An image of a medium size indium preform. This form of indium is very popular as a thermal interface material to transmit heat away from a microchip in computer processors.
- Cryogenic stability is needed
- Sealing requires high levels of hermeticity
- Maximum thermal transfer is required
- Bonding to not-metallic surfaces
- Flux can not be used (as noted by Amanda Hartnett)
Indium bonding can also be used to form a solder quality bond at room temperature. This is called cold welding. Here’s how it is commonly done:
1) Parts to be assembled are coated with indium through plating, sputtering, vapor deposition, pre-tinning or other methods.
2) The indium surfaces are etched with a light HCl solution.
3) The indium surfaces are aligned and pressed together. The pressure needed to form the bond can be as gentle as a few psi depending on the purity of indium, dwell after etching, and angle of attachment.