WO2022239167A1

WO2022239167A1 - Method for manufacturing printed wiring board with metal reinforcement plate, member set, and printed wiring board with metal reinforcement plate

Info

Publication number: WO2022239167A1
Application number: PCT/JP2021/018129
Authority: WO
Inventors: 聡西之原; 努早坂
Original assignee: 東洋インキＳｃホールディングス株式会社; トーヨーケム株式会社
Priority date: 2021-05-12
Filing date: 2021-05-12
Publication date: 2022-11-17
Also published as: CN117280876A; KR20230163499A

Abstract

This method for manufacturing a printed wiring board with a metal reinforcement plate comprises: a step [1] in which a member set (17) is disposed on a printed wiring board (20) so that the wiring board (20) and a conductive adhesive (12) oppose each other, the member set being provided with, in the given order, a metal reinforcement plate (14), a cushion material (16), and the conductive adhesive (12) which contains a conductive filler and a binder resin that is softened by heat; a step [2] for hot-pressing the member set (17) so that a ground circuit (25) and the metal reinforcement plate (14) are adhered by the conductive adhesive (12) via an opening (27) provided to an insulating protective film (22, 23), and the ground circuit (25) and the metal reinforcement plate (14) are electrically connected; and a step [3] for peeling off the cushion material (16) of the member set (17).

Description

Method for manufacturing printed wiring board with metal reinforcing plate, member set, and printed wiring board with metal reinforcing plate

The present invention relates to a method for manufacturing a printed wiring board with a metal reinforcing plate, a member set used in the manufacturing method, and a printed wiring board with a metal reinforcing plate.

As electronic devices such as OA equipment and communication devices are becoming more sophisticated and smaller, flexible printed wiring boards (hereinafter referred to as "FPC") are becoming more and more popular in electronic devices by making use of their bendability. It is used to incorporate electronic circuits into narrow and complicated internal substrates. It is common to use an FPC with an electromagnetic wave shield layer for shielding the generated electromagnetic waves for this electronic circuit, but due to the increase in the amount of information in electronic circuits in recent years, the increase in frequency and the miniaturization of electronic circuits As a result, electromagnetic wave countermeasures are becoming more and more important.

As an FPC having an electromagnetic wave shield layer, Patent Document 1 discloses an FPC in which a conductive metal reinforcing plate and a ground circuit are connected with a conductive adhesive. Specifically, a conductive adhesive sheet is used to attach a metal reinforcing plate made of stainless steel or the like to the FPC, thereby electrically connecting the metal reinforcing plate to the ground circuit. With such a configuration, it is possible to obtain an FPC with good electromagnetic wave shielding properties, and to stably transmit circuit signals. Patent Literature 2 discloses a technique related to a conductive adhesive containing a thermosetting resin and a conductive filler.

WO2014/010524 WO2019/031394

When attaching a metal reinforcing plate to an FPC, the conductive adhesive is required to have embedding properties in the opening formed in the insulating protective film of the FPC. Specifically, when a set of members arranged in the order metal reinforcing plate/conductive adhesive/FPC is hot-pressed at a predetermined press temperature (for example, 170° C.), the softening of the conductive adhesive is insufficient. , there is a problem that the fillability of the conductive adhesive into the opening deteriorates. In particular, when the opening is small, the filling property is remarkably deteriorated, resulting in poor conduction. Therefore, it is necessary to soften the conductive adhesive at the pressing temperature (eg 170°C).
On the other hand, when the conductive adhesive oozes out from between the metal reinforcing plate and the FPC due to the press pressure in the pressing process, it causes problems such as poor appearance and short circuit.

In addition, if the conductive adhesive is softened, the conductive adhesive will exude excessively from between the metal reinforcing plate and the FPC, causing poor appearance and short circuits.

In view of the above problems, an object of the present invention is to provide a method for manufacturing a printed wiring board with a metal reinforcing plate, which has good fillability of a conductive adhesive in openings and can prevent appearance defects and short circuits, and the printed wiring board. and a printed wiring board with a metal reinforcing plate for use in the manufacturing method of the above.

As a result of extensive studies, the present inventors have found that the following aspects can solve the problems of the present invention, and have completed the present invention.
A method for manufacturing a printed wiring board with a metal reinforcing plate according to one aspect of the present invention is a printed wiring board in which a circuit pattern including a ground circuit and an insulating protective film that insulates and protects the circuit pattern and has an opening are formed. A member set in which a conductive adhesive containing a binder resin and a conductive filler softened by heat, a metal reinforcing plate, and a cushion material are arranged in this order above the printed wiring board and the conductive adhesive the step of arranging the agents so as to face each other [1];
The member set is hot-pressed to bond the ground circuit and the metal reinforcing plate with the conductive adhesive through the opening provided in the insulating protective film, and the ground circuit and the metal reinforcing plate are bonded together. and a step [2] of electrically connecting to and a step [3] of peeling off the cushion material of the member set.
Further, a member set according to an aspect of the present invention includes a printed wiring board having a circuit pattern including a ground circuit, and an insulating protective film that insulates and protects the circuit pattern and has an opening penetrating to the ground circuit. , and a metal reinforcing plate joined to the printed wiring board by hot pressing, a member set used for manufacturing a printed wiring board with a metal reinforcing plate,
It contains a binder resin that is softened by heat and a conductive filler, is filled into the opening by the heat press, electrically connects the ground circuit and the metal reinforcing plate, and connects the metal reinforcing plate to the printed wiring. A conductive adhesive to be bonded to the plate, the metal reinforcing plate, and a cushioning material that softens during the hot press and flows into the side surface of the conductive adhesive and the metal reinforcing plate are arranged in this order. .

INDUSTRIAL APPLICABILITY According to the present invention, it is used in a method for manufacturing a printed wiring board with a metal reinforcing plate, which has a good filling property of a conductive adhesive in an opening and can prevent appearance defects and short circuits, and a method for manufacturing the printed wiring board. A printed wiring board with a member set and a metal reinforcing plate can be provided.

FIG. 10 is a diagram for explaining a member set preparation step [1] according to the embodiment; FIG. 10 is a diagram for explaining a member set preparation step [2] according to the embodiment; FIG. 10 is a diagram for explaining a member set preparation step [3] according to the embodiment; FIG. 2 is a diagram for explaining a method (step [1]) for manufacturing a printed wiring board with a metal reinforcing plate according to the embodiment; FIG. 4 is a diagram for explaining the method of manufacturing a printed wiring board with a metal reinforcing plate according to the embodiment (step [2]); FIG. 4 is a diagram for explaining the method (step [3]) for manufacturing a printed wiring board with a metal reinforcing plate according to the embodiment; 1 is a cross-sectional view of a printed wiring board with a metal reinforcing plate according to an embodiment; FIG. It is a sectional view of a member set concerning an embodiment. FIG. 11 is a cross-sectional view of a member set according to another embodiment; FIG. 5 is a cross-sectional view of a printed wiring board with a metal reinforcing plate according to a comparative example, for explaining poor embedding properties of a conductive adhesive into an opening. FIG. 5 is a cross-sectional view of a printed wiring board with a metal reinforcing plate according to a comparative example, for explaining a defect in seeping of a conductive adhesive; FIG. 10 is a plan view of a printed wiring board according to a comparative example for explaining a leaking defect of a conductive adhesive; FIG. 4 is a schematic plan view of a printed wiring board with a metal reinforcing plate according to a comparative example, for explaining the bleeding failure of the conductive adhesive;

A sheet in this specification includes not only a sheet defined in JIS but also a film. For clarity of explanation, the following description and drawings have been simplified where appropriate. Unless otherwise noted, the various components appearing in this specification may be used singly or in combination of two or more. In this specification, "printed wiring board" may be abbreviated as "wiring board". Hereinafter, examples of embodiments of the present invention will be described.

<<Manufacturing method of printed wiring board with metal reinforcing plate>>
A method for manufacturing a printed wiring board with a metal reinforcing plate will be described with reference to FIGS. 1A to 2C. FIGS. 2A to 2C show a manufacturing process for attaching a metal reinforcing plate to a printed wiring board using a conductive adhesive. The details of the materials forming each member will be described later. Further, in this specification, "conductive adhesive" refers to a conductive adhesive before heat curing, and "conductive adhesive layer" refers to a layer obtained by heat curing a conductive adhesive (that is, , conductive adhesive after thermosetting), and both are given the same reference numerals.

<Component set preparation process>
First, as shown in preparation step [1] in FIG. 1A, a conductive adhesive sheet 13 having a conductive adhesive 12 formed on a peelable film 11 and a metal reinforcing plate 14 are prepared. Then, as shown in the preparation step [2] in FIG. 1B, the conductive adhesive 12 side of the conductive adhesive sheet 13 is attached to the metal reinforcing plate 14, and the conductive adhesive sheet 13 is temporarily attached to the metal reinforcing plate 14. do. The temperature at which the conductive adhesive sheet 13 is temporarily attached to the metal reinforcing plate 14 (temporary attachment temperature) can be, for example, 110.degree. C. to 150.degree. C., preferably 130.degree. After temporary attachment, the conductive adhesive 12 is in a semi-cured state.

