Gallium arsenide TLP diffusion soldering (Raytheon student, early 1990s)

Tom had a Raytheon-employed graduate student in the early 1990s who worked on transient liquid phase diffusion soldering of silicon and gallium arsenide chips to substrates — addresses the thermal expansion mismatch problem in electronic packaging.

I started thinking about it and realized that a lot of the joints they were making — they might have been making solder joints with the same old lead-tin solders with copper or gold, but in fact what they're really doing is transient liquid phase diffusion soldering. I had a student from Raytheon in the early '90s, and he came in and we actually worked on transient liquid phase diffusion soldering, to try to join silicon, or in his case gallium arsenide chips to the substrate. Big thermal expansion problems. We'll talk about that stuff tomorrow.