JP2000077847A - Manufacture of multilayered printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the adhesive property of an inner board and an insulating layer by removing a metal foil and roughening the surface of the exposed board after the etching of a metal-foil applied laminated board and the formation of an inner circuit pattern. SOLUTION: Phenol resin, epoxy resin, unsaturated polyester resin, polyimide resin, polybutadiene resin and polyamide resin and the like are provided as the matrix resin as the single or converted material or the mixed material. These resin vanish is impregnated and dried in the raw fiber material such as woven fabric and unwoven fabric and mat. Thus, the metal-foil applied and laminated board is manufactured by combining these layer. This board is etched to form an inner-layer circuit pattern. Thereafter, the metal foil is removed. The exposed surface of the board is roughened by using potassium permanganate, concentrated sulfric acid, chromic acid and the like.

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.

[0002]

2. Description of the Related Art A multilayer printed wiring board is a printed wiring board having three or more conductor layers including a surface conductor layer.
Therefore, the printed wiring board has a conductor pattern, that is, an inner circuit pattern also in the inner layer.

There are a lamination method and a build-up method as a method of manufacturing a multilayer printed wiring board.

In the lamination method, a metal-laminated laminated board is etched to form an inner-layer circuit pattern, and a metal foil is used as a constituent material. An adhesive sheet is inserted between the constituent materials and heated. This is a method of applying pressure and bonding and integrating. When a metal foil is laminated on both sides of one inner layer circuit board having an inner layer circuit pattern on both sides, a four-layer printed wiring board is obtained.
By increasing the number of inner layer circuit boards, a more multilayer printed wiring board can be obtained.

[0005] The build-up method is a method in which a conductor layer and an insulating layer are sequentially stacked from an inner layer to a surface layer. The metal-clad laminate is etched to form an inner layer circuit pattern, and an adhesive sheet is inserted over it (instead of inserting the adhesive sheet, a liquid adhesive may be applied). The metal foil is heated and pressurized to bond and integrate, and the metal foil is etched to form a circuit pattern. A four-layer printed wiring board is obtained by forming an inner circuit pattern on both sides using a double-sided metal-clad laminate, bonding and integrating metal foils on both sides, and then etching to form a circuit pattern on the surface. Can be By using the circuit pattern on the surface formed as described above as an inner layer circuit pattern and repeating the same steps as described below, further multilayering can be achieved. Normally, an insulating layer and a conductor layer are stacked on both sides to form a multilayer, but there is also a case where one layer is stacked on one side to form a multilayer.

Regardless of which method is used, in a multilayer printed wiring board, it is important for the reliability of the product that the insulating layer formed by curing the adhesive sheet is firmly adhered. Then, there is known a method of forming a fine unevenness by roughening the bonding surface in order to strengthen the bonding.

On the other hand, in the case of ordinary metal foil, one surface is a smooth surface called a shiny surface or a glossy surface, and the other surface is a surface having fine irregularities called a matte surface or a roughened surface. For example, copper foil having a surface roughness of a roughened surface (ten-point average roughness defined by JIS B 0601, hereinafter referred to as Rz) of 2 to 15 μm is commercially available, and a metal-clad laminate is provided. (Copper-clad laminates).

[0008] The metal-clad laminate is laminated with a predetermined number of prepregs obtained by impregnating and drying a thermosetting resin varnish in a fibrous base material, and then laminating a metal foil so that the roughened surface is in contact with the prepreg. It is manufactured by heating and pressing. The unevenness of the roughened surface of the metal foil is transferred to the substrate surface of the inner layer circuit board of the multilayer printed wiring board, and the metal foil is roughened on the exposed substrate surface after the metal foil is removed by etching. The same shape irregularities as the surface are formed. It is known that the presence of such irregularities provides a mechanical effect, such as anchoring, that is, an anchor effect, thereby improving the adhesiveness. Therefore, in the production of a multilayer printed wiring board, conventionally, a metal-clad laminate is etched to form an inner circuit pattern, and then only the surface of the conductor layer of the inner circuit pattern is roughened.

