A method for preparing a secondary-etched LED lead frame

Abstract

The application discloses a kind of secondary etching LED lead frame preparation method, through twice etching procedure, the etching depth of second groove can be made enough deep, to reduce the distance between the groove bottom of first groove and the groove bottom of second groove, facilitate subsequent cutting procedure.Due to the depth of second groove is enough deep, in subsequent cutting procedure, the part that tool needs to cut is very small, thereby prolonging the service life of cutting tool, reduce tool wear rate.Moreover, the lead frame prepared by secondary etching is more convenient for cutting in subsequent cutting process, can also eliminate the crack and other problems caused by the thickness of metal base material during cutting, improve product quality, thereby improve work efficiency.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device technology, and more specifically to a method for preparing an LED lead frame by secondary etching. Background Technology

[0002] Existing methods for manufacturing LED brackets involve processing metal substrates through etching, electroplating, and injection molding. During the etching process, the metal substrate needs to be etched to form multiple spaced welding areas. Each welding area needs to have grooves or other structures etched into it. These grooves or other structures can form an insulating layer in the subsequent injection molding process, thus separating the electrodes in each welding area.

[0003] See patent document CN2017103127652, which discloses an LED packaging structure; see appendix. Figure 1 The packaging structure includes a conductive frame 100, which has multiple spaced-apart metal regions 210. Each metal region 210 contains a die-bonding region 214, a first electrode 216, and a second electrode 218. The metal regions 210 are separated by resin portions 300. Insulating portions are provided between the first electrode 216 and the die-bonding region 214, and between the die-bonding region 214 and the second electrode 218. The insulating portions are two independent parts: a first groove 401 formed on its top surface and a second groove 402 formed on its bottom surface. Both the first groove 401 and the second groove 402 need to be injection-molded and filled with insulating material. Figure 2 In order to prevent electrical connections between the first electrode 216 and the die-bonding region 214 and between the die-bonding region 214 and the second electrode 218, a pre-cut groove 500 needs to be cut at the second groove 402 after injection molding. After the pre-cut groove 500 is formed, injection molding needs to be performed again to achieve insulation between the first electrode 216 and the die-bonding region 214 and between the die-bonding region 214 and the second electrode 218.

[0004] Combination Figure 1 and Figure 2Both the first groove 401 and the second groove 402 are prepared by an etching process. The cutting tool used when cutting the pre-cut groove 500 is a consumable. The service life and cutting effect of the cutting tool depend on the distance between the bottom of the first groove 401 and the bottom of the second groove 402, i.e., the thickness of the conductive frame 100 between them. If the distance between them is long, it means that the thickness is thick, the tool wears faster, the tool service life is shorter, and the production cost and efficiency will be affected. If the distance between them is short, it means that the thickness is thinner, and the structural strength of the conductive frame 100 does not meet the production requirements. In the actual production process, the first groove 401 and the second groove 402 are prepared by a single etching process, that is, the first groove 401 and the second groove 402 are formed simultaneously through a single etching step. Under the premise that the contour structure of the first groove 401 and the structural strength of the conductive frame 100 meet the production requirements, the etching depth of the second groove 402 is limited. This will result in a thicker distance between the bottom of the first groove 401 and the bottom of the second groove 402, thereby accelerating the wear of the cutting tool. Furthermore, during the cutting process, it may cause cracks in some parts of the product. It may also cause the contour structure of the second groove 402 to fail to meet the production requirements, resulting in problems such as low product yield and low work efficiency. Summary of the Invention

[0005] The purpose of this invention is to provide a method for fabricating LED lead frames using a secondary etching process. This method solves the problems of low yield and rapid tool wear in the past.

[0006] This invention provides a method for fabricating an LED lead frame using secondary etching, comprising the following steps:

[0007] Step A: A first etching process is used to etch a first groove or hollow part on the top surface of the metal substrate to prepare the LED bracket substrate.

