Datasheet

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SBAS327A − JUNE 2004 − REVISED SEPTEMBER 2004
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PowerPAD PCB LAYOUT CONSIDERATIONS FOR
THE PCM4204
Figure 19 shows the recommended layer structure for
thermal management when using a PowerPad package
on a 4-layer printed circuit board design. Note that the
thermal pad is placed on both the top and bottom sides of
the board. The ground plane is utilized as the heat sink,
while the power plane is thermally isolated from the
thermal vias.
Figure 20 shows the required thermal pad etch pattern for
the 64-lead HTQFP package used for the PCM4204. Nine
13 mil (0.33 mm) thermal vias plated with 1 oz. copper are
placed within the thermal pad area for the purpose of
connecting the pad to the ground plane layer. The ground
plane is utilized as a heatsink in this application. It is very
important that the thermal via diameter be no larger than
13mils in order to avoid solder wicking during the reflow
process. Solder wicking results in thermal voids that
reduce heat dissipation efficiency and hampers heat flow
away from the IC die.
The via connections to the thermal pad and internal ground
plane should be plated completely around the hole, as
opposed to the typical web or spoke thermal relief
connection. Plating entirely around the thermal via
provides the most efficient thermal connection to the
ground plane.
ADDITIONAL PowerPAD PACKAGE
INFORMATION
Texas Instruments publishes the PowerPAD Thermally
Enhanced Package Application Report (TI literature
number SLMA002), available for download at www.ti.com,
which provides a more detailed discussion of PowerPAD
design and layout considerations. Before attempting a
board layout with the PCM4204, it is recommended that
the hardware engineer and/or layout designer be familiar
with the information contained in this document.
9/20/2004
13mils (0.33mm)
Package
Thermal Pad
Component
Traces
Thermal Via
Component (top) Side
Ground Plane
Power Plane
Solder (bottom) Side
Thermal Isolation
(power plane only)
Package
Thermal Pad
(bottom trace)
Figure 19. Recommended PCB Structure for a 4−Layer Board