An impact force compensation algorithm based on a piezo force sensor for wire bonding processes

Impact force control is a key factor in wire bonding processes affecting the overall quality of the product and productivity of the process. This paper presents an impact force compensation algorithm designed for gold wire bonding processes, which uses a piezo force sensor and contains a new algorithm design to reduce the impact force of the capillary when it contacts a silicon pad. This compensation algorithm was developed from an impedance model of the contact between the capillary and pad, and includes automatic drift cancellation calculations for the piezo force sensor. A flat-top impact force profile was achieved using this algorithm with the piezo force sensor attached to the Z-axis of the wire bonder. Tests were used to demonstrate that the proposed algorithm reduced the impact force dramatically, which is particularly important in fine pitch wire bonding processes. (C) 2007 Elsevier Ltd. All rights reserved.