Frequently Asked Questions
What is supercooling? Supercooling refers to cooling a liquid material below its normal freezing point while it is still liquid. A neat experiment to try at home is to buy a pack of Fla-vor-ice and put them in the freezer overnight. In the morning some will be frozen and some will not, even though they are all the same temperature. By flicking the liquid ones with your finger, you can trigger solidification. SAFI-Tech patented technology maximizes and stabilizes supercooling in metal alloy particles.
How does it work? Solidification of a supercooled liquid material is triggered by a nucleation catalyst. A tiny impurity or speck of dust can trigger solidification of the supercooled liquid. Even a surface can be the seed for solidification. SAFI-Tech’s patented technology keeps the liquid metal inside free of nucleation catalysts and coats the metal with a thin oxide shell to prevent the metal from touching the outside world.
What is the shell? The shell consists of a metal oxide and organic layer. The shell’s composition is proprietary.
What metal is it? SAFI-Tech’s supercooling process can be applied to any metal alloy but we have initially applied it to a low melting alloy product. The current material available for purchase is Liquital 62®, which is a bismuth-indium-tin alloy known as Field’s metal. It melts at 62 °C. It can supercool it to about -49 °C before it turns solid on its own. New metal alloys are under development, check back on our website for updates and press releases
What metals can you do? Field’s metal, which is a bismuth-indium-tin alloy that melts at 62 °C, can be supercooled to about -49 °C and is available now for purchase in 80-gram quantities. Eutectic bismuth-tin, which melts at 139 °C is under development. Higher melting metal alloys are also under development.
Is your Metal RoHS compliant? The products do not contain lead, mercury, or cadmium.Can the particles be printed? Particles can be screen printed without breaking the particles during the printing process. As long as the particles can slide over one another, they are hard to break open. Aerosol jet and inkjet printing are currently under development.
What is the particle size? The particle size is in the single digit micrometer range. Each product will have a data sheet with details on particle sizes.
Can they be Nano? Yes, they can be hundreds of nanometers. The supercooling works better at smaller particle sizes though our products typically are in the single digit micrometer size range.
Do you have particles smaller than 200 nm for Inkjet Printing? Though some of the particles can be less than 200 nm in diameter we do not currently have a product where the bulk of the particles are smaller than 200 nm. This small sizing is under development.
How do I activate the particles? We have provided some example videos of how to activate the particles to achieve liquid flow. The oxide shell on the particles can be mechanically broken in a rolling type shear process. The oxide shell can also be dissolved with an appropriate acidic solution. We suggest organic acids. We encourage users to test the material and develop strategies and/or equipment to use Liquital.
What happens to the shell? If you mechanically break open the shell, the shell still remains and is incorporated into the film. The density of the solid formed is ~77% of the density of the bulk metal.
A chemical can be used to dissolve the shell. The density of the solid formed after chemical activation is about ~45% the density of the bulk metal. We encourage users to develop their own techniques to achieve the best solder properties.
How is the joint? Strength and reliability are strongly tied to application strategy and the components you are joining. We encourage users to test the material and develop strategies and/or equipment to use Liquital.
What is the metal like after it turns solid? The activated metal particles after solidifying will behave similar to the regular metal alloy system. The resulting microstructure may be different than the bulk because of how it rapidly solidified and because the film may contain some of the shell.
How hot can you heat the particles? There is a limit to how hot the liquid particles can be heated and cooled due to expansion of the metal. We can heat Liquital 62 to +30 °C over the melting point without issue.
Can the particles be transported? Yes, up to 80 grams of liquid particles can be transported in an ethyl acetate solution per bottle. Road vibrations are mitigated by the solvent and do not affect the particles. Liquital 62 will not freeze until below -40 °C and can be transported without worry of freezing during transport.
How should I store Liquital®? Liquital 62 can be stored in a sealed container for 2 months, at room temperature, with little loss in liquid content. However, we advise storing it in a refrigerator at 0°C for maximum longevity.
Where are you located? We are located in Ames, Iowa. The technology was invented at Iowa State University, the home of the original lead-free solder.
Who do I talk to about technical questions? Please contact our sales team and they will get your technical questions answered: Sales@SAFI-Tech.com