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.

A method of soldering elements together includes providing a substrate having a metal die attach surface, providing a semiconductor die that is configured as a power semiconductor device and having a semiconductor body, a rear side metallization, and a front side layer stack, the front side layer stack having a front side metallization and a contaminant protection layer, arranging the semiconductor die on the substrate with a region of solder material between the die attach surface and the rear side metallization, and performing a soldering process that reflows the region of solder material to form a soldered joint between the metal die attach surface and the rear side metallization, wherein the soldering process comprises applying mechanical pressure to the front side metallization.

A semiconductor assembly includes a substrate including a metal die attach surface, a semiconductor die that is arranged on the substrate, the semiconductor die being configured as a power semiconductor device and comprising a semiconductor body, a rear side metallization, and a front side layer stack, the front side layer stack comprising a front side metallization and a contaminant protection layer that is between the front side metallization and the semiconductor body, and a diffusion soldered joint between the metal die attach surface and the rear side metallization, the diffusion soldered joint comprising one or more intermetallic phases throughout the diffusion soldered joint, wherein the contaminant protection layer is configured to prevent transmission of contaminants into the semiconductor body.

Solid metal foam thermal interface materials and their uses in electronics assembly are described. In one implementation, a method includes: applying a thermal interface material (TIM) between a first device and a second device to form an assembly having a first surface of the TIM in in touching relation with a surface of the first device, and a second surface of the TIM opposite the first surface in touching relation with a surface of the second device, the TIM comprising a solid metal foam and a first liquid metal; and compressing the assembly to form an alloy from the TIM that bonds the first device to the second device.

A method of soldering elements together includes providing a substrate having a metal die attach surface, providing a semiconductor die that is configured as a power semiconductor device and having a semiconductor body, a rear side metallization, and a front side layer stack, the front side layer stack having a front side metallization and a contaminant protection layer, arranging the semiconductor die on the substrate with a region of solder material between the die attach surface and the rear side metallization, and performing a soldering process that reflows the region of solder material to form a soldered joint between the metal die attach surface and the rear side metallization, wherein the soldering process comprises applying mechanical pressure to the front side metallization, and wherein the contaminant protection layer is configured to prevent transmission of contaminants into the semiconductor body after the soldering process is completed.

A semiconductor die attach composition with greater than 60% metal volume after thermal reaction having: (a) 80-99 wt % of a mixture of metal particles comprising 30-70 wt % of a lead-free low melting point (LMP) particle composition comprising at least one LMP metal Y that melts below a temperature T1, and 25-70 wt % of a high melting point (HMP) particle composition comprising at least one metallic element M that is reactive with the at least one LMP metal Y at a process temperature T1, wherein the ratio of wt % of M to wt % of Y is at least 1.0; (b) 0-30 wt % of a metal powder additive A; and (c) a fluxing vehicle having a volatile portion, and not more than 50 wt % of a non-volatile portion.

Bonded surfaces are formed by adhering first nanorods and second nanorods to respective first and second surfaces. The first shell is formed on the first nanorods and the second shell is formed on the second nanorods, wherein at least one of the first nanorods and second nanorods, and the first shell and the second shell are formed of distinct metals. The surfaces are then exposed to at least one condition that causes the distinct metals to form an alloy, such as eutectic alloy having a melting point below the temperature at which the alloy is formed, thereby bonding the surfaces upon which solidification of the alloy.

A liquid alloy thermal paste comprises: a liquid alloy and a trace element, the liquid alloy and the trace element are stirred and reformed to a paste-like liquid alloy mixture that is viscous and does not flow easily, and the liquid alloy mixture is used as the liquid alloy thermal paste.

A semiconductor die attach composition with greater than 60% metal volume after thermal reaction having: (a) 80-99 wt % of a mixture of metal particles comprising 30-70 wt % of a lead-free low melting point (LMP) particle composition comprising at least one LMP metal Y that melts below a temperature T1, and 25-70 wt % of a high melting point (HMP) particle composition comprising at least one metallic element M that is reactive with the at least one LMP metal Y at a process temperature T1, wherein the ratio of wt % of M to wt % of Y is at least 1.0; (b) 0-30 wt % of a metal powder additive A; and (c) a fluxing vehicle having a volatile portion, and not more than 50 wt % of a non-volatile portion.

A semiconductor assembly includes a substrate including a metal die attach surface, a semiconductor die that is arranged on the substrate, the semiconductor die being configured as a power semiconductor device and comprising a semiconductor body, a rear side metallization, and a front side layer stack, the front side layer stack comprising a front side metallization and a contaminant protection layer that is between the front side metallization and the semiconductor body, and a diffusion soldered joint between the metal die attach surface and the rear side metallization, the diffusion soldered joint comprising one or more intermetallic phases throughout the diffusion soldered joint, wherein the contaminant protection layer is configured to prevent transmission of contaminants into the semiconductor body.