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Reply To: | TechNet E-Mail Forum. |
Date: | Thu, 27 May 1999 10:12:30 +0000 |
Content-Type: | text/plain |
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Gents/ladies
I have been presented with a new product that gives me some concerns.
The problem (as I see it) is as follows:
We have a PCB which is attached to ten or so pins on a mounting base.
The PCB is standard 1.6mm FR4, about 150mm square. Its ONLY mechanical
support comes from sitting vertically on the joints discussed below. The
pins are pretty large from a thermal mass point of view (large amount of
copper at the other end of the pin, basically a spring clip).
Now in itself this may not sound odd, and its a little difficult to
explain the problem, but here goes. the pins are presented to the PCB
sideways on (the side being approx. 1mm thick). The PCB has no inner
layers and is only populated on one side (PTH and SMD). The pin is
presented into a slot in the board which has pad surrounding it on both
sides. the slot is not plated, it is bare FR4. The pin projects onto the
pads by approx. half mm. This is then soldered (by hand) to both pads,
the resulting joint looks poor to me with signs of crabby wetting between
the pad and the pin (possibly due to the large thermal mass of the pin).
Mechanically I think this joint is a dog (some modules only have pad on
one side of the PCB!). The unit will be exposed to daily thermal cycling
(it is exposed outdoors) as well as heavy vibration (railway Trackside,
with the PCB held upright ontop of the pins). any one share my concerns,
maybe recommend a good test/sectioning house to explore this.
Oh and Ps this is safety critical kit believe it or not
Ian Squires
Production Engineering Manager
Redifon MEL, Crawley, UK
Tel: 44 (0) 1293 466300 xT 2425
--
Ian Squires [log in to unmask]
http://www.rmel.com Tel: +44 (0)1293 446300
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