A patch inductor electrode and a method of manufacturing the same

Abstract

The present application belongs to the field of inductive components, and discloses a patch inductor electrode and a preparation method thereof. The method comprises the following steps: S1, providing a pretreated whole-plate patch inductor with invalid process edges and a blank isolation area; S2, obtaining a whole-plate patch inductor with exposed electrode areas; S3, performing pre-metal deposition treatment on the electrode areas of the whole-plate patch inductor with exposed electrode areas; S4, performing copper electroplating treatment on the whole-plate patch inductor with pre-deposited metal; S5, segmenting the whole-plate patch inductor after copper electroplating treatment to obtain single inductors; and S6, performing coating insulation layer, electrode area windowing and nickel-tin plating treatment on the single inductors. The present application realizes multiple technical effects of greatly improving plating layer uniformity, optimizing batch consistency, improving mass production yield, and reducing production cost by adopting the process route of whole-plate substrate integral electroplating forming, synchronous and uniform deposition of multiple plating layers, and finally precise cutting forming.

Description

Technical Field

[0001] This invention belongs to the field of inductor components, specifically relating to a patch inductor electrode and its preparation method. Background Technology

[0002] As the core component of surface-mount power inductors, the quality of the electrode plating of surface-mount inductors directly affects the solderability, conductivity, and long-term reliability of the product. Currently, the industry-standard electrode plating process for surface-mount inductors is single-piece barrel plating, with a typical flow as follows: First, the entire board of electrodes is patterned. Then, the board is divided into individual products, which are then sequentially coated with a spray coating, silvered, barrel-plated with copper, and barrel-plated with nickel and tin. During this barrel plating process, each product is mixed with a certain proportion of steel balls and placed together in a basket-shaped drum of a barrel plating tank for electroplating. Current conduction is achieved through random and intermittent physical contact between the steel balls and the product surface, thereby gradually thickening the functional plating layers (copper, nickel, and tin layers) in the electrode area.

[0003] Currently, the industry generally accepts the technical route of "cutting and shaping first, then electroplating in segments". The conventional understanding is that pre-dividing the whole board into independent single electrodes before electroplating can effectively avoid the problems of uneven current density distribution and excessive difference in plating thickness within the board surface caused by edge effect when directly electroplating the whole board. Based on this understanding, this process has long been regarded as a standardized solution to ensure the plating quality of chip inductor electrodes. However, as chip inductors develop towards miniaturization and high precision, the above-mentioned traditional barrel plating process has exposed several inherent and difficult-to-overcome technical defects in long-term production practice, which have become key pain points restricting the yield and consistency of products in the industry: (1) Cutting and shaping causes electroplating electric field distortion, resulting in local plating thickness out of control. After a single electrode is mechanically or laser-cut, a large number of independent sharp corner structures, side cross sections and micro-edges will be formed on its surface. According to the current distribution theory in the electrochemical deposition process, in the electroplating system, electric field lines tend to concentrate preferentially on the geometric tips, edges and protrusions of the workpiece, resulting in a significantly higher current density in these areas than in flat planar areas. The direct consequence is that the coating growth rate at the sides, corners and cross-sections of the electrode is too fast and the thickness is abnormally high, while the effective area of ​​the electrode plane, which is the main functional area, has a relatively low current density and the coating growth is too thin. This uneven thickness distribution phenomenon of "excessive thickness at the corners and insufficient thickness on the plane" further aggravates the uneven distribution of coating stress at the microscale, which can easily lead to secondary quality problems such as coating cracking and reduced adhesion, and seriously weaken the weldability and corrosion resistance of the electrode. (2) The consistency of individual electroplated products is extremely poor, and the batch yield has been low for a long time. The size of a single electrode is very small (usually at the millimeter level or even the sub-millimeter level), and the number of each batch is often tens of thousands to hundreds of thousands. In the barrel plating process, all individual products are placed in the drum with steel balls and rely on random tumbling to achieve conductive contact. However, due to the structural characteristics and loading method of the barrel plating equipment, it is impossible to ensure that the placement posture of each electrode in the drum, the contact frequency with the steel balls, the spacing between adjacent products and the resistance value of the conductive path are completely consistent. Meanwhile, the electric field distribution inside the drum is greatly affected by the product stacking state, material layer thickness, and the distribution of the conductive medium (steel balls). The flow and exchange of electrolyte also vary significantly in different areas. These variables are further amplified in mass production, leading to significant deviations in key indicators such as coating thickness, microstructure density, and surface roughness between different individual electrodes within the same batch.

