On 3/13/17 2:59 PM, Alan Melia wrote:
.....and some micro-soldering kit to attach the plated unit to the lead
frame. Our factory used homemade hot air jets, I have no idea what the
solder was prob LMP.
Lapping a single blank is difficult, one tends to get rounded edges(even
with the best machine) which affect the activity. See the video, they
are lapping several at the same time. The unplated blanks are put into a
skelton holder and measured and the most promising one proceded with.
First an evaporated contact to fix the blank to the lead frame. Then
electrode evaporation which brings the frequency down, so the final
stage evaporates electrode while measuring the mounted crystal
frequency. Allowances need to be made for the can.
I doubt most small modern firms would have a X-ray goniometer (?) The
one I saw in the 60s would never pass H&S criteria now. They probably
buy cut blanks in bulk, I think they are relatively cheap this way. My
supplier in the 90s did this.
The whole job is quite labour intensive, making a single crystal might
easily eat $1000 worth of manhours for an amateur, not even allowing for
the occasional "oops".
:-))
But you would wind up with some nice "artisanally hand crafted" crystals
to plug into a retro radio.
Definitely good for one-upsmanship at the local craft brewery.
I put this in the same sort of bucket as grinding your own telescope
mirrors - maybe something to try once.
Not all crystals are plated, either. I recall pulling crystals out of
holders and using toothpaste to raise their frequency, and a pencil to
lower it. (I will not claim high quality or stability or anything good
about it).
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