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.



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。




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。



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