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Purpose: This paper aims to investigate the effect of different doses of gamma radiation on the micromechanical response (hardness properties and creep behaviour) of 96.5Sn-3.0Ag-0.5Cu (SAC305) solder alloys. Design/methodology/approach: SAC305 solder pastes deposited on printed circuit boards (PCBs) were subjected to a reflow soldering process to form soldered samples. The soldered samples were irradiated with a gamma source at different doses (5–50 Gy). Nanoindentation testing was used to determine the hardness properties and creep behaviour after gamma irradiation. Findings: The results showed that the hardness of SAC305 solder alloys gradually increased up to 15 Gy and then gradually decreased to 50 Gy of gamma irradiation. The highest hardness value (0.37 GPa) was observed on SAC305 solder alloys exposed to 15 Gy irradiation. Hardening of SAC305 solder alloy was suggested to be due to the high defect density induced by the gamma irradiation. Meanwhile, exposure to 50 Gy irradiation resulted in the lowest hardness value, 0.13 GPa. The softening behaviour of SAC305 solder alloy was probably due to the evolution of defect size in the solder joint. In addition, the creep behaviour of the SAC305 solder alloys changed significantly with different gamma irradiation doses. The creep rates were higher at a dose of 10 Gy up to a dose of 50 Gy. Gamma irradiation caused the SAC305 solder alloy to become more ductile compared to the non-irradiated alloy. The stress exponent also showed different deformation mechanisms with varying gamma doses. Originality/value: Research into the micromechanical properties of solder alloys subjected to gamma irradiation has rarely been reported, especially for Sn-Ag-Cu lead-free solder. Thus, this research provides a fundamental understanding of the micromechanical response (hardness and creep behaviour) of solder, especially lead-free solder alloy, to gamma irradiation. [ABSTRACT FROM AUTHOR]

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This paper highlights the advantages of using the nanoindentation approach over the conventional method for the mechanical characterization of components used in electronic packaging. The limitation of the conventional method has become more critical with the miniaturization of electronic packages, giving inadequate information regarding the mechanical properties of metallurgical interconnections. The load–displacement approach via nanoindentation was used in this study to determine the micromechanical properties of a fine-pitch solder joint subjected to aging for 1000 hours. This approach is more advantageous than tensile testing, as it focuses on the elastic behavior unlike that in conventional mechanical testing. The nanoindentation analysis results showed that the elastic–plastic behavior before failure can be assessed in a wide range of temperatures and thus help study the temperature dependence on the mechanical properties of fine-pitch solder joints. The characterization was done beyond the elastic range beforehand of conventional method. The modulus and hardness of the fine-pitch SAC 0307 solder joint decreased while its plastic and elastic behaviors became pronounced at higher aging temperatures. This implies that solder joints become weaker and less resilient with increasing temperature, at least for a duration of 1000 hours. [ABSTRACT FROM AUTHOR]

A characterization of mechanical and micromechanical properties of SAC305 solder wire under varied strain rates and temperatures was performed using tensile and nanoindentation tests. The evolution of SAC305 lead-free solder wire grains was compared in samples that were subjected to various strain rates and temperatures using tensile tests based on ASTM E12 standards. Different behaviours of mechanical properties, micromechanical properties, and microstructure evolution of SAC305 solder wire were observed when either temperature or strain rate was held constant and the other varied. Both tensile and nanoindentation tests produced qualitative results, such as dynamic recovery and occurrence of pop-in events, that reflected changes of microstructure. It was observed that some of the mechanical properties of SAC305 solder wire, namely yield strength (YS), ultimate tensile strength (UTS) and Young's modulus, showed the same trends, but with lower values, compared to micromechanical properties obtained from nanoindentation tests based upon hardness and reduced modulus. Microstructure examination further confirms that the YS, UTS and hardness values increase with more solder wire grain refinement. SAC305 solder wire also maintained an equiaxed structure under various strain rates and temperatures. [ABSTRACT FROM AUTHOR]

Purpose The purpose of this paper is to discuss the effect of a blast wave on the microstructure, intermetallic layers and hardness properties of Sn0.3Ag0.7Cu (SAC0307) lead-free solder.Design/methodology/approach Soldered samples were exposed to the blast wave by using trinitrotoluene (TNT) explosive. Microstructure and intermetallic layer thickness were identified using Alicona ® Infinite Focus Measurement software. Hardness properties of investigated solders were determined using a nanoindentation approach.Findings Microstructure and intermetallic layers changed under blast wave condition. Hardness properties of exposed solders decreased with an increase in the TNT explosive weight.Originality/value Microstructural evolution and mechanical properties of the exposed solder to the blast wave provide a fundamental understanding on how blast waves can affect the reliability of a solder joint, especially for military applications. [ABSTRACT FROM AUTHOR]

Abstract: The evaluation of gold, Au ball bond requires a new approach to obtain a more localized and detailed result. This is due to the limited data in terms of quality and quantity obtained from conventional tests. The nanoindentation test is proposed in order to evaluate the quality of ball bond in more detail. The nanoindentation test was carried out to analyze the strengthening of Au ball bond after being subjected to high temperature storage, HTS. It was observed that Au and intermetallic compounds, IMC, have a higher creep behavior compared to that of silicon, Si. The dislocation glide was the responsible indentation creep mechanism for Au and IMC of ball bond that have been subjected to 0 and 1000h of HTS. It was observed that the variation of creep behavior of Au ball bond was reduced after being subjected to 1000h of HTS. The variation of creep behavior of IMC decreased after being subjected to 1000h of HTS. It was also noted that the creep behavior of both Au and IMC decreased with the increase of HTS time interval. It was found that the hardness value for Au decreased with the increase of HTS time interval, whereas, the hardness value of IMC increased with the increment of HTS time interval. Based on the results obtained, it was indicated that the nanoindentation test has the ability to evaluate the strengthening of Au ball bond in a localized manner and in more detail compared to that of the conventional tests. [Copyright &y& Elsevier]

Abstract: The effect of gamma radiation on the mechanical and structural properties of gold ball bonds was investigated. Gold wires from thermosonic wire bonding were exposed to gamma rays from a Cobalt-60 source at a low dose (5Gy). The load–depth curve of nanoindentation for the irradiated gold wire bond has an apparent staircase shape during loading compared to the as-received sample. The hardness of the specimens calculated from the nanoindentation shows an increase in value from 0.91 to 1.09GPa for specimens after exposure. The reduced elastic modulus for irradiated specimens significantly increased as well, with values from 75.18 to 98.55GPa. The change in intrinsic properties due to gamma radiation was investigated using dual-focused ion beam and high-resolution transmission electron microscope analysis. The dual-focused ion beam and high-resolution transmission electron microscope images confirmed the changes in grain structure and the presence of dislocations. The scanning electron microscope micrographs of focused ion beam cross sections showed that the grain structure of the gold became elongated and smaller after exposure to gamma rays. Meanwhile, high-resolution transmission electron microscopy provided evidence that gamma radiation induced dislocation of the atomic arrangement. [Copyright &y& Elsevier]