Flip-chip COB packaging circuit boards and electronic devices

Abstract

The present invention relates to a flip-chip COB package circuit board and electronic equipment. In the circuit board, an insulating layer is provided on the first surface of a first ceramic layer, a conductive layer is provided on the insulating layer, a second ceramic layer is connected to the second surface of the first ceramic layer, and the side of the second ceramic layer facing away from the first ceramic layer is connected to the third ceramic layer; a solder joint layer is provided on the conductive layer, and electrodes of each LED chip are connected to each solder joint layer; a temperature sensing unit is provided in a mounting hole of the second ceramic layer, a temperature-sensing metal conductive sheet is provided in a temperature-sensing area of ​​the first ceramic layer, the first ceramic layer is provided with a first via hole, the temperature-sensing metal conductive sheet is electrically connected to the conductive layer through the first via hole, an electric energy input end of the temperature sensing unit is electrically connected to the temperature-sensing metal conductive sheet, and the temperature sensing unit is attached to the temperature-sensing metal conductive sheet. This allows the temperature sensing unit to be close to the LED chip, and temperature conduction is performed using the temperature-sensing metal conductive sheet, so that the temperature sensing unit can accurately and sensitively detect the temperature of the LED chip.

Description

Technical Field

[0001] The present invention relates to the technical field of manufacturing flip-chip COB packaged circuit boards, in particular to flip-chip COB packaged circuit boards and electronic equipment. Background Art

[0002] LED (Light Emitting Diode) is a solid-state semiconductor device that can convert electrical energy into visible light. It has the advantages of low energy consumption, fast response, high brightness and long service life.

[0003] With the continuous development of LED technology, COB (Chip On Board) packaging has become widely used. Compared with traditional SMD (Surface Mount Device) packaging, COB packaging has a higher density of LED chips, resulting in a higher concentration of heat.

[0004] Flip-chip COB packaging uses a micro-bumping process to directly connect the LED chip to the circuit board, eliminating the gold wire bonding required in upright COB packaging. Flip-chip COB circuit boards are more sensitive to temperature. As the board's temperature rises, the flip-chip solder joints can easily experience CTE (Coefficient of Thermal Expansion) mismatch, leading to LED chip solder joint failure.

[0005] To address this issue, real-time temperature monitoring of COB circuit boards is necessary to prevent circuit board failure. A common temperature monitoring method involves mounting a surface-mount temperature sensor on the surface or back of the substrate to detect the COB circuit board's temperature. However, current surface-mount temperature sensors are located far from the LED chip, making it difficult to accurately detect temperature changes. Summary of the Invention

[0006] Based on this, it is necessary to provide a flip-chip COB packaging circuit board and electronic equipment.

[0007] A flip-chip COB package circuit board, comprising: a multi-layer ceramic substrate, a plurality of LED chips and a temperature sensing unit;

[0008] The multilayer ceramic substrate includes a conductive layer, an insulating layer, a first ceramic layer, a second ceramic layer, and a third ceramic layer, wherein the insulating layer is disposed on a first surface of the first ceramic layer, the conductive layer is disposed on the insulating layer, the second ceramic layer is connected to a second surface of the first ceramic layer, and a surface of the second ceramic layer facing away from the first ceramic layer is connected to the third ceramic layer;

[0009] A plurality of solder point layers are provided on the conductive layer, and the electrodes of the LED chips are connected to the corresponding solder point layers;

[0010] The second ceramic layer is provided with a mounting hole, the temperature sensing unit is arranged in the mounting hole, the second surface of the first ceramic layer has a temperature sensing area aligned with the mounting hole, the temperature sensing area is provided with a temperature-sensitive metal conductive sheet, the first ceramic layer is provided with a first via hole, the temperature-sensitive metal conductive sheet is electrically connected to the conductive layer through the first via hole, the power input end of the temperature sensing unit is electrically connected to the temperature-sensitive metal conductive sheet, and the temperature sensing unit is attached to the temperature-sensitive metal conductive sheet.

[0011] In one embodiment, the insulating layer is coated on the outside of each solder joint layer.

[0012] In one embodiment, the width of each solder joint layer gradually decreases from an end close to the LED chip to an end far away from the LED chip.

[0013] In one embodiment, the end surface of each solder joint layer close to one end of the LED chip is configured as an arc-shaped surface.

[0014] In one embodiment, the thermal expansion coefficients of the first ceramic layer, the second ceramic layer, and the third ceramic layer increase in sequence.

[0015] In one embodiment, a temperature control unit is further included. The temperature control unit is arranged on the surface of the multilayer ceramic substrate. The third ceramic layer is provided with a third via hole. The temperature sensing unit is electrically connected to the temperature control unit through the third via hole. The temperature control unit is electrically connected to the conductive layer.

