Method of producing a lamp

A method of producing a lamp is disclosed. The method provides for mounting light emitting junctions on a support structure such that the junctions adopt a three-dimensional array.

FIELD OF THE INVENTION

The present invention relates to a method of producing a lamp, particularly an LED lamp, and a lead frame for use in the lamp.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a method of producing a lamp. The method of the present invention provides for mounting light emitting junctions on a support structure such that the junctions adopt a three-dimensional array.

Preferably, the method further comprises locating the junctions in respective recesses formed in the support structure, the recesses functioning as an optical guide for controlling a direction of light output from the associated junction.

Preferably, the support structure comprises a plurality of conductors and the method further includes forming the conductors in a curved configuration, which is preferably a part spherical configuration.

Preferably, the conductors are provided in the form of a lead frame.

Preferably, the method further comprises moving the lead frame relative to a forming station and engaging a punch and die, from opposed sides of the lead frame, to form the recesses. The recesses may be formed in a single action or, alternatively, formed sequentially, with the punch and die being moved relative to the lead frame after each recess forming action so that the punch and die are appropriately positioned for a subsequent recess forming action.

Preferably, the lead frame is supported on a carrier and the method comprises moving the carrier so as to present each recess to a mounting station whereat the junctions are mounted to the conductors. The carrier is preferably rotatable about first and second orthogonal axes to align the respective recess with the mounting station and the junctions are mounted in the respective recesses by advancing the junctions and associated conductors relative to each other along a third axis, which is preferably orthogonal to the first and second axes.

Each junction is preferably electrically connected to two of the conductors via intermediate conductors. The intermediate conductors may be connected to allow for independent control of at least two of the junctions, by controlling electric current through the associated conductors, to which each junction is connected. The junctions may further be electrically coupled to the conductors in groups which are separately controllable.

The method preferably comprises application of a common phosphor over at least two adjacent junctions and, more preferably, encapsulation of the support structure and junctions, in a globe portion.

In another aspect, there is provided a lead frame comprising a plurality of conductors formed in a curved configuration, for supporting light emitting junctions in a three-dimensional array. The lead frame preferably includes recesses for receipt of a respective one of the junctions.

In another aspect, there is provided a lamp formed in accordance with the above-described method.

In yet another aspect, there is provided a method of operating the above described lamp, formed with conductors and light emitting junctions electrically connected therebetween, including controlling electrical current through individual ones of the conductors so as to independently control light output from the junctions coupled thereto.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

In accordance with an exemplary embodiment of the present invention, the lamp1, as shown inFIG. 1, includes a globe portion2with a cylindrical base3and a parabolic end4, configured to enhance illumination output in an axial direction of the lamp. The lamp also includes first and second terminals, which are preferably in the form of conductors5,6which are embedded within the globe portion2. The terminal5has a support platform7to which is mounted an integrated circuit wafer8. In the example given, the wafer includes two junctions which are arranged substantially adjacent to each other so that a common layer of fluorescent material, such as a phosphor layer, may be applied over both junctions. Intermediate conductors9to12electrically couple the junctions to the respective terminals5,6so that the LED junctions14,15are arranged in reverse polarity, as indicated in the circuit diagramFIG. 3. A resistive element16is provided between a further conductor13(connecting the intermediate conductors11and12) and the terminal5.

The conductors5,6, intermediate conductors9to13, and wafer8are all embedded within the globe portion2so that the lamp is presented as a robust unitary structure. The reverse polarity of the junctions allows the lamp to be connected to a power source without concern for polarity, as compared to the case with a conventional LED arrangement. The use of a single phosphor layer, common to each of the junctions, also simplifies manufacture and provides an aesthetic advantage in that the light from either junction is perceived to originate from a single source.

In a preferred form of the LED lamp, the following specifications may apply:

It should, however, be appreciated that the size configuration and operating parameters of any of the component parts of the lamp may vary, as required and the number of LED junctions may also be increased to suit illumination needs.

An exemplary embodiment of a second lamp20is now described with reference toFIGS. 4 to 8. The lamp20is generally similar in construction to that ofFIGS. 1 to 3, in sofar as first and second terminals21and22are provided, in the form of conductors23,24embedded in a globe portion25, together with additional conductors26,27. Each of the conductors23,26and27have a respective recess28, to provide support structure for receiving an associated junction, indicated by reference numerals29,30,31. The junctions are covered by a common layer of phosphor35and are electrically coupled between each respective conductors23,26,27to which they are mounted, and the adjacent conductor via intermediate conductors32,33,34. In the example shown, the junctions are serially connected, as represented by the circuit diagram ofFIG. 5.

