JP2003309360A - Multilayer printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multilayer printed wiring board, in which a through-hole is filled with paste-like fill and which is superior in surface smoothness without mixing bubbles. <P>SOLUTION: The through-hole is made in a substrate, a conductor is formed on the inner wall of the through-hole and the through-hole is made. The through- hole is filled with a filling material and an interlayer insulating layer is formed on the substrate. <P>COPYRIGHT: (C)2004,JPO

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 excellent in connection reliability of through holes and smoothness of a substrate surface.

[0002]

2. Description of the Related Art In recent years, with the miniaturization and modularization of electronic equipment, the printed wiring boards used in hybrid modules are required to have higher density. To meet such demands, double-sided (multi-layer) with through holes
Printed wiring boards are manufactured. When manufacturing a printed wiring board having a through hole, a tenting method is used in which a photosensitive dry film is used to etch a pattern to form a circuit. However,
This method has a drawback that the dry film is easily damaged at the through hole portion and the inner wall of the through hole is dissolved during etching. Further, there is a method of applying a liquid photosensitive resin liquid instead of the photosensitive dry film, but there is a problem that it is difficult to apply it uniformly on the substrate surface due to the existence of the through holes. Also,
When a board with through holes is used as the inner layer of a build-up multilayer wiring board, when the interlayer insulation material layer is provided, the through holes are dented and the layer thickness of the interlayer insulation material layer varies, making impedance control difficult. Therefore, there is a problem in that the mounting reliability of the IC is lowered when the recess is formed in the pad portion.

Due to the above problems, conventionally, a conductor is formed on the inner wall of a through hole for a through hole to form a through hole, 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 the paste-like filling material is filled, the paste is apt to be filled with air, and the surface layer of the filled material is hardened relatively easily, so that air bubbles escape. When the remaining filling material on the substrate surface is removed by polishing or the like, pits remain on the substrate surface. Also, if air is trapped in the filling material, it may be broken by thermal expansion when mounting an electronic component due to thermocompression bonding, etc., resulting in reduced heat resistance. Further, it tends to absorb moisture and has poor insulation. There was a problem.

Therefore, when filling the filling material,
Various methods for removing bubbles in the filling material have been developed. For example, in Patent Document 1, after filling the filling material into a through hole of a ceramic substrate, the filling material is brought into contact with a solvent to obtain the surface viscosity and the surface. By reducing the tension,
A method of removing bubbles is disclosed.

[0006]

[Patent Document 1] Japanese Patent Laid-Open No. 62-173794

[0007]

However, this method is
Since the viscosity and the surface tension of the surface of the filling material are reduced, the viscosity and the surface tension of the filling material must be controlled so that the filling material does not flow out, and it is difficult to control the quality during mass production.

[0008] As described above, it has been desired to develop a printed wiring board having a smooth surface by filling the through holes with a paste-like filling material without mixing air bubbles. As a result of intensive studies, the present inventors have found that the above-mentioned problems can be solved by using a breathable substrate.

[0009]

According to the present invention, a through hole for a through hole is provided in a substrate, a conductor is formed on the inner wall of the through hole to form a substrate having the through hole, and the through hole is filled with a filling material. At the same time, an interlayer insulating material layer is provided on the substrate, and a conductor circuit is further formed on the surface of the interlayer insulating material layer, which is a multilayer printed wiring board.

In the present invention, it is desirable that an air-permeable substrate is brought into close contact with one surface of a printed wiring board having a through hole, and a paste-like filling material is press-fitted and filled. The reason for this is that even if air bubbles are contained in the paste-like filling material, they will pass through the air-permeable substrate during press-fitting, and the filling material itself will not pass through the substrate. Is filled tightly with the filling material. For this reason, the surface smoothness of the substrate is excellent, and since the inner wall of the through hole is surely protected and is not dissolved during etching, the connection reliability of the through hole is improved.

In the present invention, the breathable substrate used is
Membranes or plates that allow air to permeate but not the filling material, such as fibrous films and porous substrates, are preferred.

The fibrous film is preferably paper such as filter paper or Japanese paper, and the porous substrate is preferably a ceramic plate or the like. The reason for this is that they are excellent in air permeability, facilitate the escape of air in the through holes, and have an effect of preventing the escape of the filling resin.

