LED device and LED lamp panel

Abstract

The invention relates to the technical field of LED packaging, and discloses an LED device and an LED lamp panel. An LED device comprises a substrate which is provided with a positive electrode bonding pad and a negative electrode bonding pad; a solder mask layer, a positive electrode and a negative electrode are arranged on a main body of the LED chip, the positive electrode and the negative electrode are partially exposed on the outer side of the solder mask layer, and a positive metal bump and a negative metal bump are respectively arranged on the positive electrode and the negative electrode; the LED chip is arranged on the substrate in an inverted mode, the positive electrode is connected with the positive bonding pad in a welded mode through the positive metal protruding block, and the negative electrode is connected with the negative bonding pad in a welded mode through the negative metal protruding block. When the LED device provided by the invention is subjected to secondary reflow soldering, the welding part of the LED chip is subjected to secondary melting, so that the positive electrode metal bump and the negative electrode metal bump are respectively backfilled to the welding part between the LED chip and the substrate; therefore, the problem that the welding spot at the welding position of the inverted LED chip is pulled by the thermal expansion force generated by the packaging glue during the secondary reflow soldering, so that the welding spot is hollow or cracked is solved.

Description

Technical Field

[0001] This invention relates to the field of LED packaging technology, and in particular to an LED device and an LED light board. Background Technology

[0002] With the rapid development of LCD technology in recent years, the trend towards larger screens, high dynamic range (HDR), and the demand driven by the "stay-at-home economy," Mini-LED display technology is gradually penetrating the application fields of medium and large-size displays, including TVs, commercial displays, and e-sports. Currently, the mainstream Mini-LED backlight products are integrated lamp boards, which include LED chips and ICs soldered together on a PCB. Specifically, this is achieved by packaging LED chips into individual SMD LED chips, and then packaging the LED chips and driver ICs together on the PCB. This is done using the commonly known POB (Package on Board) packaging technology, which is currently the most widely used packaging technology and is particularly prevalent in current Mini-LED display products.

[0003] Due to the high power, high integration, and high heat dissipation requirements of Mini-LED products, more and more LED chips are being packaged using flip-chip technology. The LED chip is only one component of the Mini-LED product. Generally, the LED chip is manufactured first and then packaged on the PCB together with components such as the driver IC. However, when the LED chip and driver IC are packaged together on the PCB, the LED chip undergoes a secondary reflow process. The solder at the LED chip packaging solder joint inside the LED chip melts a second time. At the same time, the encapsulating glue around the LED chip deforms when heated, which puts tensile stress on the LED chip and the chip solder joint, causing voids or cracks to appear at the solder joint of the LED chip.

[0004] Therefore, in existing technologies, LED chips are prone to problems such as voids or cracks at the solder joints of the LED chip inside the chip when packaged together with other electronic components, resulting in product defects. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide an LED device and an LED light board that can solve the problem in the prior art where the solder joints of the LED chips inside the lamp beads are prone to voids or cracks during the packaging process, leading to product defects.

[0006] The above-mentioned technical objective of the present invention is achieved through the following technical solution:

[0007] An LED device, comprising:

[0008] A substrate having a positive electrode pad and a negative electrode pad disposed thereon;

[0009] An LED chip is provided with a solder resist layer and a positive electrode and a negative electrode exposed on the outside of the solder resist layer. Positive and negative metal bumps are respectively provided on the positive and negative electrodes. The LED chip is flip-chip mounted on a substrate. The positive electrode is soldered to the positive pad through the positive metal bump. During reflow soldering, the positive metal bump can at least partially melt and fill the solder joint between the positive electrode and the positive pad. The negative electrode is soldered to the negative pad through the negative metal bump. During reflow soldering, the negative metal bump can at least partially melt and fill the solder joint between the negative electrode and the negative pad.