[0016] In one embodiment, the temperature control unit is arranged on the side of the third ceramic layer facing away from the second ceramic layer, and the position of the temperature control unit on the third ceramic layer is staggered from the position of the mounting hole on the second ceramic layer. The side of the third ceramic layer facing away from the second ceramic layer is provided with a first circuit layer and a second circuit layer. The temperature control unit is connected to the third via through the first circuit layer. The first ceramic layer, the second ceramic layer and the third ceramic layer are provided with a fourth via at a position close to the outer edge of the conductive layer. The temperature control unit is connected to the fourth via through the second circuit layer, and the fourth via is connected to the conductive layer.

[0017] In one embodiment, the temperature sensing unit is connected to the third via via a wire.

[0018] In one embodiment, a light-transmitting adhesive layer is further included, wherein the light-transmitting adhesive layer is connected to the first ceramic layer and covers the outer side of each of the LED chips.

[0019] An electronic device comprises the flip-chip COB packaged circuit board described in any one of the above embodiments.

[0020] The above-mentioned flip-chip COB packaged circuit board and electronic device, through the above-mentioned structure, enable the temperature sensing unit to be close to the LED chip, and utilize the temperature-sensitive metal conductive sheet to perform efficient temperature conduction, so that the temperature sensing unit can accurately and sensitively detect the temperature of the LED chip. In addition, an insulating layer is provided on the surface of the first ceramic layer, and the conductive layer is supported by a flexible insulating layer. The insulating layer can utilize elastic deformation to adapt to the expansion or contraction of the LED chip, thereby absorbing stress and effectively avoiding CTE mismatch. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 Schematic diagram of a partial cross-sectional structure of a flip-chip COB package circuit board according to one embodiment;

[0023] Figure 2 Schematic diagram of a partial cross-sectional structure of a flip-chip COB package circuit board according to one embodiment;

[0024] Figure 3 A schematic diagram of a partial cross-sectional structure of a flip-chip COB package circuit board according to another embodiment;

[0025] Figure 4 This is a partially enlarged structural diagram of a flip-chip COB package circuit board according to another embodiment.

[0026] Description of reference numerals:

[0027] 10. Flip-chip COB package circuit board; 100. Multilayer ceramic substrate; 200. LED chip; 300. Temperature sensing unit; 310. Temperature-sensitive metal conductive sheet; 400. Temperature control unit; 110. First ceramic layer; 120. Second ceramic layer; 130. Third ceramic layer; 140. Conductive layer; 150. Insulating layer; 151. First insulating layer; 152. Second insulating layer; 160. Solder joint layer; 121. Mounting hole; 101. First via hole; 102. Second via hole; 103. Third via hole; 104. Fourth via hole; 105. Fifth via hole; 106. Sixth via hole; 131. First circuit layer; 132. Second circuit layer; 133. Third circuit layer; 122. Accommodating hole; DETAILED DESCRIPTION

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] like Figure 1 and Figure 2 As shown, it is a flip-chip COB package circuit board 10 according to an embodiment of the present invention, comprising: a multi-layer ceramic substrate 100, a plurality of LED chips 200 and a temperature sensing unit 300;

[0030] The multilayer ceramic substrate 100 includes a conductive layer 140, an insulating layer 150, a first ceramic layer 110, a second ceramic layer 120, and a third ceramic layer 130. The insulating layer 150 is disposed on a first surface of the first ceramic layer 110, the conductive layer 140 is disposed on the insulating layer 150, the second ceramic layer 120 is connected to a second surface of the first ceramic layer 110, and a surface of the second ceramic layer 120 facing away from the first ceramic layer 110 is connected to the third ceramic layer 130.

[0031] A plurality of solder joint layers 160 are provided on the conductive layer 140 , and electrodes of the LED chips 200 are connected to corresponding solder joint layers 160 ;

[0032] The second ceramic layer 120 is provided with a mounting hole 121, and the temperature sensing unit 300 is arranged in the mounting hole 121. The second surface of the first ceramic layer 110 has a temperature-sensing area aligned with the mounting hole 121, and the temperature-sensing area is provided with a temperature-sensitive metal conductive sheet 310. The first ceramic layer 110 is provided with a first via 101, and the temperature-sensitive metal conductive sheet 310 is electrically connected to the conductive layer 140 through the first via 101. The power input end of the temperature sensing unit 300 is electrically connected to the temperature-sensitive metal conductive sheet 310, and the temperature sensing unit 300 is attached to the temperature-sensitive metal conductive sheet 310.

