JP2001352173A - Multi-layer printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multi-layer wiring board whose surface smoothness is made excellent by packing paste-shaped packing materials in a through-hole without mixing any air bubble. SOLUTION: A hole for a through-hole is formed in a base, and a conductor is formed on the inner wall of the through-hole so that a board having the through-hole can be constituted, packing materials are packed in the through- hole, and inter-layer insulating material layers are formed on the both faces of the board. Moreover, a conductive circuit is formed on the surface of each inter-layer insulating material layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board and a method for manufacturing the same, and more particularly to a multilayer printed wiring board having excellent through-hole connection reliability and substrate surface smoothness.

[0002]

2. Description of the Related Art In recent years, as electronic devices have been reduced in size and modularized, printed wiring boards used in hybrid modules have been required to have higher densities. To meet such requirements, both sides (multilayer) with through holes
Printed wiring boards are being manufactured. When manufacturing a printed wiring board having a through hole, a tenting method of forming a circuit by etching a pattern using a photosensitive dry film is used. However,
This method has a disadvantage that the dry film is easily damaged at the through-hole portion and the inner wall of the through-hole is dissolved during etching. In addition, there is a method of applying a liquid photosensitive resin liquid instead of a photosensitive dry film, but there is a problem that it is difficult to apply the liquid uniformly on the substrate surface due to the presence of through holes. Also,
When a board with through holes is used for the inner layer of a build-up multilayer wiring board, the impedance control is difficult because the through holes are depressed when the interlayer insulating layer is provided, and the thickness of the interlayer insulating layer varies. In the case where a recess is formed in the pad portion, there has been a problem that the mounting reliability of the IC is reduced.

[0003] Due to the problems described above, conventionally, a conductor is formed on the inner wall of a through-hole for a through-hole, the through-hole is formed, and then the through-hole is filled with a paste-like filling material to form a printed wiring board. A method of smoothing the surface has been adopted.

However, when filling a paste-like filling material, the paste is easily filled with air entrained therein, and the surface layer of the filled material hardens relatively easily, so that air bubbles escape. When the remaining filling material on the substrate surface is removed by polishing or the like, a dent remains on the substrate surface. In addition, if air is trapped in the filling material, thermal expansion and the like will cause destruction due to thermal expansion when mounting electronic components due to thermocompression bonding, etc., resulting in reduced heat resistance, moreover, moisture absorption and poor insulation. There was a problem.

[0005] Therefore, when filling the filling material,
Various methods have been developed for removing air bubbles in the filler material. For example, Japanese Patent Application Laid-Open No. Sho 62-173794 discloses a method in which a filler material is filled in a through hole of a ceramic substrate, and then the filler material is brought into contact with a solvent to form a surface. There is disclosed a method for removing bubbles by lowering the viscosity and surface tension of the foam.

[0006]

However, this method is
Since the viscosity and surface tension of the surface of the filling material are reduced, the viscosity and surface tension of the material must be controlled so that the filling material does not flow out, and there has been a problem that quality control is difficult in mass production.

As described above, it has been desired to develop a printed wiring board having excellent surface smoothness by filling a through-hole with a paste-like filling material without mixing air bubbles. The present inventors have conducted intensive studies and found that the above-mentioned problems can be solved by using a gas-permeable substrate.

[0008]

According to the present invention, a through hole for a through hole is provided in a base, a conductor is formed on an inner wall of the through hole to form a substrate having a through hole, and a filling material is filled in the through hole. The multilayer printed wiring board is characterized by being filled, provided with an interlayer insulating material layer on both surfaces of the substrate, and further formed with a conductor circuit on the surface of each interlayer insulating material layer.

In the present invention, it is desirable that a gas-permeable substrate is brought into close contact with one surface of a printed wiring board having a through hole, and that a paste-like filling material is press-fitted and filled. The reason for this is that even if bubbles are contained in the paste-like filling material, they will permeate through the permeable substrate during press-fitting, and the filling material itself does not penetrate through the substrate. The packing material is densely packed. For this reason, the surface smoothness of the substrate is excellent, and the inner wall of the through hole is reliably protected, so that it does not dissolve at the time of etching, thereby improving the connection reliability of the through hole.

In the present invention, the air-permeable substrate used is:
It refers to a membrane or a plate-like material that allows air to permeate but does not allow the filling material to permeate, such as a fibrous film or a porous substrate.