[0010] In one feasible embodiment, the positive electrode and the negative electrode are respectively formed by stacking Al layer, Ti layer, Pt layer, Ti layer, Ni layer and Au layer in sequence, with the Au layer located on the outermost side and connected to the corresponding positive electrode metal bump and the negative electrode metal bump respectively.

[0011] In one feasible embodiment, the positive electrode metal bump and the negative electrode metal bump have the same thickness, ranging from 10 μm to 100 μm.

[0012] In one feasible embodiment, a positive electrode soldering layer is provided on the positive electrode pad, a negative electrode soldering layer is provided on the negative electrode pad, the positive electrode and the positive electrode pad are connected by welding to the positive electrode soldering layer through the positive electrode metal bump, and the negative electrode and the negative electrode pad are connected by welding to the negative electrode soldering layer through the negative electrode metal bump.

[0013] In one feasible embodiment, the weld area of ​​the positive electrode welding layer is larger than the weld area of ​​the positive electrode metal bump, and / or, the weld area of ​​the negative electrode welding layer is larger than the weld area of ​​the negative electrode metal bump.

[0014] In one feasible embodiment, the positive electrode is composed of a plurality of positive sub-electrodes, each of the positive sub-electrodes having its exposed side separated from the outside of the solder resist layer by the solder resist layer, and the plurality of positive sub-electrodes being soldered together to the positive electrode pad; and / or, the negative electrode is composed of a plurality of negative sub-electrodes, each of the negative sub-electrodes having its exposed side separated from the outside of the solder resist layer by the solder resist layer, and the plurality of negative sub-electrodes being soldered together to the negative electrode pad.

[0015] In one feasible embodiment, the positive electrode is composed of a plurality of positive sub-electrodes, each of which is independently connected to the P-type semiconductor layer of the LED chip; or, the roots of the plurality of positive sub-electrodes are connected together and then connected to the P-type semiconductor layer of the LED chip.

[0016] In one feasible embodiment, the negative electrode is composed of a plurality of negative sub-electrodes, each of which is independently connected to the N-type semiconductor layer of the LED chip; or, the roots of the plurality of negative sub-electrodes are connected together and then connected to the N-type semiconductor layer of the LED chip.

[0017] The present invention also provides an LED light board, including a circuit board and the LED device, wherein the circuit board has a pre-set circuit route, and the LED device is disposed on the circuit board and electrically connected through the circuit route.

[0018] In one feasible embodiment, the LED chip is flip-chip disposed on the substrate using a first solder, and the LED device is disposed on the circuit board using a second solder, wherein the melting point of the second solder is lower than or equal to the melting point of the first solder.

[0019] By adopting the above technical solution, the present invention has at least the following beneficial effects:

[0020] The LED device provided by this invention increases the solder joint thickness between the LED chip and the substrate by setting a solder resist layer on the LED chip and exposing the positive and negative electrodes on the outside of the solder resist layer, combined with the setting of positive and negative metal bumps. This allows the LED chip solder joints to melt again during the second reflow soldering of the packaged LED device, causing the positive and negative metal bumps to fill the solder joints between the LED chip and the substrate. This avoids the problem of voids or cracks in the solder joints of the flip-chip LED chip being pulled by the thermal expansion force generated by the encapsulant during the second reflow soldering. It also allows for more flexible selection of the soldering temperature of compatible driver chips, connectors and other components during the reflow soldering of the subsequent assembly of the integrated lamp driver display module, ultimately achieving high reliability of the LED device and the integrated lamp driver display module. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the first structure of the LED device provided in the embodiment of the present invention;

[0022] Figure 2 This is a schematic diagram of the second structure of the LED device provided in the embodiment of the present invention;

[0023] Figure 3 This is a schematic diagram of another electrode structure of the LED device provided in an embodiment of the present invention;

[0024] Figure 4 This is a schematic diagram of the third structure of the LED device provided in the embodiments of the present invention;

[0025] Figure 5 This is a schematic diagram of the structure of the LED light board provided in an embodiment of the present invention.

