LED packaging structure having improved thermal dissipation and mechanical strength

The present disclosure involves a lighting apparatus. The lighting apparatus includes a thermally-conductive substrate. The thermally-conductive substrate may include a substrate. The lighting apparatus also includes a printed circuit board (PCB). The PCB is located besides the thermally-conductive substrate. The PCB and the thermally-conductive substrate have different material compositions. The lighting apparatus also includes a photonic device located over the thermally-conductive substrate. The photonic device may include a light-emitting diode (LED) die. The photonic device is thermally coupled to the thermally-conductive substrate. The photonic device is electrically coupled to the printed circuit board. The lighting apparatus also includes a thermal dissipation structure. The thermal dissipation structure is thermally coupled to the thermally-conductive substrate.

TECHNICAL FIELD

The present disclosure relates generally to light-emitting devices, and more particularly, to an improved packaging structure for light-emitting diode (LED) devices.

BACKGROUND

LED devices are semiconductor photonic devices that emit light when a voltage is applied. LED devices have increasingly gained popularity due to favorable characteristics such as small device size, long lifetime, efficient energy consumption, and good durability and reliability. In recent years, LED devices have been deployed in various applications, including indicators, light sensors, traffic lights, broadband data transmission, and illumination devices. For example, LED devices are often used in illumination devices provided to replace conventional incandescent light bulbs, such as those used in a typical lamp.

LED devices rely on a packaging structure for mechanical support and for heat dissipation. However, traditional LED packaging structures may suffer from inefficient heat dissipation and weak mechanical strength problems. Therefore, while existing packaging structures for LED devices have been generally adequate for their intended purposes, they have not been entirely satisfactory in every aspect. LED packaging structures having stronger mechanical strength and more efficient heat dissipation characteristics continue to be sought.

SUMMARY

One of the broader forms of the present disclosure involves a lighting apparatus. The lighting apparatus includes: a thermally-conductive substrate; a printed circuit board located besides the thermally-conductive substrate, the printed circuit board and the thermally-conductive substrate having different material compositions; a photonic device located over the thermally-conductive substrate, the photonic device being thermally coupled to the thermally-conductive substrate and electrically coupled to the printed circuit board; and a thermal dissipation structure thermally coupled to the thermally-conductive substrate.

In some embodiments, the thermally-conductive substrate includes a substrate free of electrical routing therein.

In some embodiments, the photonic device is thermally coupled to the thermally-conductive substrate through a thermally conductive but electrically insulating layer.

In some embodiments, the photonic device is electrically coupled to the printed circuited board through one or more metal pads.

In some embodiments, the photonic device includes one or more light-emitting diode (LED) dies.

In some embodiments, the thermally-conductive substrate is surrounded by the printed circuit board in a top view.

In some embodiments, a sidewall of the thermally-conductive substrate is spaced apart from a sidewall of the printed circuit board.

In some embodiments, the printed circuit board is attached to the thermal dissipation structure by one or more screws.

In some embodiments, the photonic device and the thermal dissipation structure are located on opposite sides of the thermally-conductive substrate.

Another one of the broader forms of the present disclosure involves a photonic lighting module. The photonic module includes: a heat sink; a substrate disposed over the heat sink and thermally coupled to the heat sink; a printed circuit board substrate disposed over the heat sink, the printed circuit board substrate surrounding the substrate; a plurality of metal pads disposed at least partially over the substrate and over the printed circuit board substrate; and one or more light-emitting devices disposed on a subset of the metal pads; wherein: the one or more light-emitting devices are thermally coupled to the heat sink through the substrate; and the one or more light-emitting devices are electrically coupled to the printed circuit board substrate through the metal pads.

In some embodiments, the light-emitting devices include light-emitting diodes.

In some embodiments, the photonic lighting module further includes: an electrically-insulating layer disposed between the substrate and the one or more light-emitting devices; and a thermally-conductive layer disposed between the substrate and the heat sink, the electrically-insulating layer and the thermally-conductive layer being disposed on opposite sides of the substrate.

In some embodiments, the substrate is free of being in physical contact with the printed circuit board substrate.