Next, as shown in the preparation step [3] in FIG. 1C, the peelable film 11 is peeled off to expose the surface of the conductive adhesive 12 opposite to the metal reinforcing plate 14 . After that, the preliminary laminate 15 of the conductive adhesive 12 and the metal reinforcing plate 14 is cut to a predetermined size (the cutting line is indicated by reference numeral 18). The cutting of the pre-laminate 15 can be performed, for example, using a stamping process. Incidentally, the peelable film 11 may be peeled off after the cutting step.

<Step [1]>
First, a printed wiring board is prepared on which a circuit pattern including a ground circuit and an insulating protective film that insulates and protects the circuit pattern and has an opening is formed. Then, above the insulating protective film of the printed wiring board, a member set having, in this order, a conductive adhesive containing a binder resin and a conductive filler that are softened by heat, a metal reinforcing plate, and a cushioning material is mounted on the wiring. In this step, the plate and the conductive adhesive are arranged so as to face each other.

In addition, the member set of the present invention is used when (i) the layers of the conductive adhesive/metal reinforcing plate/cushion material are integrated and then used, and (ii) the respective layers are arranged in order above the printed wiring board. (iii) when a cushioning material is arranged in a preliminary laminate in which a conductive adhesive and a metal reinforcing plate are integrated; This includes the case where a preliminary laminate is arranged and used. That is, in this member set, the conductive adhesive, the metal reinforcing plate, and the cushioning material may be arranged in this order at the time of hot pressing. And the metal reinforcing plate and the cushion member may be independently non-integral or integral. Here, "integrated" means not only being stacked but also stuck (laminated), and "non-integrated" means not stuck but stacked. At the time of hot pressing, at least the member set of this agent set is integrated.

For example, as shown in FIG. 2A, a pre-laminate 15 cut into a predetermined size is placed on the wiring board 20 . Furthermore, a member set 17 is obtained by arranging a cushion material 16 on the upper surface of the metal reinforcing plate 14 . Wiring board 20 has a structure in which base material 21 on the lower side and insulating film 22 on the upper side are adhered with insulating adhesive 23 . A signal circuit 24 and a ground circuit 25 are formed on the substrate 21. Above the ground circuit 25 are an insulating film 22 and an opening (through hole) 27 provided in an insulating adhesive 23. are placed. That is, part of the ground circuit 25 formed on the base material 21 is exposed through the opening 27 . Member set 17 is arranged above opening 27 of wiring board 20 . The insulating film 22 and the insulating adhesive 23 function as an insulating protective film.

<Step [2]>
In the step [2], the member set is hot-pressed, the ground circuit and the metal reinforcing plate are bonded with a conductive adhesive through the opening provided in the insulating protective film of the printed wiring board, and the ground This is the step of electrically connecting the circuit and the metal reinforcing plate.

For example, as shown in FIG. 2B, following step [1], the laminate of member set 17/wiring board 20 is hot-pressed (heated/heated) at a predetermined temperature (for example, 150 to 190° C., preferably 170° C.). pressure). As a result, the conductive adhesive 12 is softened and embedded in the openings 27 formed in the insulating film 22 and the insulating adhesive 23 . By filling the opening 27 with the softened conductive adhesive 12 , the conductive adhesive 12 contacts the ground circuit 25 exposed through the opening 27 . After the hot pressing, the conductive adhesive 12 is cured to bond the metal reinforcing plate 14 and the wiring board 20 together, and electrically connect the ground circuit 25 and the metal reinforcing plate 14 . On the other hand, the cushioning material 16 is fluidized by heat and pressure, flows into the side surfaces of the metal reinforcing plate 14 and the conductive adhesive 12, and prevents the conductive adhesive 12 from seeping out. That is, the cushion material 16 flows to the side surface of the conductive adhesive 12 before the conductive adhesive 12 seeps out from the metal reinforcing plate during hot pressing, and prevents the seepage. In this state, the cushion material 16 requires hardness (viscoelasticity) to suppress the exudation of the conductive adhesive 12 .

The pressure during hot pressing is preferably about 3 to 30 kg/cm ² . A flat pressing machine or a roll pressing machine can be used for the hot press. The time for hot pressing is not particularly limited as long as the member set of cushion material 16/metal reinforcing plate 14/conductive adhesive 12/wiring board 20 is sufficiently adhered, but usually from 1 minute to. It takes about 1 hour. If the hot press time is short, it is preferable to heat the conductive adhesive 12 in an oven at 150 to 190° C. for 30 minutes to 3 hours after the hot press to fully cure the conductive adhesive 12 .

<Step [3]>
Step [3] is a step of peeling off the cushion material of the member set.
After the hot pressing, as shown in FIG. 2C, the cushioning material 16 whose fluidity has disappeared due to the decrease in temperature is peeled off by a suction peeling device or manually.
As a result, as shown in FIG. 3, the metal reinforcing plate 14 and the ground circuit 25 of the wiring board 20 are electrically connected via the conductive adhesive layer 12, thereby forming a printed wiring with a metal reinforcing plate having electromagnetic wave shielding properties. A plate 30 can be manufactured.

Next, the details of the materials forming each member will be described.
<Member set>
A member set according to the present embodiment is used in the above-described method for manufacturing a printed wiring board with a metal reinforcing plate, and is arranged in the order of a cushion material, a metal reinforcing plate, and a conductive adhesive. As shown in FIG. 4A, each member may have substantially the same size in plan view. In addition, as shown in FIG. 4B , a mode in which a protruding region of the cushion material on which the metal reinforcing plate and the conductive adhesive are not superimposed is provided outside the outer edge of the metal reinforcing plate and the conductive adhesive in a plan view. good too. That is, the size of the cushioning material in plan view may be larger than that of the conductive adhesive and the metal reinforcing plate, and the cushioning material may have a region that protrudes from the metal reinforcing plate or the like in plan view. With such a configuration, it is possible to more effectively prevent the conductive adhesive layer from seeping out to the side surface during hot pressing.
Further, in the member set of the present invention, from the viewpoint of preventing exudation, the storage elastic modulus of the cushion material is 10 MPa or more and 100 MPa or less at 170 ° C., and the storage elastic modulus of the conductive adhesive is 170 ° C. is 2 MPa or more and 50 MPa or less, and the storage elastic modulus of the cushion material is preferably higher than that of the conductive adhesive.

After forming the preliminary laminate 15 composed of the metal reinforcing plate 14 and the conductive adhesive 12 as described above, the member set includes the step of stacking the cushioning material, or the conductive adhesive/metal reinforcement in advance before placing on the wiring board. A member set (laminate) in which the plate/cushion material is integrated may be formed.

A member set that satisfies any one of the following conditions (I) to (III) is preferable from the viewpoint of having excellent embedding properties in openings and more effectively exuding the conductive adhesive. be.
(I) The storage modulus of the conductive adhesive at 170° C. is 5.5 MPa or more and 50 MPa or less, and the storage modulus of the cushioning material at 170° C. is 10 MPa or more and 100 MPa or less, and the storage modulus of the conductive adhesive is A component set with a higher cushioning material.
(II) The storage modulus of the conductive adhesive at 170°C is 2 MPa or more and 50 MPa or less, and the storage modulus of the cushioning material at 170°C is 10 MPa or more and 100 MPa or less, and the storage modulus is higher than that of the conductive adhesive. A member set in which the cushion material is higher in the range of 21 MPa or more and 50 MPa or less.
(III) The storage modulus of the conductive adhesive at 170° C. is 2 MPa or more and 50 MPa or less, and the storage modulus of the cushioning material at 170° C. is 10 MPa or more and 100 MPa or less, and the storage modulus is higher than that of the conductive adhesive. A member set in which the material is high and the thickness ratio between the metal reinforcing plate and the cushioning material (thickness of the metal reinforcing plate [μm]/thickness of the cushioning material [μm]) is 1.5 to 2.
Each layer will be described in detail below.

(cushion material)
The cushion material uniformly transmits the press pressure of the hot press to the metal reinforcing plate and the conductive adhesive, flows during the hot press, and has a role of suppressing the seepage of the conductive adhesive.

The storage elastic modulus of the cushioning material at 170°C is preferably 10 MPa or more and 100 MPa or less, more preferably 12 MPa or more and 90 MPa or less, and even more preferably 15 MPa or more and 70 MPa or less. By setting the content in the above range, exudation of the conductive adhesive during hot press is suppressed. When the storage elastic modulus of the cushioning material exceeds 100 MPa, as shown in FIG. 4B, the cushioning material cannot disperse the press pressure, and the conductive adhesive 12 is strongly applied to the pressure, so that it softens and tends to seep out. On the other hand, if the storage elastic modulus is less than 10 MPa, the hardness of the cushioning material is insufficient, and it becomes difficult to suppress exudation due to softening of the conductive adhesive.

