JP3067512B2 - Production method of metal foil-clad laminate and metal foil used for the production - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a metal foil-clad laminate suitable as a material for a printed wiring board.

[0002]

2. Description of the Related Art In recent years, with the increase in density, integration, and miniaturization of electronic and electric equipment, the components mounted on a printed wiring board have been changed from insertion type discrete components to surface mount type SMDs. Is shifting to. Things to be aware of as an SMD compatible printed wiring board
There is a problem of the reliability of the solder connection between the SMD and the printed wiring. That is, the coefficient of thermal expansion in the plane direction of the laminate, which is the substrate of the printed wiring, is considerably larger than the coefficient of thermal expansion of the SMD. Therefore, when the cooling / heating cycle is repeated, the stress due to the difference in the coefficient of thermal expansion acts on the solder connection portion each time, and the solder connection portion is easily cracked. Therefore, by reducing the elasticity in the planar direction of the laminated board, which is the substrate material of the printed wiring board, the stress caused by the difference in the thermal expansion coefficient between the SMD and the board is absorbed by the low-elasticity board, and a large amount is applied to the solder connection. It is considered that the stress does not work. The laminated board impregnates the sheet-like base material with the thermosetting resin,
It is manufactured by laminating this under heat and pressure, for example, adding a flexibility-imparting agent to the thermosetting resin, or reacting the added flexibility-imparting agent with the thermosetting resin. A technique for reducing the elasticity of the steel is being studied. Further, when the thermosetting resin contains an inorganic filler, studies have been made on atomization and spheroidization of the inorganic filler.

[0003]

However, in the above-described conventional low-elasticity technology, although the elastic modulus of the laminated board can be reduced, other characteristics required for the printed wiring board, that is, heat resistance and metal properties, are required. There was a problem that the peel strength of the foil was reduced. The problem to be solved by the present invention is to provide a metal-foil-clad laminate suitable for a substrate of an SMD-compatible printed wiring board. Is to ensure the peeling strength.

[0004]

In order to solve the above-mentioned problems, a production method according to the present invention comprises placing a metal foil on a surface of a layer of a sheet-like substrate impregnated with a thermosetting resin, In the production of a metal foil-clad laminate subjected to heat and pressure molding, the metal foil has the following (1) to (4)
The composition is characterized in that the adhesive composition (A), which contains the following components, is applied. (1) Acrylonitrile butadiene rubber (2) Epoxy resin (3) Phenolic resin (4) Inorganic filler However, the amount of the inorganic filler is 6 in terms of solid content in the adhesive.
0% by weight or less. According to another manufacturing method according to the present invention, the following (1) to (4) are applied to the contact surface of the metal foil with the sheet-like substrate.
The composition is characterized in that the adhesive composition (B), which essentially contains the component (1), is applied. (1) Acrylic rubber (2) Epoxy resin (3) Epoxy resin curing agent (4) Inorganic filler However, the amount of the inorganic filler is 60 in terms of the solid content of the adhesive.
Weight percent or less. In the adhesive composition (A) or (B), the inorganic filler is preferably aluminum hydroxide. The metal foil for manufacturing a laminate according to the present invention is obtained by applying the adhesive composition (A) or (B). It is preferable that the modified silicone be contained in an amount of 50 parts or less based on 100 parts (weight in terms of solid content) of the adhesive composition (A) or (B).

[0005]

