It is conventionally known to provide a light emitting module comprising one or more light sources without using a printed circuit board, where the light sources are attached directly between a plurality of conductors extending substantially in parallel (see, e.g., U.S. Pat. No. 5,519,596). In the light emitting module shown in U.S. Pat. No. 5,519,596, a plurality of bus bar pairs are connected via electroconductive extendable joints, and a plurality of LEDs serving as light sources are connected between each bus bar pair by clinching, soldering, spot-welding or the like, to form a so-called matrix circuit comprising a plurality of LED parallel-connections that in turn are connected in series. Before attachment of the LEDs, the bus bars in each pair are connected to each other by integral connection pieces, which, after the attachment of the LEDs, are cut off so as not to short-circuit the LEDs.
The light emitting module fabricated by attaching the LEDs directly onto the conductive bus bars can obviate the use of a printed circuit board, and thus can be manufactured at a reduced cost. Further, the light emitting module has a favorable heat dissipation property because heat can be dissipated efficiently from the exposed bus bars and extendable joints. However, in such a light emitting module, the bus bars in each bus bar pair are mechanically connected to each other by the LEDs, and this can result in stress being imposed upon electrical connections between the bus bars and the LEDs and may undesirably lead to faulty electrical connections. Such a problem tends to be caused particularly when the light emitting module is being carried and thus makes the handling of the module cumbersome.
Japanese Patent Application Laid-Open (kokai) No. 2000-260206 has disclosed processing a metallic sheet into a plurality of bus bar pairs extending in parallel and connected together by joint portions at either ends, attaching light emitting elements mechanically and electrically between each pair of bus bars at predetermined positions by means of clamping, for example, and cutting off part of the joint portions connecting the bus bar pairs to form a flexible light emitting module. In thus formed light emitting module also, the bus bars in each bus bar pair are connected to each other by the light emitting elements (LEDs), and therefore, contains a problem that the stress imposed on the electric connections between the bus bars and the light emitting elements can cause faulty electric connection.
Japanese Patent Application Laid-Open (kokai) No. 2000-10507 has disclosed punching a metallic sheet by means of a punch press machine or the like to form a lead frame comprising a plurality of electrode terminals, to which LED chips are attached, where the electrode terminals are spaced apart from each other at a predetermined interval, subsequently molding a box-shaped reflection case onto the lead frame such that the reflection case covers top and under sides of the lead frame while exposing surfaces of the electrode terminals, and mounting LED chips onto the electrode terminal surfaces by die bonding to whereby manufacture a light emitting display device. In order to prevent warp of the lead frame when molding the box-shaped reflection case, an upper surface of the reflection case is formed with a plurality of pairs of arcuate projections such that each projection pair is aligned with a corresponding LED chip and interposes the LED chip therebetween, and a lower surface of the reflection case is formed with notches at positions between the projections. In this device, the reflection case serves to mechanically support the lead frame, and thus reduces an amount of stress imposed on electric connections between the LED chips and the lead frame. However, the reflection case extending an entire length of the light emitting display device and covering the top and under surfaces of the lead frame hinders heat dissipation as well as makes the device difficult to bend or curve. Further, the light emitting display device uses wire bonding to achieve attachment of the LED chips, and this makes it difficult to achieve attachment of a chip-type LED (or surface mount-type LED), which has electric connection terminals integral with a substantially box-shaped main body and thus has no leads.