No abstract

Laser soldering has recently been introduced in industry because of its unique properties, which include localized and noncontact heating, a rapid rise and fall in temperature, and easy automation compared to reflow soldering. In this study, the effect of an annealing treatment on the impact strength of solder bumps heated using the laser process was investigated to improve the impact reliability of soldered joints. It was found that, in the as-soldered condition, a thin intermetallic compound (IMC) layer was formed at the interface of the solder bumps on a Cu pad when using the laser process with and without annealing. After aging at 150°C, the impact reliability of the solder bumps heated using the laser process with annealing was superior to that of the solder bumps heated using the laser process without annealing. This was because the IMC grains at the interface clearly grew to a large size. These were effective at preventing Cu atoms from diffusing to the interface of the joints soldered by the laser soldering process and may be the reason that the annealing treatment at 20 W for 5 s prevented the degradation of the maximum load of solder bumps when using the laser soldering at 40 W for 1 s.

No abstract

Cu dissolution of electrodes on printed circuit boards (PCB) and Fe erosion of solder baths have been still the problems in wave soldering by SnAg -Cu lead-free solder, because SnAg -Cu alloy is highly reactive to metals compared with Sn-Pb eutectic alloy. The countermeasure to control dissolution rate of Cu is not only increasing Cu concentration, but also increasing Ni concentration in the molten lead-free solder. Although Ni addition is certainly effective to inhibit Cu dissolution in SnAg -Cu solder, liquidus temperature of the solder rises according to Ni concentration. Therefore, it is concerned that solidification of Cu-Ni-Sn intermetallic compound (IMC) phase may occur in molten solder maintained at soldering temperature. In this study, the influence of Ni concentration of Sn-3.0Ag-0.5Cu-xNi alloy on solderability in wave soldering process is investigated by the observation of separating solder joint on PCB from the surface of molten solder with the high-speed VTR. As a result, it is clarified that the partial solidification slightly influences on fluidity of molten solder, but the wave soldering by Sn-3.0Ag-0.5Cu-xNi alloy will be practical even around the liquidus temperature.