Flip-chip LED chips, circuit boards and electronic devices

Abstract

An embodiment of the present invention provides a flip-chip LED chip, a circuit board, and an electronic device, wherein two upwardly concave solder pad grooves are provided at the bottom of the chip body of the flip-chip LED chip, the N-pole solder pad and the P-pole solder pad are respectively provided at the bottom of a solder pad groove, and there is a gap between the side of the solder pad and the side wall of the solder pad groove, the cross-sectional area of ​​the solder pad groove gradually increases from the bottom of the groove to the groove opening, and the side wall of the solder pad groove is inclined in a direction away from the solder pad from the bottom of the solder pad groove to the groove opening. Therefore, in the process of soldering the flip-chip LED chip to the circuit board, the molten solder paste can penetrate into the gap and combine with the side of the solder pad, so that the collection of the solder paste and the solder pad is more complete, thereby improving the reliability of the soldering of the flip-chip LED chip and the circuit board, and can significantly improve the yield rate of the flip-chip LED chip.

Description

[0001] This application is a divisional application of the original Chinese invention patent application entitled “Flip-chip LED chip, circuit board, and electronic device.” The original application number is 201911222587.X and the filing date is December 3, 2019. Technical Field

[0002] The present invention relates to the field of electronics, and in particular to a flip-chip LED chip, a circuit board and an electronic device. Background Art

[0003] For Mini LED applications, the die bonding process uses a flip-chip printing process: each circuit board typically has thousands, or even millions, of solder joints connecting the LED chips. This massive number of solder joints poses significant challenges to Mini LED chip packaging. Due to the need for ultra-small space, Mini LED chips are micron-sized. However, when the chip's pad area is less than 2000 square microns, the contact area between the chip and the solder paste is small, resulting in a weak bonding force between the chip pad and the solder paste. This can cause problems such as open circuits, dimming, and flickering, seriously affecting product reliability. Summary of the Invention

[0004] The flip-chip LED chip, circuit board, and electronic device provided by the embodiments of the present invention mainly solve the technical problem that the soldering pad area of ​​the Mini LED chip is small, resulting in unreliable soldering between the chip solder pad and the circuit board, and low product yield.

[0005] In order to solve the above technical problems, an embodiment of the present invention provides a flip-chip LED chip, including a chip body and a solder pad arranged at the bottom of the chip body, the solder pad including an N-pole solder pad and a P-pole solder pad; two upwardly concave solder pad grooves are provided at the bottom of the chip body, the N-pole solder pad and the P-pole solder pad are respectively provided at the bottom of a solder pad groove, there is a gap between the side of the solder pad and the side wall of the solder pad groove, the cross-sectional area of ​​the solder pad groove gradually increases from the bottom of the groove to the groove opening, and from the bottom of the solder pad groove to the groove opening, the side wall of the solder pad groove is inclined in the direction away from the solder pad.

[0006] Optionally, a difference between a height h of the pad and a depth d of the pad groove is less than or equal to 20 um.

[0007] Optionally, h is less than or equal to d.

[0008] Optionally, the cross-sectional area of ​​the pad gradually decreases from the bottom of the pad groove to the notch away from the pad groove.

[0009] Optionally, the longitudinal section of the pad is an inverted isosceles trapezoid or rectangle.

[0010] Optionally, the friction coefficient of the bottom of the pad is greater than the friction coefficient of the chip body.

[0011] Optionally, the bottom surface and / or side surface of the pad are serrated or wavy.

[0012] An embodiment of the present invention further provides a circuit board comprising a substrate and at least one flip-chip LED chip as described above; the solder pad of the flip-chip LED chip is soldered to the chip setting area of ​​the substrate through solder paste and is electrically connected to the circuit in the substrate.

[0013] An embodiment of the present invention further provides an electronic device, comprising the above circuit board.

