JPH08111585A - 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 a residual rate of an inner copper foil by a method wherein photo/thermosetting undercoat is applied onto an inner circuit board and turned into a B stage by light irradiation, 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 inner circuit board 1 is exposed to light by a light exposure device such as a UV irradiation conveyer or the like to set the liquid undercoat 3 into a B stage. 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 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 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. The process of stacking copper foil on it and heating and integrally molding it with a hot platen press is performed. 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, an inner layer circuit board is coated with a light / thermosetting undercoat agent, and after being irradiated with light to be B-staged, it has a thermosetting insulating adhesive layer. This is a method for manufacturing a multilayer printed wiring board, which comprises laminating a copper foil and then integrally curing it by heating. And when a fine pattern is particularly required, in order to improve the surface smoothness after lamination, as the copper foil, a layer of the copper foil having a thickness of 1 to 50 μm to be an outer layer circuit and a thickness to be removed after lamination are formed. A two-layer copper foil having a total thickness of 11 to 250 μm with a metal layer of 10 to 200 μm 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 UV.
The undercoating agent is converted to the B stage by irradiating light with an exposure machine such as an irradiation conveyor. The B-staged undercoating agent can temporarily retain its shape, and thereafter, by using a heated hard roll or the like when adhering the copper foil with a thermosetting insulating adhesive, The undercoating agent can be laminated again with good surface smoothness without re-melting and entraining air in the step portion between the insulating substrate of the inner layer circuit board and the circuit. At that time, since 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, the inner layer copper foil residual rate 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 undercoating agent fills the recesses between the copper foil circuits of the inner layer circuit board and smoothes the surface of the inner layer circuit. The epoxy resin, the epoxy resin curing agent, the photocurable resin and the photocurable resin are used. It consists of a polymerization initiator. Since it is necessary to completely embed the inner layer circuit at the time of lamination, it is preferable to use a liquid resin as the epoxy resin and the photocurable resin. Specifically, epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, and other polyphenol phenolic epoxy resins are available. 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-based curing agent, an amide-based curing agent, an imidazole-based curing agent, or an epoxy adduct or microencapsulated product of these is selected. For example, aliphatic amines such as diethylenetriamine, alicyclic polyamines such as isophoronediamine, dicyandiamide or derivatives thereof, 2-
Methyl imidazole, 2-ethyl-4-methyl imidazole, 2-phenyl-4-methyl imidazole, 1-butyl imidazole, 2-allyl imidazole, 2-phenyl-4-methyl-5-hydroxy imidazole, 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 compounding amount of such a curing agent is 1 to 30 parts by weight with respect to 100 parts by weight of the epoxy resin. 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 30 parts by weight, the crosslinking density becomes too high and the undercoating agent may become hard and brittle. Moreover, you may add a hardening accelerator as needed.

The photo-curable resin is preferably a liquid acrylate resin, and among them, an epoxy acrylate resin obtained by acrylate conversion of an epoxy resin, such as bisphenol A type epoxy acrylate, bisphenol F type epoxy acrylate, novolac type epoxy acrylate, Alternatively, urethane acrylates are preferably used, and the amount is 1 to 100 relative to 100 parts by weight of the epoxy resin.
It is blended by weight. The average molecular weight of the acrylate resin is 5
It is preferably from 0 to 1500, and when the molecular weight is higher than that, the viscosity and the solidification are increased like the epoxy resin. The tackiness, hardness, etc. of the resin surface after the B stage is formed by light irradiation are adjusted by the amount of the acrylate resin. If the amount of the acrylate resin is less than 1 part by weight, the compounding effect is scarce, and if it exceeds 100 parts by weight, mechanical properties, heat resistance, chemical resistance and the like are deteriorated, which is not preferable.

The photopolymerization initiator is a radical polymerization initiator, and a benzoin ether type, a benzophenone type, a ketal type, an acetophenone type, a thioxanthone type or the like can be used, and particularly 1-hydroxycyclohexylacetophenone which is excellent in moldability and cured product characteristics. And 2,2-dimethoxy-
1,2-diphenylethan-1-one is preferred. The amount of the photopolymerization initiator compounded is 1 to 10 parts by weight based on 100 parts by weight of the photocurable resin. If it is less than 1 part by weight, the compounding effect will be small, and if it is more than 10 parts by weight, it will cause deterioration of properties after curing.

