Hi Ramakrishnan,

I think that a microetch is essential for finding PWB copper cracks.
There is just no way to know if in the polishing you have smeared the
copper and that will give you a false positive reading. 

You have to learn how to do the microetch however. Too much of a
microetch and the electroless copper line looks like a crack. Not enough
microetch and there is a possibility of a copper smear covering cracks.

If you want to send me a couple of photos I'll look at them and tell you
if I think the microetch is correct or not. 

Sincerely,  

 

Paul Reid 

Program Coordinator  

PWB Interconnect Solutions Inc. 
235 Stafford Rd., West, Unit 103 
Nepean, Ontario Canada, K2H 9C1 

613 596 4244 ext. 229  

Skype paul_reid_pwb 
[log in to unmask] 

 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ramakrishnan
Saravanan
Sent: December 22, 2012 10:03 AM
To: [log in to unmask]
Subject: [TN] MICRO ETCH

Dear Mr ,

We have a in house facility for making hi reliability PCBs.

We use Park Nelco N4000-6 material (Tg=175 C ).

We use hot mounting techniques for PWB coupon micro section.

We polish up to 5 microns normally bur if a problem is found we go up to
0.05 micron polish.

We don't do micro etch. A Hi reliability PCB has failed in the field
trials.

We analyzed  the coupon again  no problem found. We polished up to 1
microns  still no problem found.

But when we micro etched  the specimen we found a barrel separation.

Do the micro etch is essential in finding a fault?.

What are the false alarms possible and how to exclude ?

Kindly advise . regards.

Ramakrishnan Saravanan

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