[0026] In the attached diagram, 1 is the substrate; 11 is the positive electrode pad; 12 is the negative electrode pad; 13 is the positive electrode solder layer; 14 is the negative electrode solder layer; 2 is the LED chip; 21 is the solder resist layer; 22 is the positive electrode; 221 is the positive electrode sub-electrode; 23 is the negative electrode; 231 is the negative electrode sub-electrode; 24 is the positive electrode metal bump; 25 is the negative electrode metal bump; 10 is the circuit board; and 20 is the LED device. Detailed Implementation

[0027] The technical solution of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention.

[0028] In the description of this invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0029] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0030] Example 1

[0031] See Figure 1 , Figure 1 This is a schematic diagram of the first structure of the LED device provided in this embodiment. The LED device provided in this embodiment includes:

[0032] Substrate 1, wherein a positive electrode pad 11 and a negative electrode pad 12 are disposed on the substrate 1;

[0033] LED chip 2, the main body of LED chip 2 is provided with solder resist layer 21 and positive electrode 22 and negative electrode 23 exposed on the outside of solder resist layer 21. Positive electrode 22 and negative electrode 23 are respectively provided with positive electrode metal bump 24 and negative electrode metal bump 25. LED chip 2 is flip-chip mounted on substrate 1. The positive electrode 22 is soldered to the positive electrode pad 11 through the positive electrode metal bump 24. The positive electrode metal bump 24 can at least partially melt and fill the solder joint between the positive electrode pad 11 and the positive electrode pad 11 during reflow soldering. The negative electrode 23 is soldered to the negative electrode pad 12 through the negative electrode metal bump 25. The negative electrode metal bump 25 can at least partially melt and fill the solder joint between the negative electrode pad 12 and the negative electrode pad 12 during reflow soldering.

[0034] It is understood that the type of LED chip 2 is not limited here. Conventional chips from existing technologies can be used, or modifications can be made to the parts discussed in this embodiment. Parts not discussed can be understood and implemented with reference to existing technologies. In this embodiment, the substrate 1 is mainly used to mount the LED chip 2. The substrate 1 can also be combined with other structures of conventional LED devices to form a support. For example, a reflective cup is typically placed on the substrate 1 to form the overall support for the LED device. After the LED chip 2 is flip-chip soldered onto the substrate 1, encapsulating adhesive is generally applied to the outside of the LED chip 2 using a dispensing method. Encapsulating adhesive is a conventional material in the art, mainly used to protect the LED chip 2 and allow light to pass through. The type of encapsulating adhesive can be selected according to actual needs, such as fluorescent adhesive or various resin materials, etc., which will not be further described or illustrated here. The specific implementation of the flip-chip LED chip 2 mounting, the basic structure of the substrate 1, and the encapsulating adhesive are mature technologies in the art. Parts not discussed in this embodiment can be understood and implemented with reference to existing technologies by those skilled in the art, and will not be further described here. The substrate 1 is generally a PCB board or carrier board in this field, and generally includes a substrate body and a circuit structure. The shape of the substrate body is not strictly limited and can be square, round or irregular. The substrate body can be made of rigid material, such as, but not limited to, phenolic paper laminate, epoxy paper laminate, polyester glass mat laminate, epoxy glass cloth laminate, BT resin board, or glass plate; the substrate body can also be made of flexible material, such as, but not limited to, polyester film, polyimide film, or fluorinated ethylene propylene film. In some examples, corresponding circuits can be integrated into or on the substrate body according to application requirements, such as, but not limited to, circuits connected to LED chip 2 and driving circuits, etc. Alternatively, a conductive layer can penetrate the substrate 1 and lead out pads on both sides of the substrate 1 to facilitate the connection of flip-chip LED chip 2 on one side, and the pads on the other side can be electrically connected to the PCB or other components, so that LED chip 2 can be connected to other display modules. More specific situations will not be described further here.

