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Illicit Leaky Capacitors Killing Motherboards
mcd7756 writes "The IEEE Spectrum magazine has an article about how capacitors made with a stolen formula for the electrolyte are leaking and causing motherboards to fail. Some computer manufacturers are admitting to the problem; others are hiding it."
http://slashdot.org/article.pl?sid=02/11/04/175121 0&mode=flat
This shows that quality comes at a cost. If you truly want to get good quality goods, don't expect to keep forcing the market to make cheaper and cheaper products.
Why would a company steal a formula such as this? so they ddn't have to pay as much for the 'real deal' and then henceforth could sell at a cheaper price and undercut others. When this happens quality suffers.
It has happened in many other industries and frank, I'm surprised it hasn't yet happened in something as stressed and pushed-cheaper as the motherboard and other componentry markets.
Rampant commercialism is causing problems like this
From the article:
"Zogbi cites tests by Japanese manufacturers that indicate the capacitor's lifetimes are half or less of the 4000 hours of continuous ripple current they are rated for."
4000 hours for the good capacitors? That's like 6 months of continuous usage. Surely shome mistake?
The batch of SunRay 1 terminals (first generation?) that Sun recalled due to a power supply problem have the faulty capacitors. They were the same brand of capacitors as some dual-CPU MSI motherboards we had that died.
At the time, I also wondered what other devices may have these faulty aluminium electrolytic capacitors, but it appears the answer is not many; probably due to their cost, they seem to be restricted to high frequency switched mode power supplies.
This is old news! (Sep. 2002) I submitted this to /. some time ago, but it was rejected...WTF?
Links to original (and informative) articles are Faulty capacitors and Passive Component Industry report.
In fairness most of the products affected carry a "Made in Tiawan" warning!
Didn't they mean to say that "Leaking Capacitors Muck up Fotherboards"?
Basically anything that uses a switching power supply or a switching voltage regulator is at risk IMO. That covers most consumer and commercial equipment other than stuff that's physically too small to have one of these caps, or that handles only audio/radio.
The issue with electrolytic capacitors is this:
All capacitors have what is called an equivelent series resistance, or ESR (great: now we have 2 TLAs that are overloaded in context: RMS and ESR... )
The ESR only matters when there is a current flow through the device - a static voltage does not create (much of ) a static current flow - that is rather the definition of a capacitor. So if you are putting a DC voltage across the device all is well.
However, if what you are putting across the device is NOT DC, but rather DC with an AC component on top of it, then there will be a current flow as the capacitor tries to hold the voltage constant (again, that's rather the point).
However, due to the ESR, some of that current will cause heating of the device (power = I*I*R).
In caps with the good electrolytic, nothing much happens. In caps with the bad electrolytic, the electrolytic breaks down into hydrogen and oxygen, as well as boiling into steam. Pressure builds, and eventually the cap leaks. Since the other stuff in the electrolytic is caustic, your PC board traces rot away.
Now, at low ripple currents, this does not happen very fast, and any cap will have a long lifespan. However, as you approach the limit of the cap, the heating becomes the dominant factor, and the cap will cook itself fairly quickly.
That's where that 4000 hours comes from - that is not the cap running with a few tens of milliamps of current ripple across it, that is the cap getting amperes of current rammed down its throat, and running very hot.
That's also why you use tantalum caps wherever possible - tant's don't have an electrolyte, they use a very spongy tantalum slug with lots of surface area. They don't have quite the capacitance per unit volume that electrolytics have, but they don't leak, either. (but they do blow up real good (sic) when you exceed their rated voltage!)
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