A core mold and method for electroforming metal trumpet-shaped tapered hole micro-nozzle

Abstract

The patent of the present invention belongs to the field of micro-electroforming, and specifically relates to a core mold and method for electroforming for manufacturing metal trumpet-shaped conical-hole micro-nozzles. A core mold for electroforming for manufacturing metal trumpet-shaped conical-hole micro-nozzles includes a substrate, a conductive layer and an electrically insulating layer tightly adhered to the upper surface of the substrate in sequence, and regularly arranged blind holes penetrating the conductive layer and the electrically insulating layer; the substrate is an electrically insulating material; the bottom of the blind hole is the upper surface of the substrate. A method for manufacturing metal trumpet-shaped conical-hole micro-nozzles includes first electroforming the core mold as a cathode; then, using an ultra-precision machining device to thin and flatten the core mold; dissolving and removing the electrically insulating layer and the conductive layer to obtain a metal trumpet-shaped conical-hole micro-nozzle. The present invention solves the problem of mass production of straight outer-walled metal trumpet-shaped conical-hole micro-nozzles with small dimensions and smooth inner and outer wall surfaces. The core mold preparation process of the present invention has good compatibility and is easy to implement.

Description

[0001] The invention belongs to the field of micro electroforming, and in particular relates to an electroforming core mold and a method for manufacturing a metal trumpet-shaped tapered hole micro nozzle. Background Art

[0002] Metal conical-hole micronozzles are increasingly used in the automotive, aerospace, and medical device industries, for example in engine fuel injectors and medical waterjet nozzles. However, due to their need to operate under favorable fluid dynamics conditions, metal conical-hole micronozzles have specific and stringent requirements for their geometric dimensions, shape characteristics, surface quality, and material properties. This has led to the manufacture of high-performance metal conical-hole micronozzles being a persistent challenge in the industry.

[0003] Metal micronozzles with tapered holes are typically manufactured using methods such as laser processing, electrospark machining (EDM), electrolytic machining, or electroforming. Patent application number CN202010331415.2 provides a process for laser processing tapered holes. However, laser-processed tapered holes inevitably develop recast layers and even microcracks on the hole walls, resulting in a rough surface and often a buildup at the lower end of the hole. These factors often require post-processing to remove these thermally induced defects. However, smoothing the inner walls of deep microholes is technically challenging, and there is no low-cost, efficient, and high-quality method for removing thermally induced defects internationally. Patent application number CN201210392034.0 describes an EDM method for producing inverted tapered holes. However, EDM removes metal by melting and vaporizing the metal at instantaneous high temperatures. Like laser processing, EDM removes metal, leaving recast layers and microcracks on the micro-tapered hole walls. Similarly, secondary polishing of the processed tapered hole is required, increasing process costs and limiting its applicability. Patent application number CN201110185863.7 discloses a method for electrochemical machining of trumpet-shaped micro-hole arrays, enabling the one-time formation and mass production of trumpet-shaped hole clusters. However, electrochemical machining suffers from low stability and precision, and its isotropic dissolution behavior makes it difficult to manufacture high-precision, large-taper micro-holes.

[0004] The metal cone-hole micro-nozzle produced by electroforming has smooth sidewalls, high precision and good consistency, and is often used in the mass production of high-performance metal cone-hole micro-nozzles. According to the forming method, electroforming micro-nozzles mainly include replication forming method and overgrowth forming method. The principle of electroforming micro-nozzle manufacturing by replication forming method is as follows Figure 1As shown. The electroforming layer replication forming method realizes nozzle manufacturing by reversely replicating the structure of the thick mask. In this way, if a nozzle with a trumpet-shaped deep micro-cone hole is required, the film core of the thick mask corresponding to the replicated cone hole must be a trumpet-shaped pointed cone structure with a large aspect ratio. However, it is extremely difficult to prepare such a photoresist film structure with existing technology. Therefore, in fact, there has been no report on the electroforming of a nozzle with a trumpet-shaped micro-cone hole with a large aspect ratio based on the replication forming method. The principle of electroforming of metal cone hole micro nozzles by overgrowth forming method is as follows. Figure 2 As shown. When the thickness of the electroformed layer exceeds the thickness of the substrate film defining the pattern, the layer both thickens longitudinally and expands outward, shifting its growth direction from the original one-dimensional direction (perpendicular to the substrate) to a two-dimensional direction: perpendicular to the substrate thickening direction and along the substrate film surface. Thus, the leading edge of the metal layer's growth is the vectorial composite of the two growth surfaces, i.e., an arc surface, which continuously converges to form a pore-like structure, i.e., a trumpet-shaped cone. This indicates that the micropores formed by overgrowth electroforming are typical trumpet-shaped cones. The thicker the electroformed layer, the smaller the diameter of the resulting micropores. Simultaneously, the outer diameter of the nozzle increases (the outer diameter wall exhibits a curved surface characteristic). The Proceedings of the 17th National Special Processing Academic Conference (Volume 1), 2017, pp. 714-724, presents a simulation analysis and experimental study of the electroforming of ultra-fine unidirectional trumpet hole arrays. Using the overgrowth forming method, a unidirectional trumpet hole array with a micropore diameter of 3μm and a mesh thickness of 35μm was fabricated. However, the practicality and applicability of the trumpet-shaped, tapered micronozzles produced by electroforming using the aforementioned overgrowth forming method have certain limitations. These limitations are primarily due to their large overall size, making them unsuitable for use in small or confined spaces, and the curved outer diameter surface complicates installation and positioning.

