JPH06260741A - Manufacture of metal base circuit board - Google Patents

Abstract

PURPOSE:To obtain a metal base circuit board high in wire bonding reliability by a method wherein the surface of a copper circuit is controlled in average roughness as prescribed, smoothed, and then plated with nickel. CONSTITUTION:A copper circuit 3 is formed on a metal base board 1, and only a masked part of the circuit 3 to be plated with nickel is etched with a mixed solution of sulfuric acid 0.005 to 0.03 (g/cc) in concentration and hydrogen peroxide 0.04 to 0.2 (g/cc) in concentration to make the surface 7 of the copper circuit 3 equal to 1.0mum or below in roughness (Rz; JIS). Then, the copper circuit 3 is partially or totally plated with nickel 4 as thick as 0.1 to 50mum through an electroplating or an electroless plating method. An aluminum wire 6 is bonded to the nickel-plated surface of the copper circuit 3 through an ultrasonic bonding method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a metal base circuit board used for electronic parts such as electric equipment, communication devices, automobiles and the like.

[0002]

2. Description of the Related Art In recent years, a large amount of metal base circuit boards have been used as circuit boards for mounting electronic components. These metal base circuit boards include those having an insulating layer formed on a base metal board made of aluminum or the like, and having a copper / aluminum bonding foil thereon, or a circuit having a copper foil plated with nickel. Among them, a copper foil whose surface is nickel-plated is used for various purposes because it is easy to control in manufacturing and has good oxidation resistance.

Conventionally, when manufacturing a metal base circuit board having a copper circuit whose surface is nickel-plated, the surface of the copper circuit is simply physically polished with a cloth or the like before applying the nickel plating. It was only degreasing with the solution.

Therefore, the surface roughness of the nickel plating applied on the copper circuit is affected by the surface roughness of the underlying copper foil, and is usually as large as about 1.5 μm or more, and ultrasonic Al wires are bonded. There was a problem in that the bonding reliability was low.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and in a metal base circuit board having a copper circuit plated with nickel, the surface of the copper circuit before plating is treated with sulfuric acid. The inventors have found that the surface roughness can be adjusted and the wire bonding reliability can be improved by etching with a mixed solution of hydrogen peroxide, and the present invention has been completed.

[0006]

The feature of the present invention is that the surface of a copper circuit formed on a metal-based insulating substrate is etched by using a mixed solution of sulfuric acid and hydrogen peroxide, thereby forming a surface of the copper circuit. The average roughness (R _z ) of the above is set to 1.0 μm or less, and then the surface of the copper circuit is nickel-plated to produce a metal-based circuit board.

The present invention will be described in more detail below. The metal base insulating substrate used in the present invention is 0.3
~ 5.0 mm thick aluminum, aluminum alloy,
30 ~ on a metal plate such as copper, iron, stainless steel, invar
An insulating material such as a glass epoxy resin having a thickness of 500 μm or an epoxy resin filled with an inorganic filler is laminated. Then, after 0.031 to 1.0 mm of copper foil is laminated, the copper foil is etched to form a desired copper circuit.

Of the copper circuit on the metal base substrate thus formed, only the portion to be plated with Ni was masked, and the sulfuric acid concentration in the mixed solution was 0.001 to 0.1 (g / cc).
), A mixed solution having a hydrogen peroxide concentration of 0.01 to 0.4 (g / cc), preferably a sulfuric acid concentration of 0.005 to 0.03 (g / cc).
), And a hydrogen peroxide concentration of 0.04 to 0.2 (g / cc) was used for etching to obtain a copper surface roughness (Rz; JI
S method) to be 1.0 μm or less and smooth.

The etching method may be either a dipping method or a spray method. The temperature of the etching liquid is preferably room temperature to 60 ° C., and the treatment time is suitably 3 to 20 minutes. If the temperature of the liquid is 40 to 60 ° C., it can be produced in a short period of time, which is efficient. Next, electrolytic or electroless nickel plating having a thickness of 0.1 to 50 μm is applied to a part or the entire surface of the copper circuit.

An aluminum wire is bonded to the nickel-plated surface of the copper circuit thus formed by ultrasonic bonding. The thickness of this aluminum wire is 25 to 5
00 μmφ is generally used for connection with a semiconductor chip or other nickel-plated surface.