[0008] Step B, injection molding, involves injection molding the LED bracket substrate prepared in step A to fill the first groove or hollow part with the injection material. After the injection material solidifies, a flat plate is prepared.

[0009] Step C, one-time degumming, degumming the surface of the flat plate prepared in step B;

[0010] Step D, secondary etching: The bottom surface of the plate after the adhesive removal in step C is etched a second groove.

[0011] Step E, electroplating: Electroplating is performed on the flat plate from step D using electroplating equipment to form a metallic reflective layer.

[0012] In step A, the metal substrate is either a copper substrate or an iron substrate. Furthermore, the following steps are included between steps D and E:

[0013] Step F: Applying film. Applying film to the bottom surface of the flat plate prepared in step D.

[0014] Step G, secondary injection molding: The flat plate after degumming in step F is injected through an injection molding machine. After the injection molding material solidifies, a reflective cup is formed on the surface of the flat plate, thus preparing the LED bracket.

[0015] Step H, secondary adhesive removal, involves removing the adhesive from the surface of the LED bracket prepared in step G.

[0016] The injection molding material used in step G and the injection molding material used in step B are the same or different thermosetting materials.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) By setting two etching processes, after the metal substrate is etched and injected once, it is ensured that the metal substrate has sufficient structural strength and the first groove meets the production requirements. Then, a second etching is performed. In the second etching, the structural strength of the metal substrate does not need to be considered. Thus, the etching depth of the second groove can be made deep enough, thereby reducing the distance between the bottom of the first groove and the bottom of the second groove, that is, reducing the thickness of the metal substrate at that point, which facilitates the subsequent cutting process. Since the depth of the second groove is deep enough, the part that the tool needs to cut in the subsequent cutting process is very small, thereby extending the service life of the cutting tool and solving the problem of the previous tool wear rate.

[0019] (2) During the secondary etching process, since the contour structure of the second groove is not limited by the strength of the first groove or the metal substrate structure, the contour structure of the second groove can be made smoother, thereby improving the quality of the product, increasing the yield, and improving the work efficiency.

[0020] (3) The lead frame prepared by secondary etching is easier to cut in subsequent cutting processes, eliminating problems such as cracks caused by the thick metal substrate during cutting, improving product quality, and thus improving work efficiency. Attached Figure Description

[0021] Figure 1 This is a cross-sectional view of an existing LED packaging structure;

[0022] Figure 2 This is a cross-sectional view of an existing LED packaging structure with pre-set grooves.

[0023] Figure 3This is a schematic diagram of the structure of the metal substrate after a single etching in Example 1;

[0024] Figure 4 This is a schematic diagram of the structure of the LED bracket substrate after one injection molding in Example 1;

[0025] Figure 5 This is a schematic diagram of the structure of the plate after secondary etching in Example 1;

[0026] Figure 6 This is a partial cross-sectional view of the flat plate after secondary etching in Example 1;

[0027] Figure 7 This is a schematic diagram of the structure of the flat plate after secondary injection molding in Example 2;

[0028] Figure 8 This is a partial cross-sectional view of the flat plate after secondary injection molding in Example 2. Detailed Implementation

[0029] To better understand and implement this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings.

[0030] In the description of this invention, it should be noted that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0032] Example 1

[0033] One specific embodiment of the method for fabricating a secondary etched LED lead frame according to the present invention, wherein the LED lead frame in this embodiment is a product without the reflector cup 40, combined with Figures 3 to 6 The preparation method includes the following steps:

[0034] Step A: Etching is performed once to etch a first groove or hollow part 11 on the top surface of the metal substrate 10 to prepare the LED bracket substrate.

[0035] Step B involves a single injection molding process. The LED bracket substrate prepared in Step A is injection molded using an injection molding machine to fill the first groove or hollow portion 11 with the injection material. After the injection material solidifies, a flat plate is formed. It should be noted that the hollow portion 11 forms an insulating portion 20 after injection molding, which is mainly used to insulate and separate multiple welding areas. The first groove is an optional feature, used to cooperate with subsequent cutting processes to insulate and separate the electrodes and die-bonding areas within each welding area.

