Ask Helena & Leo

Question: Hi Leo, I have never come across soldering on platinum before, are there any soldering techniques you can recommend? Is it like soldering with lead free, should and can RA or similar flux be used, also what is the recommended tip temperature? This is for customer who’s products are type “critical” although not Class 3 but critical for gas detection. What tips do you have on brass surfaces?

Answer: This is an interesting question regarding the soldering to the metal platinum. Platinum is a precious metal used in the jewelry business and in special applications. There is not much information as to the soldering to platinum.

The research I’ve done discusses the use of platinum in jewelry and the primary discussion is to keep it clean to prevent contamination by other metals.

The typical elements to consider when soldering to any metal is to evaluate the performance of the flux in allowing the solder to wet to the basis metal. This will answer the question of wetting. The second point is the type of soldering needed, such as high temp like brazing, or low temp using existing lead free solders. As for the soldering temperature to use, start with the existing temperatures such as 650 to 750 F and observe the wetting action. I would also recommend an experiment to check for solder joint strength and a microsection to see how the intermetallic is created with the tin and the platinum.

Thirdly, depending upon the flux selected, evaluate the cleaning necessary to remove all flux residues. This is an important step as perhaps the flux will be a most aggressive material and will need to be completely removed to prevent reliability issues in the short and long term of the operational environment of the product.