Untitled

Power ICs and Power MOSFETs
The PowerPAK SO-8L: A Package
with Thermo-Mechanical Resilience
By Kandarp Pandya
Vishay is adding to its package portfolio with the PowerPAKSO-8L, an AEC Q101 qualified package. Its power cyclingcapabilities at rated temperature ensure the product life cyclein high-power automotive applications where the standardleadless packages can fail for various reasons. The newdesign shares certain characteristics of two previouspackages the high-efficiency, leadless PowerPAK SO-8 andthe industry work-horse DPAK (TO-252) with its heatdissipating tab. Figures 1, 2, and 3 highlight thecommonalities of these three package types.
Fig. 2 - PowerPAK SO-8
Fig. 1 - PowerPAK SO-8L Concept
Fig. 3 - DPAK Bottom and side view
Application Note 913
The PowerPAK SO-8L: A Package
with Thermo-Mechanical Resilience
Vishay performed a design level solder fatigue analysis and otherwise lead to failure of the solder joint either during the characterization using Ansys 9.0 on the SO-8, PowerPAK product life cycle test, the solder joint reliability test, or the SO-8 and PowerPAK SO-8L packages using identical material properties and electrical power/load assumptions.
The recommended minimum PAD pattern for PowerPAK The 2D modeling used 82 structural elements and Visco108 for solder material. The load power cycle ramped from roomtemperature to 125 °C in a minute, stayed at 125 °C for 40minutes, and then returned back to room temperature. The PCB was held in the UX and UY directions in the lower left corner and held in the UY in direction the lower right corner, allowing the PCB to freely expand in the UX direction during thermal expansion. A comparison of thermal fatigue Fig. 5 - Recommended Minimum PADs for PowerPAK SO-8
Single Dimensions in Inches/(mm)
The part overlay over the recommended PAD for single channel PowerPAK SO-8 is shown in figure 6 and the partoverlay over the same recommended single channel PAD for PowerPAK SO-8L is shown in figure 7.
Fig. 4 - Thermal Fatigue Displacement Comparisons
The thermal fatigue displacement of the PowerPAK SO-8 was 72 % higher than the SO-8, while PowerPAK SO-8Ldisplacement was only 24 % higher. In other words, the newpackage design provides for a significant improvement in The gate and source pins in the new package are terminatedlike those on the DPAK, while the package's dimensionalprofile remains the same as the regular PowerPAK SO-8.
The contoured shape of the pins allows them to expand inorder to relieve the thermo-mechanical stress generated bythe mismatch of coefficient of thermal expansion (CET)among the different material elements constituting thedevice, including the silicon die, die attach epoxy, copper lead frame, and plastic mold compound. The pin experiences a spring action in the central portion of its contour as the twoends are rigidly held in its place, one by the moldingcompound and the other by the solder joint on the PC board ICATION NOTE assembly. Thus the thermo-mechanical resilience is built into the package design to eliminate damaging stresses experienced mainly by the solo gate pin, which could Fig. 6 - Single Channel PowerPAK SO-8 on its PAD Layout
Application Note 913
The PowerPAK SO-8L: A Package
with Thermo-Mechanical Resilience
Figures 8 shows the recommended minimum PAD pattern for new designs using the single-channel PowerPAK SO-8L.
The four side leaps are part of different drain tab design. Fig. 7 - Single Channel PowerPAK SO-8L on Single Channel
PowerPAK SO-8 PAD Layout
As figures 6 and 7 indicate, the single-channel PowerPAKSO-8L serves as a drop-in replacement for the Fig. 8 - Recommended PAD for Single Channel
single-channel PowerPAK SO-8, even though the packages Power PAK SO-8L
Dimensions in mm (inches)
Keep-out 6.75 (0.266) x 7.75 (0.305)
The single channel PowerPAK SO-8L is an AEC Q101 qualified package for high-power, high-temperature automotiveapplications. Its key feature is the package's thermo-mechanical resilience, which allows the PowerPAK SO-8L to survive thedesigned life cycle of the application. The single-channel PowerPAK SO-8L serves as a drop-in replacement for thesingle-channel PowerPAK SO-8. Solder joint reliability test using IPC 9701 guidelines will be tested in the future.

Source: http://www.aztronic.cn/docs/64721/an913.pdf