JPH08111586A - Manufacture of multilayer printed wiring board - Google Patents

Abstract

PURPOSE: To smooth the surface of a multilayer printed wiring board and to control the wiring board in thickness independent of the residual rate of an inner copper foil by a method wherein thermosetting undercoat is applied onto an inner circuit board and turned into a B stage, then a copper foil possessed of a thermosetting insulating adhesive agent layer is laminated thereon, and the inner circuit board and the copper foil are formed into one piece by heating. CONSTITUTION: Liquid undercoat 3 is applied onto an inner circuit board 1 thick enough to cover an inner circuit 2 by a coating equipment such as a screen printing device. Thereafter, the liquid undercoat 3 is turned into a B stage by heating. Then, a copper foil 5 where thermosetting insulating adhesive agent 4 is applied is laminated on the undercoat 3 with a hard roll 6. By using the hard roll 6, the surface of a multilayer printed wiring board of this constitution is turned smooth, and an interlayer' thickness between the inner circuit 2 and the copper foil 5 is determined by only the thickness of the thermosetting insulating adhesive agent. Then, a concurrently integrating curing reaction is made to take place by heating to form the undercoat 3 and the thermosetting insulating adhesive agent 4 applied onto the copper foil 5 into one piece, and thus a multilayer printed wiring board 7 is manufactured.

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 multilayer printed wiring board excellent in surface smoothness and plate thickness accuracy without using a hot platen press.

[0002]

2. Description of the Related Art Conventionally, in the case of manufacturing a multilayer printed wiring board, one or more prepreg sheets obtained by impregnating a glass cloth base material with an epoxy resin and forming a B stage on an inner layer circuit board on which a circuit is formed are further stacked. A copper foil is laminated on it and is integrally molded by heating with a hot plate press. However, in this process, the impregnated resin is reflowed by heat and cured under a constant pressure.
1.5 hours is required. In addition to the long manufacturing process, the cost of the hot platen press for stacking multiple layers and the cost of the glass cloth prepreg are high.
In addition, it is difficult to make the interlayer thickness extremely thin because the glass cloth is impregnated with the resin.

In recent years, in order to solve these problems, the technology of a multilayer printed wiring board by a build-up method, which does not perform heat and pressure molding by a hot platen press and does not use glass cloth as an interlayer insulating material, has been renewed attention. There is.

[0004]

In the method for manufacturing a multilayer printed wiring board by the build-up method, when a film-shaped interlayer insulating resin layer is used, the work efficiency is higher than that of the method of forming the interlayer insulating resin layer with prepreg. Remarkably improved. However, it is expected that air will be entrained in the stepped portion between the insulating substrate of the inner layer circuit board and the circuit, and in order to prevent that, lamination must be performed under a reduced pressure environment,
Special equipment is needed. In addition, since the laminated insulating layer follows the step between the insulating substrate of the inner layer circuit board and the circuit, surface smoothness cannot be obtained, and soldering failure etc. may occur during component mounting, or resist There are problems such as peeling and deterioration of pattern development, which makes it impossible to form a stable resist.

Further, the same applies to the case of using a prepreg, but since the amount of resin to be embedded changes depending on the copper foil remaining rate of the inner layer circuit pattern, the same film does not have the same plate thickness after molding. In other words, if the copper foil residual rate is large and the portion to be embedded is small, the plate thickness will be thick, and if the copper foil residual rate is small and the portion to be embedded is large, the plate thickness will be thin. Unless changed, the same plate thickness cannot be achieved.
In addition, even if one inner layer circuit board has a different copper foil residual rate depending on the location, the resulting multilayer printed wiring board may have a non-uniform thickness.

[0006]

According to the present invention, a thermosetting undercoating agent is applied to an inner layer circuit board, and after the B stage, a copper foil having a thermosetting insulating adhesive layer is laminated. Then, the present invention relates to a method for manufacturing a multilayer printed wiring board, which is characterized by integrally curing by heating. And, especially when a fine pattern is required,
As the copper foil, a two-layer structure copper foil having a total thickness of 11 to 250 μm, which has a copper foil layer having a thickness of 1 to 50 μm to be an outer layer circuit and a metal layer having a thickness of 10 to 200 μm to be removed after lamination is used. .

That is, a liquid undercoating agent is applied by screen printing, a roller coater, a curtain coater or the like to fill the recesses between the copper foil circuits of the inner layer circuit board, and the heat treatment is carried out to obtain the B stage. The B-staged undercoating agent can temporarily retain its shape, and then by using a heated hard roll or the like when adhering the copper foil with a thermosetting insulating adhesive,
The undercoating agent can be remelted and laminated with good surface smoothness without involving the air in the step portion between the insulating substrate of the inner layer circuit board and the circuit. At that time, the thermosetting insulating adhesive coated on the copper foil is bonded by the epoxy resin component having a weight average molecular weight of 10,000 or more while maintaining its shape, that is, while maintaining the interlayer thickness. It is possible to produce a multilayer printed wiring board having excellent board thickness accuracy without depending on Then, the undercoat agent and the thermosetting insulating adhesive-attached copper foil are integrally molded by heating after laminating to cause simultaneous integral curing reaction.