[0004] In summary, while the existing single-electrode electroplating process, which involves "cutting first and then barrel plating," has addressed the edge effect problem of whole-board electroplating to some extent, its inherent drawbacks of electric field distortion and poor consistency remain unresolved. Furthermore, for small-sized surface mount inductors with limited electrode area and small body dimensions, the plating efficiency of steel ball contact barrel plating is extremely low, resulting in severe capacity shortages during mass production. Adding equipment to increase capacity directly leads to a significant increase in site, labor, and energy costs. While barrel plating thickens the coating, it also tends to increase the electrode width simultaneously, affecting product dimensional consistency, making it particularly unsuitable for high-precision, small-linewidth surface mount inductor production. Therefore, a novel electrode plating processing method that can balance coating uniformity and batch consistency is urgently needed. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a patch inductor electrode and its preparation method. By adopting a process route of integral electroplating of a whole substrate, simultaneous and uniform deposition of multiple layers of plating, and finally precise cutting, multiple technical effects are achieved, including significantly improved plating uniformity, optimized batch consistency, improved mass production yield, and reduced production costs.

[0006] The objective of this invention is achieved through the following technical solution: This invention provides a method for fabricating a patch inductor electrode, comprising the following steps: S1, providing pre-processed full-board surface mount inductors, wherein the periphery of the full-board surface mount inductors is provided with an invalid process edge, and a blank isolation area is provided between adjacent inductors; S2, Photosensitive material is covered on the pre-treated whole-board patch inductor, and the electrode area is exposed by patterned exposure and development to obtain a whole-board patch inductor with exposed electrode area; S3, perform pre-plating metal treatment on the electrode area of ​​the whole-board chip inductor exposed in the electrode area to obtain a pre-plated metal whole-board chip inductor. S4, perform copper electroplating on the pre-plated metal surface mount inductor; S5, the whole board of chip inductors after copper plating is divided to obtain individual inductors; S6, the single inductor is coated with an insulating layer, the electrode area is windowed, and the windowed electrode area is plated with nickel-tin to obtain the final inductor electrode.

[0007] In some embodiments, in step S1, the pretreatment method is to grind the plated surface of the entire board of chip inductors to expose the conductive coil electrodes and then clean it with plasma.

[0008] In some embodiments, in step S1, the distance between the invalid process edge and the nearest inductor electrode is 4.8 mm to 6 mm.

[0009] In some embodiments, in step S1, the size of the blank isolation area is 0.15-0.2 mm.

[0010] In some embodiments, in step S2, the photosensitivity of the photosensitive material is 60-80 mJ / cm. 2 The coverage thickness of the photosensitive material is 60-120 μm; the linewidth resolution of the photosensitive material is 40-90 μm.

[0011] In some embodiments, in step S3, the pre-plated metal is at least one of nickel and copper.

[0012] In some embodiments, in step S3, the pre-plated metal is processed by at least one of electroless plating, electroplating, physical vapor deposition, chemical vapor deposition, and cold spraying.

[0013] In some embodiments, in step S3, the thickness of the pre-plated metal is 2-5 μm.

[0014] In some embodiments, in step S5, the segmentation is optimized by a precise alignment process, so that the cutting trajectory is strictly limited to the blank isolation area between each inductor.

[0015] The present invention also provides a patch inductor electrode, wherein the size of the patch inductor is 2.5×2.0×1.0 mm-1.4×1.2×0.8 mm; the thickness deviation of the plating on the electrode is ≤ ±2 μm; the surface thickness of the plating on the electrode is Ra ≦0.5 μm and Rz ≦2.5 μm.

[0016] Compared with the prior art, the beneficial technical effects of the present invention are as follows: This invention achieves multiple technical benefits by using a process route of integral electroplating of a whole substrate, simultaneous and uniform deposition of multiple layers of plating, and precise cutting. This process significantly improves the uniformity of the plating, optimizes batch consistency, increases mass production yield, and reduces production costs.

[0017] Other features and beneficial effects of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other beneficial effects of the invention can be realized and obtained by means of the structures particularly pointed out in the description, claims and drawings. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the full-board surface mount inductor in Example 1; Figure 2 This is an enlarged view of area A of the surface mount inductor in Example 1; Figure 3 The images show a comparison of the electrode coating structures in Example 1 and the comparative example using scanning electron microscopy. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to specific embodiments. These embodiments will enable those skilled in the art to gain a more comprehensive understanding of the invention, but do not limit the invention in any way. Where techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0021] In the description of this invention, it should be noted that all terms used in this invention (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains, and should not be construed as limiting the invention; it should be further understood that the terms used in this invention should be understood to have the same meaning as those in the context of this specification and in the relevant field, and should not be understood in an idealized or overly formal sense, except as expressly defined in this invention.

[0022] This invention provides a method for fabricating a patch inductor electrode, comprising the following steps: S1 provides a pre-processed full-board surface mount inductor, wherein the periphery of the full-board surface mount inductor is provided with an invalid process edge ( Figure 1 10), and a blank isolation area is provided between adjacent inductors ( Figure 2 30 in the middle). S2, a photosensitive material is coated onto the pre-treated whole-board patch inductor, and the electrode area is exposed through patterned exposure and development. Figure 2 (20) to obtain the whole-board surface mount inductor with exposed electrode areas; S3, perform pre-plating metal treatment on the electrode area of ​​the whole-board chip inductor exposed in the electrode area to obtain a pre-plated metal whole-board chip inductor. S4, perform copper electroplating on the pre-plated metal surface mount inductor; S5, the whole board of chip inductors after copper plating is divided to obtain individual inductors; S6, the single inductor is coated with an insulating layer, the electrode area is windowed, and the windowed electrode area is plated with nickel-tin to obtain the final inductor electrode.

