JPS59172796A - Method of producing printed circuit board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is an economical and highly workable blind that uses a copper-clad laminate to selectively deposit electroless plating only on necessary areas such as through holes. Concerning circuit boards.

As is well known, the mainstream method for manufacturing printed circuit boards has been the etched foil method. However, as printed circuit boards have become denser in recent years, the conventional etched foil method has not only complicated the manufacturing process but also degraded the dimensional accuracy of the circuit itself due to undercuts during etching and uneven plating thickness due to electroplating. In addition, overhanging bridges and other factors have made it difficult to produce them industrially.

Therefore, recently, various methods have been proposed in order to cope with the increase in density, mainly using electroless plating, which can avoid the non-uniformity of plating thickness caused by electroplating and obtain a uniform plating thickness.

One of these methods is the additive method, but it has problems such as the use of expensive special base materials and pollution problems caused by surface roughening liquid.
Considering the adhesion between the base material and the circuit part and the cost of the adhesive used, it is thought that copper-clad laminate-based products will continue to become mainstream.

For example, in a copper-clad laminate, circuits and through-holes that require through-holes are masked, excess copper is dissolved and removed by etching, and then a catalyst is applied to the entire surface of the laminate including the through-holes. It is conceivable to manufacture a printed circuit board in which a circuit is formed by applying electroless plating only to desired portions of the circuit.

However, in this method, if the amount of adsorbed catalyst is large, the insulation resistance between the circuits will decrease, causing short circuits in extremely narrow areas between the circuits.

For example, (1) the invention disclosed in JP-A-54-11965 involves forming a desired circuit by selectively etching the copper foil on the copper-clad laminate, and then forming through holes at predetermined positions in the formed circuit. Next, an electroless plating pretreatment layer is formed on the entire circuit formation including this through hole portion, and then the electroless plating pretreatment layer of the entire circuit formation is mechanically removed, and the electroless plating pretreatment layer is removed. A method of manufacturing a printed circuit board has been proposed in which a solder resist film is formed on areas other than the formed through-holes and the circuit area around them, and then an electroless plating layer is formed on the through-hole areas and the circuit areas around them. There is.

In addition, (2) the invention disclosed in JP-A-50-155965 forms through-holes in a copper-clad laminate, and forms a layer of an activating substance for electroless plating on the entire surface including the inside of the null hole. A resist in the form of a photocurable film was adhered to the surface of the plate coated with copper foil, exposed and developed so that the through-hole area and the area that would become the printed circuit remained, and the exposed copper foil was removed by etching. A method of manufacturing a printed circuit board has been proposed in which electroless plating is performed using an activator for electroless plating.

Furthermore, in the same manner (through-holes P were formed in a 3-inch copper-clad laminate, areas other than the circuit area including the μm hole portions were masked with alkali-soluble ink, and then activation for electroless plating was performed, as described above). A method for manufacturing printed circuit boards has been proposed in which the ink is removed and the activated layer remains on the holes and circuit areas using electrolytic plating.

However, in all of the above conventional methods, the activation layer remains partially and a plating film is formed only on the 9 parts by electroless plating, but in each manufacturing method, the activation layer is removed. The process becomes complicated due to the addition of one extra step, and it is not a practical method.
Each of the methods for removing the activated layer has the following drawbacks.

Method (1) does not make it difficult to remove the catalyst material, especially in areas where the circuit spacing is narrow; for example, if mechanical polishing is used, very fine "sink marks" can be removed from the circuit area. ” occurs, causing a short circuit between the circuits. A conflict occurs.

In addition, in method (2), when forming fine circuits due to high density, there is an activated material layer between the resist used and the copper foil, so for example, a photocurable film resist is used. When used, the adhesiveness between the resist and the copper foil is poor, and the resist on the circuit flows during development or etching, and as a result, it no longer functions as an etching resist, making it difficult to form the desired circuit.

Furthermore, in the method (3), ink often adheres to the inner wall of the null-hole portion, and .1 may not be partially formed during activation. In addition, even when a mask is completely formed on the entire surface of a copper-clad laminate with ink, and then a null hole is provided, ink may adhere to the drill and the bottle of the mold during drilling with a drill or punching with a mold.
Furthermore, it adheres to the inner wall of the through hole and causes a phenomenon similar to smear, and if the electroless plating does not deposit partially or even if it does, the contact with the electroless plating becomes sensitive.

As described above, the various printed circuit board manufacturing methods described above are impractical, and it is impossible to industrially produce the products.

Therefore, in view of the above-mentioned drawbacks of the conventional methods, the present invention has discovered a manufacturing method that can simplify the process and easily produce extremely reliable and economically inexpensive high-density printed circuit boards. .

