STPCI2 查看數據表（PDF） - STMicroelectronics

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STPCI2

X86 CORE PC COMPATIBLE SYSTEM-ON-CHIP FOR TERMINALS

STMicroelectronics 

STPC® ATLAS

When considering thermal dissipation, one of the

most important parts of the layout is the

connection between the ground balls and the

ground layer.

A 1-wire connection is shown in Figure 5-1. The

use of a 8-mil wire results in a thermal resistance

of 105°C/W assuming copper is used (418 W/

m.°K). This high value is due to the thickness (34

µm) of the copper on the external side of the PCB.

Figure 6-32. Recommended 1-wire Power/Ground Pad Layout

Pad for ground ball (diameter = 25 mil)

Solder Mask (4 mil)

Connection Wire (width = 12.5 mil)

t(s) 34.5 mil

Via (diameter = 24 mil)

Hole to ground layer (diameter = 12 mil)

uc 1 mil = 0.0254 mm

rod Considering only the central matrix of 36 thermal

P balls and one via for each ball, the global thermal

resistance is 2.9°C/W. This can be easily

te improved using four 12.5 mil wires to connect to

the four vias around the ground pad link as in

Figure 6-33. This gives a total of 49 vias and a

global resistance for the 36 thermal balls of 0.5°C/

W.

le Figure 6-33. Recommended 4-wire Ground Pad Layout

uct(s) - Obso4 via pads for each ground ball

Obsolete Prod The use of a ground plane like in Figure 6-34 is

even better.

100/108

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