There are over 200 solder alloys used to bond copper, gold, nickel, and silver surfaces. Very few of those solders can bond what we consider ‘difficult’ surfaces like cobalt, titanium, and silicon. Last week we discussed my favorite list of compatibility, which comes from a study by Richard B. Belser of Georgia Institute of Technology sometime in the 1950’s. The study is named “Indium – A Versatile Solder to Metals and Non-Metals” and can be found in the second edition of “Indium”. This study does not claim to be the first to experiment with soldering to ‘difficult’ metal surfaces, but it does include some surprises.
As discussed last week, all the specs of the testing are included in the study, including the method of soldering used, and a definition of what constitutes a wetted surface in this testing. The substances which were soldered were broken down into three categories: 1) metals and alloys, 2) thin metal films, and 3) non-metals. Only substances that were successfully soldered are on the list.
Here is a list (from the study) of metals and alloys that can be soldered with indium:
- Stainless Steel
During my time fielding technical inquiries for Indium Corporation I remember many of these potential surface finishes being discussed with customers. In particular, the ability of indium to solder to stainless steel or iron is counter-intuitive to most people. Our Technical Service Team helps customers solder to these interesting surface finishes on a regular basis.
If you are looking to learn more about this study, here is a link to purchase a copy of the book “Indium”. To discuss using indium in your application (or soldering to a surface finish that isn’t on this list), contact us at AskUs@Indium.com.