WO2013027169A2

WO2013027169A2 - Light source using a bent pcb

Info

Publication number: WO2013027169A2
Application number: PCT/IB2012/054212
Authority: WO
Inventors: Udayan Kanade; Sanat Ganu
Original assignee: I2Ic Corporation
Priority date: 2011-08-19
Filing date: 2012-08-20
Publication date: 2013-02-28
Also published as: WO2013027169A3

Abstract

A single side emitting, multi-segment linear light source is disclosed. Each segment of the light source has an LED, a light guide with light extraction features, and a bent reflector sheet. All of this is mounted on a PCB that is bent in a plurality of places. The PCB provides mechanical support, electrical contacts and conducts heat generated by the LED away. Electrical connections are provided across the bend in the PCB using novel means.

Description

LIGHT SOURCE USING A BENT PCB

This application claims priority from provisional patent application 2349/MUM/2011 titled "Light Source Using a Bent PCB" filed in Mumbai, India on 19th August 2011.

Technical Field

This invention relates to light sources. This invention also relates to electronics manufacturing.

Background Art

Light sources are used for general purpose lighting and for special purposes such as display backlighting. Light sources may be made of point light sources, such as light emitting diodes (LEDs), which source light into a light guide. The light is emanated out of the light guide by light extraction means such as geometrical shapes, surface roughness or etching, or by light deflecting particles.

Summary

The above and other preferred features, including various details of implementation and combination of elements are more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular methods and systems described herein are shown by way of illustrations only and not as limitations. As will be understood by those skilled in the art, the principles and features described herein may be employed in various and numerous embodiments without departing from the scope of the invention.

Brief Description of Drawings

The accompanying drawings, which are included as part of the present specification, illustrate the presently preferred embodiment and together with the general description given above and the detailed description of the preferred embodiment given below serve to explain and teach the principles of the present invention.

Figure 1 shows a bent printed circuit board (PCB).

Figure 2 shows a PCB before it is bent.

Figure 3 shows a PCB before it is bent.

Figure 4 shows a PCB before it is bent.

Figure 5 shows a PCB before it is bent.

Figure 6 shows a bent PCB with mounted LEDs (light emitting diodes).

Figure 7 shows a bent PCB with mounted LEDs.

Figure 8 shows a PCB with mounted LEDs before it is bent.

Figure 9 shows a multi-segment linear light source with LEDs on a bent PCB, and linear light guides.

Figure 10 shows a metal sheet, or other bendable sheet.

Figure 11 shows one segment of a linear light source having a bent sheet and a linear light guide.

Figure 12 shows one segment of a linear light source with a bent sheet, a bent PCB, an LED (or a group of LEDs) and a linear light guide.

Figure 13 shows a single side emitting multi-segment linear light source with a bent sheet, a bent PCB, LEDs and linear light guides.

Detailed Description

Figure 1 shows a bent printed circuit board (PCB) 199. The bent PCB 199 might be a metal-clad PCB (MCPCB). There is a flexible PCB 101 or a flexible connector 101 at the bend 102 of the bent PCB 199. The tracks 103 and 104 at the two sides of the bend 102 are connected by the flexible PCB 101 or flexible connector 101. The PCB 199 is made of rigid material.

Flexible PCB 101 or flexible connector 101 is one means of providing one or more electrical connections across a bend in a PCB. The electrical connection might be provided by a connector such as a wire, or any known electrical connector. The electrical connection across the bend may also be provided by electrical tracks on the PCB themselves traversing the bend.

Figure 2 shows a PCB 299 before it is bent. Tracks on the PCB 299 are connected to each other using a flexible connector 201 or a flexible PCB 201. This flexible connector 201 or flexible PCB 201 is mounted and soldered onto the rigid PCB 299 using techniques known in the art. The PCB 299 is then bent. For example, it may be bent using die bending, or bent by hand, or any way of applying force. In an embodiment, since there are no tracks, but a separate flexible connector 201 or flexible PCB 201 at the bend, the flexible connector or PCB 201 is bent without loss of electrical connectivity. In an alternate embodiment, the flexible PCB 201 or flexible connector 201 may be mounted and soldered after bending.

Figure 3 shows a PCB 399 before it is bent. A lead 301, or a single strand wire 301 is used as a jumper across the bend, to form an electrical connection. The wire 301 will bend after the PCB 399 itself is bent, but will continue to provide an electrical connection.

Figure 4 shows a PCB 499 before it is bent. A flexible wire 401, which may be a single or multi-strand wire is used as a jumper across the bend, to form an electrical connection. The wire 401 may be covered with an insulating sheath. This flexible wire 401 will easily bend, and not break, when the PCB 499 is bent, and will continue to provide an electrical connection.

Figure 5 shows a PCB 599 before it is bent. A metallic strip 501 is used as a jumper across the bend, to form an electrical connection. The metallic strip 501 is not flexible, but it bends easily and will deform permanently. The metallic strip 501 is bent as the PCB 599 is bent. The metallic strip 501 will not break after bending, and will continue to provide an electrical connection. The bending die will bend the metallic strip 501 as it bends the PCB 599.

