Correct, but just to be helpful to the original enquirer: is my
understanding correct that the additions of Cu, Sb etc to basic Sn/Ag
alloys modifies the "freezing characteristics" of the basis alloy; one
of the side effects of these modifications being a finer grain
structure = smoother less lumpy surface = brighter shinier?
This is being pursued from a slightly different approach in a parallel
strand.
Mike
----- Original Message -----
From: "Jim Smith" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, August 01, 2000 6:08 PM
Subject: Re: [LF] Solder appearance
> Once again, Gordon comes through with the scientific voice of
reason.
>
> Jim Smith
> Managing Director
> Cambridge Management Sciences, Inc.
> 4285 45th St. S.
> St. Petersburg, FL 33711-4431
> Tel: (727)866-6502 ext. 21
> Fax: (727)867-7890
> eMail: [log in to unmask]
>
> "Davy, Gordon" wrote:
> >
> > A question has been raised about the appearance of solder alloys
other than
> > eutectic SnPb and whether non-shiny is acceptable. The terms
"dull" and
> > "grainy" were used. Allow me to quote from J-STD-001 (para.
9.2.4).
> >
> > There are solder alloy compositions, component lead and
terminal
> > finishes, or printed board platings and special solder processes
(e.g., slow
> > cooling with large mass PWBs) that may produce dull, matte, gray,
or grainy
> > appearing solders that are normal for the material or process
involved.
> > These solder joints are acceptable.
> >
> > The surface of a solder connection has three visual attributes:
luster,
> > texture, and contour. The first two have to do with composition
and cooling
> > rate; the third with wetting. Except for those compositions that
are at risk
> > of lifting (as discussed recently in this forum), wetting is the
primary
> > reliability concern.
> >
> > Gordon Davy
> > Northrop Grumman ESSS
> > Baltimore, MD
> > [log in to unmask]
> > 410-993-7399
> >
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