[0005] This patent combines the advantages of electroforming by replica molding and electroforming by overgrowth molding to develop an electroforming core mold and method for manufacturing metal trumpet-shaped tapered micronozzles. This allows for the mass production of straight-walled metal trumpet-shaped micronozzles with small dimensions and smooth inner and outer surfaces. Furthermore, the metal trumpet-shaped micronozzles of the present invention are easy to position and install. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the present invention provides a core mold and method for electroforming a metal trumpet-shaped tapered hole micro-nozzle. The technical solution of the present invention is as follows.

[0007] The invention provides a core mold for electroforming, which is a mold used for manufacturing a metal trumpet-shaped tapered hole micro-nozzle.

[0008] A core mold for electroforming used to manufacture a metal trumpet-shaped tapered hole micro-nozzle is characterized in that it includes a substrate, a conductive layer and an electrically insulating layer tightly adhered to the upper surface of the substrate in sequence, and regularly arranged blind holes penetrating the conductive layer and the electrically insulating layer; the substrate is an electrically insulating material; and the bottom of the blind holes is the upper surface of the substrate.

[0009] The thickness of the substrate is 1-3 mm.

[0010] The thickness h1 of the conductive layer is greater than 10 μm.

[0011] The thickness h2 of the electrical insulating layer is greater than or equal to the thickness h1 of the conductive layer.

[0012] The diameter D1 of the blind hole is less than twice the thickness h2 of the electrical insulation layer.

[0013] The hole spacing of the blind holes is greater than 3D1.

[0014] The diameter D1 of the blind hole is greater than 10 μm and less than 1000 μm.

[0015] The diameter D1 of the blind hole is equal to the outer diameter D of the metal trumpet-shaped tapered hole micro-nozzle to be manufactured.

[0016] The present invention also provides a method for manufacturing a metal trumpet-shaped tapered hole micro-nozzle, which is characterized in that it comprises the following steps:

[0017] (a) Electroforming with the mandrel as the cathode;

[0018] (b) When the thickness of the electroformed metal layer reaches a preset thickness h3 (h3 = h1 + D / 2 - d / 2) (d is the inner diameter of the metal trumpet-shaped tapered hole micronozzle to be manufactured), electroforming is stopped and the core mold with the electroformed metal layer is removed;

[0019] (c) After cleaning and drying the core mold with the electroformed metal layer, the electrical insulation layer on the core mold is thinned and leveled using an ultra-precision machining device until the thickness of the electroformed metal layer reaches the thickness h (h>h1) of the metal trumpet-shaped tapered micronozzle to be manufactured;

[0020] (d) After separating the electrical insulating layer and the conductive layer from the substrate, the electrical insulating layer and the conductive layer are dissolved and removed to obtain a metal trumpet-shaped conical hole micronozzle with a thickness of h, an inner diameter of d, and an outer diameter of D.

[0021] The electroformed metal layer will form a positioning platform after being thinned and leveled, and the positioning platform is used for installation and positioning when the metal trumpet-shaped tapered hole micro-nozzle is used.

[0022] Compared with the existing processing method of metal tapered hole micro nozzle, the present invention has the following outstanding advantages.

[0023] 1. The metal trumpet-shaped tapered hole micro-nozzle formed by electroforming of the present invention has smooth inner and outer wall surfaces, high precision, and good consistency when produced in batches.