The storage elastic modulus of the cushioning material according to this embodiment can be measured as follows. That is, using a dynamic viscoelasticity measuring device, the storage elastic modulus (E′), loss elastic modulus (E″), and loss tangent (tan δ) changes in the temperature range of 25 to 200 ° C. of the cushion material are measured. It can be obtained by extracting the storage elastic modulus (E′) in .

Also, the melt flow rate (MFR) of the cushioning material is preferably 0.002 g/10 min or more and 17 g/10 min or less, more preferably 0.01 g/10 min or more and 4.0 g/10 min or less. When the MFR is 0.002 g/10 min or more, before the conductive adhesive 12 softens and oozes out during hot pressing, the cushioning material reaches the side surface and effectively exhibits the effect of suppressing oozing out. . On the other hand, by setting it to 17 g/10 min or less, the embedding of the conductive adhesive 12 is improved by suppressing excessive flow and uniformly transmitting the press pressure.

The cushion material can be formed from a thermoplastic resin composition containing a thermoplastic resin. Moreover, the thermoplastic resin composition may contain a plasticizer, a thermosetting agent, an inorganic filler, etc. in addition to the thermoplastic resin.

Examples of thermoplastic resins include polyolefin resins, acid-modified polyolefin resins grafted with acid, copolymer resins of polyolefins and unsaturated esters, vinyl resins, styrene/acrylic resins, diene resins, cellulose resins, Polyamide resins, polyurethane resins, polyester resins, polycarbonate resins, polyimide resins, fluorine resins, and the like can be used. Among these, polyolefin resins, acid-modified polyolefin resins grafted with acid, copolymer resins of polyolefins and unsaturated esters, and vinyl resins are preferred. The thermoplastic resins may be used singly or as a mixture of two or more at any ratio as required.

Polyolefin-based resins are preferably homopolymers or copolymers of ethylene, propylene, α-olefin compounds, and the like. Specific examples include low-density polyethylene, ultra-low-density polyethylene, linear low-density polyethylene, high-density polyethylene, polypropylene homopolymer, polypropylene copolymer, and the like. Among these, polyethylene resin and polypropylene resin are preferred, and polyethylene resin is more preferred.

The acid-modified polyolefin resin is preferably a polyolefin resin grafted with maleic acid, acrylic acid, methacrylic acid, itaconic acid, or the like. Among these, maleic acid-modified polyolefin resins are preferred.

Examples of unsaturated esters in copolymer resins of polyolefins and unsaturated esters include methyl acrylate, ethyl acrylate, isobutyl acrylate, n-butyl acrylate, isooctyl acrylate, methyl methacrylate, isobutyl methacrylate, dimethyl maleate, diethyl maleate and glycidyl methacrylate, and the like. Among these, an ethylene-glycidyl methacrylate copolymer resin composed of ethylene as a polyolefin and glycidyl methacrylate as an unsaturated ester is preferred.

The vinyl-based resin is preferably a polymer obtained by polymerization of a vinyl ester such as vinyl acetate, or a copolymer of a vinyl ester and an olefin compound such as ethylene. Specific examples include ethylene-vinyl acetate copolymer, ethylene-vinyl propionate copolymer, partially saponified polyvinyl alcohol, and the like. Among these, ethylene-vinyl acetate copolymers are preferred.

The styrene-acrylic resin is preferably a homopolymer or copolymer composed of styrene, (meth)acrylonitrile, acrylamides, maleimides, and the like. Specific examples include syndiotactic polystyrene, polyacrylonitrile, and acrylic copolymers.

The diene-based resin is preferably a homopolymer or copolymer of a conjugated diene compound such as butadiene or isoprene, and a hydrogenated product of these homopolymers or copolymers. Specifically, styrene-butadiene rubber, styrene-isoprene block copolymer, styrene-ethylene/butylene-styrene block copolymer, styrene-ethylene/propylene-styrene block copolymer, styrene-isoprene-styrene block copolymer, styrene-butylene/butadiene- Examples include styrene block copolymers, mixtures of styrene-ethylene/butylene-styrene block copolymers and styrene-ethylene/butylene block copolymers, and the like.

Cellulose-based resin is preferably cellulose acetate butyrate resin. Polycarbonate resin is preferably bisphenol A polycarbonate.

Polyimide-based resins are preferably thermoplastic polyimides, polyamide-imide resins, and polyamic acid-type polyimide resins.

In order to facilitate the separation of the cushion material after hot pressing from the metal reinforcing plate, wiring board, and hot press machine, the cushion material may include a release layer in addition to the cushioning member. As the release layer, it is preferable to form a layer made of polypropylene, polymethylpentene, cyclic olefin polymer, silicone, or fluororesin. Among these, more preferable are polypropylene, polymethylpentene, silicone and fluororesin. In addition to the above forms, a form in which a release agent such as alkyd or silicone is coated is also preferable.

The thickness of the release layer is preferably 0.001-70 μm, more preferably 0.01-50 μm.

"CR1012", "CR1012MT4", "CR1040", "CR2031MT4", etc. manufactured by Mitsui Tocello can be used as commercially available cushioning materials. These commercially available cushioning materials have a layered structure in which both sides of the cushioning material are sandwiched between polymethylpentene as release layers, and the integral structure of these is called a cushioning material in the present application.

The thickness of the cushion material is preferably 50-300 μm, more preferably 75-250 μm, and even more preferably 100-200 μm. By setting the thickness to 50 to 300 μm, the exudation property can be improved. In addition, the said thickness is a value including a mold release layer, when it has a mold release layer.

(Metal reinforcing plate)
Metal reinforcing plates include conductive metals such as gold, silver, copper, iron and stainless steel. Among these, stainless steel is preferable in terms of strength, cost and chemical stability as a reinforcing plate.

The thickness of the metal reinforcing plate is preferably 50-500 μm, more preferably 60-400 μm, even more preferably 75-300 μm. By setting the thickness of the metal reinforcing plate to 500 μm or less, it is possible to suppress seepage due to the flow of the cushioning material and promote weight reduction and miniaturization of the printed wiring board. By setting the thickness to 50 μm or more, the strength of the metal reinforcing plate is improved and the reliability of the wiring board is improved.

The metal reinforcing plate preferably has a plated layer formed on its surface in order to suppress an increase in resistance value due to non-conductivity of the surface. The plating layer is preferably gold, silver, nickel, or phosphorous-containing nickel plating. The plating method is preferably electrolytic plating or electroless plating. The thickness of the plated layer is approximately 0.1 to 5 μm, preferably 0.2 to 4 μm. Incidentally, the thickness of the metal reinforcing plate is a value including the plated layer when it has a plated layer. From the viewpoint of cost reduction, it is preferable to avoid plating.

From the viewpoint of more effectively suppressing seepage, the thickness ratio between the metal reinforcing plate and the cushioning material (thickness of the metal reinforcing plate [μm]/thickness of the cushioning material [μm]) is preferably 2 or less. It is more preferably 1.7 or less, even more preferably 1.3 or less. The lower limit is preferably 0.1 or more, more preferably 0.5 or more.

(Conductive adhesive)
The conductive adhesive according to the present embodiment preferably contains at least a binder resin softened by heat and a conductive filler, and preferably has the following properties.

[Storage modulus]
In this embodiment, the storage elastic modulus of the conductive adhesive at 170° C. may be 2 MPa or more and 50 MPa or less, preferably 4 MPa or more and 25 MPa or less, more preferably 7 MPa or more and 15 MPa or less. By setting the storage elastic modulus of the conductive adhesive at 170 ° C. in this range, the conductive adhesive 12 is sufficiently softened during hot pressing (see step [1] in FIG. 2A to step [3] in FIG. 2C). It is possible to improve the fillability of the conductive adhesive 12 into the opening. Therefore, the formation of a gap 29b (see FIG. 5A) between the conductive adhesive 12 and the ground circuit 25 can be suppressed, and the resistance between the metal reinforcing plate 14 and the ground circuit 25 is increased. can be prevented from becoming In addition, it is possible to suppress exacerbation of exudation due to excessive softening of the conductive adhesive (see FIG. 5B).

Methods for increasing the storage elastic modulus at 170° C. to 2 MPa or more include, for example, increasing the weight-average molecular weight Mw of the binder resin, making the binder resin a skeleton having many aromatic rings to increase rigidity, and conducting fillers and inorganic fillers. In addition, when the binder resin is a thermosetting resin, methods such as increasing the cross-linking density with the curing agent in the B stage can be used.

