Hi Steve and Mordechai,

In the first picture it looks like the trace under the dielectric is
superimposed on the pad. This looks like a condition called
"telegraphing" where the copper conductors or pads are pressed into the
dielectric and any copper in the outer layers leaving an impression that
is visible upon inspection.

The second picture is of a microvia. Note that the layer two copper is
very thick compared to the dielectric. So the amount of "b-stage"
dielectric is squeezed out between the conductors and the layer one
copper during lamination. This condition is called "glass lock" or
"glass crush".

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 Steve Gregory
Sent: December 5, 2012 11:49 AM
To: [log in to unmask]
Subject: [TN] A PCB defect that is not specified by IPC

Hi Mordechai,

I have not seen anything like this before. I've posted your pictures so
everyone else can see:

http://stevezeva.homestead.com/Pad_Wrinkle.jpg

http://stevezeva.homestead.com/Via_Xsection.jpg

Could you share what the overall stack-up of this board was supposed to
be and what prepreg thickness was used?

Steve

From: Mordechai Kirshenbaum 
Sent: Tuesday, December 04, 2012 3:16 PM
To: [log in to unmask] 
Subject: A PCB defect that is not specified by IPC


Hi Steve 

On routine visual inspection of an income PCB board we found a type of
the defect
that is not specified in any of the IPC standards (e.g  IPC-A-600
Acceptability of Printed Boards).

It looks like  wrinkles on  pads  and conductors (see fig 1 in the
attached file). We suspected that it was caused
by thick copper conductor on the second layer (under the outer layer).

We measured the copper and the dielectric thickness between the outer
and the second layers
and found that the copper thickness on the 2nd layer was relatively high
(70 micro-meter), and the 
dielectric thickness lower than specified (only 50 microns).

Have you seen similar defect?
What is the reliability impact? 
Is it acceptable for class 3?

Best regards
Mordechai Kirshenbaum
MOD, Israel

P.S. please feel free to post this question on the technet forum. 








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