Printed Wiring

a method of wiring electronic apparatus in which the connections between electric and electronic components, including shields, are made by means of fine conductive strips with contact areas that are arranged on a printed circuit board. Printed wiring makes possible a reduction in the size and weight of apparatus and the use of mechanized and automated equipment and highly efficient processes for mass production. In addition, the reliability of the items is improved, and material outlays and labor costs are reduced.

Printed conductors are produced by etching metal-clad insulating material, by electrochemical deposition, by vacuum or cathode sputtering, by baking on conductive inks, and by electroplating, with transfer of the conducting pattern to an insulating board. The image of the printed conductors is printed on a board by photographic, offset, and screening methods, as well as molding, and embossing. Continuity of contacts between the two sides of a board is produced by plating the walls of the holes or by inserting metal tubes, which are subsequently flared and soldered. The conductors in printed wiring are usually 20–50 microns thick and 0.5–0.8 mm wide; the minimum distance between conductors is 0.3–0.5 mm. As a result of favorable heat-removal conditions, high current density (up to 30–50 amperes per sq mm) is permissible in printed conductors. Multilayer printed-circuit boards are used for microminiaturization of apparatus based on multiple-output integrated circuits, thus achieving a substantial increase in circuit density.