hi,
there is no tight control over the alloy composition of the fused tin
lead finish. what you plate is what you get. on the other hand hasl
gives you a eutectic mixture if that's what you want, and it probably
is.
phil
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Tuesday, September 20, 2005 6:25 AM
To: [log in to unmask]
Subject: Re: [TN] Fused tin lead plating versus HASL
Hi Richard!
We have a few boards that call out that too. From my point of view, as
far as appearance, it looks the same as HASL.
I've tried to think why Fused tin/lead would be called out instead of
HASL, and my only guess is that someone didn't want the boards to be
themally shocked by the HASL process. I might also add these were on
61-20 layer VME cards where everything was SMT, and the only PTH was
press-fit connectors...so the boards didn't even see wave solder.
Kind regards,
-Steve Gregory-
Senior Process Engineer
LaBarge Incorporated
Tulsa, Oklahoma
(918) 459-2285
(918) 459-2350 FAX
|---------+---------------------------->
| | "Stadem, Richard"|
| | <Richard.Stadem@G|
| | D-AIS.COM> |
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| | 09/20/2005 07:51 |
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>-----------------------------------------------------------------------
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| To: [log in to unmask]@SMTP@Exchange
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| cc: (bcc: Stephen R Gregory/LABARGE)
|
| Subject: [TN] Fused tin lead plating versus HASL
|
>-----------------------------------------------------------------------
---------------------------------------|
Hi, folks
I have a pwb fab drawing that calls out fused tin-lead plating or solder
coating. I know that the solder coating is HASL, but what is fused
tin/lead? My understanding is that it is a tin/lead coating that is
applied to the bare pwb using a reflow oven process. Does this provide a
flat surface of tin/lead? If my only choice of finish is tin/lead, which
process is better in terms of flatness and solderability? I have a
fine-pitch BGA that is going to be assembled on this pwb.
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