Techniques for making the storage elastic modulus at 170° C. to 50 MPa or less include, for example, lowering the weight average molecular weight Mw of the binder resin, reducing the rigidity of the binder resin by reducing aromatic rings, adding conductive fillers, inorganic fillers, and the like. Techniques include reducing the amount of filler component added, and when the binder resin is a thermosetting resin, lowering the crosslink density with the curing agent in the B stage, which is in the semi-cured state.

In the present embodiment, by setting the storage elastic modulus of the conductive adhesive at 170° C. to the range described above, a conductive adhesive having good filling properties in openings during manufacturing of a printed wiring board with a metal reinforcing plate can be obtained. and a printed wiring board with a metal reinforcing plate.

The storage elastic modulus of the conductive adhesive according to this embodiment can be obtained by the same method as for the cushion material.

Further, the storage elastic modulus of the cushioning material is preferably higher than that of the conductive adhesive. The difference in storage elastic modulus at 170° C. between the cushion material and the conductive adhesive is preferably 4 to 100 MPa, more preferably 10 to 87 MPa. By setting the content in the above range, the effect of blocking the oozing conductive adhesive by the cushion material is further improved.

[Loss tangent]
In the present embodiment, the loss tangent (tan δ) of the conductive adhesive at 170° C. is preferably 0.05 or more and 0.4 or less, more preferably 0.15 or more and 0.35 or less, and 0.20 or more and 0.20 or more. 3 or less is more preferable. By setting the loss tangent (tan δ) of the conductive adhesive at 170° C. to this range, the fillability of the conductive adhesive 12 into the opening can be further improved.

Techniques for making the loss tangent at 170° C. 0.05 or more include, for example, lowering the weight average molecular weight Mw of the binder resin, lowering the acid value of the binder resin, lowering the glass transition temperature (Tg) of the binder resin, and and adding a curing agent that is liquid at room temperature.

Methods for making the loss tangent at 170° C. 0.40 or less include, for example, increasing the weight-average molecular weight Mw of the binder resin, increasing the acid value of the binder resin, increasing the Tg of the binder resin, and adding a solid at room temperature. For example, a curing agent is added.

The loss tangent (tan δ) of the conductive adhesive according to the present embodiment is the storage elastic modulus (E' ), loss modulus (E″), and loss tangent (tan δ), and extract the loss tangent (tan δ) at each temperature.

[Glass-transition temperature]
Further, the conductive adhesive of the present embodiment can be determined using the peak temperature in the temperature-loss tangent (tan δ) curve obtained by viscoelasticity measurement. The conductive adhesive of the present invention preferably has first and second glass transition temperatures, with the low temperature peak defined as the first glass transition temperature and the high temperature peak defined as the second glass transition temperature. Preferably, the first glass transition temperature is 10° C. or higher and 45° C. or lower, and the second glass transition temperature is 70° C. or higher and 140° C. or lower. More preferably, the first glass transition temperature is 25° C. or higher and 40° C. or lower, and the second glass transition temperature is 75° C. or higher and 110° C. or lower. More preferably, the first glass transition temperature is 27° C. or higher and 36° C. or lower, and the second glass transition temperature is 78° C. or higher and 95° C. or lower. By setting the glass transition temperature of the conductive adhesive within such a range, the adhesiveness of the conductive adhesive and the ability to fill the opening can be further improved.

Techniques for setting the first glass transition temperature to 10° C. or higher and 45° C. or lower include, for example, a method of controlling the Tg of the binder resin, and when the binder resin is a thermosetting resin, the cross-linking density with the curing agent is adjusted. There are methods of control.
In order to set the second glass transition temperature to 70° C. or higher and 140° C. or lower, the same method as described above can be used for adjustment.

[Thickness]
The thickness of the conductive adhesive is preferably 15-70 μm, more preferably 20-65 μm. By setting the thickness to 15 μm or more, it is possible to improve the embedding property in a small opening via. By setting the thickness to 70 μm or less, the bleeding property can be suppressed. The thickness of the conductive adhesive can be measured by a contact-type film thickness meter, cross-sectional observation, or the like.

[Method for producing conductive adhesive]
The conductive adhesive that constitutes the member set can be produced, for example, from a conductive adhesive sheet using a conductive resin composition and forming a conductive adhesive on a peelable film.

"Conductive resin composition"
The conductive adhesive according to the present embodiment is preferably formed from a conductive resin composition containing a binder resin softened by heat and conductive fine particles.

The binder resin softened by heat is not particularly limited as long as it does not deviate from the gist of the present invention, but thermosetting resins are preferred. Thermoplastic resins are preferred for applications in which there is no heating process such as a reflow process in the post-process. A self-crosslinking type and a curing agent reaction type can be used for the thermosetting resin. A thermosetting resin having a reactive functional group capable of reacting with a curing agent is suitable as the curing agent reaction type binder resin.

<Thermosetting resin>
A thermosetting resin is a resin having a plurality of functional groups that can be used for a cross-linking reaction by heating.
Examples of functional groups include hydroxyl groups, phenolic hydroxyl groups, carboxyl groups, amino groups, epoxy groups, oxetanyl groups, oxazoline groups, oxazine groups, aziridine groups, thiol groups, isocyanate groups, blocked isocyanate groups, silanol groups, and the like. .
Thermosetting resins having the above functional groups include, for example, acrylic resins, maleic acid resins, polybutadiene resins, polyester resins, condensation type polyester resins, addition type polyester resins, melamine resins, polyurethane resins, polyurethane urea resins, and epoxy resins. , oxetane resins, phenoxy resins, polyimide resins, polyamide resins, polyamideimide resins, phenolic resins, alkyd resins, amino resins, polylactic acid resins, oxazoline resins, benzoxazine resins, silicone resins, and fluorine resins. Among these, polyurethane resins, polyurethane urea resins, epoxy resins, addition type polyester resins, polyimide resins, polyamide resins, and polyamideimide resins are preferred.

The weight average molecular weight (Mw) of the thermosetting resin is preferably 50,000 to 200,000, more preferably 70,000 to 130,000. By setting the weight average molecular weight (Mw) within the above range, the storage elastic modulus and loss tangent at 170° C. of the conductive adhesive can be made suitable.

The glass transition temperature (Tg) of the thermosetting resin is preferably -20°C to 20°C, more preferably -7°C to 150°C. By setting the glass transition temperature within the above range, the storage elastic modulus of the conductive adhesive at 25°C can be made suitable.

The acid value of the thermosetting resin is preferably 1-40 mgKOH/g, more preferably 4-15 mgKOH/g, and even more preferably 6-13 mgKOH/g. By setting the acid value of the thermosetting resin within the above range, the cross-linking density with the curing agent described below can be optimized, and the storage elastic modulus and loss tangent at 170° C. can be made suitable.

<Hardener>
The curing agent can be arbitrarily selected according to the type of thermosetting resin. As a curing agent, it functions to make a semi-cured state when forming a conductive adhesive by a cross-linking reaction, and does not completely cure when forming a conductive adhesive sheet, and is hot-pressed to a wiring board or a metal reinforcing plate. A curing agent that cures at the time can also be appropriately selected. Curing agents include epoxy compounds, isocyanate curing agents, amine curing agents, aziridine curing agents, and imidazole curing agents.

As the epoxy compound, a glycidyl ether type epoxy compound, a glycidyl amine type epoxy compound, a glycidyl ester type epoxy compound, a cycloaliphatic (alicyclic type) epoxy compound, and the like are preferable.

Examples of the glycidyl ether type epoxy compounds include bisphenol A type epoxy compounds, bisphenol F type epoxy compounds, bisphenol S type epoxy compounds, bisphenol AD type epoxy compounds, cresol novolak type epoxy compounds, phenol novolak type epoxy compounds, α-naphthol novolak type. Epoxy compounds, bisphenol A type novolak type epoxy compounds, dicyclopentadiene type epoxy compounds, tetrabromobisphenol A type epoxy compounds, brominated phenol novolac type epoxy compounds, tris(glycidyloxyphenyl)methane, tetrakis(glycidyloxyphenyl)ethane, etc. is mentioned.

Examples of the glycidylamine-type epoxy compounds include tetraglycidyldiaminodiphenylmethane, triglycidyl para-aminophenol, triglycidylmethaminophenol, tetraglycidylmethaxylylenediamine, and the like.

Examples of the glycidyl ester type epoxy compound include diglycidyl phthalate, diglycidyl hexahydrophthalate, and diglycidyl tetrahydrophthalate.

Examples of the cycloaliphatic (alicyclic) epoxy compounds include epoxycyclohexylmethyl-epoxycyclohexanecarboxylate and bis(epoxycyclohexyl)adipate.

Isocyanate-based curing agents include tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, dicyclohexylmethane diisocyanate, 1,5-naphthalene diisocyanate, tetramethylxylylene diisocyanate, trimethylhexamethylene diisocyanate, and the like. be done.

Amine-based curing agents include diethylenetriamine, triethylenetetramine, methylenebis(2-chloroaniline), methylenebis(2-methyl-6-methylaniline), 1,5-naphthalenediisocyanate, n-butylbenzylphthalic acid, and the like.

