JPH05308189A - Through-hole plated circuit board and its manufacture - Google Patents

Abstract

PURPOSE:To realize resource saving, no environmental pollution and shortened process time by a method wherein a conductive metal sulfide-contained layer is formed at least on a holed face in a holed board, the sulfide-contained layer is used as a cathode, a metal layer is formed on the sulfide-contained layer by an electroplating method and the through hole is connected electrically. CONSTITUTION:A conductive metal sulfide-contained layer is formed on a double-sided board in which a hole has been made and which is composed of an insulating ceramic material or on a holed face in a multilayer board. The conductive metal sulfide-contained layer is used as a cathode; a metal layer composed of copper, nickel, gold, tin, lead or a lead-tin alloy is formed on the conductive metal sulfide-contained layer by an electroplating method; conductors are connected electrically via the through hole. The through hole can be formed at low costs in a simplified process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a circuit board such as a printed wiring board or a ceramics board used in electronic equipment.

[0002]

2. Description of the Related Art A double-sided printed wiring board in which an electric circuit is formed on both sides of an insulating plate to conduct electricity through the through holes, and a conductor layer is provided not only on the surface of the insulating substrate but also inside the through holes, and through holes are formed between the conductor layers. The multilayer wiring board that is electrically connected with is used most widely in electronic devices. These through holes are usually connected by through hole plating.

As a method of through-hole plating, there are a subtractive method, a full additive method, a part additive method and the like. That is, there is an electroless plating method, or a combined process consisting of electroless plating and electroplating,
The process is appropriately selected and used from the viewpoints of the degree of miniaturization of the pattern of the formed circuit, the through hole diameter, the insulating material, and the manufacturing cost.

Generally, the mainstream process is to electrolessly plate a substrate perforated with a drill and then electroplating. This method is also subdivided into various methods in view of the fineness of the pattern, the diameter of the through hole, and the manufacturing cost. Typical examples of the manufacturing process of this through-hole substrate include a tenting method, a photo ED method, and a pattern plating method.

A brief description of each method is as follows. First, the tenting method will be described. A double-sided copper clad laminate is drilled and panel plated. A dry film is applied and image processing is performed to form an etching resist. Etching is performed to form a circuit. By removing the etching resist and forming a solder resist or the like, a through hole substrate is obtained.

Next, the photo ED method will be described. A double-sided copper clad laminate is drilled and panel plated. A resist is formed on both sides and the inside of the through holes by using an electrodeposition method, and an image processing is performed to form an etching resist.
Etching is performed to form a circuit. By removing the etching resist and forming a solder resist or the like, a through hole substrate is obtained.

Further, the pattern plating method will be described. A double-sided copper clad laminate is drilled and panel plated. Apply a dry film and process the image. Pattern plating is performed, and then etching resist plating is performed. After that, etching is performed to form a circuit. By removing the etching resist and forming a solder resist or the like, a through hole substrate is obtained.

All of the above methods have a panel plating step after drilling. Panel plating is to make electrical connection by conducting through-hole plating between conductor layers. This process is performed by electroplating subsequent to electroless plating on through-holes, or electroless plating called an additive method. It consists of plating thickening method.

[Problems to be Solved by the Invention]

Electroless plating is performed with EDTA, bipyridyl,
Using chelating agents such as cyanide compounds, palladium, tin, catalysts, harmful substances such as formalin, expensive resources, etc.
In addition, it is difficult to meet demands such as resource saving, no pollution, simplification of process control, reduction of the number of processes, and shortening of process time by using long reaction time and a large amount of washing water to obtain a high quality plating film. there were.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems and is intended to electrically connect conductors through a through hole of a through hole printed wiring board as a circuit board. And a new through-hole printed wiring board by the improved method.

According to the present invention, a conductive metal sulfide-containing layer is provided on at least a hole-punched surface (inner wall of a through hole) of a perforated substrate, and thereafter, the sulfide-containing layer is used as a cathode to form an electric field on the sulfide-containing layer. It is characterized in that a metal layer is provided by a plating method to electrically connect through holes.

As the substrate, an organic or inorganic insulator or a composite material thereof is used.

As the organic insulator, epoxy resin, fluorine resin, polyimide resin, phenol resin, etc. are used. Inorganic insulators include short glass fibers, woven glass cloth, and ceramics. A glass / epoxy base material such as FR-4, CEM-3 or CEM-1 is used as the composite material.

A single-sided or double-sided copper-clad substrate obtained by laminating a copper foil of 10 to 60 μm on one side or both sides of the substrate material, or a multilayer board in which these are used as an inner layer or an outer layer and combined with a prepreg is used.

