VWGoA - Ex. 1015
`Volkswagen Group of America, Inc., Petitioner
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`Apr. 4, 1995
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`Sheet 1 of 5
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`5,404,282
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` U.S.Patent
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`U.S. Patent
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`Apr. 4, 1995
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`Sheet 2 of 5
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`5,404,282
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`U.S. Patent
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`Apr. 4, 1995
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`Sheet 3 of 5
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`5,404,282
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`52¢;
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`272a
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`Apr. 4, 1995
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`Sheet 4 of 5
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`5,404,282
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` U.S.Patent
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`U.S. Patent
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`Apr. 4, 1995
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`Sheet 5 of 5
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`5,404,282
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`5,404,282
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`MULTIPLE LIGHT EMITTING DIODE MODULE
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`CROSS REFERENCE TO RELATED
`APPLICATIONS
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`This is a continuation of application Ser. No.
`08/123,134, filed on Sep. 17, 1993, now abandoned.
`FIELD OF THE INVENTION
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`This invention relates to a device comprising a multi- 1
`plicity of light emitting diodes for providing a source of
`illumination such as for the exterior portion of an auto-
`mobile.
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`BACKGROUND
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`Light emitting diodes (LEDs) are a type of semicon-
`ductor device that emit 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 20
`than standard bulb or filament type lamps, making their
`use particularly desirable in applications where a pre-
`mium is placed on space, such as cameras, watches,
`computers, computer printers and numerous other com-
`pact devices. Additionally, the LED is energy efficient 25
`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 with battery powered portable devices.
`Generally speaking, although 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 illumina-
`tion as a light assembly illuminated by standard bulb 35
`type lamps. However, the combination of LED lamps
`typically occupy less space and require less energy to
`operate than that of the standard bulb type lamps they
`replace. The space saving and energy efficient features
`of the LED make it a popular choice with designers and 40
`manufacturers 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
`automobile industry as a source of illumination, replac- 45
`ing standard bulb type lamps, for exterior lights, such as
`parking lights, brake lights and the like. It is highly
`desirable that the light source used in the automobile be
`energy efficient. The LED is a popular choice in such
`an application because its use permits the replacement 50
`of standard bulb type lamps that require a larger space
`and consume a greater amount of energy to operate.
`The space savings that results from replacing standard
`bulb type lamps with the LED in such an application
`may be better put to use in the form of added passenger 55
`or storage capacity. Size savings can translate into
`weight savings as well, a.n important factor in fuel econ-
`omy.
`The standard bulb type lamps are known to have a
`high rate of failure when used in an automotive applica- 60
`tion. The high failure rate is attributable to the filament
`breaking due to sudden shocks or bumps experienced
`under normal driving conditions. Unlike standard bulb
`type lamps, LED lamps are immune to such failures due
`to their inherent construction. The light emitted by an 65
`LED is caused by the generation of photons from mate-
`rials within the LED and is not the product of an elec-
`trical current passing through an illuminating filament.
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`Since the LED does not rely on the fragile filament
`scheme used in bulb type lamps it is better suited for use
`as a reliable automobile lighting source.
`Additionally, standard bulb type lamps are known to
`generate a large amount of heat during their operation.
`The heat generated by standard 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 and the like.
`Accordingly, the choice of using LED lamps to re-
`place standard bulb type lamps as the lighting source for
`the automobile is desirable because their use provides a
`more efficient use of space, is energy efficient, elimi-
`nates a common cause of light source failure, and elimi-
`nates lens deformation associated with a high heat gen-
`erating bulb type light source.
`A single LED typically produces less illumination
`than that of a standard bulb type light. Therefore, a
`plurality of LED lamps are combined in order to pro-
`vide the same degree of illumination provided by one or
`more standard bulb lamps. The LED lamps are com-
`bined to form a LED module that comprises a plurality
`of‘LED lamps and means for mechanically and electri-
`cally connecting the LED lamps to a light assembly.