[0023] For step S1, in this invention, the specific method of pretreatment is as follows: First, the surface to be plated on the entire chip inductor is ground (the thickness of the plating layer removed by grinding is controlled to be 12-18 μm, with a thickness tolerance of ±1.5 μm) to remove the surface oxide layer and contaminants, thereby exposing the electrode area of ​​the internal conductive coil; then, a plasma cleaning process is used to clean and activate the ground surface to remove residual organic contaminants and improve the surface energy, providing good interface bonding conditions for subsequent coating of photosensitive materials and patterning processing. The surface roughness of the entire chip inductor after grinding is Ra ≦0.5 μm; the plasma used is a mixture of nitrogen, carbon tetrafluoride, and oxygen to remove dust particles from the surface of the entire chip inductor.

[0024] Furthermore, in step S1, the distance between the invalid process edge and the nearest inductor electrode is 4.8 mm to 6 mm (not limited to 4.8 mm, 4.9 mm, 5.0 mm, 5.1 mm, 5.2 mm, 5.3 mm, 5.4 mm, 5.5 mm, 5.6 mm, 5.7 mm, 5.8 mm, 5.9 mm, 6 mm); the size of the blank isolation area is 0.15 to 0.2 mm (not limited to 0.15 mm, 0.16 mm, 0.17 mm, 0.18 mm, 0.19 mm, 0.2 mm).

[0025] It should be noted that, regarding the problem of uneven plating caused by electric field distortion in the edge region during the whole-plate electroplating process, this invention proposes a solution based on process layout optimization. The core of this solution lies in: arranging all effective electrode units in the uniform electric field region at the center of the substrate, separating them with blank isolation areas, while reserving ineffective process edges at the board edges. After the electroplating process is completed, the affected edge region is directly removed, retaining only the electrode array in the central region with a stable electric field and uniform plating. This approach completely avoids the interference of edge effects on electroplating quality from a structural design perspective, effectively solving the long-standing problem of controlling the uniformity of whole-plate electroplating in this field.

[0026] For step S2, in this invention, the photosensitive material is a photosensitive dry film or a liquid photosensitive emulsion. If a photosensitive film is used, the film is pressed to ensure effective adhesion of the photosensitive film to the surface to be coated. If a liquid photosensitive emulsion is used, the coated photosensitive emulsion is baked at a low temperature to achieve a pre-cured state, improving the accuracy of subsequent exposure and development. The photosensitivity of the photosensitive material is 60-80 mJ / cm. 2 The coverage thickness of the photosensitive material is 60-120 μm (not limited to 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, 105 μm, 110 μm, 115 μm, 120 μm); the linewidth resolution of the photosensitive material is 40-90 μm.

[0027] For step S3, in this invention, the pre-plated metal is at least one of nickel and copper. The pre-plated metal is processed by at least one of electroless plating, electroplating, physical vapor deposition, chemical vapor deposition, and cold spraying. The thickness of the pre-plated metal is 2-5 μm (not limited to 2 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm, 3.5 μm, 3.6 μm, 3.7 μm, 3.8 μm, 3.9 μm, 4 μm, 4.1 μm, 4.2 μm, 4.3 μm, 4.4 μm, 4.5 μm, 4.6 μm, 4.7 μm, 4.8 μm, 4.9 μm, 5 μm).

[0028] It is important to note that controlling the thickness of the pre-plated metal is crucial: if the pre-plated nickel layer is too thick (greater than 5 μm), it will compress the thickness space of the subsequent thickened copper and nickel-tin plating layers, causing the final total thickness to exceed the component assembly size requirements. Conversely, appropriately thinning the pre-plated nickel layer frees up more thickness margin for the deposition of functional thick copper layers, while also shortening electroplating time, which helps increase production capacity and reduce energy consumption. On the other hand, if the pre-plated layer is too thin (less than 2 μm), problems such as continuous film breakage, microporosity, and decreased plating uniformity are likely to occur, and there is even a risk of incomplete plating in localized areas, affecting subsequent adhesion and reliability. Therefore, the thickness of the pre-plated metal layer must be precisely controlled within a reasonable range, balancing dimensional accuracy, plating quality, and production efficiency.

[0029] In a preferred embodiment, the electrode areas of the surface-mount inductor are pre-plated with metal using a chemical plating method: First, the copper surface undergoes an ultra-clean pretreatment, including degreasing, water washing, micro-etching roughening, and PdCl2 palladium activation. Then, palladium is deposited on the copper (thickness 0.05±0.02 μm) through a displacement reaction between PdCl2 and copper. Next, a nickel plating step is performed, i.e., immersion in a Ni-containing solution. 2+ A chemical nickel plating solution containing sodium hypophosphite as a reducing agent, complexing agent, and stabilizer. The reaction occurs only on the catalytically active copper surface, where nickel atoms nucleate uniformly and grow layer by layer, achieving a thickness uniformity of ±5% across the entire plate. The micro-area exhibits atomic-level flatness, eliminating the current density unevenness problem found in electroplating processes. The typical nickel layer thickness is 2-5 μm, dense and pinhole-free, serving as an effective diffusion barrier layer between copper and subsequent tin layers.

