CS251517B1 - Method of lead-semiconductor system soldering - Google Patents

Abstract

The method of soldering the supply-semiconductor system to achieve optimal thermal-mechanical system network properties where ispájika is applied to a semiconductor ■ Handles, before etching the semiconductor. U such solder systems often also serve defining the geometric dimensions of a semiconductor .folding. In such a case it is The choice of.the.control network is very limited. Ingredient to improve thermal mechanics solder properties such as (for example silver, it is possible to add it to the solder at soldering from surface finish. U ■ Particularly demanding semiconductor components on the thermo-mechanical properties of the joint as for example, a protection diode, corrosion is possible reduce solder by using an etchant composition nitric acid + hydrofluoric acid -J-acetic acid (20 to 85%): (1 to 40%): (1 to 30%).

Description

The invention solves the perfect soldering of the lead-semiconductor system where the solder is etched together with the semiconductor. In this case, the thickness and material of the coating of the lead are diluted by the need for alloying and soldering.

In the production of semiconductor elements, the method is used where the solder is also used alcohol protection to define the geometric dimensions of the semiconductor, or mainly in the case of flat smaller semiconductors, it is applied there for easy assembly. It is necessary to use solders which are resistant to etch that etch the semiconductor. This limits the choice of the solders to be used and it is not possible to select the solder with a suitable for the heat-metering properties of the soldered joint.

In order to ensure good cooling of the semiconductor system, copper leads which are surface-treated by nickel-plating or gold-plating are generally used. However, during soldering, this coating reaches the solder, which is usually PibSn (10-0.5), and both nickel and gold impart porosity or embrittlement.

The nitric acid-.beta.-hydrofluoric acid ethers used also have no beneficial effect on the thermo-mechainic properties of the joint. Therefore, in the case of particularly sensitive elements in terms of thermo-mechanical properties, such as protective diodes, the commonly used etching compositions and surface treatment of the nickel or gold lead are inadequate.

The above-mentioned drawbacks are overcome by the proposed method of soldering the supply-semiconductor system, which is characterized in that, in order to improve the thermo-mechanical properties of the joint, the PbSn solder is alloyed during material soldering, e.g. in silver, from the supply conditioning. The thickness of the silver is mainly governed by the necessary degree of deposition. For semiconductor devices particularly sensitive to thermo-mechanical properties, the corrosion of PbSn solder by etching the semiconductor is reduced by etching in the etch; nitric hydrofluoric acid + acetic acid iv (20 to 8'5%): (1 to 40%): (1 to 30%), further improving the thermo-mechanical properties of the joint.

By using a silver-coated lead, it is achieved that when the lead-semiconductor assembly is soldered, silver is introduced into the PbSn solder, which cannot be put into the solder before etching. The addition of silver improves the heat-milling properties of PbSn solders.

A further improvement of the isa-semiconductor junction is achieved by etching with an etching composition of nitric acid -j-hydrofluoric acid -j-acetic acid in a ratio of (20 to 85%): (1 to 40%): (1 to 30%).

Good results are obtained, for example, by using copper leads with a pure silver coating, nickel reddish layer, PbSn 5 solder, and acid etching in a mixture of: 65 per centic acid-i-nitric acid-fluoro-j-fluoric acid j (48 percent) -j- acetic acid (1'-gonic acid) at a ratio of 64.5%: 22%: 13.5%.

The invention can be used in the manufacture of semiconductor elements in which the solder is etched together with the semiconductor, and therefore, in choosing the solders to be used, a trade-off between the requirement of the solder resistance to etching and the heat-mechanical properties of the solder.

Another advantage of the proposed method is the saving of gold. The cost of silver is richly balanced by the savings and advantages of the proposed method, and therefore the total cost of production in the proposed method is lower than the method used hitherto.

Claims (3)

1. A lead-semiconductor soldering system for systems wherein the solder is etched together with an etched semiconductor, characterized in that another improvement of the thermo-mechanical properties of the solder is soldered when soldering with silver from the lead finish. 2. The feed-semiconductor soldering system according to claim 1, characterized in that the improvement of the thermo-mechanical properties of the connection is achieved by silver from a locally silver-plated lead. 3. A feed-semiconductor soldering system according to claim 1 or 2, characterized in that, in order to further improve the thermo-mechanical properties of the joint, an etching agent in the composition of nitric acid - | - hydrofluoric acid -. to 85%]: (1 to 40%): (1 to 30 ° / o).