[0033] In this embodiment, the multilayer ceramic substrate 100 is also referred to as an LTCC (Low Temperature Co-fired Ceramic) substrate. The multilayer ceramic substrate 100 includes multiple ceramic layers, each of which can also be referred to as a green ceramic sheet. The ceramic layers are joined together using mechanical axial compression. The ceramic hole defined in the second ceramic layer 120 accommodates the temperature sensing unit 300, and the first ceramic layer 110 and the second ceramic layer 120 are connected to seal the mounting hole 121. The specific installation process is as follows: first, a mounting hole 121 is formed by drilling a hole on the second ceramic layer 120, for example, by using laser drilling to drill a hole on the second ceramic layer 120 to form the mounting hole 121, a temperature-sensitive metal conductive sheet 310 is made on the second surface of the first ceramic layer 110 in the temperature-sensing area corresponding to the mounting hole 121 of the second ceramic layer 120, and a first via 101 connected to the temperature-sensitive metal conductive sheet 310 is made on the first ceramic layer 110, the temperature sensing unit 300 is installed on the temperature-sensitive metal conductive sheet 310, and the second surface of the first ceramic layer 110 is laminated with the first surface of the second ceramic layer 120 to close the mounting hole 121, the second surface of the second ceramic layer 120 is laminated with the third ceramic layer 130, and the first ceramic layer 110, the second ceramic layer 120 and the third ceramic layer 130 are press-fitted and connected, thereby obtaining the substrate layer of the multi-layer ceramic substrate 100. It is worth mentioning that the mounting hole 121 can be a blind hole or a through hole. For example, the mounting hole 121 is a blind hole with an opening toward the first ceramic layer 110 and a closed bottom. For example, the mounting hole 121 is a through hole, and the first ceramic layer 110 and the third ceramic layer 130 respectively close the two ends of the mounting hole 121.

[0034] In this embodiment, the LED chip 200 is manufactured using a flip-chip COB packaging method. The conductive layer 140 is electrically connected to each LED chip 200 through the solder joint layer 160. The conductive layer 140 is also connected to a power source for supplying power to each LED chip 200. In this embodiment, the first ceramic layer 110 supports the insulating layer 150, and the insulating layer 150 supports the conductive layer 140 and provides isolation between different circuits in the conductive layer 140, so that different circuits in the conductive layer 140 are insulated from each other.

[0035] In this embodiment, the conductive layer 140 can also supply power to the temperature sensing unit 300. Specifically, the conductive layer 140 is electrically connected to the temperature-sensitive metal conductive sheet 310 through the first via 101 of the first ceramic layer 110. In this way, the temperature-sensitive metal conductive sheet 310 is provided with corresponding welding positions to be connected with the pins of the temperature sensing unit 300. The pins of the temperature sensing unit 300 are provided at both ends of the temperature sensing unit 300. A sensing area is provided in the middle of the temperature sensing unit 300, and the sensing area is attached to the temperature-sensitive metal conductive sheet 310. In this way, the temperature-sensitive metal conductive sheet 310 can not only conduct electricity to the temperature sensing unit 300 and supply power to it, but also conduct heat. For example, the temperature-sensitive metal conductive sheet 310 includes multiple conductive sub-sheets, which are isolated from each other. Two or more first vias 101 are provided, each first via is connected to a conductive sub-sheet, and each conductive sub-sheet is provided with a welding position. The welding position of each conductive sub-sheet is connected to a pin of the temperature sensing unit 300. In this way, a short circuit of the power supply to the temperature sensing unit 300 can be avoided.

[0036] Specifically, the temperature-sensitive metal conductive sheet 310 is made of aluminum foil or copper foil and has good thermal conductivity. The conductive layer 140 is connected to the LED chip 200 and can absorb the heat generated by the light emission of the LED chip 200. The resistance of the conductive layer 140 itself will also cause it to generate heat. A conductive and thermally conductive material is injected into the first via hole 101. For example, copper is plated on the side wall of the first via hole 101. In this way, the heat of the conductive layer 140 can more accurately reflect the heat of the LED chip 200. The conductive layer 140 is connected to the temperature-sensitive metal conductive sheet 310 through the first via hole 101 and can conduct heat to the temperature-sensitive metal conductive sheet 310.

