JPH0380592A - Manufacture of printed wiring board - Google Patents

Abstract

PURPOSE:To obtain the title item with a high pattern precision easily and at low cost under improved reliability of a high-density wiring board by performing electroless plating through a lead obtained by electroless plating, making thick a conductor pattern, and by insulating a lead for electroless plating and a formed conductor pattern. CONSTITUTION:Ultraviolet rays exposure is made through a mask film where a desired conductor circuit pattern and a lead for electroless plating are drawn on a substrate 1 where an adhesive material layer 2 is clad and an image is baked, developed, and a resist for plating 3 is formed. After that, electroless plating treatment is performed and one part 4 constituting a conductor pattern, a lead for electroless plating 6 which is formed at the outer periphery part of the substrate, and a lead wire 5 connecting the pattern 4 and the lead 6 are formed by thin plating. Then, after connecting an input terminal 7 to the electroless plating lead 6, electroless plating is performed, thus forming a conductor pattern exceeding 2mum. Then, a metal layer at the outer periphery part of the substrate is cut and the part of the electroless plating lead 6 is removed, thus obtaining a printed wiring board.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a printed wiring board, and particularly to a method for manufacturing a printed wiring board, in which a conductor pattern is formed relatively inexpensively and quickly by a so-called additive process. Regarding the method.

[Prior art and problems]

In recent years, with the advancement of electronic industry technology, electronic equipment has become smaller and smaller.
Speeds are increasing. Along with this, printed wiring boards and
Even in wiring boards on which SI is mounted, higher density and higher reliability due to fine patterns are required.

As a method that can meet these demands, a so-called additive process has recently been proposed in which a conductor pattern is formed by electroless plating.

By the way, since the additive process is a method of performing electroless copper plating, it is costly and time consuming, and also has the following problems. In other words, since the plating solution used is strongly basic, a plating resist that can withstand such a plating solution for a long time is required.
There are few such products, making it difficult to select one and increasing the cost.

As a means to solve such problems, conventional methods of forming conductor patterns by electrolytic plating have been used, for example, (
1) First, after providing a through hole for a through hole in a copper-clad laminate, electroless plating is applied to the entire surface, and then a plating resist is coated, electrolytic plating is performed to form a conductor pattern, and then the plating resist is coated with electrolytic plating. (2) Electroless plating is applied to the surface of the insulating plate on which the adhesive layer for electroless plating is formed, and then the plating resist is applied. After forming, a conductor pattern is formed by electrolytic plating,
A method has been proposed in which the plating resist is then peeled off and then etched to remove the copper between the patterns.

However, these methods require many steps and are complicated.
Since etching processing is required, it is difficult to achieve high density, and there are also problems such as poor pattern accuracy, and in the end, this method diminishes the advantages of an additive process.

As explained above, in the conventional method, it is difficult to form a conductor pattern by electrolytic plating without impairing the merits of the additive process.

An object of the present invention is to complete a printed wiring board manufacturing method that can overcome the above-mentioned problems faced by the prior art.

[Means to solve the problem]

In order to achieve the above-mentioned object, the present inventors first perform electroless plating to form a thin lead for electrolytic plating together with a part of the conductor pattern. They then developed a method in which electrolytic plating is performed by passing a current through the electrolytic plating leads formed at that time, thereby forming a final conductor pattern of a predetermined thickness.

・That is, the present invention provides at least the following (a) to (
Step c): (a) First, an adhesive layer for electroless plating is formed on the substrate, a plating resist is formed, and then a part of the conductor pattern is formed by electroless plating. (b) performing electrolytic plating via the leads obtained by electroless plating in step (a), thereby forming the already formed thin conductor pattern; A printed wiring board characterized by going through the following steps: (c) insulating the electrolytic plating lead from the conductor pattern formed in step (b). This is a manufacturing method.

In the step, it is preferable that a part of the thin conductor pattern formed by electroless plating and the electrolytic plating lead each have a thickness of 2 μm or more.

The electrolytic plating lead is preferably a metal layer formed along the outer periphery of the substrate and/or a band formed within the substrate.

