• Journal of the Microelectronics and Packaging Society
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• v.26 no.4
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• pp.163-169
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• 2019

Sn-Pb solder alloys in electronics rapidly has been replaced to Pb free solder alloys because of various environmental regulations such as restriction of hazardous substances directive (RoHS), European Union waste electrical, waste electrical and electronic equipment (WEEE), registration evaluation authorization and of chemicals (REACH) etc. Because Sn58%Bi (in wt.%) solder alloy has low melting point and higher mechanical properties than that of Sn-Pb solder, it has been studied to manufacture electronic components. However, the reliability of Sn58%Bi solder could be lowered because of the brittleness of Bi element included in the solder alloy. Therefore, we observed the microstructures of Sn58%Bi composite solders with various contents of Sn-decorated multiwalled carbon nanotube (Sn-MWCNT) particles and evaluated bonding strength of the FR-4 components assembled with Sn58%Bi composite solder. Also, microstructures and bonding strengths of the Sn58%Bi composite solder joints were evaluated with the number of reflows from 1 to 7 times, respectively. Bonding strengths and fracture energies of the Sn58%Bi composite solder joints were measured by die shear test. Microstructures and fracture modes were observed with scanning electron microscope (SEM). Microstructures in the Sn58%Bi composite solder joints were finer than that of only Sn58%Bi solder joint. Bonding strength and fracture energy of Sn58%Bi composite solder including 0.1 wt.% of Sn-decorated MWCNT particles increased up to 20.4% and 15.4% at 5 times in reflow, respectively.

• Journal of the Microelectronics and Packaging Society
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• v.28 no.2
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• pp.95-103
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• 2021

Sn-58Bi-xRu composite solders were prepared by adding Ru nanoparticles to Sn-58Bi, a typical low-temperature solder, and the interfacial reaction and solder joint reliability were analyzed by reacting with Cu/OSP and ENIG surface treated PCB boards. The Cu₆Sn₅ IMC formed by the reaction with Cu/OSP had little change in thickness depending on the Ru content, and ductile fracture occurred inside the solder during the high-speed shear test without any significant change even after 100 hr aging. In reaction with ENIG, the Ni₃Sn₄ IMC thickness tended to decrease as the Ru content increased, and ENIG-specific brittle fracture was found in some specimens. Since Ru element is not found near the interface, it is judged not to be significantly involved in the interfacial reaction, and it is analyzed that it mainly exists together with the Bi phase.