JPH09246695A - Surface treatment and apparatus of copper pattern on printed circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable prevention of diffusion of tin alloy and copper by electroless plating with nickel to form a nickel plated film having a predetermined thickness on a copper pattern of a printed circuit board, etc., without using expensive palladium, electroplating tin or tin alloy on the nickel plated film and then electroplating it with nickel to form a nickel plated film having a thickness of 2μm or more. SOLUTION: In this method, surface treatment of a copper pattern on a printed circuit board is carried out by electroplating the copper pattern to promote its reaction at the time of starting electroless plating on the copper pattern and thereafter by electroless plating it to form thereon a nickel plated film having a predetermined thickness, and by electroplating the nickel plated film with tin or tin alloy. The apparatus includes an initial electroplating bath 1 for performing its electroplating operation for a short time at the time of electroplating the copper pattern of the printed circuit board with nickel, an electroless plating nickel bath 8, and a tin alloy electroplating bath 10, which are all disposed in a continuos processing positional relationship.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for treating a copper pattern surface of a printed circuit board or the like.

[0002]

2. Description of the Related Art As a surface treatment method for a copper pattern on a printed circuit board, the printed circuit board is conventionally immersed in a molten solder bath,
It has been common practice to blow off excess solder with high-temperature, high-pressure air and apply the solder to the copper pattern. or,
As shown in FIG. 5, nickel has been electrolessly plated by applying an activator such as palladium, and then electroless gold plating has been performed thereon. Further, recently, a method of electrolessly plating a tin alloy directly on a copper pattern has been performed.

[0003]

In the above prior art,
The first method is that the molten solder on the copper pattern rises in the central part due to surface tension and the parts incline and adhere, and it has to be corrected to the normal position with a microscope. However, there was a problem that the solder was clogged and the legs of the component could not be inserted. The second method has an advantage that the thickness can be uniformly plated regardless of the surface area of the copper by controlling the plating time, but it is very difficult to control the temperature of the concentration of the palladium, and if the concentration is too high, the copper cannot be plated as shown in FIG. During the pattern, the palladium remains and nickel is deposited on the entire surface.If the concentration is low, nickel does not deposit.If the pattern becomes highly precise, it is difficult to remove the palladium other than the pattern, and nickel squeeze-out phenomenon occurs and correct nickel is generated. There is a problem that it is difficult to perform plating, and the palladium itself is expensive. Further, the third method has a problem that the tin alloy is plated only to about 0.8 to 1 μm, copper and tin are diffused, and the outer shape processing after plating is difficult.

[0004]

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned problems, and at the start of electroless nickel plating on the surface of a copper pattern, the reaction is promoted by electroplating, and thereafter electroless plating is performed to a predetermined thickness. Nickel plating, and the surface treatment method of the copper pattern of the printed circuit board such as electroplating tin or tin alloy on the nickel plating, and short time electroplating on the copper pattern of the printed circuit board at the start of nickel plating. The present invention is characterized by a surface treatment apparatus for a copper pattern on a printed circuit board or the like, in which an initial electroplating bath to be performed, an electroless nickel plating bath, and a tin alloy electroplating bath are continuously arranged.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail based on one embodiment shown in FIGS. 1 is a nickel initial electroplating tank, and a nickel plating liquid tank 2
The nickel liquid is supplied by the pump 3. Reference numeral 4 is a printed circuit board, 5 is a blank cathode, 6 is an anode, and 7 is a feed roller. 8 is an electroless nickel plating bath. 9 is a shower water washing tank. 10 is a tin alloy electroplating tank, 11 is a tin alloy plating solution tank, 12 is a pump, and 13 is a cathode, which is 0.5.
Pins 14 of about 1.0 mmφ are inserted into the holes of the board 15 at intervals of about 1 mm in the board width direction, and each pin 14 is pressed downward by the spring 16. 17 is an anode, 18 is a feed roller, 19
Is a shower flush tank.

