STPCC4HEBI View Datasheet(PDF) - STMicroelectronics
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STPCC4HEBI Datasheet PDF : 93 Pages
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DESIGN GUIDELINES
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 6-27. 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 6-27. Recommended 1-wire Power/Ground Pad Layout
Pad for ground ball (diameter = 25 mil)
Solder Mask (4 mil)
Connection Wire (width = 12.5 mil)
34.5 mil
Via (diameter = 24 mil)
Hole to ground layer (diameter = 12 mil)
1 mil = 0.0254 mm
Considering only the central matrix of 36 thermal
balls and one via for each ball, the global thermal
resistance is 2.9°C/W. This can be easily
improved using four 12.5 mil wires to connect to
the four vias around the ground pad link as in
Figure 6-28. This gives a total of 49 vias and a
global resistance for the 36 thermal balls of 0.5°C/
W.
Figure 6-28. Recommended 4-wire Ground Pad Layout
4 via pads for each ground ball
The use of a ground plane like in Figure 6-29 is
even better.
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Release 1.5 - January 29, 2002
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