A light emitting diode (LED) is a type of semiconductor device that emits a visible light when biased in the forward direction. Lamps incorporating such LEDs as their light source are referred to as LED lamps. Due to their construction, LED lamps are typically smaller than standard neon type lamps, making their use particularly desirable in applications where a premium is placed on space, such as advertising signs and lighted building fascia. Additionally, the LED is energy efficient in that it only requires a small amount of electricity in order to generate a relatively strong light. Therefore, the LED is a particularly desirable lighting source in applications where energy efficiency is important, such as large outdoor advertising signs that typically consume large amounts of electrical energy.
Generally, LED lamps offer a relatively high degree of illumination for their size. LED lamps must usually be combined with other LED lamps in order to achieve the same degree of illumination as a light assembly illuminated by standard neon tubes. The combination of LED lamps typically occupies less space and requires less energy to operate than that of the standard neon type lamps they replace. The space saving and energy efficient features of the LED make it a popular choice with designers who are motivated to reduce the size and/or increase the efficiency of the light source used in their products.
Recently, LED lamps have found application in the signage industry as a source of illumination, replacing standard neon type lamps, for exterior lights, such as channel letters, lighted fascias and the like. It is highly desirable that the light source used in the signs be energy efficient. The LED is a popular choice in such an application because its use permits the replacement of standard neon type lamps that require a larger space and consume a greater amount of energy to operate.
The standard neon type lamps are known to have a high rate of failure when used in a sign application. The high failure rate is attributed to the glass tube breaking due to sudden shocks or bumps experienced under normal manufacturing or shipping conditions. Unlike standard neon type lamps, LED lamps are immune to such failures due to their inherent construction. The light emitted by an LED is caused by the generation of photons from materials within the LED and is not the product of an electric current passing through an illuminating gas. Since the LED does not rely on the glass tube scheme used in neon type lamps, it is better suited for use as a reliable lighting source.
Additionally, standard filament bulb type lamps are known to generate a large amount of heat during their operation. The heat generated by standard filament bulb type lamps not only shortens the life of the light source but may cause thermal damage, deformation, cracking or the like to other nearby lighting elements, such as the deformation or cracking of a nearby plastic lens.
LED modules comprising a plurality of LED lamps are known in the art. Such modules are generally made up of a plurality of LED lamps, each having an anode and cathode lead and a printed circuit board with conductive paths. The plurality of LED lamps are each connected to the printed circuit board by soldering the anode lead of each LED to one path and soldering the cathode lead of each LED to another path. The LED lamps may be arranged along the printed circuit board as desired in order to meet the illumination, space and configuration requirements of the particular light assembly. The LED module is mechanically attached to the light assembly and the printed circuit board is electrical connected to an anode or cathode electrical source within the light assembly.
LED modules known in the art have attempted to minimize the potential for thermal damage to the LED lamps by constructing the LED leads from materials having a low thermal conductivity, such as steel. Using materials of low thermal conductivity reduces the amount of heat that can be transferred from the solder site to the LED chip itself. However, materials having low thermal conductivity necessarily have a correspondingly low electrical conductivity. Therefore, the methods used in the art to minimize the thermal damage of the LED lamps during the soldering operation has resulted in the construction of a LED module that does not display optimal electrical efficiency. Additionally, LED leads constructed from such low thermal conductivity materials effectively limit the amount of power that the LED can dissipate and remain within reliable operational parameters.
Mounting LED lamps on a printed circuit board is also costly. Each LED must be individually positioned on the board for assembly. The boards themselves are costly. Accordingly, a different approach for connecting LED lamps is desirable for both reducing the cost of an LED module and increasing the electrical efficiency of an LED module.
It would be desirable to have an LED module that can accommodate a plurality of LED lamps in a manner that will optimize the reliability of each LED. It would be desirable that the mounting of LED lamps in the LED module promote optimal electrical and thermal efficiency. It would be further desirable that the LED module permit arbitrary spacing of each LED in order to correspond to predetermined shapes or illumination requirements. It would be also desirable that the LED module be practical to produce from both an economic and manufacturing standpoint.