Philosophy and Practice in Tolerancing Passive Components for Hybrid Circuits in ‘Long Life’ Electronic Equipment

This paper reviews the need for a more realistic and professional approach by UK OEM circuit designers and hybrid engineers to the philosophy and practice of long life—‘total excursion’—tolerancing. It offers simple methods, including offset calculations, for both thick film resistors and multilayer ceramic chip capacitors (X7R), e.g., in B/T Class 1 and Class 2 applications. Acceptance of these principles enables improved product life for the same initial setting (selection) tolerance and width.