TWI699787B - Conductive adhesive composition - Google Patents

Abstract

The present invention relates to a conductive adhesive composition which contains at least one of thermoplastic resin and thermosetting resin, conductive filler and inorganic particles. The cumulative frequency of inorganic particles measured with a laser diffraction particle size distribution measuring device at a particle size of 5μm is below 40%, and the amount of inorganic particles added to the entire conductive adhesive composition is 10-30% by mass.

Description

Conductive adhesive composition

The present invention relates to a conductive adhesive composition for printed circuit boards.

In the prior art, in order to attach a reinforcing plate and an electromagnetic wave shielding film to a printed circuit board, a conductive adhesive is generally used, and the conductive adhesive is formed by adding a conductive filler to an adhesive resin composition. When attaching the reinforcing plate and the electromagnetic wave shielding film to the printed circuit board, an opening is formed in the cover layer of the printed circuit board to expose the circuit made of copper foil, etc., and the conductive adhesive is filled in the opening , To make the electrical connection between the circuit and the reinforcing plate and the electromagnetic wave shielding film.

Such conductive adhesives include, for example, the following adhesives that have been disclosed: an adhesive prepared by adding conductive fillers and silica particles with a predetermined specific surface area to a thermosetting resin. It is also stated that by adding these silicon dioxide particles, it is possible to suppress damage to the insulating layer without affecting the flexibility of the entire electromagnetic wave shielding film (for example, refer to Patent Document 1). Such conductive adhesives have also been disclosed as follows: conductive adhesives formed of an inorganic filler having a predetermined particle size and an adhesive composition containing a thermosetting resin. It is also described that by using such conductive adhesives, the connection reliability of circuits with high moisture and heat resistance and high through-hole height is improved (for example, refer to Patent Document 2).

〔Patent Literature〕

[Patent Document 1] JP 2015-53412 A

[Patent Document 2] Japanese Patent No. 5892282

In this case, generally speaking, once the conductive adhesive is exposed to the reflow process (such as 270°C for 10 seconds), its conductivity and adhesion to the printed circuit board will decrease, so It is necessary for the conductive adhesive to have reflow resistance (high heat resistance to withstand the reflow process, conductivity after the reflow process, and high adhesion to the printed circuit board). In recent years, there has been a trend toward miniaturization of electronic substrates, and therefore, the hole diameter of the opening provided in the cover layer also tends to become smaller.

However, the adhesives described in Patent Documents 1 and 2 have the following problem: If the hole diameter of the opening provided in the cover layer becomes smaller, the connection resistance value increases after being exposed to the reflow process.

The present invention was completed in view of the above problems, and its purpose is to provide a conductive adhesive composition that can ensure that the conductive adhesive composition has excellent conductivity after reflow.

In order to achieve the above object, the conductive adhesive composition of the present invention is characterized in that it contains at least one of thermoplastic resin and thermosetting resin, conductive filler and inorganic particles, and the inorganic particles are measured by a laser diffraction particle size distribution measuring device. The cumulative frequency under the 5μm particle size is below 40%.

The conductive adhesive composition according to another aspect of the present invention is characterized in that it contains at least one of a thermoplastic resin and a thermosetting resin, a conductive filler, and inorganic particles, and the inorganic particles are measured by a laser diffraction particle size distribution measuring device. The cumulative frequency under 10μm particle size is below 80%.

It should be noted that the "cumulative frequency" mentioned here refers to the particle size distribution curve obtained by a laser diffraction particle size distribution measuring device (the vertical axis is the cumulative frequency %, and the horizontal axis is the particle size). The cumulative frequency accumulated on one side.

According to the present invention, it is possible to provide a conductive adhesive composition that has excellent conductivity even after reflow.