In some embodiments, the photonic lighting module further includes a cap disposed over the substrate, wherein the cap houses the one or more light-emitting devices therein.

In some embodiments, the printed circuit board substrate contains electrical routing circuitry; and the substrate contains no electrical routing circuitry.

Still another one of the broader forms of the present disclosure involves a packaging structure for a light-emitting device. The packaging structure includes: a printed circuit board structure having an opening that extends therethrough; a substrate positioned within the opening of the printed circuit board structure; a heat sink on which the printed circuit board structure and the substrate are located; a first metal pad located over the substrate, wherein the light-emitting device is thermally coupled to the first metal pad; and a second metal pad located over the printed circuit board substrate, wherein the second metal pad is electrically coupled to the light-emitting device.

In some embodiments, the light-emitting device includes a light-emitting diode die.

In some embodiments, a sidewall of the substrate is free of being in physical contact with a sidewall of the printed circuit board structure.

In some embodiments, the packaging structure further includes a cap disposed over the substrate and housing the light-emitting device therein.

In some embodiments, the packaging structure further includes a third metal pad disposed partially over both the substrate and the printed circuit board structure, wherein the third metal pad is electrically coupled to the second metal pad through a solder material and to the light-emitting device through a bonding wire.

Yet another one of the broader forms of the present disclosure involves a method of fabricating a photonic lighting apparatus. The method includes: obtaining a first substrate having a plurality of light-emitting diode (LED) dies disposed thereon, the LED dies being thermally coupled to the substrate; obtaining a second substrate, the second substrate including a printed circuit board (PCB) and an opening that extends therethrough the PCB; and placing the first substrate within the opening of the second substrate such that the LED dies are located above, and electrically coupled to, the second substrate.

In some embodiments, the first substrate has a first metal pad located on, and extends beyond, the first substrate; the second substrate has a second metal pad located thereon; and the placing is performed such that the first metal pad is placed on the second metal pad.

In some embodiments, the first metal pad is electrically coupled to at least one of the LED dies.

In some embodiments, the placing is performed such that a sidewall of the first substrate is free of being in physical contact with a sidewall of the second substrate defining the opening.

In some embodiments, the substrate is one of: a silicon substrate and a ceramic substrate.

In some embodiments, the PCB substrate includes one or more electrical routing layers electrically coupled to the second metal pad.

In some embodiments, the method further includes: attaching the first substrate and the second substrate to a heat sink.

DETAILED DESCRIPTION

It is understood that the following disclosure provides many different embodiments, or examples, for implementing different features of various embodiments. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. Moreover, the terms “top,” “bottom,” “under,” “over,” and the like are used for convenience and are not meant to limit the scope of embodiments to any particular orientation. Various features may also be arbitrarily drawn in different scales for the sake of simplicity and clarity. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself necessarily dictate a relationship between the various embodiments and/or configurations discussed.

Semiconductor devices can be used to make photonic devices, such as light-emitting diode (LED) devices. When turned on, LED devices may emit radiation such as different colors of light in a visible spectrum, as well as radiation with ultraviolet or infrared wavelengths. Compared to traditional light sources (e.g., incandescent light bulbs), lighting instruments using LED devices as light sources offer advantages such as smaller size, lower energy consumption, longer lifetime, variety of available colors, and greater durability and reliability. These advantages, as well as advancements in LED fabrication technologies that have made LED devices cheaper and more robust, have added to the growing popularity of LED-based lighting instruments in recent years.

Nevertheless, existing LED devices may face certain shortcomings. One such shortcoming is that the packaging structure for conventional LED devices may have weak mechanical strength and/or poor heat dissipation characteristics. Mechanically-weak LED packaging structures may result in physical failures such as breaking of the packaging structure, and inefficient heat dissipation may degrade the light output uniformity of the LED device and shorten the lifetime of the LED device. Therefore, it is desirable to improve the mechanical strength and heat dissipation capabilities of conventional LED packaging structures.