All of the conductors23,24,26,27are preferably formed in a two dimensional lead frame structure40shown inFIG. 6, to allow ease of manufacture and reliability in directly positioning the junctions29,30,31before application of the phosphor layer35within and before application of the globe portion25. As can be seen from bothFIGS. 6 and 7, the junctions29,30,31are preferably arranged in a generally linear array, with the conductors23,27projecting above the conductor26so that the overall illumination generated by the junctions will be somewhat enhanced on-axis, as represented inFIG. 8by curve A.

In another exemplary embodiment, the lamp20may also be provided with a lens41which is fitted to the globe portion25and shaped so as to modify the light generated by the lamp to produce, for example, the illumination pattern represented by curve B inFIG. 8, whereby the output illumination is somewhat more evenly distributed.

Turning now toFIGS. 9 to 16, in another exemplary embodiment, a third lamp50is illustrated. Again, the lamp50is in general similar to the previous lamp construction insofar as a plurality of conductors51,52,53and54are embedded within a unitary globe portion55and have light emitting junctions56mounted in respective recesses57and covered by a common layer of fluorescent material59. Each junction is again electrically coupled to the respective conductor to which it is mounted and an adjacent conductor via intermediate conductors58so as to form the circuit illustrated inFIG. 10. Each of the conductors51to54, in this instance, however, carrying three junctions56.

The conductors51to54are curved within the globe portion55so as to support the junctions on an imaginary curved surface such as a spheroid and, in that manner, the illumination generated by the lamp50will have an appearance of emanating from a small, generally spheroid point like source. A lens60may also be provided for modifying the output of the junctions to produce a more even distribution pattern such as represented by curve C inFIG. 16, which is the illumination output observed from a plan view of the lamp50, i.e. when the lamp is seen from the same direction as viewed inFIG. 9.

In addition to modifying the light output by using the lens60, it is also possible to arrange the conductors in any desired configuration and the construction of the recesses57may also be used to assist in controlling the directional output of the light emitted from the various junctions. In particular, the configuration of each recess may be such that for example, the recess side walls act as optical guides to control the direction and/or angle of divergence of light emitted from each junction.

More specifically, the shape of each recess and its effect on the light output from the junctions will now be described in more detail with reference toFIGS. 14 and 15, which show cross-sectional views of the relevant conductors taken along the lines X—X and Y—Y shown inFIGS. 11 and 12respectively.

The recesses57containing the LED junctions are positioned and shaped in the conductors51,52,53so that the beams of light emerging from the recesses may be combined in free space outside the lamp50in predictable patterns determined by the radius of the imaginary part spherical surface designated ‘R’, the distance from the LED junction in the recess to the intersection of the imaginary extension of the sides of a recess—designated ‘r’ and the angle ‘A’ between the centre line61of the lamp50and a centre line62passing through the perpendicular to any other LED junction.

The radius ‘R’ of the imaginary spherical surface is the distance from the intersection of those centre lines to the LED junction within the recess. The angle between the sides of a recess determines the value of the ‘r’.

In the limiting case where ‘r’ is equal to or greater than ‘R’, the light from each LED junction will be shaped by the recesses into beams which do not cross, regardless of the value of angle ‘A’. For all values of ‘r’ less than ‘R’ it will be possible to have the light beam from each LED junction coincide with the edges of the light beams from adjacent LED junctions. The exact positioning in this instance will be determined by the ratio R/r and the value of angle ‘A’.

As may be appreciated, the above described lamps allow considerable scope for obtaining a light source using junction diodes, with a predetermined one of a variety of output illumination patterns whilst maintaining a generally simple construction. A particular advantage is that the various junctions are of small size and may be configured to produce a light output which may be perceived by the naked eye to be emanating from a single point source of light.

A method of producing a lamp is now described, with reference toFIGS. 17 to 24. In an exemplary embodiment the method includes three main stages: stage100is the formation of a suitable lead frame; stage101is the attachment of junctions to the lead frame; and stage102is the final packaging stage.

Stage100includes provision of a flat lead frame, at step103, formation of conductors of the lead frame into a part spherical surface, at step104, and the formation of recesses in the conductors, at step105, followed by surface treatment step106.

FIG. 18shows a lead frame110, between steps104and105. The lead frame110is provided in a generally elongate strip111, divided into sections112, which will ultimately be separated to form individual lamps. Each section112includes a plurality of conductors113,114,115formed into a curved configuration which is preferably part spherical. The conductors may be formed in that configuration by any suitable process such as by inserting the strip111in a press or the like.

