Indium Blog

Low-Temperature Solders: Important, Valuable

New developments are happening almost daily in the electronics device world: phones that do much more than just convey voice, clothing that monitors and sends the body's vital statistics to physicians, and the all encompassing "Internet of Things" that will integrate electronics into every aspect of our daily lives (if we're not there already).

New electronics assembly processes are being developed to build these wonderful devices, allowing designers to put ever-more functionality into increasingly smaller spaces.

Ever since the first component was soldered into place on the first circuit board, we have used tin-based solders: first SnPb and SnPbAg and, more recently, SAC (SnAgCu) alloys to comply with the RoHS and other regulations banning the use of lead.  

As I have mentioned in previous blog posts, tin can be alloyed with other materials, most notably indium or bismuth, to provide a range of low-temperature solder alloys that reflow below the 170-220°C range that have become industry standards.

Why would you need low-temperature solders?  There are at least four pretty obvious reasons:

  • Your components are temperature sensitive, and reflowing them at common temperatures will destroy your component before it even leaves your factory.
  • You need to step solder.  This is a process in which in which successive joints in an assembly are joined with solders of successively lower soldering temperatures, so that the previously soldered joints are not disturbed.
  • You are soldering to a non-traditional substrate (like the 3D MID materials) that cannot withstand the higher temperatures without incurring damage.
  • You are soldering two materials that have very different coefficients of thermal expansion and are trying to minimize the temperature excursion during reflow.

But, of course, there is more to know about low-temperature bismuth and indium alloys than just their melting temperatures.  These alloys each have their own unique physical, mechanical, and soldering properties.  Indium Corporation has long been the expert in these low temperature materials and our Vice President of Technology, Dr. Ning-Cheng Lee, will be presenting his expertise with these materials in a tutorial at SMTA International 2014 in Rosemont, IL.  Dr. Lee will cover the things you need to know to make low-temperature solders one of your most important soldering tools.