[0036] Step C, primary adhesive removal, involves removing adhesive from the surface of the flat plate prepared in step B. Adhesive removal is mainly used to remove residual adhesive after injection molding.

[0037] Step D, secondary etching: The bottom surface of the plate after adhesive removal in step C is etched a second time to create a second groove 30. Since the metal substrate 10 after the first etching has already been injection molded in step B, ensuring that the plate prepared in step B has sufficient structural strength, there is no need to consider whether the metal substrate 10 has sufficient structural strength during the secondary etching process. The contour structure and etching depth of the second groove 30 are not limited by other external factors, thus allowing the etching depth of the second groove 30 to be set sufficiently deep, providing a more convenient and faster cutting basis for subsequent cutting processes.

[0038] It should be noted that the purpose of the groove is to reduce wear on the cutting tool during metal cutting. If the etching depth of the second groove 30 can be set sufficiently deep, then the first groove is unnecessary. Therefore, the setting of the first groove is an optional feature. Figure 6 If the metal substrate 10 does not have a first groove, it can be considered that the bottom of the first groove is flush with the top surface of the metal substrate 10. In this case, the etching depth of the second groove 30 can be set to be deep enough to meet the cutting thickness requirements of the metal substrate 10 at that location.

[0039] Step E: Electroplating. The flat plate from step D is electroplated using electroplating equipment to form a metallic reflective layer. Optionally, the metallic material used for electroplating can be gold, silver, copper, nickel, palladium, etc., and the electroplated layer can be at least one of the above-mentioned metallic material coatings.

[0040] Compared to the existing technology that forms the first groove (cutout 11) and the second groove 30 through a single etching process, firstly, the contours and depths of the second groove 30 and the first groove (cutout 11) may not meet requirements, and secondly, glue overflow may occur during injection molding, making it impossible to remove during the washing and film removal process. The preparation method of this embodiment, by setting two etching processes, ensures that the metal substrate 10 has sufficient structural strength and that the first groove meets production requirements after the first etching and injection molding. Then, a second etching process is performed. In the second etching, the structural strength of the metal substrate 10 does not need to be considered, allowing the etching depth of the second groove 30 to be sufficiently deep. This reduces the distance between the bottom of the first groove and the bottom of the second groove 30, facilitating subsequent cutting processes. Because the depth of the second groove 30 is sufficient, the portion that the cutting tool needs to cut in the subsequent cutting process is very small, thereby extending the service life of the cutting tool and solving the problem of rapid tool wear in the past. Furthermore, glue overflow will not occur during the subsequent injection molding process. During the secondary etching process, since it is not limited by the contour structure of the first groove or the structural strength of the metal substrate 10, the contour structure of the second groove 30 can be made smoother, thereby improving product quality, yield, and work efficiency. The lead frame prepared by secondary etching is easier to cut in subsequent cutting processes, eliminating problems such as cracks caused by the thickness of the metal substrate 10 during cutting, improving product quality, and thus increasing work efficiency.

[0041] As a preferred embodiment, step A further includes the following steps:

[0042] Step a, primary dust removal: First, the top surface of the metal substrate 10 is dusted using a dust removal machine. The metal substrate 10 is placed in the dust removal machine, which drives the adhesive paper towards the metal substrate 10, so that the dust on the metal substrate 10 adheres to the adhesive paper. Optionally, the pressure of the adhesive paper in the dust removal machine is 0.2–0.4 MPa.

[0043] Step b, preheating: The dust-removed metal substrate 10 is preheated in a preheating machine at a temperature of 90-110°C. Preheating facilitates subsequent bonding with the dry film.

