In this image, note that the two purple ones are polymer caps where as the black on is a wet electrolytic cap.
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Polymer capacitor
Polymer capacitors, polymerized organic semiconductor solid-electrolyte capacitors and conductive polymer capacitors with different chemistry, are types of electrolytic capacitor with solid, rather than the more usual liquid, electrolyte. Names used for similar technologies are OS-CON (Sanyo trademark), Aluminum Organic Polymer Capacitors (AO-CAPS), Organic Conductive Polymer Aluminum Electrolytic Capacitor (OC-CON).
Characteristics
- Some types have longer life at higher cost than standard (liquid) electrolytics. 50Khours life at 85 °C. Others are specified typically for guaranteed 1000 hours at 105 °C.
- Equivalent series resistance (ESR) is lower than electrolytic of same value, and stable under varying temperature, unlike standard electrolytics.
- Working voltage up to around 35 V.
- Cathode is aluminum foil.
- A separator sheet is impregnated with electrolyte.
- Anode is aluminum foil with an oxide layer.
Benefits of Polymer Capacitors
Polymer capacitors are characterised by lower ESR and ability to handle higher ripple current than their wet electrolytic counterparts. They are also characterised by not changing their ESR when their operating temperature changes and also having a much longer life. Sanyo quotes a 10 times increase in lifetime for a 20degC reduction in operating temperature for their OS-CON polymer capacitors whist a wet electrolytic capacitor in comparison would increase lifetime by 4 times.
Low ESR
Low ESR is so important in electronics because the lower the ESR the faster the capacitor can discharge. This is a great benefit because it means the capacitors can respond faster to large current transitions. However there are several wet electrolytic capacitors which offer similar ESR as their polymer counterparts.
High Ripple
The high speed power delivery to the latest CPUs subjects the capacitors in the VRM to high ripple. This is why you will see polymer capacitors more often on vcore output on the latest motherboards as they can handle much more ripple than wet electrolytics ever will. Failure of electrolytic capacitors on vcore output can be partly attributed to exposure to ripple current that was beyond their specification.
Replacing Wet Electrolytics with Polymer Capacitors
Because some series of Polymer capacitors have lower ESR you can replace wet electrolytics with them but use about half the capacitance value instead. But it is important to first check the specification of both capacitors to see that you are not replacing a wet electrolytic with a polymer that has higher esr. Not all Polymer capacitors have lower ESR therefore just trying to obtain any polymer capacitor for your modding project is simply not going to be an upgrade.
