Long-length light-emitting diode and its application device

Abstract

The present invention provides a long-length light-emitting diode and an application device thereof that offers improved reliability against thermal cycling and thermal shock. [Solution] The elongated light-emitting diode U comprises a substrate 1, a plurality of light-emitting diode chips 3a, 3b, 3c, 3d, 3e, 3f arranged in a linear fashion, a plurality of electrical connection leads 2 connected to the electrodes of the light-emitting diode chips, and a packaging encapsulant 4 that covers the plurality of light-emitting diode chips and includes a narrow lateral groove 5 between two predetermined adjacent light-emitting diode chips.

Description

[Technical Field]

[0001] The present invention relates to an elongated light-emitting diode and an application apparatus thereof, and in particular to an elongated light-emitting diode in which a package encapsulant includes a narrow lateral transverse groove, thereby improving the reliability of the elongated light-emitting diode against thermal cycles and thermal shocks. [Background Art]

[0002] Light-emitting diodes (abbreviated as LEDs) have characteristics such as high brightness, energy saving, polychromatism and high-speed response, and have already been used in various lighting fields requiring light sources, such as the field of automotive vehicle lights. Commercially available LEDs are mostly packaged in a single chip, so they look like a point light source when lit. Conventional LED vehicle lights are characterized by multiple point light sources to distinguish them from incandescent bulbs.

[0003] Each of the Japanese patents (JPA JP 2012-59736, JPA JP 2016-167518) describes a design in which multiple LED chips are arranged in a row and potted into a long LED strip or LED tube for use in indoor lighting. Multiple LED chips are also arranged in a row and potted into a long LED spider light for use in outdoor decorative lamps. While the long LEDs potted with multiple LED chips described above have low reliability against thermal cycling and thermal shock, the operating environment is often indoors at room temperature or outdoors in the range of -30°C to 50°C, so it is not a harsh environment with large temperature fluctuations, and it is thought that the LEDs will not fail with short-term application. In contrast, the environment in which LEDs are applied to exterior lamps of automobiles is extremely harsh. For this reason, the automotive industry has particularly strict requirements for the quality and reliability of LEDs, such as the well-known AEC-Q102 test specification and the USCAR 33 test specification. Furthermore, the thermal shock test in USCAR 33 requires LEDs to undergo 1500 cycles of thermal shock testing from low to high temperatures, with a test temperature range of -55°C to 150°C, which is far more stringent than the operating environment of the outdoor LED decorative lights mentioned above. Therefore, commercially available LEDs cannot meet the stringent specifications required for automobiles. One reason for this is that the encapsulating material (colloidal material) used to encapsulate ordinary light-emitting diodes (LEDs) is mainly epoxy resin. However, epoxy resin is a thermosetting resin that becomes solid after encapsulation and has relatively high hardness and bulk modulus (approximately 1-3 Gpa). The linear thermal expansion coefficient (CLTE) of epoxy resin is approximately 20-40 ppm / °C below the glass transition temperature (Tg), but it increases sharply by 3-4 times above the glass transition temperature (Tg), which is much larger than the linear thermal expansion coefficient of gold wire (approximately 14 ppm / °C).When the operating temperature of an LED exceeds the Tg temperature of its encapsulant, the difference in linear thermal expansion coefficients between the encapsulant and the gold wire increases rapidly. This causes a sharp increase in thermal stress on the gold wire inside the LED, leading to the gold wire breaking due to thermal stress, causing the LED to fail and not pass automotive specification tests. Therefore, automotive LEDs generally use encapsulants with a high Tg temperature to improve the reliability of LED performance at high temperatures, and the difference in linear thermal expansion coefficients between the encapsulant and the gold wire is minimized as much as possible.