According to various aspects of the present disclosure, described below is a lighting apparatus that substantially improves light output uniformity and heat dissipation compared to traditional LED-based lighting instruments. Referring toFIG. 1, a diagrammatic fragmentary cross-sectional side view of a portion of a lighting instrument50is illustrated according to some embodiments of the present disclosure. The lighting instrument50includes a plurality of semiconductor photonic dies60as light sources. The semiconductor photonic dies60are LED dies in the present embodiment, and as such may be referred to as LED dies60in the following paragraphs.

The LED dies60each include two oppositely doped semiconductor layers. In one embodiment, the oppositely doped semiconductor layers each contain a “III-V” family (or group) compound. In more detail, a III-V family compound contains an element from a “III” family of the periodic table, and another element from a “V” family of the periodic table. For example, the III family elements may include Boron, Aluminum, Gallium, Indium, and Titanium, and the V family elements may include Nitrogen, Phosphorous, Arsenic, Antimony, and Bismuth. In the present embodiment, the oppositely doped semiconductor layers include a p-doped gallium nitride (GaN) material and an n-doped gallium nitride material, respectively. The p-type dopant may include Magnesium (Mg), and the n-type dopant may include Carbon (C) or Silicon (Si).

The LED dies60also each include a multiple-quantum well (MQW) layer that is disposed in between the oppositely doped layers. The MQW layer includes alternating (or periodic) layers of active material, such as gallium nitride and indium gallium nitride (InGaN). For example, the MQW layer may include a number of gallium nitride layers and a number of indium gallium nitride layers, wherein the gallium nitride layers and the indium gallium nitride layers are formed in an alternating or periodic manner. In one embodiment, the MQW layer includes ten layers of gallium nitride and ten layers of indium gallium nitride, where an indium gallium nitride layer is formed on a gallium nitride layer, and another gallium nitride layer is formed on the indium gallium nitride layer, and so on and so forth. The light emission efficiency depends on the number of layers of alternating layers and thicknesses.

It is understood that each LED die may also include a pre-strained layer and an electron-blocking layer. The pre-strained layer may be doped and may serve to release strain and reduce a Quantum-Confined Stark Effect (QCSE)—describing the effect of an external electric field upon the light absorption spectrum of a quantum well—in the MQW layer. The electron blocking layer may include a doped aluminum gallium nitride (AlGaN) material, wherein the dopant may include Magnesium. The electron blocking layer helps confine electron-hole carrier recombination to within the MQW layer, which may improve the quantum efficiency of the MQW layer and reduce radiation in undesired bandwidths.

The doped semiconductor layers and the MQW layer may all be formed by an epitaxial growth process known in the art. After the completion of the epitaxial growth process, an LED is created by the disposition of the MQW layer between the doped layers. When an electrical voltage (or electrical charge) is applied to the doped layers of the LED, the MQW layer emits radiation such as light. The color of the light emitted by the MQW layer corresponds to the wavelength of the radiation. The radiation may be visible, such as blue light, or invisible, such as ultraviolet (UV) light. The wavelength of the light (and hence the color of the light) may be tuned by varying the composition and structure of the materials that make up the MQW layer. The LED dies60may also include electrodes or contacts that allow the LED dies60to be electrically coupled to external devices.

In the embodiments illustrated inFIG. 1, the LED dies60have a phosphor layer70coated thereon. The phosphor layer70may include either phosphorescent materials and/or fluorescent materials. The phosphor layer70may be coated on the surfaces of the LED dies60in a concentrated viscous fluid medium (e.g., liquid glue). As the viscous liquid sets or cures, the phosphor material becomes a part of the LED package. In practical LED applications, the phosphor layer70may be used to transform the color of the light emitted by an LED dies60. For example, the phosphor layer70can transform a blue light emitted by an LED die60into a different wavelength light. By changing the material composition of the phosphor layer70, the desired light color emitted by the lighting instrument50may be achieved.

The lighting instrument50includes a cap80. The cap80provides a cover for the LED dies60therebelow. Stated differently, the LED dies60are encapsulated by the cap80and the substrate120collectively. In certain embodiments, the cap80may be transparent or translucent. In some embodiments, the cap80has a curved surface or profile. In some embodiments, the curved surface may substantially follow the contours of a semicircle, so that each beam of light emitted by the LED dies60may reach the surface of the cap80at a substantially right incident angle, for example, within a few degrees of 90 degrees. The curved shape of the cap80helps reduce Total Internal Reflection (TIR) of the light emitted by the LED dies60.

