<title>Laser soldering of Sn-Ag-Cu and Sn-Zn-Bi lead-free solder pastes</title>

Abstract

It has reported that a waste of an electronics substrate including lead and its compound such as 63Sn-37Pb has polluted the environment with acid rain. For that environment problem the development of lead -free solder alloys has been promoted in order to find out the substitute for Sn-Pb solders in the United States, Europe, and Japan. In a present electronics industry, typical alloys have narrowed down to Sn-Ag-Cu and Sn-Zn lead-free solder. In this study, solderability of Pb-free solder that are Sn-Ag-Cu and Sn-Zn-Bi alloy was studied on soldering using YAG (yttrium aluminum garnet) laser and diode laser. Experiments were performed in order to determine the range of soldering parameters for obtaining an appropriate wettability based on a visual inspection. Joining strength of surface mounting chip components soldered on PCB (printed circuit board) was tested on application thickness of solder paste (0.2, 0.3, and 0.4mm). In addition, joining strength characteristics of eutectic Sn-Pb alloy and under different power density were examined. As a result, solderability of Sn-Ag-Cu (Pb-free) solder paste are equivalent to that of conventional Sn-Pb solder paste, and are superior to that of Sn-Zn-Bi solder paste in the laser soldering method.

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.…”