The capacitor plague (also known as bulging capacitors, bad capacitors, bad caps, swollen caps or bloated capacitors) involved the common premature failure of certain brands of electrolytic capacitors used in various electronics equipment, and particularly in motherboards, video cards, compact fluorescent lamp ballasts, 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, and while news of their failures (usually after a few years of use) has forced most manufacturers to fix the defects, some bad capacitors are still being sold or integrated into designs in early 2007 [1]. An incorrect electrolyte formula within a faulty capacitor causes the production of hydrogen gas, leading to bulging or deformation of the capacitor's case, and eventual venting of the electrolyte. In rare cases, faulty capacitors have even been reported to pop or explode forcefully.
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Incidence
Faulty capacitors have been discovered in motherboards as old as Socket 7 and have affected boards manufactured up to the present day. The motherboard companies assembled and sold boards with faulty caps sourced from other manufacturers (see below). This is also not a phenomenon that is specific to PC based equipment; the first release of the iMac G5[2] and some eMac computers[3] were also affected.
While capacitor plague largely affects desktop computer hardware, this problem is by no means limited to that area. These capacitors can also be found in some cameras, network switches, audio equipment, DVD players, and a range of other devices. Even some automobile electronic control units have been found to have these same brands of often-failing capacitors. However, computer components are by far the most common location of these capacitors. The fact that these failure-prone capacitors are still being used has angered many people, especially in cases where a motherboard populated mainly with high quality capacitors has one or two of the bad capacitors on it, leading to accusations of planned obsolescence on the part of motherboard manufacturers. Indeed, a strong case can be made that these capacitors (which often fail in 6 months or less) are still being manufactured, and are still being chosen over superior components by manufacturers to use in their products. As of May 2005, [4] some evidence shows that the failing Nichicon capacitors on the iMac, Intel, and Dell boards are due to a different problem (capacitors overfilled with electrolyte) than the one discussed on this page (faulty electrolyte formula). However, both the effects on the system and the physical appearance of the capacitors are the same as the other failing capacitors, as is how to identify them, and the required repair. (This affects the HM and HN Series capacitors only.)
Symptoms
The most common method of identifying capacitors which have failed because of bad electrolyte is visual inspection. Such a capacitor will show one or more of these symptoms:
- Bulging of the vent on the top of the capacitor. (The 'vent' is the impression stamped in the top of the can. The impression forms the seams of the vent. It is designed so that if the capacitor becomes pressurized it will split at the vent's seams relieving the pressure rather than making it explode.)
- In the case of Dell Optiplex GX270s often a "Thermal Event" is displayed in white on a black screen when rebooting. [5]
- Sitting crooked on the circuit board as the bottom rubber plug is pushed out
- Electrolyte (a crusty brown substance) leaked onto the motherboard from the base of the capacitor
- Venting from the top of the capacitor, visible as rust-like brown deposits, or a visible hole in the vent.
Note: the electrolyte is usually wet, not dry. Be careful not to confuse electrolyte leakage with the petroleum-based glue (e.g. Evo-Stik) that is sometimes used to secure the capacitors to the board. This glue is a sandy yellow colour but turns darker (towards black) with heat. A dark brown crust up the side of a capacitor is invariably glue, not electrolyte. A common effect is corrosion of component leads covered by the glue, leading to leakage current or open-circuit. The presence of black glue is a sure sign that the capacitor has overheated due either to internal failure or inadequate ventilation.
As the capacitor ages, its capacitance decreases while its equivalent series resistance (ESR) increases. When this happens, the capacitors no longer adequately serve their purpose of filtering the direct current voltages on the motherboard, and system instability results. Some common symptoms are:
- Not turning on all the time; having to hit reset or try turning the computer on again
- Instabilities (hangs, BSODs, kernel panics, etc.), especially when symptoms get progressively more frequent over time
- CPU core voltage or other system voltages fluctuating or going out of range, possibly with an increase in CPU temperature as the core voltage rises
- Memory errors, especially ones that get more frequent with time
- Spontaneous reboots
- In case of on-board video cards, unstable image in some video modes
- Failing to complete the POST, or rebooting before it is completed
- Never starting the POST; fans spin but the system appears dead
Unlike the physical signs which are conclusive evidence the capacitors are failing, many of the operational signs may be caused by other factors, such as a failing power supply, dust clogging a fan, bad RAM, or other hardware problems. Instability, once the operating system has loaded, may indicate a software problem (such as some types of malware, poorly-written device drivers or software), and not a hardware problem at all. If any of these symptoms are experienced, removing the system's case and inspecting the capacitors, especially those around the CPU, may immediately identify capacitors as the cause. If there are no physical signs, an oscilloscope may be used to examine the voltage on the capacitors, with excessive ripple voltage being a sign the capacitors are not doing their job.
