COMPOSITE METAL-CERAMIC TOP PLATE FOR WIREBOND MACHINES
Original Publication Date: 1999-Sep-01
Included in the Prior Art Database: 2002-Aug-26
Today's thermosonic wirebond technology uses a combination of thermal and ultrasonic energy to achieve metallic bonding between a die pad surface, the wire and the metal substrate. The leadframe or metal substrate has to rest on a high temperature top plate for the leads to be at a sufficient temperature for intermetallic diffusion to occur. Current top plate materials and designs allow virtually unhin- dered heat flow from heater block to the leadframe, being constructed from tool steels with relatively high thermal conductivity coefficients. This high temperature environment is vital in the formation of good bonds between the gold wire and the lead- frame. Such designs, however, also place the die and flag area in a high temperature environment which can lead to reliability failures. The key to solving this problem is to design a top plate which distributes heat to the leads where it is needed while protecting the flag area from high temperatures.