Navy submarine transformer solder joint failure

Raytheon's Waltham defense facility was making transformers for nuclear submarine control rod actuators ($1M apiece). Specified solder was 95Pb-5Sn (melts ~300°C). A technician used 63Sn-37Pb eutectic solder (183°C) instead; during the 200°C post-pot thermal soak, liquid metal seeped out through a feed-through. Four transformers ($4M) sitting in the furnace. Pencil tests showed the joint actually didn't fail until 300°C — TLP soldering had occurred (tin diffused into copper, leaving lead-rich solid). Tom wrote a one-page letter explaining this as TLP diffusion soldering; Navy accepted the parts. Tom: "I think I made $700 on the deal."

Another story of TLP bonding, which is actually TLP soldering. I get a call from Raytheon. This was in a plant right out here in Waltham. One side of the road is now a BJ's Warehouse; the other side of the road is the building with the World Club Gym and SGH. There used to be a Raytheon facility where they made defense components, and they've since torn down both those buildings. They actually had a crosswalk on the second floor across the road. You'd come in on the east-side building, go upstairs, walk over, and come into the manufacturing facility where the SGH building is now.