JPH03294494A - Formation of film on surface of heat radiating plate - Google Patents

Abstract

PURPOSE:To suppress the contamination of the surface of a heat radiating plate of copper by adding specified amts. of saccharin and 2-butyne-1,4-diol as brighteners to a Watts bath as an Ni plating soln. and subjecting the surface of the heat radiating plate to semi-bright Ni plating in a specified thickness. CONSTITUTION:Saccharin as a primary brighener and 2-butyne-1,4-diol as a secondary brighener are added to a Watts bath as an Ni plating soln. by 2.0-3.0g/l and 0.007-0.02g/l, respectively. The surface of a heat radiating plate based on copper or iron is subjected to semi bright Ni plating in 3-9mum thickness with the plating soln. Surface treatment suppressing the contamination of the surface of the heat radiating plate is performed, the suitability of flux to washing is improved, fingerprints are nearly prevented from being left on the plate and a heat radiating plate useful for a power transistor module, etc., is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to surface treatment of a heat sink on which electronic components are mounted, such as a heat sink used in a power transistor module. More specifically, the present invention relates to a surface treatment method for applying semi-bright plating by adding additives to a conventional matte nickel plating solution in order to improve surface stains on heat sinks.

[Conventional technology]

Conventionally, power transistor module components, such as transistor chips, electrodes, terminals, etc., have been soldered to heat sinks made of copper, iron, or the like using flux-cored eutectic solder. And, on the surface of this heat sink, there is no soldering,
Currently, Watt-type matte nickel plating is applied to provide corrosion resistance.

[Problem to be solved by the invention]

In this way, conventional heat sinks are made of matte nickel, so
Because the particles on the plating surface are coarse, it is difficult to clean the solder flux, and the surface of the heat sink is easily contaminated due to the adhesion of fingerprints during handling. It is necessary to carry out wiping work using solvents, but there are problems such as contamination of the working environment caused by these solvents,
There were problems such as higher product prices due to increased labor costs associated with wiping.

This invention was made in order to solve the above-mentioned problems, and provides a surface treatment that has excellent solder flux cleanability, can prevent fingerprints from being attached during handling, and can reduce contamination on the surface of the heat sink. The purpose of this invention is to obtain a surface coating for a heat sink that can eliminate the use of harmful substances such as trichlorethylene and trichloroethane and improve wiping work.

[Means to solve the problem]

That is, the present invention adds saccharin 2.0 to 3.0ti/1 as a primary brightener to a Watt type matte nickel plating solution.
．． 2-butyne-1,4 diol 0.07 as secondary brightener
It is characterized by applying semi-bright nickel plating to a thickness of 3 to 9 μm on the surface of a copper or iron-based heat sink by adding ~0.02971 and electroplating under normal conditions.

[Effect]

The semi-bright nickel film on the surface of the heat sink in this invention is
0.00 2-butyne-1,4 diol as a secondary brightener
By adding 7 to 0.02 g/l, the precipitated surface particles are made finer, which improves the cleanability of the solder flux and reduces the amount of fingerprints attached.

〔Example〕

Watt type semi-bright nickel plating was carried out on the surface of the heat sink as follows.

The plating solution was prepared using 2509/1 nickel sulfate, 50 g/l of nickel chloride, and 30 g/l of boric acid as a base solution, and after making the usual adjustments for nickel plating, 2.3 tt/1 of saccharin was used as the base solution. , after making the usual adjustments, add 2.3tt/1 saccharin, then 2butyne-
0.01 g/i' of 1,4 diol was added to prepare a plating solution. For plating, the oxygen-free copper plate was degreased, treated with Kirins, and activated, then at a plating temperature of 50°C and a current density of 1.8A/
Semi-bright nickel plating with a thickness of approximately 4 μm was applied at a pH of 4.1 and without stirring.

When power transistor module components such as transistor chips, electrodes, and terminals were soldered to the semi-bright nickel plating on the surface of the heat sink obtained as described above, good soldering was achieved, equivalent to conventional matte nickel plating. showed gender. Furthermore, since the surface particles were fine and the surface was semi-glossy, the solder flux was easily cleaned, and no flux residue was observed. Furthermore, no fingerprints were deposited during handling during the subsequent assembly process. Furthermore, although there was very little dirt adhesion during each process, the dirt that had progressed over time could be recovered to the surface of the heat sink before assembly by simple wiping with methyl alcohol or isopropyl alcohol.

Further, in the above embodiments, the heat sink material is an oxygen-free copper plate, but other copper-based materials or iron-based materials may be used, and the same effects as in the above embodiments can be achieved.

〔Effect of the invention〕

As described above, according to the present invention, the surface film of the heat sink is made of stain-resistant semi-bright nickel plating, which replaces the use of toxic substances such as trichlorethylene and trichloroethane for wiping with methyl alcohol. or at the same time can be changed to isopropyl alcohol
Since the wiping work becomes easier, the labor costs associated with the work can be reduced, and the unit price of the product can be reduced.

Agent: Zeng I Michi Indication of written amendment case Patent application No. 1994-94947 Name of the invention Relationship to the case concerning the person amending the method for forming a surface film on a heat sink Patent applicant address 2-chome Marunouchi, Chiyoda-ku, Tokyo Number 2 and 3 Name (601) Moriya Shiki, Representative of Mitsubishi Electric Corporation

Claims (1)

[Claims] A plating solution containing 2.0 to 3.09 g/l of saccharin as a primary brightener and 0.007 to 0.02 g/l of 2-butyne-1,4 diol as a secondary brightener is added to a Watt type nickel plating solution. on the surface of a copper or iron-based heat sink.
A method for forming a surface film on a heat sink, characterized by applying semi-bright nickel plating to a thickness of 3 to 9 μm.