Now that we have a functional proof of concept circuit, we're working to plan out a longer term design for manufacturing. We had heard good things about a local PCBA manufacturer so we setup a meeting and discussed product manufacturability. The place is Hughes Circuits, Inc. and they have an incredible facility where they Manufacture PCBs and assemble products for military applications. Overkill for our device, perhaps, but they're experts and had good input. We met the other day with their BD guy and their FAB lead, shared our prototype and intent for next steps, and absorbed their wisdom. Interestingly, a lot of the discussion came down to reliable part sourcing, testing methodology, and which parts would lend themselves well to certain soldering and cleaning strategies. The relays we're using, for instance, aren't water-tight, which means that submersion cleaning of the boards after assembly would be unwise unless the cleaning step took place prior to the addition of the relays.
The folks at Hughes were helpful in some unexpected ways as well. One of the manufacturing engineers brought up the topic of the thermal connection between the heat-sink and the SCRs. According to him, while the Silver thermal paste was a really good thermal conductor, the manual application of the goop to every heat-sink was going to be more work than something like a thermal pad and more prone to inconsistent application. This kind of manual task obviously makes the work more expensive, growing the cost per unit.
The good new was that they didn't see any serious concerns with the state of the circuit board from a manufacturing point of view. While things like through hole components would add to the cost, the crew at Hughes was generally positive about the overall circuit board design. Now our concerns are shifting to the manufacturability of the enclosure and assembly as a whole. More soon!