The copper foil used is preferably thick so as not to follow the step between the insulating substrate of the inner layer circuit board and the circuit during lamination. However, when etching is performed at the time of subsequent circuit formation, if the copper foil is thick, the time becomes long and the etching in the width direction is increased, so that it is difficult to form a sufficient fine pattern. Therefore, especially when a fine pattern is required, the thickness of the outer layer circuit 1 to
50 μm copper foil layer and thickness to be removed after lamination 10
Total thickness 11 to 2 having a metal layer (carrier) of 200 μm
By using a copper foil having a two-layer structure of 50 μm, surface smoothness can be obtained without following a step during lamination, and etching time is shortened to form a fine pattern when a circuit is formed after the carrier is removed. It becomes possible. Aluminum, copper or the like is used as the metal layer, and if the thickness is thinner than 10 μm, it follows the step, and if it is thicker than 200 μm, heat from the roll is difficult to be transferred during lamination, which is not preferable. If the thickness of the copper foil is thicker than 50 μm, it becomes difficult to follow the steps, and the carrier layer that is removed after lamination is unnecessary.

In the present invention, the undercoat agent fills the recesses between the copper foil circuits of the inner layer circuit board and smoothes the surface of the inner layer circuit. Its composition is an epoxy resin and a curing agent therefor. Since it is necessary to completely embed the inner layer circuit during lamination, a liquid epoxy resin is preferable in the case of a solventless system. Specifically, the epoxy resin includes polyphenol phenol epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolac type epoxy resin, and cresol novolac type epoxy resin, An epoxy compound of a polyhydric alcohol, an alicyclic epoxy resin, or the like can be used. Furthermore, a brominated epoxy resin may be used to impart flame resistance.

As the epoxy resin curing agent, an amine curing agent, an amide curing agent, an imidazole curing agent, or an epoxy adduct or microencapsulation of these is selected. For example, aliphatic amines such as diethylenetriamine, alicyclic polyamines such as isophoronediamine, dicyandiamide or derivatives thereof, 2
-Methylimidazole, 2-ethyl-4-methylimidazole, 2-phenyl-4-methylimidazole, 1-
Butylimidazole, 2-allylimidazole, 2-phenyl-4-methyl-5-hydroxyimidazole, 2
-Phenyl-4,5-dihydroxymethylimidazole or a cyanoethylated product thereof, or a salt obtained by forming a tertiary nitrogen atom in the imidazole ring with trimellitic acid is used. Among such curing agents, dicyandiamide, an imidazole compound or a microencapsulated imidazole compound is preferable. The amount of such a curing agent is usually 1 to 1 with respect to 100 parts by weight of the epoxy resin.
It is 00 parts by weight. If it is less than 1 part by weight, curing will not proceed sufficiently and it will not be practical. If the amount is more than 100 parts by weight, the crosslinking density becomes too high and the undercoating agent becomes hard and brittle. In the case of dicyandiamide or an imidazole compound, the curability is excellent, so 1 to 50 parts by weight is preferable to 100 parts by weight of the epoxy resin. Moreover, you may add a hardening accelerator as needed.

Further, if necessary, an inorganic filler such as a reactive diluent having a glycidyl group, fused silica, crystalline silica, calcium carbonate, aluminum hydroxide, alumina, mica, talc, white carbon and E glass powder. Can be blended. It is also possible to add an epoxysilane coupling agent for improving the adhesion and moisture resistance to the copper foil or the inner layer circuit board, a defoaming agent for preventing voids, and a liquid or powder flame retardant.

Next, the thermosetting insulating adhesive for coating the copper foil will be described. Generally, rubber compounds, polyvinyl butyral, phenoxy resin, polyester resin, etc. are compounded as a method for forming an adhesive film, which is an interlayer insulating layer, into a film or a roll, but these components are thermally mixed as a multilayer printed wiring board. Reduce performance. For this reason, the adhesive used in the present invention has a weight average molecular weight of 1000 in order to keep the fluidity small and maintain the interlayer thickness when it is integrally cured with the undercoat agent, and to have film formability.
0 or more bisphenol A type epoxy resin or bisphenol F type epoxy resin is blended. The compounding ratio of such an epoxy resin is 30 to 90% by weight, preferably 50 to 90% by weight, based on the whole epoxy resin. As the curing agent, the one used for the undercoat agent described above can be used.