As the fibrous film, papers such as filter paper and Japanese paper are preferable, and as the porous substrate, a ceramic plate and the like are preferable. The reason for this is that they are excellent in air permeability, have an effect of facilitating the escape of air in the through hole, and preventing the filling resin from coming off.

As the paste-like filling material used in the present invention, an insulating resin such as a thermosetting heat-resistant resin, a photosensitive heat-resistant resin, or a thermoplastic heat-resistant resin is desirable. For example, in the case of an epoxy resin, Epicoat 828 is used. , 1001 (both trade names of Yuka Shell), EOCN-104S (trade name of Nippon Kayaku) and the like. Further, the paste-like filling material may contain a filler. As the filler, epoxy resin fine powder, amino resin powder, inorganic fine powder and the like are preferable. The reason for this is that there is an effect such as relaxation of curing shrinkage of the filling resin.

The viscosity of the paste-like filling material is preferably 1 to 10 Pa · s, depending on the coating method. The reason for this is that if the pressure is less than 1 Pa · s, the resin filled in the through-hole penetrates into the substrate, resulting in a shortage of resin in the through-hole, causing dents or resin loss. This is because bubbles in the material are difficult to escape and the leveling property is poor. The viscosity of the paste-like filling material is preferably adjusted using a solvent such as methyl ethyl ketone, methyl cellosolve, butyl cellosolve, butyl cellosolve acetate, butyl carbitol, butyl cellulose, tetralin, dimethylformamide, and normal methylpyrrolidone.

In the present invention, the means for press-fitting the paste-like filling material is preferably a roll coater, a stripe, or the like. The pressure at the time of the press-fitting is desirably 1 to 4 kg / cm ² . The reason is that if it is less than 1 kg / cm ² , the resin may not be completely filled, and if it exceeds 4 kg / cm ² , dents are likely to be generated on the surface.

After press-fitting the paste-like filling material, the paste-like filling material is dried and hardened, and after being dried and hardened, unnecessary filling material is removed by polishing or sandblasting as necessary. It is desirable to make the surface flat.

In the present invention, as a method of forming a through hole, a conventional method of electroless plating or electrolytic plating can be used. As plating, copper, nickel, gold or the like is preferably used.

In the present invention, the conductive circuit is formed by a subtractive method of etching a metal layer,
Various methods such as an additive method of forming a conductor circuit by electroless plating or the like can be used. When the additive method is used, a printed wiring board can be manufactured by the following steps. (A) An adhesive layer for electroless plating as described below is formed and roughened on a substrate such as an insulating plate or a metal plate, and this is used as a base, and a through hole for a through hole is provided. A process of manufacturing a substrate having a conductor circuit and a through hole by forming a plating resist as necessary, further forming a conductor circuit on the inner wall of the through hole and the surface of the substrate. (B) a step of bringing a gas permeable substrate into close contact or contact with one surface of a substrate having a through hole; (C) a step of press-fitting the paste-like filling material from the surface opposite to the surface on which the air-permeable substrate is in close contact or contact. (D) curing the filling material; Further, if necessary, a step of removing the remaining filling material by polishing or the like may be adopted.

When the subtractive method is used, a printed wiring board can be manufactured by the following steps. (A) A substrate provided with a metal layer on both surfaces is used as a base, a through hole for a through hole is provided, a catalyst nucleus is applied, electroless plating is performed, and a conductor is provided in the through hole. Manufacturing a substrate having: (B) a step of bringing a gas permeable substrate into close contact or contact with one surface of a substrate having a through hole; (C) a step of press-fitting the paste-like filling material from the surface opposite to the surface on which the air-permeable substrate is in close contact or contact. (D) curing the filling material; (E) forming an etching resist and etching to form a conductor circuit; If necessary, a step of removing the remaining filler material by polishing or the like may be employed.

The multilayer printed wiring board thus obtained is provided with a through hole for a through hole in a substrate, a conductor is formed on the inner wall of the through hole to form a substrate having a through hole, and a filling material is filled in the through hole. While filling
A multilayer printed wiring board comprising an interlayer insulating material layer provided on the substrate, and a conductive circuit formed on the surface of the interlayer insulating material layer. The multilayer printed wiring board of the present invention is a double-sided (including, of course, multilayer) wiring board.