[0035] It is understood that the metal bumps (including positive metal bump 24 and negative metal bump 25) can be understood as solder, which can melt and form a solder joint during reflow soldering. They can be one or a combination of Pb (lead), Sn (tin), Sb (antimony), Zn (zinc), Bi (bismuth), Au (gold), Ag (silver), Cu (copper), and their alloys. In this embodiment, Sn (tin) is used as the material for the metal bumps, i.e., tin bumps are used as an example. The solder resist layer 21 can be ink commonly used in the art, such as epoxy resin ink and other possible types. In this embodiment, it is mainly used to prevent the solder, such as the metal bumps, from flowing to non-target areas of the chip during soldering, reducing the risk of bridging or short circuits. Figure 1 As shown in the illustration, in this embodiment, the solder mask layer 21 around the positive electrode 22 and the negative electrode 23 is designed to be flat and have an area larger than the metal bump. This is to ensure that the metal bump will not flow to non-target areas when it melts during the subsequent reflow of the LED device. The specific size can be easily adjusted according to actual needs, and will not be described further here. Furthermore, the metal bump can be formed by depositing solder onto the corresponding electrode through screen printing or dotting, and then forming the metal bump (Sn bump) through reflow soldering. The shape of the metal bump can be automatically formed during reflow soldering, and generally tends to be spherical. The specific shape can be set according to actual conditions and is not strictly limited.

[0036] In this embodiment, the positive electrode 22 and the negative electrode 23 are respectively formed by stacking Al layer, Ti layer, Pt layer, Ti layer, Ni layer and Au layer in sequence. The Au layer is located on the outermost side and is connected to the corresponding positive electrode metal bump and the corresponding negative electrode metal bump. The Al layer, Ti layer, Pt layer, Ni layer and Au layer are aluminum, titanium, platinum, nickel, gold and their alloy materials, respectively. Specifically, the above material layers can be deposited in the electrode holes in one step by vapor deposition to form the corresponding electrode. The thickness of each layer of the electrode material can be selected according to the actual situation. For example, in this embodiment, the Ni layer thickness can be designed to be 1000 nanometers and the Au layer thickness can be designed to be 100 nanometers to ensure sufficient conductivity and welding connection performance. For more detailed design, those skilled in the art can adjust the design according to the actual situation.

[0037] In this embodiment, the positive electrode metal bump 24 and the negative electrode metal bump 25 have the same thickness, ranging from 10 μm to 100 μm. Specifically, the consistent thickness of the positive electrode metal bump 24 and the negative electrode metal bump 25 in this embodiment is mainly to ensure that after the positive electrode metal bump 24 and the negative electrode metal bump 25 are formed on the corresponding electrodes, their orientation is consistent with the height of one side of the positive electrode pad 11 and the negative electrode pad 12. To ensure consistent thickness, the metal bumps can be uniformly ground after the metal bumps are formed in the reflow soldering process. At the same time, to ensure that the metal bumps can effectively fill the solder joints in the subsequent secondary reflow, the thickness of the metal bumps after grinding is preferably 10 to 100 μm.

[0038] In this embodiment, a positive electrode soldering layer 13 is provided on the positive electrode pad 11, and a negative electrode soldering layer 14 is provided on the negative electrode pad 12. The positive electrode 22 is connected to the positive electrode pad 11 by welding to the positive electrode soldering layer 13 through the positive electrode metal bump 24, and the negative electrode 23 is connected to the negative electrode pad 12 by welding to the negative electrode soldering layer 14 through the negative electrode metal bump 25.

