Ultrasonic Cleaning Kills
Ceramic Resonatorsby Analog Services, Inc.
Ceramic resonators are often used as crystal replacements when the frequency accuracy doesn't need to be too good. We have discovered an instance in which ceramic resonators were being destroyed by ultrasonic cleaning.
The resonator frequency was 460 kHz. The resonator was part of a 460 kHz oscillator. The boards were being assembled by a contract board manufacturer. Their normal practice was to apply ultrasonic cleaning after soldering. But the yield was terrible.
At first we thought that the ceramic resonators might be defective or that the oscillator design was marginal. But tests with a large number of new resonators looked good. When the assembled boards with dead oscillators were re-worked by installing new resonators, the oscillators worked.
We contacted the assembly house and inquired about all of the steps in the manufacturing. At this point we were told of the ultrasonic cleaning. We decided to send a batch of new resonators to them to be "cleaned." Most of them came back dead.
And so the mystery was solved.
We asked them not to use ultrasonic cleaning on our boards and had no further trouble -- at least not with ceramic resonators.
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Contacting Analog Services, Inc.:
VOICE 952-927-7112 FAX 952-929-7503 E-Mail: stevea@analogservices.com