That is, in the present invention, after drilling a hole in a copper-clad laminate, masking the through-hole portion and the desired circuit portion, and dissolving and removing the excess copper foil other than the circuit portion, or removing the excess copper foil other than the desired circuit portion. After etching the copper foil and forming through-holes (V) at fixed positions of the formed circuit, a catalyst of 0.15 to 4 d or less is applied to the entire surface of the laminate including the inner wall of the null-holes. to be adsorbed. Furthermore, after forming a solder resist film on the through-hole portions of the laminate or other areas other than those that require plating, it is immersed in an electroless plating bath and plated on the through-hole portions or circuits, or if necessary, a solder resist film is formed on the through-hole portions or circuits. Instead, the manufacturing of printed circuit boards involves the process of masking areas that do not require electroless plating with a photocurable film resist, immersing them in an electroless plating bath, plating, and then forming a solder resist film. It's a method.

The present invention will be explained in detail below using the drawings.

FIG. 1 shows a longitudinal cross-sectional view of a copper-clad laminate used in the present invention. All commercially available katana plates can be used. For example, a paper-epoxy copper-clad laminate, a glass-epoxy copper-clad laminate, a combo dift copper-clad laminate, and a triazine steel-clad laminate can be used. In addition, the thickness of copper foil is 18.36.70 μm which is generally available.
Any of these can be used, but since high density is currently progressing, the thickness of the copper foil is preferably 18 μm in order to form circuits with narrow circuit spacing and circuit width.

Next, holes are made for inserting the components necessary for the circuit and for conducting between the front and back sides. FIG. 2 shows this. For drilling, both drilling and punching with a die can be used,
If a large number of holes of the same type are to be punched, punching with a die is advantageous, and if a small amount is to be punched, a die-cutting method is more advantageous.

FIGS. 8 and 4 show the etching process. There are two types of resists used in the etching process: alkaline and organic solvent soluble inks and photocurable film resists. However, the ink has problems with pinholes and poor circuit dimensional accuracy, and sometimes the ink adheres to the inner wall of the through hole and is difficult to remove when the ink film is peeled off, making it difficult to use as an etching resist.
A photocurable film resist, so-called photoresist, is preferred. Examples of the photoresist include Riston manufactured by DuPont and Laminar manufactured by Dynachem, and any of these may be used. Etching liquids include alkaline etching liquid, ferric chloride, cupric chloride, etc., but the etching resist is a photoresist, and waste liquid can be disposed of due to problems such as pollution. Since the etching solution must be a liquid, cupric chloride is preferably used as the etching solution.

In the present invention, the above method may be used to form the circuit by etching, and then the process may be performed by drilling holes.

Next, pretreatment for electroless plating is performed. FIG. 6 shows this. Regarding electroless plating, there are electroless copper plating, electroless nickel plating, electroless gold plating, etc., but the only difference is the plating bath, and the other plating pretreatment steps are the same, so we will use electroless copper plating here. I will explain how I did it.

1. First, degreasing is performed using an organic solvent or alkaline aqueous solution. For example, trichlorethylene, 0.
Any one of a 1 to 5 mol/g aqueous sodium hydroxide solution, γ Lugyrate manufactured by Sibley, or Liner Semoyligant 902 manufactured by Schering Co., may be used.

A through-hole surface may then be applied using Conditioner 1160 manufactured by GiGray.

Furthermore, soft etching is performed on the copper surface.

This step requires 100-250 Vl of ammonium peroxide or 1. Any mixed aqueous solution consisting of 0 to 4.0 mol/43 sulfuric acid and 0.5 to 2.5 mol/71 hydrogen peroxide may be used.

Finally, a catalyst is applied. What is meant by catalyzing here?
By immersing a laminate in a solution containing metal ions that can act as a catalyst, the metal ions are adsorbed onto the laminate, and then by immersing the laminate in a solution that allows the metal ions that can act as a catalyst to be absorbed into the metal. , a method in which a catalyst is adsorbed onto the laminate. Specifically, an aqueous solution containing metal ions that can act as an catalytic agent is PdC#z SnC/+2HCII (:
l Lloyd type), P+lCL SnCgz N
There are eight types of hCe (colloid type) and palladium organic complex salt compounds, any of which may be used. There are two types of liquids that can reduce metal ions to metals: an aqueous solution consisting of sulfuric acid or oxalic acid, and an aqueous solution consisting of an alkaline hydroxide such as sodium hydroxide or sodium carbonate and a borohydride compound. may also be used.

In this step, the amount of metal that acts as a catalyst to be adsorbed onto the laminate is reduced to 0. 15 mg/dn? By doing the following, the insulation resistance will not decrease even between extremely narrow circuits, the extra process of removing the catalyst will not be necessary, and the manufacturing process can be simplified. 0. 15ml? //am
'In order to reduce the concentration of metal ions in the aqueous solution containing metal ions that can serve as catalysts to 2000 to 2500 pP,
ffl, and the bath temperature is 40-50°C.
The immersion time of the laminate may be controlled within the range of 4 to 5 minutes.