[0004] Furthermore, in order to develop a linear LED vehicle light that is uniform and free of granular bright spots, the thin linear LED light-emitting device described in Patent Document TWI708908 provides the structure and manufacturing technology of a thin linear LED light-emitting device. It uses an LED Bar (also called an LED bar) in which multiple identical LED chips (plurality LED chips) are packaged as a light source, and since the LED Bar is a linear light source that emits light continuously and visually uniformly, it is particularly suitable for high-quality linear vehicle lights, unlike conventional designs that use granular LED packages as light sources. By applying this thin linear LED light-emitting device to linear lamps designed using a thin light guide plate, especially to vehicle lights, it is possible to solve various problems that have occurred with conventional LED linear vehicle lights, such as visually discontinuous light emission, uneven brightness, and visible granular bright spots.

[0005] However, in long-length light-emitting diodes (LEDs) containing multiple chips, when electrodes are connected to the internal LED chips by gold wire bonding, the difference in the coefficient of linear thermal expansion (CLTE) between the gold wire and the packaging encapsulant is large. As the temperature changes, the thermal stress on the gold wire due to pressure or tension from the encapsulant repeatedly changes with the temperature, causing thermal fatigue to occur between the gold wire and the gold wire welding point. Basically, the magnitude of this thermal stress is proportional to the stiffness or bulk modulus of the encapsulant and the range of temperature change. Furthermore, as the length of the encapsulant of the LED increases, the thermal stress on the gold wire and the gold wire welding point that is further away from the center of the encapsulant within the LED also increases. In other words, in long-length LEDs, the number of chips increases and the length increases, so when the temperature changes significantly, the deformation and thermal stress on the internal gold wire also increase. The magnitude of this thermal stress is closely related to the material and length of the encapsulant used in the light-emitting diode, which will be explained in detail below.

[0006] In recent years, silica gel has been used to encapsulate light-emitting diodes (LEDs) to meet automotive specifications. There are mainly two types of silica gel: methyl-based silica gel and phenyl-based silica gel. Methyl silica gel has a low Tg temperature (below -50°C) and maintains a relatively low bulk modulus in the automotive operating environment (-50°C to 150°C). It is generally called soft silica gel, but taking Dow-Corning's OE-6351 as an example, its bulk modulus is less than 0.01 Gpa even at -50°C to 150°C. When the temperature changes, the thermal stress on the gold wire within the LED due to the methyl silica gel also decreases accordingly. At -50°C to 150°C, the linear thermal expansion coefficient (CLTE) of Dow-Corning OE-6351 is approximately 290 ppm / °C, which is 20 times that of the gold wire. Phenyl-based silica gel has a relatively high refractive index (1.5-1.6) and is mainly used for encapsulating high-brightness and high-power light-emitting diodes.

[0007] However, the Tg temperature of phenyl-based silica gel is relatively high, and as an example, the Tg of many types of Dow-Corning phenyl silica gel is mostly in the range of -10°C to 50°C. At room temperature, it is usually harder than methyl silica gel and is generally called hard silica gel. The bulk modulus of these phenyl silica gels varies greatly depending on the operating environment required for automobiles (-50°C to 150°C). For example, Dow-Corning's OE-7662 has a bulk modulus of 1 GPa at -50°C, which is 100 times that of Dow-Corning methyl silica gel OE-6351, but it decreases rapidly near the Tg point, falling below 3.0 MPa above 50°C. When the temperature changes in the range of 0 to -50°C, the thermal stress on the gold wire in the light-emitting diode due to phenyl silica gel also becomes relatively high. The linear thermal expansion coefficient (CLTE) of phenyl silica gel also changes significantly depending on the temperature of the Tg point. Taking Dow-Corning OE-7662 as an example, its linear thermal expansion coefficient (CLTE) is approximately 81 ppm / °C at 0 to -50°C, which is about one-third that of methyl silica gel OE-6351. At 50 to 150°C, it rises to 181 ppm / °C, which is close to that of methyl silica gel OE-6351, but in both cases it is much larger than the 14 ppm / °C of the gold wire.