[0037] It should be understood that in traditional COB packaging circuit boards, the temperature sensor is mounted on the periphery of the circuit layer on the substrate surface, while the LED chip 200 is located within and connected to the circuit layer. This creates a significant distance between the temperature sensor and the LED chip 200, making it difficult to accurately detect temperature changes within the LED chip 200. In prior art CN107768366A, the temperature sensor is located within the component placement through-hole of the first functional green tile, separating the temperature sensor and the LED chip 200 by only one top green tile layer. This effectively reduces the distance between the temperature sensor and the LED chip 200 and improves temperature detection sensitivity. However, on the one hand, this structure is suitable for upright COB packaging, but not for flip-chip COB packaging. The reason is that an insulating layer 150 is provided on the surface of the substrate of the flip-chip COB packaging, and the insulating layer 150 is not conducive to temperature conduction. If the existing technology is directly used in the flip-chip COB solution, it will be affected by the insulating layer 150, resulting in insensitive detection of the temperature sensor. On the other hand, in the existing technology, the electrical interconnection wires are provided on the top raw ceramic sheet. For example, if the electrodes of the LED chip 200 are directly connected to the electrical interconnection wires, when the temperature rises, it is easy to cause CTE mismatch. The LED chip 200 and the raw ceramic sheet expand to different degrees due to temperature changes, generating internal stress, causing the solder joint layer 160 to be subjected to forces in opposite directions of displacement of the materials at both ends, and to withstand shear stress, causing the solder joint to deform or break. In order to avoid the above situation, in this embodiment, an insulating layer 150 is provided on the first surface of the first ceramic layer 110, and the elastic deformation of the insulating layer 150 is used to absorb stress, thereby avoiding CTE mismatch, and a thermally conductive temperature-sensitive metal conductive sheet 310 is provided on the second surface of the first ceramic layer 110. The heat conduction through the first via 101 and the temperature-sensitive metal conductive sheet 310 can compensate for the defect of decreased thermal conductivity due to the provision of the insulating layer 150.

[0038] Through the above-mentioned structure, this embodiment enables the temperature sensing unit 300 to be close to the LED chip 200, and utilizes the temperature-sensitive metal conductive sheet 310 for efficient temperature conduction, so that the temperature sensing unit 300 can accurately and sensitively detect the temperature of the LED chip 200. In addition, an insulating layer 150 is provided on the surface of the first ceramic layer 110, and the conductive layer 140 is supported by the flexible insulating layer 150. The insulating layer 150 can utilize elastic deformation to adapt to the expansion or contraction of the LED chip 200, thereby absorbing stress and effectively avoiding CTE mismatch.

[0039] To further avoid CTE mismatch, in one embodiment, Figure 2As shown, the insulating layer 150 is coated on the outside of each solder layer 160. In this embodiment, the insulating layer 150 includes a first insulating layer 151 and a second insulating layer 152. The first insulating layer 151 is disposed on the first surface of the first ceramic layer 110 and is provided with a second via 102 connected to the first via 101. The conductive layer 140 is disposed on the first insulating layer 151. The second insulating layer 152 is disposed on the first insulating layer 151 and is disposed between the circuits of the conductive layer 140 to isolate the circuits of the conductive layer 140. The height of the second insulating layer 152 on the first insulating layer 151 is greater than the height of the conductive layer 140 and less than or equal to the sum of the heights of the conductive layer 140 and the solder layer 160. The second insulating layer 152 is coated on the outside of the solder layer 160 and is connected to the solder layer 160. In this embodiment, the insulating layer 150 is covered on the outside of the solder joint layer 160. The insulating layer 150 can absorb the deformation energy of the conductive layer 140 and the solder joint layer 160, provide a buffer for the conductive layer 140 and the solder joint layer 160, and support the solder joint layer 160, thereby avoiding breakage or deformation of the solder joint layer 160 due to CTE mismatch.

[0040] To ensure that the insulating layer 150 has excellent flexibility and elasticity, and excellent thermal conductivity, so that it can transfer heat to the temperature sensing unit 300, in one embodiment, the insulating layer 150 is made of epoxy resin, wherein the epoxy resin is mixed with a thermally conductive filler, and the thermally conductive filler includes aluminum oxide. In this embodiment, the use of epoxy resin and the mixing of aluminum oxide in the epoxy resin can effectively improve the thermal conductivity of the insulating layer 150, thereby efficiently transferring heat from the LED chip 200 to the first ceramic layer 110 and to the temperature sensing unit 300. In one embodiment, the epoxy resin is a glass fiber reinforced epoxy resin. Glass fiber reinforced epoxy resin has excellent mechanical properties, good thermal stability, and thermal conductivity, and can well support the conductive layer 140 and the LED chip 200.

[0041] In one embodiment, thermally conductive silicone is filled in the mounting hole 121. In this embodiment, the thermally conductive silicone fills the gap between the temperature sensing unit 300 and the temperature-sensitive metal conductive sheet 310. In this embodiment, the use of thermally conductive silicone to fill the mounting hole 121 makes the temperature sensing unit 300 more secure within the mounting hole 121. In addition, thermally conductive silicone has insulating properties. Filling the gap between the temperature sensing unit 300 and the temperature-sensitive metal conductive sheet 310 with thermally conductive silicone can insulate the temperature sensing unit 300 and the temperature-sensitive metal conductive sheet 310 from all parts except the soldering points and pins, thereby preventing short circuits. In addition, the thermally conductive silicone can also efficiently transfer heat from the temperature-sensitive metal conductive sheet 310 to the temperature sensing unit 300, thereby improving the accuracy and sensitivity of temperature detection.

