Silicon Image, Inc.

Silicon Image, Inc.

20

Subject to Change without Notice

Stencil Design:

For improved heat transfer, the exposed pad on the package may be soldered to a thermal land on the PCB. This

requires solder paste application not only on the pad pattern for lead attachment but also on the thermal land using

the stencil. While for standard (non-thermally enhanced) leadframe based packages the stencil thickness depends

on the lead pitch and package coplanarity only, the package standoff also needs to be considered for the thermally

enhanced packages to determine the stencil thickness. For a nominal standoff of 0.1 mm, the stencil thickness of 5

to 8 mils (depending upon the pitch) should still provide good solder joint between the exposed pad and the thermal

land. The aperture openings should be the same as the solder mask opening on the thermal land. Since a large

stencil opening may result in poor release, the aperture opening can be subdivided into an array of smaller openings,

similar to the thermal land pattern shown in Figure 14. Recommended Stencil Design. The above guidelines will

result in the solder joint area to be about 80 to 90% of the exposed pad area.

Figure 14. Recommended Stencil Design