?'s about surface mount caps etc. - Page 1
Forum section: electronics / beginners

author: KD0CAC John
author_rank: Frequent Contributor
timestamp: May 24, 2014, 03:06:37 pm
content: Most of my limited experience is with old through-hole gear .Just got a few rolls of of SMD caps from one of the members here and thought about IDing , then thought about spec's .One roll was small enough that there were no markings .I did use my Smart-Tweezers to read the cap value .But then thought about the other ratings like temp , voltage , frequency range etc. ?How to figure these spec's out , or if they are needed for SMD size components ?I did see Dave's video about different caps .But went away with mostly the bad things about each kind of capacitor .Have to ask Dave to do a part 2 with the perspective more towards why you need the of each type ?Thanks John

author: amyk
author_rank: Super Contributor
timestamp: May 24, 2014, 03:22:04 pm
content: Destructive testing.

author: KD0CAC John
author_rank: Frequent Contributor
timestamp: May 24, 2014, 03:37:14 pm
content: Ya , that was a thought , having a bunch of them .Too bad I'm not in a UL lab and I can blow up other people's goodiesWould these all be considered ceramic caps ?Not enough description to answer , they are all rectangular tinned at both ends , ceramic looking , not the aluminum type SMDs .

author: theatrus
author_rank: Frequent Contributor
timestamp: May 24, 2014, 04:27:46 pm
content: More or less guaranteed to be ceramic.Based on the case size and measured capacitance you can wag the max voltage. Testing what dielectric it is is harder.

author: SeanB
author_rank: Super Contributor
timestamp: May 25, 2014, 07:34:41 am
content: Voltage rating, apply 10V bias then measure capacitance ( via a DC blocking film capacitor of about 10x the capacitance at 0V and a voltage rating of over 50V) and look up what it drops to to get an idea of material and voltage rating. To test breakdown turn up the voltage till it goes short. To finish material type heat it with a soldering iron or heat gun set to low and see the change in value.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 25, 2014, 08:18:53 am
content: By breakdown, you may be at it a while. I've heard of 6.3V caps shorting at 120V+. Probably varies a lot from part to part, too.Capacitance change with bias is a poor indicator. By that measure, a 1uF 0805 might be only 16V while a 0.1uF 0805 (same material) might be solid to 50V or more. Same material, same construction, just more and thinner layers. Which is good to keep in mind, in general, really.If you have the means of measuring dissipation factor, add that to the list. Higher K materials (with codes like Y5V and Z5U) are very poor (>10%), medium K (X7R, Y5P) are reasonable (1-10%), and low K (C0G) are very low loss (< 0.1%).On the upside, C0G are almost always white, porcelain in appearance, while high-K types are yellow, orange, tan or brown sort of colored.Tim

author: KD0CAC John
author_rank: Frequent Contributor
timestamp: May 26, 2014, 01:48:40 pm
content: I now have some homework to do , thanks

author: KJDS
author_rank: Super Contributor
timestamp: May 26, 2014, 02:31:17 pm
content: np0 is more green, whereas X5R and X7R is brown