[0014] The beneficial effects of the present invention are:

[0015] Embodiments of the present invention provide a flip-chip LED chip, a circuit board, and an electronic device, wherein the flip-chip LED chip includes a chip body and a solder pad disposed at the bottom of the chip body. The solder pad includes an N-pole solder pad and a P-pole solder pad. Two upwardly recessed solder pad grooves are disposed at the bottom of the chip body, with the N-pole solder pad and the P-pole solder pad each disposed at the bottom of a solder pad groove. A gap exists between the side of the solder pad and the sidewall of the solder pad groove. The cross-sectional area of ​​the solder pad groove gradually increases from the groove bottom to the groove opening, and the sidewall of the solder pad groove tilts away from the solder pad from the groove bottom to the groove opening. Therefore, during the process of soldering the flip-chip LED chip to the circuit board, molten solder paste can penetrate into the gap and combine with the side of the solder pad, thereby making the solder paste and the solder pad more fully bonded, improving the reliability of the soldering between the flip-chip LED chip and the circuit board, and significantly improving the yield rate of the flip-chip LED chip. For circuit boards and electronic devices using this flip-chip LED chip, product reliability can be enhanced, product service life can be extended, and product quality can be improved.

[0016] Other features and corresponding beneficial effects of the present invention are described in the latter part of the specification, and it should be understood that at least some of the beneficial effects become obvious from the description in the specification of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic diagram of the structure of a flip-chip LED chip in the related art;

[0018] Figure 2a This is a schematic structural diagram of the first flip-chip LED chip provided in Example 1 of the present invention;

[0019] Figure 2b This is a schematic structural diagram of the second flip-chip LED chip provided in the first embodiment of the present invention;

[0020] Figure 3a This is a schematic structural diagram of the third flip-chip LED chip provided in the first embodiment of the present invention;

[0021] Figure 3b This is a schematic structural diagram of the fourth flip-chip LED chip provided in the first embodiment of the present invention;

[0022] Figure 4 This is a schematic structural diagram of the fifth flip-chip LED chip provided in the first embodiment of the present invention;

[0023] Figure 5 This is a schematic structural diagram of the sixth flip-chip LED chip provided in the first embodiment of the present invention;

[0024] Figure 6 A schematic structural diagram of the solder pad shown in the first embodiment of the present invention;

[0025] Figure 7 This is a schematic structural diagram of the seventh flip-chip LED chip provided in the first embodiment of the present invention;

[0026] Figure 8 This is a schematic structural diagram of an eighth flip-chip LED chip provided in the first embodiment of the present invention;

[0027] Figure 9 This is a schematic structural diagram of a flip-chip LED chip provided in the second embodiment of the present invention;

[0028] Figure 10 This is a structural diagram of a circuit board provided in Example 3 of the present invention. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the following is a further detailed description of the embodiments of the present invention through specific implementation methods in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0030] Example 1:

[0031] See Figure 1 , Figure 1 The figure shows a schematic diagram of a flip-chip LED chip structure in the related art: the flip-chip LED chip 10 includes a chip body 11 and a pad 12, wherein the pad 12 includes an N-pole pad and a P-pole pad, and the N-pole pad and the P-pole pad are separated by an insulating isolation tape. The chip body 11 may include a sapphire layer, an N-type current spreading layer, and a P-type current spreading layer. Figure 1 These details are not shown in the Figure 1As can be seen in the figure, the solder pad 12 is provided at the bottom of the chip body 11 in an outwardly convex manner. During the soldering process, the solder paste is mainly in contact with the bottom of the solder pad 12. However, since the size of the flip-chip LED chip 10 is very small and the size of the solder pad 12 is even smaller, the actual contact area between the solder paste and the solder pad 12 is not large, which results in an insufficiently secure bond between the two. After soldering is completed, the flip-chip LED chip 10 is very likely to fall off the circuit board. To solve this problem, this embodiment provides a new flip-chip LED chip, see Figure 2a A schematic diagram of the structure of a flip-chip LED chip is shown:

[0032] The flip-chip LED chip 20 includes a chip body 21 and a solder pad 22 disposed on the bottom of the chip body. The chip body 21 may include an N-type current spreading layer and a P-type current spreading layer, with a PN junction formed between the N-type and P-type current spreading layers. Alternatively, the chip body 21 may also include a transparent protective layer, a light-emitting layer, and the like.

