Problem on Resonators

(cindy) #1

SMD packaged ceramic resonators from ECS are showing up electrically leaky in from one of the in/out terminals to the central ground terminal. This is causing a full inventory re-work and even a field recall of over 1,000 finished assemblies. Serious and expensive problem to say the least. It’s looking like water/solvent has gotten into a good percentage of these SMD resonators. Specifically its ECS part#ECS-SR1-4.00 . The electrical leakage appears to be affected by dc bias voltage (increasing leakage current the longer any DC bias voltage is applied for, while the leakage reduces almost to nothing if the DC bias is removed and the part is let to stand for several hours). Seems to me to behave like a sort of electrolysis type of conduction.

I’m aksing if anyone has any experience with this problem with anyway, that they can share.

The resonator is used in a typical +5V CPU oscillator circuit with about 500K feedback resistor internal to the CPU. Leakage spec for the part are > 100Meg ohms at 10volts, however I get anywhere from 4K to 4Meg ohms leakage at 2.5Volts.

I never get the problem on a freshresonator out of the tape/real package.

The problem is showing up in about 10% of boards and it may be anything from days to months of operation before the leakage level is bad enough that the CPU oscillator dies.

Short term I’ve halted production and ordered rework of all boards to switch to a different resonator from a different from a more trusted manufacturer in the more proven thru-hole package and to be done by hand so it’s outside of oven reflow, water-wash, and conformal coat process.

Looking for further ideas and info on this type of problem at this point?