The first batch of test boards arrived. Actually two batches did: USPS "misplaced" my first shipment for ten days, but found them again just after OSH Park rush-ordered a replacement set. Here they are:
I have a few projects that have been on hold until these arrived, so I'm excited to test them out. I'll post progress as I do.
These first boards must be glued to the copper-clad backplane. As a next step, I'm going to try some boards with three different ways of soldering to the plane:
- bare pad bottoms skillet-reflowed onto the plane with solder paste
- an outside ring of through-holes to solder to the plane
- castellations around the board perimeter
It turns out that OSH Park supports castellations, so that sounds like the most promising approach, but I'd still like to test all three.
As to which packages to support next, I'm running out of small DIP adapters. Here's a few I used this past weekend:
(Left) A 10-bit DAC is plugged in while I wait for a 12-bit unit to arrive; the adapter board makes mounting a socket on the plane easy. (Right) Half of a DIP8 adapter board makes a convenient mount for a 4-pin header for connections to a daughterboard.
I used another trick on the above prototype to preserve the copper ground plane. I cleaned the copper clad with "Barkeeper's Friend," a scouring powder containing a fine abrasive, then rinsed it thoroughly. Once it dried, I spray painted it with a light coat of clear enamel. This coating protects the copper from corrosion, but is easy to solder through when connecting to the plane: it will keep the boards looking pretty for years to come. I read about this technique a few years ago on Charles Wenzel's site, but haven't been that good about actually doing it. I finally got motivated, and coated a few large pieces of copper-clad, so I can just cut them up with a shear as I need pre-coated pieces.