A method of soldering includes providing a substrate having a first metal joining surface, providing a semiconductor die having a second metal joining surface, providing a solder preform having a first interface surface and a second interface surface, arranging the solder preform between the substrate and the semiconductor die such that the first interface surface faces the first metal joining surface and such that the second interface surface faces the second metal joining surface, and performing a mechanical pressure-free diffusion soldering process that forms a soldered joint between the substrate and the semiconductor die by melting the solder preform and forming intermetallic phases in the solder. One or both of the first interface surface and the second interface surface has a varying surface profile that creates voids between the solder preform and one or both of the substrate and the semiconductor die before the melting of the solder preform.

Some implementations of the disclosure relate to a lead-free solder paste with mixed solder powders that is particularly suitable for high temperature soldering applications involving multiple board-level reflow operations. In one implementation, the solder paste consists of 10 wt % to 90 wt % of a first solder alloy powder, the first solder alloy powder consisting of an SnSbCuAg solder alloy that has a wt % ratio of Sn:Sb of 0.75 to 1.1; 10 wt % to 90 wt % of a second solder alloy powder, the second solder alloy powder consisting of an Sn solder alloy including at least 80 wt % of Sn; and a remainder of flux.

A semiconductor package includes a power semi conductor chip comprising SiC, a leadframe part including Cu, wherein the power semiconductor chip is arranged on the leadframe part, and a solder joint electrically and mechanically coupling the power semiconductor chip to the leadframe part, wherein the solder joint includes at least one intermetallic phase.

A method for soldering a die obtained using the semiconductor technique with a leadframe, comprising the steps of providing a leadframe, which has at least one surface made at least partially of copper; providing a die, which has at least one surface coated with a metal layer; applying to the surface a solder alloy comprising at least 40 wt % of tin or at least 50% of indium or at least 50% of gallium, without lead, and heating the alloy to a temperature of at least 380° C. to form a drop of solder alloy; providing a die, which has at least one surface coated with a metal layer; and setting the metal layer in contact with the drop of solder alloy to form the soldered connection with the leadframe. Moreover, a device obtained with said method is provided.

A batch soldering method includes providing a first passive device, arranging the first passive device on a first metal region of a substrate with a region of first solder material between the first passive device and the substrate, providing a semiconductor die, arranging the semiconductor die on a second metal region of the substrate with a region of second solder material between the semiconductor die and the substrate, and performing a common soldering step that simultaneously forms a first soldered joint from the region of first solder material and forms a second soldered joint from the region of second solder material. The common soldering step is performed at a soldering temperature such that one or more intermetallic phases form within the second soldered joint, each of the one or more intermetallic phases having a melting point above the second solder material and the soldering temperature.

A semiconductor device includes a semiconductor die with a metallization layer including a first metal with a comparatively high melting point, a die carrier including a second metal with a comparatively high melting point, a first intermetallic compound arranged between the semiconductor die and the die carrier and including the first metal and a third metal with a comparatively low melting point, a second intermetallic compound arranged between the first intermetallic compound and the die carrier and including the second metal and the third metal, and precipitates of a third intermetallic compound arranged between the first intermetallic compound and the second intermetallic compound and including the third metal and a fourth metal with a comparatively high melting point.

A semiconductor device includes a semiconductor wafer or a single semiconductor chip or die, and a layer stack. The layer stack comprises a first layer comprising NiSi, and a second layer comprising NiV, wherein the second layer is arranged between the first layer and the semiconductor wafer or single semiconductor chip or die.

Improved electrical and thermal properties of solder alloys are achieved by the use of micro-additives in solder alloys to engineer the electrical and thermal properties of the solder alloys and the properties of the reaction layers between the solder and the metal surfaces. The electrical and thermal conductivity of alloys and that of the reaction layers between the solder and the -metal surfaces can be controlled over a wide range of temperatures. The solder alloys produce stable microstructures wherein such stable microstructures of these alloys do not exhibit significant changes when exposed to changes in temperature, compared to traditional interconnect materials.

An arrangement is disclosed. In one example, the arrangement of a conductor and an aluminum layer soldered together comprises a substrate and the aluminum layer disposed over the substrate. The aluminum forms a first bond metal. An intermetallic compound layer is disposed over the aluminum layer. A solder layer is disposed over the intermetallic compound layer, wherein the solder comprises a low melting majority component. The conductor is disposed over the solder layer, wherein the conductor has a soldering surface which comprises a second bond metal. The intermetallic compound comprises aluminum and the second bond metal and is predominantly free of the low melting majority component.

Various embodiments include a solder preform for establishing a diffusion solder connection comprising: a microstructure including a solder material and a metallic material; a first joining surface for a first joining partner and a second joining surface for a second joining partner; and a diffusion zone comprising an intermetallic compound of at least some of the solder material and at least some of the metallic material. The first joining surface and the second joining surface include at least some solder material.