Next, the operation will be described. The printed circuit board 4 is supplied into the nickel initial electroplating bath 1 by the feed roller 7. A voltage of 5 to 6 V is applied between the blank cathode 5 and the anode 6, and the blank cathode is brought into contact with the printed board with a soft touch for 2 to 5 seconds. Nickel deposition is promoted by this electric shock, and nickel deposition is continued even if the voltage application is stopped. Then, it is sent into the next electroless nickel plating tank 8 and nickel having a thickness of 2 to 3 μ is plated while passing through this. Next, rinse with water in the shower rinse tank 9,
It is sent to the next tin alloy electroplating bath 10. In this, the printed circuit board 4 is strongly pressed by the pin cathode 13 and stops.
During this period, electricity is applied and electroplating is performed. 1 A / dm ² to 30
By using the tin plating solution in which a current of about A / dm ² flows, no defective plating occurs even if there is a difference in the area of the independent pattern. The pin cathodes 13 are arranged not only in one row but also in three rows, and if current is taken from a separate rectifier and plating is performed, the plating thickness is averaged. Energize for about 5 to 60 seconds, pin cathode 13
Is separated from the printed circuit board 4. This electro-tin plating may leave a pin mark (non-plated part) on the plated surface, but since the printed circuit board is intermittently moved by moving the pin cathode 13 up and down, the non-plated part disappears and the pin mark is not a problem. Also, since the base is plated with nickel of 2 to 3 μm, the diffusion of copper can be stopped. Then, it is washed with water in the shower water washing tank 19 and then dried, and 2 μm is put on the copper as shown in FIG.
The above nickel is plated, and a tin or tin alloy plated printed circuit board is formed thereon.

[0007]

EFFECTS OF THE INVENTION According to the present invention, since electroless plating can be performed by electroplating only at the start in the electroless nickel plating bath and applying an electric shock, the nickel plating bath having a flat surface. Can be formed without the use of extremely expensive paradium,
Further, it can be formed to a sufficient thickness. Nickel serves as a barrier layer of copper and tin alloy and prevents diffusion of copper. Moreover, since it is hard, it protects the copper pattern. If nickel has a thickness of usually 3 μ, tin or tin alloy on it can be reliably soldered even if its thickness is 1 μ or less. Also, since nickel is deposited electrolessly, the thickness can be uniformly plated regardless of the surface area of the copper pattern only by controlling the plating time, so the plating thickness is more uniform than when nickel is deposited only by electroplating. You can get sex.

[Brief description of drawings]

FIG. 1 is a schematic front view of an entire apparatus for applying the method of the present invention.

FIG. 2 is an enlarged view of a main part of the tin alloy electroplating bath of FIG.

FIG. 3 is an external perspective view of the pin cathode of FIG.

FIG. 4 is a sectional view of a plated portion formed by the method of the present invention.

FIG. 5 is a nickel plating sectional view using palladium.

FIG. 6 is a diagram showing a state in which the paradium solution of FIG. 4 has overflowed.

[Explanation of symbols]

 1 Nickel initial electroplating tank 2 Nickel plating solution tank 4 Printed circuit board 5 Blanc cathode 7 Feed roller 8 Electroless nickel plating tank 9 Shower washing bath 10 Tin alloy electroplating tank 11 Tin alloy plating solution tank 13 pin cathode 14 pin 15 board 16 Spring 17 Anode 18 Feed roller 19 Shower Wash tank

Claims (4)

[Claims] 1. At the start of electroless nickel plating on the surface of a copper pattern, the reaction is promoted by electroplating, then nickel plating of a predetermined thickness is applied by electroless plating, and tin or tin alloy is electroplated on the nickel plating. A method for treating a copper pattern surface of a printed circuit board or the like. 2. An initial electroplating bath for performing electroplating for a short time at the start of nickel plating on a copper pattern of a printed circuit board, an electroless nickel plating bath, and a tin alloy electroplating bath, which are successively arranged. A surface treatment device for copper patterns on printed circuit boards, etc. 3. The surface treatment device for a copper pattern of a printed circuit board or the like according to claim 1, wherein a blank cathode that contacts the copper pattern of the printed circuit board to be transferred and an anode are provided in the vicinity thereof. 4. A pin cathode having a large number of pins arranged in the width direction of a printed circuit board is arranged in a plurality of rows so as to be vertically movable.
The surface treatment device for a copper pattern of a printed circuit board or the like according to claim 1, wherein an anode is provided in the vicinity thereof.