JPH11238965A - Manufacture of multilayered printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the adhesive property of prepreg and an inner-layer substrate by rouhening the surface of the inner-layer circuit board in contact with the prepreg by chemical when the inner-layer circuit board wherein a circuit pattern is formed is laminated and bonded through the prepreg. SOLUTION: An inner-layer circuit board is formed as follows: varnish such as phenol resin, epoxy resin and unsaturated polyester resin is impregnated into fiber basic material and dried, and prepreg is obtained; the specified number of the prepregs are laminated; metal foils are overlapped, heated and compressed and the metal-foil laminated plate is formed; and the plate is processed into the circuit pattern. At this time, the surface of the inner-layer circuit board in contact with the prepreg undergoes chemical roughening by using the chemical such as potassium permanganate, concentrated sulfuric acid or chromic acid. Thus, the adhesive property of the prepreg and the inner-layer substrate can be improved at the low cost and the high productivity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multilayer printed wiring board used for electronic equipment and the like.

[0002]

2. Description of the Related Art Along with the recent miniaturization of electronic devices, printed wiring boards used therein are required to be highly integrated and multilayered. The multilayer printed wiring board is manufactured by integrally molding a plurality of inner circuit boards, a prepreg, and an outer copper foil.

[0003]

In such a multilayer printed wiring board, the adhesion between the prepreg and the inner circuit board has become a problem. The inner layer circuit board is formed by etching a double-sided metal-clad laminate, and the etched metal foil has a roughened surface. Is transferred. The adhesiveness between the prepreg and the inner layer circuit board is achieved by transferring the uneven shape of the metal foil used for the inner layer circuit board to the substrate surface, and the unevenness serves as an anchor. Also, the circuit pattern composed of prepreg and metal foil is obtained by subjecting the surface of the circuit pattern to a known oxidation treatment or oxidation-reduction treatment.
Enhancement of adhesion has been performed. Here, due to the demand for higher density, the thickness of the metal foil used for the inner layer circuit board has become thinner, and accordingly, there has been a tendency to use a metal foil with a smaller unevenness, and the unevenness transferred to the substrate has also become smaller. The adhesiveness of the inner circuit board is reduced. An object of the present invention is to improve the adhesiveness between a prepreg and an inner layer substrate at low cost and with high productivity.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a method of manufacturing a multilayer printed wiring board in which an inner circuit board on which a circuit pattern is formed is laminated and bonded via a prepreg. A method for manufacturing a multilayer printed wiring board. Further, the present invention provides a ten-point average roughness (Rz) of the inner circuit board surface.
Is preferably not less than 5 μm.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Chemicals for roughening an inner circuit board by chemical treatment include potassium permanganate, concentrated sulfuric acid, chromic acid, and the like, and include buffing and mechanical roughening with other abrasives. You may use together.

In the present invention, the ten-point average roughness (Rz) of the inner layer circuit board surface is preferably 5 μm or more, and more preferably 1 μm or more.
It is preferably at least 0 μm. Surface roughness is JIS
B601, the ten-point average roughness (R
z) is based on it. As the resin used for the inner layer circuit board or prepreg used in the present invention, phenol resin, epoxy resin, unsaturated polyester resin, polyimide resin, polybutadiene resin, polyamide resin, polysulfone resin, polyphenylene sulfide resin, polyphenylene ether resin, poly Butylene terephthalate resin,
A single, modified, or a mixture of a fluorine resin and the like can be given.

The inner-layer circuit board is prepared by impregnating the resin varnish into a fiber base material and drying to form a prepreg, stacking a predetermined number of the prepregs, stacking a metal foil, for example, a copper foil, and applying heat and pressure to produce a metal foil-clad laminate. , Obtained by circuit processing. Generally, a copper foil is composed of a glossy surface and a roughened surface, and the surface roughness of the roughened surface varies depending on the copper foil thickness and application, but generally a ten-point average roughness (Rz) of 2 to 15 μm is used. You.

As the fiber base material, woven fabric, nonwoven fabric, mat of glass fiber, woven fabric, nonwoven fabric, mat of aromatic polyamide fiber and the like are used. The metal foil-clad laminate is subjected to circuit processing, and then the surface of the substrate is roughened. As the roughening treatment, the surface may be mechanically roughened with a buff or another abrasive and then treated with a chemical, or may be directly roughened with a chemical. As the chemical, the above-mentioned potassium permanganate, concentrated sulfuric acid, chromic acid, or the like is used to chemically roughen.
The surface of the circuit pattern made of metal foil in contact with the prepreg is subjected to a known oxidation treatment or oxidation-reduction treatment. As the prepreg for bonding, it is preferable to use the same prepreg used for manufacturing the inner layer circuit board. This is because the same material is used as the whole material when a multilayer printed wiring board is used, so that properties such as thermal expansion and contraction can be made uniform, and cost increases due to the use of various types of materials can be eliminated from the manufacturing perspective. .

[0009] The lamination molding can be carried out under conventionally employed conditions, similarly to the ordinary lamination molding of a multilayer board.
C., pressure 0.5 to 20 MPa, and heating time 10 to 120 minutes. Appropriate conditions are selected according to the resin composition of the adhesive prepreg.