[0008] Within the range of elastic deformation, the deformation (strain) of a material has a linear relationship with stress, i.e., stress = elastic modulus (or stiffness modulus) × strain. The stiffness modulus of resin-based materials is almost always expressed by the bulk modulus (also called the bulk elastic modulus), i.e., pressure = bulk modulus × volumetric deformation rate. In other words, the higher the bulk modulus of the encapsulating material, the greater the stress generated for the same amount of deformation. Regarding the characteristics of the encapsulating material commonly used for encapsulating the above-mentioned light-emitting diodes, the bulk modulus of epoxy resin is about 1 GPa at -50°C to 150°C, so the thermal stress on the gold wire is the greatest, which is the main reason why conventional light-emitting diodes encapsulated in epoxy resin do not meet the automotive specifications mentioned above. The bulk modulus of phenyl silica gel is about 1 GPa even at -50°C to the Tg point. In this low-temperature range, the bulk modulus of methyl silica gel is relatively low, at only about 0.01 GPa. Therefore, when the difference in thermal deformation is small, the thermal stress on the gold wire inside the light-emitting diode due to phenyl silica gel is much greater than that of methyl silica gel.

[0009] Most materials expand and contract with heat, and the encapsulant and gold wire inside a light-emitting diode (LED) are no exception. When the temperature decreases, the linear thermal expansion coefficient of the encapsulant is greater than that of the gold wire, so the gold wire deforms due to the pressure caused by the contraction of the encapsulant. Conversely, when the temperature increases, the linear thermal expansion coefficient of the encapsulant is greater than that of the gold wire, so the gold wire deforms as it is pulled in the opposite direction by the large expansion of the encapsulant. In other words, as the temperature changes up and down, the gold wire inside the LED is repeatedly deformed by thermal stress from different directions, resulting in various forms of thermal fatigue. If the number of such cycles of temperature changes continues to increase, the gold wire inside the LED will break due to the fatigue failure mechanism. The conventional fatigue life of gold wire (i.e., the number of fatigue cycles until breakage) decreases as the fatigue stress increases. In other words, the greater the thermal stress of thermal fatigue, the fewer times the gold wire can withstand thermal fatigue. When testing light-emitting diodes in automotive applications, under the same temperature cycle or thermal shock test, the greater the thermal stress generated by the encapsulant, the faster the gold wire will break.

[0010] Furthermore, when the temperature changes, the thermal stress on each gold wire in a typical long-length light-emitting diode (LED) varies depending on its location. The amount of thermal deformation of the LED encapsulant increases linearly from the center to the outer edge of the encapsulant; therefore, the further away from the center of the encapsulant, the greater the thermal stress and deformation on the gold wire. Consequently, as the length of the LED encapsulant increases, the thermal stress on the gold wires closer to the outer edge of the encapsulant also increases.

[0011] As a practical example, when encapsulating a light-emitting diode (LED) approximately 5mm long containing four chips using a wire bonding process with phenyl silica gel encapsulating material such as Shin-Etsu's LPS-3435, KER-2460, or Dow-Corning's OE-6631, OE-6636, a thermal shock test based on the aforementioned automotive specification USCAR 33 showed that the thermal stress from the encapsulating material was too great, causing some of the gold wires in the LED to break, ultimately resulting in most of the LEDs failing. Further analysis revealed that in the failure mode of all failed LEDs, the gold wire closest to the edge of the packaging encapsulating material broke, and the break occurred near the first welding point, which is the soldering point near the top surface of the LED chip. This supports the finding that the thermal stress and deformation on the gold wires are greater the further they are from the center of the encapsulating material. To solve the above problems, this invention innovatively designs the structure of the light-emitting diode encapsulant, allowing a long light-emitting diode containing multiple chips to pass the tests required for automotive specifications and be applied to vehicle lights on the exterior of automobiles, even when encapsulated using a high-hardness encapsulant such as phenyl silica gel as the encapsulant by a gold wire bonding process. [Overview of the project] [Problems that the invention aims to solve]