`The LED module may be configured so that it contains
`the required number of LED lamps arranged in a circuit
`to provide the desired degree of illumination. Addition-
`ally, the LED module should be configured to accom-
`modate the particular shape or size of the light assem-
`bly, which may be defined by the shape or contour of
`the automobile body design.
`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 con-
`ductive 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 as-
`sembly. The LED module is mechanically attached to
`the light assembly and the printed circuit board is elec-
`trically connected to an anode or cathode electrical
`source within the light assembly.
`Such LED modules typically use a solder connection
`to connect the anode and cathode lead of each LED to
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`the respective conductive paths in order to ensure a
`good electrical and mechanical connection. However,
`solder connecting each LED is a known cause of LED
`failure. During the soldering operation heat is trans-
`ferred from the soldering site, through the lead of each
`LED and to the LED chip resulting in thermal damage.
`This potential for thermal damage during the manufac-
`ture of the LED module may reduce the reliability of
`the LED and limits its viability as a desirable lighting
`source.
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`LED modules known in the art have attempted to
`minimize the potential for thermal damage to the LED
`la.inps 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 corre-
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`spondingly 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 conduc-
`tivity 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 connect-
`ing LED lamps is desirable for both reducing the cost of
`an LED module and increasing the electrical efficiency
`of an LED module.
`It is, therefore, 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 is
`desirable that mounting of LED lamps in the LED
`module promotes optimal electrical and thermal effi-
`ciency. It is desirable that the LED module permits
`arbitrary spacing of each LED in order to correspond
`to predetermined shapes or illumination requirements.
`It is also desirable that the LED module be practical to
`produce from both an economic and manufacturing
`standpoint.
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`BRIEF SUMMARY OF THE INVENTION
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`There is, therefore, provided in practice of this inven-
`tion an LED module used as a source of illumination.
`The LED module comprises a plurality of LED lamps
`each having an anode lead and a cathode lead. The
`anode lead of each LED is connected to an anode bus
`bar and the cathode lead of each LED is connected to
`a cathode bus bar. The anode and cathode bus bars may
`be arranged in parallel relation to each other, and sepa-
`rated by the plurality of LED lamps. The anode and
`cathode bus bars are constructed from an electrically
`and thermally conductive material compatible with the
`anode lead and cathode lead of each LED. The LED
`module may be configured having LED la.mps arranged
`in a serial configuration or a combination serial/parallel
`configuration depending on the predetermined lighting
`requirement and/or the design of the accommodating
`light assembly.
`The anode lead and cathode lead of each LED may
`be connected to the respective anode and cathode bus
`bars by any of several techniques. The bus bars and
`leads of each LED lamp may be integral with each
`other. Alternatively, the bus bars and leads of each
`LED lamp may be independent members that are con-
`nected by an interference fit formed between approxi-
`mately complementary portions of each lead and bus
`bar. For example, each lead and bus bar may be at-
`tached by an interlocking fit formed between a recessed
`portion of the lead and an approximately complemen-
`tary recessed portion of the bus bar. Each lead and bus
`bar may also be attached by an interference fit formed
`between the lead and an accommodating tab integral
`with the bus bar. Alternatively, each LED lead and bus
`. bar may be attached by using a low-heat technique such
`as spot welding or the like.
`The LED module is configured to accommodate
`series and parallel electrical and mechanical intercon-
`nection with other LED modules to form a LED assem-
`bly having a predetermined length and comprising a
`desired number of LED lamps.
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`The LED module according to the present invention
`permits a designer to vary the placement of each LED
`in the module depending on the desired lighting require-
`ment for a particular application. The LED module
`may also be configured to fit within a particularly
`shaped light assembly. The integral, interlocking, inter-
`ference, or low-heat connection of each LED within
`the LED module avoids the need to solder connect
`each LED, eliminating potential thermal damage to
`each LED, and thus increasing the reliability of the
`LED module. Additionally, such a connection scheme
`avoids the costs associated with having to mount the
`LED lamps on a printed circuit board.