[0033] same Figure 1 The pads 12 of the flip-chip LED chip 10 shown are similar, and the pads 22 also include an N-pole pad 221 and a P-pole pad 222 . The N-pole pad 221 and the P-pole pad 222 are isolated from each other by an isolation band made of insulating material.

[0034] The pad 22 is provided at the bottom of the chip body 21, for example, Figure 2a Among them, two upwardly concave solder pad grooves 210 are provided at the bottom of the chip body 21, and the N-pole solder pad 221 and the P-pole solder pad 222 are each provided at the bottom of a solder pad groove 210, and there is a gap between the side of the solder pad 22 and the side wall of the solder pad groove 210. When solder paste is used to solder the flip-chip LED chip 20 to the circuit board, the melted solder paste can not only bond with the bottom surface of the solder pad 22, but also penetrate along the gap between the side of the solder pad 22 and the side wall of the solder pad groove 210, thereby bonding with the side wall of the solder pad 22 and the side wall of the solder pad groove 210. In this way, the contact area between the solder paste and the solder pad 22 can be increased, thereby improving the closeness of the direct bonding between the solder paste and the solder pad 22 and enhancing the reliability of welding.

[0035] In some examples of this embodiment, the height h of the pad 22 is less than or equal to the depth d of the pad groove 210, so the pad 22 is located in the pad groove 210. Since the pad 22 is arranged in the upwardly concave pad groove 210, the pad 22 is basically "embedded" in the bottom of the chip body 21.

[0036] In some examples of this embodiment, the pad 22 may extend out of the pad groove 210, that is, the depth d of the pad groove 210 is less than the height h of the pad 22. Optionally, in some examples, it is sufficient to ensure that the value of hd is less than or equal to 20 μm. It is undoubtedly true that hd is less than or equal to 20 μm and h is less than or equal to d. However, in some examples, h may be slightly greater than d, as long as it does not exceed 20 μm. For example, in Figure 3a The pad 22 slightly extends out of the notch of the pad groove 210. However, in some other examples of this embodiment, the height of the pad 22 is substantially less than or equal to the depth of the pad groove 210, for example Figure 3b The depth of the pad groove 210 is equal to the height of the pad 22. Figure 2a The height of the middle pad 22 is less than the depth of the pad groove 210. It should be understood that, compared to the case where the height of the pad 22 is equal to or greater than the depth of the pad groove 210, Figure 2a During the soldering process of the flip-chip LED chip 20 shown in FIG, solder paste more easily penetrates into the gap between the side wall of the pad groove 21 and the pad 22. Therefore, the pad 22 shrinks into the pad groove 210, which helps to further improve the soldering reliability.

[0037] In some examples of flip-chip LED chips of this embodiment, the longitudinal section of the pad 22 may be rectangular, for example, Figure 4 In the flip-chip LED chip shown, therefore, the pad 22 itself can be a cuboid, a cube, a prism or a cylinder, etc. In this case, the cross-sectional shape and area of ​​the pad 22 are the same at all locations. However, in other examples of this embodiment, please continue to refer to Figure 2a The cross-section of the flip-chip LED chip shown is not exactly the same at all locations on the solder pad. Figure 2a The cross section of the pad 22 gradually decreases from top to bottom, that is, it gradually decreases from the bottom of the pad groove 210 to the bottom of the groove. Figure 2a The middle pad 22 is in the shape of an inverted trapezoid. Since the sidewalls of the pad groove 210 in the flip-chip LED chip are vertical (i.e. perpendicular to the bottom surface of the chip body 21), the gap between the pad groove 210 and the pad 22 gradually increases from top to bottom, which is also conducive to guiding the solder paste and facilitating the infiltration of the solder paste. Figure 2a In the embodiment, the longitudinal section of the pad is an inverted isosceles trapezoid, but in some other examples of this embodiment, the longitudinal section of the pad 22 may not be an inverted isosceles trapezoid, but a normal trapezoid.