The paste-like filling material used in the present invention is preferably an insulating resin such as thermosetting heat-resistant resin, photosensitive heat-resistant resin or thermoplastic heat-resistant resin. For example, in the case of epoxy resin, Epicoat 828 is used. , 1001 (both are 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 pasty filling material depends on the coating method, but is preferably 1 to 10 Pa · s. The reason for this is that when the pressure is less than 1 Pa · s, the resin filled in the through holes soaks into the substrate, and as a result, the resin in the through holes becomes insufficient, resulting in depressions and resin loss. This is because bubbles in the material are difficult to escape and the leveling property is poor. To adjust the viscosity of the pasty filling material, it is preferable to use a solvent such as methyl ethyl ketone, methyl cellosolvesolve, butyl cellosolve, butyl cellosolve acetate, butyl carbitol, butyl cellulose, tetralin, dimethylformamide, normal methylpyrrolidone.

In the present invention, a roll coater, a suji, or the like is preferable as the means for press-filling the paste-like filling material. The pressure at the time of press-fitting is preferably 1 to 4 kg / cm ² . The reason for this is less than 1 kg / cm ² may resin does not fit completely filled, also recesses on the surface exceeds 4 kg / cm ² tend to occur.

After the paste-like filling material is press-filled, the paste-like filling material is dried and cured, and after drying and curing, unnecessary filling material is removed by a method such as polishing or sandblasting. It is desirable to make the surface flat.

In the present invention, as a method of forming the through hole, a conventional electroless plating or electrolytic plating can be performed. Copper, nickel, gold, etc. are preferably used for the plating.

In the present invention, various methods such as a subtractive method of etching a metal layer and an additive method of forming a conductive circuit by electroless plating can be used as a method of forming a conductive circuit. When the additive method is used, a printed wiring board can be manufactured by the following steps. (A) An adhesive layer for electroless plating, which will be described later, is formed and roughened on a substrate such as an insulating plate or a metal plate, and this is used as a substrate to form through holes for through holes, and then palladium or the like. The step of applying a catalyst nucleus, then forming a plating resist if necessary, and further forming a conductor circuit on the inner wall of the through hole and the surface of the substrate to produce a substrate having a conductor circuit and a through hole. (B) A step of bringing a breathable substrate into close contact or contact with one surface of the substrate having a through hole. (C) A step of press-fitting a paste-like filling material from the surface opposite to the surface on which the breathable substrate is brought into close contact or contact. (D) A step of 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 having metal layers on both sides is used as a substrate, through holes for through holes are formed in the substrate, electroless plating is performed by adding catalyst nuclei, conductors are provided in the through holes, and through holes are formed. Manufacturing a substrate having. (B) A step of bringing a breathable substrate into close contact or contact with one surface of the substrate having a through hole. (C) A step of press-fitting a paste-like filling material from the surface opposite to the surface on which the breathable substrate is brought into close contact or contact. (D) A step of curing the filling material. (E) A step of forming an etching resist and etching to form a conductor circuit. A step of removing the remaining filling material by polishing or the like may be adopted if necessary.

The multilayer printed wiring board thus obtained is provided with a through hole for a through hole in the base body, and a conductor is formed on the inner wall of the through hole to form a substrate having the through hole, and the through hole is filled with a filling material. With filling
An interlayer insulating material layer is provided on the substrate, and a conductor circuit is further formed on the surface of the interlayer insulating material layer to provide a multilayer printed wiring board. The multilayer printed wiring board of the present invention is preferably a double-sided (including, of course, multilayer) wiring board.

According to the present invention, the through-hole filling resin is prevented from slipping out and air is not mixed in the filling material, and such a printed board is used as an inner layer board to manufacture a build-up multilayer printed wiring board. Therefore, a multilayer printed wiring board having an excellent surface smoothness can be manufactured, and the mounting reliability and impedance control of electronic circuit components are facilitated.
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 inner layer manufactured by the additive or subtractive method, exposing and developing it to form an opening, and roughening the surface of the adhesive layer, electroless Plating is performed to form a conductor circuit on the surface of the adhesive layer and the opening, and the conductor circuit of the upper layer and the conductor circuit of the inner layer are electrically connected.

In the present invention, when the conductor circuit is manufactured by the additive method, a matrix, which is made of a resin which is hardly soluble in an acid or an oxidant, is used as an adhesive and is subjected to a curing treatment that is soluble in the acid or the oxidant. It is desirable that the heat-resistant resin powder is dispersed, and the heat-resistant resin powder has 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. Aggregated 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, 4) an average particle size of 2 10μ
It is desirable that the heat-resistant resin powder of m has at least one selected from the group consisting of heat-resistant resin powder having an average particle size of 2 μm or less and inorganic powder having an average particle size of 2 μm or less.

