Paul, your wave and wash machine settings are consistent with what I am used
to seeing, and the component and PCB temperatures look pretty good too. If
you have concerns over whether or not the component is compatible with the
wash process, contact the supplier or look at a datasheet to confirm that it
is a "sealed" component. Many optic components cannot go through an aqueous
washer. Not sure if this has any relation to the "inadequate die bond".

Good Luck.

-----Original Message-----
From: Paul Truit [mailto:[log in to unmask]]
Sent: Friday, June 14, 2002 1:00 PM
To: [log in to unmask]
Subject: [TN] Optocoupler's


We are experiencing a problem related to an Optocoupler.  I wanted to
see if anyone had any ideas as to the whys.  The IC's have failed
intermittently in the field.

Specifics:
Mixed technology board.  The Opto in question is Through Hole.  It is
Hand inserted.  The board is processed using a VOC free OA flux that is
sprayed on with a spray fluxer. 2 bottom side convection pre-heaters
bring the board up to a 96°C (204°F) top side board temperature on a
conveyor that is set for 4'/min in a wave solder machine.  Wave solder
pot is at 260°C (500°F).  The maximum part lead temperature is
164°C(327°F) for 6 seconds. The board transitions into an aqueous
cleaner. The board has 6 feet to cool off before hitting the water.
This is 1.43 minutes. The water temp is set for 63°C(145°F). and the
belt speed is set for 4'/ min.  2 dryer sections dry the boards off.
Cooling of the part is a slope of -1.63°C/sec(-35°F/sec).

The optocoupler's pass a functional test.  They then fail intermittently
in the field.  Failure analysis of the IC has shown an inadequate die
bond between the Lead frame and the silicon die. 2 different date codes
have been found to have failed.

There has been a different EMS making a similar board using identical
part numbers that these boards have not failed.  What appears to be
different is we clean, they don't.  Any issues with aqueous cleaning and
Opto's? And this process causing the lead frame and die separation
issue?

--
Paul Truit, Mfg. Eng.
RBB Systems, Inc.
4265C E. Lincolnway
Wooster, OH  44691
Ph. (330) 567-2906 ext 514
Fax (330) 263-5324
Email: [log in to unmask]

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