1‧‧‧Conductive adhesive film

2‧‧‧Releasable substrate

4‧‧‧Conductive adhesive layer

13‧‧‧Protection layer

14‧‧‧Metal layer

15‧‧‧Conductive reinforcement board

20‧‧‧Electromagnetic wave shielding film

21‧‧‧Electromagnetic wave shielding film

30‧‧‧Shielded printed circuit board

31‧‧‧Shielded printed circuit board

32‧‧‧Shielded printed circuit board

40‧‧‧Printed Circuit Board

41‧‧‧Substrate

42‧‧‧Printed Circuit

43‧‧‧Insulating adhesive layer

44‧‧‧Cover

45‧‧‧Opening

46‧‧‧Plating

47‧‧‧Printed Circuit Board

Fig. 1 is a cross-sectional view of a conductive adhesive film related to an embodiment of the present invention.

2 is a cross-sectional view of a shielded printed circuit board related to the embodiment of the present invention.

Fig. 3 is a cross-sectional view of a shielded printed circuit board related to an embodiment of the present invention.

Fig. 4 is a cross-sectional view of a shielded printed circuit board related to the embodiment of the present invention.

Fig. 5 is a cross-sectional view of a flexible circuit board used in the embodiment.

Fig. 6 is for explaining the method of measuring the resistance value in the embodiment.

The conductive adhesive composition of the present invention will be specifically described below. It should be noted that the present invention is not limited to the following embodiments, and can be applied with appropriate changes within the scope of not changing the gist of the present invention.

The conductive adhesive composition of the present invention is such that it contains at least one of a thermoplastic resin and a thermosetting resin, a conductive filler, and inorganic particles. The inorganic particles are 5μm particles measured by a laser diffraction particle size distribution measuring device. Inorganic particles whose cumulative frequency is below 40%.

The thermosetting resin is not particularly limited, and polyamide resins, polyimide resins, acrylic resins, phenolic resins, epoxy resins, polyurethane resins, polyurethane urea resins, melamine resins, and alkyd resins can be used. Resin etc. One of the above resins may be used alone, or two or more of the above resins may be used in combination.

The thermosetting resin is not particularly limited, and a phenol resin composition, an epoxy resin composition, a urethane resin composition, a melamine resin composition, an alkyd resin composition, etc. can be used. One kind of the above-mentioned resins may be used alone, or two or more kinds of the above-mentioned resins may be used in combination.

<Conductive filler>

The conductive adhesive film of the present invention contains a conductive filler. The conductive filler is not particularly limited. For example, a metal filler, a metal-coated resin filler, a carbon filler, and a mixture of the above fillers can be used. The above-mentioned metal fillers include, for example, copper powder, silver powder, nickel powder, silver-coated copper powder, gold-coated copper powder, silver-coated nickel powder, and gold-coated nickel powder. The metal powder can be prepared by electrolysis, atomization, or reduction to make.

In particular, in order to make the fillers easy to contact each other, the average particle size of the conductive filler is preferably 3-50 μm. The shape of the conductive filler includes, for example, a spherical shape, a flake shape, a dendritic shape, and a fiber shape.

From the viewpoint of connection resistance and cost, the conductive filler is preferably at least one metal powder selected from the group consisting of silver powder, silver-coated copper powder, and copper powder.

The ratio of the conductive filler contained in the conductive adhesive composition is preferably 40 to 90% by mass of the total amount of the conductive adhesive composition.

It is also possible to add silane coupling agents, antioxidants, pigments, dyes, tackifying resins, plasticizers, ultraviolet absorbers, defoamers, leveling agents, and fillers to the conductive adhesive film within the range that the reflow resistance does not decrease. Agent, flame retardant, etc.

<Inorganic particles>

The cumulative frequency of the inorganic particles contained in the conductive adhesive composition of the present invention measured by a laser diffraction particle size distribution measuring device at a particle size of 5 μm is below 40%. If the cumulative frequency under 5μm particle size exceeds 40%, the number of inorganic particles with a smaller particle size will increase, making it difficult for the conductive filler to be fixed between the inorganic particles. The heat during reflow will cause thermoplastic resin (or thermosetting resin) Flow, the connection between the conductive fillers may be broken due to the flow, so the connection resistance may not be sufficiently reduced after reflow.