[0039] It is understandable that by setting the positive electrode solder layer 13 and the negative electrode solder layer 14, the LED chip 2 can be quickly fused and soldered directly to the metal bumps on the corresponding positive electrode 22 and negative electrode 23 during reflow soldering of the substrate 1. The positive electrode solder layer 13 and the negative electrode solder layer 14 can be made of the same material as the metal bumps, such as tin. It is understandable that, such as... Figure 1 As shown, when reflow soldering is performed, the LED chip 2 is stretched, and the molten positive metal bump 24 can fill the joint with the positive solder layer 13 to ensure that the solder joint will not have voids or cracks. The negative metal bump 25 is similar, and will not be described again here.

[0040] In this embodiment, as Figure 2 As shown, Figure 2 This is a schematic diagram of the structure of the second type of LED device provided in this embodiment. The welding area of ​​the positive electrode bonding layer 13 is larger than the welding area of ​​the positive electrode metal bump 24, and / or, the welding area of ​​the negative electrode bonding layer 14 is larger than the welding area of ​​the negative electrode metal bump 25. It can be understood that designing a larger welding area for the positive electrode bonding layer 13 and the negative electrode bonding layer 14 can effectively ensure the effectiveness of the welding by increasing the contact area between the positive electrode metal bump 24, the negative electrode metal bump 25 and the substrate 1 when the LED chip 2 is flip-chip mounted onto the substrate 1. Simultaneously, it prevents the positive electrode metal bump 24 and the negative electrode metal bump 25 from flowing to non-target areas, thereby improving product reliability and welding accuracy.

[0041] In this embodiment, as Figure 3 As shown, Figure 3 This is a schematic diagram of another electrode structure provided in this embodiment. The positive electrode 22 is composed of a plurality of positive sub-electrodes 221. The side of each positive sub-electrode 221 exposed outside the solder resist layer 21 is separated from each other by the solder resist layer 21. The plurality of positive sub-electrodes 221 are soldered together to the positive electrode pad 11. And / or, the negative electrode 23 is composed of a plurality of negative sub-electrodes 231. The side of each negative electrode 231 exposed outside the solder resist layer 21 is separated from each other by the solder resist layer 21. The plurality of negative electrode 231 are soldered together to the negative electrode pad 12.

[0042] It is understandable that the above situations include three scenarios: First, the positive electrode 22 is composed of multiple positive sub-electrodes 221, and the negative electrode 23 is composed of a single, integral electrode; second, the positive electrode 22 is composed of a single, integral electrode, and the negative electrode 23 is composed of multiple negative sub-electrodes 231; third, the positive electrode 22 is composed of multiple positive sub-electrodes 221, and the negative electrode is composed of multiple negative sub-electrodes 231. The design can be adjusted according to actual needs, with the third scenario being preferred. Figure 3 As shown, this embodiment uses the example of splitting the positive electrode 22 into two positive sub-electrodes 221 and the negative electrode 23 into two negative sub-electrodes 231. In other embodiments, the design can be simply modified according to actual needs.

[0043] Understandably, if the positive electrode 22 and negative electrode 23 are simply contacted and soldered to the metal bumps using a single large surface area, the large contact area makes it easy for the LED chip 2 to be pulled by the heated encapsulant during the second reflow process, resulting in voids at the contact surfaces between the positive electrode 22 or negative electrode 23 and the corresponding metal bumps that cannot be filled in time. However, in this embodiment, the positive electrode 22 and negative electrode 23 are composed of multiple positive sub-electrodes 221 and negative sub-electrodes 231, which is equivalent to increasing the contact edge between the electrode and the metal bumps. Even if the LED chip 2 is pulled by the encapsulant during the second reflow, resulting in voids, the small contact area allows the metal bumps around the sub-electrodes to melt and quickly fill the voids, reducing the contact area between a single electrode and the corresponding metal bumps, thereby reducing the possibility of voids.

