Short Cuts in Printed-Circuit Wiring

The purpose of this paper is to illustrate the responsibilities of product engineering and design in evolving printed wire products. The short cuts are the results of planning with maximum standardization. The products to be used for illustration are 23 servo-amplifier designs used in military airborne equipment. The quantity of amplifiers to be produced is not large and might be classified as a short-run type production. Printed wiring was decided upon on the basis of reduced unit cost and consistency of amplifier performance. It is important to point out that the products mentioned are part of a large system within a large company. Many of the principles illustrated herein are necessary because of the great coordination a large program requires. A standards department in a large organization determines standard practices, examples of which relative to printed wiring are: 1. Acceptable materials available for printed wiring boards and their properties. 2. Minimum requirements for printed wiring widths and spacing. 3. Types of electrical connections recommended (eg. eyelets, plated holes, and terminals). 4. Minimum component spacing and standard component lead spacing based upon insertion equipment used in the shop. The 25 mil grid coordinate system was adopted based upon studies made by, the RETMA committees and the close packaging requirements generally encountered in Military equipment. The product engineer´s responsibility is to design and test units for production use utilizing information from the standards department.