[0009]

In recent years, printed wiring boards have also been required to be thinner and higher in density, and accordingly, metal spiders have been used. As the metal foil becomes thinner, the roughness of the roughened surface must be reduced. For this reason, the unevenness transferred to the substrate surface is also reduced, resulting in a new problem that the adhesiveness between the insulating layer and the substrate is reduced. Also,
Higher adhesiveness is required for multilayer printed wiring boards used in harsh environments of high temperature and high humidity. The present invention
An object of the present invention is to provide a method for manufacturing a multilayer printed wiring board having excellent adhesion between an inner layer substrate and an insulating layer.

[0010]

According to the present invention, there is provided a process of forming an inner layer circuit pattern by etching, and thereafter roughening an exposed substrate surface (hereinafter referred to as a substrate surface) by removing a metal foil by etching. And a method for manufacturing a multilayer printed wiring board.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As a metal-clad laminate used for forming an inner-layer circuit pattern first, a conventionally known metal-clad laminate can be used, and there is no particular limitation. For example, a phenol resin, an epoxy resin, an unsaturated polyester resin, a polyimide resin, a polybutadiene resin, a polyamide resin, a polysulfone resin, a polyphenylene sulfide resin, a polyphenylene oxide resin, a polybutylene terephthalate resin, a fluorinated resin, etc. As a resin, a metal-clad laminate manufactured by laminating and integrating a metal foil on a prepreg obtained by impregnating and drying a fiber substrate with these resin varnishes is exemplified. 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, but not limited thereto. Above all, from the viewpoints of various characteristics required for printed wiring boards, ease of manufacture, cost, versatility, etc., copper-clad laminates using copper foil as metal foil, for example, glass cloth base epoxy resin Copper-clad laminates can be mentioned as preferred.

The etching method for forming the inner layer circuit pattern on the metal-clad laminate can be a conventionally known etching method, and is not particularly limited. That is, for example, when a copper-clad laminate is used, a dry film is laminated on the copper-clad laminate, exposed through a mask film having a predetermined pattern, and then subjected to a development process. Unnecessary copper foil is etched by dipping in a hydrochloric acid solution.

After forming the inner layer circuit pattern, the substrate surface is roughened. As a method for roughening the substrate surface, any of chemical roughening using a chemical agent and mechanical roughening can be applied. These may be used in combination. Examples of the chemical agent used for chemical roughening include those mainly containing potassium permanganate, concentrated sulfuric acid, chromic acid and the like. Examples of the mechanical roughening include a buff polishing method and a polishing method using an abrasive.

The substrate surface is preferably roughened so that Rz is 5 to 20 μm, more preferably 10 to 15 μm. If Rz is less than 5 μm, the anchor effect due to the unevenness becomes insufficient, and the adhesiveness between the substrate surface and the insulating layer tends to decrease. Also, R
If z exceeds 20 μm, the unevenness is too large to fill the dent, and the adhesion between the substrate surface and the insulating layer tends to decrease.

After the substrate surface is roughened, the surface of the conductor layer of the inner circuit pattern is roughened. However, when the substrate surface is roughened by mechanical roughening, the surface of the conductor layer of the inner circuit pattern is also roughened at the same time, so that this step may not be necessary in some cases. A method for roughening the surface of the conductor layer of the inner circuit pattern can be a conventionally known roughening method, and is not particularly limited. For example, in an inner layer circuit board using a copper-clad laminate, a needle-like copper oxide layer is formed on the surface of the conductor layer by subjecting the surface of the conductor layer to an oxidation treatment using an alkaline solution of sodium hypochlorite. By forming, it can be roughened. The next step may be performed as it is roughened by the oxidation treatment, and the formed copper oxide layer is reduced to copper while maintaining the roughened shape with a reducing agent such as formaldehyde or dimethylamine borane. You may enter the next step.

After roughening the substrate surface and the conductor layer surface of the inner circuit board, the metal foil is bonded and integrated using an adhesive.

As the adhesive, conventionally known thermosetting resins, photosensitive resins and the like are used, and there is no particular limitation. Examples of the thermosetting resin include an epoxy resin, an acrylic resin, a melamine resin, and a urea resin. As the photosensitive resin, acrylic resin, tripropylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, polyethylene glycol diacrylate, epoxy acrylate,
A phenol novolak epoxy resin partially acrylated, a cresol novolak resin partially acrylated, and the like can be given.