[0044] Step c: Applying dry film. The preheated metal substrate 10 enters the laminating machine, which applies dry film to the top surface of the metal substrate 10. The laminating machine's conveying speed is 2.3–3.3 m / min, the temperature of the hot pressing roller used for lamination is 110–120°C, and the pressure of the hot pressing roller is 0.3–0.5 MPa. The temperature of the cutting strip is 40–60°C. After each metal substrate 10 is laminated, the laminating machine hot-presses an indentation area into the dry film. The upper and lower layers of dry film are laminated together, with no metal substrate 10 between them, so that the indentation area is formed between two adjacent laminating stations. The width tolerance of the indentation area is ≤2 mm. This can be determined by measuring the width of the indentation area with a ruler to see if it is within the tolerance range. The indentation area can also be observed to be flat, clean, and free of air bubbles, thus determining whether the lamination of the dry film and the metal substrate 10 is uniform and whether the lamination quality meets production standards.

[0045] Step d, exposure: After the dry film is attached to the metal substrate 10, a portion of the dry film on the top surface of the metal substrate 10 is exposed to allow the dry film to form a pattern. Optionally, a secondary dust removal process can be performed before exposure.

[0046] Step e, development, using a developing solution to remove unexposed areas of the dry film. The developing solution is a potassium carbonate solution with a mass concentration of 8–14 g / L.

[0047] Step f, a single water wash, using pure water to clean the residual developer on the surface of the dry film.

[0048] Step g, etching: using an etching solution to etch the hollow portion 11 and the groove 11 into the metal substrate 10. The etching solution includes components with the following mass concentrations: Cu 2+ The concentration is 120-150 g / L, the hydrochloric acid concentration is 0.7-1.3 mol / L, and the remainder is pure water.

[0049] Step h, secondary water washing, using pure water to clean the residual etching solution on the metal substrate 10.

[0050] Step i, remove the dry film by using a film removal accelerator to remove the dry film on the top surface of the metal substrate 10.

[0051] Step j: Three water washes are performed to clean the residual film removal accelerator on the metal substrate 10 using pure water.

[0052] Step k, pickling, uses a pickling solution to clean the residual film removal accelerator. The pickling solution can be 3-5% sulfuric acid, 6-20 g / L hydrogen peroxide, and Cu. 2+ One or more of the following micro-etching solutions with a concentration of 5–45 g / L. Optionally, pickling can be performed in two separate pickling operations.

[0053] Step 1: Wash four times with pure water to clean the residual pickling solution from the metal substrate 10.

[0054] Step m, drying: the metal substrate 10 is dried at a temperature of 80-100°C to form an LED bracket substrate.

[0055] Preferably, a semi-etched roughening process can be added to step A, referring to step n, to roughen the LED bracket substrate prepared in step m. Roughening the hollowed-out areas and semi-etched areas improves the bonding force between the epoxy resin and the substrate, thereby improving the airtightness of the bracket. The specific roughening process involves forming etching marks or textures of a certain depth on the material surface. The etching depth and texture type can be controlled by adjusting the concentration of the etchant, temperature, exposure time, and the properties of the material itself. After etching, further processing (such as cleaning and drying) may be required to remove residual etchant and improve surface quality. Roughening involves treating the workpiece surface using mechanical or chemical methods to change the morphology and structure of the material surface, increasing surface roughness. Mechanical methods typically include sandblasting and grinding, which physically create tiny protrusions and depressions on the material surface, thereby increasing surface roughness. Chemical etching utilizes chemical reactions to create tiny protrusions and shell-like structures on the surface of materials, achieving a roughening effect. For example, acidic or alkaline solutions can be used to chemically etch metal surfaces, making them rougher. The main purpose of this roughening process is to improve the material's frictional properties, adhesion, fatigue resistance, and corrosion resistance.

[0056] In this embodiment, the roughening process can be carried out using acidic or alkaline solutions.

[0057] Optionally, step n includes the following steps:

[0058] Step S1, pure water cleaning: The LED bracket substrate prepared in step n is cleaned with pure water.

[0059] Step S2, degreasing: The LED bracket substrate cleaned in step S1 is degreased with sulfuric acid of concentration 3-5%.

