Vishay Siliconix

AN822

Document Number 71681

03-Mar-06

www.vishay.com

1

Johnson Zhao

MOSFETs for switching applications are now available

with die on resistances around 1 m

Ω and with the

capability to handle 85 A. While these die capabilities

represent a major advance over what was available

just a few years ago, it is important for power MOSFET

packaging technology to keep pace. It should be obvi-

ous that degradation of a high performance die by the

package is undesirable. PowerPAK is a new package

technology that addresses these issues. The PowerPAK

1212-8 provides ultra-low thermal impedance in a

small package that is ideal for space-constrained

applications. In this application note, the PowerPAK

1212-8’s construction is described. Following this,

mounting information is presented. Finally, thermal

and electrical performance is discussed.

THE PowerPAK PACKAGE

The PowerPAK 1212-8 package (Figure 1) is a deriva-

tive of PowerPAK SO-8. It utilizes the same packaging

technology, maximizing the die area. The bottom of the

die attach pad is exposed to provide a direct, low resis-

tance thermal path to the substrate the device is

mounted on. The PowerPAK 1212-8 thus translates

the benefits of the PowerPAK SO-8 into a smaller

package, with the same level of thermal performance.

(Please refer to application note “PowerPAK SO-8

Mounting and Thermal Considerations.”)

The PowerPAK 1212-8 has a footprint area compara-

ble to TSOP-6. It is over 40 % smaller than standard

TSSOP-8. Its die capacity is more than twice the size

of the standard TSOP-6’s. It has thermal performance

an order of magnitude better than the SO-8, and 20

times better than TSSOP-8. Its thermal performance is

better than all current SMT packages in the market. It

will take the advantage of any PC board heat sink

capability. Bringing the junction temperature down also

increases the die efficiency by around 20 % compared

with TSSOP-8. For applications where bigger pack-

ages are typically required solely for thermal consider-

ation, the PowerPAK 1212-8 is a good option.

Both the single and dual PowerPAK 1212-8 utilize the

same pin-outs as the single and dual PowerPAK SO-8.

The low 1.05 mm PowerPAK height profile makes both

versions an excellent choice for applications with

space constraints.

PowerPAK 1212 SINGLE MOUNTING

To take the advantage of the single PowerPAK 1212-8’s

thermal performance see Application Note 826,

Recommended Minimum Pad Patterns With Outline

Drawing Access for Vishay Siliconix MOSFETs. Click

on the PowerPAK 1212-8 single in the index of this

document.

In this figure, the drain land pattern is given to make full

contact to the drain pad on the PowerPAK package.

This land pattern can be extended to the left, right, and

top of the drawn pattern. This extension will serve to

increase the heat dissipation by decreasing the ther-

mal resistance from the foot of the PowerPAK to the

PC board and therefore to the ambient. Note that

increasing the drain land area beyond a certain point

will yield little decrease in foot-to-board and foot-to-

ambient thermal resistance. Under specific conditions

of board configuration, copper weight, and layer stack,

experiments have found that adding copper beyond an

ment in thermal performance.

Figure 1. PowerPAK 1212 Devices