Figure 6 shows a bent PCB 699 with mounted LEDs (light emitting diodes) 605. Other light producing devices, such as OLEDs, bulbs, electroluminescent light sources, etc. may be substituted. Due to the bending, part of the PCB 699 is horizontal, and part is vertical, with LEDs 605 mounted on the vertical part. The LEDs 605 are “top emitting” LEDs, and yet, throw light horizontally, since they are mounted vertically. Such LEDs 605 may throw light into a light guide, and the light guide may have light extraction features, such as dots, etching, shapes or light scattering particles (transparent particles of a different refractive index, or particles made of a light reflecting material). Thus, “top emitting” LEDs can be coupled to a light extracting light guide to create a light source.

The bent PCB 699 provides mechanical support for the vertically mounted LEDs 605. Electrical connections are provided to the LEDs 605. The electrical connections may jump across the bend using techniques given before. If the PCB 699 is an MCPCB, it provides thermal conductivity, draining the heat of the LEDs 605 away from the LEDs 605. The MCPCB may be mounted on a metallic or thermally conducting base, and will conduct the heat to this base. This base may be exposed to the atmosphere, or may be cooled by specific means such as forced coolant circulation. The PCB 699 may be thermally connected to the base using a thermally conductive epoxy.

Figure 7 shows a bent PCB 799 with mounted LEDs 705. The LEDs 705 are mounted in such a way that they are in a straight line, right behind one another, facing a single direction. This is achieved by bending parts 710 of the PCB 799 having these individual LEDs. Each bent part 710 of the PCB 799 may have one or more than one LEDs mounted on it. The LEDs 705 are “top emitting” LEDs, and yet, throw light sideways, because of the way they are mounted. In an embodiment, the LEDs may be mounted on both sides of the bent parts 710. The LED(s) on the back side of one bent part 710 will be directly facing (and in opposition to) the LED(s) on the front side of an adjoining bent part 710.

Figure 8 shows a PCB 899 with mounted LEDs 805 before it is bent. The PCB 899 has “L” shaped cuts 806 around the LEDs 805 to facilitate the bending of the LED sections into the final vertical position. The parts 810 of the PCB 899 carrying the LEDs 805 are bent by using a bending die or other means. In an embodiment, the bending die is made so as to bend parts 807 of the PCB 899 but not touch or impact the LEDs 805.

Figure 9 shows a multi-segment linear light source 999 with LEDs 905 on a bent PCB 910, and linear light guides 907. The LEDs 905 will emit light into linear light guides 907 having light extraction features. Each LED 905 (or group of LEDs on a single bent part) and linear light guide 907 pair will be a light producing segment, and thus, the entire assembly is a multi-segment linear light source 999.

The bent PCB 910 provides mechanical structure and support, and electrical connections. (In this case, the electrical connections jump across the bend, possibly using the techniques given above.) In the case of an MCPCB, the PCB 910 also provides thermal conductivity, and may be thermally mounted on a base onto which it conducts the heat of the LEDs 905 away.

This multi-segment linear light source 999 may be mounted on the side of a surface light guide with light extracting features. Thus a large surface light source is created, with LEDs 905 emitting light into linear light guides 907, which in turn emit light into the surface light source.

Figure 10 shows a metal sheet 1099, or other bendable sheet 1099. The sheet 1099 may be a reflector, or its surface may have a reflector deposited on it. For example, the sheet may be metallic, or may have a metallic coating (such as chrome coating). It may have reflective paint on it or a distributed Bragg reflector may be coated on to it. A Bragg reflector or other kind of specular reflection sheet may be pasted onto the bendable sheet 1099. The sheet will be bent along the dashed lines 1008 to produce a sheath for the linear light guides, possibly by die bending or other such methods. The sheet may have cuts 1006 (or slots) in it as shown, which after bending, will have inserted into them sections of a PCB (could be bent sections of a monolithic PCB) with LEDs mounted on the sections.

Figure 11 shows one segment of a linear light source 1199 having a bent sheet 1109 and a linear light guide 1107. The sheet 1109 may be bent using die bending, or may be created in this form using extrusion or molding. The sheet 1109 is bent so as to enclose three directions of the linear light guide 1107. Thus, light will come out of only one face of the linear light guide 1107. The sheet 1109 may be a reflector, in which case light emitted into the other directions will be redirected to come out of the said face, thus increasing efficiency. The bent sheet 1109 has a slightly narrowed opening 1111 compared to a slightly larger middle section 1112. The linear light guide 1107 may be press fit into the bent sheet 1109. The pressing will temporarily push the sides of the bent sheet 1109 slightly away, allowing the linear light guide 1107 to enter. The narrowed opening 1111 will then resume its original shape, thus mechanically holding the linear light source 1107 in place. The bent sheet 1109 may funnel out after the narrowed opening, to facilitate the temporary moving away of the sides of the bent sheet 1109 during insertion of the linear light guide 1107.

