第五讲-1-机柜导热.pptVIP

机箱和电路板的传导冷却 Printed Circuit Boards Printed Circuit Boards A printed circuit board (PCB) is generally a multi-layered board made of a dielectric material (glass-reinforced polymer or FR4) and several layers of copper planes PCB是由FR4和几层铜板构成 It serves to wire mounted IC chips that would otherwise need thousands of point-to-point wire connections A single-layer board has components mounted on one side and copper (conductor) pattern on the other一层板的元件安装在一边，铜线（导热器）在另一边 The copper pattern is established by photo-etching a copper foil pasted over FR4 A double-layer board has copper (conductor) pattern as well as components on both sides 两层板有铜，两边都有元件 A multi-layer board is made of several double-sided boards with insulating layers in between 多层板由几个两层板组成，在层与层之间有绝缘层 Printed Circuit Boards Heat and pressure is applied to laminate the layers into a rigid structure called the PCB 加热和加压而制成一种坚硬的结构叫PCB Multi-layer PCBs generally have 4-10 layers of copper 多层PCBs通常有4-10层铜线 To establish electrical connection between the different components and the copper layers, vias (small holes lined with metal plates) are drilled through the thickness of the PCB 为了使不同元件和铜线层建立连接，通过在PCB厚度上打孔 （vias） The vias may cut through the entire thickness of the PCB or connect a few layers only Vias 可能穿透整个板或只连接几层 In a multi-layer board, some of the copper layers are used to provide ground and power supply voltages, while the remaining layers are used to interconnect the IC chips 多层板中，有些铜线层会用来提供地线和电流电压，而其它的层用来提供IC chips间的连接 Printed Circuit Boards The area coverage of the copper layers can vary between 10% to 90% 铜线层的含量通常在10%到90% The thickness of one layer of copper is about 35 micron or, as is commonly reported in the industry, it contains 1 oz of copper per square foot 一层铜的厚度约在35微米或每平方英尺含1 oz的铜 Components may be mounted on a PCB using 元件可以通过以下方式安装到 PCB上 Though-Hole Technology (THT), or穿孔型 Surface-Mount Technology (SMT)表面安装型 In THT, the legs (pins) of the components pass through holes and a