According to the method of the present invention, acrylonitrile butadiene rubber, epoxy resin, phenol resin, inorganic filler (such as aluminum hydroxide) is placed directly under the metal foil integrally attached to the surface of the laminate by heat and pressure molding. Or a layer of an adhesive composition (A) containing acrylic rubber, an epoxy resin, a curing agent for an epoxy resin, and an inorganic filler (such as aluminum hydroxide) as an essential component (B). By forming this layer, the elasticity of the substrate surface is reduced without deteriorating the characteristics required for the substrate of the printed wiring board, and the solder connection reliability is ensured as an SMD-compatible substrate. The acrylonitrile-butadiene rubber and acrylic rubber are used to impart flexibility to the layer of the adhesive composition and reduce the elastic modulus, and when these are used alone as an adhesive, The heat resistance and the peel strength of the metal foil are reduced. Similarly, when only the epoxy resin is added to the acrylonitrile-butadiene rubber or the acrylic rubber to be used as an adhesive, the heat resistance of the laminate and the peel strength of the metal foil are similarly reduced. In the layer of the adhesive composition (A), acrylonitrile-butadiene rubber is present in a cured product of an epoxy resin and a phenol resin in a sea-island structure by adding a phenol resin to the adhesive composition. Has been improved, and a decrease in heat resistance has been suppressed. In addition, in the layer of the adhesive composition (B), the addition of a curing agent for the epoxy resin (the phenol resin is also a curing agent for the epoxy resin, but is not limited to this), the same applies to the epoxy resin. Akle rubber exists in a sea-island structure in the cured product, improving the adhesiveness between the adhesive and the metal foil and suppressing a decrease in heat resistance. However, since the peel strength of the metal foil necessary and sufficient as the substrate of the printed wiring board has not yet been reached, the peel strength of the metal foil is maintained by adding an inorganic filler such as aluminum hydroxide to this. It has become possible. However, when the compounding amount of the inorganic filler exceeds 60% by weight in terms of solid content in the adhesive, the elasticity of the adhesive layer effective for lowering the elasticity increases, and the reliability of solder connection cannot be secured. . In the method of applying and drying the adhesive composition having the above-mentioned composition on the surface of a laminate having no metal foil attached to the surface, and applying the metal foil to the surface by heating and pressurizing, the printed wiring board is used. It is not possible to obtain sufficient heat resistance and peeling strength of metal foil necessary for a substrate. The adhesive composition having the above composition is applied to a metal foil in advance, and then heated and pressed together with a layer of a sheet-like base material (prepreg) impregnated with a thermosetting resin to form a substrate for a printed wiring board. It is possible to reduce the elasticity without deteriorating the characteristics and to secure the solder connection reliability as an SMD-compatible substrate.

The surface on which the adhesive composition (A) or (B) is applied to a metal foil is dried even if acrylonitrile-butadiene rubber or acrylic rubber is a relatively high-molecular and low-reactivity substance. Stickiness remains. For this reason,
If a plurality of metal foils are left stacked, the surface on which the adhesive composition is applied will stick to the surface of the metal foil on which the adhesive composition has not been applied, causing a blocking phenomenon. May cause. However, by adding the modified silicone to the adhesive composition (A) or (B), it is possible to suppress the tackiness from remaining on the surface to which the adhesive composition is applied, thereby improving the blocking phenomenon. The compounding amount of the modified silicone is one of the adhesive composition (A) or (B).
When the amount exceeds 50 parts with respect to 00 parts (weight in terms of solid content),
Since the peel strength of the metal foil on the laminate surface decreases,
It must be less than 50 parts. If aluminum hydroxide is selected as the inorganic filler contained in the adhesive composition (A) or (B), when high heat stress is applied to the surface of the laminate, the stress is absorbed by thermal decomposition of aluminum hydroxide. ,ease. By such an action, the repairability of the soldering iron of the printed wiring board (by re-soldering,
It also has the effect of improving the number of times of repetition of soldering until the metal foil peels and blisters occur.

[0007] Acrylic rubber has no unsaturated bond in the molecule. Therefore, the metal foil-clad laminate using the adhesive composition (B) is compared with the metal foil-clad laminate using the adhesive composition (A) (acrylonitrile-butadiene rubber has an unsaturated bond in the molecule). As a result, a stable color tone can be maintained with little thermal discoloration due to heating such as soldering.

