Ultrathin ncsp light source and method of making same

Abstract

The application discloses an ultrathin NCSP light source and a preparation method thereof. The method comprises the following steps: performing selective etching on a metal substrate, performing front half-etching to form a recessed area at a preset die bonding position, and performing etching perforation to form a through hole in a non-front half-etching area; after electroplating a metal layer on the surface of the etched metal substrate, the metal layer and EMC material are put into a mold for injection molding, the EMC material fills the mold cavity and the through hole and is solidified to form an EMC support, and a reflection cup structure is formed around the recessed position; tin paste is applied to the pad position by using a dispensing head needle transfer method, an LED chip is fixed on the tin paste and is solidified, fluorescent glue is arranged around the LED chip and on the upper surface and is solidified, and the NCSP light source is obtained by cutting. The application takes into account the overall mechanical strength and local thinning demand of the support, enhances the heterogeneous interface bonding force, ensures the light efficiency of the chip side and the die bonding reliability of the non-planar support, and realizes the effective thinning of the overall thickness of the light source.

Description

Technical Field

[0001] This application belongs to the field of NCSP technology, specifically relating to an ultrathin NCSP light source and its preparation method. Background Technology

[0002] Currently, NCSP light sources on the market are mainly divided into two categories: substrate-free structures and substrate-based structures. Substrate-free NCSP light sources eliminate the need for a support or substrate, directly covering the surface and surrounding area of ​​the flip chip with phosphor. The overall thickness consists only of the chip thickness and the phosphor thickness, offering a significant advantage in thickness reduction. However, this type of structure lacks the effective protection of the exposed chip electrodes from the substrate. During subsequent surface mounting, module assembly, and long-term service, the chip electrodes are directly exposed to external stress and the environment, posing a high risk of electrode damage and reliability issues.

[0003] Substrate-based NCSP light sources utilize ceramic substrates, EMC (epoxy molding compound) supports, or BT substrates as carriers to provide mechanical protection and electrical interconnection for the chip electrodes, significantly improving packaging reliability. However, limited by the processing capabilities of substrate materials and the minimum thickness threshold required to maintain their mechanical strength, the overall thickness of substrate-based NCSP light sources is difficult to reduce effectively. Adding chip thickness and phosphor layer thickness on top of this, the total thickness of the packaged product often fails to meet the stringent requirements for light source thickness in ultra-thin backlight modules.

[0004] Furthermore, simply thinning the substrate in the chip placement area to reduce the overall thickness of the light source presents a series of technical obstacles: First, localized thinning leads to a decrease in the overall mechanical strength of the support structure, making it prone to warping or breakage during process flow and packaging, thus failing to meet workability requirements; second, the heterogeneous material bonding surface formed by the thinned and non-thinned areas lacks an effective mechanical interlocking structure, making it highly susceptible to interlayer peeling or delamination under environmental stresses such as thermal shock; third, when the chip is recessed into the locally thinned area, the side light emission from the chip is often blocked by the surrounding area, resulting in a significant decrease in the light extraction efficiency and brightness of the light source; finally, for support structures with non-planar features such as recesses, traditional solder paste printing processes are limited by the planar requirements of stencil operations, making it difficult to achieve precise solder paste application and reliable die bonding on the pads at the bottom of the recess, further restricting the fabrication and industrialization of ultra-thin NCSP light sources. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the existing technology in the difficulty of preparing thinner NCSP light sources, thereby providing an ultrathin NCSP light source and its preparation method.

[0006] A method for fabricating an ultrathin NCSP light source, comprising: Selective etching is performed on the metal substrate. A recessed area is formed by front-side half etching at a preset die-bonding position, and through-hole processing is performed in the non-cutting area and the non-front-side half-etched area to form a through hole. Electroplating a metal layer onto the etched metal substrate surface; The electroplated metal substrate and EMC material are placed together in a mold for injection molding, so that the EMC material melts, flows and fills the mold cavity and through holes and solidifies to form an EMC support, and a reflective cup structure is formed around the recessed area. Solder paste is applied to the pads of the EMC bracket using a dispensing needle transfer method, and the LED chip is fixed on the solder paste and cured. Phosphor adhesive is applied around and on the top surface of the LED chip and then cured. NCSP light source is obtained by cutting.

