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| 型號： | STPCI2HEYI |
| 英文描述： | PERIPHERAL (MULTIFUNCTION) CONTROLLER |
| 中文描述： | 周邊（多功能）控制器 |
| 文件頁數(shù)： | 64/71頁 |
| 文件大小： | 1071K |
| 代理商： | STPCI2HEYI |
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BOARD LAYOUT
64/69
This is preliminary information on a new product now in development or undergoing evaluation. Details are subject to change without notice.
Issue 2.4 - February 11, 2002
When considering thermal dissipation, the most
important - if not the most obvious - part of the
layout is the connection between the ground balls
and the ground layer.
A 1-wire connection is shown in
Figure 6-2
. The
use of 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.
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 improved by
using four 10 mil wires to connect to the four vias
around the ground pad link, as in
Figure 6-3
. This
gives a total of 49 vias and a global resistance for
the 36 thermal balls of 0.6°C/W.
The use of a ground plane, as shown in
Figure 6-
4
, is even better.
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 can be tolerated.
The thickness of the copper on PCB layers is
typically 34 μm for external layers and 17 μm for
internal layers. The resulting thermal dissipation is
not good, with areas of high temperature being
concentrated around the devices, falling off
quickly with increased distance.
Where possible, place a metal layer inside the
PCB. This will improve dramatically the spread of
heat and hence improve the thermal dissipation of
the board..
Figure 6-2. Recommended 1-wire Ground Pad Layout
Figure 6-3. Recommended 4-wire Ground Pad Layout
Solder Mask (4 mil)
Pad for ground ball (diameter = 25 mil)
Hole to ground layer (diameter = 12 mil)
Connection Wire (width = 10 mil)
Via (diameter = 24 mil)
345ml
1 mil = 0.0254 mm
4 via pads for each ground ball
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相關(guān)代理商/技術(shù)參數(shù) |
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| STPCINDUSTRIAL | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:PC Compatible Embedded Microprocessor |
| STP-CN04 | 功能描述:烙鐵 Cartridge Conical 0.4mm (0.016in) RoHS:否 制造商:Weller 產(chǎn)品:Soldering Stations 類型:Digital, Iron, Stand, Cleaner 瓦特:50 W 最大溫度:+ 850 F 電纜類型:US Cord Included |
| STP-CN05 | 功能描述:烙鐵 Cartridge Conical 0.5mm (0.02in) RoHS:否 制造商:Weller 產(chǎn)品:Soldering Stations 類型:Digital, Iron, Stand, Cleaner 瓦特:50 W 最大溫度:+ 850 F 電纜類型:US Cord Included |
| STP-CN10 | 功能描述:烙鐵 Cartridge Conical 1mm (0.039in) RoHS:否 制造商:Weller 產(chǎn)品:Soldering Stations 類型:Digital, Iron, Stand, Cleaner 瓦特:50 W 最大溫度:+ 850 F 電纜類型:US Cord Included |
| STP-CNB04 | 功能描述:烙鐵 Cartridge Conical Bent 0.4mm (0.016in) RoHS:否 制造商:Weller 產(chǎn)品:Soldering Stations 類型:Digital, Iron, Stand, Cleaner 瓦特:50 W 最大溫度:+ 850 F 電纜類型:US Cord Included |
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