Aziridine curing agents include trimethylolpropane-tri-β-aziridinylpropionate, tetramethylolmethane-tri-β-aziridinylpropionate, N,N'-diphenylmethane-4,4'-bis( 1-aziridinecarboxamide), N,N'-hexamethylene-1,6-bis(1-aziridinecarboxamide) and the like.

Examples of imidazole curing agents include 2-methylimidazole, 2-heptadecylimidazole, 2-phenyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazolium trimellitate and the like.

The curing agent is preferably blended in an amount of 0.3 to 80 parts by weight, more preferably 1 to 50 parts by weight, per 100 parts by weight of the thermosetting resin. By adding the curing agent in an amount of 0.3 to 80 parts by weight, the crosslink density of the conductive adhesive can be optimized, and the storage elastic modulus at 170° C. can be in the range of 2 MPa or more and 50 MPa or less. Also, by adding the curing agent in an amount of 0.3 to 80 parts by weight, the conductive adhesive sheet is less likely to flow after semi-curing, so that blocking is easily suppressed.

<Thermoplastic resin>
In this embodiment, a thermoplastic resin may be used together. Examples of thermoplastic resins include polyolefin resins, vinyl resins, styrene/acrylic resins, diene resins, terpene resins, petroleum resins, cellulose resins, polyamide resins, polyurethane resins, and polyester resins that do not have the curable functional group. , polycarbonate resins, polyimide resins, fluorine resins, and the like.

Polyolefin-based resins are preferably homopolymers or copolymers of ethylene, propylene, α-olefin compounds, and the like. Specific examples include polyethylene propylene rubber, olefinic thermoplastic elastomer, α-olefin polymer, and the like.

The vinyl-based resin is preferably a polymer obtained by polymerization of a vinyl ester such as vinyl acetate, or a copolymer of a vinyl ester and an olefin compound such as ethylene. Specific examples include ethylene-vinyl acetate copolymer, partially saponified polyvinyl alcohol, and the like.

The styrene-acrylic resin is preferably a homopolymer or copolymer of styrene, (meth)acrylonitrile, acrylamides, (meth)acrylic acid esters, maleimides and the like. Specific examples include syndiotactic polystyrene, polyacrylonitrile, acrylic copolymers, ethylene-methyl methacrylate copolymers, and the like.
The diene resin is preferably a homopolymer or copolymer of a conjugated diene compound such as butadiene or isoprene, and hydrogenated products thereof. Specific examples include styrene-butadiene rubber and styrene-isoprene block copolymers. The terpene resin is preferably a polymer composed of terpenes or a hydrogenated product thereof. Specific examples include aromatic modified terpene resins, terpene phenol resins, and hydrogenated terpene resins.

The petroleum-based resin is preferably a dicyclopentadiene-type petroleum resin or a hydrogenated petroleum resin. Cellulose-based resin is preferably cellulose acetate butyrate resin. Polycarbonate resin is preferably bisphenol A polycarbonate. The polyimide resin is preferably thermoplastic polyimide, polyamideimide resin, or polyamic acid type polyimide resin.

<Conductive fine particles>
The conductive fine particles are preferably fine particles of conductive metals such as gold, platinum, silver, copper and nickel, alloys thereof, and conductive polymers. From the viewpoint of cost reduction, it is preferable to use composite fine particles in which metal or resin is used instead of fine particles of a single composition, and the coating layer that coats the surface of the core is formed of a material having higher conductivity than the core.
It is preferable to appropriately select the core material from inexpensive nickel, silica, copper and their alloys, and resin.
The coating layer may be made of any conductive material, preferably a conductive metal or a conductive polymer. Conductive metals include gold, platinum, silver, tin, manganese, indium, and the like, and alloys thereof. Examples of conductive polymers include polyaniline and polyacetylene. Among these, silver is preferable from the aspect of conductivity.
The conductive fine particles may be used alone or in combination of two or more.

The fine composite particles preferably have a coating layer in a proportion of 1 to 40 parts by weight, more preferably 5 to 30 parts by weight, per 100 parts by weight of the core. Coating with 1 to 40 parts by weight can further reduce costs while maintaining electrical conductivity. In addition, it is preferable that the coating layer of the fine composite particles completely covers the nucleus. However, in reality, part of the nuclear body may be exposed. Even in such a case, if 70% or more of the surface area of the core is covered with the conductive fine particles, the conductivity can be easily maintained.

The shape of the conductive fine particles is not limited as long as the desired conductivity is obtained. For example, spherical, flake-like, leaf-like, dendritic, plate-like, needle-like, rod-like and grape-like are preferred. A spherical shape and a dendritic shape are more preferable in order to efficiently form a vertical conducting path between the metal reinforcing plate and the wiring board.

As for the average particle size of the conductive fine particles, the _D50 average particle size is preferably 1 to 120 μm, more preferably 5 to 60 μm. When the _D50 average particle size is within this range, blocking can be suppressed. The _D50 average particle size can be determined by a laser diffraction/scattering method particle size distribution analyzer. For example, a conductive adhesive sheet having a conductive adhesive on a peelable film is rolled up and transported. Blocking is a phenomenon in which the conductive adhesive sheet adheres to the back surface of the peelable film when the conductive adhesive sheet is unwound from the rolled conductive adhesive sheet.

The amount of conductive fine particles added is preferably 30 to 90% by weight, more preferably 40 to 80% by weight, based on 100% by weight of the conductive adhesive. Each storage elastic modulus at 170° C. can be set within a suitable range by adjusting the amount to be added as described above.

The conductive resin composition in the present embodiment contains other optional components such as a solvent, a heat stabilizer, an inorganic filler, a pigment, a dye, a tackifying resin, a plasticizer, a silane coupling agent, an ultraviolet absorber, an antifoaming agent, A leveling adjuster or the like can be blended.

Examples of inorganic fillers include silica, alumina, aluminum hydroxide, magnesium hydroxide, barium sulfate, calcium carbonate, titanium oxide, zinc oxide, antimony trioxide, magnesium oxide, talc, montmorolinite, kaolin, and bentonite. be done. By containing an inorganic filler in the conductive adhesive layer, it is possible to control the storage elastic modulus before curing and control the amount of flow to be optimal.

The conductive resin composition can be obtained by mixing and stirring the above components. For stirring, a known stirring device can be used, and Dispermat is generally used, but a homogenizer is also preferable.

The conductive resin composition is applied to the release surface of the release film by methods such as knife coating, die coating, lip coating, roll coating, curtain coating, bar coating, gravure coating, flexo coating, dip coating, spray coating, and spin coating. and heated to a temperature of usually 40 to 20° C. to remove volatile components such as solvents, thereby forming a conductive adhesive sheet having a conductive adhesive layer.

"Peelable film"
As the peelable film, any film having one side or both sides subjected to release treatment can be used without limitation.
Examples of base materials for peelable films include polyethylene terephthalate, polyethylene naphthalate, polyvinyl fluoride, polyvinylidene fluoride, rigid polyvinyl chloride, polyvinylidene chloride, nylon, polyimide, polystyrene, polyvinyl alcohol, and ethylene/vinyl alcohol copolymer. Coalescing, polycarbonate, polyacrylonitrile, polybutene, soft polyvinyl chloride, polyvinylidene fluoride, polyethylene, polypropylene, polyurethane, ethylene vinyl acetate copolymer, plastic sheets such as polyvinyl acetate, glassine paper, fine paper, kraft paper, coated Examples include papers such as paper, various non-woven fabrics, synthetic papers, metal foils, and composite films in which these are combined.

The surface of the peelable film can be matte treated as needed. Examples of matting include sand matting, etching matting, coating matting, chemical matting, and kneading matting.

The peelable film can be obtained by applying a release agent to the substrate. Release agents include hydrocarbon resins such as polyethylene and polypropylene, higher fatty acids and their metal salts, higher fatty acid soaps, waxes, animal and vegetable oils, mica, talc, silicone surfactants, silicone oils, silicone resins, fluorine-based Surfactants, fluorine resins, fluorine-containing silicone resins, melamine resins, acrylic resins, and the like are used. Examples of the method of applying the release agent include conventionally known methods, gravure coating, kiss coating, die coating, lip coating, comma coating, blade coating, roll coating, knife coating, spray coating, and bar coating. method, spin coating method, dip coating method, or the like.

<Printed wiring board>
A printed wiring board is provided with a circuit pattern including a ground circuit and an insulating protective film that insulates and protects the circuit pattern and has an opening on a substrate. Circuit patterns including ground circuits are generally formed by etching copper. The insulating protective film is preferably formed of a polyimide coverlay comprising a polyimide film and an insulating adhesive, a resist film, or a solder resist. Drilling, etching, and laser processing are preferred methods for forming an opening on the ground circuit. The area, shape, etc. of the opening will be described later.