[0030] The specific pre-plating metal treatment process is as follows: (1) Substrate loading and clamping The uncut copper-based electrode board (integrating multi-specification surface mount inductor electrode arrays such as 2016 / 2520) is horizontally suspended on a special planar electroplating fixture. The board surface is completely flat without bending or stacking. The conductive contacts of the fixture only contact the blank areas of the edge of the board, without occupying the effective electroplating area of ​​the electrodes, ensuring that there are no blind spots in the electric field distribution on the board surface, and ensuring uniform deposition of the subsequent full-area plating layer.

[0031] (2) Pretreatment 1) Hydrochloric acid immersion degreasing: The substrate is immersed in 2% dilute hydrochloric acid at room temperature for 90 seconds. The hydrochloric acid penetrates, wets, and has a weak corrosive effect to remove rolling oil stains, board release agents, and light oxide scale from the entire substrate surface. There is no strong alkaline electrolytic corrosion throughout the process, which avoids corrosion and deformation of the micro-electrode edges and corners.

[0032] 2) Two-stage countercurrent pure water washing: Spray washing removes residual hydrochloric acid solution from the plate surface and prevents cross-contamination of the solution in the next tank.

[0033] 3) Hydrochloric acid micro-etching activation: Immerse the electrode substrate in 2% dilute hydrochloric acid at room temperature for 60 seconds to slightly roughen the electrode substrate interface, thoroughly remove the dense oxide layer generated during substrate storage and transportation, optimize the interface bonding force, and do not change the dimensional accuracy of the electrode.

[0034] 4) Secondary pure water rinsing: No residual acidic solution or water stains on the board surface.

[0035] 5) PdCl2 palladium salt activation treatment: using palladium chloride activation solution, Pd... 2+The concentration is 5-25 mg / L (not limited to 5 mg / L, 6 mg / L, 7 mg / L, 8 mg / L, 9 mg / L, 10 mg / L, 11 mg / L, 12 mg / L, 13 mg / L, 14 mg / L, 15 mg / L, 16 mg / L, 17 mg / L, 18 mg / L, 19 mg / L, 20 mg / L, 21 mg / L, 22 mg / L, 23 mg / L, 24 mg / L, 25 mg / L), and the mass-to-area ratio of the palladium working solution to the effective area of ​​the whole-plate patch inductor electrode is 8-25 L / m². 2 (not limited to 8 L / m) 2 9L / m 2 10 L / m 2 11 L / m 2 12 L / m 2 13 L / m 2 14 L / m 2 15 L / m 2 16 L / m 2 17 L / m 2 18 L / m 2 19L / m 2 20 L / m 2 21 L / m 2 22 L / m 2 23 L / m 2 24 L / m 2 25 L / m 2 Immerse at 50-60℃ for 40-80 seconds to uniformly adsorb active palladium crystal nuclei on the substrate surface, providing catalytic active sites for subsequent electroless nickel plating and solving the problems of incomplete nickel plating in the insulation / passivation areas and incomplete plating.

[0036] 6) Final pure water rinse: Wash away free palladium ions from the plate surface to prevent palladium ions from being carried into the nickel plating bath and causing the bath solution to decompose and fail.

[0037] (3) Electroless nickel plating The entire surface of the substrate is immersed in a chemical nickel plating bath for electroless nickel plating. Ni in the electroless nickel plating solution... 2+ The concentration is 2.0-6.0 g / L (not limited to 2.0 g / L, 2.5 g / L, 3.0 g / L, 3.5 g / L, 4.0 g / L, 4.5 g / L, 5.0 g / L, 5.5 g / L, 6.0 g / L), the tank temperature is constant at 80-92℃, and the pH value is adjusted to 4.2-5.2. Under the catalytic action of palladium crystal nuclei, a uniform nickel base coating is simultaneously deposited on the entire electrode surface, which plays a role in blocking the diffusion of copper substrate, improving the adhesion of subsequent copper electroplating, and improving the corrosion resistance of the electrode. After nickel plating is completed, the electrode is rinsed with pure water in multiple stages for later use.

[0038] It should be noted that Pd 2+ When the concentration is below 5 mg / L, the palladium deposition rate is slow, the coating is thin, the coverage is incomplete, and it is easy to miss the coating; while when the concentration is above 25 mg / L, the palladium layer has coarse grains, high cost, and high coating stress, making it prone to peeling; this application prefers Pd. 2+ The concentration is 10–18 mg / L. The mass-to-area ratio of the palladium working solution to the effective area of ​​the entire chip inductor electrode is less than 8 L / m². 2 At times, palladium ions are rapidly consumed, resulting in large fluctuations in the bath concentration and uneven batch thickness; while concentrations above 25 L / m... 2 At that time, the maintenance cost of the bath solution was too high, and palladium salts were wasted; the preferred concentration in this application is 12-20 L / m 2 .

