NASA-STD 8739.1 is the Workmanship Standard for Polymeric Application on Electronic Assemblies, which describes NASA’s technical requirements, procedures, and documenting requirements for staking, conformal coating, bonding, and encapsulation of printed wiring boards and electronic assemblies. Included are requirements which establish the responsibility for documenting, fabrication, and inspection procedures to be used for NASA work including supplier innovations, special processes, and changes in technology. NASA-STD 8739.1 was initially released in August of 1999, with improvements and minor changes to the standard in recent years. The current up-to-date revision is NASA-STD 8739.1A with Change 2.
NASA-STD 8739.1A with Change 2 is important because it defines the processes and quality requirements needed for mission hardware and mission-critical ground support equipment. There is a certification needed for both operators and inspectors of electronic assemblies which will be used by NASA. I personally attended a five day training course and after two years, a two day retraining course at the Goddard Space Flight Center in Greenbelt, Maryland in which I was issued a diploma that certified me as a Level B instructor which allows me to train operators and inspectors employed at Diamond-MT and any sub-tier contractors of DMT.
NASA-STD 8739.1A with Change 2 is very similar to IPC J-STD-001 when it pertains to the application and inspection of conformal coating. Coating thickness tolerances and what is acceptable in regards to bubbles and scratches in the coating are nearly identical to IPC J-STD-001 with the exception that the NASA standard places strong emphasis on prerequisite vision testing which covers near vision, far vision, and a color test and on not negating the stress relief built into components. i.e.: no coating bubbles or foreign debris is allowed to bridge between the underside of a component or its leads and the circuit card surface.
This was a guest post by James Seeley, Diamond-MT's lead liquid Quality Assurance Inspector.