JPH08244165A - Manufacture of metal foil-clad laminate and metal foil for metal foil-clad laminate - Google Patents

Abstract

PURPOSE: To manufacture with good workability a metal foil-clad laminate suitable for a material for a printed wire board for surface mounting by leaving no adhesiveness on a coated surface of a metal foil coated with a resin composition of low elasticity and also controlling the curling of metal foil. CONSTITUTION: A first resin composition composed of acryl rubber, epoxy resin, phenol resin and an inorganic filler is applied onto a roughened surface of a metal foil, and also a second resin composition in the dried state and having no adhesiveness and elasticity higher than those of the first resin composition is applied to the coated surface and dried. Then the coated surface of metal foil is overlapped on a prepreg layer and heat pressurized molding is carried out, and a low elasticity resin layer composed of the first resin composition of thickness of 20μm and elasticity modulus of 10kgf/mm<2> or over is formed right under the metal foil. The second resin composition is composed of a component, for instance, similar to that of the first resin composition, and the contents of the inorganic filler and epoxy resin are more than those of the first resin composition.

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 for surface mounting and a metal foil.

[0002]

2. Description of the Related Art In a surface mount printed wiring board, the coefficient of thermal expansion of a surface mount ceramic chip resistor is 7 ppm /
℃ is small, the thermal expansion coefficient of the printed wiring board substrate (made of metal foil-clad laminate) is 14-22p
As large as pm / ° C. Therefore, when the cooling / heating cycle is repeated, stress is applied to the solder connection portion of the ceramic chip component due to the difference in thermal expansion coefficient between the ceramic chip component and the substrate. Eventually, there is a possibility that cracks may occur in the solder connection portion, leading to disconnection. Therefore, in order to reduce the coefficient of thermal expansion of the metal foil-clad laminate, which is the material of the printed wiring board,
A technology for incorporating an inorganic filler in a thermosetting resin in a laminated plate in which a metal foil is placed on the surface of a layer of a prepreg obtained by impregnating and drying a sheet-shaped base material with a thermosetting resin and heat-molded There is. Further, in order to relieve the stress applied to the solder connection portion, disposing a low elastic resin layer under the metal foil has been studied. For example, it is a method of manufacturing a metal foil-clad laminate by applying a resin composition containing acrylonitrile butadiene rubber or acrylic rubber to a metal foil in advance, placing the resin composition on a layer of a prepreg, and heat-pressing it.

[0003]

However, in the technique of incorporating the above-mentioned inorganic filler, the coefficient of thermal expansion of the laminated plate is not as low as expected and the elastic modulus of the laminated plate is high. Cracks easily occur at the connection part. Further, in the technique of applying a resin composition containing acrylonitrile butadiene rubber or acrylic rubber to a metal foil, if the compounding ratio of acrylonitrile butadiene rubber or acrylic rubber is increased to form a low elastic resin layer, the adhesiveness to the coated surface becomes The remainder is poor workability when handling the metal foil.
The metal foil tends to curl due to the shrinkage of the applied resin, which further deteriorates the handleability. The problem to be solved by the present invention is to prevent adhesiveness from remaining on the coated surface of a metal foil coated with a low-elasticity resin composition, curl of the metal foil is also suppressed, and a surface-mounted printed wiring board It is to manufacture a metal foil-clad laminate suitable as a material with good workability.
Another object is to provide a metal foil suitable for such production.

[0004]

The method for producing a metal foil-clad laminate according to the present invention comprises a sheet-shaped base material impregnated with a thermosetting resin and dried to obtain a prepreg, and a metal foil is formed on the surface of the layer of the prepreg. In the production of a metal foil-clad laminate which is placed and heated and pressed, the first component comprising the following components (1) to (4)
Of the resin composition is applied to the roughened surface of the metal foil, and the second resin composition, which has no tackiness in the dry state and has a higher elastic modulus than the first resin composition, is applied to the application surface and dried. .
Then, the coated surface of the metal foil is overlaid on the layer of the prepreg and the heat and pressure molding is performed, and the thickness of 20 μm is directly under the metal foil.
A low-elasticity resin layer made of a first resin composition having an elastic modulus of 10 kgf / mm ² or less and a m or more is provided. (1) Acrylic rubber (2) Epoxy resin (3) Phenolic resin (4) Inorganic filler The second resin composition comprises, for example, the same components as the first resin composition, and the second resin composition The content of the inorganic filler is higher than that of the first resin composition. The second resin composition may be composed of the same components as the first resin composition, and the second resin composition may have an epoxy resin content higher than that of the first resin composition. . The metal foil for a metal foil-clad laminate according to the present invention has a thickness of 20 μm or more and an elastic modulus after curing of 10 Kgf / mm ^{2 on} the roughened surface of the metal foil.
A low-elasticity resin layer of the first resin composition comprising the components (1) to (4) described below, and a second resin composition that further eliminates tackiness in a dry state on the surface of the low-elasticity resin layer. A surface resin layer (higher elasticity than the low elasticity resin layer) is formed on the object.

[0005]

FUNCTION The component (2) of the first resin composition functions to cure the component (1), and the components (3) and (4) function to reduce the tackiness after coating. Furthermore, since the surface resin layer made of the second resin composition, which loses its tackiness in a dry state, is formed on the low-elasticity resin layer made of the first resin composition, the metal foils are superposed on each other. It is possible to prevent blocking when left to stand. Further, since the elastic modulus of the surface resin layer is higher than that of the low elastic resin layer, curling of the metal foil can be suppressed and workability is improved. By specifying the thickness and elastic modulus of the low-elasticity resin layer formed directly below the metal foil of the molded metal foil-clad laminate as described above, the stress applied to the solder connection part of the surface-mounted component is reduced by the low-elasticity resin layer. It can be absorbed and alleviated, and the generation of cracks in the solder connection portion can be suppressed.