The inorganic particles may also be inorganic particles with a cumulative frequency of less than 80% at a particle size of 10 μm measured by a laser diffraction particle size distribution measuring device. If the cumulative frequency under 10μm particle size exceeds 80%, inorganic particles with a smaller particle size will increase. As mentioned above, the heat during reflow will cause the thermoplastic resin (or thermosetting resin) to flow, and the conductive fillers will flow between each other. The connection may be broken due to this flow, so the connection resistance may not be sufficiently reduced after reflow.

It should be noted that the cumulative frequency at particle sizes of 5 μm and 10 μm can be measured with a commercially available laser diffraction particle size distribution measuring device (for example, manufactured by Microtrac Co., Ltd., trade name: MICROTRAC S3500).

The inorganic particles are not particularly limited. For example, there are silicon dioxide, aluminum oxide, aluminum hydroxide, magnesium hydroxide, barium sulfate, calcium carbonate, titanium oxide, zinc oxide, antimony trioxide, magnesium oxide, talc, montmorillonite, and kaolin. , Bentonite and other inorganic compounds. Among the above-mentioned inorganic compounds, it is preferable to use silicon dioxide particles from the viewpoint of cost.

The ratio of the inorganic particles contained in the conductive adhesive composition is preferably 10-30% by mass of the total amount of the conductive adhesive composition, more preferably 10-25% by mass. This is because if the content of inorganic particles is less than 10% by mass, the connection stability after reflow will be poor, and if the content of inorganic particles exceeds 30% by mass, it may be difficult to add more inorganic particles. The conductive adhesive composition may be applied to the surface of a peelable substrate or the like, or the conductivity of the conductive adhesive composition may decrease.

The average particle diameter of the inorganic particles is preferably 1-15 μm, more preferably 2-10 μm. This is because if the average particle size is less than 1 µm, the film-forming properties of the conductive adhesive composition will decrease, making it difficult to control the thickness. On the other hand, if the average particle size exceeds 15 μm, it is difficult to reduce the thickness.

<curing agent>

The conductive adhesive film of the present invention may further contain a curing agent as necessary. The curing agent is not particularly limited. For example, a conventionally known curing agent such as an isocyanate compound, a blocked isocyanate compound, a carbodiimide compound, an imidazole compound, an oxazoline compound, a melamine, and a metal complex crosslinking agent can be used.

The above-mentioned curing agent can improve heat resistance and the like with an appropriate amount. However, if the amount of curing agent used is too much, it may result in a decrease in flexibility and adhesion. Therefore, with respect to 100 parts by mass of the resin component of the thermosetting resin, the amount of the curing agent used is preferably 0.1 to 200 parts by mass or less, more preferably 0.2 to 100 parts by mass, and particularly preferably 0.2 to 50 parts by mass.

In order to promote the curing of the curing agent, the conductive adhesive film of the present invention may also be used in combination with an imidazole curing accelerator. The curing accelerator is not particularly limited. For example, there are the following compounds formed by the addition of an imidazole ring and an alkyl group, a cyanoethyl group, a hydroxyl group, an azine, etc.: 2-phenyl-4,5-bishydroxymethylimidazole, 2-Heptadecyl imidazole, 2,4-bisamino-6-(2'-undecylimidazole) ethyl-S-triazine, 1-cyanoethyl-2-phenylimidazole, 2- Phenylimidazole, 5-cyano-2-phenylimidazole, 2,4-diamino-6-[2'methylimidazole-(1')]-ethyl-S-triazine isocyanuric acid Adduct, 2-phenyl isocyanuric acid adduct, 2-methyl isocyanuric acid adduct, 1-cyanoethyl-2-phenyl-4,5-bis(2-cyanuric acid Ethoxy) methyl imidazole and the like. The above-mentioned curing accelerator can improve heat resistance and the like with an appropriate amount. However, if the curing accelerator is used in an excessive amount, it may cause a decrease in flexibility and adhesion. Therefore, the amount of the curing accelerator used is preferably 0.01 to 1.0 parts by mass relative to 100 parts by mass of the resin component of the thermosetting resin.