[0042] In one embodiment, the minimum spacing between adjacent conductive sub-sheets is greater than twice the aperture of the first via 101 and less than three times the aperture of the first via 101. In this embodiment, thermally conductive silicone is filled between adjacent conductive sub-sheets. In this way, a capacitor-like structure is formed between the conductive sub-sheets, which is prone to parasitic capacitance. Moreover, since the conductive sub-sheets are also connected to the first via 101, parasitic capacitance in two directions is generated. One is the capacitance formed between the edge electric fields of adjacent conductive sub-sheets, which is the lateral edge capacitance. The other is the longitudinal via conductive sub-sheet capacitance formed by the coupling of the vertical electric field between the first via and the adjacent conductive sub-sheet. The lateral edge capacitance C edge The size of C is inversely proportional to the spacing s between adjacent conductive sub-sheets. edge ∝1 / s, and the vertical via conductive chip capacitance C via The size of is related to the aperture d of the first via hole and the spacing s between adjacent conductive sub-sheets. The capacitance of the vertical via conductive sub-sheet is proportional to the coupling area A and inversely proportional to the sum of the aperture d of the first via hole and the spacing s between adjacent conductive sub-sheets, that is, C via ∝A / (s+d), and the coupling area A is inversely proportional to the spacing s between the conductive sub-sheets. The smaller the spacing s, the larger the electric field overlap area between adjacent conductive sub-sheets, and the larger the coupling area. It can be seen from this that when the aperture d of the first via is larger than the spacing s between adjacent conductive sub-sheets, the edge electric field attenuates significantly as the spacing increases, the lateral edge capacitance decreases significantly, and the vertical via conductive sub-sheet capacitance decreases due to the reduction in coupling area; when the aperture d of the first via is smaller than the spacing s between adjacent conductive sub-sheets, the lateral edge capacitance rises sharply, and the vertical via conductive sub-sheet capacitance increases due to the increase in coupling area. Therefore, in order to reduce parasitic capacitance, in this embodiment, the minimum spacing between adjacent conductive sub-sheets is greater than twice the aperture of the first via 101, that is, s≥2d, which can effectively suppress parasitic capacitance while meeting the LTCC process constraints and reliability requirements. In addition, it should be understood that the spacing s between adjacent conductive sub-sheets cannot be too large. If the spacing s is set to be large, it is easy to cause the overall area of ​​the temperature-sensitive metal conductive sheet 310 to be small, which is not conducive to heat conduction. Therefore, the minimum spacing between adjacent conductive sub-sheets is less than three times the aperture of the first via 101 , which can effectively maintain the overall area of ​​the temperature-sensitive metal conductive sheet 310 , ensure heat conduction efficiency, and improve the detection accuracy of the temperature sensing unit 300 .

[0043] In order to improve the strength of the solder joint layer 160 and prevent the solder joint layer 160 from breaking or deforming, in one embodiment, as shown in FIG. Figure 2As shown, the width of each solder layer 160 gradually decreases from the end closest to the LED chip 200 to the end further away from the LED chip 200. In this embodiment, the width of the top of each solder layer 160 is greater than the width of the bottom. This increases the connection area between the top of the solder layer 160 and the electrode of the LED chip 200, achieving a full connection with the LED chip 200, increasing the shear resistance area, and effectively preventing breakage. On the other hand, the bottom of the solder layer 160, being close to the insulating layer 150, can effectively utilize the buffering effect of the insulating layer 150 to avoid breakage. This improves the overall connection strength of the solder layer 160 and prevents breakage or deformation of the solder layer 160.

[0044] In one embodiment, Figure 2 As shown, the end surface of each solder layer 160 near one end of the LED chip 200 is configured as an arc-shaped surface. In this embodiment, the end surface of the solder layer 160 is configured as a curved surface, and the solder pads corresponding to the electrodes of the LED chip 200 are configured as arc-shaped bumps. This allows the two to align, thereby achieving geometric self-alignment to reduce local stress concentration and disperse shear stress in a direction parallel to the ceramic substrate to a direction perpendicular to the ceramic substrate, thereby reducing the lateral shear stress of the solder layer 160 and effectively preventing fracture or deformation of the solder layer 160.