《Printed wiring board with metal reinforcing plate》
A printed wiring board 30 with a metal reinforcing plate according to the present embodiment (see FIG. 3) has a circuit pattern including a ground circuit 25 arranged on a base material 21, and an insulating protective film (insulating layer) for insulating and protecting the upper layer thereof. It has a wiring board 20 on which an insulating film 22 and an insulating adhesive 23) are formed. A ground circuit 25 exposed through an opening 27 provided in the insulating protective film, and a conductive adhesive layer 12 arranged on the wiring board 20 and formed using the conductive adhesive described above. and a metal reinforcing plate 14 disposed on the conductive adhesive layer 12 and bonded to the wiring board 20 via the conductive adhesive layer 12 . In printed wiring board 30 with a metal reinforcing plate according to the present embodiment, opening 27 is partially filled with conductive adhesive layer 12, so that ground circuit 25 and metal reinforcing plate 14 are bonded with the conductive adhesive. They are electrically connected through layer 12 . A signal circuit 24 may be further provided on the wiring board 20 .

The area of opening 27 (see FIG. 3) of printed wiring board 30 with a metal reinforcing plate is not particularly limited, but may be 0.16 mm ² or more and 0.81 mm ² or less. By setting the area of the opening 27 to 0.16 mm ² or more, the filling property of the conductive adhesive 12 into the opening 27 can be improved. Further, by setting the area of opening 27 to 0.81 mm ² or less, the area of opening 27 occupying printed wiring board 30 with a metal reinforcing plate can be reduced. The area of the opening 27 may be preferably 0.25 mm ² or more and 0.64 mm ² or less, more preferably 0.36 mm ² or more and 0.49 mm ² or less. When the area of the opening 27 is within this range, the filling of the opening 27 with the conductive adhesive 12 can be improved, and the contact resistance between the conductive adhesive 12 and the ground circuit 25 can be reduced. can be done.
According to the method for manufacturing a printed wiring board with a metal reinforcing plate of the present invention, even when the area of the opening is small, the conductive adhesive can be sufficiently filled, and the printed wiring board with the metal reinforcing plate has good embedding properties. can be

The shape of the opening 27 when viewed from above may be square (see opening 27b in FIG. 6A) or circular (see opening 27a in FIG. 6A). When the shape of the opening 27 is square, it is particularly difficult to fill the four corners of the square opening with the conductive adhesive, and gaps 29b as shown in FIG. 5A are likely to be formed at the four corners. However, by using the conductive adhesive according to the present embodiment, it is possible to satisfactorily fill the opening with the conductive adhesive even if the opening is square.

6A, the opening 27c is formed in a part (side wall) of the outer circumference of the wiring board 20 (in the example shown in FIG. 6A, the opening is formed at the corner of the wiring board 20) The portion 27c is formed) is in a state in which no wall is provided outside the opening 27c to block the flow of the conductive adhesive. In this case, as shown in FIG. 6B, when the metal reinforcing plate 14 is adhered to the wiring board 20 using the conductive adhesive 12, the conductive adhesive 12a exudes toward the outside of the opening 27c. There was a problem of hoarding.

On the other hand, in the present embodiment, wiring board 20 and metal reinforcing plate 14 are bonded by using a member set consisting of cushioning material/metal reinforcing plate/conductive adhesive having the above-described characteristics during hot pressing. In this case, it is possible to prevent the conductive adhesive from seeping out from the end opening 27c (or to reduce the amount of seepage).

Such a printed wiring board with a metal reinforcing plate can be mounted, for example, in electronic devices such as mobile phones, smartphones, notebook PCs, digital cameras, and liquid crystal displays. It can also be suitably mounted on transportation equipment such as automobiles, trains, ships, and aircraft.

<Modification>
The member set according to the present embodiment may be used to join a metal reinforcing plate collectively or separately to a large-sized mother board on which a plurality of printed wiring boards are formed in an array. For example, for a large-sized mother board in which a printed wiring board is formed in each section of m rows x n columns (m and n are each independently an integer of 1 or more, at least one of which is 2 or more), conductive A pre-laminate consisting of an adhesive and a metal plate is arranged, and a large-sized cushioning material is arranged on the upper layer to obtain a member set consisting of the conductive adhesive/metal plate/cushioning material, which is then hot-pressed together. A mother board having a plurality of printed wiring boards with metal reinforcing plates may be manufactured. Also, in place of the large-sized cushioning material, a cushioning material corresponding to each printed wiring board may be arranged, or a plurality of cushioning materials may be arranged over a plurality of printed wiring boards, and the same process may be performed. A mother substrate having a plurality of printed wiring boards with metal reinforcing plates may be manufactured collectively or/and dividedly.

An arbitrary layer such as a metal foil may be provided between the conductive adhesive and the metal reinforcing plate. Also, a protective film may be formed at an arbitrary position on the metal reinforcing plate. Furthermore, in the above embodiment, an example of applying this member set to a printed wiring board has been described, but it can be suitably used for any adherend.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited only to the following examples. In addition, "parts" in the examples means parts by weight, and "%" means % by weight.
In addition, the compounding amount in the table is in parts by weight, and values other than the solvent are in terms of non-volatile matter. A blank column in the table indicates that it was not blended.

[Weight average molecular weight (Mw)]
The weight average molecular weight (Mw) is a polystyrene-equivalent numerical value obtained by GPC (gel permeation chromatography) measurement. Measurement conditions are as follows.
Apparatus: Shodex GPC System-21 (manufactured by Showa Denko)
Column: A connection column in which one Shodex KF-802 (manufactured by Showa Denko), one Shodex KF-803L (manufactured by Showa Denko), and one Shodex KF-805L (manufactured by Showa Denko) are connected in series. Solvent: Tetrahydrofuran Flow rate: 1.0 mL/min
Temperature: 40°C
Sample concentration: 0.2%
Sample injection volume: 100 μL
[Acid value]
Based on the potentiometric titration method of JIS K 0070, it calculated|required by converting the measured acid value (mgKOH/g) into solid content.
[Glass transition temperature (Tg)]
The glass transition temperature of the thermosetting resin was measured using a differential scanning calorimeter (model number: DSC-1, manufactured by Mettler Toledo).
[Storage elastic modulus], [first and second glass transition temperatures] and [loss tangent tan δ]
Using a dynamic elastic modulus measuring device (model number: DVA-200, manufactured by IT Keisoku & Co., Ltd.), the conductive adhesive peeled from the peelable film of the conductive adhesive sheet prepared by the method described later was subjected to deformation mode "Tensile", frequency 10 Hz, heating rate 10 ° C./min, measurement temperature range -50 to 300 ° C. Storage elastic modulus E' at 170 ° C. The first peak temperature of loss tangent tan δ (first glass transition temperature ), the second peak temperature (second glass transition temperature), and the loss tangent tan δ at 170°C were measured. The cushioning material was obtained by the same method.
[Melt flow rate (MFR)]
Using a melt indexer (model EB01, manufactured by Toyo Seiki Co., Ltd.), the MFR of each cushion material was measured according to JIS K7210. The measurement temperature was 230° C. and the load was 10 kg. The cushioning material formed by superimposing layers of different materials was kneaded in advance with two rolls at 190° C., and the MFR was measured after kneading and homogenizing the layered state of the layers of different materials.

<Conductive resin composition, cushion material, and metal reinforcing plate>
Each member set used in Examples and Comparative Examples, each material of the conductive resin composition, the cushion material, and the metal reinforcing plate used in the production of the printed wiring board with the metal reinforcing plate are shown below. Table 1 shows the Mw, acid value and Tg of the binder resin.

