Re: HM HN, Dates for the bad boys?
When electrolytic capacitors sit in storage, their oxide layer (thins) wears away. Electrolytic capacitors have the ability to correct any defects in the oxide layer (restore it). Reforming is a method to do that (slowly raising the applied voltage whilst limiting the current).
No, Panasonic capacitors were not part of the capacitor plague. At least not really.
The capacitor plague can broken into several issues:
1) A supposedly stolen, incomplete and faulty H2O base electrolyte without the right additives and oxidizers to prevent the metallic aluminum from becoming aluminum hydroxide, accompanied by rapid generation of hydrogen gas and excessive vapor pressure. Many Taiwanese brands were accused of this in the early 2000s as those were the brands suddenly dropping like mayflies on motherboards less than a year old.
2) Aluminum foil of low purity mined in China and Taiwan. This issue may still exist to this day with certain brands, where the impurities in the aluminum foil, such as too much copper and zinc, can galvanically react with the ions in the solution to produce hydrogen gas.
3) Capacitors with a poor pH balance. This is an issue because aluminum will readily dissolve into alkaline solutions (pH values that are too high). Using phosphorous compounds in the electrolyte to protect the oxide layer from dissolution into the electrolyte and using capacitors that are acidic in nature rather than basic (lower, more chemically stable pH values) will solve that issue.
A study was conducted in 2004 which found that failed samples from Taiwanese brands of capacitors had dissolved aluminum in the electrolyte.
4) The huge faulty batch of Nichicon HM and HN capacitors, made from 2001-2005 (HM) and 2002-2005 (HN). No overall reason was ever proven, acknowledged, or admitted for all those premature failures (at least not that I can find), but around 2006, whatever issues those series had diminished. Chemi-con is also known to have issues with their KZG series and any series of wet electrolytics from them that are even lower in terms of ESR and higher in terms of ripple current rating. The electrolyte has a poor chemical composition and eventually breaks down, even in storage.
5) (This relates to issue #3) Really old stock of Japanese capacitors from the 1980s-early 1990s which are known to have leakage issues (from the bottom) due to the use of quaternary ammonium salt compounds. The pH balance grows unstable over time, causing the electrolyte to turn into a strong alkali which deteriorates the rubber seal enough to cause leakage. Using amidine based solutions seems to have rectified that issue. Nichicon (PF, PR, PL, PQ, RZ, RT, VZ, etc), Chemi-con (LXF, SXE, TXF, SXF, etc), and even Rubycon (YXB and SSP), Elna (RSG, RSE, etc), and Panasonic (possibly HFQ) all had some series which exhibited this issue.
When electrolytic capacitors sit in storage, their oxide layer (thins) wears away. Electrolytic capacitors have the ability to correct any defects in the oxide layer (restore it). Reforming is a method to do that (slowly raising the applied voltage whilst limiting the current).
No, Panasonic capacitors were not part of the capacitor plague. At least not really.
The capacitor plague can broken into several issues:
1) A supposedly stolen, incomplete and faulty H2O base electrolyte without the right additives and oxidizers to prevent the metallic aluminum from becoming aluminum hydroxide, accompanied by rapid generation of hydrogen gas and excessive vapor pressure. Many Taiwanese brands were accused of this in the early 2000s as those were the brands suddenly dropping like mayflies on motherboards less than a year old.
2) Aluminum foil of low purity mined in China and Taiwan. This issue may still exist to this day with certain brands, where the impurities in the aluminum foil, such as too much copper and zinc, can galvanically react with the ions in the solution to produce hydrogen gas.
3) Capacitors with a poor pH balance. This is an issue because aluminum will readily dissolve into alkaline solutions (pH values that are too high). Using phosphorous compounds in the electrolyte to protect the oxide layer from dissolution into the electrolyte and using capacitors that are acidic in nature rather than basic (lower, more chemically stable pH values) will solve that issue.
A study was conducted in 2004 which found that failed samples from Taiwanese brands of capacitors had dissolved aluminum in the electrolyte.
4) The huge faulty batch of Nichicon HM and HN capacitors, made from 2001-2005 (HM) and 2002-2005 (HN). No overall reason was ever proven, acknowledged, or admitted for all those premature failures (at least not that I can find), but around 2006, whatever issues those series had diminished. Chemi-con is also known to have issues with their KZG series and any series of wet electrolytics from them that are even lower in terms of ESR and higher in terms of ripple current rating. The electrolyte has a poor chemical composition and eventually breaks down, even in storage.
5) (This relates to issue #3) Really old stock of Japanese capacitors from the 1980s-early 1990s which are known to have leakage issues (from the bottom) due to the use of quaternary ammonium salt compounds. The pH balance grows unstable over time, causing the electrolyte to turn into a strong alkali which deteriorates the rubber seal enough to cause leakage. Using amidine based solutions seems to have rectified that issue. Nichicon (PF, PR, PL, PQ, RZ, RT, VZ, etc), Chemi-con (LXF, SXE, TXF, SXF, etc), and even Rubycon (YXB and SSP), Elna (RSG, RSE, etc), and Panasonic (possibly HFQ) all had some series which exhibited this issue.
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