Ceramic Capacitor Temo Coeff - Op vs Ship - Page 1
Forum section: electronics / projects

author: Pack34
author_rank: Frequent Contributor
timestamp: September 18, 2017, 04:07:06 pm
content: Just to double check myself. The temperature coefficient rating for ceramic capacitors accounts for the claimed operational characteristics.So an X5R capacitor should have the same 0.1uF 5% rating throughout the -55C to 85C range but exceeding this is fine during shipment and assembly, correct? The reduced maximum temperature rating of 125C on an X7R is only gained when the device is turned on. Correct? Excessive heat during assembly, rework, or shipment shouldn't be an issue?

author: Benta
author_rank: Super Contributor
timestamp: September 18, 2017, 04:12:32 pm
content: You'll need to consult the datasheet.There are several temperature ratings:OperatingStorageAnd sometimes soldering profile

author: wraper
author_rank: Unknown
timestamp: September 18, 2017, 04:33:38 pm
content: Incorrect, and 5% tolerance is only when capacitor is just reheated and under rated test conditions. X5R has +-15% in working temperature range. Capacitance drops with ageing, restored when soldered/heated, then dorps again. Easily -10-20% from what was at the beginning after several years (large capacitance drop initially, slows down over time). Capacitance drops with DC voltage applied, by up to 90% at max rated voltage, worst for small capacitors with large capacitance, like 10-30% for not extreme cases.http://rohmfs.rohm.com/en/products/databook/applinote/ic/power/switching_regulator/cera_cap_appli-e.pdfhttp://www.niccomp.com/resource/files/ceramic/VoltageCoefficientofCapacitors-032012-R1.pdfhttp://www.johansondielectrics.com/ceramic-capacitor-aging-made-simple

author: drussell
author_rank: Super Contributor
timestamp: September 18, 2017, 04:37:02 pm
content: Quote from: Pack34 on September 18, 2017, 04:07:06 pmUhhh... not even close. The capacitance of a ceramic capacitor varies widely in operation. The "R" in X5R/X7R means +- 15% over the temperature range, so you could be 20% out on a supposedly "5% tolerance" capacitor.And that is just temperature. You also need to take applied voltage into account. Depending on the DC bias applied on a ceramic capacitor they can sometimes be only a tiny fraction of the marked capacitance. You need to choose very carefully, taking all aspects of your application into account.QuoteYou need to look at the datasheet for storage vs. operating parameters.Some of the capacitor companies' websites have tools to investigate environmental factors, etc. more closely and compare various parts. Murata and TDK do for sure, many others likely have some kind of comparison tool so you don't need to study a gazillion datasheets just to narrow down your search.Beware the ceramic capacitor boogeyman!

author: wraper
author_rank: Unknown
timestamp: September 18, 2017, 04:39:28 pm
content: Basically if you use any MLCC other than NP0/COG where stable capacitance us needed, you will be bitten in the ass pretty soon. Even when used on power rail, capacitance drop should be considered.

author: drussell
author_rank: Super Contributor
timestamp: September 18, 2017, 04:40:28 pm
content: Here's a Maxim application note that has some good background:https://www.maximintegrated.com/en/app-notes/index.mvp/id/5527I'm sure there are many others, as well....