An adhesive varnish is prepared by blending the necessary components such as the resin component and the curing agent. Then, using the adhesive varnish as it is, a known method such as a dipping method, a curtain coating method and a roll coating method is applied to the inner circuit board and dried, and a metal foil is overlaid and heated and pressed. Alternatively, an adhesive film or sheet may be prepared by applying an adhesive varnish on a carrier film and drying to a B stage, and this adhesive sheet or film may be used. In this case, it is preferable that a component having a film forming ability, for example, a high-molecular-weight epoxy polymer is blended in order to prevent troubles such as cracking and chipping during the steps of transporting, cutting and laminating. . It is also possible to use a metal foil as the carrier film to form an adhesive film or sheet with a metal foil, and to bond and integrate it with the inner layer circuit board while keeping the metal foil. Further, a prepreg obtained by impregnating and drying an adhesive varnish on a fiber base material can also be used. In the lamination method, prepreg is frequently used.

A method and conditions for laminating a metal foil on the inner circuit board via an adhesive, curing the adhesive by heating and pressurizing, and integrating them can be according to conventionally known methods and conditions. There is no particular limitation. In the lamination method, thereafter, etching is performed to form a circuit pattern of the outermost layer, and a multilayer printed wiring board is obtained. Also,
In the build-up method, after performing etching, if necessary, the steps below the roughening of the substrate surface are repeated to form a multilayer.

[0020]

EXAMPLES Example 1 Brominated epoxy resin (using Epicoat 5040B80 (trade name) manufactured by Yuka Shell Epoxy Co., Ltd.) 90
Part by weight, cresol novolak type epoxy resin (using ESCN1273 (trade name) manufactured by Dow Chemical Company) 10
A varnish was prepared by dissolving 1.5 parts by weight of dicyandiamide and 0.05 part by weight of 2-ethyl-4-methylimidazole in 30 parts by weight of methyl ethyl ketone. This varnish was coated with a 100 μm thick glass woven fabric (MIL part number 2116).
Type) and dried at 150 ° C. for 4 minutes to prepare a prepreg.

Two prepared prepregs were stacked, and a thickness of 35 μm (a surface roughness Rz of the copper foil roughened surface Rz = 9.4) was formed on both sides thereof.
μm) of copper foil, with the roughened surface of the copper foil in contact with the prepreg, at a temperature of 170 ° C. under a pressure of 2 MPa.
It was heated and pressed for 0 minutes to produce a double-sided copper-clad laminate. In addition,
Rz of the copper-roughened surface is 3.9 μm (measured using Surfcom (trade name), manufactured by Tokyo Seimitsu Co., Ltd., and so on)
Met.

The produced double-sided copper-clad laminate was etched to produce an inner circuit board. In the manufactured inner layer circuit board, Rz of the substrate surface of the inner layer circuit board exposed by etching the copper foil was 3.9 μm.

Next, the prepared inner-layer circuit board was heated to a temperature of 85 ° C.
Potassium permanganate-based roughening solution (CIRCUPOSIT PROMOTER 330 manufactured by Spray Co., Ltd.)
8 (product name)) for 10 minutes to roughen the substrate surface. Then, sodium hydroxide 15 g / l and sodium hypochlorite 70 heated to a temperature of 85 ° C.
The surface of the conductor pattern was roughened by immersing in a g / l aqueous solution for 3 minutes. After this, when the copper foil was etched and the Rz of the exposed substrate surface was measured,
It was 10.9 μm.