[0008]

The sheet-like substrate used in the method according to the present invention is not particularly limited, and may be a glass woven fabric, a glass nonwoven fabric, a glass-paper mixed nonwoven fabric, an aramid nonwoven fabric, or the like. Further, as the thermosetting resin impregnated in these sheet-like base materials, an epoxy resin, a phenol resin, a urea resin, a polyimide, or the like can be appropriately used. These thermosetting resins, quality improvement, improvement of workability, the purpose of cost reduction, the inorganic filler _{(Al 2 O 3, Al 2} O 3 · H 2 O, Al 2
O ₃ · 3H ₂ O, talc, MgO, etc. SiO ₂₎ may be compounded. The metal foil-clad laminate manufactured by the method according to the present invention has a sheet-type substrate composed of a glass woven fabric alone, a type composed of a glass woven fabric and a glass nonwoven fabric, a type composed of an aramid nonwoven fabric alone, and a composite of the aforementioned substrate. And the type used. It also includes a metal foil-clad laminate for a multilayer printed wiring board. The metal foil used in the method according to the present invention is a copper foil, an aluminum foil, or the like, but is not particularly limited.

The acrylonitrile-butadiene rubber used as a component of the adhesive composition (A) in the method according to the present invention is desirably of a type having a carboxyl group or an epoxy group at a terminal, as shown in Chemical Formula 1. However, there is no particular limitation. Similarly, the acrylic rubber used as a component of the adhesive composition (B) is preferably of a type having a carboxyl group or an epoxy group in a side chain or a terminal and capable of crosslinking with an epoxy resin, but is particularly limited. is not. The epoxy resin used as a component of the adhesive composition (A) or (B) in the method according to the present invention is preferably a bisphenol A type epoxy resin, a phenol novolak type epoxy resin, or a cresol novolak type epoxy resin. There is no particular limitation, and bisphenol S type epoxy resin, bisphenol F type epoxy resin, alicyclic epoxy resin, naphthalene type epoxy resin and the like can be used alone or in combination. The phenol resin used as a component of the adhesive composition (A) in the method according to the present invention is not particularly limited as long as it reacts with the epoxy resin.
A phenol novolak resin using alkylphenol, cresol, or the like as a raw material can be used singly or as a mixture of several types. The curing agent for the epoxy resin used as a component of the adhesive composition (B) is as follows:
Generally, commercially available acrylic rubber contains a small amount of acrylonitrile group. Therefore, a type such as a phenol resin which can react with the acrylonitrile group and crosslink with an epoxy resin is desirable. However, there is no particular limitation as long as it reacts with the epoxy resin, and dicyandiamide, dimethylbenzylamine and the like can be used singly or as a mixture of several kinds. The inorganic filler used as a component of the adhesive composition in the method according to the present invention is preferably aluminum hydroxide, but is preferably selected from aluminum oxide (such as Al ₂ O ₃ , Al ₂ O ₃ .H ₂ O) and silica. (SiO ₂ )
Etc. can also be used. When aluminum hydroxide is used, the average particle size is preferably 0.5 to 10 μm, but is not particularly limited. In addition, those obtained by treating the surface of aluminum hydroxide particles with a silane coupling agent or the like can also be used. Further, the content of about 20 to 40% by weight of the inorganic filler is preferable because the property balance such as the peel strength of the metal foil and the reliability of the solder connection is good. The modified silicon used in the method according to the present invention comprises:
As shown in (Chemical formula 2), it is preferable to use amino-modified or epoxy-modified reactive silicon having a functional group such as an amino group or an epoxy group on a side chain or a terminal. Non-reactive silicon may be used and is not particularly limited.

[0010]

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[0011]