A method for applying an undercoating agent and laminating and curing a copper foil with a thermosetting insulating adhesive to achieve the object of the present invention will be described with reference to FIG.

(A) A liquid undercoat agent (3) is applied to the inner layer circuit board (1) to a thickness to cover the inner layer circuit (2) by using conventional coating equipment such as screen printing, roller coater, curtain coater and the like. To apply. If the filling amount is insufficient, air will be trapped in the subsequent laminate. Then, it is brought into the B stage state by heat treatment.

(B) Thermosetting insulating adhesive (4) on the surface
The copper foil (5) coated with is laminated. The laminator preferably uses hard rolls (6) to achieve surface smoothness. Lamination conditions differ depending on the pattern of the inner layer circuit, but the normal pressure is 0.5 to 6 kgf /
cm ^2, the surface temperature of 100 ° C. of about from room temperature, the laminate speed performed at the degree 0.1～6M / min. Under such conditions, the viscosity of the undercoating agent in the B stage state is 1 to 300 poise, and surface smoothness can be achieved by using a hard roll or the like. At this time, the interlayer thickness between the inner layer circuit (2) and the copper foil (5) can be achieved by the thickness of the thermosetting insulating adhesive.

(C) Next, the undercoat agent (3) and the thermosetting insulating adhesive (4) coated on the copper foil are integrally molded by heating to carry out simultaneous monolithic curing reaction. Can be produced.

Next, FIG. 2 shows a copper foil layer serving as an outer layer circuit and a metal layer (carrier) removed after lamination.
This is a case of using a copper foil having a two-layer structure having and. In this case, after passing through the steps (A) and (B), in the step (C), the undercoat agent (13) and the thermosetting insulating adhesive ((2) -coated copper foil (15) coated ( 4) is integrally molded and then a copper foil layer (16) is formed as an outer layer circuit by removing a metal foil (17) which is an outer carrier that does not form an outer layer circuit in the two-layer structure copper foil. A multilayer printed wiring board (19) can be produced.

[0018]

EXAMPLES The present invention will be described below with reference to examples.

Example 1 Bisphenol A type epoxy resin (epoxy equivalent 6400, weight average molecular weight 3000)
0) 100 parts by weight and 80 parts by weight of a bisphenol F type epoxy resin (epoxy equivalent 175, Epicron 830 manufactured by Dainippon Ink and Chemicals, Inc.) were dissolved in MEK while stirring, and 15 parts by weight of dicyandiamide as a curing agent and A thermosetting insulating adhesive varnish was prepared by adding 10 parts by weight of micro-encapsulated 2-imidazole as a curing accelerator and 5 parts by weight of a silane coupling agent (A-187 manufactured by Nippon Unicar Co., Ltd.). This varnish has a thickness of 1
The resin thickness after drying is 35μ on the anchor surface of the 8μm copper foil.
m was coated with a roller coater and dried to prepare a thermosetting type copper foil with an insulating adhesive.

Next, 100 bisphenol A type epoxy resin (Epicote 828 manufactured by Yuka Shell Epoxy Co., Ltd.)
An undercoating agent was prepared by dispersing 10 parts of dicyandiamide as a curing agent and 3 parts of a curing accelerator 2-phenyl-4-methylimidazole in each part.

On the other hand, the substrate thickness is 0.1 mm and the copper foil thickness is 35 μm.
The glass-epoxy double-sided copper-clad laminate was processed by patterning to obtain an inner layer circuit board. After blackening the copper foil surface, the above undercoat agent is applied to a curtain coater to a thickness of about 40 μm.
And was heated in an air oven at 130 ° C. for 30 minutes to be in the B stage state. Thereafter, the copper foil with the thermosetting insulating adhesive was laminated using a hard roll under the conditions of a temperature of 100 ° C., a pressure of ² kf / cm ² , and a laminating speed of 0.8 m / min. Then, it was heated and cured at 180 ° C. for 20 minutes to produce a multilayer printed wiring board.

Example 2 As the copper foil, a copper foil having a two-layer structure consisting of a copper carrier having a thickness of 70 μm and a copper foil layer having a thickness of 9 μm was used, and a thermosetting insulating adhesive was used.
A multilayer structure having a copper foil for an outer layer circuit having a thickness of 9 μm in the same manner as in Example 1 except that a layered copper foil is laminated on an inner layer circuit board coated with an undercoating agent, heat-cured, and then the copper carrier is peeled off. A printed wiring board was produced.

<Examples 3 and 4> Multilayer printed wiring boards were prepared in the same manner as in Examples 1 and 2 except that the inner layer circuit board had a circuit copper thickness of 70 µm and the undercoating agent had a thickness of 80 µm.

Comparative Example 1 A multilayer printed wiring board was prepared in the same manner as in Example 1 except that the undercoating agent was not applied.