[0007] Furthermore, the remaining thickness of the metal substrate after the front half-etching process is 50-100μm, and the initial thickness of the metal substrate is 100-200μm.

[0008] Furthermore, in the electroplating step, a nickel layer is first electroplated on the surface of the metal substrate, followed by a silver layer, wherein the thickness of the nickel plating layer is ≥0.5μm and the thickness of the silver plating layer is ≥0.5μm.

[0009] Furthermore, in the injection-molded EMC support, the EMC material forms an inclined structure of a reflective cup at the edge of the recessed area, and forms a welding platform on the exposed metal surface in the middle of the recessed area.

[0010] Furthermore, in the step of applying solder paste, a low-viscosity solder paste is prepared by selecting one of the solder powders with particle sizes of T6 and T7. The solder paste is picked up from the glue tray by the dispensing head and applied to the pad position. The thickness of the cured solder paste layer is 10-20μm.

[0011] Furthermore, in the step of setting the fluorescent adhesive, the fluorescent powder is mixed with transparent silicone to remove bubbles and then applied to the frosted release film. It is then vacuum heated, molded, and cured. The curing temperature is 80℃-150℃ and the curing time is 180 seconds-900 seconds. After cutting, the NCSP light source is dehumidified. After descaling, the mold is cast with the back electrode facing up for photoelectric parameter testing. The fluorescent adhesive is then transferred again with the fluorescent adhesive side facing up and sorted, taped, and packaged.

[0012] An ultrathin NCSP light source includes a metal substrate, an EMC material, an LED chip, solder paste, and phosphor. The metal substrate has a recessed area formed by half-etching on the front side at a predetermined die-bonding position, and through-holes are formed in the non-recessed area. The EMC material is injection molded onto the metal substrate and fills the through-holes. The EMC material forms a reflective cup structure around the recessed area. The LED chip is disposed on the exposed metal pads in the recessed area via the solder paste. The phosphor covers the periphery and top surface of the LED chip.

[0013] Furthermore, the metal substrate includes a positive electrode substrate and a negative electrode substrate, which are respectively provided with the recessed area and the etched through hole; the positive electrode substrate and the negative electrode substrate are separated by the EMC material; the positive electrode of the LED chip is connected to the metal pad on the upper side of the positive electrode substrate, and the negative electrode of the LED chip is connected to the metal pad on the upper side of the negative electrode substrate.

[0014] Furthermore, the metal substrate is made of copper sheet with a thickness of 100-200μm, and the remaining thickness of the front half-etch is 50-100μm; the recessed area of ​​the front half-etch includes the tilted structure area of ​​the reflector cup structure and the welding platform area that exposes the metal surface.

[0015] Furthermore, the tilted structure of the reflective cup has a tilt slope of 50-70°; the EMC thickness of the unetched area of ​​the metal substrate is 50-150μm, and the EMC thickness of the half-etched area on the front side is 100-200μm.

[0016] Beneficial effects: This invention creates a recessed area by selectively etching the front side of a metal substrate, providing space for the LED chip to be thinned, thus effectively compressing the overall thickness of the packaged product in the chip placement area. At the same time, by injection molding EMC material to form a relatively thick EMC support, it ensures that the support has sufficient mechanical strength and workability during process flow and subsequent packaging processes, achieving a dual balance between local thinning and overall strength preservation.

[0017] This invention sets etched through holes in the non-cutting area and the non-front half-etched area of ​​the metal substrate. During the injection molding process, molten EMC material fills and penetrates the through holes. After solidification, an interlocking anchoring structure is formed on both sides of the metal substrate. This effectively avoids the risk of interlayer delamination caused by local thinning and injection molding thickening, and significantly improves the bonding strength and long-term reliability of heterogeneous interfaces under conditions such as thermal shock and mechanical stress.

[0018] In the injection molding process, the present invention uses an EMC material to form a reflective cup structure around the recessed area formed by the half-etching on the front side. This structure can effectively reflect and export the light emitted from the side of the LED chip, avoiding the problem of obstructed light output from the side due to the chip sinking into the recessed area. This ensures that the NCSP light source achieves an ultra-thin structure while maintaining its light extraction efficiency and brightness performance.

