參數(shù)資料
型號: STPCELITE
廠商: 意法半導(dǎo)體
英文描述: X86 Core General Purpose PC Compatible System - on - Chip
中文描述: x86內(nèi)核兼容的通用計算機(jī)系統(tǒng)-關(guān)于-芯片
文件頁數(shù): 79/87頁
文件大小: 1356K
代理商: STPCELITE
DESIGN GUIDELINES
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.
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.
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
dissipation is not good; high board temperatures
are concentrated around the devices and these
fall quickly with increased distance.
means
that
thermal
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
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.
and
low
outside
Figure 6-27. Optimum Layout for Central Ground Ball - top layer
Via to Ground layer
hole diameter = 14 mil
Pad for ground ball
diameter = 25 mil
connections = 10 mil
Clearance = 6mil
External diameter = 37 mil
Solder mask
diameter = 33 mil
Figure 6-28. Use of Metal Plate for Thermal Dissipation
Metal planes
Thermal conductor
Board
Die
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