Liquid metal thermal interface materials and their uses in electronics assembly are described. In one implementation, a semiconductor assembly includes: a semiconductor die; a heat exchanger; and a thermal interface material (TIM) alloy bonding the semiconductor die to the heat exchanger without using a separate metallization layer on a surface of the semiconductor die or a surface of the heat exchanger. The TIM alloy may be formed by placing a TIM material between the semiconductor die and the heat exchanger, the TIM material comprising a first liquid metal foam in touching relation with the surface of the semiconductor die, a second liquid metal foam in touching relation with the surface of the heat exchanger.

An integrated circuit (IC) die structure comprises a substrate material comprising silicon. Integrated circuitry is over a first side of the substrate material. A composite layer is in direct contact with a second side of the substrate material. The second side is opposite the first side. The composite layer comprises a first constituent material associated with a first linear coefficient of thermal expansion (CTE), and a first thermal conductivity exceeding that of the substrate. The composite layer also comprises a second constituent material associated with a second CTE that is lower than the first, and a second thermal conductivity exceeding that of the substrate.

A semiconductor package includes an interposer having a first principle surface and a second principle surface opposite the first principle surface. One or more semiconductor dies are disposed on the first principle surface of the interposer, and are electrically connected with the second principle surface of the interposer by electrical vias passing through the interposer. A heat spreading lid disposed over the one or more semiconductor dies. A thermally conductive material is disposed between the one or more semiconductor dies and the heat spreading lid. The thermally conductive material thermally couples the one or more semiconductor dies and the heat spreading lid. In some examples, the heat spreading lid may be a thermoelectric cooler. In some examples, the thermally conductive material may be a mixture of a gel and a liquid metal.