[0019] For non-planar EMC brackets with reflective cup recesses, this invention uses a dispensing tip needle transfer method to apply solder paste. Compared with the traditional solder paste printing process that is only applicable to planar substrates, this method is not limited by non-planar structures and can achieve precise solder paste application and die bonding at the pad position at the bottom of the recess. While ensuring reliable solder strength, it provides key process support for compressing the overall thickness of the package. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the main method steps of the present invention; Figure 2 This is a schematic diagram of the NCSP light source structure of the present invention; Figure 3 This is a top view of the metal substrate structure of the present invention; Figure 4 This is a top view of the metal substrate and EMC material of the present invention.

[0022] Explanation of reference numerals in the attached diagram: 1. LED chip; 2. Metal substrate; 21. Recessed area; 3. EMC material; 4. Phosphor adhesive; 5. Solder paste; 6. Through-hole. Detailed Implementation

[0023] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0024] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0025] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0026] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0027] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0028] Example 1: Reference Figures 1-4 As shown, this embodiment provides a method for fabricating an ultrathin NCSP light source, including the following steps: Step S1: Selective etching is performed on the metal substrate using an etchant and dry film photoresist. A semi-etching process is performed on the front side of the metal substrate at a predetermined die-bonding location to form a recessed area. The remaining thickness after semi-etching is 50-100 μm, specifically 75 μm, while the initial thickness of the metal substrate is 100-200 μm, specifically 150 μm. Simultaneously, etch-through perforation is performed in the non-cutting area and the non-front-side semi-etched area to form a through-hole structure penetrating the metal substrate. In the recessed area formed by the front-side semi-etching, a portion is used to form a tilted structure, and another portion exposes the metal surface to provide a thinner welding platform. This etch-through perforation and tilted structure enhance the mechanical interlocking force and interfacial bonding strength between the EMC material and the metal substrate in the subsequent injection molding process.

[0029] Step S2: On the surface of the metal substrate completed in step S1, a nickel layer is first electroplated, followed by a silver layer, to form a NiAg plating layer. The nickel plating layer thickness is ≥0.5μm, and the silver plating layer thickness is ≥0.5μm to provide good conductivity and soldering protection.

[0030] Step S3: The metal substrate treated by electroplating in step S2 and the EMC material are placed together in a high-temperature mold. The EMC material is melted, flowed, and fully fills the mold cavity and etched through holes through a hot pressing process. After solidification, an EMC support is formed. In the injection-molded EMC support, the EMC material forms an inclined structure with a reflective cup structure with a slope of 50-70° at the edge of the recessed area, and a welding platform is formed by exposing the metal surface in the middle of the recessed area.

[0031] Specifically, the reflector cup structure can have a 60° tilt slope to reflect light emitted from the side of the chip, preventing obstruction of side light emission. The EMC material thickness at the unetched areas of the metal substrate is 50-150μm, specifically 100μm, while the EMC material thickness at the half-etched areas on the front side is 100-200μm, specifically 175μm, maintaining the overall support thickness to ensure mechanical strength.

[0032] The outer side of the inclined structure is connected to the upper side of the EMC material of the non-front half-etched area on the upper side of the metal substrate, and the inner side is connected to the recessed area of ​​the metal substrate, thereby forming a reflective cup structure surrounding the welding platform.

[0033] Step S4: Apply solder paste using a die bonder with a dispensing tip. Use low-viscosity solder paste formulated with ultrafine solder powder of T6 grade (5μm to 15μm) or T7 grade (2μm to 11μm) particle size. Dip the solder paste from the dispensing tip into the pads of the EMC support, allowing it to spread and form a uniform thin layer on the pad surface. Then, according to the die bond drawing, fix the LED chip onto the solder paste and cure it via reflow soldering. The cured solder paste layer thickness is 10-20μm, specifically 15μm. This method overcomes the limitations of traditional planar substrate processes, achieving precise soldering and reliable die bonding on non-planar EMC supports with reflector cup recesses.