[0006]

【Example】

Examples 1 to 8 and Comparative Examples 1 to 2 As the first resin composition, the following (1) to (4) were mixed at the compounding ratio (parts by weight) shown in Table 1 to obtain a low elasticity of 25% by weight of solid content. A resin solution was prepared. As the solvent, a mixed solvent of MEK / toluene = 80/20 (weight ratio) and a high boiling point solvent (cellosolve acetate, DMF, etc.) was used. The reason for using the high boiling point solvent is to improve the workability of coating on the metal foil. (1) Acrylic rubber (Nippon Zeon “LX-852”) (2) Bisphenol A type epoxy resin (Okaka Shell Epoxy “Ep-828”) (3) Alkylphenol resin (Mitsui Toatsu Chemicals “Permanol 100” , Alkyl group: isopropyl group) (4) Aluminum hydroxide (“H-42ST” manufactured by Showa Denko) As the second resin composition, the above (1) to (4) are shown in Table 1.
A highly elastic resin solution was prepared by mixing in the mixing ratio (parts by weight) shown in. The solvent was the same as the low elasticity resin solution.

First, each of the low-elasticity resin solutions described above was applied to a copper foil having a thickness of 35 μm by an applicator so as to have a thickness shown in Table 1 and dried. Next, each of the above-mentioned high-elasticity resin solutions was applied to the application surface and dried to prepare a copper foil provided with a high-elasticity surface resin layer on the low-elasticity resin layer. In addition, glass fiber woven fabric (“WFA-18” manufactured by Nitto Boseki, unit weight 205 g / m ² )
Then, bisphenol A type epoxy resin varnish was impregnated and dried to prepare a prepreg (A) having a resin amount of 40% by weight.
Non-woven glass ("EPM-4050" made by Cumulus, unit weight 5
0 g / m ² ), bisphenol A type epoxy resin varnish containing inorganic filler (resin / filler weight ratio = 100/50)
Was impregnated and dried to prepare a prepreg (B) having a resin amount of 84% by weight. 6 plies of prepreg (B) are stacked, 1 ply of prepreg (A) is arranged on each side of the prepreg (B), and the above-mentioned copper foil with various resin layers is placed on the outermost surface with the resin layer surface facing inward. A 1.6 mm thick composite type copper-clad laminate was obtained.

[0008]

[Table 1]

Table 2 shows the results of evaluation of the presence or absence of blocking and the presence or absence of curling of the copper foils of Examples 1 to 8 and Comparative Examples 1 and 2 and the solder connection reliability. The evaluation method is as follows. Solder crack: 3216R (ceramic chip resistor) was surface-mounted on a printed wiring board obtained by processing the above-mentioned copper-clad laminate according to a conventional method, and the rate of occurrence of wire breakage at the solder connection portion was measured after 1000 cycles of -30 ° C / 120 ° C cooling and heating. To do. Copper foil blocking: 10 pieces of copper foil with a resin layer cut into 5 cm x 5 cm are stacked, and a load of 10 kg is applied, and the foil is allowed to stand for 24 hours at a temperature of 23 ° C and a humidity of 60%. Check the sticking. Copper foil curl: A copper foil with a resin layer cut into 1 m x 1 m is allowed to stand for 10 days at a temperature of 23 ° C and a humidity of 60% to check the curl of the copper foil.

[0010]

[Table 2]

[0011]

As described above, according to the method of the present invention, it is possible to suppress the tackiness and curl of the metal foil having the low-elasticity resin layer and improve the workability of the metal foil-clad laminate production. There is an effect. Further, the metal foil-clad laminate produced by the method according to the present invention is suitable as a surface-mounting printed wiring board material, and secures the solder connection reliability of the surface-mounting low thermal expansion component even during repeated thermal cycles. can do.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location B32B 17/04 B32B 17/04 A 31/20 7148-4F 31/20

Claims (4)

[Claims] 1. A method for producing a metal foil-clad laminate, comprising impregnating and drying a sheet-shaped base material with a thermosetting resin to obtain a prepreg, placing a metal foil on the surface of the layer of the prepreg, and heat-pressing. , A first resin composition comprising the following components (1) to (4) is applied to the roughened surface of the metal foil, and when it is dry, it loses its tackiness and has a higher elastic modulus than the first resin composition. The resin composition of No. ² is applied to the coated surface and dried, the coated surface is overlaid on a layer of a prepreg and the heat and pressure molding is performed, and the elastic modulus of 10 Kgf / mm ² is directly under the metal foil with a thickness of 20 μm or more. A method for producing a metal foil-clad laminate, comprising providing a low-elasticity resin layer comprising the following first resin composition. (1) Acrylic rubber (2) Epoxy resin (3) Phenolic resin (4) Inorganic filler 2. The second resin composition comprises the same components as the first resin composition, and the content of the inorganic filler in the second resin composition is higher than that of the first resin composition. The method for producing a metal foil-clad laminate according to claim 1. 3. The second resin composition comprises the same components as the first resin composition, and the epoxy resin content of the second resin composition is higher than that of the first resin composition. The method for producing a metal foil-clad laminate according to claim 1. 4. A roughened surface of a metal foil having a thickness of 20 μm or more and an elastic modulus after curing of 10 Kgf / mm ² or less (1) to
The low-elasticity resin layer of the first resin composition comprising the component (4), and the surface resin layer of the second resin composition (the low-elasticity layer, which loses its tackiness on the surface of the low-elasticity resin layer in a dry state). A metal foil for a metal foil-clad laminate, which has a higher elasticity than an elastic resin layer). (1) Acrylic rubber (2) Epoxy resin (3) Phenolic resin (4) Inorganic filler