[Binder resin]
Binder resin (a-1 to 6): Polyurethane resin (manufactured by Toyochem)

[Conductive fine particles (conductive filler)]
b-1: silver-coated copper particles, _D50 average particle size = 12 μm, nucleus: dendritic (manufactured by Fukuda Metal)
[Curing agent]
c-1: bisphenol A type epoxy resin: epoxy equivalent 189 g/eq (jER1001, manufactured by Mitsubishi Chemical)
[Curing accelerator]
d-1: aziridine compound (trimethylolpropane tris [β-(N-aziridinyl) propionate], manufactured by Nippon Shokubai)
[Other ingredients]
e-1: Silica (AEROSIL R974, manufactured by Nippon Aerosil)
[solvent]
f-1: mixed solvent of toluene: isopropyl alcohol (mass ratio = 2: 1) [cushion material]
g-1: polyethylene terephthalate (thickness 25 μm, 170° C. storage modulus 470 MPa, MFR measurement not possible)
g-2: polybutylene terephthalate (thickness 50 μm, 170° C. storage modulus 89 MPa, MFR 17 g/10 min)
g-3: Polymethylpentene (thickness 50 μm, 170° C. storage modulus 62 MPa, MFR 0.002 g/10 min)
g-4: Cushion material consisting of three layers of polymethylpentene/styrene-ethylene-butylene-styrene block copolymer/polymethylpentene (thickness: 25 μm/70 μm/25 μm, 170° C. storage modulus: 32 MPa, MFR: 0.06 g/10 min)
g-5: Cushion material consisting of three layers of polymethylpentene/styrene-butadiene-styrene block copolymer/polymethylpentene (thickness: 25 μm/100 μm/25 μm, 170° C. storage modulus: 51 MPa, MFR: 0.2 g/10 min)
g-6: Cushion material consisting of three layers of polymethylpentene/ethylene-glycidyl methacrylate copolymer/polymethylpentene (thickness: 25 μm/100 μm/25 μm, 170° C. storage modulus: 23 MPa, MFR: 0.2 g/10 min)
g-7: soft vinyl chloride (thickness 75 μm, 170° C. storage elastic modulus 1 MPa, MFR 66 g/10 min)
[Metal reinforcing plate]
h-1: SUS304 with a total thickness of 200 μm with nickel layers of 2 μm thickness formed on both surfaces
h-2: SUS304 with a total thickness of 150 μm with a nickel layer of 2 μm thickness formed on both surfaces
h-3: SUS304 with a total thickness of 100 μm with nickel layers of 2 μm thickness formed on both surfaces
h-4: SUS304 with a total thickness of 75 μm with a nickel layer of 2 μm thickness formed on both surfaces
[Printed wiring board]
Printed Wiring Board 1: The printed wiring board 1 is formed of a 32 μm thick copper foil circuit on both sides of a 75 μm thick polyimide film. On the copper foil circuit, a 37.5 μm-thick insulating cover film with an adhesive and having a square through hole (opening) with a side of 0.7 mm and an opening area of 0.49 mm ² was formed. there is On the other copper foil circuit, an insulating cover film with a thickness of 37.5 μm with adhesive and without through holes was formed (so as not to warp the printed wiring board, polyimide The copper foil circuit and cover film were placed symmetrically with respect to the film).
Printed wiring board 2: A printed wiring board having the same configuration as printed wiring board 1 except that it is a square with a side of 0.4 mm and the opening area of the through hole (opening) is 0.16 mm ² .
Printed wiring board 3: A printed wiring board having the same configuration as printed wiring board 1 except that it is a square with a side of 0.2 mm and the opening area of the through hole (opening) is 0.04 mm ² .

[Example 1]
100 parts by weight of the binder resin (a-1) and 250 parts by weight of the conductive fine particles (b-1) were charged in a container, and the solvent (f-1) was added and mixed so that the concentration of the non-volatile matter was 40% by weight. . Next, 40 parts by weight of the curing agent (c-1) and 0.05 parts by weight of the curing accelerator (d-1) were added and stirred for 10 minutes with a stirrer to prepare a conductive resin composition.
Next, using a doctor blade, the conductive resin composition prepared above is applied to a release film (substrate material: foamed polyethylene terephthalate, substrate thickness 50 μm, release film) so that the thickness after drying is 60 μm. Molding agent: alkyd-based release agent) was coated on the release-treated side and dried in an electric oven at 100°C for 2 minutes to obtain a conductive adhesive sheet on which a conductive adhesive was formed. .

Next, the conductive adhesive sheet is cut to a width of 20 mm and a length of 20 mm, and the conductive adhesive sheet is cut so that the exposed surface of the conductive adhesive is in contact with the metal reinforcing plate (h-1) having a width of 20 mm and a length of 20 mm. A flexible adhesive sheet was placed on the metal reinforcing plate. Then, using a roll laminator, the conductive adhesive sheet and the metal reinforcing plate were roll-laminated under the conditions of 90° C., 3 kgf/cm ² and 1 m/min to obtain a SUS plate with the conductive adhesive sheet.

Next, after peeling off and removing the peelable film of the conductive adhesive sheet in the metal reinforcing plate with conductive adhesive sheet, a square with a side of 10 mm is punched with a punching machine, and the metal reinforcing plate with conductive adhesive ( hereinafter referred to as "metal reinforcing plate with conductive adhesive"). Next, using printed wiring boards 1 to 3 separately prepared, the surface where the conductive adhesive of the metal reinforcing plate with conductive adhesive is exposed (the surface opposite to the metal reinforcing plate of the conductive adhesive) is attached to the printed wiring board. The metal reinforcing plate with the conductive adhesive and the printed wiring board were laminated under the conditions of 130° C., 3 kgf/cm ² and 1 m/min using a roll laminator. After that, a member set was obtained in which a cushion material (g-2) cut into a square with a side of 20 mm was superimposed on the metal reinforcing plate. Next, after hot pressing these under the conditions of 170 ° C., 2 MPa, 5 minutes, the cushioning material is removed, and the printed wiring boards 1 to 1 with metal reinforcing plates are heated using an electric oven at 160 ° C. for 60 minutes. got 3.

[Examples 2 to 23]
The same operation as in Example 1 was performed except that the types and amounts of each component to be blended were as described in Tables 2 to 4, and member sets and printed wiring boards with metal reinforcing plates of Examples 2 to 23 were obtained. rice field.

[Comparative Example 1]
A member set and a printed wiring board with a metal reinforcing plate were obtained using printed wiring boards 1 to 3 in the same manner as in Example 19, except that no cushion material was used during hot pressing.

Tables 2 to 4 show the 170° C. storage elastic modulus (MPa) of the cushion material of each example−170° C. storage elastic modulus (MPa) of the conductive adhesive (characteristic values "(1)-(4)" in the table). ), and the value of thickness (μm) of metal reinforcing plate/thickness (μm) of cushion material (characteristic value “(3)/(2)” in the table).

<Evaluation>
Embedability and seepage appearance of each of the obtained printed wiring boards with metal reinforcing plates were evaluated according to the following methods. The evaluation results are shown in Tables 2-4.

[Embedability]
For printed wiring boards 1 to 3 with metal reinforcing plates having different opening areas, a resistance value measuring instrument and a BSP probe (model number: MCP-TP05P, manufactured by Mitsubishi Chemical Analytic Tech) were used to measure the SUS plate of the printed wiring boards with metal reinforcing plates. The electrical resistance (connection resistance value) between and the copper foil circuit was measured, and using this measured value as an index, the embeddability was evaluated according to the following evaluation criteria.
+++: Connection resistance value is less than 20 mΩ/□, very good.
++: The connection resistance value is 20 mΩ/□ or more and less than 100 mΩ/□, good.
+: Connection resistance value of 100 mΩ/square or more and less than 300 mΩ/square, practicable.
NG: Connection resistance value of 300 mΩ/□ or more, impractical.

[Exudation]
Regarding the printed wiring board 1 with a metal reinforcing plate, the flow amount of the conductive adhesive protruding from the edge of the metal reinforcing plate using a magnifying glass with a magnification of 200 times to 1000 times (maximum movement of the edge of the conductive adhesive layer The distance, the maximum length between the end of the SUS plate and the end of the protruding conductive adhesive layer) was measured, and the measured value was used as an index to evaluate the appearance according to the following evaluation criteria.
+++: Very good flow amount of 100 μm or less.
++: The flow amount is more than 100 μm and 130 μm or less, good.
+: The flow amount is more than 130 μm and 150 μm or less, practically possible.
NG: The amount of flow exceeds 150 µm, which is not practical.

Although the present invention has been described with reference to the above embodiments, the present invention is not limited to the configurations of the above embodiments. It goes without saying that various modifications, modifications, and combinations that can be made are included.

