A HEAT SINK FIELD OF INVENTION

The present invention relates to lighting system, more particularly, to a series of light emitting diodes (LEDs) arranged in a linear pattern to form an LED assembly, wherein a metal plate acts as the connector between the LEDs and also functions as a heat sink, thereby eliminating the soldering process. Specifically, the present invention provides an LED assembly where the heat sink has been incorporated as a part of the series connector. This can help to eliminate the heat sink on the final light module thereby overcoming the problem of heat dissipation and thermal management efficiently. Thus, the present invention provides a simple, economical and more environmentally friendly LED assembly.

BACKGROUND OF INVENTION

The life of an LED depends on the operating temperature of the LED junction. Therefore, the thermal resistance between the junctions to the ambient is the key in determining the operating life and efficacy of the light module. One of the important factors is the heat generated during connecting the LEDs by soldering.

Early LEDs produced around 20 lumens of light per watt. Currently, commercial models with 120 lumens per watt are available. This represents about 20% of power converted to light. The unused energy is converted into heat, which must be removed, as otherwise the LED junction temperature starts increasing. A large majority of literature searches have yielded that the useful life of LEDs bears a direct correlation to the junction temperatures, i.e., the higher the junction temperature, the faster the LED failure. Subsequently several schemes for heat removal has been proposed with extreme solutions such as heat pumps built into LED modules. All these solutions involve complicated engineering and are expensive. The most elegant solutions are those where passive devices are employed to remove the heat away from the junction.

A typical single piece of white LED consumes only 50mW of power, which produces a small quantity of heat (~ 40mW) and thus does not require heat sink or specialized heat removal methods. However, the light output per LED is low and this requires more LEDs to be used to achieve a certain level of illumination. This is addresses by the multi chip LEDs where several chips are packaged in a single housing. This produces light of sufficient intensity but also causes the temperature to increase, as the heat generated by the larger number of LEDs has to be rejected over a small area. Moreover, when these LEDs are placed next to each other and arranged in a series or parallel form, the assembly starts to produce heat due to the combined power output. This heat needs to be removed quickly so as to reduce the junction temperatures of the individual LEDs.

The characteristics of any LED, causes large increase in current (and therefore temperature), for a small increase in the voltage, after a certain threshold voltage is reached. However, one cannot operate the LEDs at lower and safer voltage, as the light output is proportional to the current. LEDs that are manufactured to emit light in the visible spectrum generate a significant amount of heat, e.g., approximately 80% of the input energy received by the LED is converted to heat, with the remainder converted to light. Accordingly, the heat that is generated by the LED must be dissipated. The thermal management problem on High Brightness Light Emitting Diode (HB LED) is therefore always posing a great problem in LED technology. This is addressed by having large heat sinks typically made of die cast aluminium on the LED light housing.

Typically LEDs are connected to each other by soldering and care has to be taken to ensure that the thermal budget on the LED is not exceeded. Any excess thermal load on the LED device will lead to permanent damage of the LED.

Some attempts have been made in the past to deal with overcoming the limitations of prior arts such as those disclosed in the following:

US6501103 deals with a light emitting diode assembly with low thermal resistance. The assembly comprises an LED, a circuit board and a heat-dissipating substrate.

US7796030 relates to a high power LED housing consisting of one or more LED to form a LED assembly fitted into a metal body having an upper portion with a gripping means and a lower portion with a fitting means and a base.

US7121680 discloses a lighting head assembly that incorporates a high intensity LED package into an integral assembly including a heat sink and circuit board for further incorporation into other useful lighting devices.

US7652303 discloses a LED lighting assembly that incorporates a high intensity LED package into an integral assembly including a heat sink and circuit board for further incorporation into other useful lighting devices.

US7845828 deals with a LED assembly which includes a substrate and a plurality of LEDs mounted on the substrate. Each LED includes a base and a first and a second electrode leads inserted in the base.

US 2008122375 disclose a light emitting diode (LED) lamp assembly comprising of an LED string and a plug. The LED string comprises multiple LEDs connected together in series.

US20060202210 relates to a system and method for increasing heat dissipation of LED displays by using the current PCB packaging mounted to a LCD panel support structure thereby eliminating the need for a metal core PCB.

US20100207150 discloses a system and method for LED light engines that includes an LED package with electrical leads, each lead forming a compliant portion for making electrical and mechanical connection upon insertion into a receptacle of a circuit substrate. The invention uses a separate heat sink aperture and a printed circuit board.