As the double-sided copper-clad substrate, a rigid plate having a thickness of 0.3 mm to 1.6 mm or a so-called flexible double-sided substrate having a thickness of 0.3 mm is used.

The copper clad substrate is usually provided with through holes for electrical connection between the front and back or inner layers having a diameter of 0.2 mm to 1.2 mm by drilling or punching.

In the present invention, the conductive metal sulfide-containing layer is formed on at least the insulating material of the through hole.

Regarding the conductive metal sulfide, its properties and synthesis method are disclosed in Japanese Patent Laid-Open Nos. 62-143306 and 61-215661 by the inventor of the present invention.
It is disclosed in JP-A-61-10008 and JP-A-64-18915.

In the present invention, since the conductive metal sulfide-containing layer is used as the base electrode for through-hole electroplating, the metal sulfide needs to have high conductivity. That is, the electrical conductivity of the metal sulfide is 10 ^-4 Scm ^-1 or more, preferably 10 ^-2 Scm ^-1 or more. As a metal capable of forming a sulfide having high electric conductivity, IUPAC
Elements of Group Nos. 4 to 12 in the periodic table of elements according to the Inorganic Chemistry Nomenclature Revised (1989) are used.

Among these, copper sulfide, nickel sulfide,
Iron sulfide, cadmium sulfide, cobalt sulfide, and chromium sulfide are preferable because they are inexpensive and relatively safe. Copper sulfide is particularly preferable because it has high electric conductivity and is inexpensive. The metal sulfide is obtained by reacting a metal compound with a sulfur compound. As the metal compound, sulfates, nitrates, halides, organic acid salts, organic metal compounds and the like are used. In particular, halides, sulfates, nitrates and acetates are inexpensive and preferable in terms of pollution control.

Examples of the sulfur compound include mercaptan, hydrogen sulfide, alkyl sulfide, thiosulfate, sodium sulfide, ammonium sulfide and thiourea.

As the reaction system, a liquid phase reaction or a gas-solid reaction using a slurry reaction hydrogen sulfide gas or the like is adopted. As the liquid phase, an organic solvent having a high solubility of water or a metal compound in the solvent, for example, acetonitrile, dimethylformamide,
Dimethylforsulfoxide or the like is appropriately selected. In particular, an aqueous solution or hydrogen sulfide gas is inexpensive and preferable in terms of pollution control.

The reaction temperature is -20 ° C to 300 ° C. The metal sulfide can also be deposited in a single step by chemical vapor deposition (CVD). Generally, CVD in one step
It is cheap and preferable to first attach the metal compound to the printed circuit board by the liquid phase method and then convert it to the metal sulfide by the reaction with the sulfur-containing compound, rather than attaching the metal compound by the gas phase method such as the method.

A printed circuit board perforated with a drill is immersed in a metal compound solution and then reacted with hydrogen sulfide gas, immersed in a sulfur compound solution, or heated with a sprayed sulfur compound solution to produce a metal sulfide. Can be deposited on the inner wall of the through hole. It is also possible to immerse the printed circuit board in the sulfur compound solution and then dry it, and then immerse it in the metal compound solution, or heat the sprayed metal compound solution to deposit the metal sulfide on the inner wall of the through hole. .. Furthermore, the metal sulfide can be deposited on the inner wall of the through hole by immersing the printed circuit board in a solution containing a metal compound and a sulfur compound to cause a reaction.

The reaction conditions of the metal compound and the sulfur compound in the present invention are not particularly limited, but the molar ratio of the metal compound and the sulfur compound is 1: 0.001 to 1:10.
The range of 00 is desirable. In particular, when metal sulfide is deposited on the inner wall of the through hole by immersing the printed circuit board in a solution containing a metal compound and a sulfur compound and reacting the solution, the molar ratio of the metal compound and the sulfur compound is 1: 0.01. It is preferably in the range of 1: 100 to 1: 100, particularly preferably in the range of 1: 0.1 to 1:10.

Further, the above-mentioned JP-A-62-143306.
No. 61-215661 and 61-100.
08, JP-A No. 64-18915, and further JP-A No. 6-18
As described in JP-A No. 1-91005, a dispersion containing colloidal metal sulfide (including a dispersion in which a polymer compound is dissolved) is applied to the inner wall of a through-hole to form a dispersion medium. By removing it, a metal sulfide layer may be formed on the inner wall of the through hole.