This specification also discloses the invention of the following technical ideas understood from the above embodiments.
(Appendix 1)
Above a printed wiring board on which a circuit pattern including a ground circuit and an insulating protective film having an opening for insulating and protecting the circuit pattern are formed,
A conductive adhesive containing a binder resin that softens by heat and a conductive filler, a metal reinforcing plate having a thickness of 50 to 500 μm, and a cushioning material having a storage elastic modulus at 170° C. higher than that of the conductive adhesive. A set of members arranged in order,
the step of arranging the printed wiring board and the conductive adhesive so as to face each other [1];
The member set is hot-pressed at 150 to 190° C., the ground circuit and the metal reinforcing plate are electrically connected through the opening, and the ground circuit and the metal reinforcing plate are connected by the conductive adhesive. and the cushion material flows into the side surface of the conductive adhesive and the metal reinforcing plate to block the leakage of the conductive adhesive to the outside from the metal reinforcing plate [2]; and a step of peeling off the cushioning material [3];
with
A method for producing a printed wiring board with a metal reinforcing plate, wherein, in the step [1], any one of the steps [1-1] to [1-3] is satisfied.
Step [1-1]: The conductive adhesive has a storage modulus of 5.5 MPa or more and 50 MPa or less at 170°C, and the cushion material has a storage modulus of 10 MPa or more and 100 MPa or less at 170°C.
Step [1-2]: The conductive adhesive has a storage modulus of 2 MPa or more and 50 MPa or less at 170°C, the cushion material has a storage modulus of 10 MPa or more and 100 MPa or less at 170°C, and The storage elastic modulus of the cushioning material is higher than that of the conductive adhesive within a range of 21 MPa or more and 50 MPa or less.
Step [1-3]: The storage elastic modulus of the conductive adhesive at 170° C. is 2 MPa or more and 50 MPa or less, the elastic modulus of the cushion member at 170° C. is 10 MPa or more and 100 MPa or less, and The thickness [μm]/thickness [μm] of the cushion material is 1.5-2.
(Appendix 2)
The printed wiring with a metal reinforcing plate according to Appendix 1, wherein in step [1-1] or step [1-3], a difference in storage elastic modulus at 170° C. between the cushion material and the conductive adhesive is 10 to 87 MPa. Board manufacturing method.
(Appendix 3)
In step [1-1] or step [1-2], the thickness ratio between the metal reinforcing plate and the cushioning material (thickness of metal reinforcing plate [μm]/thickness of cushioning material [μm]) is 2 or less. A method for manufacturing a printed wiring board with a metal reinforcing plate according to Appendix 1 or 2.
(Appendix 4)
In any one of steps [1-1] to [1-3],
The conductive adhesive having a loss tangent (tan δ) at 170 ° C. of 0.05 or more and 0.4 or less,
A method for producing a printed wiring board with a metal reinforcing plate according to any one of Appendices 1 to 3.
(Appendix 5)
In any one of steps [1-1] to [1-3],
In the temperature-loss tangent (tan δ) curve obtained by viscoelasticity measurement,
The first glass transition temperature is 10° C. or higher and 45° C. or lower,
the second glass transition temperature is 70° C. or higher and 140° C. or lower;
Characterized by using the conductive adhesive,
A method for producing a printed wiring board with a metal reinforcing plate according to any one of Appendices 1 to 4.
(Appendix 6)
In any one of steps [1-1] to [1-3],
characterized by using the cushioning material that is larger than the metal reinforcing plate and the conductive adhesive when viewed in plan,
A method for manufacturing a printed wiring board with a metal reinforcing plate according to any one of Appendices 1 to 5.
(Appendix 7)
In any one of steps [1-1] to [1-3],
Characterized by using the conductive adhesive having a thickness of 15 to 70 μm,
A method for manufacturing a printed wiring board with a metal reinforcing plate according to any one of Appendices 1 to 6.
(Appendix 8)
In any one of steps [1-1] to [1-3],
placing the conductive adhesive on the printed wiring board;
placing the metal reinforcing plate on the conductive adhesive;
8. The method for manufacturing a printed wiring board with a metal reinforcing plate according to any one of Appendices 1 to 7, wherein the cushioning material is arranged on the metal reinforcing plate.
(Appendix 9)
In any one of steps [1-1] to [1-3],
obtaining in advance a preliminary laminate of the conductive adhesive and the metal reinforcing plate;
The printed wiring board and the conductive adhesive in the preliminary laminate are arranged to face each other, and the metal reinforcing plate and the cushioning material in the preliminary laminate are arranged to face each other. 8. A method for producing a printed wiring board with a metal reinforcing plate according to any one of 1 to 7.
(Appendix 10)
In any one of steps [1-1] to [1-3],
A laminate obtained by laminating the conductive adhesive, the metal reinforcing plate, and the cushion material in this order is obtained in advance, and the printed wiring board and the conductive adhesive in the laminate face each other. A method for producing a printed wiring board with a metal reinforcing plate according to any one of Appendices 1 to 7, wherein the printed wiring board is arranged so as to be.
(Appendix 11)
A printed wiring board with a metal reinforcing plate obtained by the manufacturing method according to any one of Appendices 1 to 10.
(Appendix 12)
12. The printed wiring board with a metal reinforcing plate according to Appendix 11, wherein the opening has an area of 0.16 mm ² or more and 0.81 mm ² or less when viewed from above.
(Appendix 13)
13. The printed wiring board with a metal reinforcing plate according to

Appendix

11 or 12, wherein the opening is formed in a part of the outer periphery of the printed wiring board.

11 peelable film 12 conductive adhesive (conductive adhesive layer)
13 Conductive adhesive sheet 14 Metal reinforcing plate 15 Preliminary laminate 16 Cushion material 17 Member set 18 Cutting line 20 Wiring board 21 Base material 22 Insulating film 23 Insulating adhesive 24 Signal circuit 25 Ground circuit 27 Opening 29b Gap 30 Metal Printed wiring board with stiffener

Claims

Above a printed wiring board on which a circuit pattern including a ground circuit and an insulating protective film having an opening for insulating and protecting the circuit pattern are formed,
A member set in which a conductive adhesive containing a binder resin that softens with heat and a conductive filler, a metal reinforcing plate, and a cushioning material are arranged in this order,
a step of arranging the printed wiring board and the conductive adhesive so as to face each other [1];
The member set is hot-pressed to bond the ground circuit and the metal reinforcing plate with the conductive adhesive through the opening provided in the insulating protective film, and the ground circuit and the metal reinforcing plate are bonded together. a step [2] of electrically connecting to and a step [3] of peeling off the cushion material of the member set;
A method for manufacturing a printed wiring board with a metal reinforcing plate.
A printed wiring board having a circuit pattern including a ground circuit, an insulating protective film that insulates and protects the circuit pattern and has an opening penetrating to the ground circuit, and a metal bonded to the printed wiring board by hot pressing. A member set used for manufacturing a printed wiring board with a metal reinforcing plate, comprising a reinforcing plate,
It contains a binder resin that is softened by heat and a conductive filler, is filled into the opening by the heat press, electrically connects the ground circuit and the metal reinforcing plate, and connects the metal reinforcing plate to the printed wiring. a conductive adhesive that bonds to the plate;
the metal reinforcing plate;
A member set in which the conductive adhesive and a cushion material that softens during the hot press and flows into the side surface of the metal reinforcing plate are arranged in this order.
In order to prevent the conductive adhesive from seeping out to the side surface side during the hot press, the metal reinforcing plate and the conductive adhesive are placed outside the outer edges of the metal reinforcing plate and the conductive adhesive in a plan view. 3. The member set according to claim 2, wherein there is a projecting region of said cushioning material on which adhesive is not superimposed.
The storage elastic modulus of the cushion material is
10 MPa or more and 100 MPa or less at 170 ° C.,
The storage modulus of the conductive adhesive is
2 MPa or more and 50 MPa or less at 170 ° C.,
4. The member set according to claim 2, wherein the storage elastic modulus of the cushion material is higher than the storage elastic modulus of the conductive adhesive.
The member set according to any one of claims 2 to 4, wherein the melt flow rate (MFR) of the cushion material under a load of 10 kg at 230°C is 0.001 g/10 min or more and 17 g/10 min or less.
The loss tangent (tan δ) of the conductive adhesive is
0.05 or more and 0.4 or less at 170 ° C.
The member set according to any one of claims 2-5.
The conductive adhesive is
In the temperature-loss tangent (tan δ) curve obtained by viscoelasticity measurement,
The first glass transition temperature is 10° C. or higher and 45° C. or lower,
the second glass transition temperature is 70° C. or higher and 140° C. or lower;
The member set according to any one of claims 2-6.
The member set according to any one of claims 2 to 7, which satisfies any one of the following conditions (I) to (III).
(I) The storage modulus of the conductive adhesive at 170° C. is 5.5 MPa or more and 50 MPa or less, and the storage modulus of the cushion material at 170° C. is 10 MPa or more and 100 MPa or less, and the storage modulus is the above The cushioning material is higher than the conductive adhesive.
(II) The storage modulus of the conductive adhesive at 170° C. is 2 MPa or more and 50 MPa or less, and the storage modulus of the cushion material at 170° C. is 10 MPa or more and 100 MPa or less, and the storage modulus is the conductive The cushioning material is higher than the adhesive in the range of 21 MPa to 50 MPa.
(III) The storage modulus of the conductive adhesive at 170° C. is 2 MPa or more and 50 MPa or less, and the storage modulus of the cushion material at 170° C. is 10 MPa or more and 100 MPa or less, and the storage modulus is the conductive adhesive. The thickness of the cushioning material is higher than that of the agent, and the thickness ratio of the metal reinforcing plate to the cushioning material (thickness of metal reinforcing plate [μm]/thickness of cushioning material [μm]) is 1.5 to 2.
The member set according to any one of claims 2 to 8, wherein the metal reinforcing plate has a thickness of 50 to 500 µm.
Obtained by the production method according to claim 1,
A printed wiring board with a metal reinforcing plate, wherein the opening has an area of 0.16 mm 2 or more and 0.81 mm 2 or less when viewed from above.
11. The printed wiring board with a metal reinforcing plate according to claim 10, wherein at least a part of said opening is formed by a side wall on the periphery of said insulating protective film of said printed wiring board.