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Re: Crystal holder vs complete head

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  • Preston
    Hi Ken, I ve got a call into thier tech dept...fellow is in a meeting and will call me back. I did find this about the holders on thier site... In currently
    Message 1 of 18 , Feb 1, 2006
      Hi Ken, I've got a call into thier tech dept...fellow is in a meeting
      and will call me back.

      I did find this about the holders on thier site...


      "In currently available sensor head designs, the crystal rests in the
      "crystal holder" a metal cap with a hole drilled through the center of
      the cap. The holder serves as one half of the electrical circuit that
      causes the crystal to vibrate. This hole allows the evaporating film
      to coat a circular region of approximately 0.3" diameter (7.6 mm) on
      the crystal face. The crystal is held in place in the holder by a
      spring. In some models, the spring is located around the inside of the
      holder and presses against the crystal edge. In other designs, a
      "ceramic retainer" with a gold-coated spring in the center presses
      against the outer back edge of the crystal.

      In both designs, the crystal holder is inserted into the sensor head
      (a metal block), where a second gold coated spring presses against the
      back of the crystal or retainer to complete the crystal electrical
      circuit. The head often contains another spring for holding the
      crystal holder in place and providing electrical contact between the
      holder and the head."

      I can gold plate some small springs to hold the crystals in place.

      The Fil Tech site has a very good Technical Notes area!!!

      Also, they have recoated packs of 10 crystals for $32 vs $48-55...

      I should think that these would be ok for our testing purposes...

      They say this about Gold Crystals:

      "Gold is the mostly widely known crystal electrode material. It offers
      low contact resistance, very high chemical stability, and is easy to
      deposit. Typically, gold crystals are used for low-stress metal
      depositions such as gold, silver, and/or copper. With gold it is
      possible to get frequency shifts of up to 1 Megahertz without adverse
      effects. However, gold electrodes are relatively inflexible,
      transmitting stresses from deposited films to the underlying quartz.
      Transmitted stresses may result in frequency jumps and crystal
      instability."

      However they really promote the Alloy crystals and say:

      "Alloy, an aluminum-silver composition is the best electrode for
      high-stress material depositions including; silicon monoxide, silicon
      dioxide, magnesium fluroride, and titatium dioxide. Deposited
      high-stress materials often cause erratic crystal performance produced
      by high tensile or compressive stresses. These stresses cause bending
      of the quartz and subsequent frequency shifts.

      Alloy dissipates the stress of the deposited film by plastic yielding
      or flowing. Long before the compressive or tensile forces cause the
      crystal to bend the electrode will "give," dissipating the stress.
      This results in a much more stable crystal with a longer period of
      steady, jump-free oscillation. Laboratory experiments have shown as
      much as a 400% increase in crystal life with deposited silicon dioxide
      on alloy."


      >
      > Hmmm... better not put any glass in there then! I don't think this
      > applies to resistance evaporation methods.

      Glass won't hurt anything and other metals only poison the anode if
      using an Ion Assist on the lenses...

      I think that I can build a crystal holder based on the information on
      thier site and other that I have found...

      The down side to the Alloy Cryatals are they are Only 0.155" diameter!!!

      I'll let you all know what the Tech says...

      Regards,

      Preston
    • Preston
      Hi Ken, I spoke to the Tech Rep in great length...ordered the Crystal Holder and 10 Alloy Crystals...They are 0.550 diameter and he said that they will work
      Message 2 of 18 , Feb 1, 2006
        Hi Ken, I spoke to the Tech Rep in great length...ordered the Crystal
        Holder and 10 Alloy Crystals...They are 0.550" diameter and he said
        that they will work Much better for what we are trying to accomplish
        and are much more robust.

        The parts should be here on Friday or Monday and then I'll look at
        copying the holder and making a head to hold everything...

        He is also sending a number of papers regarding MgF coating on glass
        substrates that he thought would be of help.

        Regards,

        Preston
      • Ken Hunter
        ... Yeah, I ve read all of their tech notes. The springs are really round disks of spring bronze (brass?) that are cut with radial cuts and are then shaped so
        Message 3 of 18 , Feb 1, 2006
          --- In VacuumX@yahoogroups.com, "Preston" <thecount@...> wrote:
          >
          > Hi Ken, I've got a call into thier tech dept...fellow is in a meeting
          > and will call me back.
          >
          > I did find this about the holders on thier site...
          >
          >
          > "In currently available sensor head designs, the crystal rests in the
          > "crystal holder"



          Yeah, I've read all of their tech notes. The springs are really round
          disks of spring bronze (brass?) that are cut with radial cuts and are
          then shaped so that the crystal rides in the cup and is contacted
          around the edge of the crystal by the spring thingy... The other
          spring is just an electrical contact to the spring that holds the
          crystal in the cup. It can be replaced by an electrical connection
          (the pin in my arrangement).