[0012] The technical problem that this invention aims to solve is to reduce the thermal stress on the gold wires within the light-emitting diode (LED), even when encapsulating a long LED containing multiple chips using a wire bonding process with a high-hardness encapsulating material such as phenyl silica gel, through an innovative encapsulation configuration and encapsulating material design, thereby improving its reliability against thermal cycling and thermal shock, and enabling it to pass the USCAR 33 specification thermal shock test for automobiles. Another feature of this invention is that, in addition to this configuration, it maintains the uniformity of linear light emission, and the special configuration of the encapsulating material prevents the occurrence of bright spots and dark areas, thus not causing any problems in assembly or light distribution design when assembled and used in a thin wire-type light-emitting device. [Means for solving the problem]

[0013] The elongated light-emitting diode according to the present invention is applicable to the thin-wire LED light-emitting device described in Patent Document TWI708908, and provides a linear light-emitting diode light-emitting device applicable to vehicle lights of automobiles. The elongated light-emitting diode according to the present invention comprises a substrate, a plurality of electrical connection leads (e.g., gold wire, aluminum wire, or copper wire), a plurality of identical light-emitting diode chips, and a packaging encapsulant. A plurality of conductive pads are provided on the substrate, and the plurality of light-emitting diode chips are arranged linearly at an appropriate pitch, and each light-emitting diode chip is fixed to the corresponding conductive pad by a die bonding process. Depending on the characteristics of the light-emitting diode chips and the requirements for electrical connection, a wire bonding process is performed to connect one end of a wire to one light-emitting diode chip and the other end to a conductive pad next to the chip. In the encapsulation process, a packaging encapsulant is placed on the substrate so as to cover each of the light-emitting diode chips, each of the electrical connection leads, and each of the conductive pads on the substrate, the special feature being that the packaging encapsulant includes a narrow lateral groove between two predetermined adjacent light-emitting diode chips.

[0014] The elongated light-emitting diode according to this invention has at least one narrow lateral groove in the packaging encapsulant, which shortens the equivalent length of encapsulant covering the electrical connection leads inside the light-emitting diode. This effectively reduces the thermal stress on the electrical connection leads (e.g., gold wires) caused by the encapsulant, and further reduces the risk of fracture of the electrical connection leads due to thermal fatigue. To effectively reduce the thermal stress on the electrical connection leads (e.g., gold wires) caused by the encapsulant, the depth of the groove should be at least half the height of the encapsulating encapsulant. At the same time, to ensure that the encapsulating encapsulant effectively covers the light-emitting diode chip, the electrical connection leads, and the conductive pads of the substrate, the distance between the edge of the groove and the light-emitting diode chip, the electrical connection leads, and the conductive pads of the substrate should be at least 0.1 mm.

[0015] The features and technical content of this invention will be better understood by referring to the detailed description and drawings below, however, the drawings provided are for reference and illustrative purposes only and are not intended to limit this invention. [Brief explanation of the drawing]

[0016] [Figure 1] This is a schematic perspective view showing a long light-emitting diode of the first embodiment of the present invention. [Figure 2] This is a schematic side view showing a long light-emitting diode of the first embodiment of the present invention. [Figure 3] This is a schematic perspective view showing a long light-emitting diode of a second embodiment of the present invention. [Figure 4] This is a schematic side view showing a long light-emitting diode according to a second embodiment of the present invention. [Figure 5] This is a schematic perspective view showing how multiple elongated light-emitting diodes of the present invention are applied to an elongated light-emitting diode light-emitting device. [Modes for carrying out the invention]

[0017] The following describes embodiments of the "long-length light-emitting diode and its application apparatus" disclosed herein by specific examples, but those skilled in the art will be able to grasp the advantages and effects of the present invention from the content disclosed herein. The present invention may be implemented and applied by other different specific embodiments, and the details herein can be modified and changed in various ways based on different views and uses, without departing from the spirit of the present invention. It should be noted that the drawings of the present invention are for illustrative purposes only and are not drawn to actual dimensions. The following embodiments will describe the technical content relating to the present invention in more detail, but the disclosure is not intended to limit the scope of protection of the present invention. In this specification, various elements are represented by terms such as "first," "second," and "third," but it should be understood that these elements are not limited to these terms. These terms are mainly used to distinguish one element from another. The term "or" as used herein means that, depending on the actual situation, it includes any one or more combinations of the relevant items listed.

