This message is, I guess, mostly of interest to Steve, since it's a PCB
layout issue.
The number one improvement I'd like to see on the next version of Balloon
isn't a feature at all, but a tweak to the PCB pad pattern for the resistor
networks. Soldering problems on those are by far the dominant cause of
production problems. Having been to visit Barric last week with John and
discussed this with them, there seem to be two things going wrong:
1. The present batch of bare boards have some registration problems which
mean that the solder paste tends to find itself in places it shouldn't,
resulting in shorts between pins of the resistor packs. We anticipate that
these will clear up with the next batch of bare boards, so this probably
isn't a design issue so much, although a change to the pad shape will help
to solder flow back to where it should be.
2. There is a problem with the solder paste just never making it to the pin
of the resistor pack, resulting in an open circuit. Although the pads are
not the smallest on the board, being bigger than the BGA ones for example,
the res packs' pins don't carry any solder of their own (unlike the BGAs). I
confirmed with Barric that lengthening the pads for the res packs would
enable them to hold more solder paste and thus get a more reliable joint.
Anyone know of any reasons I haven't thought of why this is a bad idea?
Chris
--
Chris Jones -
chris@martin-jones.com
148 Catharine Street, Cambridge, CB1 3AR, UK
Phone +44 (0) 1223 474968 Fax +44 (0) 870 112 3908
http://www.martin-jones.com/
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