difference % solid polymer cap and aluminum electrolytic cap

[s977491]

May I ask how much cheaper is aluminum electrolytic cap against solid polymer cap.

Also, I read that it seems solid polymer cap is superior to electorlytic cap in all aspect except price, is this true?

Also, which solid polymer cap is good and which is bad? Thanks.

[Melfman]

Re: difference % solid polymer cap and aluminum electrolytic cap

Not sure on the price difference, but solid polymers do have their drawbacks.
1st, if they fail it's more likely to be short-circuit, and 2nd they're pretty poor at low frequency.
While a liquid electrolyte cap might be good for 90% of it's current rating at 500Hz, the solid polymer type can only handle 5% of rated current.
At 5KHz they'll handle more like 20% of their rated current. Current ratings are typically given for 100KHz operating frequency.
Having said that, most motherboard uses won't be a problem frequency-wise unless something else breaks first. Also their lower ESR and better ripple current (at proper frequency) means you need less of them to do the same job.

Melfman

[PeteS in CA]

Re: difference % solid polymer cap and aluminum electrolytic cap

1st, if they fail it's more likely to be short-circuit, and 2nd they're pretty poor at low frequency.

The guidance we got from either UCC or Nichicon (I can't remember which) was that polymer caps rated for greater than 16V tend to fail short, while those rated 16V and lower tend to fail open.

[gonzo0815]

Re: difference % solid polymer cap and aluminum electrolytic cap

The end user prices on solid polymer caps are very high (e.g. Sanyo Oscon SEPC 820uF 4v is about 2$ to 3$ each).
An Al cap with the closest ESR & ripple capacitance is about on third of that.

[s977491]

Re: difference % solid polymer cap and aluminum electrolytic cap

Thanks a lot.

[Logistics]

Re: difference % solid polymer cap and aluminum electrolytic cap

I noticed that Solid's also seem to have higher leakage current. What effect does this have?