Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

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Aqueous Board Cleaning

Dave

#24531

Aqueous Board Cleaning | 19 May, 2003

Hello.

We have a low profile LCC on a board. The clearance is ~ 2mils after reflow. Cleaning away residual flux with an ultrasonic 50C water cleaner caused some LCC and 0201 components to loosen. Should we stay away from the ultrasonic cleaner?

Thanks.

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#24535

Aqueous Board Cleaning | 20 May, 2003

First, it is very difficult to properly clean under devices like yours.

Second, your ultrasonic cleaner should not be damaging or loosening encapsulated components. It sounds like: * Cleaner is not of the proper type for cleaning electrics. * Cleaner amplitude or sweep are not adjusted properly. * Components were not properly soldered.

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Mike Konrad

#24540

Aqueous Board Cleaning | 20 May, 2003

This probably a reflow issue, not a cleaning issue. Although ultrasonic cleaners are not normally used in post-reflow applications (fear of internal wire bond damage), I have never heard of broken solder joints caused by an ultrasonic cleaning system. Most ultrasonic cleaners used in this industry are rated at 40 kHz, a relatively safe frequency. I would suspect there is a problem with you reflow process.

As far as cleaning is concerned, high pressure spray-in-air systems are normally effective. A chemical may be added to the wash water to lower the surface tension and increase under component penetration (impingement).

Mike konrad@aqueoustech.com www.aqueoustech.com

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iman

#24588

Aqueous Board Cleaning | 24 May, 2003

Our engineers did a study on our medical product with 1mils standoff height, and one issue was 100% of the boards that underwent ultrasonic failed due to failure of the package wirebonding. Poor reflow control would be one area to review in any event, as "broken solder joint" as root cause is rather awkward from a metallurgy perspective.

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PCB Cleaning