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`BRIEF DESCRIPTION OF THE DRAWINGS
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`These and other features and advantages of the pres-
`ent invention will become appreciated as the same be-
`comes better understood with reference to the specifica-
`tion, claims, and drawings wherein:
`FIG. 1 is a semi-schematic exploded side view of an
`automobile light assembly comprising the LED module
`of the present invention;
`FIG. 2 is a perspective view of a first embodiment of
`the LED module according to the present invention;
`FIG. 3 is a cross sectional view of a LED taken at
`3—3 in FIG. 2;
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`FIG. 4 is an electrical diagram of a LED assembly
`comprising three LED modules in series electrical con-
`nection;
`FIG. 5 is a perspective view of a second embodiment
`of the LED module;
`FIG. 6 is a fragmentary cross sectional view of a lead
`connection known as a button lock taken at 6—6 in
`FIG. 5;
`FIG. 7 is a perspective view of a third embodiment of
`the LED module;
`FIG. 8 is a plan view of an anode bus bar after a tab
`slot is formed;
`FIG. 9 is a side view of the anode bus bar after an
`integral tab has been bent away from the surface of the
`anode bus bar;
`FIG. 10 is a side view of the anode bus bar after the
`integral tab has been bent about the anode lead;
`FIG. 11 is a side view of an anode bus bar comprising
`two integral tabs;
`FIG. 12 is a plan view of an alternative embodiment
`of interconnected LED modules comprising a matrix of
`LED lamps; and
`FIG. 13 is an electrical diagram of a alternative em-
`bodiment of the LED module comprising LED lamps
`arranged in series/parallel electrical connection.
`DETAILED DESCRIPTION
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`FIG. 1 shows a light emitting diode (LED) module
`10 according to the present invention as it may be used
`to provide exterior lighting in an automobile light as-
`sembly 12 such as a brake light. The automobile light
`assembly comprises a housing 14, one or more LED
`modules 10, and a backplate 16. The LED module com-
`prises a plurality of LED lamps 18 that are electrically
`and mechanically connected in a manner forming a strip
`of LED lamps. The LED module is sized and config-
`ured to accommodate mechanical and electrical con-
`nection with the back plate 16 that may be shaped ac-
`cording to the contour or design of the automobile
`body. The LED module is made up of the desired num-
`ber of LED lamps to accommodate the light housing 14
`and provide the desired amount of illumination. The
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`cathode bus bar which are each approximately five
`millimeters high, approximately 0.4 millimeters thick,
`and are spaced apart from each other a distance of ap-
`proximately five millimeters. The LED lamps are ar-
`ranged on the module at spacings of about ten millime-
`ters.
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`In FIGS. 2, 5, and 7 the LED module is illustrated
`having an anode bus bar 28 connected to the anode lead
`24 of each LED lamp, and similarly a cathode bus bar
`30 is connected to the cathode lead 26 of each LED
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`lamp. The manner in which the LED lamp leads are
`configured is not intended be representative of a partic-
`ular LED lamp. For example, each LED lamp in FIG.
`. 5 is shown with two cathode leads and only one anode
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`lead. The differences between the two leads are not
`meant to be representative of a particular type of LED
`lamp, but rather, are used for purposes of clarity to
`distinguish the two leads. It is to be understood that
`there is no conventional anode or cathode lead configu-
`ration. Accordingly, any type of LED lamp may be
`used to construct an LED module according to practice
`of this invention.
`In the first embodiment, the anode bus bar and cath-
`ode bus bar and the respective anode lead and cathode
`lead of each LED lamp are integral with each other.
`The integral lead-bus bar arrangement may be accom-
`plished during the manufacturing process of the LED
`lamps. The LED lamp is constructed in such a manner
`that the anode bus bar and cathode bus bar are incorpo-
`rated as the anode and cathode portion of each LED
`lamp. This type of bus bar may be referred to as a “free”
`or “low cost” bus bar because it is the product of the
`method used to manufacture the LED lamps and is not
`manufactured as an individual component. Accord-
`ingly, the LED module comprising such an integral
`lead-bus bar connection arrangement should be more
`cost efficient to produce than LED modules comprising
`bus bars that are non-integral members of each LED
`lamp.
