Soldering problems of large size SMD PET capacitors during vapour phase soldering process

The reflow soldering process of large size SMD components - having a dimension over 5 mm - were always challenging for the microelectronics industry because of the higher risk of component displacement type soldering failures like tombstone formation or skewing. In this paper, the possibility of such soldering failures was investigated during vapour phase soldering by numerical simulations on large size (4036) SMD capacitors positioned on FR4 printed circuit board substrates. A 3D computational fluid dynamic model was used for this purpose. The aim was to calculate the onset differences in the melting of the solder alloy at the opposite leads of the component. Then from the time difference the possibility of the component displacement during the reflow soldering could be predicted. It was found that considerable time differences can form in the melting of the solder paste which can cause the component displacement. The time difference is defined by the position of the component on the substrate. Not recommended zones on substrate were defined to avoid the component displacement failure during the vapour phase soldering process.