Re: soldering components on larger sized pads

"Joerg" <notthisjoergsch@xxxxxxxxxxxxxxxxxxxxx> wrote in message
news:ufEqk.34919$co7.12270@xxxxxxxxxxxxxxxxxxxxxxx
The worst stuff I've seen is when designers didn't realize that there was
more current flowing than the trace could handle.

<< chuckle >>

I knew a digital designer who was on a tight schedule to get a fancy new
16-bit microcontroller board done (this was ~15 years ago), so he whipped out
the schematic and asked the PCB layout guy to get it turned into a board ASAP.
PCB guy did so, board came back and... didn't work.

Digital designer man quickly ascertained that the problem was Vcc which,
instead of being the 5V that it was supposed to be, was something closer to
4V. It seems that PCB layout guy -- in the name of saving time -- just told
his auto-router to do the entire board using the default net (8mils, I'd
guess), and the new CPU was rather power hungry (a handful of amps) and pulled
enough current far enough along a solitary 8mil trace to suffer a volt of IR
drop.

Digital designer man ended up having some techs manually solder on some fat
wires in parallel with the power supply traces. :-)

In this case the PCB layout guy arguably wasn't very good, although I'd still
lay blame with the designer for not properly reviewing the layout before he
gave the go-ahead to have the board fabbed.

---Joel


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