`The integral lead-bus bar connection of the first em-
`bodiment avoids the need to use a solder connection to
`connect each LED lamp to the bus bars. Avoiding the
`need to solder connect each lead to its respective bus
`bar eliminates potential thermal damage that may occur
`to each LED lamp, and thus increases the reliability of
`each LED lamp and the LED module. Additionally,
`eliminating the need to solder connect each LED lamp
`also permits the use of bus bars made from materials
`having a high electrical and thermal conductivity, opti-
`mizing the electrical and thermal efficiency of the LED
`module. A preferred bus bar material may comprise
`copper and the like.
`Since the bus bars of the LED module in this first
`embodiment are integral members of each LED lamp,
`the danger of thermal stresses developing between two
`materials having different thermal expansion coeffici-
`ents is eliminated. Eliminating the potential for thermal
`stress to develop between each LED lamp and the bus
`bars increases the reliability of their mechanical and
`electrical connection, and thus optimizes the reliability
`of the LED module.
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`LED module is incorporated between the back housing
`and the light housing to form the automobile light as-
`sembly. The LED module may be electrically con-
`nected at each end to an electrical connector 19 extend-
`ing from the backplate.
`Although the LED module of the present invention is
`described in the context of providing illumination for
`the exterior portion of automobiles, the LED module of
`the present invention may also be used as a light source
`for illuminating the interior portion of an automobile or 10
`as a light source in applications other than automobiles.
`FIG. 2 shows a first embodiment of the LED module
`10 according to the present invention. The LED mod-
`ule comprises a plurality of LED lamps 18 (although
`the LED module may comprise any number of LED
`lamps, for purposes of clarity a LED module compris-
`ing only five LED lamps is shown). Each LED lamp
`has a front face 20 and a back face positioned opposite
`the front face. The front face of the LED lamp is the
`face from which the LED in the lamp emits light. Each
`LED lamp has an anode lead 24 and a cathode lead 26
`that each extend downward and away from opposite
`ends of the back face and provide electrical connection
`to the LED in the lamp.
`Each LED lamp is conventional. It comprises an
`anode lead 24 and a cathode lead(s) 26 for making elec-
`trical connection to a light emitting diode 25 as shown
`in FIG. 3. Generally, the LED is secured in a reflective
`cavity in, for example, the cathode lead by an electri-
`cally conductive adhesive. A fine wire 27 is wire
`bonded to the front face of the LED and to the adjacent
`anode lead. The ends of the leads and the LED are
`embedded or “potted” in a transparent plastic such as an
`epoxy resin. Since the leads are secured in the plastic,
`they also serve as mechanical support for the LED
`lamp. Quite often the front face 20 of the LED lamp is
`molded with a convex lens 29 for concentrating the
`emitted light. In this description, the terms LED and
`LED lamp may be used interchangeably.
`The specific construction of the LED and LED 40
`lamp, the arrangement of leads in the lamp, etc., are not
`significant for practice of this invention. This can be
`recognized, for example, by noting that the leads in the
`embodiment of FIG. 2 exit the plastic through the back
`face, whereas the leads in the embodiment of FIG. 5 exit 45
`through side faces of the plastic. It will also be,recog-
`nized that some LED lamps are round domes instead of
`rectangular bodies with a domed lens on a flat face.
`Each LED lamp is connected to an anode bus bar 28
`and a cathode bus bar 30. In the first embodiment, the 50
`anode lead of each LED lamp is integral with the anode
`bus bar. Similarly, the cathode lead of each LED lamp
`is integral with the cathode bus bar.