The adhesive layer can be provided with a roughened surface by roughening with an acid or an oxidizing agent. Even if the conductor circuit is formed by electroless plating, the interlayer insulating material layer and the conductor circuit are not separated from each other. This is because the adhesion can be improved. The resin of the matrix is preferably photosensitive. This is because a via hole can be formed by exposure and development by using a photosensitive resin. In the build-up multilayer wiring board, the adhesive serves as an interlayer insulating material layer. Regarding the anchor shape and anchor depth formed by such an adhesive layer, it is desirable that the surface roughness be within the range of 1 μm to 20 μm with fillers having different particle diameters. Sufficient adhesion strength can be obtained.

In the multilayer printed wiring board of the present application, it is preferable that the roughening layer formed of the electroless plating film provided at the interface between the conductor circuit and the interlayer insulating material layer is a eutectic compound containing copper, nickel and phosphorus. The reason for this is that the blackening reduction treated surface oxidizes the surface to form copper oxide on the surface and roughens the surface, but the strength of this roughened layer of copper oxide is low and it is destroyed by thermal shock. This is because delamination occurs, but the eutectic compound obtained by the eutectic plating of the present invention has high strength, so delamination due to thermal shock is less likely to occur, and heat cycle characteristics are improved. Further, since such a eutectic compound is mainly acicular crystals, it has a high effect as an anchor, and the conductor circuit and the interlayer insulating material layer can be brought into close contact with each other, so that the heat cycle characteristics are improved. Furthermore, after the blackening reduction treatment, the copper oxide is exposed to the surface, so that it is easily dissolved in an acid solution, which easily causes a so-called haloing phenomenon. Since it is formed in the above, it is not melted 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 respectively.
It is desirable to be about 2 wt%. This is because, in the above range, the crystals of the deposited film have a needle-like structure, and 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 for this is that if the thickness is 0.5 μm or less, the anchor effect is low, and if it is 5 μm or more, the surface roughness becomes too large.
On the contrary, the adhesion strength will decrease. 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 to each other through a via hole or a through hole. When connecting via a via hole, it is necessary that the roughening layer at the connection point be removed in advance or that no roughening layer be provided.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, Example 1 and Comparative Example 1 embodying the present invention will be described in detail with reference to the drawings.

Example 1 Manufacturing process (1) of the multilayer printed wiring board of Example 1
(9) will be described with reference to FIGS. Step (1): Double-sided copper-clad laminate with a drill bore of 0.2
A through hole 3 of mm was formed. After applying and activating the active catalyst on the entire surface, electroless plating was performed according to a conventional method to deposit copper on the inner wall of the through hole 3 to form the through hole 4. Step (2): Japanese paper 5 was placed on the laminated plate having the through holes 4 formed therein. Step (3): 60 parts by weight of phenol novolac type epoxy resin (made by Yuka Shell), 40 parts by weight of bisphenol A type epoxy resin (made by Yuka Shell) and 5 parts by weight of imidazole type curing agent (made by Shikoku Kasei) in butyl cell Dissolved in sorb acetate, based on 100 parts by weight of the solid content of this composition, 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 particle having a particle size of 5.5 μm. Mix in proportion, then knead with 3 rolls, add butyl cellosolve acetate further, solid content concentration 75%
A paste-like filling material 14 was prepared. According to JIS-K7117, the viscosity of this solution was measured at 20 ° C. for 60 seconds using a digital viscometer manufactured by Tokyo Keiki, and the rotation speed was 6 rpm, 5.2 Pa · s, and 60 rpm was 2.6 Pa · s.
s, and its SVI value (thixotropic property) is 2.
It was 0. Process (4): Surface pressure of 3 kg / c by the roll coater 7.
The filling material 14 was press-fitted into the through hole 4 at m ² . Step (5): The filling material 14 was dried, heated, and cured, and the excess filling material 14 was removed by polishing to be 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 a cupric chloride aqueous solution to obtain a double-sided printed board (inner layer circuit 8). Since the through hole 4 is protected by the filling material 14, it was not etched. Further, neither bubbles nor dents were found in the filled through holes 4. Step (8): After degreasing the substrate, applying a soft etching sulfuric acid active catalyst, and activating the substrate, plating is performed in the next electroless plating bath, and a Ni-P-Cu eutectic 1 μm thick uneven surface is formed. Got 9. 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 novolac type epoxy Resin (made by Yuka Shell, trade name: Epicoat 180S) 50% acrylate 60 parts by weight, bisphenol A type epoxy resin (made by Yuka Shell, trade name: E-1001) 40 parts by weight, diallyl terephthalate 15 parts by weight, 2-methyl-
1- [4- (methylthio) phenyl] 2-morpholinopropanone-1 (manufactured by Ciba Geigy, trade name: Irgacure-907) 4 parts by weight, epixy resin fine powder having a particle size of 5.5 μm (manufactured by Toray) 10 Weight part and particle size are 0.5μ
25 parts by weight of fine powder of epoxy resin (manufactured by Toray) of m was compounded. Then, an appropriate amount of butyl cellosolve was added to this mixture and stirred with a homodisper stirrer to prepare an adhesive varnish.