The adhesive layer for electroless plating is made by dispersing heat-resistant fine powder that is soluble in oxidizing agents and cured in advance into a heat-resistant resin that becomes poorly soluble in oxidizing agents through curing treatment. It is preferable that the material is formed by curing the material and then treating it with an oxidizing agent.

[For production]

In the present invention, an adhesive layer for electroless plating is first formed on a substrate (laminate), then a plating resist used for electrolytic plating is provided, and then a thin conductor pattern forming a part of the conductor pattern is formed. At the same time, electrolytic plating leads electrically connected to this conductor pattern are formed by electroless plating.

Next, by applying current to the electrolytic plating lead to perform electrolytic plating, a thin film (
#2 μm) on the conductor pattern,
Furthermore, a conductive pattern thickened to a predetermined thickness (approximately 10 μm to 35 μm) is formed. Thereafter, the electrolytic plating lead and the conductive pattern are insulated.

In this manufacturing method, most of the conductor pattern is formed by electrolytic plating, so it is possible to make the conductor pattern at a lower cost and in a shorter time than in the conventional case where the entire conductor pattern is formed using only electroless plating. Can be formed in time. Furthermore, this method does not require much consideration of the base resistance of the plating resist, and therefore has the advantage that a low-cost plating resist can be used.

It is desirable that the thickness of the thin conductor pattern and the thin lead for electrolytic plating, which are formed in advance by electroless plating, are each 2 μm or more. The reason for this is that if the thickness of the electroless plated film is less than 2 μm, sufficient electrical conduction cannot be achieved and good electrolytic plating treatment cannot be performed.

The electroless plating treatment may be any of electroless copper plating, electroless nickel plating, electroless tin plating, electroless gold plating, and electroless silver plating, but in particular, electroless copper plating may be used. Plating treatment is optimal.

Further, the electrolytic plating treatment includes electrolytic copper plating method, electrolytic nickel plating method, electrolytic tin plating method, electrolytic gold plating method,
Any of the electrolytic silver plating methods may be used, and among them, electrolytic copper plating is a preferable method.

Note that in addition to the electrolytic plating described above, a different type of electrolytic plating may be performed or a solder coating may be performed. In particular, by performing electrolytic copper plating, followed by electrolytic nickel plating and electrolytic gold plating, it is possible to form conductive patterns that adhere well to gold wires used in COB (chimp-on-board) boards, etc. .

The electrolytic plating lead in this invention is, for example, a metal layer formed on the outer periphery of a substrate, or a pad formed within the substrate. The reason why the electrolytic plating lead is shaped like this is to minimize the loss of the effective area of the substrate due to the electrolytic plating lead and to facilitate the removal of the electrolytic plating lead. The metal layer, pad, etc. are electrically connected to the conductive pattern through lead wires, and when performing electrolytic plating, current may be passed through the electrolytic plating leads. Note that the metal layer formed on the outer periphery of the substrate is preferably formed in an annular shape.

Next, as a method of insulating the electrolytic plating lead and the conductor pattern in the present invention, there is a method of cutting the lead wire connecting the electrolytic plating lead and the conductor pattern, or peeling off the electrolytic plating lead. desirable. As a method for cutting the lead wire and separating #J from the lead for electrolytic plating, it is desirable to cut by canting, punching, cutting, or dissolving and peeling by etching.

In particular, it is desirable that the metal layer of the electrolytic plating lead, which is formed along the outer periphery of the substrate, be cut during contour processing. Further, it is preferable that the pads serving as leads for electrolytic plating be removed by punching, cutting, or etching, or by removing unnecessary portions of the lead wires connected to the conductor pattern to use as mounting pads. .

