I'm almost certain that you are wrong.
The "bad capacitor" problem was a real issue in the industry:
https://en.wikipedia.org/wiki/Capacitor_plague
The major brands were not affected.
And who discovered the problem? And ex-scientists form Rubycon.
http://www.molalla.net/members/leeper/alumin~1.pdfIt is somewhat ironic when you link this thread with the last sentence of the PDF article above:
Teapo suspects it is an attempt by Japanese aluminum capacitor suppliers to gain market share, and that the unfortunate incident involving a few companies will unfairly categorize the entire aluminum capacitor industry in Taiwan.
Coincidentally, your immediate suspicion of Jamicon branded caps in episode #824 (14:30) reflects that same fear. Still from the same article:
Further intelligence revealed that Kamei/Jamicon sources its electrolytes from Sanyo in Japan, and likely was not affected by the faulty electrolyte supply.
Industrial espionage implicated
A major cause of the plague of faulty capacitors was industrial espionage in connection with the theft of an electrolyte formula. A materials scientist working for Rubycon in Japan left the company with the secret electrolyte formula for the ZA and ZL series of Rubycon and began working for a Chinese company. The scientist then developed a copy of this water-based electrolyte. After that, some staff members who defected from the company copied an incomplete version of the formula and began to undersell the pricing of the Japanese manufacturers with this electrolyte to many of the aluminum electrolytic manufacturers in Taiwan. The subsequent electrolyte produced lacked important proprietary ingredients which were essential to the long-term stability of the capacitors and was unstable when packaged in a finished aluminum capacitor. The bad formulation of electrolyte allowed the unimpeded formation of hydroxide and produced hydrogen gas.
The report of Hillman and Helmold proved that the cause of the failed capacitors was a faulty electrolyte mixture used by the Taiwanese manufacturers, which lacked the necessary chemical ingredients to ensure the correct pH of the electrolyte over time, for long-term stability of the electrolytic capacitors. The further conclusion that the electrolyte with its alkaline pH value then had the fatal flaw of continual growth of hydroxide without conversion into the stable oxide, was verified on the surface of the anode foil both photographically and with an EDX-fingerprint analysis of the chemical components.
Maximum ripple capability is rated at a certain frequencies.
Basically, any professional engineer knows there is some risk with going with that new brand based on some accelerated life cycle testing on a small sample.
A lot of engineering is about lowering the risk and using "best practice". It's like the old "Nobody ever got fired for buying IBM/Fluke/Keysight etc".
In the case of caps, no engineer ever got fired for designing in Panasonic caps if it's within the budget. It's smart design.
If for some reason those Panasonic caps went tits-up because they had a production problem, then no one is going to hound you for the choice of using those Panasonic caps. If you used CapXon, well, good luck defending that choice.
So "best practise" is really about making sure you cover your arse with the same sized pillow as everyone else? Sigh.
Good brand caps are sometimes just good looking porns, not essentially good in products. For instance, a 85C NCC cap rated at 2khrs won't outlive a 105C CapXon cap rated at a same 2khrs.
Interesting how the supply uses Analog Devices parts, delta fans, Omron Relays, A Caddock precision divider, and then......5 lelon caps?!? Doesnt seem to me like they were really trying to save any money....besides those caps and steel chassis. (Im 10 minutes into the video). Im not sure if that means those caps have been properly speced, or they just have a nutso purchasing manager. God questin for Eric next time.
Interesting how the supply uses Analog Devices parts, delta fans, Omron Relays, A Caddock precision divider, and then......5 lelon caps?!? Doesnt seem to me like they were really trying to save any money....besides those caps and steel chassis. (Im 10 minutes into the video). Im not sure if that means those caps have been properly speced, or they just have a nutso purchasing manager. God questin for Eric next time.
It's likely that the designer did not specify a brand. The BOM could simply have "1000uF 10V RB 5mm pitch Electrolytic".
And/or Siglent get a good deal on Lelon caps and simply uses them in a ton of products.
Indeed, the BOM could actually specify a specific Lelon part number, and the designer simply picked that part from the company approved schematic parts list.
Whether or not someone at Siglent actually sat down and thought about and/or tested or investigated Lelon, and/or approved them and/or made any sort of cost/quality tradeoff is possibly, but I suspect more unlikely than not.
Maybe there is some really pissed off engineer at Siglent who's a Panasonic fanboy and speced those in, only to be usurped by the purchasing department and the powers-that-be.
Can be a whole host of reasons and scenarios.
It's likely that the designer did not specify a brand. The BOM could simply have "1000uF 10V RB 5mm pitch Electrolytic".
And/or Siglent get a good deal on Lelon caps and simply uses them in a ton of products.
Indeed, the BOM could actually specify a specific Lelon part number, and the designer simply picked that part from the company approved schematic parts list.