[0038] In some examples of this embodiment, the sidewalls of the pad groove may not be vertical. Figure 2bAmong them, an LED chip is shown, in which the cross-sectional area of ​​the pad groove gradually increases from the bottom of the groove to the groove opening. In other words, from the bottom of the groove to the groove opening, the side wall of the pad groove is inclined away from the pad.

[0039] Although Figure 2b Here, the pad is in the shape of an inverted trapezoid, but there is no doubt that in some other examples of this embodiment, the longitudinal section of the pad can also be rectangular, and the pad 22 itself can be a cuboid, a cube, a prism or a cylinder, etc.

[0040] It is understandable that in order to improve the tightness of the bond between the solder paste and the pad, it can also be achieved by improving the friction coefficient of the pad surface. Specifically, a pad with a rough surface can be more tightly bonded to the solder paste than a pad with a smooth surface. On the one hand, this is because a large friction coefficient can increase the friction between the pad and the solder paste, and improve the tightness of the bond by enhancing the interaction between the two; on the other hand, an increase in the friction coefficient necessarily means that the pad surface is uneven. For example, if a certain position of the pad is concave, it means that the solder paste will bulge at the corresponding position, and if a certain position of the pad is convex, it means that the solder paste will be concave at the corresponding position. In this way, the solidified solder paste and the pad can "bite" or "match" each other, thereby enhancing the cutting force between the two. Therefore, in some examples of this embodiment, to ensure that the flip-chip LED chip can be more reliably soldered to the circuit board, the friction coefficient of the bottom of the pad can be set relatively high. For example, the friction coefficient of the bottom of the pad can be set to be greater than that of the current spreading layer integral with the pad. For example, the friction coefficient of the bottom of the N-pole pad is greater than that of the N-type current spreading layer, and the friction coefficient of the bottom of the P-pole pad is greater than that of the P-type current spreading layer. In some examples of this embodiment, the friction coefficient of the bottom of the pad is greater than the friction coefficients of the N-type current spreading layer and the P-type current spreading layer.

[0041] Please combine Figure 5 The schematic diagram of the structure of a flip-chip LED chip is shown: the arrangement between the solder pad 52 and the chip body 51 in the flip-chip LED chip 50 is similar to that in FIG. Figure 1 The arrangement of the flip-chip LED chip 10, however, Figure 5 Among them, the bottom of the flip-chip LED chip 50 pad is jagged or wavy. It should be understood that Figure 5 Although the bottom surface of the pad 52 is triangular sawtooth, in some other examples of this embodiment, the bottom surface of the pad 52 may also be square wave sawtooth, or even a combination of triangular sawtooth and square wave sawtooth, or a combination of sawtooth and wave. Figure 6 Of course, in some other examples of this embodiment, the saw teeth on the bottom surface of the pad can also be in other shapes, which are not listed here.

[0042] In some examples of this embodiment, the solution of increasing the friction coefficient of the pad surface can also be applied to the flip-chip LED chip provided in this embodiment, for example, Figure 7 In flip-chip LED chip 70, the bottom surface of solder pad 72 is rough, resulting in a greater friction coefficient than the corresponding current spreading layer. Therefore, for flip-chip LED chip 70, not only can the solder paste penetrate the gap between solder pad 72 and solder pad groove 710 to improve the bond between solder pad 72 and solder paste, but the serrations on the bottom surface of solder pad 72 also fit the solder paste, further increasing the cutting force between solder pad 72 and solder paste, thereby improving the reliability of flip-chip LED chip 70 soldering.