[0044] Furthermore, in combination Figure 3 And such as Figure 4 As shown, Figure 4The diagram below illustrates the structure of the third type of LED device provided in this embodiment. It should be noted that the single integrated positive electrode 22 and negative electrode 23 are mainly connected to the corresponding positive pad 11 and negative pad 12 through a corresponding positive metal bump 24 and a corresponding negative metal bump 25. If the positive electrode 22 and negative electrode 23 are composed of multiple sub-electrodes, each individual positive sub-electrode 221 can be connected to a positive pad 11 through a corresponding positive metal bump 24, and each individual negative sub-electrode 231 can be connected to a negative pad 12 through a corresponding negative metal bump 25. In other words, multiple sub-electrodes can be connected to the same electrode pad on the substrate 1 through multiple metal bumps, minimizing modifications to the substrate 1 and reducing processing costs.

[0045] In one feasible embodiment, the positive electrode 22 is composed of a plurality of positive sub-electrodes 221, and the plurality of positive sub-electrodes 221 are independently connected to the P-type semiconductor layer of the LED chip 2; or, the roots of the plurality of positive sub-electrodes 221 are connected together and then connected to the P-type semiconductor layer of the LED chip 2.

[0046] It is understood that in some embodiments of the present invention, the positive electrode 22 of the LED chip 2 is designed to consist of multiple positive sub-electrodes 221, which can reduce the contact area between a single positive sub-electrode 221 and the positive metal bump 24, thereby avoiding voids. These positive sub-electrodes 221 can be formed as a whole and then their exposed end face on the side of the solder resist layer 21 can be divided into multiple positive sub-electrodes 221, or each positive sub-electrode 221 can be completely separated from each other and directly connected to the corresponding layer of the LED chip 2, that is, each positive sub-electrode 221 is independently connected to the P-type semiconductor layer of the LED chip 2. Furthermore, by first forming a whole and then dividing the exposed end face of the solder resist layer 21 into multiple positive electrode sub-electrodes 221, the process is convenient while effectively reducing voids. Each positive electrode sub-electrode 221 is completely isolated from each other and directly connected to the corresponding layer of the LED chip 2. This is equivalent to forming multiple parallel connections between the flip-chip LED chip 2 and the substrate 1, which effectively ensures the connection effect during secondary reflow. Even if some positive electrode sub-electrodes 221 are disconnected, the LED chip 2 will not be completely disconnected, reducing the risk of solder joint cracking and failure.

[0047] In one feasible embodiment, the negative electrode 23 is composed of a plurality of negative sub-electrodes 231, each of which is independently connected to the N-type semiconductor layer of the LED chip 2; or, the roots of the plurality of negative sub-electrodes 231 are connected together and then connected to the N-type semiconductor layer of the LED chip 2. The N-type and P-type semiconductor layers of the LED chip are part of the basic chip structure and can be understood by referring to existing technologies; further description is not provided here.

[0048] It is understood that in some embodiments of the present invention, the negative electrode 23 of the LED chip 2 is designed to consist of multiple negative sub-electrodes 231, which can reduce the contact area between a single negative sub-electrode 231 and the negative metal bump 25, thereby avoiding voids. These negative sub-electrodes 231 can be formed as a whole and then their exposed end face on the solder resist layer 21 side can be divided into multiple negative sub-electrodes 231, or each negative sub-electrode 231 can be completely separated from each other and directly connected to the corresponding layer of the LED chip 2, that is, each positive sub-electrode 221 is independently connected to the N-type semiconductor layer of the LED chip 2. Furthermore, by first forming a whole and then dividing the exposed end face of the solder resist layer 21 into multiple negative electrode sub-electrodes 231, the process is convenient while effectively reducing voids. Each negative electrode sub-electrode 231 is completely isolated from each other and directly connected to the corresponding layer of the LED chip 2. This is equivalent to forming multiple parallel connections between the flip-chip LED chip 2 and the substrate 1, which effectively ensures the connection effect during secondary reflow. Even if some negative electrode sub-electrodes 231 are disconnected, the LED chip 2 will not be completely disconnected, reducing the risk of solder joint cracking and failure.

