别是生产关键应用领域的产品的市场里，此类故障的后果不堪设想。

  对比PCB价格时，铣刀，应牢记这些方面。虽然可靠、有保证和长寿命产品的初期费用较高，但从长期来看还是物有所值

On the surface of PCB， regardless of inner quality. It is through the surface， we didn't see the difference， and the differences of PCB in durability and functionality is crucial in the whole life. In both manufacturing assembly process and in actual use， the PCB must have reliable performance， it is very important. In addition to the relevant cost， the defects in the process of assembly into the final product may be covered by PCB， failure may occur in the process of actual use， result in a claim against you. In that sense， therefore， can never to say that the cost of a high quality PCB is negligible.

In all market segments， especially in the production of key application in the field of product in the market， the consequences of such failure.

Compare the price of PCB， should remember these aspects. Although reliable， guaranteed and the beginning of the long life product cost is higher， but in the long run or value

13、系统原带库Miscellanous Devices.ddb中的DIODE(二级管)封装应该改，也就把管脚说明1(A) 2(K)改为A这样画PCB导入网络表才不会有错误：Note Not Found

   (4)焊盘：焊盘中心孔要比器件引线直径稍大一些。焊盘太大易形成虚焊。焊盘外径D一般不小于(d+1.2)mm，其中d为引线孔径。对高密度的数字电路，焊盘最?直径可取(d+1.0)mm。

SMT常识：

1. 一般来说，SMT车间规定的温度为25±3℃;

2. 锡膏印刷时，所需准备的材料及工具锡膏、钢板﹑刮？﹑擦拭纸、无尘纸﹑清洗剂﹑搅拌刀;

3. 一般常用的锡膏合金成份为Sn/Pb合金，锯片铣刀，且合金比例为63/37;

4. 锡膏中主要成份分为两大部分锡粉和助焊剂。

5. 助焊剂在焊接中的主要作用是去除氧化物﹑破坏融锡表面张力﹑防止再度氧化。

6. 锡膏中锡粉颗粒与Flux(助焊剂)的体积之比约为1:1， 重量之比约为9:1;

7. 锡膏的取用原则是先进先出;

8. 锡膏在开封使用时，硬质合金铣刀，须经过两个重要的过程回温﹑搅拌;

9. 钢板常见的制作方法为﹕蚀刻﹑激光﹑电铸;

10. SMT的全称是Surface mount(或mounting) technology，中文意思为表面粘着（或贴装）技术;

11. ESD的全称是Electro-static discharge， 中文意思为静电放电;

12. 制作SMT设备程序时， 程序中包括五大部分， 此五部分为PCB data; Mark data; Feeder data; Nozzle data; Part data;

13. 无铅焊锡Sn/Ag/Cu 96.5/3.0/0.5的熔点为 217C;

14. 零件干燥箱的管制相对温湿度为 < 10%;

15. 常用的被动元器件(Passive Devices)有：电阻、电容、点感（或二极体）等；主动元器件(Active Devices)有：电晶体、IC等;

16. 常用的SMT钢板的材质为不锈钢;