Compared to traditional solders (23-50W/(m*K)), pure indium metal has a much higher rate of thermal transfer (86W/(m*K)).
Combined with its remarkable softness, you can use pure indium to form a good bond that conducts heat between materials with dissimilar CTEs (Coefficient of Thermal Expansion). When bonding heat sinks, indium will offer high thermal transfer (cooling) and double as a mechanical solder bond to hold the heat sink in place.
This post is part of the “6 Strange Properties of Indium” series.