[time-nuts] build your own crystals.

[Bob kb8tq]

HI

> On Feb 18, 2021, at 8:06 PM, Lux, Jim <jim at luxfamily.com> wrote:
> 
> On 2/18/21 4:38 PM, Bob kb8tq wrote:
>> Hi
>> 
>> Ok
>> 
>>> On Feb 18, 2021, at 6:40 PM, Magnus Danielson <magnus at rubidium.se> wrote:
>>> 
>>> Hi,
>>> 
>>> A lot of fascinating steps. It would be real fun if one would do a
>>> coarse in which one would actually build a handful of crystals oneself,
>>> to learn the basics, and measure them up. It would be a fun
>>> summer-coarse to do.
>> A crystal plant isn’t going to let you in to do this. The risk of breaking gear /
>> stopping production isn’t going to work for them.
>> 
>> So what do you need to come up with for the group?:
>> 
>> You need some quartz bars. Forget about trying to grow them yourself unless
>> you have the ability to deal with battleship guns ….
>> 
>> Next you will need an x-ray setup for the angles you wish to deal with. For AT
>> cuts that may not be to bad. For SC’s … good luck at < $500K.
>> 
>> For a summer camp sort of setup, go with a diamond saw, dice up the blank slowly,
>> but with cheap gear.
>> 
>> Now you need lapping equipment. Normally this is a device made from
>> cast iron and with “couple of meters in each direction” sort of dimensions.
>> Not much of an alternative out there so a fairly unique thing to find.
>> 
>> Rounding the blanks can be done a couple of ways, a fairly normal lathe
>> might be adapted to do this.
>> 
>> For the contour process, I’d just go with drum processing. I’ll take you a
>> couple of months, but there isn’t a lot of fancy gear involved.
>> 
>> Chemical etch is easy, but you need to do it.
>> (note that “polish” got left out …. )
>> 
>> Now you need to put the base plate on the blank after cleaning it. It’s
>> a thin film deposition process. If you are set up to make semiconductor
>> wafers, you likely have the gear to do it. Same sort of deal, masks,
>> mounting fixtures, thickness monitoring, gold evaporation at very
>> high vacuum.
>> 
>> Next up drop it in a solder seal base and solder it into an enclosure.
>> (note that finish plate got left out).
>> 
>> You now have a working device.
>> 
>> Bob
>> 
> If you want RF resonators to build in a "simple lab", it's probably easier to do SAW devices on a blank you buy. Then it's a single layer of aluminum that you photo etch.  Not hugely different than PC boards or a thick film hybrid.
> 
> Getting small feature sizes might be a challenge - when we did it where i used to work, they did photo reduction onto a photoresist covered substrate. I wonder if someone has a laser rig that could programmed to "draw" the pattern on the resist at the right scale.  As I recall, 50 MHz has a wavelength of about 60 microns, and your transducer fingers are half wavelength apart.  You're probably not going to scribe those with an X-acto knife by hand. But it's not particularly exotic.
> 
> We bought the substrates already plated, but that is something you can conceivably do in a small lab - vacuum system and evaporation rig.
> 
> Then you have to bond wires onto the aluminum. But that's a "available from surplus" thing - and if you are equipped for doing hybrids you're all set.

You can (and companies often do) buy blanks “in the round”. They already are 
properly oriented (x-rayed). They have the basic shaping already done. 

You still need to do the final shaping / polishing / cleaning / plating etc. 

Getting the metal to properly attach to quartz is a bit exciting. More so with
some metals (gold) than with others (chrome). One often sees a very thing 
under layer of chrome on gold plated crystals. 

Bob

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