Hacker News Reader

Comment by ahoka | Hacker News Reader

https://en.wikipedia.org/wiki/Capacitor_plague

A story of industrial espionage, betrayal and an incomplete electrolyte formula.

'Industrial espionage was implicated in the capacitor plague, in connection with the theft of an electrolyte formula. A materials scientist working for Rubycon in Japan left the company, taking the secret water-based electrolyte formula for Rubycon's ZA and ZL series capacitors[citation needed], and began working for a Chinese company. The scientist then developed a copy of this electrolyte[citation needed]. Then, some staff members who defected from the Chinese company copied an incomplete version of the formula[citation needed] and began to market it to many of the aluminium electrolytic manufacturers in Taiwan, undercutting the prices of the Japanese manufacturers.[1][42] This incomplete electrolyte lacked important proprietary ingredients which were essential to the long-term stability of the capacitors[4][23] and was unstable when packaged in a finished aluminum capacitor. This faulty electrolyte allowed the unimpeded formation of hydroxide and produced hydrogen gas.[36]'

Huh, I did not know this was the reason behind it.

I'm nominally in the electronics industry this was a big deal in part because Chinese companies were also feeding counterfeit parts into the supply chain.

There's a site to go with it too:

http://www.badcaps.net/

It's more of a general repair forums with lots of useful advice now, but there are still plenty of stories about how replacing a few dollars worth of caps saved some $$$ equipment from the e-waste.

This page doesn't talk about it, but what I recall is that the stage was set for this by a move away from a fire retardant (containing bromine) that was linked to developmental disorders. To eliminate the fire retardant, they also moved to a new capacitor chemistry.

That would represent a pretty big spike in demand from manufacturers. New product, possibly new partnerships.

That would be interesting because it would represent a second case of a safety oriented change causing a significant reduction in product quality in as many years. The other being the switch to RoHS lead free solder that caused a great many BGA failures for companies like nVidia.

The failure in implementing lead-free strategies is really interesting, because the sole reason lead was put into electronics solder was that it prevented the tin whisker growth pure tin solder or silver solder experienced.

So some odd-seventy-eighty years later people remove the lead and substitute it with "straight nothin'" and are subsequently surprised they get tin whiskers again?! WTF?

I thought it also made the solder slightly more malleable, so a flex in the board would be less likely to crack the joint. I understand that the nVidia problems were due to using such a large BGA that the thermal expansion of the chip was enough to crack the lead-free soldier after a number of cycles. With the old leaded solder you could get away with it, but the new stuff wasn't properly lifecycle tested before being integrated into the production lines.

Lead is added to solder because it lowers the melting point. It forms a eutectic alloy.

Tin whiskers has nothing to do with it.

>Tin whiskers has nothing to do with it.

This is not accurate. Tin whiskers are a well-known problem resulting from pure tin coatings (although the mechanism is not well understood) and lead has historically been added to mitigate their growth (among other benefits).

From Wikipedia:

"Traditionally, lead was added to slow down whisker growth in tin-based solders." [0]

From NASA:

"No single mitigation technique provides effective protection against whisker formation except the addition of 3% or more of Pb by weight" [1]

"Suggestions for Reducing Risk of Tin Whisker Induced Failures...1. Avoid the use of PURE TIN plated components if possible...Alloys of tin and lead are generally considered to be acceptable where the alloy contains a minimum of 3% lead by weight...Although some experimenters have reported whisker growth from tin-lead alloys, such whiskers have also been reported to be dramatically smaller than those from pure tin plated surfaces and are believed to sufficiently small so as not to pose a significant risk for the geometries of today's microelectronics." [2]

[0] https://en.wikipedia.org/wiki/Whisker_(metallurgy)

[1] https://nepp.nasa.gov/whisker/reference/tech_papers/2011-kos...

[2] https://nepp.nasa.gov/whisker/background/index.htm

> Lead is added to solder because it lowers the melting point. It forms a eutectic alloy.

Pure tin already has a melting point of 230 °C. Yes, Sn63Pb37 (arguably the best solder alloy ever created) has a somewhat lower melting point at around 180 °C but no one uses such low temperatures except when absolutely necessary.

Being able to make the alloy eutectic is yet-another advantage, but the main concern was clearly tin whiskers, because these were breaking devices in the field.

I find that interesting since Bromine is so often used as a sanitizing agent in indoor pools and hot tubs. I see that it causes central nervous system issues and I'm left wondering why Bromine in a steamy hot tub is somehow acceptable while its use in a tiny capacitor is somehow harmful.

Reply on news.ycombinator.com