JP3107278B2 - Manufacturing method of metal foil-clad laminate and metal foil for metal foil-clad laminate - 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 surface-mounted printed wiring board and a metal foil.

[0002]

2. Description of the Related Art In a printed wiring board for surface mounting, the thermal expansion coefficient of a ceramic chip resistor to be surface mounted is 7 ppm /.
° C, the thermal expansion coefficient of the printed wiring board substrate (made of a metal foil-clad laminate) is 14-22p
pm / ° C. Therefore, when the thermal 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 enter the solder connection portion and lead 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 in which a thermosetting resin contains an inorganic filler in a laminated board obtained by placing a metal foil on the surface of a prepreg layer obtained by impregnating and drying a sheet-shaped base material with a thermosetting resin and heating and pressing. There is. In addition, in order to alleviate the stress applied to the solder connection portion, it has been studied to arrange a low elastic resin layer below the metal foil. For example, there is a method in which a resin composition containing acrylonitrile-butadiene rubber or acrylic rubber is applied to a metal foil in advance, this is placed on a prepreg layer, and a metal foil-clad laminate is manufactured by heat and pressure molding.

[0003]

However, in the above-described technique of incorporating an inorganic filler, the thermal expansion coefficient of the laminate is not so low as to be expected, and the elastic modulus of the laminate is high. Cracks are easily formed in the connection part. In addition, in the technology of applying a resin composition containing acrylonitrile butadiene rubber or acrylic rubber to a metal foil, if the mixing ratio of acrylonitrile butadiene rubber or acrylic rubber is increased to form a low-elastic resin layer, the adhesiveness on the application surface is reduced. In addition, workability when handling the metal foil is deteriorated.
The metal foil is easily curled due to the shrinkage of the applied resin, and the handleability is further deteriorated. The problem to be solved by the present invention is to prevent the adhesiveness of the metal foil coated with the low-elasticity resin composition from remaining on the coating surface, suppress the curl of the metal foil, and improve the printed wiring board for surface mounting. An object of the present invention 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]

According to the method of manufacturing a metal foil-clad laminate according to the present invention, a prepreg is obtained by impregnating and drying a sheet-like substrate with a thermosetting resin, and the surface of the prepreg layer is coated with a metal foil. In the production of a metal foil-clad laminate in which a sheet is placed and heated and pressed, the first component comprising the following components (1) to (4)
Is applied to the roughened surface of the metal foil, and the second resin composition which is less sticky and has a higher elastic modulus than the first resin composition in a dry state is applied to the coated surface and dried. .
Then, the application surface of the metal foil is superimposed on the prepreg layer, and the heating and press-forming is performed.
a low-elasticity resin layer comprising a first resin composition having a modulus of not less than m and not more than 10 kgf / mm ² . (1) Acrylic rubber (2) Epoxy resin (3) Phenolic resin (4) Inorganic filler The second resin composition is composed of, for example, the same components as the first resin composition, and is a second resin composition. The content of the inorganic filler is larger than that of the first resin composition. In addition, the second resin composition may be composed of the same components as the first resin composition, and the epoxy resin content of the second resin composition may be larger 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 a cured elastic modulus of 10 kgf / mm ^{2 on} the roughened surface of the metal foil.
A low elastic resin layer of the first resin composition comprising the above components (1) to (4), and a second resin composition which further loses tackiness in a dry state on the surface of the low elastic resin layer A surface resin layer (higher elasticity than the low elasticity resin layer) of the product is formed.

[0005]

The component (2) of the first resin composition has a function of curing the component (1), and the components (3) and (4) have a function of reducing the tackiness after coating. Furthermore, since the surface resin layer made of the second resin composition, which has no stickiness in a dry state, is formed on the low elastic resin layer made of the first resin composition, the metal foils are overlapped. Blocking when left unattended can be prevented. Further, since the elastic modulus of the surface resin layer is larger than the elastic modulus 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 elastic 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 mount component is reduced by the low elastic resin layer. It absorbs and relaxes, and the occurrence 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 and the low elasticity of the solid content was 25% by weight. 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 application to the metal foil. (1) Acrylic rubber (“LX-852” manufactured by Zeon Corporation) (2) Bisphenol A type epoxy resin (“Ep-828” manufactured by Yuka Shell Epoxy) (3) Alkylphenol resin (“Permanol 100” manufactured by Mitsui Toatsu Chemicals) ), 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.
To obtain a highly elastic resin solution. The solvent was the same as the low elastic resin solution.