[0045] In one embodiment, the width of each solder layer 160 gradually decreases from the end proximal to the LED chip 200 to the end distal to the LED chip 200, and the end surface of each solder layer 160 proximal to the LED chip 200 is configured as an arcuate surface. In this embodiment, the solder layer 160 is configured in an inverted trapezoidal shape. Due to the larger connection area between the top and the electrode of the LED chip 200, the shear resistance area is effectively increased, effectively preventing fracture. The arcuate top end surface effectively disperses shear stress in a direction parallel to the ceramic substrate to a direction perpendicular to the ceramic substrate, reducing the lateral shear stress of the solder layer 160. Furthermore, the larger arcuate end surface can better reduce local stress concentration, effectively preventing fracture or deformation of the solder layer 160.

[0046] In one embodiment, the thermal expansion coefficients of the first ceramic layer 110 , the second ceramic layer 120 , and the third ceramic layer 130 increase in sequence.

[0047] In this embodiment, the ceramic content in the first ceramic layer 110, the second ceramic layer 120 and the third ceramic layer 130 decreases successively. For example, the first ceramic layer 110 is formed by sintering ceramic, the second ceramic layer 120 is formed by sintering ceramic mixed with copper powder and glass powder, and the third ceramic layer 130 is formed by sintering ceramic mixed with aluminum powder. In this way, the metal powder content in the first ceramic layer 110, the second ceramic layer 120 and the third ceramic layer 130 increases successively. The thermal expansion coefficient (CTE) of the first ceramic layer 110 is 5 to 6.5 ppm / °C, the thermal expansion coefficient of the second ceramic layer 120 is 8 to 8.5 ppm / °C, and the thermal expansion coefficient of the third ceramic layer 130 is 10 to 12 ppm / °C. It should be understood that the thermal expansion coefficient of the LED chip 200 is 2.6 ppm / °C. The first ceramic layer 110 has a lower thermal expansion coefficient than the second ceramic layer 120 and the third ceramic layer 130, and has a thermal expansion coefficient closer to that of the LED chip 200, which can reduce the gap between the first ceramic layer 110 and the LED chip 200. The internal stress caused by the difference in thermal expansion between the layers can be avoided to avoid CTE mismatch. The metal powder content of the second ceramic layer 120 and the third ceramic layer 130 located at the bottom layer gradually increases, which can form a thermal expansion gradient between the three ceramic layers, gradually absorbing the stress caused by the expansion difference, so that the stress is dispersed. In addition, the second ceramic layer 120 and the third ceramic layer 130 with a higher metal powder content have higher hardness and strength, effectively supporting the first ceramic layer 110, and have a higher thermal conductivity, which can effectively absorb the heat of the upper layer and diffuse it to the outside, so that the heat dissipation effect of the multi-layer ceramic substrate 100 is better.

[0048] In one embodiment, Figure 3 As shown, the flip-chip COB package circuit board 10 also includes a temperature control unit 400, which is arranged on the surface of the multilayer ceramic substrate 100, and the third ceramic layer 130 is provided with a third via 103. The temperature sensing unit 300 is electrically connected to the temperature control unit 400 through the third via 103, and the temperature control unit 400 is electrically connected to the conductive layer 140.

[0049] In this embodiment, the temperature sensing unit 300 may be a surface-mount temperature sensor, and the temperature control unit 400 may be a temperature control chip. The temperature control unit 400 may also be referred to as an overheat protection control unit. The temperature control unit 400 transmits signals to the temperature sensing unit 300 via the third via 103. The temperature sensing unit 300 transmits the detected temperature signal to the temperature control unit 400. The temperature control unit 400 is configured to detect the temperature of the LED chip 200 and the multilayer ceramic substrate 100 via the temperature sensing unit 300. The temperature control unit 400 controls the current of the LED chip 200 by electrically connecting to the circuit on the conductive layer 140. When the temperature of the LED chip 200 and the multilayer ceramic substrate 100 exceeds a preset temperature, the current of the LED chip 200 is reduced, thereby reducing the brightness of the LED chip 200. This dynamically adjusts the temperature of the LED chip 200 to prevent overheating. It is worth mentioning that the prior art considers setting the thermal protection IC and the temperature sensor in the component placement through-hole at the same time. On the one hand, a placement hole with a larger area is required, and a larger hole needs to be opened in the second ceramic layer 120, which affects the rigidity of the second ceramic layer 120. On the other hand, the temperature control unit 400 is set in the placement hole, and a via needs to be set on the first ceramic layer 110. This will result in more vias in the temperature sensing area, increasing the parasitic capacitance generated by the via, and affecting the signal transmission of the circuit board. Therefore, in this embodiment, the temperature control unit 400 is set outside the mounting hole 121, and the third via 103 connecting the temperature control unit 400 and the temperature sensing unit 300 is set in the third ceramic layer 130, which avoids the third via 103 and the first via 101 being concentrated in the temperature sensing area at the same time, thereby reducing the parasitic capacitance.

