I sympathize. I do not believe the spec applies to tinning although I do have a customer with a req. of visible clearance from the tin line to the body. However J-STD 5.4.1 says gold shall be removed from 95% of the surface to be soldered on THROUGH HOLE components with more than 2.5 micro meters of gold. It does not mention SMT parts. We have eliminated tinning on most through hole parts by checking the Manuf. data sheet for gold thickness. Most are less than 2.5 uM.  

-----Original Message-----
From: d. terstegge [mailto:[log in to unmask]]
Sent: Wednesday, November 26, 2003 9:29 AM
To: [log in to unmask]
Subject: Re: [TN] Pretinning height on fine-pitch gull wing leads


Hi Steve,

I forgot to tell that my problem is that our QA rejects parts because
the solder has wicked to far onto the leads during pretinning. It's
treated like a solder fillet that touches the body, which to my opinion
makes no sense.
It's not a problem with gold embrittlement.

Daan Terstegge
Thales Communications
Unclassified mail
Personal Website: http://www.smtinfo.net

>>> "Sauer, Steven T." <[log in to unmask]> 11/26/03 03:44pm >>>
Hi Daan,
I'll go back to the old testament (MIL-STD-2000 para 5.4.17.2 on p.
114)
that states "...Only the portion of the lead subsequently to be
soldered
need be..."
Similarly, J-STD-001 para 5.4.1 states that gold shall be removed from
at
least 95% of the to-be-soldered surface.

The elimination of gold removal prior to soldering can be  done with
objective evidence that solder embrittlement is not compromised.
Depending
on your customer and quantifying how much gold is in the final solder
connection are the bumps on that road.  Good luck.

Steve Sauer
NG Xetron
Cincinnati, OH

-----Original Message-----
From: d. terstegge
Subject: [TN] Pretinning height on fine-pitch gull wing leads


Hi Technet,

We're using some ceramic QFP's here with gold-plated leads that need
to
be pretinned prior to assembly.
Does anyone know a specification that prescribes how far the
pretinning
solder coverage for these parts may be for boards that have to meet
ANSI-J-STD-001C class 3 requirements ?

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