When I worked in the field the book, “Statistical Qualtiy Control” by Grant and Leavenworth was a good textbook. Things have probably changed a lot. Suggest you contact the bookstore at a good university and see what they are using for a textbook now. Also the American Society for Quality Control would probably be a good source. You might want to consider what field you are interested in such as, electronics, computers (software QC is big now), or biomedical. Good luck. PS: The field of QC was sure good to me.

Are you an engineer? And your posting your questions about your job on Yahoo Answers? Man, I’m scared now! You need to monitor the temperature somehow. Cold solder joints are a major failure mode in many electronics. The solder and the base material has to reach a certain temperature for proper adhesion of the solder. Cleanliness is super important. Obviously, the electrode has to make contact in the right spot, also. That’s going to involve some complicated equipment. I’m not sure how it could be done if it’s hand soldering. If done by hand, “conscientious operators” are your best bet. If it’s automated soldering, you can build/integrate equipment to measure temperature at a set period and collect and analyze that data and track the trends. Maybe you could integrate something into the soldering iron than produces an audible “beep” after contact has been made and when the electrode has been on the parts long enough before introducing the solder to the parts (appropriate preheating). Maybe there needs to be a set interval when the equipment needs “cleaned”, like cleaning the electrodes after so many soldered parts. You could design some kind of a test that tests the soldered pieces for strength, like tensile strength. Some kind of “break-off” test. Test pieces randomly and record the data and look for trends. Either a machine could be designed/developed to do this or it could be done manually by hand. I used to resistance weld items together and we had a test, a simple test, where we would “grab” one part of the welded pieces and sort of bend it back and forth until fracture, Then we would look at the broken piece under a inspection scope and make sure the base material broke and NOT the weld. We would do that maybe three times before starting the production run. It was just one test to give the go ahead. There are ,also, “acid tests” that can be performed on the parts. Certain acids can eat away at certain (base) materials, but not weld (in your case the solder or solder interface). Depending on the color of the weld interface after boiling in acid, we could determine of the weld was good or failed. But, that’s a destructive test given before the production run to give confidence about the setup. You have got to set up something where there are regular intervals where the equipment is inspected and checked to make sure it is performing correctly and then documented. I’m pretty sure there are some type of monitors that you can purchase to measure some of the important attributes of a good solder interface. Better make sure the parts are appropriately cleaned before soldering. Do some Googling on “monitor soldering” or “solder monitors” or “solder quality control” or something like that and see what you come up with. Like I said, I’m scared, of whatever is going on where you work. Where do you work? I might want to avoid buying your product for a while until you get this sorted out.