[0039] In a preferred embodiment, electrolytic flash nickel pre-plating (replacing chemical pre-plating nickel) is used: the patterned substrate is clamped at both sides of the ineffective process edges, and the cathode is connected through the pre-set conductive process points on the substrate. The substrate is then immersed in flash nickel electrolyte, with the nickel plate serving as the electrolytic anode. A short-time, high-current flash plating process is employed, rapidly depositing a thin nickel pre-plating layer only on the exposed conductive copper electrode surface. No metallic nickel is deposited in the insulating area covered by the photosensitive film, eliminating defects such as seepage and side etching that contaminate the pattern. The electrolytic nickel pre-plating layer serves as a transitional intermediate layer between the copper substrate and the subsequent electroplated copper layer, significantly improving the interfacial adhesion between multiple metal plating layers. Specifically, high-chlorination acidic electrolytic flash nickel pre-plating replaces chemical pre-plating nickel, with the following process parameters: nickel chloride 220-260 g / L, hydrochloric acid 120-160 mL / L, temperature 30-50℃, pH < 1.0, current density 3-8 A / dm², plating 30-90 s, plating thickness 2-5 μm, with no phosphorus precipitation and no blind hole overflow defects.

[0040] It should be noted that the method to ensure the quality stability of high-chlorination acidic electrolytic flash nickel pre-plating is to achieve precise management by establishing a dynamic reference table of current-time-thickness: under a fixed current density, the corresponding thickness increment standard is calibrated every 10 seconds, and the coating thickness is monitored by XRF every 2 hours. Once the measured value exceeds the target range of 2-5 μm, the electroplating time is immediately adjusted, thereby effectively preventing defects such as overflow caused by excessive thickness or poor interfacial adhesion caused by insufficient thickness. The advantages of this process are: significantly reduced hazardous waste and wastewater treatment costs, significantly reduced environmental compliance pressure; at the same time, the service life of the bath is longer, the frequency of downtime for bath replacement is reduced, and the overall production uptime is improved. It should be noted that it requires the initial configuration of rectifier, cathode moving and electrolysis equipment, with a one-time investment higher than that of chemical nickel plating; in addition, the uniformity of current density distribution must be strictly controlled during production to ensure coating consistency.

[0041] For step S4, in this invention, by electroplating the ineffective process edges, copper is electroplated onto the exposed electrode areas of the entire board through process points, achieving a uniform increase in plating thickness. Because the electroplating current distribution is uniform across the entire board, issues of plating thickness variation and width offset can be effectively avoided. The specific electroplating process is as follows: 1) Electroplating bath solution system: Acidic bright copper sulfate electroplating solution is used: Cu 2+ The concentration is 50-70 g / L, sulfuric acid is 180-220 g / L, and chloride ions are 50-80 ppm. It is combined with a leveling and brightening additive (at least one of sodium polydithiopropane sulfonate (SPS) accelerator and polyethyleneimine quaternary ammonium salt, preferably, the additive is a mixture of SPS accelerator and polyethyleneimine quaternary ammonium salt in a volume ratio of 2:1); the tank solution is equipped with a continuous filter and a constant temperature control device, and the temperature is stable at 22±2℃ throughout the process.

[0042] 2) Electroplating mode: The large plate is equipped with titanium mesh soluble copper anodes on both sides, and the anode and cathode are arranged in parallel and equidistantly. Pulsed DC electroplating is adopted with an average current density of 1.5-2.0 A / dm². All electrode units of the entire large plate receive a uniform electric field synchronously, and the copper layer is deposited synchronously throughout the entire area, without defects such as stacking of individual workpieces and uneven current distribution.

[0043] 3) Coating thickness control: Based on the high conductivity and high current carrying capacity requirements of high power surface mount inductor electrodes, the target thickness of the conductive copper layer is 15 μm-20 μm when deposited in one go; relying on the uniformity of the electric field of the whole board, the difference in copper layer thickness on the board surface is stably controlled within ±10%, and there is no need for multiple plating operations.

[0044] It should be noted that electroplating copper before dividing the entire inductor board not only improves the overall uniformity of the product, but also significantly improves the plating efficiency: for the same plating thickness, the processing time for a batch is reduced from about 8 hours to 30 minutes.

[0045] It should be noted that after step S4, the following may also be required: 1) Multi-stage pure water counter-current cleaning thoroughly removes copper sulfate plating solution from the board surface; 2) Weak acid neutralization and anti-oxidation immersion to prevent oxidation and discoloration of the nickel-copper composite plating; 3) Hot air drying at a low temperature of 60℃, the entire board retains its array structure without being disassembled.

[0046] It should be noted that, in an optional embodiment, after the entire plate electroplating (step S4) is completed, a whole-plate inspection operation can be further performed. This operation performs batch quality assessment on the plating thickness and its uniformity, which facilitates the early separation of defective products, controls quality from the source, and thus optimizes the overall manufacturing cost.