According to the present invention, a build-up multilayer printed wiring board is manufactured by using such a printed circuit board as an inner layer board to prevent the resin from filling the through hole and to prevent air from being mixed in the filling material. Therefore, a multilayer printed wiring board having excellent surface smoothness can be manufactured, and mounting reliability and impedance control of electronic circuit components can be easily performed.
As a method of manufacturing a build-up multilayer printed wiring board,
After forming a photosensitive adhesive layer on the surface of the printed wiring board for the inner layer manufactured by the additive and subtractive method, exposing and developing an opening to roughen the surface of the adhesive layer, Electroplating is performed to form a conductive circuit on the surface of the adhesive layer and on the opening, and the upper conductive circuit and the inner conductive circuit are electrically connected.

When the conductor circuit is manufactured by the additive method in the present invention, a hardening treatment which is soluble in an acid or an oxidizing agent is carried out in a matrix made of a resin which is hardly soluble in an acid or an oxidizing agent as an adhesive. It is desirable that the heat-resistant resin powder is dispersed, and the heat-resistant resin powder is 1) an average particle diameter of 10 μm or less, and 2) the heat-resistant resin powder aggregates a heat-resistant resin powder having an average particle diameter of 2 μm or less. Agglomerated particles having an average particle size of 2 to 10 μm; 3) a mixture of a heat-resistant resin powder having an average particle size of 2 to 10 μm and a heat-resistant resin powder having an average particle size of 2 μm or less; 10μ
It is desirable to select from pseudo particles obtained by adhering at least one of a heat-resistant resin powder having an average particle size of 2 μm or less and an inorganic powder having an average particle size of 2 μm or less to the surface of the heat-resistant resin powder having a particle size of m.

The above-mentioned adhesive layer can be provided with a roughened surface by roughening it with an acid or an oxidizing agent. This is because adhesion can be improved. The matrix resin is desirably photosensitive. By using a photosensitive resin, a via hole can be formed by exposure and development. The adhesive becomes an interlayer insulating material layer in the build-up multilayer wiring board. In addition, as for the anchor shape and anchor depth formed by such an adhesive layer, it is desirable that the surface roughness is in the range of 1 μm to 20 μm with fillers having different particle diameters. Sufficient adhesion strength is obtained.

In the multilayer printed wiring board of the present invention, it is preferable that the roughened layer made of the electroless plating film provided at the interface between the conductor circuit and the interlayer insulating material layer is a eutectic compound made of copper, nickel and phosphorus. The reason for this is that the surface of the blackened and reduced treated surface oxidizes the surface to form copper oxide on the surface and roughens the surface.However, the strength of the copper oxide, which is a roughened layer, is low, and this is destroyed by thermal shock. Delamination occurs, but the eutectic compound obtained by the eutectic plating of the present invention has high strength, so that delamination due to thermal shock hardly occurs and heat cycle characteristics are improved. Further, such a eutectic compound is mainly a needle-like crystal, so that it has a high effect as an anchor, and can adhere a conductive circuit to an interlayer insulating material layer, thereby improving heat cycle characteristics. Furthermore, after the blackening reduction treatment, the copper oxide is exposed to the surface, so that it is easily dissolved in an acid solution, so that a so-called haloing phenomenon is likely to occur. , It is not dissolved, and high adhesion can be secured.

The contents of copper, nickel and phosphorus in the eutectic compound are 90 to 96%, 1 to 3%, and 0.5 to 96%, respectively.
Desirably, it is about 2 wt%. This is because, in the above range, the crystals of the deposited film have a needle-like structure, so that the anchor effect is excellent. The thickness of the roughened layer is preferably 5 μm, more preferably 0.5 μm to 2 μm. The reason is that the anchor effect is low at 0.5 μm or less, and the surface roughness is too large at 5 μm or more,
Conversely, the adhesion strength decreases. In the multilayer printed wiring board of the present invention, the conductor circuit on the substrate and the conductor circuit provided on the interlayer insulating material layer may be electrically connected via holes or through holes. When connecting via holes, it is necessary that the roughened layer at the connection location has been removed in advance or that no roughened layer is provided.

[0025]

Examples and Comparative Examples Hereinafter, Examples 1 and Comparative Examples 1 embodying the present invention will be described in detail with reference to the drawings.

