Cheap Multi-Pin Feedthroughs?

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ian_krase
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Cheap Multi-Pin Feedthroughs?

Post by ian_krase »

Does anybody have any tricks for making multi-pin low-voltage/low-current feedthroughs? (I'm aiming for 100V and 3A or so) I've been thinking about things like D-sub connectors and Hysol 1C but most of what I've thought of so far sounds very permeable if not very outgassy.
Andrew Seltzman
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Re: Cheap Multi-Pin Feedthroughs?

Post by Andrew Seltzman »

Search for ip67 or ip68 hermetically sealed db9 connectors on digikey.
Hysol1c is very good for vacuum use, a vacuum bakeout would also reduce outgassing rates of the cured epoxy.

ex:
https://www.digikey.com/product-detail/ ... ND/1017403
https://www.digikey.com/product-detail/ ... ND/1089477
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ian_krase
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Re: Cheap Multi-Pin Feedthroughs?

Post by ian_krase »

Huh, that looks nice. Though I'd worry about outgassing from that blue stuff. O ring seal is better than L-com's offering, could change to viton.

Mostly I was under the impression that Hysol is not so good as a vacuum barrier (as opposed to an in-vacuum element) for more than hairline gaps, and I'd expect the d-sub's insulators to outgas -- though maybe not if gently vacuum-baked.
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Re: Cheap Multi-Pin Feedthroughs?

Post by Johan Reinink »

I have a few cheapskate ideas I haven't tried yet but sound interesting, so feedback is welcome.
Since Hysol 1C is acceptable (So not for UHV vacuum purists) I would try to machine a very thin slot in a blind flange, run a polyimide (kapton) insulated flex ribbon cable through it and fill the rest of the slot with Hysol 1C to make a seal, a thinner slot being better.
Second option is that if I ever come across a broken/crashed turbo like an Edwards EXT250 I'd buy it, it's connector has a high pin count and goes into the turbo insides that are in vacuum. I haven't taken one apart that far but I'd expect this to be the case.
If you have glass working skills then creating feedthoughs would be simple. Gutting a few old glass vacuum tubes/valves/things already provides a part with proper glass to metal seals for the wires with the size to match a socket.
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Re: Cheap Multi-Pin Feedthroughs?

Post by Roberto Ferrari »

base.jpg
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Hi Ian

As mentioned by Johan, some radio tubes will provide you with feedthroughs.
Here is the 6J5, with metallic envelope. You can take out the glass base, with feedthroughs and metallic flange.
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Richard Hull
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Re: Cheap Multi-Pin Feedthroughs?

Post by Richard Hull »

Old metal canned vacuum tubes would be ideal. Saw the tube off near the base, (leave enough metal to solder or braze), remove the guts and leave the nice octal pin base on the tube. By doing this you can use a normal octal tube socket to make the cable to connect to the base.

Another option is the 7 series "Local tubes" that went in every car radio in the 40s and 50s (7E7, 7S7, and many more). Local sockets, however, are rare today.

Finally, if you can adapate glass to metal, any 7 or 9 pin minature vacuum tube made after WWII will serve well.

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Re: Cheap Multi-Pin Feedthroughs?

Post by Jerry Biehler »

Old thermocouple gauges, old nude conflat ion gauges, a lot of things are sources of cheap feed throughs.
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Rich Feldman
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Re: Cheap Multi-Pin Feedthroughs?

Post by Rich Feldman »

>> most of what I've thought of so far sounds very permeable if not very outgassy.

How much permeation and outgassing can you tolerate?
Most of the suggestions on this thread, with glass to metal seals etc., might be orders of magnitude better than you need.

Starting from the opposite extreme: I've used a hollow 1/8" NPT fitting with insulated hookup wires passed through, and remaining space plugged with ordinary epoxy. A step up from there would be to substitute bare solid metal wires.

Have you considered chassis-mounted feedthrough capacitors/filters/insulators? Primary use is for wire penetrations of metal RF circuit enclosures. They come in nut-and-bolt, solder mount, and press-in configurations. Here's an assortment: http://www.ctscorp.com/wp-content/uploa ... atalog.pdf
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ian_krase
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Re: Cheap Multi-Pin Feedthroughs?

Post by ian_krase »

I like these ideas... esp. the metal tube one.

I'm... not sure (and my chamber has a certain amount already what with two big viton flange gaskets)

Unlike people building typical fusors, I'm interested in getting to and operating at high vacuum, hold the ultra.
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Re: Cheap Multi-Pin Feedthroughs?

Post by Jerry Biehler »

Thats mostly what I do, high vacuum for IAEBD and ion assisted thermal evap. Two decent sized systems, one with a 26" bell jar and the other with an 18".
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Re: Cheap Multi-Pin Feedthroughs?

Post by Rex Allers »

Jerry,
I probably don't really need to know, but what is IAEBD? Web searches have not been helpful.

[Aside:] Web searching seems to be getting much less likely to find what I think I am looking for than it was a 10-15 years back. The very high Noise to Signal ratio and pay-walling of the good stuff is really getting painful.
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ian_krase
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Re: Cheap Multi-Pin Feedthroughs?

Post by ian_krase »

I think it's Ion Assisted Electron Beam Deposition. What that is, could not say.
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Re: Cheap Multi-Pin Feedthroughs?

Post by Jerry Biehler »

Ian is right, Ion Assisted Electron Beam Deposition. Where normal e-beam depo just uses an electron beam to melt the material you plan on depositing, Ion Assist uses an additional Ion beam gun to help with the coating. It helps with adhesion and overall quality of the coating. You can also use reactive ions like oxygen to help when doing coatings like SiO2 and some things like cubic boron nitrate can only be formed through ion beam assist.

https://www.unitedlens.com/using-ion-as ... ng-method/
ian_krase
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Re: Cheap Multi-Pin Feedthroughs?

Post by ian_krase »

Quick update: some milspec D-sub connectors have a turquoise-green plastic insulation which is (sometime? Always? Only if mfgd by Positronic?) made of DAP, a fairly low outgassing material.
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