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Quartz crystals

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41–50 of 60 posts

Re: Quartz crystals

#41

The article is a nostalgic reminder of when I was first interested in electronics and got interested in quartz resonators for projects. Grinding down old war surplus FT243-style crystals and other types so as to resonate at frequencies I needed was a common practice with hobbyists back then. I used many similar techniques to the same end of removing quartz which raised its frequency. Grinding materials included abras…

Heavens, that should be AT cut not XT. What on earth was I thinking of?

Some of you guys should have picked that up. ;-)

Re: Quartz crystals

#42

Earlier quoted context omitted.

How are people sticking stuff to quartz? I know less than nothing, but the pieces of quartz you find in rock don't look like they'd take a solder bond. I'd assumed that with piezo crystals etc there was a mechanical connection rather than an electrode bonded to the crystal? But if you can add solder presumably there is some kind of molecular connection with the metal?

Electrodes are deposited on the crystal in vacuum, e.g. by metal evaporation or sputtering, in the same way as they are deposited on the semiconductor crystals used to make transistors or integrated circuits. The electrodes may consist of multiple layers, a base layer that adheres strongly to quartz and a top layer that is solderable, e.g. made of nickel or silver. The pins of the package that hosts the crystal reson…

Thanks, that's fascinating. I imagine they use a mask and large spread? Or a stepper?

Fun video of 'metallization' on a coarser scale! https://www.youtube.com/watch?v=e-QcseGvU5o

Re: Quartz crystals

#43

Earlier quoted context omitted.

Wow! I'm working on something much, _much_ smaller than that! https://blog.afandian.com/tags/harmonium/

You are going to be leveling up in a whole bunch of skills.

Yes! Most important being calibrating what I should and shouldn't attempt yet.

Re: Quartz crystals

#44

Earlier quoted context omitted.

> BTW, the mentioning of HF will likely horrify chem-phobic readers I would not say I am chem-phobic, but yes indeed that stood out. HF is nasty stuff, and yes requires some care I suspect. The other details are fascinating, though - the intersection of mechanical, crystallographic, and RF (?) properties of a crystal that you can adjust through abrasives and selection of the cut.

Working with HF was extremely difficult before WWII, but it has become much easier after the invention of Teflon. Teflon is not affected by HF, so if you use only vessels of Teflon to hold the HF solution and tweezers made of Teflon for handling anything that you submerge in the solution of HF, it works fine. Besides using Teflon for anything that is in contact with the HF solution, you must do all work under a hood…

In my case the HF came in small black plastic cylindrical bottles of 50 perhaps 75 ml (could have been 100ml but that seems a bit big). Back then they were commonly available at local hardware stores.

The bottle was flat on top from which protruded its 'neck' — more a threaded spigot of perhaps 8mm in dia. and about 10 to 12mm high with a small hole in it for the HF to exit. A red plastic cap screwed onto the thread to seal the bottle.

If the bottle were ever knocked over (which it never was) very little would have spilled out (picture the threaded top and screw cap on the small bottles of Tabasco sauce and you've pretty much got it).

So the HF only came out in drops which were poured directly into a small plastic beaker of about 50ml containing about 20ml of H2O and the crystal. The crystal rested on some finely corrugated plastic and not lying flat on the bottom to ensure the etching process was reasonably uniform.

The operation was done outside and if I recall the HF was neutralised with NaOH.

The soln was very dilute and the process could easily take over an hour and was used mainly to finish off crystals that had already been through the abrasive process.

I don't know what type of plastic the bottle was made of but it was jet black.

Re: Quartz crystals

#45
post #32

The article is a nostalgic reminder of when I was first interested in electronics and got interested in quartz resonators for projects. Grinding down old war surplus FT243-style crystals and other types so as to resonate at frequencies I needed was a common practice with hobbyists back then. I used many similar techniques to the same end of removing quartz which raised its frequency. Grinding materials included abras…

This awesome. Could you perhaps remember the title of the book you lost?

I wish I could but it's s long while ago. More precisely the book wasn't lost but loaned to someone who never returned it and I lost track of him.