<Conductive Adhesive Film>

As shown in Figure 1, the conductive adhesive film 1 of the present invention includes a peelable substrate 2 (release film) and a conductive adhesive layer 4, the conductive adhesive layer 4 is coated with the above conductive adhesive composition It is formed on the surface of the peelable substrate 2. It should be noted that the coating method is not particularly limited. Well-known coating machines can be used, and representative methods such as die coating, lip coating, and comma coating can be used. . It should be noted that the conditions when applying the conductive adhesive composition to the peelable base material 2 may be set appropriately.

The peelable substrate 2 can be used: a silicone-based release agent or a non-silicon-based release agent is coated on a base film such as polyethylene terephthalate, polyethylene naphthalate, etc. A substrate made on the side surface where the conductive adhesive layer 4 is formed. In addition, the thickness of the peelable base material 2 is not specifically limited, It can determine suitably in consideration of convenience of use.

The thickness of the conductive adhesive layer 4 is preferably 15-100 μm. If it is thinner than 15 μm, the embedment is insufficient, and it may not be reliably connected to the ground circuit. If it is thicker than 100 μm, it is disadvantageous in cost and cannot meet the demand for thinning. By setting the conductive adhesive layer 4 to the above thickness, when there are irregularities on the substrate, the conductive adhesive composition will flow moderately and become a shape that bury the concave portion, so that it can be adhered with good adhesion. .

<Anisotropic conductive adhesive layer, isotropic conductive adhesive layer>

According to the purpose of use, the conductive adhesive composition of the present invention can be used to form an anisotropic conductive adhesive layer or an isotropic conductive adhesive layer. For example, if the conductive adhesive composition of the present invention is used to form a conductive adhesive film for adhering to a reinforcing plate, an isotropic conductive adhesive layer can be formed.

If it is an electromagnetic wave shielding film with a metal layer, the conductive adhesive composition of the present invention can be used to form an isotropic conductive adhesive layer or an anisotropic conductive adhesive layer, but an anisotropic conductive adhesive can be formed The layer is better.

It should be noted that the conductive adhesive composition of the present invention can form different adhesive layers depending on the amount of conductive filler added. In order to use the conductive adhesive composition of the present invention to form an anisotropic conductive adhesive layer, the amount of conductive filler added is preferably 5% by mass or more and less than 40% by mass of the total solid content of the conductive adhesive composition . In order to form an isotropic conductive adhesive layer with the conductive adhesive composition of the present invention, the conductive filler is preferably 40% by mass to 90% by mass of the total solid content of the conductive adhesive composition.

The conductive adhesive film formed with the conductive adhesive of the present invention has excellent adhesion to a printed circuit board, and its adhesion to the printed circuit board includes that of resin boards such as polyimide films. Adhesion between metal materials and metal materials such as gold-plated copper foil or conductive reinforcing plates.

<Electromagnetic wave shielding film>

As shown in FIG. 2, the electromagnetic wave shielding film 20 formed with the conductive adhesive composition of the present invention includes a conductive adhesive layer 4 and a protective layer 13, and the protective layer 13 is provided on the surface of the conductive adhesive layer 4. The protective layer 13 is not particularly limited, as long as it has insulating properties (that is, it is formed of an insulating resin composition), and a known protective layer can be used.

As the insulating resin composition, for example, a thermoplastic resin composition, a thermosetting resin composition, an active energy ray curable composition, etc. can be used. The thermoplastic resin composition is not particularly limited, and polyamide resins, polyimide resins, acrylic resins, polyester resins, urethane resins, polycarbonate resins, and polyolefin resins can be used. , Styrene resin composition, vinyl acetate resin composition, etc. The thermosetting resin composition is not particularly limited, and a phenolic resin composition, epoxy resin composition, urethane resin composition, melamine resin composition, alkyd resin composition, etc. can be used. The active energy ray-curable composition is not particularly limited, and, for example, a polymerizable compound containing at least two (meth)acryloxy groups in the molecule can be used.