[0049] The LED device provided by this invention increases the solder joint thickness between the LED chip and the substrate by setting a solder resist layer on the LED chip and exposing the positive and negative electrodes on the outside of the solder resist layer, combined with the setting of positive and negative metal bumps. This allows the LED chip solder joints to melt again during the second reflow soldering of the packaged LED device, causing the positive and negative metal bumps to fill the solder joints. This avoids the problem of voids or cracks in the solder joints of the flip-chip LED chip being pulled by the thermal expansion force generated by the encapsulant during the second reflow soldering. It also allows for more flexible selection of the soldering temperature of compatible driver chips, connectors and other components during the reflow soldering of the subsequent assembly of the integrated lamp driver display module, ultimately achieving high reliability of the LED device and the integrated lamp driver display module.

[0050] Example 2

[0051] See Figure 5 , Figure 5This is a schematic diagram of the structure of an LED light board provided in this embodiment. The LED light board provided in this embodiment includes a circuit board 10 and an LED device 20 as described in this invention. The circuit board 10 has a pre-set circuit route (not shown), and the LED device 20 is disposed on the circuit board 10 and forms an electrical connection through the circuit route.

[0052] It is understandable that the number of LED devices 20 on the LED light board can be adjusted according to actual needs; only a simple illustration is provided here.

[0053] In this embodiment, the LED chip is flip-chip mounted on the substrate using a first solder, and the LED device 20 is mounted on the circuit board using a second solder, wherein the melting point of the second solder is lower than or equal to the melting point of the first solder.

[0054] Specifically, in this embodiment, the first solder corresponds to the aforementioned metal bumps (including positive and negative metal bumps). As mentioned earlier, it can be various metal materials, such as solder paste, gold-based solder paste, silver-based solder paste, or other conventional low-melting-point solder pastes. The corresponding second solder can be composed of tin, silver, or other solders. The melting point of the second solder is generally not higher than that of the first solder, or it can be the same material as the first solder with the same melting point. Those skilled in the art can select and set it according to actual needs. For example, generally speaking, due to the difference in packaging processes between LED chips and electronic components, the melting point of the first solder used to package LED chips will be higher than or equal to the melting point of the second solder used to package LED devices and driver chips, etc. The specific selection of solder will not be further described here.

[0055] During SMT reflow soldering, the reflow oven temperature needs to be 20-30°C higher than the melting point of the second solder to ensure good solder melting and soldering results. This means that even if the melting point of the second solder is lower than that of the first solder, the SMT oven temperature will still be higher, leading to secondary melting of the first solder. Simultaneously, due to the high temperature, the encapsulating adhesive on the outside of the LED chip inside the LED device experiences thermal expansion, exerting an upward pulling force on the LED chip. This can cause poor soldering, voids, or cracks at the junction of the LED chip and solder paste, resulting in LED failure, affecting the quality of the LED device, producing defective products, and affecting the rework of the LED board. Furthermore, even if the LED chip and other component packages use the same solder, when the LED device is packaged together with other components on the circuit board, the solder at the LED chip's solder joint can still experience secondary melting due to the expansion and pulling of the encapsulating adhesive.

[0056] Therefore, the LED device included in the LED light board provided in this embodiment increases the welding thickness between the LED chip and the substrate by setting a solder resist layer on the LED chip and exposing the positive and negative electrodes on the outside of the solder resist layer, combined with setting positive and negative metal bumps. This allows the LED chip welding point to melt twice during the second reflow soldering of the packaged LED device, causing the positive and negative metal bumps to fill the welding point. This avoids the problem of voids or cracks in the solder joints of the flip-chip LED chip being pulled by the thermal expansion force generated by the encapsulant during the second reflow soldering. It also allows for more freedom in selecting the welding temperature of compatible driver chips, connectors and other components during the reflow soldering of the subsequent integrated lamp driver display module, ultimately achieving high reliability of the LED device and the integrated lamp driver display module.

