With the size of DC-to-DC converters continuing to shrink, it has become a challenge to dissipate the heat generated by various components on the PCB.
Advances in packaging need to be developed in tandem with silicon technology improvements. The PolarPAK package, with its superior thermal handling capability, represents a remarkable evolution in assembly technology allowing designers to increase efficiency and power density.
This package technology will complement ST’s range of STripFET MOSFETs optimized for power conversion in computer, datacom, and telecom applications.
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Excellent Heat Dissipation |
ST’s latest low voltage technology, “STripFET™ III” brings unbeatable value with silicon-inherent on-resistance and total gate charge. Both of these parameters are very important factors for achieving the highest efficiency, but without the appropriate packaging solution the overall design is simply not complete.
More power in the same sized or smaller package can be obtained by reducing the thermal resistance, and add more exposed metal to the device design, in order to enhance its thermal dissipation.
ST has offered various solutions comparable in size to the SO-8 package. For example the PowerSO-8 and PowerFLAT5x6 both provide a low thermal resistance path from the die to the PCB via a metal pad placed at the bottom of the package.
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The new package’s leadframe and plastic encapsulation are similar to those used for most standard power MOSFET packages, ensuring good die protection and easy handling in manufacturing. Yet compared with the standard SO-8, the metal-topped PolarPAK package dissipates heat so efficiently from both the top and the bottom of the package that it can handle twice the current within the same footprint dimensions.
With a footprint no larger than a standard SO-8 or PowerFLAT5x6, this new package allows increased power handling with just a simple forced-air cooling system. Further improvement is also possible with a low-cost heat sink placed on the top of the package.
The power handling capability of the PolarPAK is 30% higher than the PowerFLAT5x6, and 73% higher than the PowerSO-8.
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 Top and bottom heat dissipation paths;
Fully encapsulated silicon;
Same footprint as standard SO-8 packages;
Low profile package (0.8 mm);
Superior thermal performance;
Multiple sourcing.
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P / N |
PD
[W] |
Rthi-pcb
[°C/W] |
Rthj-c
(bottom)
[°C/W]
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Rthj-c
(top)
[°C/W] |
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PolarPAK |
5.2 |
24 |
2.7 |
1 |
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PowerFLAT5x6 |
4 |
31.2 |
1.56 |
16 |
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PowerSO-8 |
3 |
42 |
1.8 |
18 |
PolarPAK Superior Thermal Performance Compared to the PowerFLAT5x6 and PowerSO-8 Packages
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PolarPAK package technology complements ST’s extensive selection of STripFET MOSFETs which are optimized for power conversion in computer, datacom, and advanced telecommunications applications. Specifically, these new products are designed for high frequency DC-to-DC converters used to power the next Intel® and AMD processors designed into high-end notebooks and servers.
With the introduction of ST’s PolarPAK, there is now a broad range of products available to fulfil any kind of customer requirements, from the standard SO-8 to the new double-sided cooling package. This flexibility is a great advantage for the customer who really has to have the suitable, comprehensive solution. |
The first devices specifically designed for the PolarPAK frame will be:
STK800 With its low capacitance and total gate charge, the STK800 represents the ideal choice as a control FET in non-isolated DC-to-DC step down converters;
STK850. Due to the low RDS ON, the STK850 is the best solution as a synchronous FET.
The PolarPAK package product range will soon include other options, such as different voltage breakdown values. |
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Sales
Type |
ID
[A] |
RDS(ON)
@ 10Vmax
[Ohm] |
RDS(ON)
@ 4.5Vmax
[Ohm] |
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20 |
0.007 |
0.0105 |
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30 |
0.0035 |
0.0043 |
ST provides a full range of package options:
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Package |
SO-8
Fully molded |
PowerSO-8
Bottom side cooling pad |
PowerFLAT5x6
Bottom side cooling pad |
PolarPAK
Double side cooling pads |
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PolarPAK is a registered trademark of Siliconix incorporated
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