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October 2007

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Subject:
From:
"Wenger, George M." <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Wenger, George M.
Date:
Sun, 14 Oct 2007 21:41:18 -0400
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text/plain (209 lines)
On the failed boards you cross sections, did the copper pl
Rush,



On the failed boards you cross sections, did the copper plating have an

"hour-glass" shape (i.e., thicker near the outer-layers and thinner in

the middle)and were the cracking approximately in the vertical center of

vias?  Also, were the cracks in the barrel plating or was there

separation of the barrel plating from internal layers? 



Regards,

George

George M. Wenger

Andrew Corporation Wireless Network Solutions

Senior Principal FMA / Reliability Engineer

40 Technology Drive, Warren, NJ 07059

(908) 546-4531 [Office]  (732) 309-8964 [Cell]



-----Original Message-----

From: TechNet [mailto:[log in to unmask]] On Behalf Of [log in to unmask]

Sent: Sunday, October 14, 2007 4:15 PM

To: [log in to unmask]

Subject: Re: [TN] SV: [TN] URGENT HELP NEEDED:- non-destructive method

for via hole pl...





 

George, Werner,



These are unpopulated brds.

 

YES THERE ARE CPNS ON THE PANEL.(as per IPC-2221)

 

1) CPNS SHOW more than 0.0015" mini in the via holes (in cpns

representing 

via holes)

 

2) However, some assy have failed due to cracked copper.

 

3) 2 assy were X-sectioned and showed low copper ~ 0.001" in the vias

that  

cracked. (these are vias in the  brd)...            we do  have pretty

good 

plating quality....we check tensile elongation every 2 wks and

elongation always 

runs > 20%.

 

4) We X-secitoned some scrap brds...via plating was fine.

 

5) SO WE feel that, some brds may less plating in these via holes even  

though the cpns show adequate plating.

 

6) HENCE WE WANT TO MEASURE COPPER PLATING IN VIA HOLES (IN A BARE BRD)



NON_destructively.

 

Rush

818-415-0030

 

 

In a message dated 10/13/2007 4:55:02 PM Pacific Daylight Time,  

[log in to unmask] writes:



I  haven't see your product but just knowing the board i

Hi Rush,



I  haven't see your product but just knowing the board is a 20-layer 150

mils  PCB with a 1.5 mil thick copper requirement for the vias it sounds

like  this isn't a cheap assembly.  I guess that is the reason  you're

looking for a non-destructive measurement.  Unfortunately I  don't think

you are going to find a non-destructive technique for measuring  the

copper thickness in vias on a fully populated PCBA.  Werner's  comment

about a "classic case" is correct.  In fact I would add to his

statement

and say that a non-populated PCB retention sample is always a  good idea

as is non-destructive measurements on bare PCB's prior to  assembly.



Regards,

George

George M. Wenger

Andrew Corporation  Wireless Network Solutions

Senior Principal FMA / Reliability  Engineer

40 Technology Drive, Warren, NJ 07059

(908) 546-4531  [Office]  (732) 309-8964 [Cell]



-----Original  Message-----

From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner  Engelmaier

/*

Sent: Saturday, October 13, 2007 7:30 PM

To:  [log in to unmask]

Subject: Re: [TN] SV: [TN] URGENT HELP NEEDED:-  non-destructive method

for via hole plating thickness



Hi  Rush,

Here is a classic case as to why it is imperative to have coupons  as

part of 

the panel.

you state:

20 layers, ~150 mils  thick

Via holes are 20-22 mils finished; Required plating is 0.0015  min.

Also, for via holes, the finished hole size is totally  unimportant-you

need 

to know the drilled hole size.

Is the required  plating thickness 1.5 mils minimum? or measures how?

You also do not say  whether you have problems, and what the  problems

are.





Werner







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