[0060] Step S3, ultra-roughening: The roughening solution is sprayed onto the area of ​​the LED bracket substrate to be roughened. The ultra-roughening temperature is 24-28℃. The Cu content of the roughening solution... 2+ The concentration is 15–45 g / L, and the micro-etching depth is 0.6–1 μm.

[0061] Step S4, pickling, the pickling solution is a hydrochloric acid solution, wherein the hydrochloric acid concentration is 3-4%, Cu 2+ Content ≤2g / L, pickling temperature 80~100℃.

[0062] Step S5: Drying. The LED bracket substrate is dried at a temperature of 80-100°C.

[0063] Step S6: Water break test. The pickled LED bracket substrate is subjected to a water break test, and the water hanging time is ≥30 s. Specifically, a piece of LED bracket substrate is placed in pure water and then vertically taken out. If water is still hanging on the entire LED bracket substrate after 30 s, it is qualified. If the water breaks in advance, it means that the board surface is not clean or even has oil, and such workpieces will affect the product quality in the subsequent processes.

[0064] It should be noted that the specific steps of the secondary etching in Step D are similar to or the same as those of the primary etching in Step A, and whether to perform the roughening process can be selected according to the actual situation.

[0065] Embodiment 2

[0066] The second specific implementation manner of the preparation method of the secondary-etched LED lead frame of the present invention. The LED lead frame in this embodiment is a product with a reflector cup 40. Combining Figures 7 to 8 , the preparation method further includes Step F, Step G, and Step H between Step D and Step E, which respectively correspond to the steps of film pasting, secondary injection molding, and secondary degumming.

[0067] In Step F, the bottom surface of the flat plate prepared in Step D needs to be pasted with a film, which is mainly used to eliminate the problem of overflowing glue.

[0068] In Step G, the flat plate after degumming in Step F is injection molded through an injection molding device to form a reflector cup 40. After the injection molding material solidifies and forms, a reflector cup 40 is formed on the surface of the flat plate, and an LED bracket is prepared.

[0069] Step H: Secondary degumming. The surface of the LED bracket prepared in Step G is degummed.

[0070] Optionally, the injection molding material used in Step G and the injection molding material used in Step B are the same or different thermosetting materials, that is, different thermosetting materials can be used for the insulating part 20 and the reflector cup 40 part, so that materials with different colors and different chemical properties can be selected to better composite with the metal substrate 10 or achieve better optical effects. For example, the insulating part 20 on the flat plate can be formed by using an injection molding material with lower cost, better stability or better bonding force with the substrate, and the reflector cup 40 can be made of a rubber material with high reflectivity, so as to meet the lighting requirements and solve the problem of poor bonding between the previous rubber material and the metal substrate.

[0071] While the embodiments disclosed in this invention are as described above, the content is merely for the purpose of facilitating understanding of the invention and is not intended to limit the invention. Any person skilled in the art to which this invention pertains may make any modifications and variations in form and detail of the implementation without departing from the spirit and scope disclosed herein; however, the scope of patent protection for this invention shall still be determined by the scope defined in the appended claims.

Claims

1. A method for fabricating an LED lead frame using secondary etching, characterized in that, Includes the following steps: Step A: A first etching process is used to etch a first groove or hollow part on the top surface of the metal substrate to prepare the LED bracket substrate. Step B, injection molding, involves injection molding the LED bracket substrate prepared in step A to fill the first groove or hollow part with the injection material. After the injection material solidifies, a flat plate is prepared. Step C, one-time degumming, degumming the surface of the flat plate prepared in step B; Step D, secondary etching: The bottom surface of the plate after the adhesive removal in step C is etched a second groove. Step E, electroplating: Electroplating is performed on the flat plate from step D using electroplating equipment to form a metallic reflective layer; It also includes a semi-etched roughening treatment of the LED bracket substrate prepared in step A, including the following steps: Step S1, pure water cleaning: the prepared LED bracket substrate is cleaned with pure water; Step S2, degreasing: The LED bracket substrate cleaned in step S1 is degreased with sulfuric acid with a concentration of 3-5%. Step S3, ultra-roughening: The roughening solution is sprayed onto the area of ​​the LED bracket substrate to be roughened. The ultra-roughening temperature is 24-28℃. The Cu content of the roughening solution... 2+ The concentration is 15–45 g / L, and the micro-etching depth is 0.6–1 μm; Step S4, pickling, the pickling solution is a hydrochloric acid solution, wherein the hydrochloric acid concentration is 3-4%, Cu 2+ Content ≤2g / L, pickling temperature 80~100℃; Step S5, drying: The LED bracket substrate is dried at a temperature of 80-100℃. Step S6, water breakage test: The acid-washed LED bracket base is subjected to a water breakage test, and the water hanging time is ≥30s.

