Nickel plating and tin-coating annealing process

Abstract

The invention relates to a nickel plating and tin-coating annealing process which comprises the steps of: carrying out first tin-coating on an electro nickelling protective layer at a temperature of 300+ / -5 DEG C, cooling to room temperature; carrying out secondary tin-coating at a temperature 430-435 DEG C, cooling to room temperature; and carrying out third tin-coating at a temperature of 300+ / -5 DEG C. By tin-coating for only three times, the solderability of a copper lead can be kept, the hydrogen embrittlement of the electro nickelling protective layer can be eliminated, and the process is simpler; the first tin-coating temperature is 300+ / -5 DEG C, which can play roles of protecting a nickel-plating layer and preventing the nickel-plating layer from being damaged; the second tin-coating temperature is 430-435 DEG C, which can play a role of annealing the nickel-plating layer at high temperature to ensure that the copper lead has a certain flexibility; and the third tin-coating temperature is 300+ / -5 DEG C, which can play a role of cleaning tin oxides generated by the secondary tin-coating to ensure that the copper lead has more attractive appearance.

Description

technical field [0001] The invention relates to a nickel-plating and tin-lined annealing process, which belongs to the technical field of electronics. Background technique [0002] The processing of plastic-encapsulated transistors includes sticking chips on the copper lead frame that has been electroplated with a protective layer of nickel, wire bonding, encapsulation, flash cleaning, printing, curing, rib cutting, tin annealing, testing and packaging processes. Among the above processes, The tinning annealing process is to ensure that the copper leads have a certain degree of solderability. It needs to be tinned on the electroplated nickel protective layer. The tinning temperature is about 300°C. The nickel protective layer will produce hydrogen embrittlement. Such copper leads will generally break after being bent several times. In order to eliminate the hydrogen embrittlement of the electroplated nickel protective layer and make the copper leads have toughness, at presen...

AI Technical Summary

Problems solved by technology

[0002] The processing of plastic-encapsulated transistors includes sticking chips on the copper lead frame that has been electroplated with a protective layer of nickel, wire bonding, encapsulation, flash cleaning, printing, curing, rib cutting, tin annealing, testing and packaging processes. Among the above processes, The tinning annealing process is to ensure that the copper leads have a certain degree of solderability. It needs to be tinned on the electroplated nickel protective layer. The tinning temperature is about 300°C. The nickel protective layer will produce hydrogen embrittlement. Such copper leads will generally break after being bent several times. In order to eliminate the hydrogen embrittlement of the electroplated nickel protective layer and make the copper leads have toughness, at present, hydrogen furnaces are usually used for annealing. When the temperature range is relatively narrow, it is not easy to control, the lead wire will become soft when the temperature is high, and it cannot be annealed when the temperature is low, resulting in defective products