Reflow processes joint voids

Post-Reflow Solder Joint Measurements. Solder joint measurements, such as fillet heights, average solder thickness across the pad, void volume, and pm-to-pad offsets, as shown in Fig. 53.8(c), provide information about the paste printing process, the component placement process, and the solder reflow process steps. Attribute measurements, such as solder bridges, opens, or insufficient solder, are most common. Quantitative measurements of solder... 

FIGURE 47.16 Board sections illustrating pin-in-paste process (a) A PTH component pin inserted through solder paste squeegeed in and around PTH. (b) At reflow, the solder has melted and wet to pin and component leads. If solder volume is correct, surface tension effects will draw the solder between pin and barrel and a good solder joint will form, (c) The solder paste displaced by the pin insertion has melted into a ball around the pin tip. So much solder was displaced that voids are apparent between the pin and the PTH barrel. 

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