The protective layer 13 may also use the resin component (components other than the conductive filler) used in the conductive adhesive layer 4 described above. The protective layer 13 may also be a laminate composed of two or more layers having different physical properties, such as material, hardness or elastic coefficient.

The thickness of the protective layer 13 is not particularly limited, and can be appropriately set as required, and can be set to 1 μm or more (preferably 4 μm or more) and 20 μm or less (10 μm or less preferably, 5 μm or less).

The protective layer 13 may also contain curing accelerators, adhesion-imparting agents, antioxidants, pigments, dyes, plasticizers, ultraviolet absorbers, defoamers, leveling agents, fillers, flame retardants, viscosity regulators, and anti-sticking agents as needed.剂 etc.

The electromagnetic wave shielding film 20 is formed, for example, by the following method: a resin composition for a protective layer is coated on one surface of a peelable film and dried to form a protective layer 13, and then the above-mentioned conductive layer is coated on the protective layer 13. The adhesive composition is dried to form the conductive adhesive layer 4.

The method for forming the conductive adhesive layer 4 and the protective layer 13 can use coating methods known in the prior art, such as gravure coating, kiss coating, die coating, and lip coating. Mouth coating, comma coating, blade coating, roll coating, knife coating, spray coating, bar coating coating), spin coating (spin coating), dip coating (dip coating), etc.

The electromagnetic wave shielding film 20 may be adhered to the printed circuit board by heat and pressure. The conductive adhesive layer 4 of the electromagnetic wave shielding film 20 is softened by heating, and flows into the ground portion provided on the printed circuit board due to pressure. As a result, the ground circuit and the conductive adhesive are electrically connected, and the shielding effect can be improved.

The electromagnetic wave shielding film 20 can be used to form the shielding printed circuit board 30 shown in FIG. 2, for example. The shielding printed circuit board 30 includes a printed circuit board 40 and an electromagnetic wave shielding film 20.

The printed circuit board 40 includes a base substrate 41, a printed circuit (ground circuit) 42, an insulating adhesive layer 43 and a cover layer 44. The printed circuit 42 is formed on the base substrate 41, the insulating adhesive layer 43 is disposed on the base substrate 41 and is adjacent to the printed circuit 42, and the covering layer 44 is insulating and covers the insulating adhesive layer 43. It should be noted that the insulating layer of the printed circuit board 40 is composed of an insulating adhesive layer 43 and a cover layer 44. An opening 45 is formed on the insulating adhesive layer 43 and the cover layer 44. The opening 45 is used for printing A part of the circuit 42 is exposed.

The base substrate 41, the insulating adhesive layer 43, and the cover layer 44 are not particularly limited, and may be, for example, a resin film. In this case, it may be formed of resin such as polypropylene, cross-linked polyethylene, polyester, polybenzimidazole, polyimide, polyimide, polyetherimide, or polyphenylene sulfide. The printed circuit 42 may be a copper wire pattern or the like formed on the base substrate 41, for example.

Next, a method of manufacturing the shield printed circuit board 30 will be described. The electromagnetic wave shielding film 20 is placed on the printed circuit board 40, and heated and pressurized with a press machine. The conductive adhesive layer 4 is softened by heating, and a part of it flows into the opening 45 by pressure. In this way, the electromagnetic wave shielding film 20 is attached to the printed circuit board 40 via the conductive adhesive layer 4.

<Electromagnetic wave shielding film with metal layer>

The electromagnetic wave shielding film of the present invention may also have a metal layer. Due to the metal layer, more excellent electromagnetic wave shielding performance can be achieved.

More specifically, as shown in FIG. 3, the electromagnetic wave shielding film 21 formed with the conductive adhesive composition of the present invention includes a metal layer (shielding layer) 14, a conductive adhesive layer 4, and a protective layer 13. The conductive adhesive The agent layer 4 is provided on the side of the first side of the metal layer 14, the protective layer 13 is provided on the side of the second side of the metal layer 14, and the second side is on the side opposite to the first side.