[0010]

(Example 1) 50 parts by weight of bisphenol A novolak type epoxy resin (using Epicron N-868 (trade name) manufactured by Dainippon Ink and Chemicals, Inc.)
Bisphenol A novolak resin (using YLH-129 (trade name) manufactured by Yuka Shell Epoxy Co., Ltd.) 4
0 parts by weight, brominated bisphenol A type epoxy resin (ESB-400 (trade name) manufactured by Sumitomo Chemical Co., Ltd.)
50 parts by weight and 1 part by weight of 1-cyanoethyl-2-phenylimidazole were added to 90 parts of methyl ethyl ketone.
The varnish was dissolved in parts by weight. 100μ of this varnish
m woven glass fabric (MIL part number 2116 type) and dried in a dryer at 150 ° C. for 4 minutes to obtain a B-stage prepreg. The obtained four prepregs are stacked, and a thickness of 35 μm (roughened surface roughness Rz =
9.4 μm) copper foil, pressure 2 MPa, temperature 170
The mixture was heated and pressed at 100 ° C. for 100 minutes to obtain a double-sided copper-clad laminate. This double-sided copper-clad laminate was subjected to a predetermined pattern etching to obtain an inner layer circuit board. The irregularities on the surface of the inner circuit board are represented by Rz =
It was 9.4 μm. The roughened surface of the copper foil and the surface of the inner layer circuit board are manufactured by Tokyo Seimitsu Co., Ltd.
rfcom). Next, the surface of the inner layer circuit board subjected to the pattern etching is coated with potassium permanganate (Shipley (Sh
iply) using CIRCUPOSIT ROMOTER 3308)
The treatment was performed at 5 ° C. for 5 minutes. The surface roughness of the inner circuit board is R
z = 10.9 μm. Thereafter, a predetermined oxidation-reduction treatment was performed on the copper foil pattern as a conductor. One prepreg and 18 μm copper foil were placed on the upper and lower sides of the inner circuit board thus obtained, respectively, and heated and pressed at a temperature of 175 ° C. for 90 minutes to obtain a multilayer board A.

Example 2 In the same manner as in Example 1, a double-sided copper-clad laminate using a copper foil having a thickness of 35 μm and a roughened surface having a surface roughness of Rz = 3.9 μm was prepared. The laminated laminate was subjected to a predetermined pattern etching to obtain an inner circuit board.
The surface roughness of the inner circuit board is Rz = 3.9 μm, and the surface roughness of the inner circuit board after the roughening treatment is Rz = 6.2.
μm. Example 1 using this inner layer circuit board
In the same manner as in the above, a multilayer board B was obtained.

Comparative Example 1 A multilayer board C was obtained in the same manner as in Example 1 except that the roughening treatment was not performed.

Comparative Example 2 A multilayer board D was obtained in the same manner as in Example 2 except that the roughening treatment was not performed.

The multilayer boards obtained in Examples 1 and 2 and Comparative Examples 1 and 2 were evaluated for moisture absorption solder heat resistance and peel strength between a prepreg and a substrate. The results are shown in Table 1. .

The heat resistance of the solder after absorption is 121 ° C. and 2 atm.
Immerse in solder at 60 ° C for 20 seconds, and evaluate the appearance by visual inspection. Those without blisters are OK, those with blisters are NG.
And The adhesion between the prepreg and the inner layer circuit board was determined by cutting out a 100 × 25 mm test piece from the multilayer board and forming an outermost layer of copper foil on one side and an insulating layer made of one prepreg into a 10 mm piece.
Peeling off the strip with the width of the strip remaining, peeling off the end of the strip, grasping the tip with the gripper of the testing machine, and peeling off at the pulling speed of 50 mm / min in the direction perpendicular to the surface of the test piece. The required load was measured to determine the peel strength.

[0016]

[Table 1] Item Example 1 Example 2 Comparative example 1 Comparative example 2 Multilayer board A Multilayer board B Multilayer board C Multilayer board D Substrate surface roughness (Rz, μm) 9.4 3.9 9.4 3.9 (Roughening treatment Before) Substrate surface roughness (Rz, μm) 10.9 6.2-- (After roughening treatment) Peel strength (KN / m) 0.81 0.63 0.73 0.49 Heat resistance State OK OK OK OK PCT-2h OK OK OK NG PCT-3h OK NG OK NG PCT-4h OK NG NG NG

From Table 1, it can be seen that Examples 1 and 2 in which the substrate surface of the present invention was treated with chemicals had higher peeling strengths than Comparative Examples 1 and 2 in which the chemical treatment was not performed, and therefore, the heat resistance of the moisture absorption solder. Is significantly improved. According to the present invention, the adhesiveness between the prepreg and the surface of the inner layer circuit board is increased particularly when a thin copper foil having a small surface roughness on the roughened surface of the copper foil is used.

[0018]

According to the method of manufacturing a multilayer printed wiring board of the present invention, the adhesion between the prepreg and the substrate surface can be improved by using conventional equipment and at low cost by roughening the substrate surface.

Claims (2)

[Claims] 1. A method for manufacturing a multilayer printed wiring board in which an inner circuit board on which a circuit pattern is formed is laminated and bonded via a prepreg, wherein the surface of the inner circuit board in contact with the prepreg is roughened by a chemical. Manufacturing method of wiring board. 2. Ten-point average roughness (Rz) of the surface of the inner circuit board
2. The method for producing a multilayer printed wiring board according to claim 1, wherein the thickness is 5 μm or more.