Your CM should work continually to maintain their certifications annually to meet national and global standards for quality contract manufacturing and excellence of service. ISO certification ensures that contract manufacturers meet certain regulatory standards for production quality and employee support. Your CM should follow the IPC J-STD-001 standard for soldering, IPC-A-610 for electronic assembly, and IPC – 7711/7721 for rework/repair modifications. Additionally, your specific product industry will also have key certifications to look for – ISO 13485 and FDA for medical devices, ITAR for defense, etc. As a reference, Cirtronics list of certifications can be found here.