On 13/01/2012 18:37, John Rumm wrote:

I was toying with doing a wiki article on component level repair of
electronic stuff, since there seems to be so much otherwise decent kit
that dies these days for silly reasons like failing capacitors etc.

With modern lead free solder, and ever increasing layout densities, use
of multilayer boards etc, the job of component removal seems to be
getting ever harder. There was a time when a moderate iron with enough
bit mass to heat the joint quickly, was all you needed. To reflow the
joint and then either pull the device, or apply a solder sucker, all one
did was tin the bit, apply heat for a couple of secs, and job done.

Recently I have needed to recap a few motherboards (not usually an
economic exercise - but these were custom form factor jobbies where
replacements are not readily available), and they were a right PITA to
work on. Obviously multilayer, and since the caps are on the power
regulation sections, probably connected to fairly heavy power plane
traces in the board. Component removal was very difficult - often taking
excessive time for the joint to reflow. Tight pins in close holes with a
small annulus. However cleaning the holes for reuse proved impossible
with any of my normal irons. In the end I had to resort to using a hot
air paint stripper with small nozzle on the end to get enough heat into
the area to be able to suck the holes clear!

I was wondering what suggestions those of you who do this daily had to
offer?


I have a cheap hot-air SMT rework station (ebay) which is quite
effective at individual component removal on multi-layer boards. I
usually have the smallest tip fitted which has about a 4mm hole.
I use the same method for SMT ICs, run the air-flow around the pins
until the chip is free, then flip it over with a knife or similar.
Clean pads with decent solder wick and fit replacement, typically by
flow-soldering by hand all the pins on each side of the IC in turn.

Capacitor failure seems to be far worse than it used to be, when I
worked in electronic repair (~15 years ago) I rarely had any issues with
caps, but now it's one of the first things I look for, especially in
SMPSUs, monitors & TVs.