100 parts by weight of a high molecular weight epoxy polymer having a molecular weight of 500,000 (with no trade name, manufactured by Hitachi Chemical Co., Ltd.) and a bisphenol A type epoxy resin having an epoxy equivalent of 171.5 (Dai Nippon Ink Chemical Industry Co., Ltd.) Company-made, using Epicron 850CRP (trade name)) 24
Parts by weight and 15 parts by weight of isocyanate were dissolved in 2 parts by weight of N, N-dimethylacetamide to prepare an adhesive varnish having a viscosity of 8 Pa · s. This adhesive varnish was applied to a copper foil having a thickness of 18 μm using a roll coater so that the thickness of the adhesive layer after drying was 100 μm, and the temperature was 100 μm.
The film was heated at a temperature of 150 ° C. for 10 minutes and further at a temperature of 150 ° C. for 10 minutes to produce an adhesive adhesive film.

On both sides of the inner circuit board prepared above, the copper-foiled adhesive film was laminated so that the adhesive layer of the copper-foiled adhesive film was in contact with the inner-layer circuit board.
The adhesive was cured by heating and pressing at 75 ° C. and a pressure of 4 MPa for 90 minutes to prepare a four-layer printed wiring board.

Example 2 A copper foil used in the production of a double-sided copper-clad laminate was replaced with a roughened surface R
A double-sided copper-clad laminate was produced in the same manner as in Example 1, except that the copper was changed to 9.4 μm. Hereinafter, an inner circuit board was prepared in the same manner as in Example 1, and the conditions for the roughening treatment of the inner circuit board with a potassium permanganate-based roughening solution were set to a temperature of 70 ° C.
Then, the immersion time was changed to 5 minutes to perform a roughening treatment, and thereafter, a predetermined oxidation-reduction treatment was performed on the copper foil pattern as a conductor. Rz of the substrate surface of the inner circuit board exposed by etching the copper foil was 9.4 μm before the roughening treatment and 10.9 μm after the roughening treatment. Thereafter, in the same manner as in Example 1, a four-layer printed wiring board was prepared as an inner circuit board.

Comparative Example 1 A four-layer printed wiring board was manufactured in the same manner as in Example 1 except that the roughening treatment with a potassium permanganate-based roughening solution was not performed.

Comparative Example 2 A four-layer printed wiring board was produced in the same manner as in Example 2 except that the roughening treatment with the potassium permanganate-based roughening solution was not performed.

With respect to the four-layer printed wiring board manufactured as described above, the peel strength between the substrate surface and the insulating layer (hereinafter referred to as peel strength) and the heat resistance of the moisture-absorbing solder (hereinafter referred to as the heat resistance) were evaluated in order to evaluate the adhesiveness. Gender). Table 1 shows the results. The test method was as follows.

Peeling strength A test piece of 100 × 25 mm was cut out from the prepared four-layer printed wiring board, and bonded so that the insulating layer formed by curing the adhesive was left in a strip shape having a width of 10 mm in the longitudinal direction. The insulating layer formed by curing the agent was peeled off. Next, the end of the remaining band-shaped portion was peeled off, and the tip was grasped with a gripper of a tester, pulled in a direction perpendicular to the surface of the test piece, and the load required for peeling was measured.

Heat Resistance A test piece of 50 × 50 mm was cut out from the produced four-layer printed wiring board, and the test piece was heated at a temperature of 121 ° C. and a pressure of 2 atmospheres.
After absorbing moisture with a pressure cooker of 026 hPa for a predetermined time, the mixture was floated in a solder bath at a temperature of 260 ° C. for 20 seconds, and the presence or absence of blisters was visually observed. In Table 1, the normal state is a state in which the test piece is cut out,
The PCT-n time (n = 1, 2, 3) indicates that the sample was examined in a state after moisture absorption with a pressure cooker for n hours, and the result was OK for no blistering and NG for blistering. Indicates what was done.

[0032]

[Table 1]

From Table 1, it can be seen that in Examples 1 and 2, the peel strength is greatly improved and the heat resistance is extremely good as compared with Comparative Examples 1 and 2 corresponding thereto. Is shown.

[0034]

According to the present invention, a multilayer printed wiring board having excellent adhesion between the inner circuit board and the insulating layer can be manufactured, and the reliability of the multilayer printed wiring board can be improved.

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Claims (1)

[Claims] 1. A multilayer printed wiring board comprising a step of forming an inner layer circuit pattern by etching, and then roughening a substrate surface of the exposed inner layer circuit board by removing a metal foil by etching. Manufacturing method.