Why DRO stops to oscillite until super glue is dry?
Why it behaves different while glue is not dry? Also if using very small amount of glue, DRO performance still differs from unglued one (same position). Glue dielectric constant changes while drying reaction?
My guess is that it's the high dielectric loss of the solvent that lowers the total resonator Q.
Maybe. But here is interesting thing: if i remove resonator and put it again (above old dry glue, maybe some 0.05mm height), it works better.
Yes, the stand-off height and material (loss tangent) change total Q factor of the resonator - directly, but also indirectly by changing the coupling.
Super glue is usually a cyanoacrylate (CA). As CA dries the solvent evaporates and leaves behind a crosslinked polymer, so the dry and wet states will have different volume and dielectric properties.
Slightly off topic but has anyone noticed the @&%!* DRO ALWAYS sticks to your finger when trying to position it?
Brian.
I guess the cyanoacrylate monomer diffuses either into the porous DRO ceramics or the PCB.
I believe that "super glue" should be strictly avoided when bonding electronic parts. Better use epoxy resin (araldite).
You have to be careful with the dielectric properties (loss tangent).
This is what Trans-Tech recommends:
http://www.trans-techinc.com/documen...rs_202824A.pdf
Why your DRO is so sensitive against small fraction of movement of the DR ?
I understand that the frquency may shift but if it stops to oscillate, there should be a very critical design parameters.
It may also stop to oscillate In any different corner cases ( temp.,material lot,mfg. tolerances etc)
It stops to oscillate while glue is in liquid state. Few minutes later it turns on.
The problem is, after tuning DR position i need to pick it up with tweezers to add small drop of glue. When i put DR on this drop of glue, position is not the same as before, so i hope that oscillation still exists (to make small position adjustments). But super glue catches fast, and there is no oscillation until it dry. I tried to put glue while DR is on the board surface, but it seems that glue do not penetrate well to thin gap between PCB and DR.
So with very tiny drop of glue it works, but catches too fast to the PCB, so i can't adjust it's position.
With big drop of superglue it dries slower, but it is useless, as oscillations disappear, so there is no any phase noise / amplitude information available with adjusting position. After a while huge drop of glue becomes solid and oscillation comes back.
Hi,
it seems the glue contaminates part of the oscillator.
And it seems you adjust your oscillator and then fix the "frequency" with the glue.
Take care, because the glue may create thermal drift to your oscillator frequency (because dielectric constant of the super glue drifts with temperature). So avoid to put the glue directely on active oscillator (conductive) components like traces, pins, capacitors, resistors.
To be sure you could make some thermal drift tests on circuits with and without glue.
Before the tests make sure the glue is fully cured. I′d say at least after a day. The exposure to some higher temperature should improve curing. Keep in mind that super glue is activated with the humidity on the surface and air. So it needs a little humidity to cure properly.
Klaus