You could re-create this for your customer. We have done this using an IPC
test pattern, but any two traces could work if you can attach wires and
apply 0.3V/thousandths of an inch of spacing between traces. Add a drop of
DI water on the test location. For Enig nick the trace to expose the
copper. You can re-create the exact photos you have taken in about a
minute if as contaminated as you suggest.
A clean Enig board with un-nicked trace should last 15 minutes without
dendrites ( typically using 25mil spacing at 7.5V).
since you have created a plating process with the three required elements
of voltage bias, sacrificial anode, electrolyte (DI water and
contaminants)...air is not a required factor and this can occur under
coatings or internally under the right conditions.
Roger Mack P.Eng.
Manufacturing Specialist
Parker Hannifin Canada
Electronic Controls Division
1305 Clarence Avenue
Winnipeg, MB R3T 1T4 Canada
direct 204 453 3339 x373
[log in to unmask]
www.parker.com/ecd
From:
"Wenger, George M." <[log in to unmask]>
To:
<[log in to unmask]>
Date:
07-06-2012 04:36 PM
Subject:
Re: [TN] AW: [TN] Copper Dendrites
Sent by:
TechNet <[log in to unmask]>
I my opinion the photographs make it obviously clear that this is dendrite
growth. The question concerning PCB surface finish really doesn't matter.
The dendrites are growing from a SMOBC trace. What needs to be
determined is the contamination necessary for the dendrite to grow on the
PCB prior to application of solder mask or is the contamination coming
from the solder assembly process and getting through the solder mask to
the copper trace.
Regards,
George
George M. Wenger
Senior Principal Reliability / FMA Engineer
Andrew Corporation - Wireless Network Solutions
40 Technology Drive, Warren, NJ 07059
(908) 546-4531 Office (732) 309-8964 Mobile
E-mail: [log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Friday, July 06, 2012 12:19 PM
To: [log in to unmask]
Subject: Re: [TN] AW: [TN] Copper Dendrites
Hi Günter!
Got your pictures posted, they're here:
http://stevezeva.homestead.com/Dendrite_1.jpg
http://stevezeva.homestead.com/Dendrite_2.jpg
Steve
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Grossmann, Guenter
Sent: Friday, July 06, 2012 12:03 PM
To: [log in to unmask]
Subject: [TN] AW: [TN] Copper Dendrites
I sent the to Steve.
Cheers
Günter
>-----Ursprüngliche Nachricht-----
>Von: TechNet [mailto:[log in to unmask]] Im Auftrag von Victor Hernandez
>Gesendet: Freitag, 6. Juli 2012 17:55
>An: [log in to unmask]
>Betreff: Re: [TN] Copper Dendrites
>
>What happened to the pictures?
>
>Victor,
>
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of Paul Reid
>Sent: Friday, July 06, 2012 10:33 AM
>To: [log in to unmask]
>Subject: Re: [TN] Copper Dendrites
>
>Ah, Now I understand.
>
>Conductive filaments can grow particularly conductive anodic filaments.
>I was thinking of a dendrite of copper not conductive filaments. I
>expect dendrites to be larger and of pure copper but you may get
>dendritic growth with a contaminate, in the presents of water and with
>an electrical potential.
>
>Sorry for my misunderstanding.
>
>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 Guy Ramsey
>Sent: July 6, 2012 9:23 AM
>To: [log in to unmask]
>Subject: Re: [TN] Copper Dendrites
>
>I agree. I have seen dendrites grow under solder mask from on conductor
>to another, and from a PTH to a conductor, under solder mask.
>
>If the residue were benign, until exposed to water, and the coating
>were to protect it from exposure, it could help.
>
>Still, I am skeptical, that it would reduce risk of failure. It would
>need to be a designed process, not a band aid.
>
>It might make things worse.
>
>Guy
>
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of Graham Naisbitt
>Sent: Friday, July 06, 2012 8:23 AM
>To: [log in to unmask]
>Subject: Re: [TN] Copper Dendrites
>
>Hi Neil
>
>I stand by my earlier posting on this. Neither a solder resist nor a
>conformal coating will PREVENT dendrites, they might delay it for a
>while, but then what is lurking and festering underneath..just when you
>thought it was safe to go back in the water!?
>
>Graham Naisbitt
>
>
>On 5 Jul 2012, at 19:50, Neil Atkinson wrote:
>
>> Thanks everyone for comments so far - haven't been on Technet for a
>while
>so it was good to get such good responses.
>>
>> Really miss Werner for questions like this...
>>
>> Actually we have never seen a failure for dendrites; however, we have
>a
>customer who has a past problem with another supplier due to dendrites
>on PCBs and as a result wants us to cover vias with solder resist or
>conformal coating.
>>
>> Tha,
>>
>> Neil
>>
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