JPH01251784A - Manufacture of wiring board - Google Patents

Abstract

PURPOSE:To suppress insulation degradation due to electric erosion by including a material having small ingredient migration due to electric fields between copper which is a wiring conductor and an insulation board. CONSTITUTION:An adhesive layer contained a catalyzer for electroless plating is formed on the surface of an insulating board containing a catalyzer for electroless plating. A hole to be used as a through hole is bored. A resist for electroless plating is formed on a portion except the through hole and a portion to become a circuit section. It is immersed in a chemically roughening liquid and the surface of the portion where resist for electroless plating is not formed is selectively roughened. As a first metal layer, a layer of a combination of one or more kinds selected from among electroless nickel alloys, electroless cobalt alloys, electroless palladium and electroless gold is formed on a portion where resist for electroless plating is not formed. It is immersed in an electroless copper plating and a copper plating layer is formed on the first metal layer.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an electroless plating method with excellent electrolytic corrosion resistance.

(Prior art) As an economically superior manufacturing method for wiring boards, an adhesive layer containing an electroless plating catalyst such as palladium is formed on the surface to deposit electroless plating. If a resist for electroless plating is applied to parts of an insulating plate containing a catalyst for electroless plating other than the parts that should become circuit parts, the surface of the parts where no resist is formed is immersed in a chemical roughening solution such as chromic acid. There is a so-called additive method in which a circuit pattern is formed by selectively roughening the material and immersing it in an electroless plating solution.

(Problem to be Solved by the Invention) In recent years, as electronic devices have become smaller and lighter, wiring boards are required to have higher wiring density. The spacing between holes is being narrowed, and the width of conductors for wiring is being narrowed. In such a high-density wiring board, conductors with different potentials are in close proximity, and over a long period of time, ions are generated in the area between the conductors with different potentials on the surface of the insulating board that supports the conductors. Under humid conditions, dendritic copper compounds called dendrites are formed, either due to the migration of copper due to sexual impurities or due to the effects of various processing solutions in the additive manufacturing process of wiring boards. There is. This dendrite gradually grows under similar conditions and eventually leads to a short circuit between the conductors.

Therefore, in the conventional additive method, it is not possible to reduce the distance between conductors to 0.15 mm or less, and in order to increase the density of wiring, only the width of the conductor must be reduced.
This has been an obstacle to increasing wiring density.

The present invention provides an electroless plating method that is excellent in suppressing insulation deterioration due to electrolytic corrosion.

(Means for Solving the Problems) The present invention is a method for manufacturing a wiring board, which includes the steps shown below.

a. An adhesive layer containing a catalyst for electroless plating is formed on the surface of an insulating substrate containing a catalyst for electroless plating.

b. Drill a hole that will become a through hole.

c. A resist for electroless plating is formed in areas other than the through holes and the portions that will become circuit parts.

d. Immerse in a chemical roughening solution to selectively roughen the surface where the electroless plating resist is not formed.

e. As the first metal layer in areas where the resist for electroless plating is not formed, one or a combination of two or more of electroless nickel alloy, electroless cobalt alloy, electroless palladium, or electroless gold is used. form a layer.

f. Immerse in electroless copper plating solution to form a copper plating layer on the first metal layer.

That is, in the present invention, the problem related to dendrites is solved by interposing a substance whose components are less likely to migrate due to an electric field between copper, which is a wiring conductor, and an insulating substrate.

In step a, insulating substrates that can be used in the present invention include paper-based phenolic resin laminates, paper-based epoxy resin laminates, glass cloth epoxy resin laminates, or glass cloth polyimide resin laminates. , an insulating substrate containing palladium, platinum, rhodium, etc., which are catalysts for electroless plating, is used in this resin. As a commercially available product, LE
-168, LE-144 (Hitachi Chemical Co., Ltd., trade name), etc.

Adhesives include those whose main components are NBR, those whose main components are NBR and chlorosulfonated polyethylene,
Alternatively, epoxy resin as a main component can be used, which contains palladium, platinum, rhodium, etc. as a catalyst for electroless plating, and is mixed with zirconium silicate, silica, calcium carbonate, aluminum hydroxide, etc. as a filler. You can also use the

In the process, any device, such as a punch or drill, which is normally used for making holes in wiring boards, can be used to form the holes that will become through holes.

The resist for electroless plating formed in Step C includes an ultraviolet curable resist film made of a photocurable resin, an ultraviolet curable resist ink, a thermosetting resist ink, etc. that can be applied by screen printing. Any chemical solution and usage conditions used during the process, such as the electroless nickel plating solution, copper plating solution, and its pretreatment solution described below, can be used as long as it does not cause peeling or the like. can.

