GB1518089A - Optical couplers for electronic circuits - Google Patents

Abstract

1518089 Printed circuits; optical coupler for electronic circuits MARCONI CO Ltd 30 July 1975 [12 Sept 1974] 39759/74 Headings H1K and H1R An optical coupler for interconnecting an input and an output signal comprises (Fig. 1, not shown) a light emissive diode energized through a transistor from an input signal to illuminate aphotodiode whose signal is transistor amplified to produce a proportional output. The coupler comprises two ceramic substrates 20, 22 of which the latter carries transistor TR1 energizing light emitting diode LED on its edge, which illuminates a photodiode PD on the edge of 20 whose output is amplified by transistor TR2; the gap between the edges being filled by clear plastic 18. Metal films defining circuits, e.g. 24, 26 are screen printed on the upper surfaces and edges of the substrates together with the necessary resistors; the conductors being first printed on the surfaces of the substrates and then on to the edges of a pack of such substrates; all cut out by diamond wheels. The diodes are secured to the edges, e.g. by a silver loaded conductive epoxy resin connected to the edge conductors. The substrates are housed in superimposed rectangular frames 12, 14 sandwiching input and output leads 28; to which cover 10 and base 12 are secured; and the unit is then potted in epoxy resin to form a flat pack. In a modification (Fig. 3, not shown) the substrates may carry e.g. 4 similar couplers.