Hi Rudy,
Yes they do. The note is as follows:
3. Manufacturing Requirements
A. Solder: Solder shall be applied over the external
finished copper on the board surface as defined below:
The fused tin lead thickness shall be no less than .0003
on the surface of the conductor and no less than .0001 in
the plated thru hole. Thickness shall be measured at the
crest of the conductor, or at the crest of the hole, as
applicable.
Hot air leveling processes shall not be used on this design
for any solder processing.
Kind regards,
-Steve Gregory-
Senior Process Engineer
LaBarge Incorporated
Tulsa, Oklahoma
(918) 459-2285
(918) 459-2350 FAX
|---------+---------------------------->
| | R Sedlak |
| | <rsedlak2000@yaho|
| | o.com> |
| | |
| | 05/17/2005 08:14 |
| | AM |
| | |
|---------+---------------------------->
>--------------------------------------------------------------------------------------------------------------|
| |
| To: TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask] |
| cc: |
| Subject: Re: [TN] SMOBC question... |
>--------------------------------------------------------------------------------------------------------------|
Steve: Do they spec out a Tin/Lead thickness, or whether the Tin/Lead
should be reflowed?
Jeff Bush and I are really talking about two different kinds of finishes.
I have seen thin Tin/Lead, non-fused. Could not fathom designing a board
with this finish. Jeff Bush is talking about Thick Tin/Lead, which is
fused, not an easy board to build, but shelf life is not an issue.
Rudy Sedlak
Stephen Gregory <[log in to unmask]> wrote:
Hi Jeffery,
The board that I'm talking about doesn't seem to be that old
design-wise. So do you think that maybe the note is just something
kind of got "boiler-plated" from earlier designs?
A description of the board is that it is a VME styled board, and
everything
on the board is SMT including headers, right angle push button switches,
etc., the only through-hole is two press-fit right angle connectors. So
the
board is never going to see wave solder.
The board is 15-layers and only .065" thick. Do you think that maybe the
reason they have the note prohibiting HASL is because they don't want
to thermally shock the board which may cause other problems?
Kind regards,
-Steve Gregory-
Senior Process Engineer
LaBarge Incorporated
Tulsa, Oklahoma
(918) 459-2285
(918) 459-2350 FAX
|---------+----------------------------->
| | Jeffrey Bush |
| | | | RCUITS.COM> |
| | Sent by: TechNet |
| | |
| | |
| | |
| | 05/17/2005 06:57 |
| | AM |
| | Please respond to |
| | TechNet E-Mail |
| | Forum; Please |
| | respond to Jeffrey|
| | Bush |
| | |
|---------+----------------------------->
>
--------------------------------------------------------------------------------------------------------------|
| |
| To: [log in to unmask] |
| cc: |
| Subject: Re: [TN] SMOBC question... |
>
--------------------------------------------------------------------------------------------------------------|
This process is called selective solderstrip and is incorporates
removing the tin/lead plating from masked areas, applying the mask then
reflowing the tin/lead plating to a solder finish. This is from a time
when HASL was new and not very robust - issues existed with the
thickness of the HASL deposit and problems were noted in assembly from
inadequate solder coating. The tin/lead reflow process offer a much
thicker solder alloy on the PCB and avoided the thickness issue. This
process worked best with hot-oil reflow as the tin/lead plating was
contaminated from photo resist development and when LPI was introduced,
mask developing.
I do not see this as an issue today with a well controlled HASL process.
Jeffrey Bush
Director, Quality Assurance and Technical Support
VERMONT CIRCUITS INCORPORATED
76 Technology Drive - POB 1890
Brattleboro, Vermont 05302
Voice: 802.257.4571.21 Fax: 802.257.0011
http://www.vtcircuits.com
-----Original Message-----
From: Stephen Gregory [mailto:[log in to unmask]]
Sent: Monday, May 16, 2005 7:50 PM
To: [log in to unmask]
Subject: [TN] SMOBC question...
This may seem like a strange ques tion, but here it is:
Can a board have a tin/lead finish on the solderable surfaces when
SMOBC is called out, and comply with a note on the drawing that
SPECIFICALLY states that HASL is not allowed?
I have a fab vendor that's telling me that it's not possible. SMOBC
without
HASL can't happen, if you want a tin/lead finish on the pads...is that
true?
I've been told that there will be some areas that will wind-up having a
tin/lead
finish beneath the soldermask, which we all know isn't a good thing
because
of the loss of adhesion of the mask when the assembly goes thru reflow
or
wave solder.
Kind regards,
-Steve Gregory-
Senior Process Engineer
LaBarge Incorporated
Tulsa, Oklahoma
(918) 459-2285
(918) 459-2350 FAX
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