[0050] In one embodiment, Figure 3 As shown, the temperature control unit 400 is arranged on the side of the third ceramic layer 130 facing away from the second ceramic layer 120, and the position of the temperature control unit 400 on the third ceramic layer 130 is staggered with the position of the mounting hole 121 on the second ceramic layer 120. The side of the third ceramic layer 130 facing away from the second ceramic layer 120 is provided with a first circuit layer 131 and a second circuit layer 132. The temperature control unit 400 is connected to the third via 103 through the first circuit layer 131. The first ceramic layer 110, the second ceramic layer 120 and the third ceramic layer 130 are provided with a fourth via 104 at a position close to the outer edge of the conductive layer 140. The temperature control unit 400 is connected to the fourth via 104 through the second circuit layer 132, and the fourth via 104 is connected to the conductive layer 140.

[0051] In this embodiment, the first circuit layer 131 and the second circuit layer 132 are formed on the back side of the third ceramic layer 130 by screen printing or mask printing, and are used to achieve electrical connection between the temperature control unit 400, the temperature sensing unit 300, and the conductive layer 140. The fourth via 104 is located near the outer edge of the conductive layer 140, and is at a greater distance from the third via 103. This effectively avoids the problem of large parasitic capacitance caused by concentrated vias. Furthermore, the temperature control unit 400 is staggered from the mounting hole 121, so that the temperature control unit 400 is located outside the mounting hole 121, away from the via, avoiding the influence of the via's parasitic capacitance, thereby improving signal integrity.

[0052] In one embodiment, the temperature sensing unit 300 is connected to the third via 103 via a wire (not shown). In this embodiment, one end of the wire is electrically connected to the signal pin of the temperature sensing unit 300, and the other end of the wire is connected to the third via 103, thereby achieving an electrical connection between the temperature sensing unit 300 and the third via 103. The connection process involves first soldering one end of the wire to the signal pin of the temperature sensing unit 300. After laminating the second ceramic layer 120 and the third ceramic layer 130, the other end of the wire is passed through the third via 103 of the third ceramic layer 130. Subsequently, copper plating is formed in the third via 103 to connect to the other end of the wire.

[0053] In one embodiment, Figure 4 As shown, a accommodating hole 122 is provided on the second ceramic layer 120 at a position close to the outer edge of the conductive layer 140, the temperature control unit 400 is provided in the accommodating hole 122, the third ceramic layer 130 is provided with a fifth via 105 in an area aligned with the accommodating hole 122, the first ceramic layer 110 is provided with a sixth via 106 in an area aligned with the accommodating hole 122, and the third ceramic layer 130 is provided with a third circuit layer 133 on a side facing away from the second ceramic layer 120, the position of the third via 103 on the third ceramic layer 130 is aligned with the temperature sensing area of ​​the first ceramic layer 110, the third via 103 is connected to the third circuit layer 133, the third circuit layer 133 is connected to the temperature control unit 400 through the fifth via 105, and the temperature control unit 400 is connected to the conductive layer 140 through the sixth via 106.

[0054] In this embodiment, the temperature control unit 400 is disposed within the receiving hole 122, separate from the temperature sensing unit 300 and placed in a different hole. This reduces the area of ​​each hole and avoids significantly affecting the overall rigidity of the second ceramic layer 120. The temperature control unit 400 is connected to the temperature sensing unit 300 via the fifth via 105, the third circuit layer 133, and the third via 103, and is connected to the conductive layer 140 via the sixth via 106, thereby achieving connection with the circuit of the conductive layer 140. Unlike the above embodiment, this embodiment does not place the temperature control unit 400 on the back side of the third ceramic layer 130, but rather within the receiving hole 122 of the second ceramic layer 120. This avoids the problem of reduced rigidity of the second ceramic layer 120 due to an excessively large single hole area. It also avoids the problem of increased parasitic inductance caused by an excessive length of the via (fourth via 104) connecting to the conductive layer 140, thereby effectively ensuring the integrity of signal transmission in the flip-chip COB package circuit board 10.

[0055] In this embodiment, the connection structure between the temperature control unit 400 and the fifth and sixth vias 105 and 106 in the receiving hole 122 can be similar to the connection structure between the temperature sensing unit 300 and the first and third vias 101 and 103 in the mounting hole 121. This will not be described in detail in this embodiment.

[0056] In one embodiment, the flip-chip COB package circuit board 10 further includes a light-transmitting adhesive layer, which is connected to the first ceramic layer 110 and covers the outer side of each of the LED chips 200 .

