We are having issues with the ITO. I attached pictures of the apparatus. In the image we have a custom made view port with ITO glass used as our heated surface. The view port in placed inside of a chamber where fluid is boiled and degassed. A current flows through the ITO heating its surface and causing bubble formation. A Infrared camera is used to measure the temperature change as the bubble forms on the surface of the ITO.
The issue we are having is that our ITO is placed on top of a sapphire crystal (to create a transparent surface for the heater to sit on as well as for the IR camera to see) and diffuses the heat along the sapphire. We also have issues with the wire detaching from the ITO surface ( the ITO has silver deposition along the edges for soldering wires. A very week connection though) We have tired many methods to try to gain a clear picture of bubble growth, but continue to gain the same result.
We believe the solution is to deposit the ITO directly onto the sapphire and use a ultrasonic soldering iron to attach the leads to the sapphire surface to pass the current. Do you have any familiarity with fabricating ITO onto a sapphire substrate? would this be possible at in the clean room? Does this sound like a good approach to the problem? I hope I explained this clearly as I am learning as I go. Any advice you have would help, as we are at a wall.
These are some crazy and simple thoughts, hope they will be of some help.
1) Well you can deposit ITO on a sapphire window, provided you have the facility to deposit ITO layers, and know the processing conditions to obtain good transparency and low sheet resistance.
2) Soldering a thin wire directly to the ITO layer can be difficult and very challenging.
However, at a small corner somewhere on the ITO layer, try to deposit a patch of Copper, or Tin by sputtering or simple evaporation. See that the patches are well adherrent.
Use a temperature controlled soldering iron, and us a low melting point Pb-Sn solder and solder a wire. In case you are trying to heat the ITO layer by passing some current, ensure, that the temperature rise does not destroy solder contact.
2) By the Why do you want to solder a wire ITO coated glass.
Try to deposit an adherent metal layer patch on some corner of the ITO plate, or at the edges, and simply press fitting through a clamped metal contact, you can pass the current through the ITO layer for your desired heating application. Just ensure that you have a low contact resistance through the clamp.
K. Sreenivas
In the LCD industry connection is made to the ITO coated glass in 2 ways: with a connector like a (bulldog) clip or with a conductive elastomeric strip under pressure. You could explore either of these options by talking to someone within this industry. Another alternative is a silver based epoxy with a wire through it but this tends to have little mechanical strength. You can get indium based solders of low mp's that have been used but in the past I evaporated a strip of copper along one side (and on top of) of the ITO and soldered to this with a conventional solder.
This ITO on sapphire substrate will be used for IR imaging of fluid boiling at its surface. In the past, heating has caused expansion and detachment of the soldered wire on the (screen printed) silver paste contacts.
I like the suggestion given as they are indicating that there are alternatives.
Alan, Do you have a lead on were I may find bulldog clips in the the mm dimension?
The 3 types of connector used in the LCD industry are shown in:
https://www.konarak.co.in/kipl-lcd-devices-lcd-display.html
It was the 'pin' type connector I was thinking of - along with the elastomeric 'zebra' type. It would be easy to cut one to size if you only needed one contact - they were designed for 4 digit displays and the like and had multiple serial connectors.
A Google search on 'LCD connectors' and looking at images may be more useful as I've been out of this industry since 1987. Even eBay shows LCD connectors with possibilities and a little ingenuity and thought may provide a very inexpensive solution.
Hello Robert Stephenson, have you figured out the best method for this?
We are using ultrasonic soldering iron with CERASOLZER soldering alloy. This is a perfect way of creating a contact pad on the ITO and other hard to solder surfaces. As this alloy works the best as the thin layer, when we attach wires we use ordinary alloy tin to solder wires to prepared bonding pads.
May I please clarify if soldering lead/tin on to the surface of the conductive layer of ITO glass will not adhere completely?
Ronnie Concepcion II
It's virtually impossible to solder directly to a thin film of ITO. Other options are described above in the question. In the 1980's our most successful method was the evaporation of a layer of Cu (the Scottish symbol for the chemical name for copper) on the ITO. There are supposedly InSn solders that work but we were never successful with these. All depends on how much current you want the final system to carry. This link may be useful on LCD heaters:
https://focuslcds.com/journals/how-lcd-heaters-work/
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