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February 1997

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From:
[log in to unmask] (Jack Crawford)
Date:
Tue, 4 Feb 1997 14:30:58 -0500
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Following short note prepared by Jim Moffitt and posted by the EMPF HelpLine:

Regarding your status as an industry orphan...

It is true that certain component types (transformers, chokes, inductors,
trimpots, variable capacitors, speakers, microphones, baro-transducers,
optical encoders, etc., etc.) have been purposely excluded from
conventional solderability test described by ANSI/J-STD-002.  The
exclusion(s) are because most of the components mentioned will fail
catastrophically when subjected to the steam aging tests of ANSI/J-STD-002,
and requiring that assets be sacrificed to a destructive test does not make
good sense.

My suggestion to you would be to effect some "process development" followed
by strict "process controls" to assure that connections external to your
product are indeed solderable.

- First step would be to define a process to assure that a solderable
coating is present on external elements.  Confirm by test (test of ONLY the
solderable lugs or surfaces that is) that the solderable coating achieved
will comply with the solderability requirements for Category 3 of
ANSI/J-STD-002.  That is, demonstrate acceptable solderability after
8-hrs.(+/-15 min.) of steam aging. The test is intended for surfaces
finished with Sn or Sn/Pb coatings which will be soldered after an extended
storage (e.g. greater than 4 months) from the time of testing and/or which
see multiple thermal exposures prior to soldering.

- Second, freeze your process to assure repeatable results and provide your
customers a Certificate of Compliance to assure them that the solderable
interconnects of your product meet the requirements of ANSI/J-STD-002 for
Category 3 applications.

- Now, regarding the subject of solder connections internal to components
you build.  Most machine solder systems (whether reflow or wave) will
control the reflow temperature or solder bath temperature fairly closely
(ANSI/J-STD-001 advocates a bath temperature in the range of 230 to 290
deg. C which is controlled within +/- 5 C deg. of the set point).  The
requirement of J/STD-001 that solders be in accordance with J/STD-006
leaves you plenty of options internally.  Note that the advocacy of Sn60,
Pb36, and Sn63 (par. 4.1 of J/STD-001) are recommendations intended to
apply to solder connections external to a component; that is surfaces to
which your customer must make solder connection or solder connections which
may be subject to rework or repair by the user (purchaser of the finished
product).  If I were you I would look in J/STD-002 and select a solder
other than Sn63/Pb37 for completing connections internal to the components
you manufacture.  For
instance, Sn10/Pb90 has a liquid/plastic range of 275 to 302 deg. C;
Sn05/Pb95 has a range of 308 to 312 deg. C (narrower plastic range), as
does Sn05/Pb94/Ag01 which has a range of 296 to 301.  Any of the above
should be usable to solder connections internal to components, and may be
expected to satisfactorily survive exposure to a manufacturing process
which is operated in accordance with best industry practice and is in
control.

- I hope the above helps.  If you want/need additional definintion
regarding the intent of the J/STDS please contact David Bergman at the IPC.
If additional discussion is appropriate I can be reached at the EMPF,
317/655-3673 Ext. 121, or by return e-mail.  Regards, Jim Moffitt/EMPF>

*********
>We're pretty much one of the 'orphans' of the soldering specs.
>MIL-STD-2000A specifically states that it doesn't apply to inductive
>devices.  Most of the other specs pretty much ignore transformers,
>inductors, and similar stuff.  We have to solder internal connections that
>may, or may not, reflow during wave soldering.  Our leads have to meet
>'solderability.'
>
>Yet, our Customers (We always capitalize that word.) want us to solder to
>IPC requirements.  How?
>        Do we just 'cherry pick' what seems applicable?
>        Should there be a separate section in the spec for inductive devices?
>        Should there be a separate spec for inductive devices?
>
>How do manufacturers of other components not mentioned in the soldering
>specs solve this problem.
>
>We'd love to have a bit of feedback on the subject.
>
>Mike Middleton, engineer
>Wirebenders Inc.
>Custom Transformers and Inductors
>voice (602) 861-1856  fax (602) 870-9242
>e-mail [log in to unmask]

***ALL NEW EMPF PHONE NUMBERS***

Jack Crawford, HelpLine Coordinator
Electronics Mfg. Productivity Facility
****NEW--317.655.3688
****FAX  317-655-3699
714 N Senate Ave, Suite 100
Indianapolis IN  46202-3112
VISIT OUR HOME PAGE AT: http://www.empf.org
[log in to unmask]


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