A thermally enhanced plastic package with indented leadframe

A new plastic package with indented leadframe is proposed. The unique feature of the new design is that the die-pad region is indented to expose its bottom surface to the package exterior. The potential advantages of this package design are: 1. the exposed die-pad surface can be soldered to a thermal via in the PCB, providing the shortest possible heat path from the die to the board for the best possible thermal performance. 2. the additional solder joint greatly enhances the mechanical strength and reliability of the PCB assembly. 3. since the die top surface is almost in plane with the bonding pads on the leadframe, the wire bonding process is easier and the wire can be shortened to reduce inductance. 4. being soldered to the PCB, the die-pad region can serve as the best possible electrical ground. In assembly, the exposed die-pad is mounted in the same soldering operation as the leads. Thus, the cost of the above performance improvements is only a few extra stamping steps for the die-pad indention. Comparing to other thermal enhancement features, the present package design can be implemented at lower cost. Finite element analyses of the new package of the same footprint as a 16-lead SOIC double batwing package shows that it compares favorably with the heat slug enhanced SOIC package in terms of thermal performance.