Hi Steve - Fused tin/lead has outstanding solderability shelf life but as
Franklin described, the process isn't pretty - the process is somewhat of
an art, costly, and results in slightly crowned pads. But, I have a 14
year old fused tin/lead pwb on my desk that still passes JSTD-003A testing
with flying colors.
Dave Hillman
Rockwell Collins
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Steve Gregory
<Stephen.Gregory@
LABARGE.COM> To
Sent by: TechNet [log in to unmask]
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Subject
09/20/2005 08:24 Re: [TN] Fused tin lead plating
AM versus HASL
Please respond to
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Forum
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Stephen.Gregory@L
ABARGE.COM
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
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| | "Stadem, Richard"|
| | <Richard.Stadem@G|
| | D-AIS.COM> |
| | Sent by: TechNet |
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| | 09/20/2005 07:51 |
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| | ; Please respond |
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| | Richard" |
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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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