Bad capacitor plague victim

  If you don't know what I'm referring to, go here:
http://en.wikipedia.org/wiki/Capacitor_plague

Thanks, China.

At any rate, my cousin gave me a HP Pavilion a6333w:

http://h10025.www1.hp.com/ewfrf/wc/document?docname=c01301704&tmp_task=prodinfoCategory&lc=en&dlc=en&cc=us&lang=en&product=3658911

with a MCP61PM-HM motherboard:

http://h10025.www1.hp.com/ewfrf/wc/document?lc=en&dlc=&cc=us&docname=c00906137

He told me that he was having problems with the computer locking up and
shutting down. I took one look at the motherboard and noticed eight,
bulging capacitors, one of them at an angle because of bottom-bulging.

Pretty obvious what's happened here.

At any rate, I was wondering if anybody can recommend a good
micro-soldering iron which doesn't cost an arm and a leg?

TIA

--
John Corliss

 John Corliss wrote:

http://h10025.www1.hp.com/ewfrf/wc/document?docname=c01301704&tmp_task=prodinfoCategory&lc=en&dlc=en&cc=us&lang=en&product=3658911

I thought the plague was over and that it was attributed to a
Taiwanese company, not Chinese.

I haven't been affected by bad caps personally, but have come
across quite a few cases. I manage quite well with a normal-sized
soldering iron. Since motherboards are multi-layer PTH boards,
the trick is to apply the iron tip to the solder point for some
time until the solder in the PTH is melted through. Then pry the
bad cap out, one leg at a time. A 50W iron works better than one
of lower power, especially on the ground side of the caps. A $3
iron works fine for me.

  Pimpom wrote:

http://h10025.www1.hp.com/ewfrf/wc/document?docname=c01301704&tmp_task=prodinfoCategory&lc=en&dlc=en&cc=us&lang=en&product=3658911

"...some bad capacitors were still being sold or used in equipment as of
early 2007, and faults were still being reported as of 2010."


My mistake. However, the original problem was caused by Chinese
nationals according to this article:

http://www.siliconchip.com.au/cms/A_30328/article.html

Specifically mentioned in the section titled "Industrial espionage?"


Thanks very much for that advice!

--
John Corliss

 wrote:

I had a two year old 24" acer LCD monitor that had the problem. I ended up
replacing all of the caps in the monitor. Better than new now.

 John Corliss wrote:

http://h10025.www1.hp.com/ewfrf/wc/document?docname=c01301704&tmp_task=prodinfoCategory&lc=en&dlc=en&cc=us&lang=en&product=3658911  

Based on my experiences to date, with cheap soldering irons, you have
to go for more power. At least, to get the equivalent operating power
of a controlled temperature soldering station. I have an 80W in my
collection, and this would be my weapon of choice. Mine happens
to have come from the hardware store.

(Amazon.com product link shortened)

This is the one I've got. I've had no problems with burnout.
Mine still works, but I bought it years ago, same model.

http://www.canadiantire.ca/AST/browse/6/Tools/WeldingSoldering/Soldering/PRD~0586306P/Mastercraft%252B80W%252BSoldering%252BIron.jsp?locale=en

I use the 80W iron, for things that are difficult to remove. For
regular SMT work, I use a pair of irons, a 15W and 25W, just
to show I don't always "lean on the power". Small SMT parts
are a lot easier to deal with.

(I don't believe in "soldering guns". I used to own one and burned
it out. They're "not recommended". Period.)

The thing is, the capacitor leads will be soldered to copper planes.
Each plane acts as a heatsink, sucking all the heat from the joint,
and preventing proper melting point from being achieved. And those
are the conditions where damage arises - you try to pull the legs
out, tearing out the solder fillet, instead of getting a clean
removal. Or, you press so hard on the board, using the tip of the
soldering iron, that the copper pad is ripped up.

It is possible, when you lay out a board, to use an "isotherm" pad
pattern, which gives good enough electrical contact, without becoming
a giant heatsink. But that is not popular on boards.

A second thing that helps, is oversized holes for the capacitor leads.
That too, is not popular, but at least for a good reason. If you use
oversized holes, the capacitor legs need to be bent, to maintain
a compression fit. (I believe some pick and place machines can be
programmed to do the bending.) By using an "interference fit" for the
holes, barely larger than the lead diameter, the capacitor stays in the
board, and won't float out of the hole while riding on a wave solder
machine. But the interference fit design, makes maintenance unnecessarily
difficult.

I've tried both a vacuum desoldering station, also manual solder
sucker and solder wick, without much progress. It took plenty of
cursing and swearing, the last time I did some.

You can try this stuff if you want (I could never afford it).
Chipquik is a low temperature melting point solder, which you can use
to "poison" the solder joint. What that achieves, is a lower melting
point, and the ability to get the capacitor to move, without so much heat
buildup as to lift the foil off the motherboard. After the capacitor
and leads are removed from the hole, you use the solder sucker and/or
solder wick, to clean all the old solder off the board. When you
use new solder, the melting point will then return to the originally
intended temperature and metal composition.

http://www.chipquikinc.com/newsletters/cq_new_june_2004.htm

The alloy is absurdly expensive.

http://www.chipquikinc.com/store/prod_smd16.htm

When you get your soldering gear together, practice on some other busted
electronics first, to get a feel for how easy it is to damage
the foil. Modern motherboards don't take a lot of abuse, at
least compared to the motherboards my former employer used
to make. Those were bulletproof by comparison. You could leave
a 35w iron resting on one of those PCBs, and the foil would not lift.

For solder wick, to clean up the pad after the cap is removed,
I like the thinner stuff. With ROHS, there are more variations
on soldering materials, so there are more choices here to make.
I'd probably go for a few rolls of 80-1-10 (resin based). The
idea of the resin, is to enhance take-up of the solder. Resin
residue can be cleaned up with alcohol (isopropyl) later.

http://www.chemtronics.com/literature/americas/flyers/Soderwick%20Brochure_LR.pdf

You can see the Solder Wick at RadioShack, got a thumbs down from a few people
in the review section. There is probably no resin in this.

http://www.radioshack.com/product/index.jsp?productId=2062744

This is an example of a manual solder sucker, with spring
loaded pump. You push on the spring until it clicks, to
store spring energy. Everyone has their favorite model, and
this is the one I used to use. These all have teflon tips,
that can get chewed up after a while, so treat the tip
with respect to make it last longer. Teflon is used, to
withstand the high temperatures.

(Amazon.com product link shortened)

I see the people at the motherboard company, are comedians.
They've used a mix of Polymer and Electrolytic caps. The
electrolytics (with the pressure relief joints on the top)
are the ones that likely failed. And based on your description
that eight had failed, I'd bet that even the ones not under
electrical stress have failed. They probably failed the
same way the ones here failed - a pure internal chemistry
failure, that can happen even if the motherboard is stored
in a closet for a couple years. Caps with "bad chemistry" inside,
don't need to be under electrical stress, to fail.

http://h10025.www1.hp.com/ewfrf-JAVA/Doc/images/c00906142.jpg

Good luck with the repair. And keep track of how many swear
words were necessary, to complete the repair :-)

    Paul