In some embodiments, the cap80has a diffusive and textured surface. For example, the textured surface may be roughened to help scatter the light emitted by the LED dies60, which makes the light output more uniform. In more detail, it would be undesirable to have a light output that is very intense (bright) in some directions or spots and weak (dim) in other directions or spots. The textured surface of the cap80allows incident light to be reflected in a plurality of different directions. Consequently, the result is that the light output is less likely to contain spots having varying degrees of brightness—thereby improving light output uniformity.

In some embodiments, a space90between the LED dies60and the cap80is filled by air. In another embodiment, the space90may be filled by an optical-grade silicone-based adhesive material, also referred to as an optical gel. Phosphor particles may be mixed within the optical gel in that embodiment so as to further diffuse light emitted by the LED dies60.

Though the illustrated embodiment shows all of the LED dies60being encapsulated within a single cap80, it is understood that a plurality of diffuser caps may be used in other embodiments. For example, each of the LED dies60may be encapsulated within a respective one of the plurality of diffuser caps.

In the embodiments illustrated inFIG. 1, the plurality of LED dies60are electrically coupled together in series by a plurality of bonding wires105. The LED dies may have other coupling configurations in other embodiments, however, for example they may be electrically coupled together in parallel. Furthermore, although the lighting instrument50includes a plurality of LED dies60in the embodiment illustrated inFIG. 1, other embodiments of the lighting instrument50may include and use a single LED die as its light source.

The LED dies60are located on metal pads110, respectively. The metal pads110are thermally conductive. In various embodiments, the metal pads110may include Aluminum, Copper, or another suitable metal or metal alloy. The metal pads110facilitate the dissipation of the heat (thermal energy) generated by the LED dies60. Two of the LED dies60located at the opposite ends of the series coupling are also electrically coupled to metal pads120through bonding wires125. In some embodiments, the metal pads120may have a composition substantially similar to that of the metal pads110. Through the metal pads120, electrical connections between the LED dies60and external devices may be established.

The metal pads110and120are located on a layer140. The layer140includes a thermally conductive material, which helps facilitate the dissipation of heat produced by the LED dies60. In some embodiments, the layer140may also be electrically insulating. For example, the layer140may include a ceramic material or a thermal glue material, which are both thermally conductive yet electrically insulating materials.

The layer140is located on a substrate150, which may be made of silicon or a ceramic material. The substrate150has good thermal conductivity and further facilitates the dissipation of heat produced by the LED dies60. While silicon may be suitable for manufacturing due to a lower cost than ceramic, the ceramic substrate offers good thermal conductivity. In some embodiments, the substrate150has a horizontal dimension (width)160and a vertical dimension (thickness or height)170as shown inFIG. 1. In some embodiments, the horizontal dimension160is in a range from about a few hundred microns to about a few centimeters, and the vertical dimension170is in a range from about 50 microns to about 1 millimeter. The horizontal dimension160and the vertical dimension170are also positively correlated (e.g., proportional to each other). In some embodiments, a higher value of the horizontal dimension160corresponds to a higher value of the vertical dimension170, and vice versa. In other words, as the surface area of the substrate150expands, it becomes thicker. Conversely, as the surface area of the substrate150shrinks, it becomes thinner. This type of configuration helps ensure that the substrate150does not become brittle or breakable.

The substrate150is located on an interlayer material180. The interlayer material180is thermally conductive and further facilitates heat dissipation. In various embodiments, the interlayer180may include thermal grease, one or more thermally-conductive pads (e.g., metal pads), solder, etc.

