Ken,
If you have access to some small grinding tools, i.e. a variable speed
Dremel tool or better yet, cross-sectioning equipment, carefully grind
down three of the four sides of the perimeter of the lid. If you know
which end of the package the crystal is in, leave that edge alone;
grind the other three. Once you just start to break through, use a new
X-acto, with minimum penetration of the blade into the case, to pry
and slice open the unit. Fold back the lid along the unground edge,
and use it to hold the part. If you watch your grinding speed, and
don't use water, you won't introduce any foreign matter into the
package, or damage the crystal.
Once you're inside, you can examine the crystal under a normal 30X
microscope and check for cracks and chips in the crystal. Sometimes,
the conductive epoxy used to cement them to the spring mounts, fills
the mounts - making them solid, which makes the part very vulnerable
to shock damage. Sometimes they're built just fine and as Tuan says
below, they're just too roughly handled. I've also seen solder shorts,
unsoldered pins, etc., which were manufacturing defects.
This delidding technique works well; I've done it many times. Try it
out first on a few parts that you don't care much about before going
after one you want to seriously investigate. Careful of the sharp
edges on the lid & package.
Bruce Tostevin
Benchmark Electronics
Hudson, NH
______________________________ Reply Separator _________________________________
Subject: Re: [TN] Crystals/Oscillators failure
Author: Tuan300859 <[log in to unmask]> at 0UTG0ING
Date: 5/11/98 6:30 PM
Ken,
I have experienced this failure before. The root cause is definitely due to
handling. The crystal/oscillator is a fragile component. It can get damaged
even in tube. The crystal will crack when drop from a distance of 5 inches
to a hard surface. My recommendation is to transport these crystal parts in
a foam pads , not in tube and definitely not in bag. And lastly, all
operators from shipping, stockroom, hand load, and PC need to be awared of
handling issue of the crystals/oscillators.
I hope this helps!
Tuan
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