[0043] Although, in Figure 5-Figure 7 Only the friction coefficient of the bottom surface of the pad is increased. However, in some examples of this embodiment, in addition to increasing the friction coefficient of the bottom surface of the pad, the friction coefficient of the side surface of the pad can also be increased, or the increase in the friction coefficient of the bottom surface of the pad is combined with the increase in the friction coefficient of the side surface of the pad. For example, in some examples of this embodiment, Figure 8 As shown, the side surface of the pad may also be serrated, such as triangular serration, square wave serration, or a combination of triangular serration and square wave serration.

[0044] It should be understood that in this embodiment, an LED chip includes two solder pads, and the shapes of these two solder pads may not be exactly the same. For example, in some examples, the height of one solder pad is equal to the depth of the solder pad groove, and the height of the other solder pad is lower than the depth of the solder pad groove; in some examples, the surface of one solder pad is relatively rough, and the surface of the other solder pad is relatively smooth; in some examples, the surface of one solder pad is triangular serrated, and the surface of the other is square wave serrated.

[0045] The flip-chip LED chip provided by the embodiment of the present invention deploys the solder pad by setting an upwardly concave solder pad groove at the bottom of the chip body. The height of the solder pad is less than or equal to the depth of the solder pad groove, and a gap is ensured between the side of the solder pad and the side wall of the solder pad groove. Therefore, the solder pad in the flip-chip LED chip can be changed from a convex setting and the bottom of the chip body to an indented setting and the bottom of the chip body. In this way, when the solder pad is soldered to the circuit board, the solder paste can penetrate along the gap between the solder pad and the solder pad groove, thereby combining with the side of the solder pad and the side wall of the solder pad groove, thereby increasing the force between the solder pad and the solder paste, and improving the reliability of the combination of the solder pad and the circuit board.

[0046] Furthermore, the friction coefficient of the bottom and side surfaces of the solder pad in the flip-chip LED chip can be set to be relatively large. For example, the bottom surface of the solder pad or the bottom and side surfaces of the solder pad can be set to be serrated. This can increase the friction by increasing the surface area of ​​contact between the solder pad and the solder paste. At the same time, it can also make the solder pad surface and the solder paste fit together more tightly, thereby enhancing the cutting force between the two and improving the yield of electronic products containing the flip-chip LED chip.

[0047] Example 2:

[0048] In order to make the advantages and details of the flip-chip LED chip provided in the above embodiments more clear to those skilled in the art, this embodiment will provide a more detailed description of the flip-chip LED chip with reference to examples.

[0049] See Figure 9 The flip-chip LED chip 90 shown includes a chip body 91 and solder pads 92. The solder pads 92 include an N-pole solder pad 921 and a P-pole solder pad 922. The N-pole solder pad 921 is integrated with the N-type current spreading layer 911 in the chip body 91, while the P-pole solder pad 922 is integrated with the P-type current spreading layer 912 in the chip body 91.

[0050] In addition to the N-type current spreading layer 911 and the P-type current spreading layer 912, the chip body 91 may also include a transparent protective layer 913, a light-emitting layer 914, and an isolation strip 915. The N-type current spreading layer 911, the light-emitting layer 914, and the P-type current spreading layer 912 are sequentially arranged below the transparent protective layer 913 from top to bottom. The transparent protective layer 913 is used to protect the N-type current spreading layer 911, the light-emitting layer 914, and the P-type current spreading layer 912 below. Therefore, it is understood that in this embodiment, the transparent protective layer 913 is required to have a relatively high hardness. In some examples of this embodiment, the transparent protective layer 913 may be a sapphire layer.

[0051] In this embodiment, a PN junction is formed between the N-type current spreading layer 911 and the P-type current spreading layer 912. Similarly, the N-pole pad 921 and the P-pole pad 922 are isolated by an insulating tape 915. Figure 9 As can be seen in FIG, the N-type current spreading layer 911 and the P-type current spreading layer 912 , as well as the N-pole pad 921 and the P-pole pad 922 are isolated by the isolation tape 915 . Figure 9The isolation strip 915 shown in FIG. 1 is in an inverted "L" shape. Therefore, isolation strip 915 actually comprises a vertical plane and a horizontal plane. The vertical plane provides isolation between N-type current spreading layer 911 and P-type current spreading layer 912, as well as between N-pole pad 921 and P-pole pad 922. However, to prevent solder paste from connecting the two pads during soldering, isolation strip 915 also requires horizontal isolation along its horizontal plane.

