The ultra-low ESR Nichicon HM and HN series were decent parts. According to Nichicon, they had at least one production line which was overfilling the electrolyte in these two series. HM and HN series parts made after 2004 are perfectly fine (I continue to use NOS late production HM and HN parts as replacements for faulty Nippon / UCC KZG). The HZ series (HM->HN->HZ) seems to not have been affected at all.
This was never actually proven and that announcement didn't actually stem from Nichicon, it stemmed from a university in Iowa:
Recently Dell recently discovered potential problems with a capacitor on the system board of GX270 systems with medium and small form factor motherboards. The problem is isolated to a specific capacitor supplier which was used in system boards manufactured from April 2003 to March 2004. The defective Nichon capacitors were placed on two manufacturers' GX270 motherboards between 04/01/2003 to 03/20/2004.
However we have discovered that the Nichon capacitors were not all produced outside control specifications. Rather the affected capacitors were limited to certain batches made during specific shifts during the manufacturing process. This means that not all GX270 motherboards are affected. Unfortunately, there is not specific way to determine which motherboards are affected and which are not.
Specifically the capacitors were filled with more liquid than required. After an approximate service life of 300 days and when the CPU reaches a core temperature of 64 degrees C they will begin to bulge and eventually overflow onto the motherboard causing a system crash and a "No Post" failure on boot. There is usually no data loss associated with this issue.
Dell became aware of the problem in the last several weeks based on high numbers of customer tech support calls related to the GX270 motherboard failures. Because of the extremely long time lag between system install and the beginning of the failure rate spike it was impossible to anticipate the problem we now face. In response to our engineering research regarding the suspect capacitors and motherboards, we have decided to proactively replace GX-270 motherboards at specific customer locations.
The GX270 motherboards have not been made in the past year and our on hand reserves required for normal fix on fail warranty repairs have been strained. We have arranged for these motherboards to be remanufactured however that process takes time to ramp up. Delivery of sufficient numbers of boards to move forward with proactive field replacement is not anticipated for some weeks.
I think they were of the assumption that they were "overfilled" because they were leaking an overabundance of electrolyte. Nichicon never actually commented on the defective HMs and HNs. Any announcement (at least that I could find on the Internet) that the problem would be "fixed" came from Dell.
Further intelligence revealed that Kamei/Jamicon sources its electrolytes from Sanyo in Japan, and likely was not affected by the faulty electrolyte supply.
Nope. The follow up article to that issue shows Sanyo denying that they supply Jamicon with electrolyte:
http://old.passivecomponentmagazine.com/files/archives/2002/PCI_02_06Nov-Dec.pdfI'm sure many of those bad bands, IE Teapo, Lelon, OST, G-Luxon, and Jamicon, were lying so as to protect themselves. It's very unlikely they pay the higher premium for importing higher purity materials from Japan - they can't even be bothered to QC test their products.
Proadlizer caps are notoriously bad for failures. Actually their performance is superb, but they killed too many laptops, eapecially Toshiba ones.
Yup, those are terrible. The Proadlizer capacitor (of a tantalum polymer class) was manufactured by Chemi-con and NEC as a joint effort. I don't know what exactly went amiss during the manufacturing process. Maybe the polymerization process was ineffective, IE residue could have been left over on any of the layers of functional polymer on the cathode (possibly using polypyrrole), creating a leakage path which grew over time (especially with high heat and humidity) and resulting in all those failures. Just a theory of course...
The forming process is also important. Cheap brands could speed up the forming process to reduce costs, i.e. thinner oxide layer.
Cheaper brands use very bad materials and faulty electrolyte, so faulty that such capacitors could actually bulge in a sealed bag (as shown in this thread with those CapXon LZ capacitors), in a cool and dry environment, retaining their full leads, without ever having been soldered to a board, or without having bias applied to the plates or conducting current (although heat can certainly expedite such chemical reactions). Really bad brands use shoddy quality aluminum foil (with purity below 98%, the minimum specified by DAPO), which contains an excess of copper, zinc, magnesium, and iron, and that can certainly cause hydrogen gas to form at the cathode.
Seems like Lelon is not a shabby brand.
YXA series has been discontinued in 2012, so either the ones used are NOS or fake parts. Anyway, YXA are low end parts, direct equivalent of Lelon RGA.
Rubycon YXA are good, general purpose capacitors (although PX has indeed replaced them for some time). You just need to use them properly, IE within specifications. Lelon has always been a terrible brand - one of the primary brands associated with the so-called "capacitor plague".
A badly laid out PSU full of NCCs running very hot is probably going to die before a well-cooled one full of CapXons.
No, not really, unless you're referencing KZGs and KZJs (those are also known to bulge in storage).
But CapXon is a terrible brand. No brand has a higher failure rate in LCD monitors.
Exactly, but it's not sufficient anyway. Many crap capacitors performed accelerated tests just fine. But when they reached the real world, turned out they fail prematurely. For example Nippon Chemi-con KZG series or Nichicon HM, HN series if talking about good brands. I have read a while ago that high voltage and temperature used in accelerated tests prevented some negative effects which caused capacitors to fail in real use conditions.
The higher voltage generates the dielectric film on the anode faster and keeps it thicker, which prolongs the thinning of the dielectric, IE the H2O base electrolyte's tendency to attack the aluminum oxide layer, convert the aluminum into hydroxide, and outgassing thereafter. The problem with cheap brands is that the water-base electrolyte that they use does not contain the proper hydrogen absorbers, corrosion inhibitors, depolarizers, and conductivity enhancers to stabilize the oxide film and suppress the aggressiveness of that type of electrolyte. That type of electrolyte needs very pure materials, good manufacturing (effective QC testing), and excellent additives to remain stable. So it's not IF but WHEN those bad capacitors fail. Of course, there is more to it than that - it's critical that the electrolyte has a chemical composition that isn't bound to wreak havoc upon the rest of the materials. pH values are also vital, because too high a pH value (higher than 7) and the electrolyte becomes basic rather than acidic, which means they are more chemically prone to instability.
But without question, QC testing is the most important factor of all, and that's what most cheap Taiwanese and Chinese brands miss, and that is the reason for their inconsistency and unpredictable performance in the real world. The Japanese brands process all their own materials (which are always of high purity and quality) and perform extensive QC testing on all (if not most, possibly evidenced by the defective KZG, KZJ, HM, and HN series, unless they were counterfeit) of their capacitors. Most cheap brands don't bother with QC testing at all, so whatever defects that are present in their products won't actually show up until some time after they're manufactured, IE when they reach the consumer and when it is no longer those companies' problem.
As for the Lelons that survived reverse voltage? It would make sense if they were bi-polar electrolytics by any chance. OR, if Lelon made a mistake and sleeved those capacitors with the polarity stripe the wrong way around from the factory (more likely the latter). Or possibly because they were installed on a negative output. No electrolytic that isn't bi-polar can survive reverse polarity for long, not even the highest quality electrolytic of sorts (unless they're semi-polar). Reverse polarizing capacitors exceeds the reverse bias (cathode) voltage, which usually isn't higher than 1.5V. And just to be clear, all wet electrolytic capacitors have some sort of wear out mechanism. The liquid electrolyte is prone to giving away and drying up over time, whether through rubber seal diffusion or through the self-healing mechanism. But there is certainly a difference between the top tier brands and the lesser quality ones.
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