There is no one definitive way to measure solder quality. Some common methods include: -Measuring the solder flux level. This is a simple, direct method of determining whether or not the solder joint is clean and free of contaminants. -Checking the solder joints for tightness and alignment. This can be done by using a soldering iron and a straight edge to make sure each joint is square and properly aligned. -Checking the soldering temperature.