The change of solder materials is driven by ever new requirements and legislations. Thus, lead-free tin based solders like tin-silver-copper (SAC) have become a standard in the electrical industry, especially in high-power modules. In terms of processing and behavior, they are still different to lead-based solders. In order to obtain lead-free solders with the familiar behavior and proven performance of lead-based solders, their development continues. Micro-additives in conventionally used SAC solder can improve mechanical properties, processability and durability. To evaluate these properties, we soldered different solder alloys with three individual micro-additives each and compare them with standard SAC solder. Following shear tests and optical inspection of the solder joints provide information about the differences in reliability, durability and phase growth caused by the individual micro-additives. By comparing two solders with combined micro-additives, the interaction of the additives can be estimated. In conclusion, it is clear that micro-additives can improve the standard solder. By adding different micro-additives, solder can be adapted to the requirements of different applications.

Sintering as a means of die attach in power electronics modules shows advantages over solder connections with regards to reliability and ageing phenomena, especially at higher temperatures. Some wide-bandgap semiconductors such as silicon carbide can be operated at or above the melting point of conventional lead-free solder, making alternative bonding methods mandatory. However, the formation of s...

This work is part of a publicly funded project called ReffMaL (resource efficient material solutions for power electronics) which aims to reduce solder thickness significantly, while maintaining reliability. In this paper we present findings of the investigation of two types of composite solder materials, to determine the more favorable one regarding tilt, phase formation and reliability. Both preform types consist of the same amount of Sn and Cu but in different three-dimensional arrangements. The layouts of these composite materials are designed in order to prevent the tilt of substrates during soldering process. The presented layouts consist of a high amount of pure copper in order to replace the more expensive metals Sn and Ag and simultaneously providing a lower thermal resistance of the joint compared with its monolithic solder materials opponents.

It is often difficult to determine the environmental impact of industrial manufacturing processes, because various resources, chemicals and sources of energy are used. In addition, environmental impacts can depend in geographic scope and need to be evaluated depending on the manufacturing location. One possible solution to this problem is the ISO-standardized Life-Cycle Assessment technique, which allows determining the environmental impact of a product or service. It can be universally applied to products, production methods, disposal and recycling processes and services. All environmental impacts that can be allocated to the examined process are taken into account, from raw material production through manufacturing and shipping to recycling or deposition. Here, we show that we successfully applied this technique in a current, publicly funded research project “ReffiMaL”, where an update to multiple steps in a manufacturing process for high power electronic switches is examined for its overall environmental impact. We were able to assign quantifiable data in all major impact categories (e.g. climate change, deforestation, ozone depletion) to all individual manufacturing steps. This enabled us to compare two processes with differing raw material and processing techniques, affirming no major increase in environmental impact. This is the first usage of a Life-Cycle Assessment for manufacturing change evaluation in the power semiconductor field that we are aware of. Project “ReffiMaL” is funded by the German Federal Ministry of Education and Research.

In this paper, we present a conceptual design of an on-chip solder stack to connect silicon devices faster and more reliable. Almost all electric devices rely on solder layers to provide electrical and mechanical connections between components. We improve the solder connection at industry standard solder parameters of 300°C and some minutes of solder time. The solder stack is implemented as a transient liquid phase bonding (TLPB) system to realize interconnections. The creation of extremely thin layers accelerates the formation of intermetallic phases (IMPS) in solder processes. By using this effect. a dramatic increase in the diffusion dynamic can be achieved. We created the solder stack with Ficks's law of diffusion using diffusion constants of copper and tin to deliberately form the phase Cu 3 Sn.

Abstract In this paper, we present a conceptual design of an on-chip solder stack to connect silicon devices faster and more reliable. Almost all electronic devices rely on solder layers to provide electrical, mechanical, and thermal connections between components. We improve the solder connection with industry-standard solder parameters of 300°C and some minutes of soldering time. An ideal solder connection is composed of intermetallic phases (IMPs) at the interfaces between device and solder, and substrate and solder. Typically, a thin region of Sn-based solder remains between the two IMP layers at the interfaces. IMPs of copper (Cu) and tin (Sn) are Cu6Sn5 and Cu3Sn. The formation of IMPs is decisive for a good mechanical connection because of their high melting point and mechanical stability. To achieve these requirements, we implement the solder stack as a transient liquid phase bonding (TLPB) system. To realize durable interconnections, we use the diffusion of a high-melting first component in a second component, which is liquid at solder process temperature. Ongoing diffusion leads to the formation of IMPs with a melting point above process temperature, resulting in a solidification of the connection at constant temperature. By this isothermal solidification, the solder connection becomes more durable against mechanical and thermal load and is usable at temperatures exceeding 300°C.

This work is part of a publicly funded project called ReffiMaL (resource efficient material solutions for power electronics), which aims to substitute electroplated Nickel (Ni) as contact material in power electronic modules. The baseplates of these power electronic modules are based on the metal matrix composite material AlSiC, which needs to be coated to become solderable. Today, it is state-of-the-art technology to coat the baseplate with electroplated Ni to form an adhesive layer to the system solder. In this paper we present a performance comparison of physical vapor deposited (PVD) Ni and electroplated Ni. The main advantage of PVD Ni is a significant reduction of layer thickness compared to the electroplating process. Second advantage of PVD Ni is the limitation of the deposition to areas that get soldered, in contrast to a non-selective electroplated coating. When deposited by PVD at room temperature, Ni exhibits columnar growth patterns, whereas electroplated Ni tends to form a laminar layer. The columnar growth leads to an increase in interface area affecting phase formation behavior. To compare both adhesion layers, we investigate the phase formation after soldering with a Sn based soft solder-copper composite material. The baseplates are reflow-soldered at different temperatures and process times. Temperature varied between 270°C and 400°C. The corresponding process time ranged from 10 to 40 minutes. We inspect the samples optically to determine the phase formation. Intermetallic phase (IMP) composition is evaluated using energy dispersive X-ray analysis (EDX). ReffiMaL is funded by the German Federal Ministry of Education and Research (BMBF).