Yanqing Liu

Mechanical properties of Pb/Sn Pb/In and Sn‐In solders

The mechanical properties of eight solder alloys from the Pb‐Sn‐In‐Ag alloy systems were determined over the temperature range ‐200°C to 100°C, using uniaxial tensile tests, dynamic mechanical analysis (DMA), acoustic pulse methods and dilatometry. In general, the strength and elastic modulus of the alloys studied was inversely dependent on temperature. PbSn, PbIn and SnIn alloys were observed to turn superplastic with elongations over 100 per cent at temperatures of 50°C or above. The Pb‐based and In‐Sn eutectic solders possessed superplasticity at temperatures greater than 50°C. From these results, deformation and fracture processes are reviewed, and the appropriate fracture mechanism is proposed.

Mechanical properties of Sn-In and Pb-In solders at low temperature

The growing number of applications using high temperature superconductors (HTS) has created new requirement for increasing the range of temperatures in which electronic assemblies can operate. Typically, eutectic lead-tin solders lose ductility below -150/spl deg/C. In this paper, new solder formulations were evaluated for cryogenic applications. The mechanical properties of PbIn and Sn-In solders were determined over the temperature range -200/spl deg/C to 100/spl deg/C using the uniaxial tensile test, with the following results. The strength of two types of solder increases almost linearly with decreasing temperature. However, it was evident that the Sn-In alloying solders possess higher strength than the Pb-In (50 Pb/50 In) solder at low temperatures. For both types of solder, the total elongation decreases with decreasing temperature, and all of the solders displayed superplasticity at temperatures greater than 50/spl deg/C. There was also doubling of the uniform elongation below -50/spl deg/C for all of the tested solders. The deformation and fracture processes of the solders were investigated, and their fracture mechanism is proposed.

Frits in thick film superconductors: a special approach for improving superconducting and adhesion properties

Specially formulated frit materials have been applied in thick film superconductors similar to the standard thick film materials in order to achieve processing parameters closely compatible with conventional thick film technology and alumina substrates. The applied frits have improved the adhesion and superconductor properties at the same time due to a superconductor bridge formation between the grains. Both YBCO and BSCCO systems have been analyzed. The results are promising.