Temperature Rise at a Constriction in a Current-Carrying Printed Conductor

During the design and manufacture of printed conductors to interconnect electrical circuits, one is often confronted with the task of determining whether an isolated constriction in a printed conductor is of any significance. A constriction is sometimes designed into a printed conductor to help alleviate some particular routing problem. Also, during the manufacturing process, such a constriction can arise in the form of an isolated nick in the printed conductor. In general, the maximum allowable temperature rise at the isolated constriction imposes definite limits on the allowable dimensions of the constriction. The relationship between the dimensions of the isolated constriction and the maximum temperature at the constriction is useful for both design purposes and for determining the maximum allowable nick in a printed conductor. As the maximum allowable nick in a printed conductor is increased, the manufacturing yield increases and the time necessary to visually examine the printed conductor decreases. Thus, the cost of manufacturing printed wiring boards can perhaps be decreased by increasing the maximum allowable nick. 233