Q1 : How to judge the quality of ic chip

One, not on the road detection. This method is performed when ic is not soldered into the circuit. Generally, a multimeter can be used to measure the forward and reverse resistance values of each pin corresponding to the ground pin and compared with the intact ic. Second, in the road detection, this is a method of detecting the ic pins on the road (IC in the circuit) through the multimeter, the DC resistance, the AC-DC voltage and total operating current. This method overcomes the limitations of the substitution test method and the trouble of disassembling ic. It is the most common and practical method for detecting ic. 2. DC operating voltage measurement