Research On The Wettability Dynamic Testing Method Of Solder Pre-forms

The wettability of solder pre-form will deeply affect the reliability of optoelectronic packaging products. At present, study of solder pre-form wettability testing methods and evaluation parameters are rare, and the current evaluation of the solder wettability has significant limitations to apply in the solder pre-form, so the research of a kind of testing method for solder pre-form is significant.This paper puts forward an innovative dynamic wetting test method. The largest spreading area, wetting time, average spreading speed and instantaneous wetting speed are obtained through the three spreading area-the time, the spreading area-the temperature, and the temperature-the time functions. The larger spreading area indicates the better wettability. But the wetting time and average wetting rate is for the same solder pre-form.In this condition, the shorter wetting time and the faster average wetting rate means better wettability. Instantaneous wetting speed is mainly affected by the temperature, and the changes of wetting speed can suggest the dynamic changes of wettability. In this article, a simple dynamic testing system was designed, including the heating unit, image acquisition unit and the bracket parts. In addition, the three different solder pre-forms experimental results got through this dynamic system showed that the dynamic testing method is feasible. More interesting, we found that Au80Sn20 solder pre-form had a contraction process at the beginning, which was the innovative finding of this dynamic testing method. Finally, in order to develop more perfect testing system, the synchronous dynamic acquisition of the time, spreading area and the temperature is necessary. Besides, corresponding software development is indispensible.