RE: [TN] Ultrasonic CleaningSteven
The specific component types that were concerns for this cleaning method per
the DoD studies were TO package IC's (not used much these days). Later
testing by the EMPF looked at encapsulated components with better results,
should still be available for review but I don't believe that the DoD
studies are.

Mel Parrish
  -----Original Message-----
  From: TechNet [mailto:[log in to unmask]]On Behalf Of Creswick, Steven
  Sent: Wednesday, January 02, 2002 8:17 AM
  To: [log in to unmask]
  Subject: Re: [TN] Ultrasonic Cleaning


  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]

        -----Original Message-----
        From:   Vinit Verma [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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