In step d, the roughening liquid that selectively roughens the surface of the portion where the resist is not formed is a chemical roughening liquid that can be normally used in manufacturing additive method wiring boards, such as a chromic acid-sulfuric acid mixture. liquid, chromic acid-tracebe acid mixed liquid, etc. can be used.

In step e, the electroless plating solution for forming the first metal layer includes nickel, nickel/tungsten alloy, nickel/cobalt alloy, cobalt, cobalt/
There is no particular limitation as long as it can plate tungsten alloy, palladium, or gold. For example, in the case of nickel, a plating solution containing phosphorus or boron using ordinary hypophosphite as a reducing agent is commercially available. As products, Blue Shuma (Nippon Kanizen Co., Ltd., trade name), Top Nicolon (Okuno Pharmaceutical Co., Ltd., trade name), Nimden (Kamimura Industries Co., Ltd., trade name), etc. can be used. In addition, it is preferable that the thickness of the palladium or gold plating layer is 0.5 to 5 μm from the viewpoint of uniformity of the plating thickness and thickness of the finished wiring board, and for other metals, the same reason applies. It is preferable to set it as 0 degrees 5-10 micrometers.

In step f, the electroless copper plating solution used for copper plating on the first metal layer is not particularly limited, and CC-41 plating solution (Hitachi Chemical Co., Ltd.,
Ordinary electroless plating solutions such as (trade name) can be used.

(Function) Copper dendrites are a phenomenon in which between conductors with a potential difference, the copper conductor with a higher potential dissolves, ions move to the lower potential, and precipitation occurs in the conductor with a lower potential. By interposing the first metal layer, which is a substance whose components are less likely to migrate due to an electric field, at the interface, it is possible to prevent insulation deterioration due to electrolytic corrosion when a voltage is applied between wiring conductors on the surface of the insulating substrate.

Example 1 A glass cloth base epoxy resin laminate LE-144 (trade name, Hitachi Chemical Co., Ltd.) containing palladium chloride as a catalyst for electroless plating was coated with acrylonitrile butadiene rubber using an adhesive containing the same palladium chloride. An adhesive containing alkylphenol resin, epoxy resin, silica as an inorganic filler, and zirconium silicate as main components in a solvent was applied, dried, and cured by heating to form an adhesive layer.

Next, after punching holes at predetermined positions using a punch press, Photec SR-'3000 (trade name, Hitachi Chemical Co., Ltd.), a photoresist film for electroless plating, is laminated using a vacuum laminator to form holes in areas that will not form a circuit. The unexposed portions were developed and removed to form a resist. At this time, the circuit width and the spacing between the conductors were both 0.15 mm.

The insulating plate on which the resist was formed was heated with 55 g of Cr and 210 mj of concentrated sulfuric acid! The sample was immersed for 10 minutes in a solution of chromic acid mixture diluted with water to make 11 at a temperature of 55° C., and the portion that would become the circuit portion was selectively roughened chemically, washed with water, and neutralized.

This insulating plate was immersed in the following electroless nickel/tungsten alloy plating solution for 60 minutes to form an alloy plating layer of about 2 μm.

〔composition〕

Nickel sulfate: 1g/l Sodium tungstate: 35g/l Sodium citrate
:20g/1 Sodium hypophosphite :LOg/
l [Conditions] pH: 9.8 Solution temperature: 93°C Next, after washing with water, CC-4 was used as an electroless plating solution.
1 Plating solution (Hitachi Chemical Co., Ltd., trade name) at 70℃
After depositing a copper plating of about 20 μm, a solder resist was applied by screen printing to the surface of the substrate other than the through holes and cured by heating to obtain a test wiring board.

Example 2 The adhesive used in Example 1 was applied to a glass cloth epoxy resin laminate LE-168 (trade name, Hitachi Chemical Co., Ltd.) containing palladium chloride, and cured by heating to obtain an insulating substrate.

After that, a hole was drilled at a predetermined position using a high-speed drill machine, and Photec 5R-3000 (trade name, Hitachi Chemical Co., Ltd.), which is a photoresist film for electroless plating, was laminated with a vacuum laminator, and exposed and developed. Then, a resist was formed on the parts that would not form a circuit.

The insulating plate on which the resist was formed was immersed for 10 minutes in a solution of chromic acid mixture (11) made by diluting 55 g of Cr and 210 ml of concentrated sulfuric acid with water at a temperature of 55°C to selectively chemically remove the parts that would become the circuits. It was roughened, washed with water, and neutralized.

This insulating substrate was immersed in the following electroless cobalt/nickel alloy plating solution for 50 minutes to form an alloy plating layer of about 10 μm.