First, each of the above low elastic resin solutions was applied to a copper foil having a thickness of 35 μm with an applicator so as to have a thickness shown in Table 1 and dried. Next, the above-mentioned high elastic resin solutions were applied to the application surface and dried to prepare a copper foil having a high elastic surface resin layer provided on a low elastic resin layer. In addition, glass fiber woven fabric (Nittobo “WFA-18”, unit weight 205 g / m ² )
Then, a prepreg (A) having a resin amount of 40% by weight was prepared by impregnating and drying a bisphenol A type epoxy resin varnish.
Glass non-woven fabric (cumulus EPM-4050, unit weight 5
0 g / m ² ), an inorganic filler-containing bisphenol A epoxy resin varnish (weight ratio of resin / filler = 100/50)
Was impregnated and dried to prepare a prepreg (B) having a resin amount of 84% by weight. The prepreg (B) is piled up in 6 plies, the prepreg (A) is placed on each side by 1 ply, and the above-mentioned copper foil with various resin layers is placed on the outermost surface with the resin layer surface inside, and is heated and pressed. A 1.6 mm thick composite type copper-clad laminate was obtained.

[0008]

[Table 1]

Table 2 shows the results of the evaluation of the copper foils of Examples 1 to 8 and Comparative Examples 1 and 2 for the presence / absence of blocking and the presence / absence of curl and the reliability of solder connection. 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 breaking rate of the solder joint was measured after 1000 cycles of cold / heat cycles of -30 ° C / 120 ° C. I do. Copper foil blocking: Ten pieces of copper foil with a resin layer cut to 5 cm × 5 cm are stacked, and while applying a load of 10 kg, the copper foils are left standing at a temperature of 23 ° C. and a humidity of 60% for 24 hours. Check the sticking. Copper foil curl: A copper foil with a resin layer cut to 1 m × 1 m is left 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, the workability of manufacturing a metal foil-clad laminate can be improved by suppressing the adhesiveness and curl of a metal foil having a low elasticity resin layer formed thereon. This has the effect. Further, the metal foil-clad laminate manufactured by the method according to the present invention is suitable as a material for a surface-mounted printed wiring board, and ensures the solder connection reliability of a low-thermal-expansion component surface-mounted even in repeated thermal cycles. can do.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification code FI B32B 17/04 B32B 17/04 A 31/20 31/20 H05K 1/03 610 H05K 1/03 610L (58) Fields surveyed ( Int.Cl. ⁷ , DB name) B32B 1/00-35/00 H05K 1/03

Claims (4)

(57) [Claims] A prepreg is obtained by impregnating and drying a thermosetting resin on a sheet-like base material, and a metal foil is placed on the surface of the prepreg layer. A first resin composition comprising the following components (1) to (4) is applied to a roughened surface of a metal foil, and the first resin composition loses tackiness in a dry state and has a higher elastic modulus than the first resin composition. 2. The resin composition of No. ² was applied to the coated surface and dried, and the coated surface was superimposed on a prepreg layer and subjected to the heat and pressure molding, and a thickness of 20 μm or more and a modulus of elasticity of 10 kgf / mm ² immediately below the metal foil. A method for producing a metal foil-clad laminate, comprising providing a low elastic resin layer comprising the following first resin composition. (1) Acrylic rubber (2) Epoxy resin (3) Phenol 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 larger than that of the first resin composition. The method for producing a metal foil-clad laminate according to claim 1. 3. The resin composition according to claim 2, wherein the second resin composition comprises the same components as the first resin composition, and the epoxy resin content of the second resin composition is larger than that of the first resin composition. A method for producing a metal foil-clad laminate according to claim 1. 4. The following (1) to (4), in which the elastic modulus after curing becomes 10 kgf / mm ² or less when the thickness is 20 μm or more on the roughened surface of the metal foil.
A low-elasticity resin layer of the first resin composition comprising the component (4); and a surface resin layer of the second resin composition which loses tackiness in a dry state on the surface of the low-elasticity resin layer. A metal foil for a metal foil-clad laminate, wherein the metal foil has a higher elasticity than the elastic resin layer). (1) Acrylic rubber (2) Epoxy resin (3) Phenol resin (4) Inorganic filler