[0057] It is understandable that, in addition to LED devices, other electronic components, such as driver chips, can be packaged on the circuit board according to actual needs. Soldering driver chips and other electronic components together with LED devices onto the circuit board is a conventional SMT (Surface Mount Technology) process in this field, which will not be elaborated here.

[0058] For any content not elaborated in detail in this embodiment, those skilled in the art can refer to the foregoing embodiments for understanding and implementation, and will not be further described here.

[0059] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. An LED device, characterized in that, include: A substrate having a positive electrode pad and a negative electrode pad disposed thereon; The LED chip has a solder resist layer and a positive electrode and a negative electrode partially exposed on the outside of the solder resist layer. Positive and negative metal bumps are respectively provided on the positive and negative electrodes. The LED chip is flip-chip mounted on the substrate. The positive electrode is soldered to the positive pad via the positive metal bumps. During reflow soldering, the positive metal bumps can at least partially melt and fill the solder joint between the positive electrode and the positive pad. The negative electrode is soldered to the negative pad via the negative metal bumps. During reflow soldering, the negative metal bumps can at least partially melt and fill the solder joint between the negative electrode and the negative pad.

2. The LED device according to claim 1, characterized in that, The positive electrode and the negative electrode are respectively formed by stacking Al layer, Ti layer, Pt layer, Ti layer, Ni layer and Au layer in sequence, with the Au layer located on the outermost side and connected to the corresponding positive electrode metal bump and the negative electrode metal bump respectively.

3. The LED device according to claim 1, characterized in that, The positive electrode metal bump and the negative electrode metal bump have the same thickness, ranging from 10 μm to 100 μm.

4. The LED device according to claim 1, characterized in that, A positive electrode soldering layer is provided on the positive electrode pad, and a negative electrode soldering layer is provided on the negative electrode pad. The positive electrode and the positive electrode pad are connected by welding to the positive electrode soldering layer through the positive electrode metal bump. The negative electrode and the negative electrode pad are connected by welding to the negative electrode soldering layer through the negative electrode metal bump.

5. The LED device according to claim 4, characterized in that, The weld area of ​​the positive electrode welding layer is larger than the weld area of ​​the positive electrode metal bump, and / or the weld area of ​​the negative electrode welding layer is larger than the weld area of ​​the negative electrode metal bump.

6. The LED device according to claim 1, characterized in that, The positive electrode is composed of a plurality of positive sub-electrodes, each of which is separated from the other by the solder resist layer on the side exposed outside the solder resist layer, and the plurality of positive sub-electrodes are soldered together to the positive electrode pad; and / or, the negative electrode is composed of a plurality of negative sub-electrodes, each of which is separated from the other by the solder resist layer on the side exposed outside the solder resist layer, and the plurality of negative sub-electrodes are soldered together to the negative electrode pad.

7. The LED device according to claim 6, characterized in that, The positive electrode is composed of several positive sub-electrodes, each of which is independently connected to the P-type semiconductor layer of the LED chip; or, the roots of several positive sub-electrodes are connected together and then connected to the P-type semiconductor layer of the LED chip.

8. The LED device according to claim 6, characterized in that, The negative electrode is composed of several negative sub-electrodes, each of which is independently connected to the N-type semiconductor layer of the LED chip; or, the roots of several negative sub-electrodes are connected together and then connected to the N-type semiconductor layer of the LED chip.

9. An LED light panel, characterized in that, The device includes a circuit board and an LED device as described in any one of claims 1 to 8, wherein the circuit board has a pre-set circuit path, and the LED device is disposed on the circuit board and electrically connected through the circuit path.

10. The LED light panel according to claim 9, characterized in that, The LED chip is flip-chip mounted on the substrate using a first solder, and the LED device is mounted on the circuit board using a second solder, wherein the melting point of the second solder is lower than or equal to the melting point of the first solder.

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