[0011]

FUNCTION AND EXAMPLE In the present invention, by adjusting the roughness of the copper circuit surface and smoothing it, it becomes possible to smooth the nickel-plated surface applied on the copper circuit.
Therefore, the aluminum wire and the nickel-plated surface can be easily bonded by ultrasonic waves. Therefore,
It has become possible to improve the bonding reliability in ultrasonic wire bonding.

Next, the structure of the metal base circuit board according to the embodiment of the present invention will be described with reference to FIGS.

[Example 1] 3.0 mm on the metal base plate 1
A thick aluminum plate is used, on which an insulating layer 2 of 80 μm is formed.
A copper circuit having a thickness of 105 μm was laminated on the copper foil by etching, and a copper circuit was formed by etching. Add this to 0.01% sulfuric acid at a temperature of 55 ° C.
(G / cc) and 0.08 (g / cc) hydrogen peroxide were soaked in a mixed solution for 8 minutes, so that the surface of the copper circuit having an average surface roughness (Rz) before treatment of 4.0 μm was 0.02. 6 μmφ (Rz
The average surface roughness of 7) was smoothed. The surface roughness was measured by "Surfcoder-SE-30D" manufactured by Kosaka Laboratory Ltd. at a feed rate of 0.1 mm / sec and expressed by JIS; Rz method. After this, the entire surface of this copper circuit is electroless plated to 4
A nickel plating 4 having a thickness of μm was applied. And on the surface of this nickel plating, "USW-2" manufactured by Ultrasonic Industrial Co., Ltd.
0ZD60S-C ”bonding machine is used to load 3
300g under the condition of 00g, output 1.8W, output time 0.4 seconds
1000 μmφ aluminum wires 6 were wire-bonded. As a result, the number of defective bonds was zero.

Example 2 A copper plate having a thickness of 1.0 mm was used as a metal base plate, and a copper plate having a thickness of 150 μm was placed on the copper plate.
A pattern was formed by laminating a copper foil of μm and etching. Sulfuric acid 0.02 (g / cc), hydrogen peroxide 0.14
By immersing in a mixed solution containing (g / cc) at 30 ° C. for 4 minutes, the average surface roughness (Rz) before treatment was 2.0 μm.
The surface of the copper foil of m was smoothed to 0.8 μm (Rz).
Then, part of this circuit pattern is electroless plated to 3
A μm thick nickel plating was applied. Then, 1000 aluminum wires having a diameter of 300 μm were wire-bonded to the surface of the nickel plating under the same conditions as in Example 1.
As a result, the number of defective bonds was zero.

[Comparative Example 1] A 3.0 mm thick aluminum plate was used as a metal base plate, a 105 μm copper foil was laminated on this with an 80 μm insulating layer interposed therebetween, and a pattern was formed by etching. At this time, the average surface roughness (Rz) of the copper circuit
Is 2.0 μm, and 4 μm thick electroless nickel plating was directly applied to the entire surface of the copper circuit. Then, 1000 aluminum wires having a diameter of 300 μm were wire-bonded to the surface of the nickel plating under the same conditions as in Example 1. As a result, the number of defective bonds was eight.

[0016]

According to the present invention, by adjusting the average roughness of the surface of the copper circuit and smoothing it, it becomes possible to smooth the surface of the nickel plating applied on the copper circuit.
Ultrasonic wire bonding between an aluminum wire and a nickel-plated surface can be easily performed, and high wire bonding reliability can be obtained.

[Brief description of drawings]

FIG. 1 shows a part of the manufacturing process of the present invention. It is sectional drawing of the metal base circuit board of the step which formed the copper circuit.

FIG. 2 shows a part of the manufacturing process of the present invention. It is sectional drawing of the metal base circuit board which carried out the nickel plating on the copper circuit.

FIG. 3 is a cross-sectional view of a metal base circuit board subjected to ultrasonic aluminum wire bonding.

[Explanation of symbols]

 1: Metal base substrate 2: Insulation layer 3: Copper circuit 4: Nickel plated part 5: Semiconductor 6: Aluminum wire 7: Copper circuit surface with adjusted average roughness

Claims (1)

[Claims] 1. The average roughness (R) of the surface of the copper circuit is formed by etching the surface of the copper circuit formed on the metal base insulating substrate with a mixed solution of sulfuric acid and hydrogen peroxide.
_z ) is 1.0 μm or less, and then the surface of the copper circuit is nickel-plated.