Further, if necessary, an inorganic filler such as fused silica, crystalline silica, calcium carbonate, aluminum hydroxide, alumina, mica, talc, white carbon or E glass powder can be added. 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, a liquid or powder flame retardant, and the like.

Next, the thermosetting insulating adhesive 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 of 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 outlined with reference to FIG.

(A) The inner layer circuit board (1) is coated with a liquid undercoat agent (3) on the inner layer circuit (2) using a conventional coating equipment such as screen printing, roller coater or curtain coater. To apply. If the filling amount is insufficient, air will be trapped in the subsequent laminate. After that, exposure is performed by an exposure device such as a UV irradiation conveyor to form a B stage.

(B) Thermosetting insulating adhesive (4) on the surface
Is laminated on the coated copper foil (5). 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) Then, the undercoat agent (3) and the thermosetting insulating adhesive (4) coated on the copper foil are integrally molded by heating and simultaneously performing an integral curing reaction to form a multilayer printed wiring board. (7) can be produced.

Next, FIG. 2 shows a metal layer (carrier) which is removed after lamination with a layer of copper foil which will be an outer layer circuit as a copper foil.
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.

[0020]

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, bisphenol A type epoxy resin (Epicote 828 manufactured by Yuka Shell Epoxy Co., Ltd.) 100
Parts by weight, 10 parts by weight of bisphenol A type epoxy acrylate resin (lipoxy SP-1507 manufactured by Showa High Polymer),
2-Encapsulated as epoxy resin curing agent
A composition of 10 parts by weight of methylimidazole and 0.5 parts by weight of a photopolymerization initiator (Irgacure 184 manufactured by Ciba-Geigy) was sufficiently stirred with a homomixer to prepare an undercoating agent.

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, apply the above undercoat agent with a curtain coater to a resin thickness of about 40
It was applied to a thickness of μm. After that, 80W / with UV conveyor machine
Ultraviolet irradiation was carried out with two cm high pressure mercury lamps under the condition of about 2 J / cm ² . Temperature 1 on the B-staged undercoat agent
00 ℃, pressure 2kgf / cm ² , laminating speed
The copper foil with the thermosetting insulating adhesive was laminated using a hard roll under the condition of 0.8 m / min.
The mixture was heated and cured at ℃ for 20 minutes to produce a multilayer printed wiring board.

Example 2 As the copper foil, a copper foil having a two-layer structure composed 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 produced 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 exactly 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.

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 ──────────────── ─────────────────

(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.

[0030]

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 undercoat agent which has been B-staged by being irradiated with light after being applied to the inner layer circuit is remelted. Since the surface is smoothed and the thermosetting insulating adhesive coated on the copper foil maintains its thickness, a multilayer printed wiring board with excellent board thickness control without depending on the residual rate of the inner copper foil Can be made. Furthermore,
The undercoating agent and the thermosetting insulating adhesive coated on the copper foil can be integrally molded by heating after laminating and performing simultaneous integral curing reaction.

Furthermore, by using a copper foil having a two-layer structure having a metal layer serving as a carrier as the copper foil, when the copper foil with a thermosetting insulating adhesive is laminated with a hard roll or the like, it is removed after the lamination. 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 the 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)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Satoshi Hayai 2-5-8 Higashi-Shinagawa, Shinagawa-ku, Tokyo Sumitomo Bakelite Co., Ltd.

Claims (4)

[Claims] 1. An inner-layer circuit board is coated with a light / thermosetting undercoat agent, and after being irradiated with light to be B-staged, 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. The method for manufacturing a multilayer printed wiring board according to 1 or 2. 4. The epoxy resin 1 is used as the undercoat agent.
1. 1 part by weight to 100 parts by weight of photocurable resin, 1 part by weight to 30 parts by weight of epoxy resin curing agent, 1 part by weight to 100 parts by weight of epoxy resin curing agent, 2. The method for manufacturing a multilayer printed wiring board according to 2.