New estimation method of wetting and surface tension by measuring area of spreading solder in flux atmosphere based on ellipse approximation of Sessile drop configurations

A method for analyzing the wetting behavior which allows estimation of the movement path and final form of molten solder has been developed. This method is based on an energy analysis which considers the total balance, as opposed to the local balance contact angle method used conventionally for analyzing wetting behavior. In this report, the method is applied to the spreading of solder balls, and the effects of physical properties on wetting behavior are examined. It is found that the physical property which influences the wetting behavior the most is the ratio of wetting tension to surface tension, and this ratio is suitable as a parameter for analyzing soldering defects such as solder bridges