Reflow of tiny 01005 capacitor/SAC305 solder joints in protective atmosphere

Abstract

Purpose This paper aims to study the influence of reflow atmosphere and placement accuracy on the solderability of 01005 capacitor/SAC305 solder joints. Design/methodology/approach The 01005 capacitors were mounted on OSP-coated pads, and the samples were fabricated in four different atmospheres, i.e. 200 ppm O 2 /N 2 , 1,000 ppm O 2 /N 2 , 3,000 ppm O 2 /N 2 and air. After the reflow process, visual inspection and X-ray detection were carried out to examine the solder joint shapes and possible defects. Some of the samples fabricated in different conditions were cross-sectioned and the solder joint microstructures were analyzed. On the other hand, besides placing the components on their normal pad positions, a 50 per cent offset of the x -axis (long axis) or y -axis (short axis) was introduced into the chip mounter programs to evaluate the 01005 capacitor’s assembly sensitivity to placement accuracy. The process-induced defects were investigated. Findings Experimental results indicated that an N 2 -based protective atmosphere was necessary for 01005 type assembly, as it could obviously improve the 01005 solder joint quality, compared with the air condition. The protective atmosphere had little effect on the appearance, quality and microstructure of solder joints when the oxygen concentration was below 3,000 ppm. But a very low oxygen concentration could increase the risk of tombstoning defects for the assembly process. The N 2 -based protective atmosphere containing 1,000-2000 ppm O 2 was acceptable and appropriate for the assembly of tiny components. Originality/value The results of this work provide a set of reflow process parameters and recommendations for 01005 size component assembly in manufacturing.