642/DEL/2008 deals with a LED lighting assembly including a plurality of individual LEDs mounted on a common, bendable heat sinking member designed to remove heat from the LEDs during operation and also to be formed (bent) to provide the desired light direction and intensity.

4082/CHENP/2007 discloses a LED light module assembly for use with high power, high light output LEDs includes a thin flexible circuit board with surface mounted LEDs and other electronic components which is attached to a metal heat sink.

1949/CHE/2009 relates to plurality of LEDs arranged serially to form a LED assembly where conventional heat sink and printed circuit board can be eliminated. The lead electrodes of the LEDs are soldered with the lead electrode of the other LED and the additional length of the leads is taken as the heat transfer element.

1950/CHE/2009 deals with plurality of LEDs arranged in a linear pattern to form a LED assembly with integrated heat sink. The LEDs are arranged in series with integral serial/ parallel connection and bonding the LED chip onto a metal base. This metal base is in turn is fixed with conducting adhesive to the integral heat sink to remove the heat, while being electrically isolated.

Whereby it is desirable to provide an LED assembly, which overcome the shortcomings of prior art. The present invention substantially departs from the conventional concepts and designs of the prior art and in so doing it overcome other problems encountered in conventional products and services.

OBJECTS OF INVENTION

One or more of the problems of the conventional prior art may be overcome by various embodiments of the present invention.

It is thus the primary object of the present invention to provide a series of light emitting diodes (LEDs) arranged in a linear pattern to form an LED assembly.

It is another object of the present invention to provide an LED lighting system, wherein the LEDs are placed in an array and connected using metal plate clips, eliminating the need for a printed circuit board and for soldering the LEDs on to the printed circuit board.

It is yet another object of the present invention to provide a method of manufacturing LED lighting system by using metal plate clips to connect the LEDs without using soldering, thereby eliminating the need for a printed circuit board.

It is another object of the present invention to provide an LED lighting system, wherein the metal plate clip acts as a connector between the LEDs and also functions as a heat sink.

It is another object of the present invention, wherein the lead electrodes are connected in series with the metal clip by a mechanical crimping process, thereby eliminating possible damage due to overheating during the soldering process.

It is another object of the present invention, wherein the said lead electrode is pinched with the metal clip using a roller process, which provides good ohmic contact.

It is another object of the present invention, wherein the said module is then brushed with resins.

It is another object of the present invention, wherein the resin used for brushing is selected from commonly available epoxy resin suitable for encapsulation, which provides for good electrical isolation.

It is another object of the present invention, wherein the terminals of the said lead electrodes are connected to current limiting circuit for controlling the power supply and connected to AC or DC.

It is another object of the present invention to provide a series of LEDs arranged in a linear pattern to form an LED module, wherein the heat sink has been incorporated as a part of the series connector so that the heat sink on the light module can be eliminated.

It is another object of the present invention, wherein the metal clip is made of metal selected from the group consisting of a thin sheet of aluminium, copper, iron, tin or any metallic conductor or an alloy of such metals.

It is another object of the present invention, wherein the thickness of the metal sheet may be between 50 and 300 um.

It is another object of the present invention to provide a series of LEDs arranged in a linear pattern to form an LED module, wherein the metal clips can be fabricated in any shape as deemed necessary for the LED module design.

It is another object of the present invention to provide a series of LEDs arranged in a linear pattern to form an LED module, wherein the shape of the array of the LEDs can be of any shape to provide illumination as required.

It is another object of the present invention, wherein the LED module is powered by any suitable driver circuit depending on the number of LEDs in series or series parallel combination.

It is another object of the present invention to provide a series of LEDs arranged in a linear pattern to form an LED module, wherein the distance between the LEDs is generally but not limited to between 3 and 15 mm.

It is another object of the present invention is to provide a series of LEDs arranged in a linear pattern to form an LED module which has a lifetime several thousand hours longer than traditional lighting source.

It is another object of the present invention, wherein the elimination of PCB helps in reducing the cost of the overall assembly thereby making the product more eco friendly.

It is another object of the present invention to provide a series of LEDs arranged in a linear pattern to form an LED module, wherein the LED are left uncut whereby increasing the surface area for heat transfer.

A still further object of the present invention is to provide a series of LEDs arranged in a linear pattern to form an LED module, wherein the leads of the LEDs which are directly bonded to the metal clip connector enhances the heat removal process.

It is another object of the present invention to provide an LED lighting system, wherein a metal base is used for better heat dissipation which can achieve a heat transfer area exceeding 20cm2/Watt.

