Author Topic: Ceramic capacitor cracking  (Read 1210 times)

0 Members and 1 Guest are viewing this topic.

Offline zenerbjtTopic starter

  • Regular Contributor
  • *
  • !
  • Posts: 69
  • Country: gb
Ceramic capacitor cracking
« on: August 30, 2020, 10:38:34 pm »
Hi,
This is the best thing ive read on ceramic cap cracking
https://www.youtube.com/watch?v=QgKY5QWehME&feature=youtu.be

...however, at 17:47 onwards, it seems to suggest that a lot of flexion can be tolerated....up to "4mm".

I work  with a PCB  which is approx 15cm by 25cm and it has multiple 47uF, 16V, X6S, 1210 caps on it. They are  placed in both directions, (so one of the directions  is wrong).

Being high value, the problem is worse, but i need  the best ceramic cap crack video/tutorial out there to convince them that a change to Flexiterm/Thru-hole etc is worth while...they dont want to re-spin the PCB.
Do you know of  the best tutorial/video on this subject.?
 

Offline temperance

  • Frequent Contributor
  • **
  • Posts: 687
  • Country: 00
Re: Ceramic capacitor cracking
« Reply #1 on: August 31, 2020, 12:35:42 am »
Are those capacitors on the edge of the board? Ceramic caps usually crack when the board are being de-penalized and the capacitors are perpendicular to the board edge.

If this is related to the question about connectors and connecting batteries, then inrush current is the problem.
« Last Edit: August 31, 2020, 12:39:21 am by temperance »
 
The following users thanked this post: zenerbjt

Offline zenerbjtTopic starter

  • Regular Contributor
  • *
  • !
  • Posts: 69
  • Country: gb
Re: Ceramic capacitor cracking
« Reply #2 on: August 31, 2020, 09:11:23 am »
Thanks, but no the ceramic MLCCs are away from the edge, but according to the video in the top post.....depanelization is just one factor, not the main factor. Its not clear though, how much board bending causes cracking.

..Thus if you bring this up in a company, and request changes, people just shrug it off and ignore it.
 

Offline TheMG

  • Frequent Contributor
  • **
  • Posts: 867
  • Country: ca
Re: Ceramic capacitor cracking
« Reply #3 on: September 02, 2020, 10:36:57 pm »
Just design the enclosure/chassis to be rigid enough and properly supports the PCB to avoid bending/flexing. Good support around areas of the PCB with any connectors which will be inserted/removed more frequently, etc
 
The following users thanked this post: zenerbjt

Offline Doctorandus_P

  • Super Contributor
  • ***
  • Posts: 4004
  • Country: nl
Re: Ceramic capacitor cracking
« Reply #4 on: September 04, 2020, 03:26:32 am »
Reminds me of a video where Davey Jones lets out the magic smoke of a 50V 20A power supply.
In a followup video it's explained that ta ceramic cap just under the screw terminals was the culprit. You need to exert some force to the screw connectors for the 20A cable, which flexes the PCB and damages the cap.

The simplest solution is to not flex the PCB (too much) during handling & mounting.

Ther are special ceramic caps which have a little bit of flexibility built in, but you probably have to pay extra for that. Dave also did a video on those.
 
The following users thanked this post: zenerbjt


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf