Surface Mount Assembly Classifications
Three general classes for the intended end use of electronic assemblies have been established. As applications and functionality increase there may be overlap of equipment between classes. The owner of the application has the responsibility to determine the class that applies. Although a single class may be referenced, specific requirements defined in other classes may apply as well. If a class is not stated for a criterion then the single criterion applies to all classes.
Class 1: Consumer Products: This class of product includes non-critical applications which shall be reliable and cost effective but for which extended life is not the primary objective. Examples include products manufactured for general consumer applications.
Class 2 – General Industrial. This class includes high performance commercial and industrial products in which extended life if required but for which uninterrupted service is not critical. Application and environmental considerations should be taken into account.
Class 3 – High Reliability. Equipment in this class includes those equipment which continued performance is critical, equipment whose downtime cannot be tolerated, or equipment used as a life support item. Unless otherwise specified, Class 3 shall be used for soldering requirements on military electronic equipment.
Printed circuit assemblies are manufactured in a variety of ways, exclusively using smt devices or smt mixed with through-hole components. Boards which have both SMC’s and through-hole components are called mixed technology boards. Surface
mount components are conventionally attached to the substrate using the reflow or the wave soldering process. Typically PCBs are assembled in one of the following ways and categorized as: