Indium Blog

Step Soldering Opportunities with Durafuse™ LT

One of the things I love about Durafuse™ LT is how the reflow temperature fits in to a "gap" where previously manufacturers didn't have many options. This temperature range (200-210℃) is also interesting because it provides new opportunities for step soldering.

Step soldering is a common process in PCB Assembly (Meagan's blog talks a bit more about how often this can be relevant). Components that contain soldered joints themselves may be at risk when using the same solder alloy (or one with a similar melting point) in later reflow processing. There are higher temperature alloys such as BiAgX or high-Pb materials that already get used in these situations, but having lower temperature "steps" can open new doors for PCB complexity. 

The more stacking and complex a PCB is, the more likely there is to be some component, material, or connection which is temperature sensitive. Perhaps the concern is solder extrusion after underfill, or a heavy component on a double sided assembly.  Whatever the case, printing and reflowing multiple solder pastes starting from the highest temperature alloy and moving down to the lowest, is a valuable tool. 

Durafuse™ LT however, can be used as a "second step" after SAC reflow (providing drop shock reliability that other low-temperature alloys lack), as well as the "higher step" BEFORE another lower temperature alloy is used. Some processes cannot handle SAC temperature reflow at any stage, but with Durafuse™ LT step soldering is still possible. 

I really believe that developing new materials drives our industry towards new innovations and opportunities.