[0024] 2. The present invention can realize the batch one-time production of metal micro-conical hole nozzles with a small and limited outer diameter, a smooth trumpet-shaped micro-conical hole inner diameter wall, and a straight outer diameter wall. It breaks through the limitations of the existing technology, does not require post-processing operations, and the resulting nozzles have a low unit cost, solving the manufacturing problem of double-micro (small outer dimensions, small cone hole diameter) trumpet-shaped cone hole micro-nozzles.

[0025] 3. The core mold preparation process has good compatibility and is easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the schematic diagram of the micro nozzle manufactured by electroforming using the replica forming method.

[0027] Figure 2 This is the principle diagram of electroforming metal conical hole micro nozzle by overgrowth forming method.

[0028] Figure 3 It is a schematic diagram of the core mold of the present invention.

[0029] Figure 4 It is a cross-sectional view of the blind hole on the core mold of the present invention.

[0030] Figure 5 It is a cross-sectional view of the blind hole after electroforming of the present invention is completed.

[0031] Figure 6 It is a schematic diagram of the ultra-precision machining device of the present invention machining a blind hole with an electroformed metal layer.

[0032] Figure 7 It is a schematic diagram of the metal trumpet-shaped tapered hole micro-nozzle of the present invention.

[0033] Figure 8 It is a three-dimensional schematic diagram of the metal trumpet-shaped tapered hole micro-nozzle of the present invention.

[0034] In the figure: 1. thick mask; 1-1. film core; 2. electroformed layer; 3. base film; 4. trumpet-shaped cone hole; 5. substrate; 6. conductive layer; 7. electrical insulating layer; 8. blind hole; 9. core mold; 10. electroformed metal layer; 11. ultra-precision machining device; 12. metal trumpet-shaped cone hole micronozzle to be manufactured; 12-1. positioning platform; 12-2. inner diameter wall; 12-3. outer diameter wall; D1. diameter of blind hole; h1. thickness of conductive layer; h2. thickness of electrical insulating layer; h3. preset thickness; D. outer diameter of metal trumpet-shaped cone hole micronozzle to be manufactured; d. inner diameter of metal trumpet-shaped cone hole micronozzle to be manufactured; h. thickness of metal trumpet-shaped cone hole micronozzle to be manufactured. DETAILED DESCRIPTION

[0035] The following combination Figures 3 to 8 , the specific implementation method of the present invention - "a core mold and method for electroforming for manufacturing a metal trumpet-shaped conical hole micronozzle" is further described in detail.

[0036] A core mold for electroforming of a metal trumpet-shaped tapered micro-nozzle, comprising a substrate 5, a conductive layer 6 and an electrical insulating layer 7 tightly adhered to the upper surface of the substrate 5, and an array of blind holes 8 penetrating the conductive layer 6 and the electrical insulating layer 7; the bottom of the blind hole 8 is the upper surface of the substrate 5, such as Figure 3 and Figure 4 shown.

[0037] In this case, the outer diameter D of the metal trumpet-shaped conical hole micronozzle 12 to be manufactured is 800 μm, the inner diameter d of the metal trumpet-shaped conical hole micronozzle 12 to be manufactured is 100 μm, the thickness h of the metal trumpet-shaped conical hole micronozzle 12 to be manufactured is 200 μm, and the material is nickel.

[0038] According to the size of the metal trumpet-shaped conical hole micro-nozzle 12 to be manufactured, the design dimensions are determined as follows: the thickness h1 of the conductive layer 6 is 20 μm; the thickness h2 of the electrical insulating layer 7 is 500 μm; the hole spacing of the blind hole 8 is 3 mm; and the diameter D1 of the blind hole is 800 μm.

[0039] The preparation process of core mold 9 is as follows:

[0040] (1) In this case, a silicon wafer with a thickness of 2 mm is used as substrate 5. A 50 nm metal seed layer is sputtered on the surface of substrate 5. Copper is electroplated on the surface of the metal seed layer. The copper plating layer and the metal seed layer serve as conductive layer 6 until the thickness h1 of conductive layer 6 reaches 20 μm. Electroplating is then completed.

[0041] (2) Cover the surface of the conductive layer 6 with an electrical insulating layer 7. In this case, photoresist is used as the electrical insulating layer 7.

[0042] (3) Ion etching is performed to process the blind hole 8 until it stops at the upper surface of the substrate 5. At this point, the core mold 9 is obtained.

