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

To avoid solder wicking over to the via pads during

soldering, it is important to have a solder mask of 4

mil around the pad (NSMD pad). This gives a

diameter of 33 mil for a 25 mil ground pad.

To obtain the optimum ground layout, place the

vias directly under the ball pads. In this case no

local board distortion is tolerated.

Figure 6-34. Optimum Layout for Central Ground Ball - top layer

Clearance = 6mil

External diameter = 37 mil

Via to Ground layer

hole diameter = 14 mil

Solder mask

diameter = 33 mil

ct(s) Pad for ground ball

du diameter = 25 mil

ro connections = 10 mil

lete P 6.5.2.3. Heat dissipation

so The thickness of the copper on PCB layers is

b typically 34 µm for external layers and 17 µm for

O internal layers. This means that thermal

- dissipation is not good; high board temperatures

) are concentrated around the devices and these fall

t(s quickly with increased distance.

c Where possible, place a metal layer inside the

u PCB; this improves dramatically the spread of heat

d and hence the thermal dissipation of the board.

The possibility of using the whole system box for

thermal dissipation is very useful in cases of high

internal temperatures and low outside

temperatures. Bottom side of the PBGA should be

thermally connected to the metal chassis in order

to propagate the heat flow through the metal.

Thermally connecting also the top side will

improve furthermore the heat dissipation. Figure

6-35 illustrates such an implementation.

ro Figure 6-35. Use of Metal Plate for Thermal Dissipation

solete P Die

Ob Board

Metal planes

Thermal conductor

101/108

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