Tag Archives: capacitors

What are Aluminum Polymer Capacitors?

Choosing the right capacitors can make a big difference in the reliability, longevity, cost, and board size of your design. But most engineers don’t know which capacitors to choose for which applications. In this episode of Chalk Talk, Amelia Dalton chats with James Lewis from KEMET about the fascinating and surprising world of capacitor technology.

What are Aluminum Polymer Capacitors? – [Link]

They’re ‘Not’ JUST Capacitors

James Lewis from Kemet has made a presentation to address some of misconceptions about capacitors like how you should de-rate capacitors.
James said that de-rating depends on the chemistry and configuration of a particularly capacitor.  So he started by asking a question: Should capacitors be de-rated 50%? And the answer was not a simple true or false. It was: it depends…

James talked about the typical construction of Multilayer Ceramic Capacitor(MLCC), Aluminum Electrolytic(wet one), Tantalum, Polymer Electrolytic and Supercapacitors.

James talked about the Temperature Coefficients diagram for various types of Ceramic Capacitor like: YV, Z5U, X5R, X7R, U2J and C0G [Ceramic Capacitor].

Temperature Coefficients diagramWe can see that MLCC capacitance ranges, and Coefficients depend on type.

Another key point was about capacitance change vs DC bias in MLCC. It’s about the role of package size in capacitance lose over DC bias. He compared 10nf and 6.3v rated 1206 package capacitor with same one in 0805 package. Results showed that the 1206 one lost 2% of capacity, while the 0805 lost 50% at 6V. James said that the 0805 package is thinner than the 1206 one, so we need to put more layers into the design to get more capacity. So thinner package leads to worse coefficients.

He pointed out that the capacitance of Wet Aluminum Capacitors is affected on shelves, and he explained how to reform/self-heal them.

James also explained why it’s safer to use Polymer Electrolytic rather than using Tantalum Capacitors, and why Polymer Electrolytic when fails, it fails safely.

TantalumsHe ended his presentation up by talking about Supercapacitors, and he made a walkthrough the tools Kemet provides:
KEMET Catalog App for Mobile Devices
Capacitor Simulator K-SIM 
KEMET Engineering Center (capacitor technical content)

[Presentation Slides]

How To Select a Capacitor

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Sanket Gupta @ blog.octopart.com has written a capacitor select guide. The article goes through aluminum electrolytic capacitors, ceramic capacitors, Tantalum Capacitors, mica capacitors, film capacitors and Polymer Capacitors.

In this blog, we will explain all the different types of capacitors, their merits and demerits, and popular applications. We have included some recommendations for commonly used capacitor series with high supply chain availability from Common Parts Library and Seeed Studio’s Open Parts Library

How To Select a Capacitor – [Link]