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November 2007

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Subject:
From:
"Stadem, Richard D." <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Stadem, Richard D.
Date:
Wed, 14 Nov 2007 14:57:26 -0600
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text/plain (114 lines)
Were the boards wave-soldered? 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Tom Burek
Sent: Wednesday, November 14, 2007 1:57 PM
To: [log in to unmask]
Subject: Re: [TN] Green Growth between PCB traces

Thanks Phil,
I read the article. 
In assembly, we use a No Clean (paste) process, but re-work stations would use a rosin flux.
From the information I have, there was no re-work performed on these assemblies.

Thanks again for the response.

Tom Burek, CID+




"Phil Nutting" <[log in to unmask]>
11/14/2007 11:47 AM

To
"TechNet E-Mail Forum" <[log in to unmask]>, "Tom Burek" 
<[log in to unmask]>
cc

Subject
RE: [TN] Green Growth between PCB traces






Tom,

Go to the Kester site and look for a tech note "Green Corrosion with Rosin Flux?".

This may answer your questions.

Phil 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Tom Burek
Sent: Wednesday, November 14, 2007 12:44 PM
To: [log in to unmask]
Subject: [TN] Green Growth between PCB traces

Hello everyone,
Has anyone ever seen or experienced the phenomenon of this green growth between the traces and even on some of the pads.
It almost appears as if it is leaching out from under the etchback of the traces into the space between the traces. 
Oddly enough it is only on one side of the board, the bottom side, opposite the component side.
It will not wash off with DI or Alcohol and a Q-tip, however it will scrub 

off with a stiff bristle brush or very gently with an exacto knife.
The soldermask is very thin in spots, (white solder mask).

The PCB is ENIG with white soldermask.  FR4 material (IPC-1401/21).
The boards had just gone through HALT testing, (Thermal Shock: 2 hrs. @ 85°C then 2 min. 5 sec. swing to  -40°C for 2 hrs. This was repeated until 

it failed after 136 hrs.) We think this green stuff might have caused the failure. 
 With the temperature swings, often there is condensation created so, possibly created by humidity? 
Is there something in the PCB fabrication process that could have lay dormant until it experienced thermal shock?

I know an analysis of the green stuff is necessary, but I was wondering if 

anyone has ever seen of experienced this type of growth before.

Thank you in advance.

I have attached some pictures, but I know somehow they are suppose to get to Steve to post. 



Tom Burek, CID+

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