The interlayer material180is located on a thermal dissipation structure200, also referred to as a heat sink200. The heat sink200is thermally coupled to the LED dies60through the metal pads110, the layer140(which includes a thermally conductive material as discussed above), the substrate150(which may be either silicon or ceramic as discussed above), and the interlayer material180(which may include thermal grease, metal pads, or solder, as discussed above). The heat sink200is configured to facilitate heat dissipation to the ambient atmosphere. The heat sink200contains a thermally conductive material, such as a metal material. The shape and geometries of the heat sink200may be designed to provide a framework for a familiar light bulb while at the same time spreading or directing heat away from the LED dies60. To enhance heat transfer, the heat sink200may have a plurality of fins210that protrude outwardly from a body of the heat sink200. The fins210may have substantial surface area exposed to ambient atmosphere to facilitate heat transfer.

From the discussions above, it can be seen that certain aspects of the present disclosure pertain to effective heat dissipation through a silicon substrate, for example the substrate150. Thermal energy is conducted from the LED dies60to the thermal dissipation structure200through the substrate150(among other components). Silicon is a relatively efficient thermal energy transfer medium. In comparison, many traditional LED-based illumination devices use a Metal Core Printed Circuit Board (MCPCB) to conduct thermal energy from the LED dies to the heat sink. Though a typically MCPCB includes metal, which is thermally conductive, it also typically includes one or more dielectric layers that are not good thermal conductors. Thus, the thermal conduction performance for an MCPCB is worse than that of silicon. In other words, the lighting instrument50illustrated herein possesses superior heat dissipation characteristics through the use of a substrate150, rather than an MCPCB. Furthermore, MCPCBs are more expensive than silicon substrates. Therefore, the use of the substrate150(as opposed to the MCPCB) to dissipate heat herein also saves fabrication costs.

According to various embodiments of the present disclosure, since the substrate150is used herein to facilitate the dissipation of thermal energy, it is free of dielectric layers, which tend to have poor thermal conduction characteristics. As such, the substrate150is free of electrical routing layers. Instead, the electrical routing tasks are performed by a printed circuit board (PCB) substrate220. As shown inFIG. 1, the PCB substrate220is located horizontally adjacent to the substrate150. The sidewalls of the PCB substrate220and the sidewalls of substrate150are spaced apart by a small distance. In other words, there may be a gap between the PCB substrate220and the substrate150. The gap may be filled by air or another electrically-insulating material. In some embodiments, the PCB substrate220surrounds (or at least partially surrounds) the substrate150in a top view. Several example top views are shown inFIGS. 2-4and are discussed later.

Still referring toFIG. 1, the PCB substrate220is attached to the thermal dissipation structure200by fixing screws230in the illustrated embodiments. In alternative embodiments, the PCB substrate220may be secured to the thermal dissipation structure200by other suitable mechanisms. In some embodiments, the PCB substrate220has one or more electrical routing layers that can carry out the routing of electrical signals. The electrical routing layers may contain metal traces, vias, and other suitable passive or active electronic circuit components. Electrical connectivity to the PCB substrate220is obtained through metal pads240, which may be located on an upper surface of the PCB substrate220. These metal pads240are electrically coupled to metal pads250through solder materials260. The metal pads250are also electrically coupled to the metal pads120. In this manner, electrical connections to the LED dies60may be established through the metal pads120,250,240, and the PCB substrate220. In certain embodiments, however, the PCB substrate220need not contain electrical routing layers. Instead, the electrical connections between the LED dies60and external devices may be established through the metal pads120,250, and240.

Since the electrical routing functions are performed at least in part by the PCB substrate220, the substrate150only needs to handle the heat dissipation for the LED dies60. As the LED dies60collectively occupy a limited (e.g., relatively small) area, the substrate150need not have a great size to perform its heat dissipation task effectively. For example, the horizontal dimension160of the substrate150may exceed the horizontal area collectively occupied by the LED dies60, or an area covered by the cap80, but not by much. This is because silicon is a brittle material, and as the size of the substrate150increases, the more breakable it becomes. A relatively small size for the substrate150will increase its mechanical strength and durability.

In some embodiments, the size of the substrate150is configured while taking both thermal dissipation and breakability into considerations. Thus, the size (e.g., the dimension160) of the substrate150may be configured to be large enough to effectively facilitate heat transfer, but still small enough to avoid mechanical breaking issues. In other words, the design of the substrate150may involve making a tradeoff between heat dissipation and mechanical durability.

