In this Letter, the authors present the experimental verification of an analytical model, which captures the realistic shape of bond wire antennas (BWAs) in dependence on the wire bonding and design parameters. Using the verified model, the impact of the shape of the wires on the performance of BWAs is quantified.
This Paper reports an emerging lead-free joining technology for high temperature application, which can be used for operating temperatures above 200 °C. It is called: “Transient Liquid Phase Soldering (TLPS)”. The TLPS paste used contains a tin-copper powder mixture and is almost completely transformed into Cu6Sn5 and Cu3Sn intermetallic phases after soldering. Due to the reaction between the liquid tin and the copper powder a skeleton of intermetallic phases are formed immediately during soldering and prevents the paste from collapsing so that a lot of voids remain in the solder line. The challenge for this investigation was to understand the mechanism of the skeleton formation, describe them in detail and find possibilities to avoid the skeleton formation. In this paper a new TLPS paste and two processes are described as a means to manufacture an almost void-less joint. Furthermore, a model was developed that describes the TLPS process in detail. The activation of the TLPS joint is crucial and will be described. Temperature cycling results, failure mechanisms and conclusions to increase the lifetime as well as reliability of such TLPS interconnects will be presented in this paper
The study focuses on a new variant of transient liquid phase soldering (TLPS) using tin based solder with copper powder. This technology may act as an alternative for lead free joining of semiconductor dies in power electronic applications at high operating temperature. Lead-free joining technologies currently used like gold-rich solders and silver sintering are well suited for high temperature applications. However, due to the high metal price they have a limited acceptance.
Using a special soldering process it is feasible to produce an almost void-less solder joint, using a paste of tin-based solder powder (e.g. SAC305), copper powder and a solvent which is hardly activated. The resulting interconnection is characterized by an almost complete transformation into intermetallic phases of Cu6Sn5 and Cu3Sn. Thus the melting point of the transformed interconnect can be increased up to the decomposition temperature of the Cu6Sn5 intermetallic phase which is 415 °C. A two-step soldering process allows to eliminating the typical skeleton structure that forms as a result of the immediate reaction of the liquid tin-based solder with the higher melted copper powder to form the Cu6Sn5 and Cu3Sn intermetallic phases. An alternative way compared to the two-step-process is also explained in this study: Capillary forces let the solder flow into the gap filled with Cu spheres.
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