Slashdot Mirror
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
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.
However, I'm glad that this is happening to boards that end up in the hands of tech-savvy individuals that can spot the problem. People who buy ABIT, Asus, etc... boards expect a lot from the product that they recieve and are usuially knowledgeable about the equipment that they run.
I could only imagine if this happened to a major computer company, how it would be swept under the rug (which it may already have been). I see that IBM is named in the article, so at least they are willing to accept the failures. IBM is one of the only computer makers that I trust anymore after the way that they handled their hard drive failure issues. Yes, they tried to fix the problem by changing the uptime specs, but in the end, they got the problem worked out without too much hassle to customers (hardware zealots excluded).
I would like to know if this problem has been documented by any users that aren't using products from the manufacturers listed in the article and their expierence with the equipment, service and support.
I don't keep a lid on my coffee so when I walk around I look busy -me
High-Reliability motherboards don't use electrolytic capacitors for their onboard power supplies anyway. You'll only find these types on the typical built like crap (found in the majority of PC's built today)high volume motherboards. 5000 hour lifetime is what you'll find for typical ratings on low esr and long life electrolytic capacitors. This is only 200 days of continuous use.
High-Rel designs use very low esr tantalum caps. like these T530 Series
Quidquid latine dictum sit altum viditur
What's really odd is that bulging and popping electrolytic capacitors usually are caused by applying the wrong polarity to them.
When the capacitor is made, a DC current is put through them to form a crust on the metal surfaces inside the capacitor, which is then used as the dielectric.
When the capacitor is used in a product, you have to apply the same polarity to it, or you'll reverse the chemical reaction and get a DC current flow, which boils the electrolyte. (Thus causing pressure inside, causing a bulge and eventually a pop.)
What's this Submit thingy do?
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!)
www.eFax.com are spammers