The metal material forming the metal layer 14 includes, for example, nickel, copper, silver, tin, gold, palladium, aluminum, chromium, titanium, zinc, and alloys containing one or more of the above materials, which can be used according to the required electromagnetic shielding effect , Repetitive bending resistance and sliding resistance are appropriately selected.

The thickness of the metal layer 14 is not particularly limited, and may be, for example, 0.1 μm to 8 μm. It should be noted that the method for forming the metal layer 14 includes an electroplating method, an electroless plating method, a sputtering method, an electron beam evaporation method, a vacuum evaporation method, a CVD method, an organic metal, and the like. The metal layer 14 may be metal foil or metal nanoparticle.

This electromagnetic wave shielding film 21 can be used to form the shielding printed circuit board 31 shown in FIG. 3, for example. The shielding printed circuit board 31 includes the above-mentioned printed circuit board 40 and an electromagnetic wave shielding film 21.

Next, a method of manufacturing the shield printed circuit board 31 will be described. The electromagnetic wave shielding film 21 is placed on the printed circuit board 40 and heated and pressurized with a press machine. The adhesive layer 4 is softened by heating, and a part of it flows into the opening 45 by pressure. In this way, the electromagnetic wave shielding film 21 is attached to the printed circuit board 40 by the adhesive layer 4, and the metal layer 14 and the printed circuit 42 of the printed circuit board 40 are connected by a conductive adhesive, and the metal layer 14 The printed circuit 42 is connected.

<Shielded printed circuit board including reinforcing plate>

The conductive adhesive composition of the present invention can be used to form a shielded printed circuit board including a reinforcing plate. More specifically, for example, it can be used to form the shielded printed circuit board 32 shown in FIG. 4. The shielding printed circuit board 32 includes a printed circuit board 47, a conductive adhesive layer 4 and a conductive reinforcing plate 15. The printed circuit board 47 and the conductive reinforcing plate 15 are adhered and electrically connected by the conductive adhesive layer 4 of the present invention.

The printed circuit board 47 is configured such that a plating layer (such as a gold plating layer) 46 is provided on a part of the surface of the printed circuit 42, and the plating layer 46 is exposed from the opening 45.

It should be noted that, similar to the shield printed circuit board 30 shown in FIG. 2 described above, the following structure may be adopted: instead of providing the plating layer 46, the conductive adhesive layer 4 flowing into the opening 45 directly connects the printed circuit 42 is connected to the conductive reinforcing plate 15.

The purpose of providing the conductive reinforcing plate 15 is to prevent the occurrence of the following situations: on the printed circuit board where the electronic component is packaged, the portion where the electronic component is packaged is strained due to the bending of the printed circuit board, causing damage to the electronic component. As the conductive reinforcing plate 15, a conductive metal plate or the like can be used. For example, a stainless steel plate, iron plate, copper plate, or aluminum plate can be used. Among the above metal plates, a stainless steel plate is more preferable. By using stainless steel plate, even if its thickness is thin, it will have enough strength to support electronic components.

The thickness of the conductive reinforcing plate 15 is not particularly limited, but is preferably 0.025 to 2 mm, and more preferably 0.1 to 0.5 mm. As long as the thickness of the conductive reinforcing plate 15 is within the above-mentioned range, the circuit board to which the conductive reinforcing plate 15 is adhered can be easily built in a small device and has sufficient strength to support the packaged electronic components. On the surface of the conductive reinforcing plate 15, a metal layer such as Ni or Au may be formed by plating or the like. It is also possible to give the surface of the conductive reinforcing plate 15 an uneven shape by sandblasting, etching, or the like.

It should be noted that, in addition to connectors and ICs, the electronic components mentioned here also include chip-type components such as resistors and capacitors.