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Examples 1 to 7 and Comparative Examples 1 to 7 (Acrylonitrile butadiene rubber was used as a rubber component) (Preparation of adhesive composition) Acrylonitrile butadiene rubber having both ends carboxylated at the compounding amounts shown in Tables 1 and 2. (“CTBN” manufactured by Ube Industries), bisphenol A type epoxy resin (“Ep-828” manufactured by Yuka Shell Epoxy),
Novolak type phenolic resin (“TD-
2093 "), and 2-ethyl-4-methyl-imidazole (2E
4MZ) was added in an amount of 0.5 part by weight. These mixtures include:
Cellosolve acetate and methyl ethyl ketone are 1/1 by weight.
Was mixed with a homomixer to dissolve and disperse, thereby preparing an adhesive composition (A) having a solid content of 30% by weight. (Application of Adhesive Composition to Copper Foil) Adhesive Composition (A)
Is applied on a roughened surface of a copper foil having a thickness of 35 μm so that the thickness of the adhesive layer after drying is 30 μm, and then dried by heating at 160 ° C. for 60 minutes to obtain a copper foil (A) with an adhesive layer. Obtained. (Formation of metal foil-clad laminate) Bisphenol A type epoxy resin varnish was impregnated and dried in a glass woven fabric having a unit weight of 205 g / m ² to obtain a prepreg (A) having a resin adhesion amount of 40% by weight. A bisphenol A epoxy resin varnish containing an inorganic filler (resin / filler weight ratio = 1)
00/50) was impregnated and dried in a glass nonwoven fabric having a unit weight of 50 g / m ² to obtain a prepreg (B) containing a filler and having a resin adhesion amount of 84% by weight. The prepreg (B) is overlaid with 6 plies, the prepreg (A) is placed on each side by 1 ply, and the copper foil with adhesive layer (A) is placed on both sides by 1 ply with the adhesive layer side inside. Then, a 1.6 mm thick composite type copper-clad laminate was obtained by heating and pressing.

[0013]

[Table 1]

[0014]

[Table 2]

Comparative Example 8 Six layers of prepreg (B) were stacked, one ply of prepreg (A) was placed on each side, and a polyacetate film was placed on both sides. The acetate film was peeled off to obtain a 1.6 mm thick composite type laminate. The adhesive composition (A) of Example 2 was applied to the surface of this laminated plate so that the thickness of the adhesive layer after drying was 30 μm, and was dried by heating at 160 ° C. for 60 minutes. To form an adhesive layer. And
Place a 35μm thick copper foil (without adhesive layer) on both surfaces,
A 1.6 mm thick composite type copper-clad laminate was obtained by heating and pressing.

Conventional Example 1 40 parts by weight of a bisphenol A type epoxy resin ("Ep-828" manufactured by Yuka Shell Epoxy) is added to 100 parts by weight of acrylonitrile butadiene rubber having carboxylated at both ends ("CTBN" manufactured by Ube Industries). 2 as curing accelerator
0.5 parts by weight of E4MZ, toluene 30 as a diluting solvent
By weight, the mixture was reacted at 100 ° C. for 2 hours to prepare an epoxidized butadiene acrylonitrile rubber at both ends. 50 parts by weight of the above-mentioned epoxidized butadiene acrylonitrile rubber at both ends was mixed with a bisphenol A type epoxy resin 10
0 parts by weight of the varnish was mixed with a unit weight of 205 g / m ^2.
Was impregnated and dried to obtain a prepreg (C) having a resin adhesion amount of 40% by weight. Six layers of prepreg (B) are stacked, one ply of prepreg (C) is placed on each side, and one ply of 35 μm-thick copper foil (no adhesive layer) is placed on each side. 1.6 thickness
Thus, a composite type copper-clad laminate of mm was obtained.

Conventional Example 2 Six layers of prepreg (B) are stacked, one ply of prepreg (A) is arranged on each side, and 35 μm is formed on both sides.
A thick copper foil (without an adhesive layer) was placed one ply at a time, and a 1.6 mm-thick composite-type copper-clad laminate was obtained by heating and pressing.