Example 1 Manufacturing process (1) to multilayer printed wiring board of Example 1
(9) will be described with reference to FIGS. Step (1): Drill 0.2 diameter on double-sided copper-clad laminate
The through-hole 3 of mm was formed. After applying and activating an active catalyst on the entire surface, electroless plating was performed according to a conventional method, and copper was deposited on the inner wall of the through hole 3 to form a through hole 4. Step (2): Japanese paper 5 was placed on the laminated plate in which the through holes 4 were formed. Step (3): 60 parts by weight of phenol novolak type epoxy resin (manufactured by Yuka Shell), 40 parts by weight of bisphenol A type epoxy resin (manufactured by Yuka Shell) and 5 parts by weight of imidazole-based curing agent (manufactured by Shikoku Chemicals) are butyl cells Dissolved in Solvent Acetate, and 15 parts by weight of an epoxy resin fine powder having a particle size of 0.5 μm and 30 parts by weight of a epoxy resin fine particle having a particle size of 5.5 μm were added to 100 parts by weight of a solid content of the composition. And then kneading with three rolls, further adding butyl cellosolve acetate, solid concentration 75%
Was prepared. The viscosity of this solution was measured using a digital viscometer manufactured by Tokyo Keiki Co., Ltd. at 20 ° C. for 60 seconds according to JIS-K7117, and found to be 5.2 Pa · s at a rotation speed of 6 rpm and 2.6 Pa · s at a rotation speed of 60 rpm.
s, and its SVI value (thixotropic property) is 2.
It was 0. Step (4): Surface pressure 3 kg / c by roll coater 7
The filling material 14 was pressed into the through hole 4 at m ² . Step (5): The above-mentioned filling material 14 was dried, heated and cured, and excess filling material 14 was removed by polishing and flattened. Step (6): After removing the Japanese paper 5, a dry film was laminated, and this was exposed and developed to obtain an etching resist. Step (7): Etching was performed with an aqueous cupric chloride solution to obtain a double-sided printed circuit board (inner circuit 8). Since the through-hole 4 was protected by the filling material 14, it was not etched. No bubbles or depressions were found in the filled through holes 4. Step (8): The substrate is subjected to acidic degreasing, soft etching sulfuric acid activation catalyst application and activation, and then plated in the following electroless plating bath to form a 1 μm-thick uneven surface of Ni-P-Cu eutectic. 9 was obtained. Electroless plating bath Copper sulfate: 10.1 g / l Nickel sulfate: 1.0 g / l Sodium hypophosphite: 20.2 g / l Sodium hydroxide: appropriate amount pH = 9.0 Step (9): Cresol novolak type epoxy 60 parts by weight of a 50% acrylate resin (manufactured by Yuka Shell, trade name: Epicoat 180S), 40 parts by weight of a bisphenol A type epoxy resin (manufactured by Yuka Shell, trade name: E-1001), 15 parts by weight of diallyl terephthalate, 2-methyl-
4 parts by weight of 1- [4- (methylthio) phenyl] 2-morpholinopropanone-1 (manufactured by Ciba-Geigy, trade name: Irgacure-907), a fine powder of epixy resin having a particle size of 5.5 μm (manufactured by Toray) 10 Parts by weight and particle size 0.5μ
m of epoxy resin fine powder (manufactured by Toray Co., Ltd.). Then, the mixture was stirred with a homodisper stirrer while adding an appropriate amount of butyl cellosolve to prepare a varnish of the adhesive.

Step (10): After applying the above adhesive varnish on the inner layer circuit 8 using the roll coater 7, the applied varnish is dried and cured at 100 ° C. for 1 hour to obtain a thickness of 50%.
A photosensitive adhesive layer (interlayer insulating layer) 12 of μm was formed. Step (11): Next, a black circle having a diameter of 100 μm and a photomask film having a punched and cut portion printed in black are brought into close contact with the wiring board subjected to the processing of the above step (10), and 500 mj / cm ² using an ultra-high pressure mercury lamp. Exposure. This was subjected to ultrasonic development with a chlorocene solution to form an opening serving as a via hole 13 having a diameter of 100 μm on the wiring board. Step (12): Next, the wiring board was exposed to light at about 300 mj / cm ² using an ultra-high pressure mercury lamp, and further subjected to heat treatment at 100 ° C. for 1 hour and at 150 ° C. for 3 hours. Through these processes, an interlayer insulating layer 12 having an opening having excellent dimensional accuracy corresponding to a photomask film was formed. Step (13): The surface of the interlayer insulating layer 12 was roughened by immersing the wiring board in chromic acid for 10 minutes. Further, after the neutralization, washing with water and hot water was performed to remove chromic acid from the wiring board. Step (14): Thereafter, the wiring board was immersed in a commercially available Pd-Sn colloid catalyst, and the Pd-Sn colloid was adsorbed on the inner wall surface of the opening and the surface of the roughened interlayer insulating layer 12.
Thereafter, heat treatment was performed at 120 ° C. for 30 minutes. Step (15): A plating resist 10 was formed by laminating a dry film photoresist on the wiring board and performing exposure and development. Step (16): Thereafter, the wiring board was immersed in a 37% aqueous formaldehyde solution as a reducing agent to activate Pd. At this time, the processing temperature is 40 ° C., and the processing time is 5 minutes. Next, the wiring board was immediately immersed in an electroless plating solution according to a conventional method, and kept in that state for 15 hours. Through the above steps, a thickness of about 35 μm, L / S = 7
A four-layer printed wiring board including the conductive circuit 11 of 5 μm / 75 μm was formed. Even though the inner layer had a through hole, the thickness of the upper layer became uniform, and no variation in impedance was observed. Further, even if the inner layer has a through hole, the pad becomes smooth, so that no failure occurred even when the IC was mounted. Also, there is no difficulty in quality control during mass production as seen in JP-A-62-173794.