[0043] A method for manufacturing a metal trumpet-shaped tapered hole micro-nozzle, comprising the following steps:

[0044] (a) Place the core mold 9 as the cathode in the nickel sulfamate electroforming solution for electroforming at a current density of 2A / dm 2 ;

[0045] (b) When the thickness of the electroformed metal layer 10 reaches a preset thickness h3 (h3=h1+D / 2-d / 2=370μm), the electroforming is stopped and the core mold 9 is removed. Figure 5 As shown;

[0046] (c) After cleaning and drying the core mold 9 with the electroformed metal layer 10, the core mold 9 is thinned and leveled using an ultra-precision machining device 11 until the thickness of the electroformed metal layer 10 reaches the thickness h of the metal trumpet-shaped tapered micro-nozzle 12 to be manufactured. At this point, the thickness of the electroformed metal layer 10 (200 μm) is greater than the thickness h1 of the conductive layer 6 (20 μm). Figure 6 As shown;

[0047] (d) If Figures 7 and 8 After separating the electrical insulation 7 and conductive layer 6 from the substrate 5, the electrical insulation 7 is dissolved and the conductive layer 6 is removed, resulting in a metal trumpet-shaped tapered micronozzle 12 having a smooth trumpet-shaped inner diameter wall 12-2 and a straight outer diameter wall 12-3. The outer diameter D, inner diameter d, and thickness h of the metal trumpet-shaped tapered micronozzle 12 are 800 μm, 100 μm, and 200 μm, respectively.

[0048] After being thinned and leveled, the electroformed metal layer 10 forms a positioning platform 12-1, which is used for positioning when installing the metal trumpet-shaped conical hole micro-nozzle (12).

[0049] The above description illustrates the technical field, main technical features, technical problems solved, beneficial effects, and specific embodiments of the present invention. The present invention is not limited by the specific drawings or specific embodiments. Various changes, improvements, and extensions are possible without departing from the spirit and scope of the present invention. Such changes, improvements, and extensions fall within the scope of the present invention as claimed, which is defined by the appended claims and their equivalents.

Claims

1. A core mold for electroforming for manufacturing a metal trumpet-shaped tapered micro-nozzle, characterized by: It comprises a substrate (5), a conductive layer (6) and an electrical insulating layer (7) which are tightly attached to the upper surface of the substrate (5) in sequence, and regularly arranged blind holes (8) which penetrate the conductive layer (6) and the electrical insulating layer (7); the substrate (5) is an electrical insulating material; the bottom of the blind hole (8) is the upper surface of the substrate (5); the diameter D1 of the blind hole (8) is less than 2 times the thickness h2 of the electrical insulating layer (7); the hole spacing of the blind hole (8) is greater than 3D1; the diameter D1 of the blind hole (8) is greater than 10 μm and less than 1000 μm; the diameter D1 of the blind hole is equal to the outer diameter D of the metal trumpet-shaped cone-hole micro-nozzle to be manufactured.

2. The electroforming core mold for manufacturing a metal trumpet-shaped tapered hole micro-nozzle according to claim 1, characterized in that: The thickness of the substrate (5) is 1-3 mm.

3. The electroforming core mold for manufacturing a metal trumpet-shaped tapered hole micro-nozzle according to claim 1, characterized in that: The thickness h1 of the conductive layer (6) is greater than 10 μm.

4. The electroforming core mold for manufacturing a metal trumpet-shaped tapered hole micro-nozzle according to claim 1, characterized in that: The thickness h2 of the electrical insulation layer (7) is greater than or equal to the thickness h1 of the conductive layer (6).

5. A method for manufacturing a metal trumpet-shaped tapered hole micro-nozzle, characterized in that: The following steps are involved: (a) placing the core mold (9) according to any one of claims 1 to 4 as a cathode into an electroforming liquid for electroforming; (b) when the thickness of the electroformed metal layer (10) reaches a preset thickness h3, the electroforming is stopped and the core mold (9) with the electroformed metal layer (10) is removed; (c) After the core mold (9) with the electroformed metal layer (10) is cleaned and dried, the electrical insulating layer (7) on the core mold (9) is thinned and leveled using an ultra-precision processing device (11) until the thickness of the electroformed metal layer (10) is thinned to the thickness h of the metal trumpet-shaped tapered hole micro-nozzle (12) to be manufactured; (d) After separating the electrical insulating layer (7) and the conductive layer (6) from the substrate (5), the electrical insulating layer (7) and the conductive layer (6) are dissolved and removed, thereby obtaining a metal trumpet-shaped conical hole micro-nozzle (12) with a thickness of h, an inner diameter of d, and an outer diameter of D.

6. The method for manufacturing a metal trumpet-shaped tapered hole micro-nozzle according to claim 5, characterized in that: The electroformed metal layer (10) forms a positioning platform (12-1) after being thinned and leveled.

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