Next, the adhesive layer for electroless plating used in the present invention is made of heat-resistant fine powder that is soluble in oxidizing agents and has been hardened in advance, and becomes hardly soluble in oxidizing agents through hardening treatment. It is desirable to form the material by curing a material dispersed in a heat-resistant resin and then treating it with an oxidizing agent. For example, a mixture of heat-resistant resin particles with an average particle size of 2 to 10 μm and heat-resistant resin fine powder with an average particle size of 2 μm or less in a heat-resistant resin that is poorly soluble in oxidizing agents, or a mixture of heat-resistant resin particles with an average particle size of 2 to 10 μm or less The average particle size is 2μ on the surface of the heat-resistant resin particles.
Pseudo-particles formed by adhering at least one of heat-resistant resin fine powder with a particle size of 2 μm or less or inorganic fine powder with an average particle size of 2 μm or less, or agglomerated particles with an average particle size of 2 to 10 μm. In other words, it is preferable that the adhesive layer is formed by curing a material containing heat-resistant particles soluble in an oxidizing agent and then treating it with an oxidizing agent. . This adhesive layer has a surface with a large number of anchors formed thereon due to the difference in solubility to the oxidizing agent, and can improve the adhesion strength of the plating film, such as beer strength and pull strength.

The oxidizing agent used in forming the adhesive layer includes:
Chromic acid, chromate, permanganate, ozone, etc. can be used, and as the resin constituting the heat-resistant particles, any resin selected from epoxy resin, polyester resin, and bismaleimide-triazine resin can be used. At least one type of resin can be used, and among them, epoxy resin is preferred. Further, as the inorganic fine powder that is soluble in an oxidizing agent, for example, calcium carbonate is used.

〔Example〕

Example 1 (1) Hensiel mixer (manufactured by Mitsui Miike Kakoki, F
Epoxy resin particles (manufactured by Toshi,
Trepearl EP-B, average particle size 3.9 pm) 200
In an acetone solution, epoxy resin (manufactured by Mitsui Petrochemicals, trade name TA-1800) was dissolved at a ratio of 30 g to 11 g of acetone in an epoxy resin particle suspension prepared by dispersing 51 g of acetone in acetone. , epoxy resin powder (
Made by Toshi, Trevor EP-B.

The epoxy resin powder was attached to the surface of the epoxy resin particles by dropping a suspension in which 300 g (average particle size: 0.5 μm) was dispersed, and after the acetone was removed, the so-called epoxy resin was heated to 150°C. We created pseudo-particles of resin. The epoxy resin pseudoparticles had an average particle size of 4.3 μm, and about 75% by weight existed within a range of ±2 μm around the average particle size.

(2) Epoxy resin pseudoparticles 5 prepared in (1) above
0 parts by weight, phenol novolac type epoxy resin (manufactured by Yuka Shell, trade name E-154) 60 parts by weight, bisphenol A epoxy resin (manufactured by Yuka Shell, trade name E-154)
-1001) and 4 parts by weight of an imidazole curing agent (manufactured by Shikoku Kasei Co., Ltd., P4MH2), butyl carpitol was added, and the viscosity was adjusted to 120 cp using a homodisper disperser to obtain an adhesive solution. Ta.

(3) Therefore, after applying the adhesive solution obtained in the step (2) to a glass polyimide substrate l (manufactured by Toshiba Chemical Co., Ltd., trade name: Toshiba Durite Laminated Board-EL),
The adhesive layer 2 was dried and cured at 150° C. for 1 hour and then at 150° C. for 5 hours to form an adhesive layer 2 with a thickness of 20 μm.

(4) The substrate 1 from which the adhesive layer 2 obtained in step (3) has been removed is immersed in an oxidizing agent consisting of 500 g of chromic acid/It aqueous solution for 15 minutes at 70°C to immerse the surface of the adhesive layer 2. After roughening, neutralize solution (manufactured by Sibley, trade name:
PN-950) and washed with water.

(5) A palladium catalyst (manufactured by Sibley, trade name: Catabodisoto 44) is applied to the substrate 1 on which the surface of the adhesive layer 2 obtained in step (4) has been roughened to activate the surface of the adhesive layer 2. turned into

(6) Place a photosensitive dry film on the substrate 1 ξ
The film was exposed to ultraviolet light through a mask film on which a desired conductor circuit pattern and leads for electrolytic plating had been drawn, and the image was printed. Then, it was developed with a 5% sodium carbonate solution to form a plating resist 3.

