Double Thermosonic Ball Bonding Technique
Original Publication Date: 1988-Dec-01
Included in the Prior Art Database: 2005-Feb-15
A technique is disclosed for insuring full wire tensile strength of all wire sets in a wire bonded semiconductor package. A thermosonic wire bonding tool normally leaves a wire ball at the first point of contact, indexes to a termination pad and bonds the wire to that pad before clamping and breaking the wire and forming another ball for the next wire set. Because a wire ball is only deposited at the first point of contact and not at the termination point, care must be taken. Variations in wire orientation under the tool's capillary, surface materials and finishes at the termination bonding site all narrow the process window and result in a thin cross-sectional wire area, as shown in Fig. 1. This results in a highly variable pull tensile strength for each wire set.