STPCE1EDBI View Datasheet(PDF) - STMicroelectronics

Part Name

Description

MFG CO.

STPCE1EDBI

X86 Core General Purpose PC Compatible System - on - Chip

STMicroelectronics 

DESIGN GUIDELINES

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 6-27. 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

Pad for ground ball

diameter = 25 mil

connections = 10 mil

6.4.4.3. Heat dissipation

The thickness of the copper on PCB layers is

typically 34 µm for external layers and 17 µm for

internal layers. This means that thermal

dissipation is not good; high board temperatures

are concentrated around the devices and these

fall quickly with increased distance.

Where possible, place a metal layer inside the

PCB; this improves dramatically the spread of

heat 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

6-28 illustrates such an implementation.

Figure 6-28. Use of Metal Plate for Thermal Dissipation

Die

Board

Metal planes

Thermal conductor

Release 1.3 - January 29, 2002

79/87

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

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