Capacitor plague

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All these aluminum electrolytic capacitors have failed, with open vents in the top of the can, and visible dried electrolyte residue (reddish-brown color).

The capacitor plague was a problem with the higher than expected premature failure rate of aluminum electrolytic capacitors with non-solid or liquid electrolyte of certain brands, especially from some Taiwanese manufacturers.[1] The capacitors failed because of a special water-based corrosion effect, due to a poorly formulated electrolyte.

The first flawed capacitors were reported in September 2002. Many publicized press releases about the widespread problem with premature failures of Taiwanese electrolytic capacitors appeared. Most of the affected capacitors failed within the next five years. High failure rates occurred in various electronic equipment, particularly motherboards, video cards, compact fluorescent lamp ballasts, LCD monitors, and power supplies of personal computers. News of the failures (usually after a few years of use) forced many equipment manufacturers to repair the defects. As of 2013 the problem seems to have receded, with the last major surge of complaints being reported in 2010.

Prevalence[edit]

Results of fire on a printed circuit board, caused by leaked electrolyte which short-circuited conductors carrying power

Faulty capacitors have been discovered in electronic equipment at various times, but mainstream electronics journals began to report widespread defective capacitors from Taiwanese manufacturers in motherboards in October 2002.[1][2][3] Many well-known motherboard companies have unknowingly assembled and sold boards with faulty capacitors sourced from other manufacturers. Major vendors such as Dell, HP, and Apple Inc. were affected.[4] Circa 2005, Dell spent some US$420 million replacing motherboards outright and on the logistics of determining whether a system was in need of replacement.[5][6] HP reportedly purged its product line in 2004. The motherboards and power supplies in the Apple iMac G5 and some eMacs were also affected.[citation needed]

While the capacitor plague has affected large numbers of desktop computers, the problem is by no means limited to that category. Bad capacitors can also be found in external power supply adapters, network switches, audio equipment, flat panel displays, and a wide range of other devices. Bad capacitors can cause a simple failure to turn on, or a wide range of bizarre (often intermittent) behavior of afflicted electronic equipment.

Diagnosis[edit]

In failures of general electronics devices, bad capacitors are often found in the power supply circuitry. In failed computer systems, bad capacitors are often found in power supply units, but also on motherboards next to CPUs, and near GPUs.

Visual symptoms[edit]

Failed Jun Fu electrolytic capacitors (the dark brown residue on the casings is deteriorated glue, not leaked electrolyte).

Direct visual inspection is a common method of identifying capacitors which have failed because of bad electrolyte. Failed capacitors may show one or more of these visible symptoms:

  • Bulging or cracking of the vent on top of the capacitor.[3] (The "vent" is shaped by an impression stamped into the top of the can, forming 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 exploding.)
  • Capacitor casing sitting crooked on the circuit board, as the bottom rubber plug is pushed out.[3]
  • Electrolyte leaked onto the motherboard from the base of the capacitor or vented from the top, visible as crusty rust-like brown deposits.
  • Detached or missing capacitor casing. Sometimes when the vent does not open, a failed capacitor will literally explode, ejecting its contents violently and shooting the casing off the circuit board.

Sometimes, electrolytic capacitors fail without any visible changes in appearance of the external SMD or metal can package. Since the electrical characteristics of capacitors are the reason for their use, these parameters must be tested with instruments to definitively decide if the devices have failed.

Electrical symptoms[edit]

As an electrolytic capacitor ages, its capacitance usually decreases and its equivalent series resistance (ESR) usually increases. The capacitance may abnormally degrade to as low as 4% of the original value, as opposed to an expected 50% capacity degradation over the normal life span of the component. When this happens, the capacitors no longer adequately serve their purpose of filtering the direct current voltages on the motherboard, and a result of this failure is an increase in the ripple voltage that the capacitor is supposed to filter out. This results in a system instability. Capacitors with high ESR and low capacitance can make power supplies malfunction, sometimes causing further circuit damage. In computers, CPU core voltage or other system voltages may fluctuate or go out of range, possibly with an increase in CPU temperature as the core voltage rises.