SUMMARY OF INVENTION

Thus according to the basic aspect of the present invention there is provided a light emitting diode (LED) lighting system comprising:
One or more LEDs arranged in a linear pattern in one or more metal sheets to form one or more arrays; and
one or more metal plate clips,
wherein the metal sheet is provided with one or more openings to accommodate the LEDs,
wherein the LEDs in the array are connected using the metal plate clips,
wherein each array is encapsulated with resins, and
wherein the positive lead of one LED and the negative lead of the next LED are part of the same metal plate clip.

In accordance with another aspect of the present invention there is provided an LED lighting system, wherein the metal plate clip acts as a heat sink.

In accordance with yet another aspect of the present invention there is provided an LED lighting system, wherein the lead electrodes of the LEDs are connected with the metal plate clip by a crimping process.

In accordance with another aspect of the present invention there is provided an LED lighting system, wherein the lead electrodes are pinched with the metal plate clip by a roller process.

It is another aspect of the present invention, wherein the metal plate clip is made of metal selected from the group consisting of a thin sheet of aluminium, copper, iron, tin or any metallic conductor or an alloy of such metals.

It is yet another aspect of the present invention, wherein the thickness of the metal sheet is in the range between 50 and 300 um.

It is further aspect of the present invention, wherein the distance between the LEDs in the array is between 3 mm and 15 mm.

It is another aspect of the present invention, wherein the metal plate clips can be of any geometrical shape.

It is another aspect of the present invention, wherein the array can be of any geometrical shape.

It is another aspect of the present invention, wherein the lighting system is powered by a driver circuit which is selected based on the number of LEDs in series or series parallel combination.

It is another aspect of the present invention, wherein the LEDs are left uncut to increase the surface area for heat transfer.

It is another aspect of the present invention, wherein the terminals of the lead electrodes are connected to current limiting circuit for controlling the power supply.

It is another aspect of the present invention, wherein the lighting system has heat transfer area greater than 20 cm2/Watt.

In accordance with another aspect of the present invention there is provided a method of manufacturing LED lighting system, comprising:
inserting the LEDs in series into the metal sheet;
inserting the metal plate clips into the adjacent lead electrodes of the LEDs by a crimping
process;
pinching the lead electrodes with the metal clip by a rolling process; and
encapsulating the array with resin,
wherein the positive lead of one LED and the negative lead of the next LED are part of the same metal clip, and
wherein the connection between the anode and the cathode of the LED act as the heat sink.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1: illustrates the arrangement of the LEDs in the jig according to the present invention.

Figure 2: illustrates the positioning of the metal connector clips according to the present
invention.

Figure 3: illustrates the LED arrangement after crimping process according to the present
invention.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS

Thus, an LED lighting system according to the present invention is made without any soldering process thus eliminating the need for a printed circuit board and which does not need an external heat sink. The invention provides a manufacturing method of connecting the LEDs without a thermal process such as soldering, but is connected by a mechanical crimping process. The present arrangement will eliminate possible damage due to overheating during the soldering process which can also overcome the problem of heat dissipation and thermal management in a much better manner.

Reference is now invited to accompanying Figure 1, which illustrates the arrangement of the LEDs in the jig. According to Figure 1, a metal sheet is provided with an opening to accommodate the LEDs. The LEDs are connected in series in a linear pattern in the metal sheet with the leads pointing upwards to form one or more arrays. This insertion can be done manually or with suitable automated equipments. The metal sheet/base is used for better heat dissipation to achieve a heat transfer area exceeding 20 cm /Watt.

Reference is then invited to Figure 2, according to which the metal clips are inserted into adjacent leads of the LEDs where the positive lead of one LED and the negative lead of the next LED are part of the same clip. The connection between the anode and the cathode of the LED is the heat sink. After this process the linear arrangement of the LEDs are fed through a roller assembly to crimp the metal plate with the LED leads as shown in Figure 3. The roller assembly is arranged so as to have a minimum gap between the rollers. The force applied by the roller assembly is also important and is adjusted to provide optimum force to attach the leads to the metal plate without any damage to the leads. This ensures that the LEDs are interconnected without any additional contact resistance than the soldering process. The leads of the LEDs should be left long so as to accommodate the clip. In addition, the length of the clip is directly proportional to the area of the clip which increases the heat transfer area.

