Appendix B
Stencil Design on PCB for
ACPM-7891
0.236 [6.00]
0.2317 [5.52]
In order to dissipate heat, addi-
tional via holes on the PCB are
needed on the printed circuit
board.
0.189 [4.80]
0.142 [3.60]
0.236 [2.40]
0.047 [1.20]
0.000 [0.00]
0.150 [3.82]
0.220 [5.59]
Solder mask should not be
applied to thermal/ground plane
underneath the vias in a way that
will reduce heat transfer
0.043 [1.09]
0.011 [0.26]
efficiency from conductive
paddle to ambient. The stencil
design enables solder paste to fill
up the vias and form a solid
conducting bar that further
improves the thermal dissipation.
A properly designed solder
screen or stencil is required to
ensure optimum amount of sol-
der paste is deposited onto the
PCB pads. The recommended
stencil layout is shown in Figure
B1. The stencil has a solder paste
deposition opening approxi-
mately 90% of the PCB pad.
Reducing stencil opening of the
conductive paddle potentially
generate void underneath, on the
other hand stencil opening larger
than 100% will lead to excessive
solder paste smear across the
conductive paddle to adjacent
I/O pads.
0.022 [0.56]
0.022 [0.56]
Figure B1. Recommended Stencil.
21
HP [ HEWLETT-PACKARD ]