Impact[edit]

Closeup of swollen electrolytic capacitor vent and dried electrolyte residue

The large number of failures of aluminum electrolytic capacitors with liquid electrolytes are based on millions of faulty capacitors produced in the years 1999 to 2007 by some (not all) Taiwanese manufacturers[7] whose products started failing prematurely after only a few months of operation. Many[which?] of the capacitors had a life span specification (load life) of 2000 hours at 105 °C. With a lower average internal temperature of 45 °C on a printed circuit board and a ripple current within the data sheet specifications, these capacitors should have a life expectancy of about 18 years of continuous operation; a failure after 1.5 to 2 years is very premature.

Many well-known equipment manufacturers such as Dell had to carry out recalls and reimburse repair costs because of these capacitors.[8] In addition to manufacturer recall programs, detailed repair instructions for self-help can be found on the Internet.[9][10]

Industrial espionage implicated[edit]

A major cause of the plague of faulty capacitors was industrial espionage in connection with the theft of an electrolyte formula.[11] A researcher is suspected of having taken the secret chemical composition of a new low-resistance, inexpensive, water-containing electrolyte when moving from Japan to Taiwan. The researcher subsequently tried to imitate this electrolyte formula in Taiwan, to undersell the pricing of the Japanese manufacturers. However, the secret formula had apparently been copied incompletely, and it lacked important proprietary ingredients which were essential to the long-term stability of the capacitors.[2][3] The bad formulation of electrolyte allowed the unimpeded formation of hydroxide and produced hydrogen gas.[12]

Failed capacitor images
Opened electrolytic capacitor with extracted foils partly unwound. Red color is typical for some water-based electrolyte chemistries. 
Unwound layers of a failed electrolytic capacitor; foils are glued together, typical construction with water-based electrolytes. No obvious damage (short circuit) is visible. 
Failed electrolytic capacitors with swollen can tops and expelled rubber seals, dates of manufacture "0106" and "0206" (June 2001 and June 2002) 
A blown capacitor (top center) only can be viewed as evidence of a "bad" one with wrong electrolyte, if it can be shown that the capacitor has failed "prematurely" 

See also[edit]

References[edit]

  1. ^ a b Sperling, Ed; Soderstrom, Thomas; Holzman, Carey (October 2002). "Got Juice?". EE Times. 
  2. ^ a b Chiu, Y.-T.; Moore, S. K. (February 2003). "Faults & Failures: Leaking capacitors muck up motherboards". IEEE Spectrum 40 (2): 16–17. doi:10.1109/MSPEC.2003.1176509. ISSN 0018-9235. 
  3. ^ a b c d Smith, P. (11 May 2003). "Motherboard Capacitor Problem Blows Up". Silicon Chip. Australia. Retrieved 2012-03-07. 
  4. ^ Singer, D. M. (11 November 2005). "PCs plagued by bad capacitors". CNET (Asia). 
  5. ^ Vance, A. (28 June 2010). "Suit over Faulty Computers Highlights Dell's Decline". The New York Times. Retrieved 2012-03-08. 
  6. ^ "Defekte PCs: Dells Gewinnmotor stottert" (in German). Pressetext Nachrichtenagentur. .
  7. ^ "Low-ESR Aluminum Electrolytic Failures Linked to Taiwanese Raw Material Problems". Passive Component Industry (Paumanok Publications). September–October 2002. Retrieved 2013-08-05. 
  8. ^ Suit Over Faulty Computers Highlights Dell’s Decline, The New York Times .
  9. ^ Capacitor Replacement Video Tutorial (HD) (video), Afro tech mods .
  10. ^ Repair and bad capacitor information, Capacitor Lab .
  11. ^ "How a stolen capacitor formula ended up costing Dell $300m". 
  12. ^ Hillman, C.; Helmold, N. (2004). "Identification of Missing or Insufficient Electrolyte Constituents in Failed Aluminum Electrolytic Capacitors" (pdf). CARTS 2004: 24th Annual Capacitor and Resistor Technology Symposium. DFR solutions. 

External links[edit]