Tables 3 and 4 show the characteristics of each of the above laminates.
The evaluation method of each characteristic in the table is as follows. (1) Copper foil peeling strength: JIS method (2) Solder heat resistance: Measure the time until blistering occurs on the surface of a sample by immersing a normal sample in a 300 ° C. solder bath (3) Solder crack: 100 samples of # 3125 chip soldered by surface mounting method (100 pieces each in the vertical and horizontal directions of the base material) were subjected to repeated cold and hot tests at -30 ° C and 120 ° C, and cracks occurred after 1000 cycles. (4) Soldering iron repairability: A 50 × 50 mm copper-clad laminate was etched to leave a 1 × 1 mm copper foil at the center, and the sample was heated to 380 ° C. Soldering iron on copper foil 1
After applying for 0 seconds, the copper foil was checked for peeling or blistering, and the above operation was repeated to measure the number of operations until the copper foil peeled and blistered. (5) Copper foil blocking property: 50 Five copper foil samples of × 50 mm were stacked and left for 24 hours under a load of 500 g from above, and the condition of sticking between the copper foils was confirmed. ○: No or almost no blocking △: Sticking, Easy peeling ×: Completely blocking and difficult to remove

[0019]

[Table 3]

[0020]

[Table 4]

Examples 8 to 14, Comparative Examples 9 to 14 (Acrylic rubber was used as a rubber component) (Preparation of adhesive composition) Acrylic rubber (LX852, manufactured by Zeon Corporation) was used in the amounts shown in Tables 5 and 6. "), Bisphenol A type epoxy resin (" Ep "
-828 "), a novolak-type phenol resin (" TD-2093 "manufactured by Dainippon Ink and Chemicals, Inc.) and aluminum hydroxide, 0.5 parts by weight of 2E4MZ as a curing accelerator was added. For the mixing, a mixed solvent of cellosolve acetate and methyl ethyl ketone in a weight ratio of 1/1 was used and stirred and dissolved and dispersed by a homomixer to prepare an adhesive composition (B) having a solid content of 30% by weight. (Application of Adhesive Composition to Copper Foil) Adhesive Composition (B)
Is applied on a roughened surface of a copper foil having a thickness of 35 μm so that the thickness of the adhesive layer after drying is 30 μm, and then dried by heating at 160 ° C. for 60 minutes to obtain a copper foil (B) with an adhesive layer. Obtained. (Formation of metal foil-clad laminate) 6 layers of prepreg (B), 1 ply of prepreg (A) on both sides, and copper foil with adhesive layer (B) on both sides with adhesive layer inside Each ply was placed, and a 1.6 mm-thick composite-type copper-clad laminate was obtained by heat and pressure molding.

Example 15 An adhesive composition was similarly prepared using dicyandiamide in place of the novolak type phenolic resin in the proportions shown in Table 5. Using this adhesive composition, a 1.6 mm-thick composite type copper-clad laminate was obtained in the same manner.

[0023]

[Table 5]

[0024]

[Table 6]

Comparative Example 15 Six layers of prepreg (B) were stacked, one ply of prepreg (A) was placed on each side, and a polyacetate film was placed on both sides. The acetate film was peeled off to obtain a 1.6 mm thick composite type laminate. The adhesive composition (B) of Example 9 was applied to the surface of the laminated plate so that the thickness of the adhesive layer after drying was 30 μm, and was dried by heating at 160 ° C. for 60 minutes. To form an adhesive layer. And
Place a 35μm thick copper foil (without adhesive layer) on both surfaces,
A 1.6 mm thick composite type copper-clad laminate was obtained by heating and pressing.

Tables 7 and 8 show the characteristics of each of the laminated plates.
The evaluation method of each characteristic in the table is the same as in the case of Tables 3 and 4. However, the discoloration over time of the laminate was evaluated as follows. The entire surface of a 50 × 50 mm copper-clad laminate is etched and subjected to -30 ° C. and 120 ° C. repeated 100 times.
After 0 cycles, the degree of surface discoloration is examined. A: No discoloration is observed. B: Discoloration is noticeable when viewed side by side with the sample before the aging treatment. C: Discoloration is apparent at a glance. Copper-clad laminate of Example 1 (acrylonitrile butadiene rubber as rubber component) Was evaluated for discoloration over time, and the evaluation was "C".