`The position of each bus bar relative to each LED
`lamp may be dependent on the particular mechanical 55
`and/or electrical connection requirement of an accom-
`' modating light assembly. In the first embodiment, the
`anode bus bar is positioned adjacent to the back face of
`each LED lamp near the anode lead 24. In similar fash-
`ion, the cathode bus bar is positioned adjacent to the
`back face of each LED lamp near the cathode lead 26.
`The anode bus bar and cathode bus bar each comprise a
`. strip of electrically conductive material. The configura-
`tion and thickness of each bus bar may be dependent on
`the number of LED lamps desired for a particular appli- 65
`cation as well as the particular electrical or mechanical
`connection requirements of a particular light assembly.
`A typical LED module may comprise an anode and
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`The LED module according to present invention
`may be configured to accommodate a plurality of LED
`lamps used for providing exterior automobile illumina-
`tion, such as parking lights, tail lights, brake lights and
`the like. The LED module may be configured as a strip
`of desired length comprising a predetermined number
`of sequentially arranged LED lamps. Each bus bar may
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`contain holes 32 or the like as shown in FIG. 2 to facili-
`tate its connection with an electrical connector within a
`light assembly. The holes may also be used to facilitate
`the series interconnection of two or more adjacent
`LED modules as shown by electrical diagram in FIG. 4
`using one of the mechanical connection schemes ac-
`cording to principles of this invention.
`It may be desirable to connect LED modules in an
`electrical series as illustrated in FIG. 4 to obtain a de-
`sired voltage-current relationship for a group of lamps.
`For example, in an automotive application the voltage
`available is over 12 volts, whereas the typical voltage
`drop across an LED is less than about 2 volts. By using
`groups of lamps in parallel and connecting the groups in
`series, the desired voltage drop is obtained for a light
`source with many LED lamps. The number of lamps in
`a parallel module and the number of such modules con-
`nected in series depends on several factors including the
`area illuminated, the voltage and current available, the
`reliability of manufacturing the modules, and the num-
`ber of lamps readily made per module in the specific
`manufacturing equipment available, for example. For
`purposes of clarity and illustration, the LED modules
`may be arranged in an electrical seriesby electrically
`connecting the cathode bus bar of each LED module to
`an anode bus bar of an adjacent LED module.
`The ability to interconnect LED modules in series is
`desirable because it may allow the designer to obtain a
`desired degree of illumination without being limited by
`the manufacturing process of the LED lamps. For ex-
`ample, LED lamps may be manufactured in relatively
`small groups of five or six due to the limitations of the
`manufacturing process itself. Accordingly, a first em-
`bodiment of the LED module comprising LED lamps
`manufactured by such a process may contain only four
`to six LED lamps. The designer can overcome the
`inherent limitations of such a LED lamp manufacturing
`process, and obtain the desired degree of illumination,
`by simply interconnecting in series the desired number
`of LED modules. Each LED module may be connected
`to an electrical source or with another LED module by
`techniques well known by those skilled in the art such
`as by a spot weld, rivet, interference fit and the like.
`A shortcoming of the integral lead-bus bar embodi-
`ment is a lack of electrical and mechanical flexibility.
`Different applications of LED lamps call for different
`spacings between each LED lamp, voltage matching
`LED lamps, for example, or electrical connections dif-
`ferent from the parallel connections illustrated. The
`tooling for making an integral lead-bus bar embodiment
`is costly and unless a very large number of modules are
`to be built, the unit cost may be excessive. Thus, a dif-
`ferent technique is desirable for flexibility in the manu-
`facturing process to make LED modules with desired
`configurations.
`Generally speaking, a suitable different technique is
`to manufacture LED lamps on a bus bar as presently
`practiced, cut the individual LED lamps from the bus
`bar, and then reconnect the LED lamps to parallel
`bar-like strips with any desired spacing. Such modules
`can be made with a few or many LED lamps in parallel
`and may be interconnected in series and parallel ar-
`rangements to obtain desired electrical properties.