In order to firmly attach the metal sulfide to the through-hole portion of the printed board, the perforated board is subjected to pretreatments such as degreasing cleaning, soft etching and oxidation treatment, if necessary. Examples of the degreasing cleaning include mechanical methods such as buffing, and washing with a jet water after rinsing the aqueous surfactant solution. As the soft etching, dilute sodium hydroxide aqueous solution, dilute potassium hydroxide aqueous solution, sodium carbonate aqueous solution or the like is used when the substrate is glass / epoxy, and sodium-naphthalene is used when the substrate is polytetrafluoroethylene. A system organic solution is used. Even when the base material is ceramics, alkali or acid is selected. An example of the oxidation treatment is an aqueous mixed solution of potassium permanganate and caustic alkali.

Further, in order to promote the adhesion of the metal sulfide to the through holes of the printed circuit board, at least the through holes are pretreated with a coupling agent such as iodine, polyethyleneimine or polyvinyl alcohol in advance. Is preferred. As the pretreatment method, the printed board is immersed in a solution of the coupling agent 0.005 to 1 mol / l (liter), preferably 0.01 to 0.5 mol / l for about 10 minutes and then washed with water. Is desirable.

After forming the conductive metal sulfide, a metal layer is provided thereon by electroplating. A known metal is used as the metal layer, but in particular, copper, nickel, gold, tin,
From the viewpoints of cost, fineness and reliability, it is preferable to select one of the lead / tin alloys according to the application of the substrate and the pattern forming method.

As a general-purpose printed circuit board, copper plating and lead / tin solder plating are particularly preferable.

Known methods can be easily applied to the metal electroplating. The thickness of the plating is controlled by the amount of electricity, but 0.1
The thickness is from 70 μm to 70 μm, and normally 5 to 40 μm is suitable. For example, as the copper plating solution, a copper sulfate plating solution obtained by adding an appropriate amount of a brightening agent and chlorine ions to a copper sulfate sulfuric acid aqueous solution or a copper pyrophosphate plating solution obtained by adding an appropriate amount of a brightening agent to an aqueous solution of copper pyrophosphate-ammonia pyrophosphate is used. Be done. The cathode current density of the plated substrate is 1 to 10 A / d
Electrolytic copper plating is carried out using a copper anode with stirring at m ² and temperature of 20 to 60 ° C. Copper sulfate plating is preferable in terms of plating quality or pollution control.

In the case of solder plating, borofluoride first
An aqueous solution of tin, lead borofluoride, and hydrofluoroboric acid is used as a plating bath.

In the manufacturing process of the through-hole plated printed circuit board according to the present invention, one embodiment is to perform electrolytic copper plating after depositing a metal sulfide on the entire copper clad board drilled with a drill. An organic resist film may be attached to a portion other than the portion drilled by a drill to selectively attach a metal sulfide to the drilled portion, and electroplating may be selectively applied to the hole portion.

The through-hole plated substrate obtained by electroplating the metal sulfide thus obtained is then sent to the image forming step, for example, a resist by the photo ED method, a dry film resist by the tenting method or After the dry film resist or the like is formed by the pattern plating method, the photo E is formed by the metal etching or the metal etching subsequent to the pattern plating.
A through hole plated substrate by the D method, a through hole plated substrate by tenting, and a through hole plated substrate by the pattern plating method are obtained. Among these, the photo-ED method, which has been industrialized in recent years, is particularly preferable from the viewpoint of inexpensiveness and fineness.

[0035]

【Example】

Example 1 A glass / epoxy double-sided board (thickness: 1.6 mm, FR-
A substrate provided with a through hole having a diameter of 0.8 mm by drilling in 4) was used as a test piece. This substrate was buffed, washed with water, degreased with a 4% aqueous sodium hydroxide solution, and washed with water.

Then, it was immersed in a 0.1 mol / l copper sulfate aqueous solution at 25 ° C. for 5 minutes. Excess liquid was removed from the substrate. Then, it was immersed in a 0.5% ammonium sulfide aqueous solution. The inner wall of the through hole and the copper surface turned black or blackish brown. This substrate was washed with water and then dried. Do this operation 3
Repeated times.

It is well known that black conductive copper sulfide is produced in the reaction of a copper compound with ammonium sulfide and the reaction of a copper compound such as copper sulfate with sodium thiosulfate under heating. Further, the fact that the formation reaction of these copper sulfides is carried out in the presence of a polymer material or glass can form the surface of the polymer material or the surface layer of the glass under certain conditions, for example, as disclosed in JP-A-62-143306. JP-A-61-215661, JP-A-61-10008
JP-A-64-18915, JP-A-61-4281
No. 3, Chem, Ind, (London) 198.
This black or blackish brown substance is considered to be copper sulfide because it is well known in 653, page 531. In fact, the deposition of this black-brown material on the inner walls of the through holes provided conduction between both sides of the substrate.