2. The method for fabricating an LED lead frame by secondary etching according to claim 1, characterized in that, The metal substrate in step A is a copper substrate or an iron substrate.

3. The method for fabricating an LED lead frame by secondary etching according to claim 1 or 2, characterized in that, The following steps are also included between step D and step E: Step F: Applying film. Applying film to the bottom surface of the flat plate prepared in step D. Step G, secondary injection molding: The flat plate after degumming in step F is injected through an injection molding machine. After the injection molding material solidifies, a reflective cup is formed on the surface of the flat plate, thus preparing the LED bracket. Step H, secondary adhesive removal, involves removing the adhesive from the surface of the LED bracket prepared in step G.

4. The method for fabricating an LED lead frame by secondary etching according to claim 3, characterized in that, The injection molding material used in step G and the injection molding material used in step B are the same or different thermosetting materials.

5. The method for fabricating an LED lead frame by secondary etching according to any one of claims 1-2 and 4, characterized in that, Step A includes the following steps: Step a, primary dust removal: First, perform primary dust removal on the top surface of the metal substrate. Place the metal substrate into the dust removal machine for dust removal. The pressure of the dust removal paper in the dust removal machine is 0.2-0.4 MPa. Step b, preheating: The dust-removed metal substrate is put into a preheating machine for preheating at a temperature of 90-110°C. Step c, applying dry film: The preheated metal substrate is fed into the laminating machine, and dry film is applied to the top surface of the metal substrate. The conveying speed of the laminating machine is 2.3 to 3.3 m / min, the temperature of the hot pressing roller used for lamination is 110 to 120°C, and the pressure of the hot pressing roller is 0.3 to 0.5 MPa. The temperature of the laminating strip used for cutting is 40 to 60 degrees Celsius. Step d, exposure: After the dry film is attached to the metal substrate, a portion of the dry film is exposed to allow the dry film to form a pattern. Step e, development, using a developing solution to remove unexposed areas of the dry film. The developing solution is a potassium carbonate solution with a mass concentration of 8-14 g / L. Step f, a single water wash, using pure water to clean the residual developer on the surface of the dry film; Step g, etching: using an etching solution to etch open areas and grooves into the metal substrate. The etching solution comprises the following components at the following mass concentrations: Cu 2+ The concentration is 120–150 g / L, the hydrochloric acid concentration is 0.7–1.3 mol / L, and the remainder is pure water; Step h, secondary water washing, using pure water to clean the residual etching solution from the metal substrate; Step i, Remove the dry film by using a film removal accelerator to remove the dry film on the top surface of the metal substrate; Step j: Three water washes are performed to clean the residual film removal accelerator on the metal substrate using pure water. Step k, pickling, uses a pickling solution to clean the residual film removal accelerator. The pickling solution can be 3-5% sulfuric acid, 6-20 g / L hydrogen peroxide, and Cu. 2+ One or more combinations of micro-etching solutions with a concentration of 5–45 g / L; Step 1: Four water washes are performed to clean the residual pickling solution from the metal substrate using pure water. Step m, drying: The metal substrate is dried at a temperature of 80-100℃ to form an LED bracket substrate; Step n involves roughening the LED bracket substrate prepared in step m using a semi-etching process.

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