SMT的特点
The characteristics of SMT
组装密度高、电子产品体积小、重量轻，贴片元件的体积和重量只有传统插装元件的1/10左右，一般采用SMT之后，电子产品体积缩40%~60%，重量减轻60%~80%。
The assembly density is high, the electronic product is small, and the weight is light. The volume and weight of the patch element are only about 1/10 of the traditional cartridge element. After SMT, the volume of the electronic product is 40%~60% and the weight is reduced to 60%~80%.
可靠性高、抗振能力强。焊点缺陷率低。
High reliability and strong anti vibration ability. The defect rate of solder joints is low.
高频特性好。减少了电磁和射频干扰。
High frequency characteristics. It reduces electromagnetic and radio frequency interference.
易于实现自动化，提高生产效率。降低成本达30%~50%。 节省材料、能源、设备、人力、时间等。
It is easy to realize automation and improve production efficiency. The cost is reduced to 30%~50%. Save materials, energy, equipment, manpower, time and so on.
为什么要用表面贴装技术(SMT)？
Why do we use surface mount technology (SMT)?
电子产品追求小型化，以前使用的穿孔插件元件已无法缩小，电子产品功能更完整，所采用的集成电路(IC)已无穿孔元件，特别是大规模、高集成IC，不得不采用表面贴片元件产品批量化，生产自动化，厂方要以低成本高产量，出产优质产品以迎合顾客需求及加强市场竞争力。
In pursuit of miniaturization of electronic products, the perforated plug-in components used previously can not be reduced and the electronic products have more complete functions. The integrated circuits (IC) used have no perforated components, especially large scale and high integrated IC, and have to use surface patch components to batch products, produce automation, and produce high output with low cost. Produce high quality products to cater to the needs of customers and enhance market competitiveness.
电子元件的发展，集成电路(IC)的开发，半导体材料的多元应用，
The development of electronic components, the development of integrated circuits (IC), the multiple applications of semiconductor materials,
电子科技革命势在必行，追逐国际潮流。
The revolution of electronic technology is imperative and the pursuit of international trends.
为什么在表面贴装技术中应用免清洗流程？
Why do we apply the no cleaning process in surface mount technology?
生产过程中产品清洗后排出的废水，带来水质、大地以至动植物的污染。
In the process of production, the waste water discharged from the product will pollute the water quality, the earth and even plants and animals.
除了水清洗外，应用含有氯氟氢的有机溶剂(CFC&HCFC)作清洗，亦对空气、大气层进行污染、破坏。
In addition to water cleaning, the organic solvent (CFC&HCFC) containing chlorine, fluorine and hydrogen is used for cleaning. It also pollute and destroy the air and atmosphere.
清洗剂残留在机板上带来腐蚀现象，严重影响产品质素。
The cleaning agent remains on the machine plate to cause corrosion and seriously affect the quality of the product.
减低清洗工序操作及机器保养成本。
Reduce the operation and maintenance cost of the cleaning process.
免清洗可减少组板(PCBA)在移动与清洗过程中造成的伤害。仍有部分元件不堪清洗。
No cleaning can reduce the damage caused by PCBA during movement and cleaning. Some of the components are still unbearable.
助焊剂残留量已受控制，能配合产品外观要求使用，避免目视检查清洁状态的问题。
The flux residue has been controlled, which can match the appearance requirements of the product and avoid the problem of visual inspection of cleanliness.
残留的助焊剂已不断改良其电气性能，以避免成品产生漏电，导致任何伤害。
The residual flux has been continuously improving its electrical properties to avoid leakage of the finished product and cause any damage.
免洗流程已通过国际上多项安全测试，证明助焊剂中的化学物质是稳定的、无腐蚀性的。
The washing process has passed many safety tests in the world, proving that the chemicals in flux are stable and non corrosive.
回流焊缺陷分析：
Reflow defect analysis:
锡珠原因：
The cause of tin Zhu:
1、丝印孔与焊盘不对位，印刷不精确，使锡膏弄脏PCB。
1, silk screen holes and pads are not aligned, printing is not accurate, so that solder paste dirty PCB.
2、锡膏在氧化环境中暴露过多、吸空气中水份太多。
2, solder paste exposes too much in the oxidizing environment and sucks too much water in the air.
3、加热不精确，太慢并不均匀。
3, the heating is inaccurate, too slow is not uniform.
4、加热速率太快并预热区间太长。
4. The heating rate is too fast and the preheating range is too long.
5、锡膏干得太快。
5, the solder paste is too dry.
6、助焊剂活性不够。
6, the flux of the flux is not enough.
7、太多颗粒小的锡粉。
7, too many small particles of tin powder.
8、回流过程中助焊剂挥发性不适当。锡球的工艺认可标准是：当焊盘或印制导线的之间距离为0.13mm时，锡珠直径不能超过0.13mm，或者在600mm平方范围内不能出现超过五个锡珠。
8. The flux of flux is not appropriate in the process of reflux. The technical approval of the tin ball is that when the distance between the weld plate or the printed wire is 0.13MM, the diameter of the tin bead can not exceed 0.13MM, or more than five tin beads can not be found in the 600mm square range.
锡桥(Bridging)：一般来说，造成锡桥的因素就是由于锡膏太稀，SMT贴片加工包括 锡膏内金属或固体含量低、摇溶性低、锡膏容易榨开，锡膏颗粒太大、助焊剂表面张力太小。焊盘上太多锡膏，回流温度峰值太高等。
Tin bridge (Bridging): generally, the cause of the tin bridge is because the solder paste is too thin. The SMT patch processing includes low metal or solid content in the solder paste, low shake solubility, easy extraction of tin paste, too large tin paste particles and small welding flux surface Zhang Litai. There are too many solder paste on the pad, and the peak value of reflux temperature is too high.
开路原因：
Reasons for the opening of the road:
1、锡膏量不够。
1, the amount of solder paste is not enough.
2、元件引脚的共面性不够。
2, the component pin's coplanarity is not enough.
3、锡湿不够(不够熔化、流动性不好)，锡膏太稀引起锡流失。
3, tin wet is not enough (not melting, fluidity is bad), solder paste is too thin to cause tin loss.
4、引脚吸锡(象灯芯草一样)或附近有连线孔。引脚的共面性对密间距和超密间距引脚元件特别重要，一个解决方法是在焊盘上预先上锡。引脚吸锡可以通过放慢加热速度和底面加热多、上面加热少来防止。也可以用一种浸湿速度较慢、活性温度高的助焊剂或者用一种Sn/Pb不同比例的阻滞熔化的锡膏来减少引脚吸锡。
4, the pin sucking tin (like rush rush) or near the connection hole. The coplanarity of pins is particularly important for pin spacing and ultra high spacing pin elements. One solution is to pre solder tin on the pad. Pin tin absorption can be prevented by slowing down the heating speed and heating the bottom surface much less. It is also possible to reduce the pin tin absorption by using a slow wetting, high active flux or a solder paste with different proportions of Sn/Pb retarding melting.
SMT有关的技术组成
The technical composition of SMT
电子元件、集成电路的设计制造技术
Design and manufacture technology of electronic components and integrated circuits
电子产品的电路设计技术
Circuit design technology of electronic products
电路板的制造技术
Manufacturing technology of circuit board
自动贴装设备的设计制造技术
Design and manufacture technology of automatic mounting equipment
电路装配制造工艺技术
Circuit assembly manufacturing technology
装配制造中使用的辅助材料的开发生产技术
Development and production technology of auxiliary materials used in assembly manufacturing