Dave,

If there were any cavity packages, such as mechanical relays, HYBRIDS,
CPU's, crystals, etc on the board they could indeed be susceptible to
possible mechanical damage caused by the ultrasonics.  I have observed the
results of individuals placing SEALED hybrids [cavity style packages] into
ultrasonic cleaners with devastating results to the wire bonds.  Placing the
same hybrids into the ultrasonic cleaner in an un-sealed state did not
affect the wire bonds [but prove out one's own process to be sure].

Conversely, if the devices are plastic encapsulated PEMs, with no internal
cavities, they are essentially immune from any reasonable ultrasonic
exposure that I can imagine.

   If there are cavities - tread with caution.  
   No cavity, total encapsulation - typically safe!

My 10 cents

Steve Creswick


From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Wednesday, October 12, 2011 8:14 AM
To: TechNet E-Mail Forum; Amol Kane
Cc: [log in to unmask]
Subject: Re: [TN] Wire soldering question - Utrasonics discussion


Hi Amol - you can call it a myth or just old tribal knowledge but for many
years there was (and still is in some segments) the idea that ultrasonics -
either soldering or cleaning - will damage the die or the wirebonds in
components. There are a number of good industry publish investigations that
show ultrasonics can be applied for in both the cleaning and soldering
applications safely without causing component damage provided you do
sufficient process qualification. I am not a fan of ultrasonic soldering as
I can ultrasonically solder a toothpick - the solder sticks mechanically and
not because I made a metallurgical interface. But, ultrasonic soldering is a
viable process provided attention is paid to making metallurgically sound
solder joints. Ultrasonics have wide application in cleaning processes.
Other TechNetters can provide better information on that aspect than I.

Dave Hillman
Rockwell Collins
[log in to unmask]




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