Conventionally, the LED leads are normally inserted into printed circuit board (PCB) and are soldered in position. The excess length of the leads are then cut and removed. The soldering point is very close to the LEDs, with just the thickness of the PCB, and the hole in the PCB is designed to allow the solder to flow upto the LED. Thus, the probability of the heat being conducted from the soldering point to the LED becomes high. If the soldering time is larger than what is permissible, the life of the LED would be appreciably reduced due to thermal damage of the semiconductor.

Although particular components and materials are specifically identified herein, one skilled in the art may readily substitute the components and/or materials of similar function without departing from the invention as defined in the appended objects.

The following are some of the advantages of the present invention:

1. Eliminate the need of a printed circuit board
2. Eliminate the need of conventional heat sink
3. Eliminate soldering of LEDs
4. Eliminate damage due to overheating
5. The metal plate acts both as connector between LEDs and heat sink
6. LEDs are connected by mechanical crimping process
7. LEDs are left uncut
8. Provide good ohmic contact
9. Provides good electrical isolation
10. Different shapes of LED arrays are possible
11. Longer lifetime
12. Less cost LED array
13. Eco friendly
14. Enhanced heat dissipation capacity
15. Enhanced heat removing facility

Although the above provides a full and complete disclosure of the preferred embodiments of the invention, various modifications, alternate constructions and equivalents will occur to those skilled in the art. For example, other geometrical configurations other than described above may be employed, as desired. Further, many symbols and legends may be implemented by installing an opaque mask with appropriate translucent areas in front of a module. In addition, modules may be fabricated using integrated circuit processing technology to provide a series of individual light sources distributed throughout the viewable area of the module, with each light source having the two-color or three-color light elements with cathodes coupled in common and individually connectible anodes. In such an embodiment, the individual encapsulation packages can be replaced with a single transparent or translucent cover having lens regions located over the individual light sources. Therefore, the above should not be construed as limiting the invention, which is defined by the appended objects.

WE CLAIM:

1. A light emitting diode (LED) lighting system comprising:
One or more LEDs arranged in a linear pattern in one or more metal sheets to form one or more arrays; and
one or more metal plate clips,
wherein the metal sheet is provided with one or more openings to accommodate the LEDs,
wherein the LEDs in the array are connected using the metal plate clips,
wherein each array is encapsulated with resins, and
wherein the positive lead of one LED and the negative lead of the next LED are part of the same metal plate clip.

2. The LED lighting system as claimed in claim 1, wherein the metal plate clip acts as a heat sink.

3. The LED lighting system as claimed in claim 1, wherein the lead electrodes of the LEDs are connected with the metal plate clip by a crimping process.

4. The LED lighting system as claimed in claim 3, wherein the lead electrodes are pinched with the metal plate clip by a roller process.

5. The LED lighting system as claimed in anyone of claims 1 to 4, wherein the metal plate clip is made of metal selected from the group consisting of a thin sheet of aluminium, copper, iron, tin or any metallic conductor or an alloy of such metals.

6. The LED lighting system as claimed in claim 1, wherein the thickness of the metal sheet is in the range between 50 and 300 urn.

7. The LED lighting system as claimed in claim 1, wherein the distance between the LEDs in the array is between 3mm and 15 mm.

8. The LED lighting system as claimed in anyone of claims 1 to 7, wherein the metal plate clips can be of any geometrical shape.

9. The LED lighting system as claimed in claim 1, wherein the array can be of any geometrical shape.

10. The LED lighting system as claimed in anyone of claims 1 to 9, wherein the lighting system is powered by a driver circuit, which is selected based on the number of LEDs in series or series parallel combination.

11. The LED lighting system as claimed in anyone of claims 1 to 10, wherein the LEDs are left uncut to increase the surface area for heat transfer.

12. The LED lighting system as claimed in anyone of claims 1 to 11, wherein the terminals of the lead electrodes are connected to current limiting circuit for controlling the power supply.

13. The LED lighting system as claimed in anyone of claims 1 to 12, wherein the lighting system has heat transfer area greater than 20 cm2/Watt.

14. A method of manufacturing LED lighting system as claimed in anyone of claims 1 to 13, comprising:

inserting the LEDs in series into the metal sheet;

inserting the metal plate clips into the adjacent lead electrodes of the LEDs by a crimping process;

pinching the lead electrodes with the metal clip by a rolling process; and

encapsulating the array with resin,
wherein the positive lead of one LED and the negative lead of the next LED are part of the same metal plate clip, and

wherein the connection between the anode and the cathode of the LED act as the heat sink.