[0057] In this embodiment, the light-transmitting adhesive layer is used to encapsulate and protect each LED chip 200 and guide and diffuse the light emitted by the LED chip 200 to the outside. In this embodiment, the light-transmitting adhesive layer is made of a transparent epoxy resin mixed with fluorescent powder particles. This allows each LED chip 200 to be encapsulated by the light-transmitting adhesive layer, preventing the ingress of dust and moisture. Furthermore, the light-transmitting adhesive layer has good light transmittance and excellent light-scattering properties, resulting in more uniform and brighter light output from the flip-chip COB package circuit board 10.

[0058] In one embodiment, an electronic device is provided, comprising the flip-chip COB package circuit board 10 described in any one of the above embodiments.

[0059] In this embodiment, the structure of the flip-chip COB package circuit board 10 allows the temperature sensing unit 300 to be close to the LED chip 200. The temperature-sensitive metal conductive sheet 310 is used for efficient temperature conduction, allowing the temperature sensing unit 300 to accurately and sensitively detect the temperature of the LED chip 200. Furthermore, an insulating layer 150 is provided on the surface of the first ceramic layer 110. The flexible insulating layer 150 supports the conductive layer 140. The insulating layer 150 can adapt to the expansion or contraction of the LED chip 200 through elastic deformation, thereby absorbing stress and effectively avoiding CTE mismatch. This effectively increases the service life of the flip-chip COB package circuit board 10, thereby increasing the service life of the electronic device.

[0060] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0061] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A flip-chip COB package circuit board, characterized in that: include: Multilayer ceramic substrate, multiple LED chips and temperature sensing unit; The multilayer ceramic substrate includes a conductive layer, an insulating layer, a first ceramic layer, a second ceramic layer, and a third ceramic layer, wherein the insulating layer is disposed on a first surface of the first ceramic layer, the conductive layer is disposed on the insulating layer, the second ceramic layer is connected to a second surface of the first ceramic layer, and a surface of the second ceramic layer facing away from the first ceramic layer is connected to the third ceramic layer; A plurality of solder point layers are provided on the conductive layer, and the electrodes of the LED chips are connected to the corresponding solder point layers; The second ceramic layer is provided with a mounting hole, the temperature sensing unit is arranged in the mounting hole, the second surface of the first ceramic layer has a temperature sensing area aligned with the mounting hole, the temperature sensing area is provided with a temperature-sensitive metal conductive sheet, the first ceramic layer is provided with a first via hole, the temperature-sensitive metal conductive sheet is electrically connected to the conductive layer through the first via hole, the power input end of the temperature sensing unit is electrically connected to the temperature-sensitive metal conductive sheet, and the temperature sensing unit is attached to the temperature-sensitive metal conductive sheet.

2. The flip-chip COB packaging circuit board according to claim 1, characterized in that: The insulating layer is coated on the outside of each solder joint layer.

3. The flip-chip COB packaging circuit board according to claim 1, characterized in that: The width of each solder joint layer gradually decreases from an end close to the LED chip to an end far away from the LED chip.

4. The flip-chip COB packaging circuit board according to claim 1, characterized in that: The end surface of each soldering point layer close to one end of the LED chip is set as an arc surface.

5. The flip-chip COB packaging circuit board according to claim 1, characterized in that: The thermal expansion coefficients of the first ceramic layer, the second ceramic layer, and the third ceramic layer increase in sequence.

6. The flip-chip COB packaging circuit board according to claim 5, characterized in that: It also includes a temperature control unit, which is arranged on the surface of the multilayer ceramic substrate. The third ceramic layer has a third via hole. The temperature sensing unit is electrically connected to the temperature control unit through the third via hole. The temperature control unit is electrically connected to the conductive layer.

7. The flip-chip COB packaging circuit board according to claim 6, characterized in that: The temperature control unit is arranged on the side of the third ceramic layer facing away from the second ceramic layer, and the position of the temperature control unit on the third ceramic layer is staggered from the position of the mounting hole on the second ceramic layer. The side of the third ceramic layer facing away from the second ceramic layer is provided with a first circuit layer and a second circuit layer. The temperature control unit is connected to the third via through the first circuit layer. The first ceramic layer, the second ceramic layer and the third ceramic layer are provided with a fourth via at a position close to the outer edge of the conductive layer. The temperature control unit is connected to the fourth via through the second circuit layer, and the fourth via is connected to the conductive layer.

8. The flip-chip COB packaging circuit board according to claim 6, characterized in that: The temperature sensing unit is connected to the third via hole through a wire.

9. The flip-chip COB package circuit board according to any one of claims 1 to 8, characterized in that: It also includes a light-transmitting adhesive layer, which is connected to the first ceramic layer and covers the outer side of each of the LED chips.

10. An electronic device, characterized in that: The invention comprises the flip-chip COB package circuit board described in any one of claims 1 to 9.

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