Effect of reflow profile parameters on surface mount chip resistor solder joint shear strength.

Abstract

The focus of this study is on the effect of reflow parameters on the joint shear strength. Eight reflow profiles were developed using four factors at two levels of Taguchi design of experiment for 1206, 0805 and 0603 chip resistors. Normal probability and main effect plots were used to provide a complete profile of the effect of reflow parameters on the chip resistor solder joint shear strength. The Normal Probability plots show effect of some reflow parameters on shear strength. Some data points did not fall on the best fit line.These outliers indicate parameter effects. The 1206 chip resistor shear strength value of 74.85N lies outside the best fit line indicating that some of the parameters are critical and significantly affect the response value. The results of the Main Effect plots help identify the unknown critical parameters in the probability plots. It indicates that the shear strength of 1206 chip resistor depends on the peak temperature, time above liquidus and preheat slope but not on cooling rate. In the case of the 0805 chip resistor, there were no exceptional departures from the line fitted to the data. It can be assumed that the factors and the levels considered here have no significant effect on the response. The normal probability plot of the 0603 chip resistor shows that the 46.68N shear strength lies outside the fitted line. This means that the factors and settings (run 3) can be further modified to improve the response. The factors which affected the 0603 resistor from the main effect plot are preheat slop and cooling rate.The results of the 1206 chip resistor show the highest shear force of 74.8 N using a peak temperature setting of 230°C (low level). The 0805 and 0603 chip resistors recorded the highest shear forces of 68.32N and 46.48 respectively using a temperature of 245°C (high level). The higher temperature may have contributed to the lower shear force due to the growth of brittle intermetallic compound in the case of the 0805 and 0603 chip resistors.