(7) By immersing it in an electroless copper plating solution having the composition shown in Table 1 for 30 minutes and performing electroless plating treatment, flash plating (thin plating) is performed to form a 2 μm thick conductor pattern. A portion 4, an electrolytic plating lead 6 formed on the outer periphery of the substrate, and a lead wire 5 connecting the pattern 4 and the lead 6 were formed.

(8) After connecting the input terminal 7 to the electrolytic plate 6, apply current and conduct electrolytic plating for 70 minutes under the conditions shown in Table 2.
This was carried out for a minute to form a conductor pattern with a thickness of 30 μm.

Table 2 Electrolytic plating conditions (9) The outer periphery of the board was cut to remove 6 electrolytic plating leads to obtain a printed wiring board.

Example 2 (1) Epoxy resin particles (Trepar EP- manufactured by Toshi)
B, average particle size 0.5 μm) was charged into a hot air dryer, and 1
The mixture was heat-treated at 80° C. for 3 hours to form a cohesive bond. The aggregated and bonded epoxy resin particles were dispersed in acetone, crushed in a ball mill for 5 hours, and then classified using an air classifier to produce aggregated epoxy resin particles. The average particle size of the epoxy resin aggregated particles was about 3.5 μm, and about 68% by weight existed within a range of ±2 μm around the average particle size.

(2) 50 parts by weight of the epoxy resin pseudoparticles prepared in step (1) above, phenol novolac type epoxy resin (
Yuka Shell Co., Ltd., trade name E-154) 60 parts by weight, bisphenol A type resin (Yuka Shell Co., Ltd., E-1001)
40 parts by weight, imidazole curing agent (Shikoku Kasei, 2P4
Butylcarpitol was added to 4 parts by weight of MH2) to prepare an adhesive solution.

(3) Using the adhesive solution prepared in step (2), perform the treatments shown in steps (3) to (6) of Example 1, and perform electroless plating to a thickness of 3 μm, A portion 4 of the conductor pattern and a band 9 serving as a lead for electroless plating were formed at the center of the substrate 1.

(4) Next, a current was applied to the pad 9 for electrolytic plating, and electrolytic copper plating was performed under the conditions shown in Table 2 to form a conductor pattern 8 with a thickness of 35 μm.

(5) After performing puff polishing to smooth the substrate surface, the electrolytic plating pad 9 was removed by cutting using a drill to obtain a printed wiring board.

Example 3 (1) 60 parts by weight of phenol novolac type epoxy resin (manufactured by Yuka Shell, E-154), bisphenol A
40 parts by weight of type epoxy resin (Yuka Shell E-1001), imidazole curing agent (Shikoku Kasei, 2P4MH2)
) 4 parts by weight, coarse particles for anchor formation, 10 parts by weight of epoxy resin powder (Torepar EP-B, average particle size 3.9 μm, manufactured by Toshi) as fine powder, and 10 parts by weight of epoxy resin (Torepar EP-B, manufactured by Toshi). B, average particle size 0.5 μm)
Adding butylcarpitol to 25 parts by weight,
An adhesive solution was prepared.

(2) After forming an adhesive layer on both sides of the substrate 1 by the same method as step (3) of Example 1, the process of Example 1 (
Roughen the adhesive layer 2 by the method shown in 4),
A roughened surface 2' was formed.

(3) A through hole 10 for forming a through hole was formed using a drill.

(4) A palladium catalyst (manufactured by Sibley, trade name: CATABODISOTO 44) was applied onto the substrate 1 to activate the roughened surface 2' of the adhesive layer 2.

(5) Plating resist 3 is formed on both sides of the substrate 1 by the method of step (6) of Example 1, and then electroless copper plating is applied to a thickness of 3 μm by the method of step (7>) of Example 1. A conductor pattern 4, a lead wire 5, and a pad 9 as a lead for electrolytic plating were formed.

(6) A current was applied to the lead pad 9 and electrolytic copper plating was performed under the conditions shown in Table 2 to form a 30 μm thick conductor pattern 8 and through hole 11.

(7) The pad 9 was removed by punching to obtain a printed wiring board.