[0047] For step S5, in this invention, the segmentation is optimized through a precise alignment process, so that the cutting trajectory is strictly limited to the blank isolation area between each inductor.

[0048] For step S6, in this invention, an insulating layer is applied to each individual inductor, that is, the individual inductor is immersed in an insulating material, so that the outer surface of the individual inductor is covered with an insulating layer; a window is opened in the electrode area, that is, the electrode area is exposed to the insulating layer using a laser. The process of nickel-tin plating on the windowed electrode area is as follows: 1) Single-piece roller electroless nickel plating: using the same system of electroless nickel plating solution Ni 2+ (2.0-6.0 g / L), bath temperature 80-92℃, pH 4.2-5.2; barrel rotation speed 6-10 r / min, single barrel loading 8000-12000 pcs, tumbling nickel plating time 60-90 min, uniformly deposited nickel plating layer on electrode surface, nickel layer thickness 1-3 μm.

[0049] 2) Finished product barrel tin plating (outermost solderable plating layer): using a stannous sulfate acidic barrel tin plating system, Sn 2+ Concentration 18-25 g / L, sulfuric acid 160-200 g / L, brightener 15-25 ml / L, temperature 22±2℃, barrel plating current 20-40 A, barrel rotation speed 5-8 r / min; electroplating time 90-120 min, tin layer thickness 3-9 μm.

[0050] This invention also provides a patch inductor electrode, wherein the size of the patch inductor is 2.5×2.0×1.0 mm-1.4×1.2×0.8 mm; the thickness deviation of the plating on the electrode is ≤ ±2 μm; and the surface thickness of the plating on the electrode is Ra ≦0.5 μm and Rz ≦2.5 μm.

[0051] It should be noted that in high-reliability designs, the uniformity of electrode plating thickness and surface smoothness are crucial. Uneven plating thickness or rough surface not only increases contact resistance and affects high-frequency characteristics, but also leads to welding defects, severely weakening the long-term stability of electrical connections.

[0052] It should be noted that in the field of micro inductor electrode manufacturing, those skilled in the art have long held a deep-rooted technical understanding that "forming first and then electroplating" is a prerequisite for achieving high-quality plating, while generally holding a negative attitude towards whole-piece electroplating, believing that it inevitably faces the problem of uneven plating caused by the edge effect of the electric field. Therefore, this technical route has been shelved for a long time. This invention breaks the above-mentioned technical prejudice and creatively proposes a reverse process idea of ​​"first whole-piece electroplating, then precise cutting": first, the whole substrate is subjected to whole-piece electroplating operation, so that each layer of plating is deposited synchronously and uniformly in a stable electric field environment, and then the final electrode product is obtained through a precision cutting process. This invention organically integrates three dimensions: uniform distribution of electric field, controllable deposition process, and structural avoidance of uneven edge areas, and systematically solves the long-standing technical problem of uneven whole-piece electroplating. The specific principle is as follows: (1) Eliminate micro-edge current distortion and achieve uniform distribution of electric field throughout the whole area. The entire substrate is a regular and flat integrated planar structure, without the sharp corners, cross-sections, and irregular concave and convex structures after individual cutting. During the electroplating process, the electric field distribution on the cathode surface is continuous, uniform, and without abrupt changes, completely avoiding the inherent drawbacks of electroplating such as tip discharge and edge current accumulation. The overall surface current density of the substrate tends to be uniform, and the deposition rate of copper, nickel, and two metal coatings is uniform, eliminating the problem of thickness deviation between the corners and the planar coating of a single electrode from the source. This conforms to the core principle of electroplating uniformity and greatly improves the micro-uniformity of the coating. (2) Electroplating of the entire substrate achieves batch consistency. The entire plate can be electroplated synchronously in the entire array electrode area at one time. All electrode units are under the same electrolyte environment, electric field strength, temperature, and flow rate process conditions, and there are no contact differences or position differences between individual hanging. Compared with traditional single-electrode dispersed electroplating, it completely eliminates the coating parameter deviation within and between batches, and achieves a high degree of uniformity in coating thickness, density, and adhesion of all electrodes. (3) Cutting only separates the substrate without destroying the effective coating functional area. This case optimizes the precise alignment process, strictly limiting the cutting trajectory to the blank substrate isolation area between electrodes, and only cutting and separating the substrate connecting ribs that do not require plating, completely avoiding the plating structure of the effective conductive, welding, and inductive working areas of the electrodes. The cutting process only divides the substrate material and will not touch, wear, or tear the effective plating of the electrodes, thus completely solving the problem of no secondary damage after electroplating in traditional processes. (4) Simultaneous conformal deposition of multi-layer plating improves the overall plating quality. The conformal properties of electroplating on a flat substrate are far superior to those of irregularly shaped single workpieces. The copper bottom layer, nickel barrier layer, and tin surface layer can achieve atomic-level uniform deposition, with dense grains, no pinholes, no thickness difference, and excellent matching of multi-layer plating. In contrast, the irregular structure of the traditional pre-cut process will cause an imbalance in the deposition rate of multi-layer plating, resulting in defects such as uneven nickel layer barrier and poor flatness of the tin layer welding surface.