`Thus, FIG. 5 shows a second embodiment of the
`LED module 10 according to the present invention.
`Like the first embodiment,
`the second embodiment
`comprises a plurality of LED lamps 18 (although the
`LED module may comprise any number of LED lamps,
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`for purposes of clarity a LED module comprising only
`three LED lamps is shown). Each LED lamp has a
`front face 20 and a back face positioned opposite to the
`front face. Each LED lamp has an anode lead 24 and a
`cathode lead(s) 26 which each extend outwardly and
`away from the LED lamp from opposite sides and pro-
`vide electrical connection to the LED lamp. The anode
`lead of each LED lamp is connected to the anode bus
`bar 28 and the cathode lead of each LED lamp is con-
`nected to the cathode bus bar 30.
`The anode bus bar and cathode bus bar are positioned
`parallel to each other and are separated by the LED
`lamps. Each bus bar comprises a thin strip of electrically
`conductive material. The thickness and configuration of
`each bus bar may vary depending on the desired illumi-
`nation requirements or configuration of the accommo-
`dating light assembly. A preferred LED module may
`comprise an anode and cathode bus bar that are each
`approximately five millimeters wide and approximately
`0.4 millimeters thick.
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`The anode and cathode bus bar may be positioned
`with respect to the LED lamps differently than that
`illustrated in FIG. 5 depending on the particular config-
`uration or connection requirement of the light assem-
`bly. For example, the anode bus bar and cathode bus bar
`may be positioned with their faces perpendicular to the
`front face of the LED lamp as shown in FIG. 2. The
`leads for such a configuration may be bent inside or
`outside of the plastic potting material.
`Unlike the first embodiment, the anode bus bar and
`cathode bus bar of the second embodiment are non-inte-
`gral with the respective anode lead and cathode lead of
`each LED lamp. The anode lead of each LED lamp is
`connected to the anode bus bar to form an anode lead
`connection 34. Similarly, the cathode lead of each LED
`lamp is connected to the cathode bus bar to form a
`cathode lead connection 36. The leads of each LED
`lamp may be connected to the bus bars by using an
`interlocking connection whereby a portion of the lead
`of each LED lamp is placed in intimate interface with
`an approximately complementary portion of the respec-
`tive bus bar. The connection may be formed by using
`techniques well known to those skilled in the art for
`other purposes, such as by clinching and the like.
`In the second embodiment, the anode lead connection
`34 and cathode lead connection 36 each comprises a
`recessed portion of the lead placed in intimate interface
`with an approximately complementary portion of the
`respective bus bar as shown in FIG. 6. The lead connec-
`tion or button lock in the second embodiment can be
`formed by a well known commercial process such as
`one that uses a punch to place an indentation into both
`the lead and the respective bus bar after the lead had
`been aligned and placed into position against the surface
`of the bus bar. In such a technique, a punch deep draws
`a cup-shaped impression in both the lead and bus bar.
`When the closed end of the cup is pressed in the oppo-
`site direction, the walls of the cups “mushroom” or
`bulge outwardly a small amount for interlocking the
`inner cup into the outer cup. This forms both a secure
`mechanical interlock, but also a low resistance electrical
`connection. As illustrated, the inner cup is formed in a
`portion of the lead and the outer cup is formed in the
`bus bar. These could clearly be reversed if desired.
`Although the anode and cathode lead connections of
`the second embodiment are formed by interlocking
`recessed lead and bus bar portions, other mechanical
`interlocking connections defined as an interference fit,
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`interlocking fit or equivalent may be used within the
`scope of the present invention. For example, an inter-
`locking connection may be achieved by using a rivet
`and the like as the mushroomed member. Although the
`second embodiment of LED module shows a single 5
`interlocking connection at each lead, the lead may be
`joined to the respective bus bar by using one or more
`interlocking connections if such is desired.
