From a hybrid manufacturing standpoint we found that if the wirebonds are
surrounded by the ultrasonic cleaning fluid there is no problem.

However, if there is a cavity - there will be a problem.

Put another way - ultrasonic cleaning of sealed units (nothing but dry
nitrogen around the wires) was an open invitation for non-functional units.
Cleaning of un-sealed units was not a problem.

Most plastic encapsulated devices have no (intentional) air pockets around
the wires, therefore, I would expect them to be okay.  If you have sealed
metal can type packages I would stay away from the ultrasonics.

Steven Creswick - Gentex Corporation

-----Original Message-----
From: Dieselberg, Ron [mailto:[log in to unmask]]
Sent: Wednesday, January 02, 2002 10:26 AM
To: [log in to unmask]
Subject: Re: [TN] Ultrasonic Cleaning



I had only one experience, about 15 years ago. The assembly tested OK before
cleaning in an ultrasonic tank. Afterwards it did not work. Failure analysis
folks said almost all of the wire bonds in the three transistors were
damaged.. Maybe someone has had good luck, but not me. That was the first
and last on anything but a component-less board!

Ron Dieselberg
Trainer/Auditor
CMC ELECTRONICS
CINCINNATI
[log in to unmask]

        BM__MailData-----Original Message-----
From:   Vinit Verma [ mailto:[log in to unmask]
<mailto:[log in to unmask]> ]
Sent:   Thursday, December 27, 2001 5:48 AM
To:     [log in to unmask]
Subject:        [TN] Ultrasonic Cleaning

        Hi Technetters,

        I am presently evaluating post reflow PCB cleaning machines, both
aqueous
and ultrasonic. I have a concern regarding ultrasonic cleaning. Read
somewhere that the ultrasonic frequencies can have an effect on the wire
bonds inside the packaging. Does anyone have any idea of this?

        Thanks in anticipation.

        Regards
Vinit Verma


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