[0053] Example 1 This invention provides a method for fabricating a patch inductor electrode, comprising the following steps: S1, Smoothing the entire plated surface: The conductive plating surface of the substrate (with a 5 mm gap between the invalid process edge and the nearest inductor electrode) is precision ground using a mechanical polishing disc (Φ400 mm, #3000 grit diamond mechanical polishing disc, controlling the plating removal thickness to 15 μm with a thickness tolerance of ±1.5 μm) to completely expose the underlying conductive coil electrode. A ternary mixed gas of 80% oxygen, 10% nitrogen, and 10% carbon tetrafluoride is used for plasma bombardment cleaning to remove polishing copper powder, surface oxide film, and organic oil, ensuring a clean and impurity-free plating surface. After polishing, the surface roughness of the electrode substrate is controlled as follows: Ra ≤ 0.5 μm, Rz ≤ 2.5 μm. An invalid process edge is reserved at the substrate edge, with a 5 mm gap between the invalid process edge and the nearest inductor electrode edge. The size of the blank isolation area between adjacent inductor units is 0.15 mm. S2, Full-plate photosensitive film lamination: After leveling, the dry film on the plated surface is laminated with a photosensitive film. Key parameters of the photosensitive film: photosensitivity 80 mJ / cm². 2 The film layer has a thickness of 75 μm and possesses high-precision linewidth resolution. After lamination, it undergoes low-temperature baking: baking temperature 85℃, baking time 15 min, to bring the photosensitive film to a semi-pre-cured state, suppressing exposure halo diffusion and improving the dimensional accuracy of subsequent exposure and development patterns. Exposure and development: patterned exposure is performed using a parallel ultraviolet light source, with exposure energy matched to the photosensitive film's photosensitivity of 80 mJ / cm². 2 Using a 1wt% sodium carbonate aqueous solution for spraying and development, only the copper substrate of the electrode area to be electroplated is exposed, while the rest of the substrate is completely covered and insulated by the photosensitive film, achieving a precise graphic definition of the electrode area boundary with an accuracy of ±0.02 mm. S3, pre-plated nickel by electroless plating: Chemical nickel plating is performed on the exposed copper substrate area of ​​the electrode to form a uniform and dense thin nickel pre-plating layer, which blocks the oxidation of the copper substrate and improves the interfacial adhesion of the subsequent electroplated copper layer; specifically, Pd² + The concentration was 25 mg / L, and the mass-to-area ratio of the palladium working solution to the effective area of ​​the whole-board chip inductor electrode was 25 L / m²; the temperature-controlled immersion time was 80 s; the electroless nickel plating solution system was sodium hypophosphite type medium-temperature electroless nickel plating, the pH value of the plating solution was 5.0, the working temperature was 85℃, and the immersion reaction time was 12 min; the pre-plated nickel layer thickness was 2.5 μm, and the plating layer was free of pinholes and uniformly covered the surface of the bare copper electrode.

[0054] S4, copper plating thickened: The electroplating fixture holds the substrate along 5 mm wide ineffective process edges on both sides. Pre-set conductive process points on the substrate enable uniform conductivity across the entire board. Copper is simultaneously electroplated onto all exposed electrode areas, achieving uniform coating thickness. Key parameters of the acidic copper sulfate electroplating system are: 220 g / L copper sulfate, 90 g / L sulfuric acid, and 0.8 mL / L additive (a mixture of SPS accelerator and polyethyleneimine quaternary ammonium salt in a 2:1 volume ratio); current density 1.5 A / dm², electroplating time 30 min; final total copper plating thickness increase 15 μm; uniform current field distribution across the entire board; and electrode coating thickness variation within a single substrate ≤0.3 μm, effectively avoiding coating thickness differences and electrode pattern width offset issues.

[0055] S5, splitting into single particles: After the copper plating thickening is completed, the substrate is soaked in a 3 wt% sodium hydroxide solution to remove the photosensitive film, and then rinsed with pure water in multiple stages and dried with hot air at 100℃. A CNC precision cutting machine is used to cut the substrate along the preset dividing lines and split it into individual inductor semi-finished products with a size of 2.0×1.6×1.0 mm.

[0056] S6, spray coating, electrode windowing and nickel-tin plating final treatment: 1. Insulation coating spraying: Epoxy insulating paint is sprayed on the entire non-electrode area of ​​the single inductor core and the substrate. The coating thickness is 50 μm. It is baked at 120℃ for 30 min to fully cure, so as to achieve insulation and isolation. 2. Electrode windowing: Fiber laser point etching is used to precisely remove the insulating varnish in the electrode area. The deviation between the window outline and the inner electrode is ≤0.03 mm, fully exposing the pre-plated nickel + electroplated copper composite electrode substrate. 3. Final treatment of nickel-tin plating: First, pre-plat a barrier nickel layer (2 μm thickness, electrolytic nickel system, current density 2 A / dm³). 2 (Time 15 s), then electroplat a pure tin layer (thickness 8 μm, tin methanesulfonate system, temperature 25℃, current density 1 A / dm³). 2 (Electroplating time 18 min); finally forming a nickel barrier layer + tin outer layer composite electrode layer, the finished electrode has excellent acid and alkali corrosion resistance, high temperature oxidation resistance, and stable solderability.