[0052] When the flip-chip LED chip 90 is soldered to the circuit board and powered on, the light-emitting layer 914 can emit light under the stimulation of the electrical energy in the N-type current spreading layer 911 and the P-type current spreading layer 912. The color of the light emitted by the light-emitting layer 914 is related to the material of the current spreading layer (that is, the material of the N-pole pad 921 and the P-pole pad 922). In this embodiment, the materials of the N-type current spreading layer 911 and the P-type current spreading layer 912 are both gallium nitride. Of course, in other examples of this embodiment, the N-type current spreading layer 911 and the P-type current spreading layer 912 can also be made of other materials, such as gallium arsenide.

[0053] In this embodiment, the bottom of the chip body 91 is provided with corresponding pad grooves 910 for the N-pole pad 921 and the P-pole pad 922, respectively. Each of the two pads 92 corresponds to a pad groove 910. The pad groove 910 is recessed upward, and the pad 92 extends from the bottom of the pad groove 910 toward the notch. However, in this embodiment, the depth of the pad groove 910 is slightly greater than the height of the pad 92. Therefore, the pad 92 does not extend above the notch of the pad groove 910. In some examples of this embodiment, the sidewalls of the pad groove 910 are vertical, and there is a certain gap between the pad 92 and the sidewalls of the pad groove 910. The gap gradually increases from the bottom of the groove to the notch. In other words, the cross-section of the pad 92 gradually decreases from the bottom of the groove to the notch.

[0054] Since the solder pad 92 is embedded and retracted in the solder pad groove 910, during the soldering process of the flip-chip LED chip 90, the molten solder paste can easily penetrate along the gap between the solder pad 92 and the solder pad groove 910, thereby contacting the side of the solder pad 92, increasing the contact area between the solder pad 92, and thereby increasing the cutting force between the solder pad 92 and the solder paste.

[0055] In order to further enhance the reliability of the flip-chip LED chip 90 soldering, in this embodiment, the friction coefficient of the surface of the solder pad 92 can be set to be relatively large, for example, Figure 9Among them, the side and bottom surfaces of the pad 92 are wavy. In this way, by changing the bottom and side surfaces of the pad 92 from a smooth plane to a wavy water pattern, the contact area between the flip-chip LED chip pad 92 and the solder paste can be increased, thereby increasing the thrust of the flip-chip LED chip and ensuring the quality and reliability of the product.

[0056] Example 3:

[0057] This embodiment provides a circuit board, see Figure 10 The circuit board 100 includes a substrate 101 and at least one flip-chip LED chip 102. The structure of the flip-chip LED chip 102 can be found in the previous embodiments and will not be further described here. The substrate 101 includes circuitry, and a chip mounting area is provided on the surface of the substrate 101. The flip-chip LED chip 102 can be soldered to the chip mounting area using solder paste, thereby achieving electrical connection with the circuitry within the substrate 101.

[0058] When soldering the flip-chip LED chip 102 to the chip placement area, the melted solder paste not only bonds with the bottom surface of the flip-chip 102 pad, but also seeps into the gap between the pad and the side of the pad groove, thereby bonding with the side of the pad. This can increase the contact area between the solder paste and the flip-chip LED chip 102 pad to a certain extent, thereby improving the strength of the bond between the two.

[0059] Furthermore, since in some examples, at least one of the bottom and side surfaces of the solder pad in the flip-chip LED chip 102 is relatively rough, wavy and / or jagged, this not only increases the surface area of ​​contact between the solder pad and the solder paste, thereby increasing friction, but also allows the solder pad surface and the solder paste to fit more tightly together, thereby enhancing the cutting force between the two.