Copper electroplating was performed on this substrate. High-purity copper sulfate for plating in the plating soluble (CuSO _4. · 5H ₂
O) 30 g / l, special grade sulfuric acid 250 g / l, chloride ion 2
5 ppm, additive 50 ml / l (Shipley Co., XP-8
A mixed solution of 802) was used. When the printed circuit board was used as a cathode and plating was performed for 30 minutes under stirring at a cathode current density of 1.5 A / dm ^{2 at} a temperature of 25 ° C., all the through holes were copper-plated. Subsequently, plating was carried out, and copper plating with a thickness of 30 μm was carried out in the through holes. The copper plating in the through holes was firmly attached to the substrate.

Example 2 Double-sided copper clad laminate drilled by the same method as in Example 1 except that 0.1 mol / l nickel chloride was used in place of copper sulfate as the metal compound for forming the metal sulfide. Nickel sulfide was deposited on a plate (thickness: 1.6 mm, FR-4). After washing with water, electroplating was performed in the same manner as in Example 1. After 30 minutes from the start of energization, copper plating was applied to all the through holes. Continue to plating,
Copper plating with a thickness of 30 μm was performed in the through holes. The copper plating in the through holes was firmly attached to the substrate.

Example 3 A double-sided copper clad laminate drilled by the same method as in Example 1 (thickness: 1.6 mm, FR-
4) was immersed in a mixed solution of 0.1 mol / l copper sulfate and 0.1 mol / l sodium thiosulfate mixed at 40 ° C. or lower and then heated, and black copper sulfide was added at 75 to 85 ° C. for 1 hour. Was generated. After that, the substrate is taken out, washed and dried,
When electrolytic copper plating was carried out in the same manner as in Example 1, the inner surfaces of all the through holes were copper plated.

<Embodiment 4> A double-sided copper clad laminate (thickness: 1.6 mm, FR-) drilled in the same manner as in Embodiment 1.
4) was pretreated by immersing it in a 0.05 mol / l iodine solution at room temperature for 5 minutes. After washing and drying, copper sulfide was deposited on the inner surface of the through holes and the surface of the copper foil in the same manner as in Example 1. Copper sulfide was uniformly formed inside the through holes. The reaction between copper sulfate and ammonium sulfide was carried out four times, and then electrolytic copper plating was performed, but copper plating was performed on all inner surfaces of the through holes.

<Example 5> Copper sulfide was permeated in the same manner as in Example 4 except that 0.5% polyethyleneimine methanol solution was used instead of the iodine solution of Example 4 for pretreatment. It was formed on the inner surface. Even after electrolytic copper plating, copper plating was performed on the inner surfaces of all the through holes.

[0044]

According to the present invention, a conductive metal sulfide-containing layer is formed in a through hole of a circuit board, and a metal layer is formed on the conductive metal sulfide containing layer by an electroplating method. Through holes can be formed in the.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Mizutsuki 2-2-1 Aioi, Sagamihara City, Kanagawa Prefecture

Claims (5)

[Claims] 1. A method for forming a conductive metal layer on at least a through hole portion of a printed wiring board having a through hole on a double-sided board or a multi-layer board made of an insulating organic polymer, glass fiber and / or an insulating ceramic material, etc. A conductive metal sulfide-containing layer on at least the perforated surface of the formed substrate, and a step of forming a metal layer on the inner wall of the through hole by electroplating on the sulfide-containing layer using the conductive metal sulfide-containing layer as a cathode. A method of manufacturing a through-hole plated circuit board having: 2. The method for manufacturing a through-hole plated circuit board according to claim 1, wherein the conductive metal sulfide is selected from copper sulfide, nickel sulfide, cobalt sulfide, and iron sulfide. 3. The method for manufacturing a through-hole plated circuit board according to claim 1, wherein the metal layer is copper, nickel, gold, tin, lead, or a lead / tin alloy. 4. A double-sided or multi-layer through-hole plated circuit board having a conductive metal sulfide-containing layer in the through hole. 5. A metal plating layer made of any one of copper, nickel, tin, and lead / tin alloy is provided on the conductive metal sulfide-containing layer having a thickness of 0.1 μm to 50 μm. Double-sided or multilayer through-hole plated circuit board.