          If you look at the photo's I put in the groups files section, you will
          see that I was using an RF (SO-239) type connector there and I
          machined a disk which was recessed in the center to contact the
          circumference of the crystal. This disk also has a pin that plugs into
          the connector making the connection. The screw on lid makes contact
          with the face of the crystal and makes the "ground" connection for the
          crystal circuit. My scheme works very well as long as you have the
          proper pressure on the crystal. As the photo's show, it's easy to
          break a crystal. If I had some phosphor bronze material or some brass
          shim stock, I'm sure that I can make a crystal holder/crystal head
          that will work satisfactorily but I can't compete with $75.00 yet.
          I'm also nearly sure that your crystal head/holder will cost you the
          full $400.00 by the time you get it all together. The $75.00 is mainly
          to replace the formed spring that they say will eventually lose
          it's "springiness"...

          Anyway, If I could find one on eBay for $75.00 I'd buy it and be done
          with it... so far that's not happened. I hope that you can come up
          with something... I have plenty of ideas but not the time or money to
          chase down a solution at this time.

          By the way, the photo's are of a BNC to UHF adapter (large center
          pin)... I'm currently not working on the MK-II. A SMA to Type "N" but
          the idea is the same in that I'm using a screw-on connector cap to
          hold the crystal. If you need to get some of these connectors, let me
          know. I have a few but the screw-on caps are kinda spendy at $15.00
          plus shipping.

          Ken Hunter
        • Ken Hunter
          ... Cool... Take some good hi-rez photo s and post them so we can see what you are starting out with. I might be able to help in some fashion too. Ken Hunter
          Message 4 of 18 , Feb 1, 2006
            --- In VacuumX@yahoogroups.com, "Preston" <thecount@...> wrote:
            >
            > Hi Ken, I spoke to the Tech Rep in great length...ordered the Crystal
            > Holder and 10 Alloy Crystals...They are 0.550" diameter and he said
            > that they will work Much better for what we are trying to accomplish
            > and are much more robust.
            >
            > The parts should be here on Friday or Monday and then I'll look at
            > copying the holder and making a head to hold everything...
            >
            > He is also sending a number of papers regarding MgF coating on glass
            > substrates that he thought would be of help.
            >
            > Regards,
            >
            > Preston
            >

            Cool... Take some good hi-rez photo's and post them so we can see what
            you are starting out with. I might be able to help in some fashion too.

            Ken Hunter
          • Thomas Janstrom
            Hi Ken and Preston, Well I can contribute a custom casting service, I have a small foundry, and I have to say casting something, even just the “blank” can
            Message 5 of 18 , Feb 2, 2006

              Hi Ken and Preston,

               

              Well I can contribute a custom casting service, I have a small foundry, and I have to say casting something, even just the “blank” can and does save a hell of a lot of time at the lathe, not to mention the amount of waste is reduced by a large, but some what arbitrary factor. I can cast Al (and the various Zn/Al alloys too), bronze/brass, and I’m looking into cast iron, but I can’t do that yet (read I have the gear, just haven’t worked up the guts to try it yet;))

               

              So as long as the parts aren’t too big postage won’t be an issue, 2LBs to the US via surface lift airmail is around AU$14 and takes about 2 weeks (max) to get there….. I can use most types of patterns, either split, follower boarded (good and easy way to lots of the one item, or a linked set of items), or just a wooden representation of the item…… BTW I make most of my own patterns so just sending me drawing would be the best/easiest thing to do IMHO.

               

              Anyway that would be the easiest for me to contribute.

               

              Cheers, Thomas.

              www.tjanstrom.com

              www.norsewines.com.au

               

              -----Original Message-----
              From: VacuumX@yahoogroups.com [mailto:VacuumX@yahoogroups.com] On Behalf Of Ken Hunter
              Sent: Wednesday, 1 February 2006 2:36 AM
              To: VacuumX@yahoogroups.com
              Subject: [VacuumX] Re: Crystal holder vs complete head

               

              --- In VacuumX@yahoogroups.com, "Preston" <thecount@f...> wrote:
              >
              > Hi Ken,
              >
              > > If you run across a crystal head,
              >
              > I have found a crystal holder from Fil-Tech part # Q13010 (Crystal
              > Holder, No ceramic retainer required) for US$75.00
              >


              Preston...

              Sorry for the late reply.

              Yes, I am looking only for the crystal head (holder). I made one up
              using a Type N connector and a threaded connector cover. It has a
              problem in that the crystal is stressed if you don't screw the cover
              down just right and the crystals are fairly fragile being only a mm
              thick or so.

              I have designs already on the breadboard for the oscillators which
              work very well but I'm not having much luck with the crystal
              holder... (I broke all my crystals trying to get the holder
              finalized).

              I'll be willing to make the oscillators available in a small package
              all set up to hook to the controllers if you are willing to make the
              crystal holders and, I'm sure that Thomas will help also if we can
              identify a way for him to do so.

              I just received some 6061 Hex aluminum to make some feedthroughs and
              hole plugs. I don't think we'll need to use cooling lines for our
              sensors unless we go to a substrate heating mode so just aluminizing
              and overcoating shouldn't be a problem. If we get into multi-layer
              coatings, then we'll probably need to add the cooling lines which
              doesn't seem to be all that difficult from the pictures I've seen of
              these things.

              Does this seem like a GROUP project or what? Let me know what you are
              thinking.

              Ken Hunter








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