Capacitor plague

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Leaking Chhsi capacitors on a MSI 694D Pro motherboard.

The Capacitor plague (also known as Bad Capacitors, Bad 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, and power supplies of personal computers.

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.

[edit] 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 appears to have suffered as well (see these photos). The problem has apparently been rectified on the updated model of the iMac released in May 2005. Apple has also introduced an extended free repair program for early iMac G5s suffering from the problem ^[1]. Some eMac computers were affected as well, and there is a similar repair extension program for it^[2].

A power supply unit with failed capacitors.

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 car 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, ^[3] 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.

[edit] Symptoms

Bulging or domed tops, no matter how slight, are a sure sign the capacitor is faulty.

Failed Choyo caps which have leaked onto the motherboard.

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
• 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

Failed Tayeh capacitors which have vented through their aluminum tops.

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
• Vcore 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 onboard 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

This failed cap has blown its can off.

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.

[edit] 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. ^[4] (An anti-corrosion ingredient was not documented, reported in comp.risks .) ^[5]

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 capacitors 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.

Sadly, once the problems with these capacitors became known, there is evidence that motherboard manufacturers continued to use the bad capacitors either knowingly or unknowingly. Only ABIT has admitted to the problems, while other manufacturers have given responses ranging from ignorance to denial. Some have gone so far as to issue legal threats to web sites mentioning their names in conjunction with capacitor failures.^{[citation needed]}IEEE's Spectrum covered the issue ^[4], and later estimated that the problem cost US$100 million to fix.^[6]

[edit] Replacement of failing capacitors

An MSI 694D Pro motherboard with all new Nichicon capacitors.

Some repair personnel are willing to perform the labor intensive task of replacing motherboard capacitors (typically referred to as "recapping"), however the cost of having a technician repair the board often costs more than simply purchasing a replacement board of equal or even greater value, depending on the country. Furthermore, recapping a motherboard does not guarantee its revival as neighboring components can be damaged by leaked electrolyte and can also be damaged by heat during the soldering process, especially if the person attempting the repair is unskilled.

Soldering on motherboards, which are typically made of six or more layers, some of which may have ground planes, and may use lead-free solder requiring higher temperatures than leaded solders, can be challenging. Attempting a repair without the right equipment and skills can easily destroy an otherwise repairable board. Before replacing the capacitors on a motherboard, research has to be done into the proper low-ESR replacements and best soldering methods for the board in question. During the repair process special care should be taken to protect the hands and eyes as capacitor fluid is acidic.

As is common with motherboards, it is usually more cost effective to purchase a replacement unit rather than to attempt the repair.

Typically, only electrolytic capacitors with rated values over 480 µF fail, since the smaller capacitances are usually implemented with a different electrolyte. When motherboards are recapped, only the larger capacitors may be replaced in order to save money.

Failing capacitors with smaller values are not unheard of, so replacing all capacitors may be advisable—particularly if the existing capacitors are from a questionable manufacturer.

[edit] Failure analysis

While failing capacitors typically results 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.

Capacitors removed from a computer power supply were found to have dramatically less capacitance than their rated values.

A capacitor rated 2200 µF may experience a drop in capacity to as little as 75 µF. The design engineer might have assumed that it might drop up to 50% over its life, 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 short circuit, 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. A motherboard with symptoms of failing capacitors should be taken out of service until it is repaired in order to prevent further damage.

[edit] References

1. ^ Apple iMac Repair Extension Program
2. ^ Apple eMac Repair Extension Program
3. ^ dead page
4. ^ ^{a b} Yu-Tzu Chiu; Moore, S.K. Leaking capacitors muck up motherboards, Spectrum, IEEE; Volume 40, Issue 2, Feb 2003 Page(s): 16 - 17.
5. ^ [1] name="May 2003comp.risks"
6. ^ Bogus! Electronic manufacturing and consumers confront a rising tide of counterfeit electronics; Spectrum, IEEE, May 2006

[edit] External links

• [2] - Carey Holzman is 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 and replacement capacitor selection
• Motherboard Capacitor Problem Blows Up — An article about capacitor failures