Aside from the applied stress created from the indentation of load, it can be deduced that the existence of the copper-based substrate can also act as the pioneer of the formation of pure tin growth. Both samples of different load are stored together in the same ambient temperature but within different phase of storage. Based on the current studies, the formation of pure tin whisker involved the grain boundary sliding motion which start with the critical pressure about -15 MPa 32. Eventually, the stress gradient is created to drive out the pure tin atoms from the surrounding undeformed areas to the base of hillock and push up the hillock outwards.
The thin cover of pure tin solder plating need less time for the movement of intermetallic compound to the pure tin grain boundaries plating to initiate the compressive stress 58. According to Horváth et. al, the manipulation of the size of the pure tin grain will cause the adjustment in the rate of grain boundary dispersion and the level of exerted compressive stress.
4.2.2. Effect of Temperature on the Pure Tin solder.
There are two sample of pure Tin solder dip are placed under indentation of the same load about 200 g are placed at room temperature and at 150 for the period of 240 hours. For the first sample that indented under the 400 g within the room temperature, only several nodules are formed in comparison with the pure tin sample under indentation of 200 g in the 150 oC