The book was a harback with a bright yellow dust jacket and I think its title was printed in red. It was about 300 pages and was no lightweight, full of resonance equations, tables etc.—the sort of book you'd find in the lab of a commercial crystal manufacturer.

Can't remember the price but it was damned expensive. At times over the years I've had need to refer to it and I still get a bit peeved when I think about it.

Re: Quartz crystals

#46

The article is a nostalgic reminder of when I was first interested in electronics and got interested in quartz resonators for projects. Grinding down old war surplus FT243-style crystals and other types so as to resonate at frequencies I needed was a common practice with hobbyists back then. I used many similar techniques to the same end of removing quartz which raised its frequency. Grinding materials included abras…

So is this art of selecting right crystals is applicable for synthetic crystals also or these can be grown perfect each time to specifications?

I can't recall exactly but I'm pretty certain most crystal are synthetic these days, at least so for the common cuts. I'd imagine most watch quartz would be synthetic but that's only a guess.

Re: Quartz crystals

#47

Earlier quoted context omitted.

That sinking feeling of knowing you've ground off just a bit too much...

I've just spent the weekend tuning brass reeds from an organ. It sounds like a very similar process, except you can grind both ends of the tongue to raise and lower frequency. And, if you're sneaky, you can add solder.

Funny you should mention that another hobby of mine was rescuing old harmoniums and making them playable again—you know, fixing and replacing reeds, renewing bug-eaten felt, sealing rat holes in the bellows, etc.

I grant you it's not in the same league as voicing a diapason though. :-)

I reckon adjusting and tweaking things goes with the territory. I'm pretty much at home tweaking crystals, fixing reeds, aligning IF stages in radio and TV equipment, there's much of a sameness in the way one tackles all of them.

BTW, I've actually repaired reeds by soldering them. Not a good fix though as the solder can fatigue with use. Throws out equal temperament a bit too but most can't hear the difference.

Re: Quartz crystals

#48
post #32

Earlier quoted context omitted.

This awesome. Could you perhaps remember the title of the book you lost?

I wish I could but it's s long while ago. More precisely the book wasn't lost but loaned to someone who never returned it and I lost track of him. The book was a harback with a bright yellow dust jacket and I think its title was printed in red. It was about 300 pages and was no lightweight, full of resonance equations, tables etc.—the sort of book you'd find in the lab of a commercial crystal manufacturer. Can't reme…

ok, could it be: Crystal Oscillator Design and Temperature Compensation :Marvin E. Frerking (1978). or perhaps Introduction to Quartz Crystal Unit Design : Virgil E. Bottom (1982)?

Re: Quartz crystals

#49
post #48

Earlier quoted context omitted.

I wish I could but it's s long while ago. More precisely the book wasn't lost but loaned to someone who never returned it and I lost track of him. The book was a harback with a bright yellow dust jacket and I think its title was printed in red. It was about 300 pages and was no lightweight, full of resonance equations, tables etc.—the sort of book you'd find in the lab of a commercial crystal manufacturer. Can't reme…

ok, could it be: Crystal Oscillator Design and Temperature Compensation :Marvin E. Frerking (1978). or perhaps Introduction to Quartz Crystal Unit Design : Virgil E. Bottom (1982)?

Could well be either, it was around the late 70s early 80s when the book went walkabout.

Damn nuisance my memory isn't better. However, I'd recognize it instantly if I saw it. Must check those references out. There may be enough info online for me to figure it out. Thanks.

Re: Quartz crystals

#50
post #48

Earlier quoted context omitted.

ok, could it be: Crystal Oscillator Design and Temperature Compensation :Marvin E. Frerking (1978). or perhaps Introduction to Quartz Crystal Unit Design : Virgil E. Bottom (1982)?

Could well be either, it was around the late 70s early 80s when the book went walkabout. Damn nuisance my memory isn't better. However, I'd recognize it instantly if I saw it. Must check those references out. There may be enough info online for me to figure it out. Thanks.

Thank you!
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