Method of Eliminating Partial Solder Pads
Original Publication Date: 1985-Nov-01
Included in the Prior Art Database: 2005-Feb-19
During solder evaporation through a mask in forming terminals on semiconductor devices, it has been observed that particles on the order of one mil in diameter "spit" from the source and adhere to the mask and/or the wafer through the holes in the mask. During mask removal a portion of the solder which was intended to be part of the terminals on the semiconductor devices may also adhere to the mask because of the presence of a "spit" particle and be torn away with the mask. This results in a partial terminal pad of low solder volume. This can cause yield loss and can also result in reliability problems if only enough solder is left to form a partial contact. It is therefore desired to have only the solder vapor, that is, individual atoms and/or small groups of atoms, reach the semiconductor device wafers.