Many such segments of a linear light source 1199 are mechanically placed next to each other to form a multi-segment linear light source.

In an embodiment, the bent sheet 1109 has a cross section that touches the linear light guide 1107 cross section only at specific points. Thus, the linear light guide is held mechanically in place, but optically suspended in air (or vacuum or any surrounding material; in fact a low index material such as an aero-gel may be inserted in this void on purpose). The air is a low index material, thus improving the light guiding ability of the light guide 1107.

Figure 12 shows one segment of a linear light source 1299 with a bent sheet 1209, a bent PCB 1210, an LED 1205 (or a group of LEDs) and a linear light guide 1207. The bent sheet 1209 is mounted onto the PCB 1210 which may be mounted on a base. The bent sheet 1209 reflects light so that light can come out in one direction, and holds the linear light guide 1207 in place. The PCB 1210 mechanically supports the bent sheet 1209 and the LED 1205, and provides electrical connections to the LED 1205 using techniques disclosed above. It may also conduct the heat of the LED 1205 away.

The LED 1205 sends light into the linear light guide 1207. The linear light guide 1207 conducts the light from the LED 1205 from one end to the other end. The linear light guide 1207 has light extraction features such as geometric shapes, etching, diffusing surfaces, paint or pigment patterns or light scattering particles or pigmentation included in the bulk of the linear light guide 1207 which extract the light all over the body of the linear light guide 1207. The extracted light is guided by the bent sheet 1209 that specularly or diffusely reflects the light, so that it comes out of the opening of the bent sheet 1209.

The light extraction features may be present at varying occurrences or concentrations in the linear light guide 1207. For uniform light extraction, the concentration of light extraction feature must progressively increase further and further away from the LED 1205.

In an embodiment, LEDs are present on both the ends of the linear light guide 1207. The LED at the other side (not shown) may be situated at the back of the next bent section of the PCB. The light extraction features in this case increase as we move away from both the LEDs, i.e. increase towards the center of the linear light guide 1207.

Figure 13 shows a single side emitting multi-segment linear light source 1399 with a bent sheet 1309, a bent PCB 1310, LEDs 1305 and linear light guides 1307. The bent sheet 1309 is mounted onto the PCB 1310 which may be mounted on a base. The bent sheet 1309 has cuts 1306 in it on one or both sides, to allow the bent sections of the PCB 1310 having the LEDs 1305 mounted on them. The bent sheet 1309 reflects light in one direction, and holds the linear light guides 1307 in place. The PCB 1310 mechanically supports the bent sheet 1309 and the LEDs 1305, and provides electrical connections to the LEDs 1305 using techniques disclosed above. It may also conduct the heat of the LED 1305 away.

This assembly is thus a single-side-emitting multi-segment linear light source 1399. This light source may be coupled to a light guide surface having light extraction features, to create a surface light source.

A single side emitting, multi-segment linear light source is disclosed. It is understood that the embodiments described herein are for the purpose of elucidation and should not be considered limiting the subject matter of the present patent. Various modifications, uses, substitutions, recombinations, improvements, methods of productions without departing from the scope or spirit of the present invention would be evident to a person skilled in the art.

Claims

A system comprising a PCB having a plurality of bends, wherein electrical connections are connected across the bends.
The system of claim 1 wherein the electrical connections are flexible PCBs soldered onto the PCB.
The system of claim 1 wherein the electrical connections are PCB tracks.
The system of claim 1 wherein the electrical connections are wires.
The system of claim 1 wherein the electrical connections are metallic strips soldered onto the PCB.
The system of claim 1 further comprising a plurality of LEDs mounted on the plurality of bends.
The system of claim 6 further comprising a plurality of light guides, wherein the plurality of LEDs source light into the plurality of light guides.
The system of claim 7 wherein each light guide of the plurality of light guides contains light extracting features.
The system of claim 8 wherein the light extracting features are one of geometric shapes, etching, paint or pigment patters and light scattering particles.
The system of claim 8 further comprising a bent sheet, wherein the bent sheet reflects light emanating from each light guide of the plurality light guides such that light comes out from one face of the light guide.
The system of claim 10, wherein the bent sheet has slots in which bends from the plurality of bends fit.
The system of claim 10 wherein the bent sheet has a narrowing configured to hold the plurality of light guides in place, once they are within the bent sheet.
A method comprising, creating a connection on a PCB that connects two parts of a PCB, and bending the PCB such that the two parts are now not coplanar.
The method of claim 13 wherein the step of creating the connection comprises soldering a flexible PCB onto the PCB.
The method of claim 13 wherein the step of creating the connection comprises soldering a metallic strip onto the PCB.
The method of claim 13 wherein the step of creating the connection comprises soldering a wire onto the PCB.