[SI-LIST] Re: Immersion gold
- From: "Moran, Brian P" <brian.p.moran@xxxxxxxxx>
- To: <leeritchey@xxxxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>,"Martin Euredjian" <martin@xxxxxxxxxxxxxx>
- Date: Mon, 14 Apr 2003 17:44:47 -0700
Martin,
Folks are always looking for ways to improve the coplanarity or =
smoothness of SMT pads as we go to smaller and smaller geometries. You =
have to coat the exposed pads after plating and the soldermask is =
applied with something to keep the exposed pads from oxidizing, and for =
the solderpaste to adhere to. The cheap and dirty approach is to dip the =
board in tin/lead solder and then blow off all the excess. Of course =
this can leave puddles and rough surfaces. So various alternatives have =
been attempted over the years to coat the bare platting pad surface. I =
forget the names of some of the coatings people have tried to make work =
with mixed results. The last time I was involved in such discussions =
people were looking at immersion gold, which is expensive, or immersion =
tin, which was discussed as a lower cost alternative to immersion gold. =
Not sure it ever caught on or what the trade offs were. In either case =
case the object is to prevent the pads from oxidizing while maintaining =
optimal flatness.=20
Brian P. Moran
Signal Integrity Engineer
Intel Corporation
brian.p.moran@xxxxxxxxx
-----Original Message-----
From: Lee Ritchey [mailto:leeritchey@xxxxxxxxxxxxx]
Sent: Sunday, April 13, 2003 1:26 PM
To: si-list@xxxxxxxxxxxxx; Martin Euredjian
Subject: [SI-LIST] Re: Immersion gold
Martin,
The proper term for this kind of PCB finish is immersion gold over
electroless nickel (ENIG). It is a "noncorrosive" finish applied after
solder mask has been applied over bare copper.
It is a way to maintain solderability of the pads and holes. White =
nickel
is not a substitute for this finish.
The ENIG process can go unstable and produce a black pad failure. A =
safer
finish is electroplated gold over electroplated nickel.
Lee
Lee Ritchey
leeritchey@xxxxxxxxxxxxx
Why Wait? Move to EarthLink.
> [Original Message]
> From: Martin Euredjian <martin@xxxxxxxxxxxxxx>
> To: <si-list@xxxxxxxxxxxxx>
> Date: 4/12/2003 12:06:46 PM
> Subject: [SI-LIST] Immersion gold
>
>
> Can someone explain the primary need/benefits of the immersion gold
process?
> Some have told me that "white nickel" is comparable in certain =
aspects.
>
> Thanks,
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Martin Euredjian
> eCinema Systems, Inc.
> voice: 661-305-9320
> fax: 661-775-4876
> martin@xxxxxxxxxxxxxx
> www.ecinemasys.com
>
>
>
>
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