[0018] Referring to Figures 1 and 2, Figure 1 is a schematic perspective view showing an elongated light-emitting diode (U) according to an embodiment of the present invention, and Figure 2 is a schematic side view showing an elongated light-emitting diode (U) according to an embodiment of the present invention. In Figure 1, the elongated light-emitting diode (U) comprises a substrate (1), 12 electrical connection leads (2), 6 light-emitting diode chips (3a, 3b, 3c, 3d, 3e, 3f), and a packaging encapsulant (4). The packaging encapsulant (4) has a lateral groove (5), that is, the direction of this lateral groove is perpendicular to the arrangement direction of these 6 light-emitting diode chips (3a, 3b, 3c, 3d, 3e, 3f). These six light-emitting diode chips (3a, 3b, 3c, 3d, 3e, 3f) are all horizontal type, and since their positive electrode (P) and negative electrode (N) are located on the top surface of the chip, each light-emitting diode chip requires two independent electrical connection leads (2). The substrate (1) has six conductive pads (11, including 11a, 11b, 11c, 11d, 11e, 11f) corresponding to the six light-emitting diode chips (3a, 3b, 3c, 3d, 3e, 3f) and one conductive pad (12) on which no light-emitting diode chip is mounted. Also, since the conductive pad (12) does not require a light-emitting diode chip, its area is smaller than that of the conductive pads (11). Six light-emitting diode chips (3a, 3b, 3c, 3d, 3e, 3f) are fixed to corresponding conductive pads (11) with die bonding paste (6) in a die bonding process so that they are arranged linearly (or in a straight line) at equal intervals. In a wire bonding process, one end of each electrical connection lead (2) is connected to one light-emitting diode chip, and the other end is connected to an adjacent conductive pad (11) or conductive pad (12). In this embodiment, gold wire with a diameter of 1.2 mil is used for the electrical connection leads (2). In an encapsulation process, a package encapsulant (4) is provided on the upper surface of the substrate (1) so as to cover each of the light-emitting diode chips, each of the electrical connection leads (2), and each of the conductive pads (11, 12) on the substrate (1).As shown in Figure 2, the packaging encapsulant (4) in this embodiment covers only the upper surface of the substrate (1), and the height (T) of the encapsulant is approximately 1.7 mm. One of the features of this invention is that the packaging encapsulant (4) includes a lateral groove (5) between two predetermined adjacent light-emitting diode chips. In this embodiment, the lateral groove (5) in the packaging encapsulant (4) is provided between the third light-emitting diode chip (3c) and the fourth light-emitting diode chip (3d), and the direction of the lateral groove (5) is perpendicular to the arrangement direction of the six light-emitting diode chips.

[0019] In this embodiment, the lateral groove (5) is formed in the encapsulation preform (not shown) of the light-emitting diode by cutting the encapsulation preform with a diamond cutter. Therefore, in Figure 2, the width (W) of the lateral groove (5) is determined by the thickness of the diamond cutter used. Basically, the width (W) of the lateral groove (5) should not be too large in order to avoid affecting the shape of the light of the light-emitting diode or causing visual variations. For this reason, limited by the thickness of the diamond cutter, the width (W) of the lateral groove (5) in this invention is preferably 0.1-0.3 mm. In Figure 2, the depth of the lateral groove (5) is determined by the height (H) of the bottom of the lateral groove. The height (H) of the bottom of the lateral groove is determined by the depth of the groove cut by the diamond cutter, which must be greater than at least half the height (T) of the package sealant (1.7 mm) in order to effectively reduce the thermal stress of the sealant on the electrical connection leads (e.g., gold wires). This ensures that the height (H) of the bottom of the groove is between 0.1 mm and half the height of the package sealant (i.e., 0.8 mm), so that the package sealant effectively covers the conductive pads of the substrate. In this embodiment, the height (H) of the bottom of the groove is controlled to be between 0.1 mm and the height of the top surface of the light-emitting diode chips (3c, 3d), which more effectively reduces the thermal stress of the sealant on the electrical connection leads (e.g., gold wires). In this embodiment, the height of the light-emitting diode chips (3c, 3d) is 0.3 mm. Therefore, in a preferred embodiment of the present invention, the height (H) of the bottom of the lateral groove is controlled to 0.1 mm to 0.3 mm so that the encapsulant completely covers each of the light-emitting diode chips and each of the conductive pads on the substrate, and the thermal stress caused by the encapsulant on the electrical connection leads can be effectively reduced.

