|PJRC.COM Offline Archive, February 07, 2004
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This board differs slightly from rev A, as I discovered a few errors in the layout, which were of course corrected for rev A.
Nearly all of the lines on this board are 15 mil (0.015 inch, 0.38 mm) wide, with 10 mil (0.01 inch, 0.25 mm) separation. The only exception is on the solder side where the connections are made to the 44 pin laptop drive connector. The board must be etched with a process that can reproduce 15 mil lines with 10 mil separation. Most hobbyist photoresist-based methods can acheive this if done properly, but iron-on techniques are questionable for this resolution.
When assembling the board, many connections are made on the component side of the board. This poses a serious problem for soldering the PLCC sockets and SIMM socket. I used single-pin insert sockets, which are visible in the photo between the microcontroller and flash rom (the two smaller PLCC chips) and the large FPGA chip. They must be soldered on both sides for many locations, and soldering on the top is tricky, as a slight wrong movement will flood the socket with solder. These single-pin inserted sockets are available from Digikey (TODO: find exact part number I used). Unfortunately, they are expensive, but there is little other choice. They also require special PLCC sockets with narrow pins.
If you do manage to build the board by etching it yourself, please consider sending a photo or two to add to the User Photo Gallery.