Hi Gerald!

I still maintain my web page for images and I have yours posted. They are here:

IMG_3021.JPG

IMG_3022.JPG

IMG_3023.JPG

IMG_3024.JPG

IMG_3026.JPG

IMG_3029.JPG

Good lord, that looks pretty bad! I think you meant R15 as being the one with the cracks, I’m surprised that there aren’t more cracks. That laminate is starting to come apart from the heat. Are the other boards that don’t have cracks as discolored as this one is beneath the three resistors ? Do the resistors really run that hot ?

The resistors in the photo look brand new to me, like they’ve been replaced, even the sleeving on the leads looks pristine. Look at all the powdery deposits around in the area. I think that something special happened with this board and it smoked R15 big time, which led to the laminate breaking down and failing. I think something catastrophic happened with this particular board and it has been reworked with new resistors...

Steve

From: [log in to unmask] 
Sent: Friday, September 21, 2012 4:22 PM
To: [log in to unmask] 
Subject: What could have caused the PWB laminate cracks???

September 21, 2012

 

We have an OEM who is having problems with cracks in board laminate.  The six PIX are for the CCA involved.  If you look at Image 3026 and view the area around R13 you will see the cracks radiating from around the PTH.  The CCA is FR4 epoxy 0.062 in thick with Type UR conformal coating.  The area under the power resistors is not conformal coated. You can easily see this since the other areas are conformal coated and have brown color.  This brown color is due to the operating temp which is most likely > 100C.  

 

This CCA design was fully qualification tested and passed all tests in 50C ambient temp environment.  The CCA runs hot as you can see from viewing the other images.

 

We have fielded many of the same CCAs previously with no evidence of cracking.

 

Any input on what could have caused the cracks would be appreciated.

 

Not sure if you are still the go to person who maintains the photo library for tech net; if so, can you please post the PIX and send out e-mail to tesn net on my behalf.  Thanks.

 

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