To eliminate the danger of damage the device, the best way is not doing it (ultrasonic clean). So far, I have not seen in this string of e-mail that ultrasonic clean IS A Part of Standard Process Flow...(more of the fix up of someone messed up somewhere, somehow...). Try to figure out at manufacture level if what frequency of ultrasonic is acceptable at how long is difficult... not all the devices have same resonance. Even it worked at time zero, it does not mean you have a full life as per design. Damaged wire may not immediately as open or short...but necking... (we all know what that means... the wire fusing current limit may not be as per design). What ever you guys play with fire, ... I admire your bravery...
jk
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Eric CHRISTISON
Sent: Wednesday, August 17, 2005 4:33 AM
To: [log in to unmask]
Subject: Re: [TN] Ultrasonic Cleaning
If the silicon, and consequently the bond wires, are encapsulated in epoxy overmoulding it's very unlikely that you will have a problem.
If the bond wires are in air then I'd still be surprised if you had failures. Our standard package for our product has been a CLCC package with non encapsulated silicon i.e. the bond wires are unconstrained. The normal PCB cleaning method in our workshop is a 15 minute US clean and I've never heard of this causing a failure.
My only health warning for the above is that our devices are always destined for consumer products, they don't go into space or any other challenging environments.
Regards,
Eric Christison
Mechanical Engineer
Home, Personal, Communication Sector - Imaging Division
STMicroelectronics
33 Pinkhill
Edinburgh
EH12 7BF
Tel: +44 (0)131 336 6165
Fax: +44 (0)131 336 6001
>
> David Tremmel wrote:
> > Dear forum,
> >
> > I have some microBGAs which have a no-clean flux residue which must be
> > removed before they can be reballed.
> >
> > I have been doing my homework regarding USC (ultrasonic cleaning) and
> > would like opinions on whether or not putting the microBGAs in alcohol
> > and putting them through a US cleaning cycle for 1 minute would damage
> > the wirebonding.
> >
> > Most of what I see regarding USC is negative, but would only a minute
> > be damaging to the parts or does the damage occur after more time
> > (i.e. - 3 minutes, 5 minutes).
> >
> > As always, I appreciate the feedback.
> >
> >
> > David
> >
> > P.S. - Ramon, you said a 15 minute soak in alcohol would do trick, right?
> >
> >
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