PCs Plagued by Bad Capacitors

Hawaiian Rules writes "CNET has a story detailing a new threat to Dell PCs, Apple iMacs and other computers with Intel boards. This has been documented on BadCaps.net for some time, but the article also discusses what to do if you suspect you've got a case of the bad caps."

Comments

Not the first time

[Racher]

I had this happen to an old Asus board I had a couple year ago. It was covered on /. before.

Slashdot - Taiwanese Capacitors Leaking, Exploding

Watch out for all the 'Geeks popping a cap in your mother' jokes.

-Eric

Re:it's not that hard to fix

[labnet]

This is where a little bit of knowledge can be a bad thing.

Sure its easy enough to go to the local electronics store, and buy an equivilent cap (ie match the Voltage and Capacitance written on the cap), but there are a couple of other very important (depending on the application) normally not marked parameters.
Ripple Rating, Temperature, and ESR
ESR = Effective Series Resistance and can cause stability problems if it is too high.
If the Ripple Current Rating is too low, you could end up with more exploding / dying caps due to over heating.
If you do decide to DIY, I suggest you buy 105oC, low ESR caps. (And don't forget they are polarised. Putting them in backwards will make them explode)

Stamped with an "X" on top ?

[aspeer]

The article says that the caps have "... a letter "X" stamped on the top." They are not stamped with the letter "X" - they are stamped to allow the caps to deform and vent the boiling liquid contents in a predictable manner when it fails. That is why the top of a failing cap bulges and not the sides.

Not that it always works - plenty of caps still just "pop" violently and spew their content across the electronics anyway.

So don't look for a stamped "X", chances are all your caps have them ..

Nothing to do with brand new high-tech

[HotNeedleOfInquiry]

The caps were made by Nichicon. Nichicon has been in business for 50 years and has had, up to now, the reputation of building *the best* low esr high quality electrolytic caps on the market. I've specified Nichicon caps only in designs because they work better than anything else.

That's why this is such a surprise.

I know it's bad form to bitch about moderation, but I can't see any way that the parent is insightful. Nichicon has produced good caps for years. Manufacturers pay a premium for Nichicon caps. Something or someone fucked up a Nichicon. Has nothing to do with trial and error.

Re:Nothin new here. Just like Car Makers.

[HotNeedleOfInquiry]

But that's not what happened. The capacitor company in question, Nichicon is, or rather was, the best in the business. Manufacturers pay a premium for Nichicon caps because they were the best available. The motherboards in question were made by Intel and Intel uses quality parts.

The problem is that Nichicon screwed up somehow, not that Intel got burned for buying the cheapest parts.

The real story is in IEEE Spectrum, April 2003

[Animats]

The capacitor story is covered properly, with manufacturer names and electrolyte formulas, in IEEE Spectrum for April, 2003. But you have to be an IEEE member to read it.

The definitive study, from The Computer Aided Life Cycle Engineering (CALCE) Electronic Products and Systems Center , is "Identification of Missing or Insufficient Electrolyte Constituents in Failed Aluminum Electrolytic Capacitors". CALCE actually took capacitors apart and analyzed the electrolyte.

To see if the excessive hydrogen was being produced by impurities in the capacitor foil, wavelength dispersive x-ray spectrographic (WDS) analyses of foils from a capacitor from the lot of Taiwanese capacitors known to bulge and foils from a capacitor from a lot of non-bulging Japanese capacitors were performed.

A small amount of magnesium was detected in both the Taiwanese and Japanese foils, and copper was detected in the Taiwanese foils alone (see Table 1). Ignoring the topical constituents of oxygen and carbon, the purity of the cathodic aluminum foil from the Japanese capacitor worked out to be approximately 99.1 wt%, which was within the limit set by Dapo. The purity of the cathodic aluminum foil from the Taiwanese capacitor was approximately 97.5%,which was below the minimum value stated by Dapo. The insufficient purity of the Taiwanese aluminum foil could cause gaseous hydrogen production that would not be impeded by a depolarizer, but the galvanic couples were not thought to be sufficient to account for the rapid production of hydrogen gas that was necessary to cause the relatively rapid bulging of the capacitor cans. There were other anomalies in the ion chromatographic analyses,chiefly variations in the amounts of ammonium and phosphate ions present. Ammonium ions in water form ammonium hydroxide, which is strongly basic. This raised concerns about the pH of the electrolyte in the bulging capacitors,as a review of the chemical properties of aluminum oxide - the dielectric - showed that it is slightly soluble in basic solutions (but not in acidic)[8 ]. Measuring the pH of electrolytes from capacitors from the Taiwanese lot known to bulge and from a Japanese lot that had not exhibited bulging showed that the electrolytes of the bulging lot were weakly basic (7 < pH < 8),while those of the non-bulging lot were acidic (pH 4).

And that's the cause - internal corrosion because the electrolyte has a highly acidic Ph.