[0020] How to select two adjacent light-emitting diode (LED) chips to install lateral grooves (5), or how many lateral grooves (5) to install, is related to the total length of the package encapsulant, the tensile strength of the package encapsulant and the electrical connection leads (2), and the temperature range of the thermal cycling (or thermal shock). In short, the more lateral grooves there are in the LED encapsulant, the less thermal stress is placed on the electrical connection leads inside the LED, and the higher the reliability against thermal cycling and thermal shock. Relatively speaking, the more lateral grooves there are in the LED encapsulant, the more difficult and costly the manufacturing process becomes.

[0021] Next, the effects of the present invention will be explained. In this embodiment, the elongated light-emitting diode is configured such that the packaging encapsulant has a lateral groove whose depth is close to the surface of the light-emitting diode. The effect of this is to divide the original encapsulant into two packaging encapsulants of half the length, that is, to form the centers of two independent new encapsulants. This corresponds to halving the distance of the gold wire at the far right edge of the light-emitting diode from the center of the encapsulant covering it on the right side. When the effective length of thermal stress caused by the encapsulant covering the gold wire is shortened, the thermal stress on the gold wire due to the encapsulant is relatively reduced, thus reducing the risk of the gold wire breaking due to thermal fatigue, and improving the lifespan and reliability of the light-emitting diode in withstanding thermal cycling and thermal pressing. As described above, the present invention is not limited to the material and form of the substrate (1). For example, the substrate (1) is a two-layer substrate with conductive layers on both the upper and lower layers (front and back surfaces), but it may also be a BT (Bismaleimide Triazine) board, a ceramic substrate, or a composite substrate in which separated metal blocks are embedded in resin. Alternatively, the substrate (1) may be a BT board or ceramic substrate containing two or more conductive layers to improve the flexibility of circuit wiring design. Note that the present invention is not limited to the shape of the conductive pads (11) and (12).

[0022] The present invention is applied to light emitting diode chips in different embodiments, including vertical light emitting diode chips (the positive electrode (P) and negative electrode (N) of an LED chip are separated on different surfaces of the LED chip, that is, the front surface and the bottom surface), horizontal light emitting diode chips (both the positive electrode (P) and negative electrode (N) of an LED chip are located on the surface or top surface of the LED chip), and the like. Among them, both vertical light emitting diode chips and horizontal light emitting diode chips need to be encapsulated through die bonding and wire bonding processes, so there is the aforementioned problem that the gold wires are broken due to thermal fatigue.

[0023] Figures 3 and 4 show a second embodiment of the present invention, wherein the illustrated light emitting diode chip is a vertical light emitting diode chip. In the vertical light emitting diode chip, one electrode (for example, the positive electrode (P)) is located on the top surface of the chip, and the other electrode (for example, the negative electrode (N)) is located on the bottom surface of the chip. In this embodiment, the light emitting diode chips (3a, 3b, 3c, 3d, 3e, 3f) are first fixed to corresponding conductive pads (11, including 11a, 11b, 11c, 11d, 11e, 11f) by conductive die bonding paste (6) (for example, silver paste), and then each is connected to the electrode (P) on the top surface of the corresponding light emitting diode chip and another adjacent conductive pad (11) or conductive pad (12) through the electrical connection leads (2) by a wire bonding process. In this embodiment, the light emitting diode chip (3a) is connected to the corresponding conductive pad (11a), and the electrical connection lead (2) connected to the electrode (P) on the surface of the light emitting diode chip (3a) is bonded to the conductive pad (11b). In this arrangement, only the electrical connection lead (2) connected to the electrode (P) on the surface of the light emitting diode chip (3f) is bonded to the conductive pad (12).

