I was using STM32F103VET6 (LQFP) for 3 years. At this time, we found some parts' pins were dark and the showed assembly in Philippine. Last lot parts came from Korea which were fine. So we followed AN2639 document to take a test for soldering but they were failed (The same test for Korea assembly parts were passed.) Then we sent to testing lab and Philippine's parts were failed for soldering either. We need some new instruction for settle this case.
I attached 2 photos which are before and after soldering.