hi
please read
why chineses-taiwan- make capacitors fail far sooner than other ones.
http://en.wikipedia.org/wiki/Capacitor_plague
The capacitor plague (also known as bad capacitors) is the common premature failure of huge numbers of electrolytic capacitors of certain brands made from about 1999 and sometimes until 2007, used in various electronics equipment, particularly motherboards, video cards, compact fluorescent lamp ballasts, LCD monitors, and power supplies of personal computers. The first flawed capacitors were seen in 1999, but most of the affected capacitors were made in the early to mid 2000s. News of the failures (usually after a few years of use) forced most manufacturers to repair the defects and stop using the capacitors, but some bad capacitors were still being sold or used in equipment as of early 2007[update], and faults were still being reported as of 2010[update].[citation needed]
An incorrect electrolyte formula within a faulty capacitor causes the production of hydrogen gas (confirmed by mass spectrometry[1]),
leading to bulging or deformation of the capacitor's case, and eventual venting of the electrolyte. The failed capacitors analyzed by two University of Maryland researchers (by ion chromatography and mass spectroscopy) contained no traces of the depolarizing agent normally found in such capacitors in order to retain the hydrogen.
The root cause of failure for bulging Taiwanese capacitors has been hypothesized to be dissolution of the aluminum into the electrolyte due to poor phosphate-electrolyte balance, rather than the normal evaporation of the electrolyte that all such capacitors undergo. This hypothesis has been confirmed by analyzing the electrolyte using energy dispersive X-ray spectroscopy (EDS),
which confirmed the presence of dissolved aluminum in the Taiwanese capacitors' electrolyte, but not in Japanese ones, and by electrical testing, which confirmed a thinning of the dielectric, because the capacitance increased before failure, rather than the normal decrease through electrolyte evaporation. The industry standard test failed to capture this behavior, likely because the high voltage used in the test significantly retards the dissolution, whereas it occurs faster at the production environment voltages.[1] taiwan is china basically.
In rare cases,
faulty capacitors have even been reported to pop or explode forcefully. Although modern manufacturing techniques normally ensure they vent safely rather than explode, manufacturers[who?] have been known[by whom?] to omit the key safety features that allow this.[citation needed]
A serious quality control problem is that the problem only manifests after use over a period of time;
poor quality electrolytic capacitors have the same measurable parameters as good ones when new. Only extensive accelerated life testing with high ripple currents and high operating temperatures can identify inferior components. After some normal use the bad capacitors fail predictably far sooner than normal end-of-life; most electronic components do not systematically fail in this way.
Carey Holzman claims to be the first journalist to bring this issue to the public's attention and has worked with lawyers to bring settlements from major manufacturers.[2]
please read
http://spectrum.ieee.org/computing/hardware/leaking-capacitors-muck-up-motherboards
Leaking Capacitors Muck up Motherboards
Finger-pointing and fury as manufacturers try to dodge blame
By Samuel K. Moore, Yu-Tzu Chiu (Taipei) / February 2003
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Photo: Nicholas Eveleigh
Busted caps: capacitors oozing a brownish crud as on this motherboard, provided by custom computer builder Carey Holzman, have led to the failure of hundreds of PCs. A faulty electrolyte formula is to blame. It has all the elements of a good thriller: a stolen secret formula, bungled corporate espionage, untraceable goods, and lone wolves saving the little guy from the misdeeds of multinational corporations. In this case, a mistake in the stolen formulation of the electrolyte in a capacitor has wrecked hundreds of PCs and may wreck still more in what is an industrywide problem.
Aluminum electrolytic capacitors with a low equivalent series resistance (ESR) are high-capacitance components that generally serve to smooth out the power supply to chips. Throughout 2002, they have been breaking open and failing in certain desktop PCs. Motherboard and PC makers contacted by IEEE Spectrum have stopped using the faulty parts, but because the parts can fail over a period of several months, more such failures are expected.
So far, the only motherboard maker to admit to the problem is ABIT Computer Corp. (Taipei), and the only major PC maker to acknowledge being affected is IBM Corp. But the problem is likely to be more widespread. Indeed, those who have repaired the damaged boards say that they have encountered crippled motherboards from Micro-Star International, ASUSTek Computer, Gigabyte Technology, and others.
For Gary Headlee, who repairs electronics in Midvale, Utah, the trouble surfaced at the end of 2001, when users of PCs with ABIT motherboards began to complain of leaking capacitors. Headlee's solution was to replace all the low-ESR aluminum electrolytic capacitors of 1000 microfarads or over. By last summer he was receiving as many as 10 broken boards through the mail every day, and he estimates he has fixed 1200 boards so far. At about the same time, Carey Holzman, who builds and sells custom PCs, noticed the identical problem in non-ABIT computers he had sold and others he was asked to repair [see ]. In 12 years of PC repair, "I've never seen anything like it," says Holzman, owner of Computer Performance Specialists (Glendale, Ariz.).
It is clear now that a faulty electrolyte is to blame for the burst capacitors. The mystery is: where did it come from and which manufacturers used it? Citing Japanese sources, initial reports claimed that major Taiwanese capacitor firms, including the island's market leaders, Lelon Electronics Corp. and Luxon Electronics Corp., had turned out faulty products. But both companies have denied the accusations.
Most of the leaking capacitors pulled from bad boards in the United States, according to repair people, were labeled Tayeh, not a brand affiliated with known capacitor makers. Many others were unmarked.
Some, however, did bear the trademarks of Taiwanese passive components firms such as Jackcon Capacitor Electronics Co. (Taipei). Jackcon claims that it has been out of the motherboard market for two years but received some complaints from U.S. consumers in 2002. John Ko, its managing director, blames the motherboard design and remains confident in the quality of Jackcon products. According to Ko, the company's low-ESR capacitors passed quality tests at the Industrial Technology Research Institute (Hsinchu, Taiwan), a nonprofit R&D organization partly funded by the Ministry of Economic Affairs (Taipei), which is also often the source of Taiwanese firms' electrolyte formulas.
What happened? The origins of the motherboard malaise seem a lesson in how not to commit corporate espionage.
A well-placed source in Taiwan, who did not wish to be identified, largely confirmed for Spectrum accounts published in the United States that were based on sources in the Japanese electronics industry. According to the source, a scientist stole the formula for an electrolyte from his employer in Japan and began using it himself at the Chinese branch of a Taiwanese electrolyte manufacturer. He or his colleagues then sold the formula to an electrolyte maker in Taiwan, which began producing it for Taiwanese and possibly other capacitor firms. Unfortunately, the formula as sold was incomplete.
PHOTO: CAREY HOLZMAN
Exploding capacitors blow the lid off a case of intellectual property theft in the electronics industry
"It didn't have the right additives," says Dennis Zogbi, publisher of Passive Component Industry magazine (Cary, N.C.), which broke the story last fall.
According to Zogbi's sources, the capacitors made from the formula become unstable when charged, generating hydrogen gas, bursting, and letting the electrolyte leak onto the circuit board. 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.
Electronics makers are ordinarily very careful about capacitor quality. "The large volumes of passive content in any electronic device means that you have that many more chances for a product to fail," says Zogbi, who also runs The Paumanok Group (Cary, N.C.), a market analysis firm focused on the passive components industry. Electronics firms generally supply their manufacturers with a list of parts and materials they can use from suppliers whose quality they trust. Zogbi suspects that, in an effort to cut costs, contract manufacturers used dodgy component sources that were not on the approved list.
Major Taiwanese capacitor makers have vigorously denied having made any bad components, but the crisis has had a chilling effect on the island's whole industry, which produces 30 percent of the world's aluminum electrolytic capacitors.