[0024] In this embodiment, the packaging encapsulant (4) includes two lateral grooves (51, 52), wherein a first lateral groove (51) is provided between the second light-emitting diode chip (3b) and the third light-emitting diode chip (3c), a second lateral groove (52) is provided between the fourth light-emitting diode chip (3d) and the fifth light-emitting diode chip (3e), and the direction of these lateral grooves (51, 52) is perpendicular to the arrangement direction of the six light-emitting diode chips (3a, 3b, 3c, 3d, 3e, 3f). As described above, since the number of lateral grooves in the encapsulant of the light-emitting diode in this embodiment is increased, the reliability against thermal cycles and thermal shocks is also improved.

[0025] The elongated light-emitting diode of the present invention has at least one narrow lateral groove in the packaging encapsulant, which shortens the effective length of thermal stress induced by the encapsulant on the electrical connection leads, effectively reduces the thermal stress induced by the encapsulant on the wires, and further reduces the risk of wire breakage due to thermal fatigue.

[0026] It should be further noted that in the present invention, the direction of wire bonding on the electrical connection leads of the light-emitting diode is not limited. However, in order to avoid affecting the formation of the lateral grooves in the encapsulant and preventing the encapsulant from being unable to cover all the electrical connection leads, it is preferable that the wire bonding direction of the electrical connection leads on both sides of each lateral groove in the encapsulant is parallel to the direction of the lateral groove as much as possible.

[0027] It should be noted that the number of light-emitting diode (LED) chips is not limited in this invention. Nor is the number of lateral grooves in the LED encapsulant. When forming lateral grooves in the LED encapsulant of this invention, it is not limited to forming them by cutting the encapsulation preform with a diamond cutter. For example, the encapsulant may be coated by a molding process such as direct molding, transfer molding, or injection molding, and lateral grooves may be formed in the encapsulant at the same time. However, when forming lateral grooves in the encapsulant by a molding process, a draft angle is required in the lateral grooves of the encapsulant depending on the demolding conditions, and the width of the lateral grooves also needs to be relatively wide. In other words, it is desirable that the LED chips be installed at a large pitch and that the number of lateral grooves that can be installed in the encapsulant be relatively small.

[0028] In one actual sample functional test of this invention, the resin used to encapsulate the light-emitting diodes (LEDs) was Dow Corning's phenyl silica gel. Two different types of LEDs, identical in length and internal LED chip, were subjected to a thermal shock test using USCAR 33 automotive LEDs. One type had lateral grooves in the encapsulating material, while the other did not. The test conditions were thermal shock from a low temperature of -55°C to a high temperature of 150°C, and the test duration was 1512 hours (equivalent to 3000 cycles). After 1344 hours of testing, the failure rate for the LED samples without lateral grooves in the encapsulating material was 80 / 80, meaning all 80 test samples were defective. However, after 1512 hours of testing, the failure rate for the LED samples with lateral grooves in the encapsulating material was 0 / 80, meaning there were no defects. The test results fully confirmed the specific effectiveness and inventiveness of this invention.

[0029] Figure 5 is a schematic perspective view showing how the elongated light-emitting diode of the present invention is applied to an elongated light-emitting diode light-emitting device (Z). In this embodiment, the elongated light-emitting diode light-emitting device (Z) comprises a printed circuit board (P), a plurality of elongated light-emitting diodes (U) of the present invention, and at least one electrical connector (C). The elongated light-emitting diodes (U) and the electrical connector (C) are installed on the printed circuit board (P) by a SMT process to form the elongated light-emitting diode light-emitting device (Z). The present invention is not limited in the number of elongated light-emitting diodes (U).