Cause of the failing capacitors
In some cases, the root cause of the failing capacitors is industrial espionage gone wrong. Several Taiwanese electrolyte manufacturers began using a stolen formula that was incomplete, and lacked ingredients needed to produce a stable capacitor. [6] (An anti-corrosion ingredient was not documented, reported in comp.risks.[7]) When a faulty capacitor is charged, the water-based electrolyte becomes unstable, and breaks down producing hydrogen gas. Since these types of capacitors are sealed in an aluminum casing, the pressure builds up within the capacitor until either the flat metal tops of the capacitor begins to bend, or the rubber sealing plug is pushed down. Eventually the pressure exceeds the strength of the metal casing and venting occurs, either by blowing out the rubber bottom of the capacitor, or bursting the scored metal vent on the top of the capacitor. When an electrolytic capacitor bursts, effects can range from a pop and a hissing noise to a small explosion. Venting is typically messy, and the acidic electrolyte must be cleaned off the motherboard to prevent further damage. IEEE Spectrum covered the issue [6], and later estimated that the problem cost US$100 million to fix.[8]
Failure analysis
While failing capacitors typically result in the aforementioned system instabilities, occasionally, failed capacitors will lead to a failure of the voltage regulators on the motherboard. There are two common theories on why this happens. The first (and simpler) theory is that the failing capacitors develop a very high leakage current, overloading the voltage regulators and causing them to overheat. The second theory is that as the capacitance decreases and the ESR increases, the buck controller for the voltage regulator increases the switching frequency to compensate for the load. Since most of the MOSFET's heat output is produced during the switching transitions, the increased frequency causes them to overheat.
A capacitor rated 2200 µF may experience a drop in capacity to as little as 75 µF. A 50% drop over its life maybe to be expected, but not to 5% of its original value. The stability of the buck switching regulator is compromised by such a dramatic drop and the regulator's voltage oscillates (perhaps wildly) to voltages above the absolute maximum ratings of the ICs to which the supply is connected. The most common failure mode of the voltage regulator is for the MOSFET to fail in a way that produces a direct connection between the source and drain, causing the system's power supply (5 or 12 volts depending on the motherboard) to be applied directly to the CPU, northbridge, RAM, or other components. This, in turn, causes those parts to catastrophically fail. Note that measurement of the capacitance value is not a reliable guide to the condition of the capacitor. A capacitor that measures only fractionally low (within tolerance) may have an extremely high ESR (Ohms instead of MilliOhms). If the capacitance value is OK, always take an ESR measurement.
References
- ^ Badcaps.net - Badcaps Home. 070405 badcaps.net
- ^ Apple iMac Repair Extension Program
- ^ Apple eMac Repair Extension Program
- ^
dead page - ^ http://news.com.com/PCs+plagued+by+bad+capacitors/2100-1041_3-5942647.html
- ^ a b Chiu, Yu-Tzu; S.K. Moore (February 2003). "Leaking capacitors muck up motherboards" (PDF, subscription required). IEEE Spectrum 40 (2): 16–17. doi:10.1109/MSPEC.2003.1176509. ISSN 0018-9235.
- ^ May 2003 comp.risks
- ^ Pecht, Michael; Sanjay Tiku (May 2006). "Bogus! Electronic manufacturing and consumers confront a rising tide of counterfeit electronics". IEEE Spectrum 43 (5): 37-46. doi:10.1109/MSPEC.2006.1628506. ISSN 0018-9235.
See also
External links
- [1] - 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.
- BadCaps — A repair site offering tutorials on proper soldering, repair services and replacement capacitors
- Capacitor Lab - Repair and bad capacitor information site
- Motherboard Capacitor Problem Blows Up — An article about capacitor failures
- Identification of Missing or Insufficient Electrolyte Constituents in Failed Aluminum Electrolytic Capacitors; Hilman and Helmold, CARTS 2004