Next, a method of manufacturing the shield printed circuit board 32 will be described. First, the conductive adhesive film constituting the conductive adhesive layer 4 is placed on the conductive reinforcing plate 15 and heated and pressurized with a press machine to produce a conductive adhesive film with a reinforcing plate. Then, a conductive adhesive film with a reinforcing plate is placed on the printed circuit board 47, and heated and pressurized with a press. The adhesive layer 4 is softened by heating, and a part of it flows into the opening 45 by pressure. In this way, the conductive reinforcing plate 15 is attached to the printed circuit board 47 by the adhesive layer 4, and the conductive reinforcing plate 15 and the printed circuit 42 of the printed circuit board 47 are connected by the conductive adhesive. The conductive reinforcing plate 15 and the printed circuit 42 are in a conductive state. Therefore, the electromagnetic wave shielding performance can be obtained by the conductive reinforcing plate 15.

It should be noted that after the conductive adhesive film is formed from the conductive adhesive composition of the present invention, a representative example of the adherend to which the conductive adhesive film can be attached is a flexible circuit board that undergoes repeated bending. Of course, it can also be applied For rigid printed circuit boards. Moreover, it is not limited to single-sided shielded circuit boards, but can also be applied to double-sided shielded circuit boards.

Example

Hereinafter, the present invention will be described based on examples. It should be noted that the present invention is not limited by these embodiments, and these embodiments can be modified or changed based on the spirit of the present invention, and these modifications or changes should not be excluded from the scope of the present invention.

(Examples 1 to 3, Comparative Examples 1 to 3)

<Preparation of conductive adhesive composition>

The conductive adhesive compositions of Examples 1 to 3 and Comparative Examples 1 to 5 were prepared by the following preparation methods, and they had the composition (mass %) shown in Table 1.

To the following materials constituting the resin composition shown in Table 1, silver-coated copper powder, which is a conductive filler, and spherical silica particles, which are inorganic particles, were added to prepare a paste-like conductive adhesive composition.

Thermoplastic resin: The complex viscosity at 150°C is 8.2×10 ³ Pa. s polyamide resin with anhydrous carboxyl group at the end

Thermosetting resin: Glycidylamine epoxy resin (manufactured by Mitsubishi Chemical Corporation, trade name: jER604)

Silane coupling agent: manufactured by Shin-Etsu Chemical Co., Ltd., trade name: KBM-602

Cyanate curing agent: manufactured by Lonza Japan Ltd., trade name: PT-30

Imidazole curing agent: manufactured by Shikoku Chemical Co., Ltd., trade name: 2MZ-H

【Table 1】

<Measurement of the cumulative frequency of inorganic particles>

The cumulative frequency of inorganic particles containing the conductive adhesive compositions of Examples 1 to 3 and Comparative Examples 1 to 5 was measured. More specifically, a laser diffraction particle size distribution measuring device (manufactured by Microtrac Co., Ltd., trade name: MICROTRAC S3500) was used, pure water was used as a solvent (refractive index=1.33), and the refractive index of inorganic particles was set to 1.51. The volume distribution pattern was measured. The above results are shown in Table 1.

<Production of electromagnetic wave shielding film>

Then, an electromagnetic wave shielding film was produced using the above-mentioned conductive adhesive composition. More specifically, a PET film with a thickness of 60 μm and a release treatment on the surface was used as the supporting substrate. Then, a protective layer composition (solid content 30% by mass) composed of bisphenol A epoxy resin (manufactured by Mitsubishi Chemical Corporation, jER1256) and methyl ethyl ketone was coated on the supporting substrate, and heated and dried. A 5 μm thick supporting substrate with a protective layer was produced.

Then, a shielding layer was formed on the surface of the protective layer. More specifically, a rolled copper foil with a thickness of 2 μm was attached to the protective layer.

Then, the conductive adhesive compositions prepared in Examples 1 to 3 and Comparative Examples 1 to 5 were coated on the surface of the shielding layer to form a 5 μm thick adhesive layer, thereby fabricating an electromagnetic wave shielding film.

<Production of shielded printed circuit board>

Then, the produced electromagnetic wave shielding film and the printed circuit board are laminated so that the adhesive layer of the electromagnetic wave shielding film faces the printed circuit board, and then heated and pressurized for 1 minute at 170°C and 3.0 MPa using a press , Heat and press at the same temperature and pressure for 3 minutes, and peel off the supporting base material from the protective layer to produce a shielded printed circuit board.