Whether or not someone at Siglent actually sat down and thought about and/or tested or investigated Lelon, and/or approved them and/or made any sort of cost/quality tradeoff is possibly, but I suspect more unlikely than not.
Maybe there is some really pissed off engineer at Siglent who's a Panasonic fanboy and speced those in, only to be usurped by the purchasing department and the powers-that-be.
Can be a whole host of reasons and scenarios.
LOL once I was desperate for a capacitor to use a in a prototype, so I pulled an old Crapston capacitor from an old monitor, tested it and it still read the full capacitance so I used it and it worked fine. Of course if it was for production, then I'd use a decent brand capacitor. I don't see the point on saving a few pence on a capacitor, only for it to go wrong and cost a lot more in future.
So how would one go about accelerated testing caps like this?
Off the top of my head I'd say:
- Chose at least two name brand, and two crap brands.
- Same temp range, rated hours @ similar ESR, size, etc.
- At least 5 samples of each type.
- Only buy from authorized distributors to avoid fakes (maybe not possible for the crap brands)
- Buy each one from 5 different suppliers (Digikey, Mouser, Farnall, RS etc) to hopefully avoid and batch related quality issues.
- Test the ESR and other parameters of each cap before testing. Might as well test everything I guess, cap, leakage etc
- Put them all on the same board with individual and identical bridge rectifiers and loads. No parallels!
- Pick a ripple current to stress the parts somewhat. Normally speced at 100KHz, but testing with normal 100Hz full wave should be fine. Although if you wanted to get fancy pantsy, 100KHz SMPS for each one.
- Pick a voltage close to the max working voltage
- Put in thermal chamber at say 85C
- Run for 1000 hours.
- Test all parameter of every cap every 100 hours, after letting settle to room temp.
- Also try and see any difference in internal heating with FLIR.
So how would one go about accelerated testing caps like this?
Off the top of my head I'd say:
- Chose at least two name brand, and two crap brands.
- Same temp range, rated hours @ similar ESR, size, etc.
- At least 5 samples of each type.
- Only buy from authorized distributors to avoid fakes (maybe not possible for the crap brands)
- Buy each one from 5 different suppliers (Digikey, Mouser, Farnall, RS etc) to hopefully avoid and batch related quality issues.
- Test the ESR and other parameters of each cap before testing. Might as well test everything I guess, cap, leakage etc
- Put them all on the same board with individual and identical bridge rectifiers and loads. No parallels!
- Pick a ripple current to stress the parts somewhat. Normally speced at 100KHz, but testing with normal 100Hz full wave should be fine. Although if you wanted to get fancy pantsy, 100KHz SMPS for each one.
- Pick a voltage close to the max working voltage
- Put in thermal chamber at say 85C
- Run for 1000 hours.
- Test all parameter of every cap every 100 hours, after letting settle to room temp.
- Also try and see any difference in internal heating with FLIR.
But if we remove the "reliability is paramount" constraint and accept your subsequent claim "and the no-name caps might perform just as well as the name brand ones" then choosing for no other reason (and you originally offered no other reason) than protecting ones professional reputation, reduces "best practise" to mean nothing more than CYA. Doesn't it?
I also think that there are people in all walks of life who like to delude themselves that they alone don't engage in a good bit of arse covering. Engineers included. They'll heap scorn on managers, on marketing, on customers and suppliers, on anyone and everyone else in order to maintain the delusion. A reality check does no one any harm.
In the real world a big part of best practise is "arse-covering".
There should be on-off session. E.g. once per day. Cut the power, allow everything to cool and restart. To simulate turn on-off events. Daily thermal expansion and contraction could play a role to the life of the component.
So how would one go about accelerated testing caps like this?
Off the top of my head I'd say:
- Chose at least two name brand, and two crap brands.
- Same temp range, rated hours @ similar ESR, size, etc.
- At least 5 samples of each type.
- Only buy from authorized distributors to avoid fakes (maybe not possible for the crap brands)
- Buy each one from 5 different suppliers (Digikey, Mouser, Farnall, RS etc) to hopefully avoid and batch related quality issues.
- Test the ESR and other parameters of each cap before testing. Might as well test everything I guess, cap, leakage etc
- Put them all on the same board with individual and identical bridge rectifiers and loads. No parallels!
- Pick a ripple current to stress the parts somewhat. Normally speced at 100KHz, but testing with normal 100Hz full wave should be fine. Although if you wanted to get fancy pantsy, 100KHz SMPS for each one.
- Pick a voltage close to the max working voltage
- Put in thermal chamber at say 85C
- Run for 1000 hours.
- Test all parameter of every cap every 100 hours, after letting settle to room temp.
- Also try and see any difference in internal heating with FLIR.
There should be on-off session. E.g. once per day. Cut the power, allow everything to cool and restart. To simulate turn on-off events. Daily thermal expansion and contraction could play a role to the life of the component.
Alexander.
In the end, the best people to ask about caps are not design engineers - it's the repair techs.