On Thu, 31 Mar 2016 04:20:59 -0400, "Michael A. Terrell"
wrote:


Jeff Liebermann wrote:

On Sat, 26 Mar 2016 19:56:12 +0000 (UTC), Andre Majorel
wrote:

Sorry for the delay but I missed the followups to my comment.

On 2016-03-22, Jeff Liebermann wrote:

If it uses an MLCC capacitor, use a hot air gun to reflow, not
a soldering iron tip.

News to me. In what way are multi-layer ceramic caps and
soldering irons incompatible ?

Thermal shock easily cracks MLCC caps. I learned that the hard way
while fixing several Apple Mac Mini computahs, which feature a
collection of MLCC on the bottom of the main board.
https://web.archive.org/web/20130606062903/http://blog.helpmymac.ru/?p=3585
The original failure mode was shorted MLCC caps caused by either
thermal shock or board flex. The bad ones were easy to find with an
ESR meter. However, when I tried to install replacements (and
guessing the part value because Apple doesn't supply service
information to non-authorized repair shops), I managed to crack and
short several known good MLCC caps with a soldering iron. Having
learned the lesson, I used some solder paste and a hot air SMT reflow
gun to do the soldering. I also pre-heated the PCB and let the caps
cool down slowly. I don't know if that was necessary, but it worked
every time. I'm told that two solding irons used as a tweezer also
works, but I haven't tried that yet.

How were the new caps stored? If it is where they can adsorb
moisture, you can damage them with an iron that is too hot.

I haven't had any problems with cracking but I used to have problems
with end caps falling off. I haven't seen the issue for some time,
though perhaps it was a problem with the manufacturer. Our purchasing
group prefers Murata, so that's what I use (GRM series).