We build the raw boards and assemble the same - all have immersion tin
but we have the following rules: 1) in our opinion immersion tin is good
for one thermal pass - solderability is not good for two passes 2) our
parts see as few heat cycles as possible before assembly ( we even
silkscreen the nomenclature before tin)
There should be no solderability issue on the tin versus tin lead - if
there is then the tin is contaminated or is heavily oxidized. To test
for the oxidation clean a few pads with a clean pencil eraser - tin
should be smooth and white in appearance - then try soldering.
Good Luck.
Steve Kelly
PFC Flexible Circuits Limited
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Gaby Bogdan
Sent: Monday, November 25, 2002 3:44 PM
To: [log in to unmask]
Subject: Re: [TN] Immersion Tin
We tried several boards with immersion tin from different vendors.
Some of them had very good solderability, others not.The soldering
conditions were the same as for hot air leveling.
We tried to see where the problem was, and saw that the problem occured
mostly on boards which were plugged BEFORE the mmersion tin plating,
only on
one side. The same problem was seen on immersion silver boards which
were
plugged before the final finish, and on these we run a contamination
test
which they failed.
IMHO , if the boards are new, it could be a contamination issue due to
contaminants in the vias not being washed away properly because of the
plugging on one side. The interesting point was that the problem was
more
visible after the second reflow.
Maybe we ca shed some light on this?
Gaby
----- Original Message -----
From: "Yannick Brisson" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, November 25, 2002 3:03 PM
Subject: [TN] Immersion Tin
> Hi,
>
> I made a board wich I plated with immersion Tin, I tought it should
be
the
> same result as we had with tin lead but we ran into a weird problem.
We
use
> a 63/37 no clean paste and on the Board with Immersion Tin the solder
just
> make a ball ON the pad...we ran the same profile with a board Tin-Lead
and
> we get almost a perfect solder joint. Because it's immersion tin
should
we
> put our temperature higher?
>
> We try to solder with a iron and the paste can hardly wet all the
pad
the
> fisrt time..if we do it a first time, cleand the pad and do it again
it's
> more easy. If someone have work with it can give me some trick I
would
> appreciate.
>
> Thanks You
>
> Yannick Brisson
> ============================
> Technicien Ingénierie de Production
> Technician Production ingineering
> M2S Électronique
> 2855, Rue de Celles
> Québec, Québec
> G2C 1K7
> Téléphone: (418) 842-1312 Ext: 264
> Télécopie: (418) 842-0123
> [log in to unmask]
> ============================
>
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