Example 4 This example is basically the same as Example 2, but in order to remove the pads as leads for electrolytic plating, a photosensitive dry film (manufactured by DuPont, trade name: Riston 10) was used.
51) was laminated and exposed and developed to form an etching resist 12 on the parts other than the pad 9, and the electrolytic plating lead pad 9 was dissolved and removed using a cupric chloride etching solution. Then, the etching resist was removed with methylene chloride to obtain a printed wiring board.

Example 5 In this example, after processing steps (1) to (8) of Example 1, nickel plating 13 was applied, and then gold plating 14 was applied. Thereafter, the electrolytic plating lead 6 was cut, and the plating resist was peeled off using methylene chloride to create a printed wiring board.

Ni/Au plated substrates improve the adhesion between the conductor pattern and the gold wire when performing wire bonding using gold wire, etc., making it suitable for COB (chip on board).
It can be suitably used as a substrate.

Regarding the implementation results; Table 3 shows the time required to form conductor patterns for printed wiring boards manufactured by the methods described in Examples 1 to 5 above. For comparison, an equivalent printed wiring board manufactured using the conventional additive method is also shown.

Furthermore, the pattern accuracy (deviation of pattern width from the design value) of the printed wiring boards obtained in Examples 1 to 5 was ±3 μm.
The pattern accuracy was about the same as that of the additive method. By the way, the pattern accuracy of the subtractive method is ±(20 to 40) μm, compared to the conventional technology (1> or (2)
), it is ±(10-20) μm,
It was found that the printed wiring boards obtained through the steps of each of the above-mentioned Examples had superior pattern accuracy compared to the conventional technology. In addition, in each example, the manufacturing cost per 1 m2 of printed wiring board is compared to the conventional additive method.
It was possible to reduce the amount by about 10 to 15%.

〔Effect of the invention〕

As explained above, the present invention enables high-density wiring boards to be easily manufactured with high reliability, and is effective in manufacturing high-pattern-accuracy boards at low cost.

[Brief explanation of drawings]

Figures 1 (a) to (f) are explanatory diagrams of the manufacturing process in Example 1. Figures 2 (a) to (f) are explanatory diagrams of the manufacturing process in Example 2. Figure 3 (a) - (f) are explanatory diagrams of the manufacturing process in Example 3, Figures 4 (a) to (g) are explanatory diagrams of the manufacturing process in Example 4, and Figures 5 (a) to (h) are FIG. 6 is an explanatory diagram of the manufacturing process in Example 5. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Adhesive layer, 2'... Roughened surface, 3... Plating resist, 4... Electroless plated conductor pattern, 5... Lead wire, 6...・Lead for electrolytic plating, 7...Terminal for current input, 8...Conductor pattern, 9...Pad for electrolytic plating, 0...Through hole for through hole 1...Through hole, 2... - Etching resist, 3...nickel plating film, 4...gold plating film.

Claims (4)

[Claims] 1. When manufacturing printed wiring boards, (a) first form an adhesive layer for electroless plating on the board, then form a plating resist, and then apply electroless plating to partially remove the conductor pattern. a step of forming leads for electrolytic plating at the same time as the shaping; (b) performing electrolytic plating via the leads obtained by electroless plating in step (a), thereby forming the already formed thin conductor pattern; (c) insulating the electrolytic plating lead from the conductor pattern formed in step (b). Method of manufacturing the board. 2. The manufacturing method according to claim 1, wherein in the step (a), the part of the thin conductor pattern formed by electroless plating and the electrolytic plating lead each have a thickness of 2 μm or more. . 3. 3. The manufacturing method according to claim 1, wherein the electrolytic plating lead is a metal layer formed along the outer periphery of the substrate and/or a pad formed within the substrate. 4. The adhesive layer for electroless plating is made by dispersing heat-resistant resin fine powder, which has been cured in advance and is soluble in oxidizing agents, into a heat-resistant resin that becomes poorly soluble in oxidizing agents through curing treatment. The manufacturing method according to any one of claims 1 to 3, wherein the material is hardened and then treated with an oxidizing agent.