以钯作扩散阻挡层——一种多功能线路板表面处理方法

Palladium as Diffusion Bar——A Way to a Multifunctional Printed Circuit Board Finish

电子工业不断的小型化,数种不同互联技术于线路板上电子零件连接及电接点被应用范畴不断增加。基于此用途,线路板组装垫位需被一层最后表面处理保护,如这最后表面处理层可用于不同互联技术,可被称为多功能表面层。钯是一个良好的镍扩散阻挡层,故此层膜能抵受如焊接及键接之严酷老化测试条件。其两大优点为具有良好热超声波键接性及于无铅焊料之非常优良焊接性。从预镀导线架过往多年经验已知即使很薄贵金属钯层及金层已可有保证可靠的金线键接性。从这一知识,沉镍浸钯浸金层膜系统(ENIPIG)被研发出来。此崭新表面处理ENIPIG三种金属镀液需互相配合才能于线路板工艺上达成理想多功能层膜。因着其薄贵金属层膜,相对于其他表面处理,可节省颇大的成本。

Due to the continuing miniaturization in the electronics industry,several different interconnect techniques are used to an increasing extent for the joining and contacting of electronic components on printed circuit boards. For this purpose,the assembly pads of the printed circuit boards are protected with an final surface finishes.If this final finish can be used for different interconnect techniques,it is called a multifunctional finish. Palladium is a good diffusion barrier to nickel. This is the reason why this layer system resists even harsh ageing conditions as regards solderability and bondability.Two big advantages are the good thermosonic bondability with gold wire as well as the excellent solderability with lead-free solders.It has been known for years from the experience with pre-plated lead frames that even very thin precious metal layers of palladium and gold ensure reliable gold wire bondability.From this knowledge, an electroless nickel/immersion palladium/immersion gold layer system （EN/PIG） has been developed. This new final finish ENIPIG,all three metallization baths must be adapted to each other to achieve the desired multifunctional finish on the printed circuit boards.Due to the low thickness of the precious metal coatings,considerable costs can be saved compared to other final finishes.