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Locate the bottom driver chip on the board, it’s just below the 104 resistor that you just
mounted. Lightly tin the upper-right pad on the board.
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Remove one of the driver chips from its carrier. Look at the writing with a
magnifier… you will notice that there is a “ST” logo on the top-left corner of the chip. That is
the Pin 1 mark, which must align with the little box in the top-left corner of the driver chip
marking on the PC board.
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Place the driver chip on the board, and hold it in place while heating up the previously
tinned upper-right pad. Make sure that the chip is centered on all eight pads, then carefully
remove the soldering iron and wait 5 seconds for the solder to cool.
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Carefully solder the lower-right pad. Check the pad with a 10x jeweler’s loupe to
make sure that the solder joint covers both the lead of the chip and the pad on the PC board.
It’s very easy to get solder on the chip’s lead but miss the PC board pad; a good solder joint
should actually flow underneath the chip lead and bond the “elbow” of the lead to the pad.
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Now, solder the remaining leads in the same manner. You may have to go back and
resolder the first lead (the one that you tinned earlier).
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Go back and check all of the leads with a 10x jeweler’s loupe, and retouch as
necessary.
Mount the Processor
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Orient the board so that it’s pointed vertically, with the previously-soldered
componetnts on the bottom.
