Yes, It is so, and then you loose the whole board....
Gaby
----- Original Message -----
From: "Rick Smith" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, November 30, 2006 5:21 PM
Subject: Re: [LF] black pad
> In my experience, w/gold boards, when removing parts, cleaning solder off
> the pads, and re-installing parts, eventually the nickel/ solder bondable
> surface area decreases to the point where solder no longer sticks, (like a
> de-wetted solder Iron tip).
>
> Im guessing Im not the only one who has noticed this? Anyways my focus
> with these type of boards has been to have excellent up-front processes to
> limit touch-up and preclude rework...
>
>
> Rick Smith
> Product Engineering
> Celestica Aerospace Technologies Corporation
> 4616 West Howard Lane
> Building One Suite 100
> Austin, Texas 78728
> Phone: 512-615-8591
>
>
>
> "Stadem, Richard D." <[log in to unmask]>
> 11/30/2006 07:40 AM
>
> To
> "\(Leadfree Electronics Assembly Forum\)" <[log in to unmask]>, "Rick Smith"
> <[log in to unmask]>
> cc
>
> Subject
> RE: [LF] black pad
>
>
>
>
>
>
> Rick,
> What do you mean when you state "Gold boards also have limited
> reworkability because of the nickel?"
>
> -----Original Message-----
> From: Leadfree [mailto:[log in to unmask]] On Behalf Of Rick Smith
> Sent: Wednesday, November 29, 2006 9:11 AM
> To: [log in to unmask]
> Subject: Re: [LF] black pad
>
> Don't forget thin gold coverage problems which is a major issue with PCB
> suppliers trying to save money on gold application. This can be
> inspected with SEM/Backscatter method, but it is very hard to inspect
> with the naked eye or even under magnification. XRF will tell you gold
> is there & thickness, but not show the holes in the surface that are
> typically found when suppliers scrimp.
>
> Remember the gold is supposed to be only "flashed" on; thin enough to
> keep the nickel from oxidizing because solder won't stick well to nickel
> if it is oxidized. If the nickel is not covered on the PCB, then in
> assembly solder joint integrity is adversely affected and we see more
> black-pad.
>
> Too much gold is the enemy, embrittling solder joints.
>
> Gold boards also have limited reworkability because of the nickel.
>
> The key is to select a board supplier that has good process controls and
> the right equipment to verify gold coverage, and for the PCBA process
> engineer to control the solder process effectively to limit rework.
>
> my thoughts, sorry for rambling.
>
>
> Rick Smith
> Product Engineering
> Celestica Aerospace Technologies Corporation
> 4616 West Howard Lane
> Building One Suite 100
> Austin, Texas 78728
> Phone: 512-615-8591
>
>
>
> "Wenger, George M." <[log in to unmask]> Sent by: Leadfree
> <[log in to unmask]>
> 11/29/2006 06:56 AM
> Please respond to
> "(Leadfree Electronics Assembly Forum)" <[log in to unmask]>; Please
> respond to "Wenger, George M." <[log in to unmask]>
>
>
> To
> [log in to unmask]
> cc
>
> Subject
> Re: [LF] black pad
>
>
>
>
>
>
> I think that the fear of brittle failures with ENIG surface finish stems
> from the fact that there isn't a known root cause for the failure.
> Unfortunately, it appears that this research report doesn't calm those
> fears because the root cause is still unknown. I haven't read the
> report but it appears from the information Wolf-Dieter provided that we
> know exactly what we knew years ago:
>
> 1. ENIG Chemical Suppliers Provide Good Chemistry 2. Solder / Paste
> Suppliers provide Good Solder 3. Assemblers Use Good Soldering Processes
> 4. Therefore the problem must be some inaccuracies of cleaning and
> surface plating by some PCB fabricators.
>
>
> Regards,
> George
> George M. Wenger
> Senior Principle FMA / Reliability Engineer Wireless network Solutions
> Andrew Corporation, 40 Technology Drive, Warren, NJ 07059 (908) 546-4531
> [log in to unmask]
>
>
> -----Original Message-----
> From: Leadfree [mailto:[log in to unmask]] On Behalf Of SCHMIDT,
> WOLF-DIETER - PFHO
> Sent: Wednesday, November 29, 2006 3:19 AM
> To: [log in to unmask]
> Subject: [LF] black pad
>
> Hello Gaby,
>
> a few weeks ago the research report on that topic, carried out by Andus
> (PCB-manufacturer) and Fraunhofer Institute, was published. The result
> based on technical analysis and a poll asking a lot of PCB manufacturer
> as well as assembling companies showed that neither the type oc
> chemistry (e.g. the chemistry supplier) nor the type of solder nor the
> soldering process itself is the reason for black pad. The only remaining
> root seems to be some inaccuracies during running the board production
> process - mainly the chemistriy of cleaning and surface plating.
>
> The same information I received two years ago from Eric de Kluizenaar
> (ex Philips Eindhoven).
>
> Best regards
>
> Wolf-Dieter Schmidt
> -----------------------------------------------------------
> THALES Defence Deutschland GmbH
> Industrial Engineering
> Land & Joint Systems
> Ostendstrasse 3
> D-75175 Pforzheim - Germany
> -----------------------------------------------------------
> Phone: +49 7231 15 3386
> Fax: +49 7231 15 3390
> mailto: [log in to unmask]
> http://www.thalesgroup.com
>
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