The thickness alone is only part of the equation leading to
embrittlement. The total volume of gold as a percentage by volume within
the resultant solder joint is the critical factor. There is a lot of new
work that shows anytime you increase the gold content of a solder joint
by more than 1%, the chances of having gold embrittlement greatly
increases. So a gold layer 2 uinches thick is not likely to greatly
reduce cycles to failure. But if your pads are very small such as a
.004" flip chip pad with no solder paste added (reflowing the flipchip
solder only) and you put on a 5-8 uinch gold layer over nickel, then you
are approaching or exceeding the 1% limit. Having to form the IMC with
nickel doesn't help.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Guy Ramsey
Sent: Friday, December 29, 2006 1:33 PM
To: [log in to unmask]
Subject: Re: [TN] Questions on ENIG VS gold plating
Two would be fine if you could control the thickness across the board.
I am not aware of any either. But, electroplated gold is another story.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Lee parker
Sent: Friday, December 29, 2006 1:55 PM
To: [log in to unmask]
Subject: Re: [TN] Questions on ENIG VS gold plating
Guy
If two micro inches of gold is an embrittlement threat, then ENIG must
be considered equally as dangerous. I am hardly a fan of ENIG, but I am
unaware of any documented ENIG embrittlement failures.
Best regards
Lee
J. Lee Parker, Ph.D.
JLP Consultants LLC
804 779 3389
----- Original Message -----
From: "Guy Ramsey" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, December 29, 2006 1:09 PM
Subject: Re: [TN] Questions on ENIG VS gold plating
> I didn't read your paper but my experience mirrors Werner's. It is
> very difficult to get a thin, even, always present electroplate. A two
> micro inch minimum might easily result in spots that are thick enough
> to cause brittle solder connections. A two micro inch maximum might
> easily fail to protect the nickel.
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Lee parker
> Sent: Friday, December 29, 2006 12:56 PM
> To: [log in to unmask]
> Subject: Re: [TN] Questions on ENIG VS gold plating
>
> Werner
>
> This could not be flash gold since in this process the gold thickness
is
> approximately 2 micro inches, which of course is where the name
> originated.
> The advantage over ENIG is that the porosity is greatly reduced.
>
> I am sure you will agree two micro inches of gold is not going to
cause
> embrittlement. I imagine what you have is typical plated gold with
uses a
> completely different and much more expensive chemistry.
>
> Best regards
>
> Lee
>
> J. Lee Parker, Ph.D.
> JLP Consultants LLC
> 804 779 3389
>
>
> ----- Original Message -----
> From: "Werner Engelmaier" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Friday, December 29, 2006 12:47 PM
> Subject: Re: [TN] Questions on ENIG VS gold plating
>
>
> > In a message dated 12/29/06 11:25:43, [log in to unmask] writes:
> > > Many Asian shops use what they call "flash gold"
> > > which is electro plated gold over nickel.
> > >
> > Hi Lee,
> > True enough, but 2 of my clients in China had gold-embrittlement
> > failures
> > because some of their product had too much Au on it.
> >
> > Werner
> >
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