[0027]

[Table 7]

[0028]

[Table 8]

[0029]

As is clear from Tables 3 and 4, and Tables 7 and 8, according to the method of the present invention, the characteristics suitable for a metal foil-clad laminate used for a substrate of an SMD-compatible printed wiring board. That is, it is possible to reduce the elasticity of the surface layer centering on the surface direction necessary for ensuring the solder connection reliability of the SMD, and at the same time, secure the peel strength and heat resistance of the metal foil. When aluminum hydroxide is used as the inorganic filler, when a high heat load is applied to the laminate surface, the stress is absorbed by thermal decomposition of the aluminum hydroxide,
Be relaxed. By such an action, the repairability of the soldering iron of the printed wiring board (the number of repetitions of soldering until the metal foil peels and bulges when the soldering is repeated in the same place, but the metal foil peels and bulges) is improved. Can be improved. By improving the repairability of the soldering iron, the reliability of solder connection by the conventional soldering method using a soldering iron has been improved, making it a laminated board for printed wiring boards suitable for consumer boards etc. be able to. Also,
When the modified silicone is added to the adhesive composition in an amount of 50 parts by weight or less with respect to 100 parts by weight, blocking of the metal foils that occurs when the metal foils coated with the adhesive composition are left stacked is also reduced. Can be suppressed. And
By limiting the amount, the characteristics of the metal foil-clad laminate are not deteriorated. In the invention in which acrylic rubber is selected as the rubber component of the adhesive composition, the discoloration of the laminate surface due to heat is small, and the appearance is excellent.

────────────────────────────────────────────────── (5) References JP-A-62-60290 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B32B 15/08 105 H05K 1/03 650

Claims (8)

(57) [Claims] 1. A method for manufacturing a metal foil-clad laminate in which a metal foil is placed on the surface of a sheet-like base material layer impregnated with a thermosetting resin, and is formed by heating and pressing the metal foil. A method for producing a metal foil-clad laminate, characterized in that an adhesive composition (A) having the following components (1) to (4) as essential components is applied in advance to a contact surface with a substrate in the form of a metal foil. . (1) Acrylonitrile butadiene rubber (2) Epoxy resin (3) Phenolic resin (4) Inorganic filler However, the amount of the inorganic filler is 6 in terms of solid content in the adhesive.
0% by weight or less. 2. A metal foil for producing a metal foil-clad laminate, which is coated with an adhesive composition (A) having the following components (1) to (4) as essential components. (1) Acrylonitrile butadiene rubber (2) Epoxy resin (3) Phenolic resin (4) Inorganic filler However, the amount of the inorganic filler is 6 in terms of solid content in the adhesive.
0% by weight or less. 3. A method for producing a metal foil-clad laminate in which a metal foil is placed on the surface of a layer of a sheet-like base material impregnated with a thermosetting resin and is heated and pressed to form a sheet. A method for producing a metal foil-clad laminate, characterized in that an adhesive composition (B) having the following components (1) to (4) as essential components is applied in advance to a contact surface with a substrate in the form of a metal foil. . (1) Acrylic rubber (2) Epoxy resin (3) Epoxy resin curing agent (4) Inorganic filler However, the amount of the inorganic filler is 60 in terms of the solid content of the adhesive.
Weight percent or less. 4. A metal foil for producing a metal foil-clad laminate, which is coated with an adhesive composition (B) having the following components (1) to (4) as essential components. (1) Acrylic rubber (2) Epoxy resin (3) Epoxy resin curing agent (4) Inorganic filler However, the amount of the inorganic filler is 60 in terms of the solid content of the adhesive.
Weight percent or less. 5. The method according to claim 1, wherein the inorganic filler is aluminum hydroxide. 6. The adhesive composition according to claim 1, wherein the weight ratio is 100
The method for producing a metal-foil-clad laminate according to any one of claims 1, 3, and 5, wherein the modified silicon is blended in 50 parts or less per part. 7. The metal foil according to claim 2, wherein the inorganic filler is aluminum hydroxide. 8. The adhesive composition according to claim 1, wherein the weight ratio is 100
The metal foil for producing a metal-foil-clad laminate according to any one of claims 2, 4, and 7, wherein the metal foil contains not more than 50 parts of modified silicon per part.