Comparative Examples 2 and 3 A multilayer printed wiring board was prepared in the same manner as in Examples 1 and 2 except that the undercoating agent applied on the inner layer circuit board was heated at 180 ° C. for 60 minutes to be completely cured. It was made. The obtained multilayer printed wiring board has the characteristics shown in Table 1.

(Test method) Inner layer circuit board test piece: 150 μm pitch between lines, clearance hole 1.0 mmφ 1. 1. Surface smoothness: JIS B 0601 R (max) Moisture absorption solder heat resistance test Moisture absorption conditions: Pressure cooker treatment, 125 ° C, 2.
3 atmospheres, 30 minutes Test condition: n = 5, all test pieces at 280 ° C., 120
The case where there was no blistering in a second was marked with ◯. 3. Embedding property: After peeling off the outer layer copper foil, it was visually judged using an optical microscope whether or not the inner layer circuit was embedded, and the one embedded was rated as ◯. 4. Interlayer insulating layer thickness: The multilayer printed wiring board was cut, the cross section was observed with an optical microscope, and the interlayer insulating layer thickness between the inner layer circuit and the surface copper foil was measured.

Table 1 ───────────────────────────────── Surface smoothness Moisture absorption Solder heat resistance Implantability Interlayer insulation layer Thickness ───────────────────────────────── Example 1 6 μm ○ ○ 35 μm Example 2 3 ○ ○ 35 Implemented Example 3 6 ○ ○ 35 Example 4 3 ○ ○ 35 Comparative Example 1 12 × × 30 Comparative Example 2 15 ○ ○ 40 Comparative Example 3 15 ○ ○ 40 ──────────────── ─────────────────

[0028]

According to the method of the present invention, by laminating a copper foil with a thermosetting insulating adhesive on a hard roll or the like, the B-staged undercoating agent coated on the inner layer circuit is remelted and the surface is re-melted. Is smoothed, and the thermosetting insulating adhesive coated on the copper foil maintains its thickness, so it is necessary to produce a multilayer printed wiring board with excellent board thickness control without depending on the residual rate of the inner copper foil. You can Furthermore, the undercoating agent and the thermosetting insulating adhesive coated on the copper foil can be integrally molded by heating after laminating and simultaneously performing an integral curing reaction.

Further, by using a copper foil having a two-layer structure having a metal layer serving as a carrier as the copper foil, the copper foil with a thermosetting insulating adhesive is removed after lamination when laminating with a hard roll or the like. The double-layered copper foil, which is thicker because it has a metal layer, does not easily follow the steps of the inner layer circuit,
The surface smoothness of the multilayer printed circuit board is further improved, and a finer pattern circuit can be formed.

Further, it is possible to manufacture a multilayer printed wiring board having an outer layer copper foil by a laminating method without using a prepreg and a hot platen press as in the prior art and without plating as in an additive method. Therefore, the time required to form the insulating layer and the outer conductive layer is significantly shortened, which can contribute to simplification of the process and cost reduction. Furthermore, since no glass cloth is used, the interlayer insulating layer can be made extremely thin.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a process for producing a multilayer printed wiring board (one example) of the present invention.

FIG. 2 is a schematic cross-sectional view showing a process for producing a multilayer printed wiring board (another example) of the present invention.

[Explanation of symbols]

 1 Inner Layer Circuit Board 2 Inner Layer Circuit 3 Undercoat Agent 4 Thermosetting Insulating Adhesive 5 Copper Foil 6,18 Hard Roll 7,19 Multilayer Printed Wiring Board 15 2 Layer Hard Copper Foil 16 Copper Foil Layer 17 Metal Layer (Carrier)

Claims (4)

[Claims] 1. An inner layer circuit board is coated with a thermosetting undercoating agent, the undercoating agent is brought into a B-stage state, and then a copper foil having a thermosetting insulating adhesive layer is laminated, and then, A method for manufacturing a multilayer printed wiring board, which comprises integrally curing by heating. 2. The total thickness 11 according to claim 1, wherein the copper foil includes a copper foil layer having a thickness of 1 to 50 μm to be an outer layer circuit and a metal layer having a thickness of 10 to 200 μm to be removed after lamination. A method for manufacturing a multilayer printed wiring board, which comprises using a copper foil having a two-layer structure of 250 μm. 3. The thermosetting insulating adhesive comprises an epoxy resin and its curing agent, and one component of the epoxy resin comprises a bisphenol A type epoxy resin or a bisphenol F type epoxy resin having a weight average molecular weight of 10,000 or more. 1. A method for manufacturing a multilayer printed wiring board according to 1 or 2. 4. The epoxy resin 1 is used as the undercoat agent.
The method for producing a multilayer printed wiring board according to claim 1 or 2, which comprises 100 parts by weight of the epoxy resin curing agent and 1 to 100 parts by weight of the epoxy resin curing agent.