The printed circuit board includes two copper foil patterns and an insulating layer (thickness: 25μm). The two copper foil patterns are spaced apart and extend parallel to each other. The insulating layer covers the copper foil pattern and is formed of polyimide, on the insulating layer An opening (diameter: 0.8 mm) through which each copper foil pattern is exposed is provided. The adhesive layer of the electromagnetic wave shielding film is superimposed on the printed circuit board so that the opening is completely covered by the electromagnetic wave shielding film.

It should be noted that the end of the copper foil pattern of the printed circuit board used is not covered by the insulating layer, but is exposed.

<Evaluation of Reflow Resistance>

Then, the reflow resistance of the manufactured shielded printed circuit board was evaluated. The condition for reflow is to set the temperature profile in consideration of the use of lead-free solder to ensure that the shielding film on the shielding printed circuit board is exposed to 265°C for 1 second.

After exposing the shielded printed circuit boards of Examples 1 to 3 and Comparative Examples 1 to 5 to the temperature conditions of the above curve for 1 to 5 times, as shown in FIG. 6, 52 pairs of resistance meters were formed on the printed circuit The resistance value between the two copper foil patterns 51 on the board 50 was measured, and the connectivity between the copper foil pattern 51 and the electromagnetic wave shielding film 53 was evaluated.

The above reflow process was performed once, twice, 3 times, 5 times, and the resistance value change after reflow was evaluated. The above results are shown in Table 2.

【Table 2】

As shown in Table 2, the conductive adhesive composition used in Examples 1 to 3 contains inorganic particles with a cumulative frequency of less than 40% (or a cumulative frequency of less than 80% under a particle diameter of 10 μm) at a particle size of 5 μm, and Compared with Comparative Examples 1 to 3, the increase in the connection resistance value after the reflow process is effectively suppressed, and it can be said that it can guarantee excellent electrical conductivity after the reflow process.

〔Industry availability〕

In summary, the present invention is applicable to conductive adhesive compositions for forming printed circuit boards.

1‧‧‧Conductive adhesive film

2‧‧‧Releasable substrate

4‧‧‧Conductive adhesive layer

Claims (5)

A conductive adhesive composition containing at least one of a thermoplastic resin and a thermosetting resin, a conductive filler, and inorganic particles. The conductive adhesive composition is characterized in that the inorganic particles have a laser diffraction particle size The cumulative frequency at a particle size of 5 μm measured by the distribution measuring device is 40% or less, and the addition amount of the inorganic particles relative to the entire conductive adhesive composition is 10-30% by mass. A conductive adhesive composition containing at least one of a thermoplastic resin and a thermosetting resin, a conductive filler, and inorganic particles. The conductive adhesive composition is characterized in that the inorganic particles have a laser diffraction particle size The cumulative frequency at a particle size of 10 μm measured by the distribution measuring device is below 80%, and the addition amount of the inorganic particles to the entire conductive adhesive composition is 10-30% by mass. A conductive adhesive film, characterized in that the conductive adhesive film comprises a peelable substrate and a conductive adhesive layer, the conductive adhesive layer is provided on the surface of the peelable substrate, and is defined by claim 1 Or the conductive adhesive composition described in 2 is formed. An electromagnetic wave shielding film, characterized in that the electromagnetic wave shielding film includes a protective layer and a conductive adhesive layer, the protective layer has insulation, the conductive adhesive layer is provided on the surface of the protective layer, and is requested The conductive adhesive composition according to item 1 or 2 is formed. A printed circuit board, wherein the printed circuit board includes a base substrate, a conductive adhesive layer, and a conductive reinforcing plate, a printed circuit is formed on the base substrate, and the conductive adhesive layer is defined by claim 1 Or the conductive adhesive composition described in 2 is formed, wherein the base substrate and the conductive reinforcing plate are electrically connected by the conductive adhesive layer.

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