STPCI01 STMicroelectronics, STPCI01 Datasheet - Page 63

• Manufacturer Part Number: STPCI01
• Description: STPC INDUSTRIAL - PC COMPATIBLE EMBEDED MICROPROC
• Manufacturer: STMicroelectronics

6. BOARD LAYOUT
6.1. THERMAL DISSIPATION
Thermal dissipation of the STPC depends mainly
on supply voltage. When the system does not
need to work at 3.3 V, it may be beneficial to
reduce the voltage to, for example, 3.15 V. This
may save a few 100’s of mW.
A further area to consider is unused interfaces and
functions. Depending on the application, some
input signals can be grounded, some blocks left
un- powered, other blocks shutdown. Clock speed
dynamic adjustment offers a further solution,
together with the integrated power management
unit.
The standard way to route the thermal balls to the
internal ground layer uses one via for each ball
pad, connected using 8-mil wire.
This is preliminary information on a new product now in development or undergoing evaluation. Details are subject to change without notice.
Note: For better visibility, ground balls are not all routed.
Figure 6-1. Ground Routing
Issue 2.4 - February 11, 2002
With such a configuration, the Plastic BGA 388
package provides 90% of the thermal dissipation
through the ground balls, in particular the central
thermal balls, as these are directly connected to
the die. The remaining 10% of heat is dissipated
through the case. Adding a heat sink can reduce
this value by 85%.
To avoid thermal problems when routing to the
STPC, some basic rules must be applied.
Firstly, the ground balls must be directly
connected to the ground layer, which acts as a
heat sink. This is illustrated in
If one ground layer is not enough, a second
ground plane may be added on the solder side.
Thru hole to ground layer
Pad for ground ball
BOARD LAYOUT
Figure
6-1.
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