回流技术在通孔双面焊工艺中的新应用

随着表面贴装技术的不断发展，回流技术因其本身独特的优点，已经得到了广泛的应用，并开始逐步应用在传统通孔工艺上。回流焊技术是利用热传输的3种途径（辐射、对流、传导）对待焊接器件、焊料及PCB（印制电路板）加热和冷却，实现焊料溶化、结晶过程，进而完成焊接的技术。目前众多SMT（表面贴装技术）企业没有将回流焊技术应用到通孔焊接工艺中。随着电子产品的日新月异发展，不少通孔双面焊接已无法用波峰焊接技术实现，即使有少数企业采用了通孔双面回流焊技术，也会对器件（特别是镀金长插针）引脚产生焊料涂覆，降低了使用可靠性。文中介绍一种新的、并已实现的解决方案，即用回流技术焊接长针通孔元件。

New Application of Reflow Technology in Double Side Through-hole PCB Assembly

With the rapid development of Surface Mount Technology, the reflow-soldering technique becomes more and more important. It is also being used in the traditional through-hole PCB assembly. Reflow soldering technique basically takes the advantage of heat radiation, convection and conduction to warm up the mounted parts, solder paste and PCB, weld the solder paste, then cool them down to firmly solder the components on the PCB. So far, most of the ESM suppliers have not adopted this technology to the through-hole type PCB assembly yet. With the emergence of new electronics product designs, some of the double sides throughhole PCB cannot be assembled by wave soldering any more. Though some ESM suppliers have tried this technology to double sides through-hole PCB assembly, a solder coating layer was generated on the components （especially for connector with long golden-plated pins） , reducing the reliability of the products. This paper presents an innovate solution to soldering of through-hole parts with long pins with the reflow technology.