Significant Characteristics require special controls because they are important to customer satisfaction. Severity ratings between 5 and 8 coupled with an Occurrence rating greater than 3 indicate Significant Characteristics. In a design FMEA, they are Potential Significant Characteristics. In the process FMEA, if a special control is required to ensure detection then an Actual Significant Characteristic exists.
Companies have not standardized a method for grouping and denoting Special Product Characteristics. Nomenclature and notation will vary.
With Regard to QS-9000 (now IATF 16949)
The AIAG defines a Special Product Characteristic as a product characteristic for which reasonably anticipated variation could significantly affect a productís safety or compliance with governmental standards or regulations, or is likely to significantly affect customer satisfaction with a product. Ford Motor Company divides Special Characteristics into two categories: Critical Characteristics and Significant Characteristics
Critical Characteristics are defined by Ford as product or process requirements that affect compliance with government regulation or safe product function, and which require special actions or controls. In a design FMEA, they are considered Potential Critical Characteristics. A Potential Critical Characteristic exists for any Severity rating greater than or equal to 9. In the process FMEA, they are referred to as Actual Critical Characteristics. Any characteristic with a Severity of 9 or 10 which requires a special control to ensure detection is a Critical Characteristic. Examples of product or process requirements that could be Critical Characteristics include dimensions, specifications, tests, assembly sequences, tooling, joints, torques, welds, attachments, and component usages. Special actions or controls necessary to meet these requirements may involve manufacturing, assembly, a supplier, shipping, monitoring, or inspection.