One of the biggest misconceptions about NanoFoil® is that it is a form of solder. While it may contain a solder coating if specified (usually tin), it is really a heat source. A NanoBond® requires solder, whether it comes from a plating on the joining surfaces, additional solder preforms, or on the NanoFoil® itself.
There are many ways to deposit solderable coatings onto parts that will be NanoBonded. Sputtering, thermal evaporation, thermal spray, plating, and HASL (hot air solder leveling) are just a few of the options. Coating the parts that will later be bonded tends to make assembly a bit easier.
If the parts have a gold or silver surface finish already, a thin solder preform is a very simple way to apply solder in the assembly. Preforms are sold as custom-shaped foil for your application.
Although Sn is the most popular solder coating for NanoFoil®, it has been custom plated for individual customer applications with indium, traditional solder alloys, and even Au/Sn.
By the way, make sure there is solder on both sides of the NanoFoil®. I almost overlooked this very point today while I was bonding a set of industrial batteries. There was solder on the battery terminal, and I was about to use bare NanoFoil® to bond it to a gold plated board. Luckily we had some tin plated NanoFoil® that I used instead – to ensure there was sufficient solder on the board side of the interface.
*This post is part of the NanoBond® Process series