[0030] The foregoing disclosures are merely preferred and implementable embodiments of the present invention and do not limit the scope of the claims for utility model registration of the present invention. Therefore, any equivalent technical modifications as described in the specification and drawings of the present invention are included within the scope of the claims for utility model registration of the present invention. [Explanation of Symbols]

[0031] Z: Long-length light-emitting diode light-emitting device U: Long-length light-emitting diode W: Width of the horizontal groove H: Height of the bottom of the horizontal groove P: Printed circuit board C: Electrical connector 1: Circuit board 11, 11a, 11b, 11c, 11d, 11e, 11f: Conductive pads 12: Conductive pads 2: Leads for electrical connections 3a, 3b, 3c, 3d, 3e, 3f: Light-emitting diode chips 4: Packaging sealant 5: Yokomizo 51: Yokomizo's First 52: The Second Yokomizo 501: Bottom of the horizontal groove 6: Die bonding paste

Claims

1. A substrate including multiple conductive pads, A plurality of light-emitting diode chips are provided on the corresponding conductive pads of the substrate so as to be arranged in a linear fashion, Multiple electrical connection leads, each having one end connected to one of the light-emitting diode chips and the other end connected to an adjacent conductive pad, A packaging encapsulant is provided on the substrate so as to cover each of the light-emitting diode chips, each of the electrical connection leads, and each of the conductive pads on the substrate, and includes a transverse groove between two adjacent light-emitting diode chips, the direction of the transverse groove being substantially perpendicular to the arrangement direction of the plurality of light-emitting diode chips, and the height of the bottom of the transverse groove being 0.1 mm to half the height of the packaging encapsulant, A long-length light-emitting diode equipped with the following features.

2. The elongated light-emitting diode according to claim 1, wherein the width of the transverse groove is 0.1 mm to 0.3 mm.

3. The elongated light-emitting diode according to claim 1, wherein the height of the bottom of the aforementioned horizontal groove is 0.1 mm to 0.3 mm.

4. A substrate including multiple conductive pads, Six vertical light-emitting diode chips are provided on the corresponding conductive pads so as to be arranged linearly at equal intervals, Six electrical connection leads, each having one end connected to one of the light-emitting diode chips and the other end connected to an adjacent conductive pad, A packaging encapsulant is provided on the substrate so as to cover each of the light-emitting diode chips, each of the electrical connection leads, and each of the conductive pads on the substrate, Equipped with, The packaging encapsulant includes a first transverse groove between the second light-emitting diode chip and the third light-emitting diode chip, the direction of which the first transverse groove is perpendicular to the arrangement direction of the six light-emitting diode chips, and the packaging encapsulant includes a second transverse groove between the fourth light-emitting diode chip and the fifth light-emitting diode chip, the direction of which the second transverse groove is perpendicular to the arrangement direction of the six light-emitting diode chips, and the height of the bottom of the first transverse groove and the second transverse groove is 0.1 mm to half the height of the packaging encapsulant.

5. A long-length light-emitting diode light-emitting device having a printed circuit board including at least one electrical connector and a plurality of long-length light-emitting diodes, Each of the aforementioned elongated light-emitting diodes is A substrate including multiple conductive pads, Multiple light-emitting diode chips are provided on the corresponding conductive pads so as to be arranged in a linear fashion, Multiple electrical connection leads, one end of which is connected to one of the light-emitting diode chips and the other end of which is connected to an adjacent conductive pad, A packaging encapsulant is provided on the substrate so as to cover each of the light-emitting diode chips, each of the electrical connection leads, and each of the conductive pads on the substrate, Equipped with, The packaging encapsulant includes a transverse groove between two adjacent light-emitting diode chips, the direction of the transverse groove is substantially perpendicular to the arrangement direction of the plurality of light-emitting diode chips, and the height of the bottom of the transverse groove is 0.1 mm to half the height of the packaging encapsulant, in a long-length light-emitting diode light-emitting device.

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