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44 The PCB Magazine • September 2016 by Steve Williams THE RIGHT APPROACH CONSULTING LLC FOD and the Aerospace Industry FEATURE COLUMN: THE RIGHT APPROACH Introduction Unless you are currently building aero- space product to AS9100 [1] you are probably saying, "What the heck is FOD?" What start- ed out as a requirement to prevent damage to aircraft parts such as engines has been flowed down to any component or assembly includ- ing PCBs. What is FOD? Foreign object debris/foreign object dam- age (FOD) is defined by Boeing [2] as, "A sub- stance, debris or article alien to an aircraft or system, which would potentially cause dam- age." Foreign object debris can lead to foreign object damage. The classic examples of FOD are things like a wrench or other hand tool left in a jet engine after maintenance has been per- formed. From a printed circuit board perspec- tive, it means things that can become a perma- nent part of the product like dirt, dust or other debris that can be entrapped under soldermask or during lamination. It also means surface contamination that could be cleaned off but hasn't been. Why is FOD Important? In an industrial environment, when a part doesn't work the machine may go down. When something malfunctions in an automobile, the occupants have a high chance of survival. When something malfunctions in a plane, the plane goes down and people die. Aside from the human cost, an airplane is probably one of the most expensive pieces of equipment your product can go into. For example, it can cost more than $1 million to overhaul a McDonnell Douglas MD-80 engine after FOD, $10 million to replace it, with the cost of the entire airplane at around $50 million. A Boeing 747-8 costs in excess of $357 million! FOD Area Levels FOD programs typically use a three-tier sys- tem of controls for activities with different titles in work areas. The system described in this doc- ument uses: 1. FOD Awareness Area 2. FOD Sensitive Area 3. FOD Critical Area