[0060] On the other hand, this embodiment also provides an electronic device, which can be an outdoor LED display or various terminals. The terminals here can include mobile terminals such as mobile phones, tablet computers, laptops, PDAs, portable media players (PMPs), navigation devices, wearable devices, smart bracelets, pedometers, etc., as well as fixed terminals such as digital TVs and desktop computers. In this embodiment, the electronic devices include Figure 10 The circuit board shown in FIG.

[0061] The circuit board and electronic device provided in this embodiment can enhance product reliability, extend product service life, and improve product quality due to the improvement of the pad structure of the flip-chip LED chip used therein.

[0062] There is no doubt that the flip-chip LED chips provided in the aforementioned embodiments can be applied to various lighting fields. For example, they can be made into backlight modules for use in the display backlight field (which can be backlight modules for terminals such as televisions, monitors, and mobile phones). In this case, they can be applied to backlight modules. In addition to being applicable to the display backlight field, they can also be applied to the key backlight field, the photography field, the home lighting field, the medical lighting field, the decoration field, the automotive field, the transportation field, and the like. When applied to the key backlight field, they can be used as key backlight light sources for mobile phones, calculators, keyboards, and other devices with key buttons; when applied to the photography field, they can be made into camera flashlights; when applied to the home lighting field, they can be made into floor lamps, table lamps, lighting lamps, ceiling lamps, downlights, projection lamps, and the like; when applied to the medical lighting field, they can be made into surgical lamps, low-electromagnetic lighting lamps, and the like; when applied to the decoration field, they can be made into various decorative lamps, such as various colored lanterns, landscape lighting lamps, and advertising lamps; when applied to the automotive field, they can be made into car lights, car indicator lights, and the like; when applied to the transportation field, they can be made into various traffic lights and various street lamps. The above applications are merely examples of applications in this embodiment. It should be understood that the application of the LED in this embodiment is not limited to the above examples.

[0063] The above content is a further detailed description of the embodiments of the present invention in conjunction with specific implementation methods, and the specific implementation of the present invention cannot be considered to be limited to these descriptions. For those skilled in the art of the present invention, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should be considered to fall within the scope of protection of the present invention.

Claims

1. A flip-chip LED chip, characterized in that: It includes a chip body and a solder pad arranged at the bottom of the chip body, the solder pad includes an N-pole solder pad and a P-pole solder pad; two upwardly concave solder pad grooves are provided at the bottom of the chip body, the N-pole solder pad and the P-pole solder pad are respectively provided at the bottom of a solder pad groove, there is a gap between the side of the solder pad and the side wall of the solder pad groove, the cross-sectional area of ​​the solder pad groove gradually increases from the bottom of the groove to the groove mouth, and the side wall of the solder pad groove is inclined in the direction away from the solder pad from the bottom of the groove to the groove mouth.

2. The flip-chip LED chip according to claim 1, wherein: The difference between the height h of the pad and the depth d of the pad groove is less than or equal to 20 μm.

3. The flip-chip LED chip according to claim 2, wherein: The h is less than or equal to the d.

4. The flip-chip LED chip according to claim 1, wherein: The cross-sectional area of ​​the pad gradually decreases from the bottom of the pad groove to the notch away from the pad groove.

5. The flip-chip LED chip according to claim 1, wherein: The longitudinal section of the pad is an inverted isosceles trapezoid or rectangle.

6. The flip-chip LED chip according to any one of claims 1 to 5, wherein: The friction coefficient of the bottom of the pad is greater than the friction coefficient of the chip body.

7. The flip-chip LED chip according to claim 6, wherein: The bottom surface and / or side surface of the pad are serrated or wavy.

8. A circuit board, characterized in that: It comprises a substrate and at least one flip-chip LED chip according to any one of claims 1 to 7; the pad of the flip-chip LED chip is soldered to the chip setting area of ​​the substrate through solder paste and is electrically connected to the circuit in the substrate.

9. An electronic device, characterized in that: Comprising the circuit board as claimed in claim 8.

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