Step (10): After applying the above-mentioned 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 have a thickness of 50.
A photosensitive adhesive layer (interlayer insulating layer) 12 having a thickness of μm was formed. Step (11): Next, a photomask film in which a black circle having a diameter of 100 μm and a punching cut portion is printed in black is adhered to the wiring board subjected to the treatment of the step (10), and 500 mj / cm ^{2 is} applied by an ultra-high pressure mercury lamp. Exposed. This was ultrasonically developed with a chlorocene solution to form an opening to be a via hole 13 having a diameter of 100 μm on the wiring board. Step (12): Next, the wiring board was exposed by an ultra-high pressure mercury lamp at about 300 mj / cm ² , and further heat-treated at 100 ° C. for 1 hour and 150 ° C. for 3 hours. By these treatments, the interlayer insulating layer 12 having an opening excellent in dimensional accuracy and equivalent to a photomask film was formed. Step (13): Then, the surface of the interlayer insulating layer 12 was roughened by immersing the wiring board in chromic acid for 10 minutes. Further, after neutralization, the substrate was washed with water and hot water to remove chromic acid from the wiring board. Step (14): Then, the wiring board was immersed in a commercially available Pd-Sn colloid catalyst to adsorb the Pd-Sn colloid on the inner wall surface of the opening and the roughened surface of the interlayer insulating layer 12.
Then, it heat-processed at 120 degreeC for 30 minutes. Step (15): A dry film photoresist was laminated on the wiring board and exposed and developed to form a plating resist 10. Step (16): After that, 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. Then, the wiring board was immediately immersed in an electroless plating solution according to a conventional method, and kept in that state for 15 hours. By going through each of the above steps, a thickness of about 35 μm, L / S = 7
A four-layer printed wiring board having a conductor circuit 11 of 5 μm / 75 μm was formed. Even if the inner layer had through holes, the film thickness of the upper layer was uniform, and no variation in impedance was observed. Further, even if the inner layer had a through hole, the pad was smooth, so that no defect occurred even when the IC was mounted. Further, there is no difficulty in quality control during mass production as seen in JP-A-62-173794.

Example 2 Almost the same as in Example 1, except that the filling material 14 was cresol novolac type epoxy resin (made by Yuka Shell, trade name: Epicoat 180S) 50% acrylate 60 parts by weight. , Bisphenol A type epoxy resin (made by Yuka Shell, trade name: E-1001) 40 parts by weight,
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 (manufactured by Ciba-Geigy, trade name: Irgacure-907), and a ceramic plate was used as a breathable substrate.

Example 3 A glass epoxy insulating substrate was coated with the adhesive for electroless plating prepared in Example 1, cured by exposure, heating, roughened with a chromic acid solution, and then laminated with a dry film,
After exposure and development, a plating resist 10 was provided. Further, a palladium catalyst nucleus was applied and electroless plating was performed to form the conductor circuit 11 and the through hole 4. Then, using a polyether sulfone (PES) which is a thermoplastic resin as a filling paste, filling was performed 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 the substrate and a filling material was press-fitted to obtain a 4-layer build-up wiring board in the same manner as in Example 1. However, air bubbles enter 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 could not be mounted. Further, due to the depression on the through hole of the inner layer, it becomes difficult to control the film thickness of the upper layer, and the variation of the film thickness causes the variation of impedance, resulting in a defect.

Comparative Example 2 A polyethylene film was brought into close contact with a through-hole substrate, the filling material obtained in Example 1 was press-fitted, and then methyl ethyl ketone was sprayed to spray the filling material in JP-A-62-173794. Bubbles were removed. However, it was confirmed that the filling material for the through holes partially flowed out.

[0033]

As described above, according to the present invention, not only a multilayer printed wiring board having excellent connection reliability of through holes can be easily manufactured, but also mounting reliability is ensured and impedance control is facilitated. realizable.

[Brief description of drawings]

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

[Explanation of symbols]

1 metal layer 2 insulating plate 3 through holes 4 through holes 5 Japanese paper (breathable substrate) 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 Interlayer insulation layer 13 via hole 14 Filling material

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Claims (3)

[Claims] 1. A through hole for a through hole is provided in a base,
A conductor is formed on the inner wall of the through hole to form a substrate having a through hole, the through hole is filled with a filling material, an interlayer insulating material layer is provided on the substrate, and a conductor is formed on the surface of the interlayer insulating material layer. A multilayer printed wiring board having a circuit formed therein. 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 filling material contains a filler.