[0034] Step S5: Apply and cure phosphor adhesive around and on the top surface of the LED chip. Mix phosphor and transparent silicone in a specific ratio and degas. Attach a frosted release film to the mold. Apply the mixed phosphor adhesive to the frosted release film in a predetermined amount. Then, vacuum heat the mold to form and cure the mixture. The curing temperature is 80℃-150℃, and the curing time is 180-900 seconds. The amount of phosphor used is 0.5 to 3 times that of the transparent silicone, or 100% transparent silicone can be used. The transparent silicone can be 100% high-refractive-index, 100% medium-refractive-index, or 100% low-refractive-index transparent silicone to suit different light emission requirements.

[0035] Step S6: Cut the product horizontally and vertically along the cutting path according to the preset NCSP product size to obtain a single NCSP finished product. After cutting, dehumidify the NCSP light source, remove the adhesive, and mold the NCSP product onto another UV film with its back electrode facing upwards.

[0036] Step S7: Perform photoelectric parameter testing and binning on the NCSP products with the back electrode facing up. After testing, remove the adhesive again and transfer the NCSP products onto another UV film with the fluorescent adhesive side facing up; then remove the adhesive again and sort according to the test results. After sorting, package the products into bins to complete the finished product preparation.

[0037] As a further improvement of this embodiment, before cutting during the preparation process, a whole metal substrate composed of multiple single metal substrates is used to realize the preparation method of steps S1-S5. The horizontal and vertical connections of the single metal substrates form a whole metal substrate, and after division, each single metal substrate is equipped with an LED chip.

[0038] In this embodiment, a through-hole structure is formed at each of the four corners of each individual metal substrate.

[0039] As a further improvement to this embodiment, a notch is provided on the back of one of the positive and negative electrode substrates as a mark to distinguish between the positive and negative electrodes.

[0040] Example 2: This embodiment provides an ultrathin NCSP light source, which can be fabricated using the above-described method, including a metal substrate, EMC material, LED chip, solder paste, and phosphor. The metal substrate includes a positive substrate and a negative substrate, which are separated by the EMC material. The positive and negative substrates each have recessed areas and through-holes. Thus, the positive and negative substrates are not directly connected and are formed into a single structure by the EMC material.

[0041] The metal substrate has a recessed area formed by half-etching on the front side at a predetermined die-bonding position, and through-holes are formed in the non-recessed area. EMC material is injection molded onto the metal substrate and fills the through-holes. After curing, an interlocking anchoring structure is formed on both sides of the metal substrate, which significantly enhances the bonding force of the heterogeneous interface.

[0042] EMC material forms a reflective cup structure around the recessed area. This reflective cup structure has a 50-70° tilt slope, specifically a 60° tilt slope, to reflect light emitted from the side of the LED chip and improve light extraction efficiency.

[0043] LED chips are flip-chip chips, which are applied to exposed metal pads in the recessed area using solder paste.

[0044] Specifically, the positive electrode of the LED chip is connected to the metal pads on the upper side of the positive electrode substrate, and the negative electrode of the LED chip is connected to the metal pads on the upper side of the negative electrode substrate. Phosphor adhesive is applied to the perimeter and top surface of the LED chip.

[0045] The metal substrate is made of copper sheet with a thickness of 100-200μm, specifically 150μm. The remaining thickness of the half-etched front side is 50-100μm, specifically 75μm.

[0046] The semi-etched recessed area on the front side includes the tilted structure area of ​​the reflector cup structure and the welding platform area exposing the metal surface. A portion of the semi-etched recessed area forms the tilted structure to increase the bonding area and mechanical interlocking force between the EMC material and the metal substrate; another portion exposes the metal surface to provide a thinner welding platform. The thickness of the EMC material in the unetched areas of the metal substrate is 50-150 μm, specifically 100 μm; the thickness of the EMC material in the semi-etched areas on the front side is 100-200 μm, specifically 175 μm; and the overall EMC material thickness is 250 μm.

[0047] The solder paste is a low-viscosity solder paste formulated with ultrafine solder powder of T6 or T7 grade particle size. It can be any of the following: low temperature solder paste, medium temperature solder paste, or high temperature solder paste. The thickness of the solder paste is 10-20μm, specifically 15μm, to ensure reliable soldering strength while compressing the overall thickness.

[0048] As a preferred embodiment, the fluorescent adhesive is a mixture of fluorescent powder and silicone or silicone alone.

