BOARD LAYOUT

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Release B

This is preliminary information on a new product now in development or undergoing evaluation. Details are subject to change without notice.

A local ground plane on opposite side of the board

as shown in Figure 6-6 improves thermal dissipa-

tion. It is used to connect decoupling capacitances

but can also be used for connection to a heat sink

or to the system’s metal box for better dissipation.

This possibility of using the whole system’s box for

thermal dissipation is very usefull in case of high

temperature inside the system and low tempera-

ture outside. In that case, both sides of the PBGA

should be thermally connected to the metal chas-

sis in order to propagate the heat flow through the

metal. Figure 6-7 illustrates such implementation.

Figure 6-6. Bottom side layout and decoupling

Ground plane for thermal dissipation

Via to ground layer

Figure 6-7. Use of metal plate for thermal dissipation

Metal planes

Thermal conductor

Board

Die