TC 2.3

Design Improvements for Selective Soldering Assemblies

Selective soldering is, together with pin in paste reflow and press fit, the assemble method for through hole components. The reflow process is limited by component dimensions and heat resistance. Press fit becomes expensive when defects that can’t be repaired. Electronic manufacturing services realize that SMT can’t replace the through-hole technology for 100%.

The selective soldering process offers opportunities to make solder connections on different levels, connecting housing, junction boxes, aluminum parts, stacking PCB’s and more. Designers of new board assemblies could benefit from the special solder nozzles and robot capabilities that modern selective solder machines offer.

Selective soldering can be done under an angle (tilt) like in wave soldering or horizontal with different shape of nozzles and nozzle materials. All have different properties and can be beneficial to solder the most complex assemblies. In order to optimize the production/soldering efficiency assembly engineers should be involved in the Design for Assembly process. Knowledge of Selective Soldering and nozzle technology may offer competitive advantage when implemented in new design and assembly processes.

Studies were done to determine minimum distances to surrounded (SMT) components. What pin to hole ratio gives the best hole filling? How much influence has the flux selection on the soldering results and what nozzles should be used? Historical data is combined with several Design of Experiments looking at solder defects like bridging and process optimizations to achieve the best hole filling.

Hole filling is critical for high thermal mass boards. The thick copper layers absorb a lot of heat from the preheating and liquidus solder. Special design modifications will result in more heat in the solder barrel and will guide the solder to the solder destination side of the board. Together with the right nozzle selection and solder acceleration and deceleration even the most difficult joints will meet the IPC-A-610 classification.

 

如何提升选择性焊接装配的设计

选择性焊接与回流焊pin in paste 和压紧式都属于插入式封装零件组装方法。回流焊接制程会受限于零件的规格和耐热度。压紧式零件却因损坏时无法维修而成本高昂。电子制造服务供应商了解表面安装技术无法百分百代替插入式封装技术。

选择性焊接制程提供相关机会以制造不同层次的焊接,连接元件外壳,接合点,铝部件,多层印刷电路板和其它。新的电路板设计师可以从现代的选择性焊接设备所提供的特制焊锡喷嘴设计与高性能机械手受惠。

选择性焊接可以完成倾斜式波峰焊接或使用不同的喷嘴形状与材料的水平式焊接。两者都有各自不同的特质,对焊接高复杂化的电路装配有帮助。为了更有效的优化焊接制程生产,装配工程师应该投入于装配制程设计。当执行新的设计和装配时选择性焊接与喷嘴科技知识将可以提高竞争优势。

对于表面安装技术元件与周围元件最小的距离已有了相关的研究。多少的贯穿孔与引脚比例是最佳的通孔填充?助焊剂的选择对焊接结果有多大的影响?应该如何选择喷嘴?过去的数据结合数个对于焊接不良有如桥接的实验设计和制程优化可达到最佳的通孔填充。

通孔填充对于高热能容量电子线路板有着非常关键的影响。多层的厚铜板吸收很多来自预热和液化焊锡的热能。特别的改造设计会促成更多的热能留在通孔里从而导致焊锡往电路板上的焊接方向流去。同时配合良好的喷嘴设计和焊锡波峰上下速度的设制,再复杂的焊接都可以达到IPC-A-610 的规格。

 

 

深圳自动化展 深圳自动化展

深圳自动化展 深圳自动化展

深圳自动化展 深圳自动化展

深圳自动化展

深圳自动化展

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