In addition, the solute concentration of the reducing solution was adjusted to 0.01 to 1 mo I/J.
The temperature of the bath may be controlled within the range of 20 to 50°C, and the immersion time of the laminate may be controlled within the range of 2 to 10 minutes.

Next, the solder resist film is printed using a printing method or a photo-curable fill-em type solder/ruder resist to mask areas other than the through-hole areas, and then immersed in an electroless copper plating bath to coat the solder resist film with a desired thickness. Form a film. This is shown in FIGS. 7 and 8. As another method, instead of the solder resist film, a photocurable film resist may be used as a mask and immersed in an electroless copper plating bath to form an electroless copper plating film, and then a solder resist film may be formed.

After the electroless copper plating step, the printed circuit board can be manufactured using the same manufacturing steps as those used in the etched foil method. For example, terminals must be plated with nickel or gold. If solder is required for the entire circuit or the null-hole area, the printed circuit board can be completed by going through the necessary steps, such as applying solder plating.

The present invention will be explained in more detail with reference to Examples below.

Example 1 A circuit as shown in FIG. 9 was formed by etching using a glass epoxy steel laminate.

The laminate was degreased by immersing it in an alkylate solution manufactured by Sibley at 60° C. for 5 minutes. Next, the surface was smoothed by immersing it in a conditioner 1160 solution manufactured by the company at 30°C for 8 minutes. Furthermore, the copper surface was soft etched by immersing it in an aqueous ammonium persulfate solution at 150 fj/l and 25°C for 2 minutes. After dissolving the scum on the copper surface by immersing it in an arsenic acid aqueous solution of 8 mol/J at room temperature for 1 minute, a catalyst was applied. At this time, the amount of adsorbed catalyst was varied and the insulation resistance between the circuits was measured. This relationship is shown in the table below. The amount of adsorbed catalyst was determined by atomic absorption spectrometry after dissolving it in dilute nitric acid. Also, the insulation resistance is 100V, 1
After charging for a minute, measurements were made using a 4829A resistance meter manufactured by Yokogawa-Huhle and Topan Card.

Table: Relationship between amount of adsorbed catalyst and insulation resistance Example 2 Six holes were punched in a paper-epoxy copper-clad laminate using a die. The necessary circuit parts and through-hole parts were masked using DuPont's Riston 1220.

Excess @ was dissolved and removed using a cupric chloride solution.

After peeling off the resist, the laminate was immersed in a 6[]'C alkylate solution manufactured by Sibley for 5 minutes to degrease it. Next, the surface was smoothed by immersing it in a conditioner 1160 solution manufactured by the company at 80'C for 3 minutes.

The copper surface was soft etched by immersing it in ammonium persulfate containing 115 oy/g of SaraVC at 25°C for 2 minutes.

It was immersed in a 1.8 mol/ll sulfuric acid aqueous solution at room temperature for 1 minute to dissolve the scum on the copper surface. Metal ion concentration is 200
PaCe2-SnC at 0 ppm and bath temperature of 45 °C
Immersed in an aqueous solution containing gz-HCe for 5 minutes, and then immersed in an aqueous solution containing 0.7 mol/g of sulfuric acid and oxalic acid at 20°C.
The catalyst was immersed in a mixed solution for 8 minutes to adsorb the catalyst on the surface of the laminate. After drying at 110° C. for 10 minutes, a solder resist film is formed on the surface of the laminate other than through-hole areas and areas where plating is to be deposited using a solder resist ink manufactured by Tokyo Ohka.

Off-acid copper 0.08 mol/(10ED
TA-ZNa salt 0.05 mol/#0 Sodium hydroxide 0.20 mol/ItO Formalin 0.20 mol/IIO Sodium cyanide 5 my/e01.10-phenanthroline 5 tnII/IO Polyethylene V glycol/I/ 1-9 The above composition was immersed in an electroless copper plating bath at 60°C for 15 hours to form a plating film of about 30 μm. After forming the plating film, insulation resistance was measured, and no abnormality was found.

