Light emitting semi-conductor diode manufacture on printed circuit board involves chip alignment and connection to circuit board and plastic injection onto board in a tool to form light distributor

摘要

One or more light emitting semi-conductor chips(21) are placed on the printed circuit board(10) and aligned with an edge(18) of the board. The chip is then connected to the board to give thermal, electrical and mechanical contact. The circuit board assembly is placed in an injection molding tool and aligned using either the same edge as before or the chip. Plastic is injected into the tool and passes through one or more openings in the circuit board or flows around the latter to form a light distributor(31). The semi conductor chip(21) may be premounted on a chip carrier. During injection of plastic the light emitting semi-conductor chip lies below the printed circuit board and the injected plastic forms one or more light distributors(31), e.g. lenses. The alignment edge(18) forms part of an opening(16) through which plastic flows. Connection of chips to the circuit board is by bonding and/or soldering(22) onto the conductive paths(12,13). Alternatively a bonding wire may be used. For production of several illuminating diodes(20) on a printed circuit board(10) each light distributor is injected via the same runner. Independent claims are included for: a) a method for manufacturing an injection molded illumination unit with at least one light distributor comprising a printed circuit board with one or more chips on one side and openings close to the chips through which the light distributor passes. During injection the material flows normal to the underside of the circuit board and the center of the injected material jet lies below the chips and disperses the flow across the circuit board; b) an illumination unit incorporating a printed circuit board with a light emitting chip and a thermoplastic plastic light distributor contacting the chip or chip group. The light distributor extends through one or more openings in the circuit board and forms gripping ribs on the rear side. Minimum cross-section area of a single rib is not less than10% of the contact area of the light distributor on the chip carrying side and on the chip. The contact area of the light distributor on the rear side of the circuit board is not less than75% of the cross-section area of the rib.