FIGS. 2-4are simplified diagrammatic fragmentary top views of the lighting instrument50according to various embodiments. In more detail,FIGS. 2-4illustrate top views of lighting instruments50A-50C, respectively, wherein the cross-sectional views of these lighting instruments50A-50C may be obtained by “cutting” along a dashed line inFIGS. 2-4from point X to point X′. The resulting cross-sectional view of the lighting instruments50A-50C may be substantially similar to the cross-sectional view illustrated inFIG. 1. Also, for reasons of consistency and clarity, similar components are labeled the same throughoutFIGS. 1-4.

Referring toFIG. 2, the embodiment of the lighting instrument50A includes a plurality of LED dies (not illustrated) that are covered by the cap80. These LED dies are located on the substrate150, which is surrounded (or encircled) by the PCB substrate220. As discussed above, the substrate150has a relatively small area and thus has good durability and is not likely to break. In addition, since silicon has favorable thermal conduction characteristics, the substrate150can efficiently transfer the heat generated by the LED dies to the heat sink therebelow (not illustrated).

Meanwhile, the LED dies are electrically coupled to the metal pads250and240. These metal pads240-250may be used to gain electrical access to the LED dies. For example, the metal pad240on one side of the cap80may serve as an anode contact, and the metal pad240on the opposite side of the cap80may serve as a cathode contact, or vice versa. A voltage may be applied through the anode and cathode contacts to power on the LED dies so that they can illuminate light. In embodiments where additional electrical routing is needed, the PCB substrate220may contain various electrical routing layers to carry out the routing.

Referring now toFIG. 3, the lighting instrument50B is similar to the lighting instrument50A, in that the heat dissipation for the LED dies is performed using the substrate150, and that the electrical connections to the LED dies may be established through the PCB substrate220and the metal pads240-250. One difference between the lighting instrument50A ofFIG. 2and the lighting instrument50B ofFIG. 3is that the lighting instrument50B has more metal pads240-250. For example, in addition to the metal pads240-250on the “left” and “right” sides of the cap80, there are also metal pads240-250on the “top” and “bottom” sides of the cap80. Note that the terms “left,” “right,” “top,” and “bottom” are used herein as examples with reference to the top view ofFIG. 3, and they do not indicate any specific type of configuration relationship to the LED dies in actuality.

Referring now toFIG. 4, the lighting instrument50C is similar to the lighting instrument50A, in that the heat dissipation for the LED dies is performed using the substrate150, and that the electrical connections to the LED dies may be established through the PCB substrate220and the metal pads240-250. One difference between the lighting instrument50A ofFIG. 2and the lighting instrument50C ofFIG. 4is that the lighting instrument50C has relatively “big” metal pads240and250on either side of the cap80. These “big” metal pads250cover up a substantial portion of the substrate150from a top view. The outline or top-view profile of the substrate150is delineated as the dashed square that surrounds the cap80. Though the metal pads240-250are configured somewhat differently in the embodiments illustrated inFIG. 4, the intended operation of the lighting instrument50C is not substantially different from that of the lighting instrument50A or50B.

Note that the lighting instruments50A-50C may include additional components. For example, the lighting instruments50A-50C may include reflector cups (or another suitable reflective structure) for the reflection of light. For reasons of simplicity, however, these additional components are neither illustrated nor discussed herein.

FIG. 5is a flowchart of a method300for fabricating a lighting apparatus using a semiconductor photonic device as a light source according to various aspects of the present disclosure. The method300includes a block310, in which a substrate is provided or obtained. In some embodiments, the substrate is a silicon substrate. In other embodiments, the substrate may be a ceramic substrate. The substrate has a plurality of LED dies located thereon. The LED dies are thermal-conductively coupled to the substrate. The substrate also has a plurality of metal pads located thereon. In some embodiments, the LED dies may each be located on a respective one of the metal pads. Some of the metal pads also partially extend beyond the substrate. For example, the metal pads250ofFIG. 1may be viewed as the metal pads extending partially beyond the substrate150. The LED dies may be electrically coupled together in series through a plurality of bonding wires. The bonding wires may also electrically couple the LED dies with the metal pads extending beyond the substrate. The LED dies may also be coated with a phosphor material.