Example 3 A drill was used to drill holes in a laminate made of epoxy copper. The necessary circuit parts and through-hole parts were masked using DuPont's Riston 1220. Excess copper was dissolved and removed using a cupric chloride solution. After removing the resist, the laminate was immersed in an alkylate solution manufactured by Sibley at 60° C. for 5 minutes to degrease it. Next, the surface was leveled by immersing it in a conditioner 1160 solution manufactured by the company at 30° C. for 3 minutes. Furthermore, 1.8 mol/e of sulfuric acid, 2
The copper surface was soft etched by immersing it in a mixed solution of mol/l hydrogen peroxide for 2 minutes. 1.3 mol/I
I. The scum on the copper surface was dissolved by immersing it in a sulfuric acid aqueous solution at room temperature for 1 minute. Pt3CM2-5nCe2-NaC with a metal ion concentration of 2500 ppm and a bath temperature of 50″C.
13 for 6 minutes, and further immersed in an aqueous solution containing 0.5
The laminate was immersed in a mixed solution of mol/# of sulfuric acid and oxalic acid at 30°C for 8 minutes to adsorb the catalyst on the surface of the laminate. 11
After drying at 0°C for 110 minutes, a solder resist film was formed on the surface of the laminate other than the null-hole areas and the areas where plating was to be deposited, using solder ink manufactured by Kasha in Tokyo. Immersed in the same electroless copper plating bath as in Example 2 for 15 hours,
A plating film of μm was formed. After forming the plating film, insulation resistance was measured, and no abnormality was found.

Example 4 Holes were drilled in a glass epoxy copper-clad laminate using a dowel. The necessary circuit parts and through-hole parts were masked using DuPont's Riston 1220. Excess copper was dissolved and removed using a cupric chloride solution. After peeling off the resist, degreasing was performed using a cleaner Sekyuri Gant 902 manufactured by Schering Co., Ltd. at 40°C. Next 1.8
The copper surface was soft etched by immersing it in a 45°C mixed solution consisting of mol/It of sulfuric acid and 2 mol/e of hydrogen peroxide for 2 minutes. 1.8mol/g1 in sulfuric acid aqueous solution at room temperature
It was soaked for a minute to dissolve the scum on the copper surface. A 0.6 m
The plate was immersed for 4 minutes in a mixed solution K at 40°C consisting of ol/l of a porium hydride compound and 0.1 mol/l of sodium hydroxide to adsorb the catalyst on the surface of the laminate. 110°C110
After drying for a minute, a solder resist film was formed on the surface of the laminate other than through-hole areas and areas where plating was to be deposited using solder ink manufactured by Tokyo Ohka Co., Ltd. It was immersed in the same electroless copper plating bath as in Example 2 for 15 hours to form a plating film of about 80 μm. After forming the plating film, insulation resistance was measured, and no abnormality was found.

As described above, the method for manufacturing a printed circuit board according to the present invention can omit the step of removing excess catalyst adsorbed on the surface of the laminate, so the manufacturing process can be simplified.
By adjusting the amount of catalyst to be adsorbed, it is possible to prevent a drop in insulation resistance between circuits, and compared to conventional methods, the area covered by electroless plating is smaller, which has the advantage of lower manufacturing costs. .

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a printed circuit board substrate used in the manufacturing method of the present invention, and FIGS. 2 to 7 are vertical cross-sectional views of product components in the order of steps in the manufacturing method of the present invention. . Figure 8 is a circuit diagram for measuring insulation resistance. In the above drawings, 1... Insulating plate 2... Electrolytic copper foil 3... Hole 4... Etching resist 5...
... Catalyst layer 6 ... Solder resist film 7 ...
...Name of electroless copper plating film patent applicant IBIDEN Co., Ltd. Representative Jun Taga 〆/l 〆2g gu3I

Claims (1)

[Claims] 1. After forming through-holes at predetermined positions on the #11 clad laminate, the copper foil other than the desired circuit is dissolved and removed by etching, and a circuit is formed in accordance with the through-hole. The laminate is sequentially immersed once in a reducing solution capable of reducing metal ions that can serve as a catalyst to metal, and the entire surface of the laminate including the through-holes is coated with a catalyst,
In a method for manufacturing a printed circuit board in which a circuit is formed by selectively applying electroless plating only to desired portions,
When applying a catalyst, the metal ion concentration of the aqueous solution containing metal ions that can serve as the catalyst is 2000 to 2500 pp.
The immersion time of the laminated plate was controlled within the range of 4 to 6 minutes, the bath temperature was controlled within the range of 40 to 50°C, and the solute concentration of the reducing solution was controlled within the range of 0. 01~l molA
The temperature of the bath is within the range of 20 to 50''C, and the immersion time of the laminate is controlled within the range of 2 to 10 minutes, thereby increasing the amount of catalyst and force adsorbed onto the surface of the laminate. A method for manufacturing a printed circuit board, characterized in that the total amount that can be used as a catalyst is 0.15 mg, Qnd or less. 2. The aqueous solution containing metal ions that can serve as a catalyst is
d0g2SnCj! 2-HCI (colloid type)
, Pd(J2SnC#2NaC# (colloid type)
2. The method according to claim 1, wherein the radium is any one selected from organic radium complex salt compounds. 3. The reducing solution is an aqueous solution containing at least one selected from nitric acid, oxalic acid, sodium hydroxide, sodium carbonate, and borohydride compounds. The method described in section.