Hi Ron,
That's exactly the spec where my QA refers to, but I doubt if it is
correct to treat solder on a pretinned lead (which is only there to
remove the gold) as if it's the same thing as a solder joint that's too
thick. With all standard QFP's (or SOIC's or a zillion of other parts)
the solderplating covers 100% of the lead, so why would that be ok and
would the same be unacceptable when originally there was a goldplating ?
Daan
>>> "Dieselberg, Ron" <[log in to unmask]> 11/26/03 04:25pm >>>
Daan, J-Std page 27, Table 9-8, Class 3, note 4, "Solder fillet may
extend through the top bend. Solder shall not touch package body or end
seal, except for low profile SMD devices, e.g. SOICs and SOTS. Solder
should not extend under the body of low profile surface mount components
whose leads are made of Alloy 42 or similar metals."
Ron Dieselberg
Trainer
CMC Electronics Cincinnati
[log in to unmask]
-----Original Message-----
From: d. terstegge [mailto:[log in to unmask]]
Sent: Wednesday, November 26, 2003 8:52 AM
To: [log in to unmask]
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. Some parts are supplied with
pretinning
by the component manufacturer, for other types we need to do it
ourselves.
Most of the times the pretinning-solder reaches somewhere between the
lower and upper bend of the gull wing leads, but at other times solder
coverage extends to where the lead goes into the body.
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 ?
Best regards,
Daan Terstegge
Thales Communications
Unclassified mail
Personal Website: http://www.smtinfo.net
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