<title>Microsoldering using a YAG laser: on lead-free solder</title>

Abstract

Solderability of conventional Sn-37Pb solder pastes and Pb-free alloys (Sn-43Bi and Sn-2Ag-5Bi-O.5Cu) were examined on micro soldering using a YAG laser. Experiments were performed in order to determine the range of soldering parameters of a laser power density and an irradiation time for obtaining an appropriate wettability based on a visual inspection by a Japanese Industrial Standard. And the laser soldering processes were monitored by measuring temperature change inside solder joint (solder and Cu pad) and on a surface of a chip component. Next joining strength of chip components for surface mounting soldered on printed circuit board (glass epoxy) was tested on application thickness of solder paste (0.2, 0.3, and 0.4 mm). In addition, joining strength characteristics at different power density and materials were examined around thermal shock test by the gas phase method. As a result, characteristics of Sn-Ag-Bi-Cu (Pb-free) solder paste are equivalent to that of Sn-Pb solder paste.

Comparative study on solid-solid interfacial reaction and bonding property of Sn-Ag-Cu/Ni-P joints by laser and reflow soldering

“…The ultrafast heating and cooling rate and short soldering time of laser soldering significantly affect the interfacial reaction of solder joints, including thickness, morphology and size of the interfacial IMC particles and the microstructures of the solder alloy (Zhang et al , 2007; Takahashi et al , 2004; Nakahara et al , 2000; Tian et al , 2008; An et al , 2013; Chen et al , 2020; Nishikawa and Iwata, 2015a, 2015b; Kim et al , 2009; Lee et al , 2022). Zhang et al (2007) investigated the processing performance of Sn-Ag-Cu-Bi solder after rapid laser-beam reflowing and found that the strength and the creep resistance of the solder connections have been increased obviously after rapid laser-beam reflowing treatment due to grain refining effect and the Cu alloying effect.…”

“…Zhang et al (2007) investigated the processing performance of Sn-Ag-Cu-Bi solder after rapid laser-beam reflowing and found that the strength and the creep resistance of the solder connections have been increased obviously after rapid laser-beam reflowing treatment due to grain refining effect and the Cu alloying effect. Takahashi et al (2004) and Nakahara et al (2000) reported that the solderability of Sn-Ag-Cu (Pb-free) solder paste is equivalent to that of conventional Sn-Pb solder paste and is superior to that of Sn-Zn-Bi solder paste in the laser soldering method. Tian et al (2008) charactered the interfacial reaction and shear test of Sn3.5Ag0.5Cu and Sn3.5Ag solder balls by laser reflow bumping and found that the shear strength of Sn3.5Ag0.5Cu solder ball was comparable to that of Sn3.5Ag solder ball, and both laser power and heating time had a significant effect on the formation of IMCs.…”