The method300includes a block320, in which a printed circuit board (PCB) substrate is provided or obtained. The PCB substrate contains an opening that extends therethrough (e.g., from a front side of the printed circuit board substrate to a back side). The PCB substrate may contain one or more electrical routing layers. The PCB substrate may also contain metal pads located on its front surface. For example, the metal pads240ofFIG. 1may be viewed as these metal pads.

The method300includes a block330, in which the substrate is placed within the opening of the PCB substrate. In other words, the substrate is “inserted” into the opening of the PCB substrate. The sidewall of the substrate is spaced apart (i.e., not touching) the sidewall of the PCB substrate. After the substrate is placed within the PCB substrate, the LED dies on the substrate are still located above the front surface of the PCB substrate. As a part of the insertion process, the metal pads (e.g., metal pads250ofFIG. 1) located on and extending beyond the substrate are also placed on the metal pads (e.g., metal pads240ofFIG. 1) located on the PCB substrate. These metal pads are electrically coupled together through a suitable process such as a soldering process. A solder material may be disposed between these metal pads to enhance the soldering process. Thus, the LED dies are electrically coupled to the PCB substrate, and may therefore be electrically accessed through the PCB substrate. For example, through the metal pads on the substrate and the PCB substrate, a voltage can be applied to areas of the PCB substrate to control the operation of the LED dies located on the substrate.

Additional processes may be performed before, during, or after the blocks310-330discussed herein to complete the fabrication of the lighting apparatus. For example, an encapsulation structure such as a diffuser cap may be formed over the LED dies to house the LED dies therein. Furthermore, the PCB substrate may have a plurality of openings, and the process discussed above may be performed to insert a plurality of substrates having LED dies located thereon into the openings of the PCB substrate. For the sake of simplicity, these additional processes are not discussed herein.

The lighting instrument50according to the embodiments disclosed herein offers advantages over existing semiconductor-based lighting products. However, not all advantages are necessarily discussed herein, and different embodiments may offer additional advantages, and that no particular advantage is necessarily required for all embodiments.

One advantage of the embodiments disclosed herein is that an MCPCB substrate is no longer required to perform thermal dissipation. MCPCBs typically have poor thermal conduction characteristics and are also expensive. In comparison, the substrate used herein is cheaper and have better thermal conduction capabilities. Hence, heat generated by the LED dies in operation can be quickly and efficiently dissipated without causing damage to the LED dies. In addition, since the substrate used herein is small, they are not as brittle or breakable as larger substrates.

Another advantage of the embodiments disclosed herein is the elimination of Through-Silicon-Vias (TSV). Existing approaches of using silicon substrates to dissipate heat for LED devices usually require TSVs to establish electrical connections to the LED dies. TSVs are expensive and require complex and lengthy fabrication processes to form. As one example, TSVs need to be shielded by an electrically-insulating material so that electrical leakage does not occur. Forming such electrically-insulating material in a silicon substrate is time consuming and costly. Here, since the thermal conduction is performed by the silicon substrate, and the electrical routing may be done using the PCB substrate and the metal pads located thereon, TSVs are no longer needed, thereby reducing fabrication time and cost.

FIG. 6illustrates a simplified diagrammatic view of a lighting module400that includes some embodiments of the lighting instrument50discussed above. The lighting module400has a base410, a body420attached to the base410, and a lamp430attached to the body420. In some embodiments, the lamp430is a down lamp (or a down light lighting module).

The lamp430includes the lighting instrument50discussed above with reference toFIGS. 1-5. In other words, the lamp430of the lighting module400includes an LED-based light source, a diffuser cap that encapsulate the LED light source therein, a small silicon substrate and a heat sink for dissipating the heat generated by the LED light source, and a PCB substrate and a plurality of metal pads for establishing electrical connections to the LED light source. Due at least in part to the advantages discussed above, the LED packaging for the lamp430is operable to dissipate heat effectively while enjoying good mechanical durability compared to traditional LED packaging. In addition, due at least in part to the improved heat dissipation capabilities, the lamp430can offer a longer lifetime compared to traditional LED lamps.