(Composition) Cobalt chloride: 30g/It Nickel chloride: 30g/L Sodium glycolate:
100g/A1 Sodium hypophosphite: 22g/
i! [Conditions] p)l: 4.5-5.0 Solution temperature: 92°C Next, after washing with water, CC-4 was used as an electroless plating solution.
1 Plating solution (Hitachi Chemical Co., Ltd., trade name) at 70℃
After depositing a copper plating of about 20 μm, a solder resist was applied by screen printing to the surface of the substrate other than the through holes and cured by heating to obtain a test wiring board.

Example 3 The adhesive used in Example 1 was applied to a glass cloth epoxy resin laminate LE-168 (trade name, Hitachi Chemical Co., Ltd.) containing palladium chloride, and cured by heating to obtain an insulating substrate.

After that, a hole was drilled at a predetermined position using a high-speed drill machine, and Photec 5R-3000 (trade name, Hitachi Chemical Co., Ltd.), which is a photoresist film for electroless plating, was laminated with a vacuum laminator, and exposed and developed. Then, a resist was formed on the parts that would not form a circuit.

The insulating plate on which the resist was formed was immersed for 10 minutes in a solution of chromic acid mixture (11) made by diluting 55 g of CrOz and 210 mJ of concentrated sulfuric acid with water at a temperature of 55°C to selectively chemically roughen the parts that would become the circuit parts. It was washed with water and neutralized.

This insulating substrate was immersed in the following electroless cobalt plating solution for 60 minutes to form a plating layer of about 5 μm.

〔composition〕

Cobalt chloride: 35g/j! Sodium citric acid: 116g/j! Sodium hypophosphite
: 11.5 g/A [Conditions] pH: s, on 10.0 Solution temperature: After washing with water, CC-4 was used as an electroless plating solution.
1 Plating solution (Hitachi Chemical Co., Ltd., trade name) at 70℃
After depositing about 20 Iim of copper plating, a solder resist was applied by screen printing to the surface of the substrate other than the through holes and cured by heating to prepare a test wiring board.

Example 4 The adhesive used in Example 1 was applied to a glass cloth epoxy resin laminate LE-168 (trade name, Hitachi Chemical Co., Ltd.) containing palladium chloride and cured by heating to obtain an insulating substrate.

After that, a hole was drilled at a predetermined position using a high-speed drill machine, and Photec 5R-3000 (trade name, Hitachi Chemical Co., Ltd.), which is a photoresist film for electroless plating, was laminated with a vacuum laminator, and exposed and developed. Then, a resist was formed on the parts that would not form a circuit.

The insulating plate on which the resist was formed was immersed for 10 minutes in a solution of chromic acid mixture (11) made by diluting 55 g of CrOz and 210 ml of concentrated sulfuric acid with water at a temperature of 55°C to selectively chemically roughen the parts that would become the circuit parts. It was washed with water and neutralized.

This insulating substrate was immersed in the following electroless palladium plating solution for 60 minutes.
A plating layer of about 1 μm was formed by immersion for a minute (composition) Tetramine palladium chloride: 7.5 g/A EDTA-2Na: 8. Og/R Ammonia water: 280 g/6 hydrazine (1 mol/
1):8mj! //! [Conditions] Solution temperature: 38°C Next, after washing with water, CC-4 was used as an electroless plating solution.
1 Plating solution (Hitachi Chemical Co., Ltd., trade name) at 70℃
After depositing a copper plating of approximately 20 μm, a solder resist was applied by screen printing to the surface of the substrate other than the through holes and cured by heating to obtain a test wiring board.

Example 5 The adhesive used in Example 1 was applied to a glass cloth epoxy resin laminate LE-168 (trade name, Hitachi Chemical Co., Ltd.) containing palladium chloride, and the adhesive was cured by heating to obtain an insulating substrate.

After this, a hole was drilled at a predetermined position using a high-speed drill machine, and Fotefuku 5R-3000 (trade name, Hitachi Chemical Co., Ltd.), which is a photoresist film for electroless plating, was laminated with a vacuum laminator, and exposed and developed. Then, a resist was formed on the parts that would not form a circuit.

The insulating plate on which the resist has been formed is immersed for 10 minutes in a solution of chromic acid mixture (11) made by diluting 55 g of croz and 210 mj+ of concentrated sulfuric acid with water at a temperature of 55°C to selectively chemically roughen the parts that will become the circuit parts. It was washed with water and neutralized.

This insulating substrate was immersed in the following electroless gold plating solution for 30 minutes to form a plating layer of about 0.5 μm.

〔composition〕

Potassium gold cyanide: 2g/j! Ammonium chloride: 15g/l Sodium citrate: 5
0g/β sodium hypophosphite: 10g/j! [Conditions] p) (Near, O~7.5 Solution temperature: 92°C Next, after washing with water, CC-4 was used as an electroless plating solution.
1 Plating solution (Hitachi Chemical Co., Ltd., trade name) at 70℃
After depositing a copper plating of about 20 μm, a solder resist was applied by screen printing to the surface of the substrate other than the through holes and cured by heating to obtain a test wiring board.

