polymer caps

[halaster79]

is it safe to use aluminum polymer caps to replace the aluminum caps, as long as the uf and v are the same, they have the right diameter and wire space, and are of equal or lesser ESR, on a motherboard? in the datasheet when it says polymer cap ESR is 9, does that mean the same thing as .009 on an aluminum cap?

[mariushm]

Re: polymer caps

Polymer capacitors usually have lower esr compared to their electrolytic counterparts. ex a 1500uF 6.3v electrolytic may have 10 mOhm esr, while a polymer would be smaller in height and slightly lower esr.

On motherboards, yes, in most locations it should be safe to replace electrolytic capacitors with polymer capacitors. Try to keep the esr relatively the same though, or a bit lower.
In the VRM circuit (those capacitors very close to the cpu socket) it should be safe to use polymer capacitors of slightly lower capacitance and voltage.

For example they may use 4-8 x 1'000-1'500uF 6.3v capacitors in parallel to obtain lower esr. They don't need 6'000-10'000uF and they don't need a 6.3v rating when the top voltage on the cpu would be less than 1.5v, but they simply used 6.3v and 1000-1500uF per capacitor to get the lowest esr possible in the height available there by the cpu (any higher would have blocked cpu coolers). If replacing those with polymer capacitors, you could replace the electrolytics with 4v rated (or even 2.5v rated) polymers and only 680-820uF in capacitance, as they'll have the same esr and the total capacitance would still be more than enough.

[2andrewd]

Re: polymer caps

why would you want to use polymer over E.L. Mehhhh

[halaster79]

Re: polymer caps

bored and looking at the Nichicon PLG series on digi-key. they seem to have really ultra low ESR if 9 means the same as .009 ESR on regular aluminum caps. some regular aluminum ultra low ESR caps are getting kinda hard to find, or are starting to get old, like the 1200uf 6.3v Rubicon MCZ, and some of the Nichicon HN and HZ series, or could be fakes.

[momaka]

Re: polymer caps

why would you want to use polymer over E.L. Mehhhh

Because polymer caps have solid electrolyte, so they have better reliability at high temperature. This is especially important for Intel socket 775 and newer motherboards, where the caps can be placed under the heat sink.

Polymer caps are also smaller. With everything being shrunk-down these days, polymers are almost a necessity for new motherboards.

if 9 means the same as .009 ESR on regular aluminum caps.

Yes.
Many polymers state their ESR in mOhms (milliOhms), which is 1/1000 of an Ohm, whereas old electrolytics typically specify ESR in Ohms.

So 9 mOhms = 9/1000 Ohms = 0.009 Ohms

[halaster79]

Re: polymer caps

Is ripple current higher 6000 or equal safe when replacing a lower ripple current aluminum 1200 cap, for example?

[momaka]

Re: polymer caps

Is ripple current higher 6000 or equal safe when replacing a lower ripple current aluminum 1200 cap, for example?

Yes.
The Ripple Current (RC) rating of a cap simply specifies how much AC current the cap can take before it starts to overheat internally. Thus, if the old caps are only rated for 1200 mA of RC and they worked for many years, then the new caps will work for even longer, as the ripple current in the circuit won't get anywhere near their maximum RC rating.