In order to form the recesses, the part spherical portion of the lead frame is fitted over a correspondingly shaped tool116, at a forming station, where a punch (not shown) is engaged with the conductors113,114,115, from an opposite side of the lead frame to that of the die, to form recesses in the conductors by action of the punch deforming the conductors into an associated die117provided in the tool116. The recesses may be formed sequentially and for that purpose, the tool is preferably rotatably movable relative to the lead frame so that the die can be rotated to any desired position where a recess is required. In that manner, a single punch, which is rotated in unison, and die117can be used to form all of the recesses in any desired array. Alternatively, the tool116may have a predefined array of die117and the punch configured appropriately so that all of the recesses are formed in a single action. The particular positioning and configuration of the recesses can be selected to optimise output, as required, since the recesses act as optical guides, as discussed above specifically in relation toFIGS. 9 to 16, to define the directional output while the number of recesses will determine the maximum output intensity.

In any event, the lead frame110, can be mounted on a carrier119, as shown inFIG. 19, for stage101, where light emitting junctions are mounted in the recesses120. The carrier119is itself rotatable on a shaft121, for pivotal movement about an x-axis, and a shaft122, for pivotal movement about a y-axis. As such, the lead frame can be positioned at a mounting station (not shown) and rotated about the x,y axes relative to the mounting station in order for each one of the recesses120to be sequentially presented for receipt of an associated junction.FIG. 20shows a cross-section of one of the stations112and, in particular, the part spherical configuration of conductor114. A curve123represents the possible path of spherical translation of the conductor114which is achievable by rotating the lead frame110about axes121,122. Line124represents an equivalent rotation of the tool116away from the z-axis, which in turn defines the operating angle125within which recesses120may be formed.

When each of the recesses is appropriately presented at the mounting station, the associated light emitting device or die, referred to for simplicity as junction130, as shown inFIG. 21, is inserted into the recess along a third axis, which is preferably in a z-axis direction, and bonded in place in accordance with step107of stage101of processing. At that time, or subsequent thereto, intermediate conductors131are attached at step108to electrically connect the junctions to adjacent conductors. The junctions shown inFIG. 21are arranged in an electrically parallel configuration, however, the positioning and coupling of the junctions may be in any desired configuration, such as shown inFIG. 22, where each junction is coupled to a common central conductor114and a separate radially arranged conductor132to allow the light intensity from each of the junctions to be separately controlled by independently controlling the power supplied to the conductors. Another possible configuration of recesses120is shown inFIG. 23. In any of the configurations, various ones of the junctions can be electrically connected in groups so that the light intensity from each of the groups can be independently controlled.

Once the LED junctions have been mounted in place and the intermediate conductors connected, a phosphor is applied over the junctions at processing step109of stage101. The phosphor is preferably applied to at least two adjacent LED junctions.

The lead frame110is then transferred to a final stage102of processing to form the lamp140shown inFIG. 24. Stage102includes separating the sections112, removing excess lead frame material and either compression moulding, at step135or epoxy moulding, at step136, a globe portion137(seeFIG. 24) about the conductors112,114,115. Free ends of the conductors may then be bent into terminals or pins138, to be inserted in an associated through hole of a typical printed circuit board (PCB) or the like. The resultant lamp140may then be tested at step139and packaged, if required.

Another finished lamp150is shown inFIG. 25, with an additional moulded body151formed beneath the globe portion137. In this instance, the conductors within the globe portion have not been shown for simplicity, however, the conductors may have a configuration similar to that shown inFIG. 22, albeit that more junctions and associated recesses and conductors are provided. Specifically, 18 separately wired junctions are provided, with 18 associated pins138and a further pin152, for providing electric current to a common conductor within the globe portion137. As such, 18 different circuits are formed within the lamp150and these can be individually addressed and controlled via the pins138, which are again adapted to fit into PCB, or the like.

As may be appreciated then, the invention provides a method for producing an LED lamp which optimises output of the LED junctions by positioning the junctions in a three-dimensional array and utilising recesses for optical guides. Further, the construction allows different output of individual junctions or groups of junctions to be independently controlled to vary the intensity of emitted light. Lastly, it is again mentioned that the three-dimensional array of the junctions and the configuration of the curved conductors themselves allow for the light from the lamp to have more of an appearance of emanating from a single point or small spherical source, which may be considered an advantage over conventional discrete junction light emitting junction devices.

The above method and LED lamps have been described by way of non-limiting example only, and many modifications and variations may be made thereto without departing from the spirit and scope of the invention as hereinbefore described.