Example 2 The same as Example 1, except that the filling material 14 was added to 60 parts by weight of a 50% acrylated product of a cresol novolak type epoxy resin (manufactured by Yuka Shell, trade name: Epicoat 180S) as a photosensitive resin. 40 parts by weight of a bisphenol A type epoxy resin (manufactured by Yuka Shell, trade name: E-1001)
15 parts by weight of diallyl terephthalate, 2-methyl-1-
A solution was prepared by mixing 4 parts by weight of [4- (methylthio) phenyl] 2-morpholinopropanone-1 (trade name: Irgacure-907, manufactured by Ciba-Geigy), and a ceramic plate was used as a gas-permeable substrate.

Example 3 The adhesive for electroless plating prepared in Example 1 was applied to a glass epoxy insulating substrate, cured by exposure and heating, roughened with a chromic acid solution, and then laminated with a dry film.
Exposure and development were performed to provide a plating resist 10. Further, a palladium catalyst core was applied and electroless plating was performed to form a conductor circuit 11 and a through hole 4. Next, using polyether sulfone (PES), which is a thermoplastic resin, as the filling paste, filling was carried out in the same manner as in Example 1 to form a four-layer printed wiring board.

Comparative Example 1 In Comparative Example 1, a polyethylene film was brought into close contact with a substrate, and a filling material was press-fitted to obtain a four-layer build-up wiring board in the same manner as in Example 1. However, air bubbles enter into the through-hole portion of the inner layer, which becomes a depression, and a recess is formed in the pad portion on the surface, so that the IC cannot be mounted. In addition, the depression on the through hole in the inner layer makes it difficult to control the thickness of the upper layer, and the variation in the thickness causes variations in impedance, resulting in failure.

Comparative Example 2 A polyethylene film was closely adhered to a through-hole substrate, and the filling material obtained in Example 1 was press-fitted. Then, methyl ethyl ketone was sprayed by spraying according to Japanese Patent Laid-Open No. Sho 62-173794. Bubbles were removed. However, it was confirmed that the filling material of the through holes partially flowed out.

[0032]

As described above, according to the present invention, not only can a build-up multilayer printed wiring board having excellent through-hole connection reliability be easily manufactured, but also mounting reliability can be ensured and impedance control can be performed. Can be easily realized.

[Brief description of the drawings]

FIGS. 1A to 1G are process diagrams of a four-layer printed wiring board according to a first embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal layer 2 Insulating plate 3 Through-hole 4 Through-hole 5 Japanese paper (air-permeable base) 6 Filling material receiver 7 Roll coater 8 Inner layer circuit 9 Uneven surface (Ni-P-Cu eutectic plating) 10 Plating resist 11 Conductor circuit 12 Layer Insulation layer 13 Via hole 14 Filling material

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5E314 AA25 AA26 AA27 AA41 AA42 CC01 FF01 FF08 GG12 5E317 AA21 AA24 BB02 BB12 CD27 CD32 GG09 5E346 AA06 AA12 AA15 AA32 AA43 AA51 CC04 CC08 CC32 DD03 GG19 GG19

Claims (3)

[Claims] 1. A base having a through hole for a through hole,
A conductor is formed on the inner wall of the through hole to form a substrate having a through hole, a filling material is filled in the through hole, and an interlayer insulating material layer is provided on both sides of the substrate. A multilayer printed wiring board characterized by forming a conductor circuit on the printed circuit board. 2. The multilayer printed wiring board according to claim 1, wherein the filling material is a thermosetting heat-resistant resin, a photosensitive heat-resistant resin, or a thermoplastic heat-resistant resin. 3. The multilayer printed wiring board according to claim 1, wherein the filler material contains a filler.