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FLEX Circuit Discoloration

Mythical Knights
By Mythical Knights
in Hobby Electronics
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Putting this out there if anyone knows or has any info about this sort of phenomenon.

 

We received some rigid flex boards the other day and noticed some strange discoloration on them. We don't have any info about if they are good or bad or what even causes it. To me it almost looks like either a stain or burns. When you run your fingers across them, you feel no bumps or uneveness to them at all. I personally don't know the process of making a rigid flex therefore I don't know how this could be possible. There isn't anything in IPC that talks about it either.

 

If you guys have any info or experience on this, let me know.

20190904_152944[1].jpg

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4 hours ago, mariushm said:

Not an expert on this but I'd make a guess.

 

Maybe the glue used didn't cure properly in some places or trapped tiny bits of air?

I could maybe see the glue not curing. You can't feel any bumps or anything so it's tough to think it's air. However, maybe it's one in the same. Where there may have been bits of air could maybe cause the glue to cure improperly. Then after they were pressed together any bumps could have been removed. Honestly I really don't know. They test ok but I just wish I knew what it was from.

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I was initially thinking this could be de-lamination, but it looks like the discoloration is localized to the copper. Could be staining from the copper not being cleaned/handled properly at the fab house. This would definitely be rejected by most companies.

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On 9/6/2019 at 5:58 PM, bob345 said:

I was initially thinking this could be de-lamination, but it looks like the discoloration is localized to the copper. Could be staining from the copper not being cleaned/handled properly at the fab house. This would definitely be rejected by most companies.

I would agree with you on this. We haven't requested anything from this board house before so it's a new experience for all of us.

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