`Unlike the first embodiment of the LED module,
`which comprises an anode and cathode bus bar that are 10
`integral members of each LED lamp, the second em-
`bodiment comprises an anode and cathode bus bar that
`are non-integral members of each LED lamp. The
`placement of each LED lamp along the anode and cath-
`ode bus bar, therefore, is not dependent on the manufac- 15
`turing process of each LED lamp. Rather, each LED
`lamp can be placed at arbitrary positions along the bus
`bars, permitting the designer to vary the pitch of the
`LED lamps depending on the particular lighting re-
`quirement or configuration of the accommodating light 20
`assembly.
`The anode and cathode lead connection in this sec-
`ond embodiment, like the first embodiment, avoids the
`need to solder connect each lead of the LED lamp to
`the respective bus bars. Avoiding the need to solder 25
`eliminates the possibility of causing thermal damage to
`the LED lamps, and thus increases the reliability of
`each LED lamp and the LED module. Additionally,
`avoiding a solder connection permits the use of bus bars
`constructed from a material having a high electrical 30
`conductivity, optimizing the electrical efficiency of
`each LED lamp and the LED module. Copper is a
`preferred bus bar material.
`To minimize the occurrence of thermal stress that
`may develop between two connected metals having 35
`different properties of thermal expansion, it is preferred
`that the bus bar material selected have an approximately
`equal or at least a similar coefficient of thermal expan-
`sion (CTE) as the CTE of the lead material of each
`LED lamp. Selecting a bus bar material having the same 40
`CTE as that of the LED lamp leads eliminates the possi-
`bility of a thermally related mechanical failure that may
`occur at the anode lead connection 34 and the cathode
`lead connection 36, and thus increases the reliability of
`the LED module. It is also desirable that the material 45
`selected for the bus bars be compatible with the material
`of the leads of the LED lamps to prevent the occur-
`rence of undesirable galvanic action, such as corrosion
`or the like, at the points of connection.
`FIG. 7 shows a third embodiment of the LED mod- 50
`ule 10 according to the present invention. The third
`embodiment is similar to the second embodiment in all
`
`respects except for the anode lead connection 34 and
`the cathode lead connection 36. Like the second em-
`bodiment, the anode bus bar and the cathode bus bar in 55
`the third embodiment are non-integral with the anode
`lead and cathode lead of each LED lamp. The leads of
`each LED lamp are mechanically and electrically con-
`nected to the bus bars by an interference fit formed
`between the leads and a tab 40 integral with the respec- 60
`tive bus bars.
`
`The lead connection is formed by first cutting at least
`one tab slot 38 into each bus bar to form a integral tab
`40 as shown in FIGS. 7 and 8. During the cutting step
`the integral tab of each bus bar is bent outward and 65
`away from a front face of each bus bar as shown in
`FIGS. 8 and 9. The tab is of sufficient size and length to
`accommodate its placement over the surface of the
`
`10
`complementary lead of each LED lamp. A connecting
`portion of the lead 24 of each LED lamp comprises a
`front face and a back face opposite to the front face. The
`back face of the connecting portion of each lead is
`placed into position against the front face of the respec-
`tive bus bar near the attached portion of the integral tab.
`The integral tab is bent inward towards the bus bar
`around and over the lead as shown in FIGS. 7 and 10.
`A force is applied to the tab to form an interference fit
`by an intimate interface between the front face of the
`bar and the back face of the lead and between the front
`face of the lead and the integral tab.
`Alternatively, the leads of each LED lamp may be
`connected to the respective bus bars by an interference
`fit comprising more than one integral tab 40. For exam-
`ple, a pair of integral tabs may be formed at each bus bar
`and bent around a lead to form an interference fit as
`shown in FIG. 11. Other connections such as the crimp
`connections used in solderless wire terminations and
`connectors could also be used, as well as interface
`“slots” common to insulation displacement connection
`schemes.
`Like the second embodiment of the LED module, the
`third embodiment permits the arbitrary placement of
`the LED lamps along the pair of bus bars, thereby al-
`lowing the designer to place the LED lamps according
`to the particular lighting requirem