[0049] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above 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.

[0050] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for fabricating an ultrathin NCSP light source, characterized in that, include: Selective etching is performed on the metal substrate. A semi-etch is performed on the front side at the preset die-bonding location to form a recessed area. Through-hole etching is then performed in the non-cutting area and the non-front-side semi-etched area to form vias. A metal layer is electroplated onto the etched metal substrate surface. The electroplated metal substrate and EMC material are placed together in a mold for injection molding. The EMC material melts, flows, fills the mold cavity and vias, and solidifies to form an EMC support. A reflective cup structure is formed around the recessed area. Solder paste is applied to the pads of the EMC support using a dispensing needle transfer method. The LED chip is then fixed onto the solder paste and cured. Phosphor adhesive is applied around and on the top surface of the LED chip and cured. NCSP light source is obtained by cutting.

2. The method for fabricating an ultrathin NCSP light source according to claim 1, characterized in that, The remaining thickness of the metal substrate after the front half-etching process is 50-100μm, and the initial thickness of the metal substrate is 100-200μm.

3. The method for fabricating an ultrathin NCSP light source according to claim 1, characterized in that, In the electroplating step, a nickel layer is first electroplated on the surface of the metal substrate, followed by a silver layer, wherein the thickness of the nickel plating layer is ≥0.5μm and the thickness of the silver plating layer is ≥0.5μm.

4. The method for fabricating an ultrathin NCSP light source according to claim 1, characterized in that, In the EMC support formed by injection molding, the EMC material forms an inclined structure of a reflective cup structure at the edge of the recessed area, and forms a welding platform on the exposed metal surface in the middle of the recessed area.

5. The method for fabricating an ultrathin NCSP light source according to claim 1, characterized in that, In the step of applying solder paste, a low-viscosity solder paste is prepared by selecting one of the solder powders with particle sizes of T6 and T7. The solder paste is picked up from the glue tray by the dispensing head and applied to the pad position. The thickness of the cured solder paste layer is 10-20μm.

6. The method for fabricating an ultrathin NCSP light source according to claim 1, characterized in that, In the process of setting up the fluorescent adhesive, the fluorescent powder is mixed with transparent silicone to remove bubbles and then applied to the frosted release film. The film is then vacuum heated and molded for curing. The curing temperature is 80℃-150℃ and the curing time is 180 seconds-900 seconds. After cutting, the NCSP light source is dehumidified. After descaling, the film is molded with the back electrode facing up for photoelectric parameter testing. The film is then re-attached with the fluorescent adhesive side facing up and sorted, taped, and packaged.

7. An ultrathin NCSP light source, characterized in that, The device includes a metal substrate, EMC material, an LED chip, solder paste, and phosphor adhesive. The metal substrate has a recessed area formed by half-etching on the front side at a predetermined die-bonding position, and through-holes are formed in the non-recessed area. The EMC material is injection molded onto the metal substrate and fills the through-holes. The EMC material forms a reflective cup structure around the recessed area. The LED chip is placed on the exposed metal pads in the recessed area via the solder paste. The phosphor adhesive covers the periphery and top surface of the LED chip.

8. The ultrathin NCSP light source according to claim 7, characterized in that, The metal substrate includes a positive electrode substrate and a negative electrode substrate, which are respectively provided with the recessed area and the etched through hole; the positive electrode substrate and the negative electrode substrate are separated by the EMC material; the positive electrode of the LED chip is connected to the metal pad on the upper side of the positive electrode substrate, and the negative electrode of the LED chip is connected to the metal pad on the upper side of the negative electrode substrate.

9. The ultrathin NCSP light source according to claim 7, characterized in that, The metal substrate is made of copper sheet with a thickness of 100-200μm, and the remaining thickness of the front half-etch is 50-100μm; the recessed area of ​​the front half-etch includes the tilted structure area of ​​the reflector cup structure and the welding platform area that exposes the metal surface.

10. The ultrathin NCSP light source according to claim 7, characterized in that, The tilted structure of the reflector cup has a tilt slope of 50-70°; the thickness of the EMC material in the unetched area of ​​the metal substrate is 50-150μm, and the thickness of the EMC material in the half-etched area on the front side is 100-200μm.

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