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April 2005

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Subject:
Re: gold vs copper plating on pcb's - Black PAD???
From:
John Burke <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, John Burke <[log in to unmask]>
Date:
Fri, 29 Apr 2005 09:57:59 -0700
Content-Type:
text/plain
Parts/Attachments:
text/plain (198 lines) 
If you are trying to detect it you have some kind of a
problem.......generally.

Quickest way I have found as a fast screen is to do an IPC tape test, and
run trial batches through print and re-flow without a component load and
inspect the result.

It is also important to differentiate between black pad and skip plating,
the chemical result can look the same but the trigger mechanism root cause
is completely different, and the skip  plate phenomena is much more of a
random effect, and much more difficult to find "after the event" - I would
go for immersion Ag since as Werner points out the black pad problem may
actually become worse with LF solders.

Add to this that higher thermal excursion will make matters worse
particularly with ENIG since area array packages will put high strain on the
brittle intermetallics formed on that finish at the nickel interface.

Ken, call me if you want to chat about it.

John



-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Kanaiyalal Patel
Sent: Friday, April 29, 2005 9:17 AM
To: [log in to unmask]
Subject: Re: [TN] gold vs copper plating on pcb's - Black PAD???


All,
How is to detect black pad? Can it be inspected at PCB
level? I guess no. Is it the after reflow soldering
phenomena?

Re,
Ken Patel


--- Werner Engelmaier <[log in to unmask]> wrote:
> Hi Bob,
> First, with ENIG you do not solder to gold, but to
> the underlying nickel;
> Second, soldering to Ni requires more thermal
> energy, thus higher temperatures, and that is really
> bad news on top of the T-increase necessary for
> LF-solders;
> Third, the 'black pad' issue will not go away with
> LF-solderas,but actually may become worse.
> Thus, Immersion Ag is a good choice.
> Werner Engelmaier
>
> -----Original Message-----
> From: Jeffrey Bush <[log in to unmask]>
> To: [log in to unmask]
> Sent: Wed, 27 Apr 2005 07:14:42 -0400
> Subject: Re: [TN] gold vs copper plating on pcb's
>
>
> If you stick with ENIG and do not test Immersion
> Silver then I am sure
> you will be doing future testing to combat the
> issues with ENIG.  Monies
> are being put into the development if silver and
> several toughed
> formulas are coming out that have excellent
> resistance to TC and do not
> have the issues associated with ENIG.  OSP is also
> seeing some
> development, but I do not see this as a viable
> alternative today.
>
> Jeffrey Bush
> Director, Quality Assurance and Technical Support
>
> VERMONT CIRCUITS INCORPORATED
>   76 Technology Drive - POB 1890
>     Brattleboro, Vermont 05302
>       Voice: 802.257.4571.21 Fax: 802.257.0011
>            http://www.vtcircuits.com
>
>
> -----Original Message-----
> From: Bob Arciolla [mailto:[log in to unmask]]
> Sent: Tuesday, April 26, 2005 4:41 PM
> To: [log in to unmask]
> Subject: [TN] gold vs copper plating on pcb's
>
> Good Afternoon all,
>
> Our company will be switching over to lead free and
> we have received
> sample pcb's from one of our vendors and one board
> has gold (ENIG) for
> the traces and one has copper (OSP). From some of
> the emails I have seen
> on Technet it appears that gold is what most of
> companies are going to
> be using? Is this correct or is there some other
> materials we should be
> looking into to use? Is the gold more reliable than
> the copper?
> Any input would be greatly appreciated.
>
>
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>
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