Increasing the Conductive Density of Packaging
Wide bandgap (WBG) semiconductor technologies have created new challenges and opportunities for power packages. Developments such as silicon carbide (SiC) and gallium nitride (GaN), have a higher figure of merit (FOM) compared to silicon MOSFETs and have extended the efficiency, output power and/or switching frequency range and operating temperature range for power electronics.
Today’s discrete power packages are limited to the electrical performance of clip, wire and solder interfaces. In general, discrete packaging follows the design philosophy that greater size/volume correlates to higher power handling capability. However, these more efficient transistor technologies provide the ability to handle more power in the same size package or to reduce the form factor significantly.
Figure 1.可用的电源离散功能包括(a)PQFN evolution,(b)ed2pak带散热器标签，
(c)TOLL variations and(d)LFPAK。
To maximize the total conductivity in traditional power packaging, the source and drain need to be connected to current carrying materials at or near 100% of the available space in the die design. Traditionally, this is done by increasing the number of wires, increasing the wire diameter, or maximizing the size of the clip attached to the source or drain.
Table 1.Comparative data on existing power packages.
To maximize both the thermal and electrical properties, it would be preferred to have as much conductive material as possible within the volume of the package. In most power packaging today, the conductive material in the package rarely goes above 25% (refer to Table 1).
New package formats need to be created to maximize conductive density in the package. One concept is the PowerCSP™ technology developed by Amkor. PowerCSP technology is typically in the 40-70% range for conductive density and can be designed in a much smaller form factor than traditional power packages as a result. This increase is due to the use of a continuous Cu substrate instead of a clip or wires.
Figure 3.Simulated comparison of RDS, LDS and Ciss for the PowerCSP™ (PCSP) design to different versions of eD2PAK, TOLL and LFPAK packages.
Other package concepts might be developed specifically for power, but the conductive density of the package will be a key factor. Whether it is Si, GaN or SiC, all can benefit from increasing the conductive density of the package to lower resistance, inductance, and to ultimately reduce the form factor of the package itself. Efforts to increase the conductive density of the package can only help to address the overall power density of the package and allow us to take advantage of all that Si and WBG devices have to offer.
About the Author
肖恩鲍德斯is VP, Mainstream Advanced Package Integration at Amkor Technology Inc., Tempe, AZ. He joined Amkor in 2000 and is currently responsible for package development in automotive, leadframe and power packaging business segments. He previously held technical program management, sales and customer service roles as well. Prior to joining Amkor, he worked for Johnson Matthey Electronics and Honeywell Electronic Materials. He holds a degree in Mechanical Engineering from Gonzaga U.