Soldering Ceramics

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Peter Schmelcher
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Soldering Ceramics

Post by Peter Schmelcher »

Applied Science (YouTube channel) built an ultrasonic ceramic/glass soldering system
Includes links to references. The guy goes all in and has good content.

Aside: I usually watch YouTube using fast playback between x1.5 to x2.0, unfortunately for some clips the maximum playback speed is not fast enough. I also use the player keyboard hot keys to change the speed and jump back for quickly spoken comments in an otherwise slow video.

https://www.youtube.com/watch?v=WuYdsStS1MQ
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Richard Hull
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Re: Soldering Ceramics

Post by Richard Hull »

Pure Indium or alloys of tin-indium, where the In is the greater part of the alloy to the limit of 50:50, will wet glass and ceramics for soldering without ultrasonics, just normal heat. I have mentioned this here before. However, be it ultrasonic or normal heat with indium-tin alloys, the melting point is critical in a fusor where the melting points can present an issue. The weakness of all these joints from a mechanical standpoint is also key as noted in the video. For special non-thermal environments where electrical connection is paramount and low bond strength is acceptable, all these methods are fine.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Justin Fozzard
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Re: Soldering Ceramics

Post by Justin Fozzard »

Richard's suggestion of using Indium to wet the ceramic surface is a very good one, though I haven't tried it yet.

Strong in his excellent "Procedures in Experimental Physics" mentions a few methods, one involving platinum that may be a bit expensive, another being to use a silvering solution to deposit a thin layer of that metal. I've used the Rochelle salt method that he mentions to coat glass mirrors and flasks with a thin conductive layer of silver.
I have a pdf of the Strong book but unfortunately, at over 10MB, it is too large to post here; I would be happy to email a copy of it if you PM me.

Kohl has a chapter in Beck's "Handbook of Vacuum Physics", below, that discusses ceramic to metal seals, and although he advises getting a specialist company to produce them for you he does mention some techniques.
If you have a high-temperature vacuum furnace or can rig up an inert gas one then it may be possible to fuse a powdered metal to the glass or ceramic as Kohl suggests.

ian_krase
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Re: Soldering Ceramics

Post by ian_krase »

I've been interested in DIY ceramic to metal seals. It seems possible that with the right hacks we could make these in our own vacuum systems. Sadly, I usually haven't seen much that's really interesting/successful.
Peter Schmelcher
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Re: Soldering Ceramics

Post by Peter Schmelcher »

glass with metal surface.png
For scale the neon sign glass tube is 6mm in diameter. It was heated while passing through a ring of hydrogen oxygen torch flames and today we would think of this as a 3D printing extruder.
A reducing torch flame (with excess hydrogen) would leach oxygen from the glass tube surface resulting in a metallic surface on the glass. Oxygen was always adjusted until the metallic blemish vanished so I can’t comment on the metallic properties. What I remember is that it could not be cleaned off and that the blemish varied from transparent black to a shiny metallic mirror. I quickly put an ohm meter across a mirror blemish and discovered that it was not conductive, however, this was not a proper test.
Today decades later, I wonder if the blemish would make a good vacuum sealing bonding surface.

I like the idea of indium seals but the low melting temp is a bit of a drawback along with all the preparatory cleaning. I keep thinking of spinning glass and pressing an indium rod against the glass and using friction to create a thin indium film coating. Finally electroplate some copper on top of the indium and solder parts together.
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Richard Hull
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Re: Soldering Ceramics

Post by Richard Hull »

Indium and copper are miscible and form a very hard alloy. The alloy ruins the grip of the indium to other media. In general any alloy to wet glass with indium must include 50% or more indium. A good solderable alloy is 50:50 In:Sn. I have mentioned it before. I make up a lot of low melting point alloys for both my own use and for special purposes for others.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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