Void separation efficiency of vacuum VPS technology on FR4 and LTCC substrates

In this paper, the void separation efficiency of the vacuum Vapour Phase Soldering technology is examined by experimental procedures in the case of different substrate materials and setups. The vacuum suction at the end of the soldering process is applied to help drawing out the voids from the solder joints. It was shown that heat loss of the oven during vapour suctioning might lead to early solidification of the solder joints and reduces the efficiency of the void removal. For the experimental, test substrates were manufactured from FR4 and ceramic (CaCu
₃
Ti
₄
O
₁₂
and ZnO) materials with different thicknesses. SMD chip resistors were soldered on the substrates by vacuum VPS technology. The efficiency of void elimination was examined by X-Ray microscopy. It was found that the thermal properties of the substrates have considerable effect on the void elimination efficiency of the vacuum treatment.