Comparative Example 1 As described below, in Example 1, only electroless copper plating was performed.

Glass cloth base epoxy resin laminate LE-144 (Hitachi Chemical Co., Ltd., trade name) containing palladium chloride as a catalyst for electroless plating is coated with acrylonitrile butadiene rubber as a main component using an adhesive containing the same palladium chloride. An adhesive prepared by blending alkylphenol resin, epoxy resin, silica as an inorganic filler, and zirconium silicate in a solvent was applied, dried, and cured by heating to form an adhesive layer.

Next, after punching holes at predetermined positions using a punch press, Photec 5R-3000 (trade name, Hitachi Chemical Co., Ltd.), a photoresist film for electroless plating, was used.
were laminated using a vacuum laminator, exposed to light in areas that would not form a circuit, and the unexposed areas were developed and removed to form a resist. At this time, the circuit width and the spacing between the conductors were both 0.15 mm.

The insulating plate with the resist formed was treated with 55g of CrOz and 210nl of 4-sulfuric acid! It was immersed for 10 minutes in a solution of a chromic acid mixture diluted with water to give lβ at a temperature of 55° C., to selectively chemically roughen the portion that would become the circuit portion, and then washed with water and neutralized.

Next, after washing with water, CC-4 was applied as an electroless plating solution.
1 Plating solution (Hitachi Chemical Co., Ltd., trade name) at 70℃
After depositing a copper plating of about 20 μm, a solder resist was applied by screen printing to the surface of the substrate other than the through holes and cured by heating to obtain a test wiring board.

Comparative Example 2 As described below, in Example 2, only electroless copper plating was performed.

The adhesive used in Example 1 was applied to a glass cloth epoxy resin laminate LE-168 (trade name, Hitachi Chemical Co., Ltd.) containing palladium chloride and cured by heating to obtain an insulating substrate.

After that, a hole was drilled at a predetermined position using a high-speed drill machine, and Photec 5R-3000 (trade name, Hitachi Chemical Co., Ltd.), which is a photoresist film for electroless plating, was laminated with a vacuum laminator, and exposed and developed. Then, a resist was formed on the parts that would not form a circuit.

The insulating plate on which the resist was formed was immersed for 10 minutes in a solution of chromic acid mixture (11) made by diluting 55 g of CrOz and 210 ml of concentrated sulfuric acid with water at a temperature of 55°C to selectively chemically roughen the parts that would become the circuit parts. It was washed with water and neutralized.

Next, after washing with water, CC-4 was applied as an electroless plating solution.
1 Plating solution (Hitachi Chemical Co., Ltd., trade name) at 70℃
After depositing a copper plating of about 20 μm, a solder resist was applied by screen printing to the surface of the substrate other than the through holes and cured by heating to obtain a test wiring board.

Further, in both the example and the comparative example, the conductor width and interval are both 0.
In No. 11, an electrolytic corrosion evaluation pattern was used, which had a through-hole diameter of 0.6 tm, approximately 200 through-holes, and a conductor pattern that alternately connected the through-holes to both sides of the insulating substrate via the through-holes.

In order to accelerate the electrolytic corrosion evaluation test on a large number of test pieces, under heating and humidification at 65°C/90%, 50 V DC was applied between the conductors and the current was applied continuously at regular intervals for a certain period of time. The insulation resistance value between the conductors was measured, and the cross section of the through hole was observed to check for the occurrence of dendrites. The results are shown in Table 1 below.

At the same time, the solder heat resistance and peel strength required for the wiring board were measured in accordance with JIS-C-6481. The results are also shown in Table 1.

As can be seen from these results, the effects of this example are that it is excellent in suppressing insulation deterioration due to electrolytic corrosion on the surface of an insulating substrate, without impairing other properties required for wiring boards, and that Improvement was also seen in electrolytic corrosion.

Table 1 (Effect of the invention)

Claims (1)

[Claims] 1. A method for manufacturing a wiring board comprising the steps shown below. a. An adhesive layer containing a catalyst for electroless plating is formed on the surface of an insulating substrate containing a catalyst for electroless plating. b. Drill a hole that will become a through hole. c. A resist for electroless plating is formed in areas other than the through holes and the portions that will become circuit parts. d. It is immersed in a chemical roughening solution to selectively roughen the surface where the electroless plating resist is not formed. e. As the first metal layer, a layer made of one or a combination of two or more of electroless nickel alloy, electroless cobalt alloy, electroless palladium, or electroless gold is applied to the area where the electroless plating resist is not formed. Form. f. A copper plating layer is formed on the first metal layer by immersing it in an electroless copper plating solution.