[0057] Example 2 This invention provides a method for preparing a patch inductor electrode. Compared with Example 1, step S3 is electrolytic flash nickel pre-plating (replacing chemical pre-plating nickel): the patterned substrate is clamped along both sides of the ineffective process edges, and the cathode is connected through a pre-set conductive process point on the substrate. The substrate is then immersed in flash nickel electrolyte, with the nickel plate serving as the electrolytic anode. A short-time, high-current flash plating process is used to rapidly deposit a thin nickel pre-plating layer only on the exposed conductive copper electrode surface. No metallic nickel is deposited in the insulating area covered by the photosensitive film, eliminating defects such as seepage and side etching that contaminate the pattern. The electrolytic nickel pre-plating layer serves as a transitional intermediate layer between the copper substrate and the subsequent electroplated copper layer, significantly improving the interfacial bonding between multiple metal plating layers. Specifically, high-chlorination acidic electrolytic flash nickel pre-plating replaces chemical pre-plating nickel. The process parameters are: nickel chloride 260 g / L, hydrochloric acid 160 mL / L, temperature 50℃, pH < 1.0, and current density 6 A / dm³. 2 Electroplating for 90 seconds resulted in a coating thickness of 2.5 μm, with no phosphorus precipitation or blind hole over-plating defects. All other conditions were consistent.

[0058] Comparative example (traditional process) This invention provides a comparative example of a method for fabricating a patch inductor electrode. Compared to the embodiments, this method employs a traditional fabrication process, which involves first obtaining a single inductor electrode before performing subsequent plating operations. The specific steps are as follows: S1, Plated surface leveling: Diamond grinding is performed on the plated surface of the same batch of substrates as in the example to expose the conductive coil electrodes; plasma cleaning with a mixture of oxygen, nitrogen, and carbon tetrafluoride is used to ensure the cleanliness of the plated surface; the surface roughness of the grinding is Ra ≤0.5μm, Rz ≤2.5μm; the distance between the invalid process edge and the nearest inductor electrode is 5 mm; the size of the blank isolation area is 1.0 mm × 1.0 mm.

[0059] S2, Segmentation of individual inductors: Without performing full-board electroplating, the inductors are directly cut along the substrate dividing lines according to their individual dimensions to obtain independent bare blank inductor semi-finished products. The bare blank inductors are directly coated with epoxy insulation spraying with a coating thickness of 50μm and cured at 120℃ for 30 minutes. Fiber lasers are used to open windows one by one in the electrode areas of the individual inductors to expose the electrode parts to be plated.

[0060] S3, Single-cell copper plating thickening: All individual inductors in a batch are placed in a copper-plating basket, with conductive balls added simultaneously. Copper plating is thickened on the windowed electrode area of ​​each individual inductor. The concentrations are: copper sulfate 220 g / L, sulfuric acid 90 g / L, and additive (a mixture of SPS accelerator and polyethyleneimine quaternary ammonium salt at a volume ratio of 2:1) 0.8 ml / L; current density 1.1 A / dm³. 2The electroplating time is 360 min (current is transferred to the product through steel balls, the plated area is dynamically blocked, the contact resistance is high, only small electrodes of the product are plated and a low-stress thick copper layer is required, and the mass transfer and exhaust conditions inside the drum are poor; therefore, if the same copper plating thickness as in Example 1 is to be achieved, the high current and short time parameters of whole-board electroplating cannot be used, and the current density must be reduced to 1.1 A / dm). 2 The total thickness of the electroplated copper increased by 15 μm due to the cumulative plating thickness during the 360-minute ultra-long electroplating time. However, due to the uneven distribution of the individual electroplating current and the deviation of the steel balls and inductors in the copper rolling process, the electrodes are prone to poor plating thickness and poor electrode side width offset.

[0061] S4, Final treatment of single nickel-tin plated electrodes: For single inductor electrodes that have completed copper plating, electrolytic plating is first used to form a 3 μm barrier nickel layer. The electrolytic nickel system has a current density of 2 A / dm³. 2 Electroplating time 15 s; followed by electroplating of a 9 μm pure tin layer using a tin methanesulfonate system at 25°C and a current density of 1 A / dm³. 2 The electroplating process takes 18 minutes, ultimately forming a solderable and corrosion-resistant nickel-tin composite final electrode layer.

[0062] A comparative analysis was performed on the patch inductor electrode coatings obtained by the preparation methods used in Example 1 and the comparative example. The scanning electron microscope results are as follows: Figure 3 As shown in (a), the preparation method used in this application yields a whole electroplated coating free of pinholes and cracks, with uniform grain distribution, no peeling or uneven thickness defects, and excellent coating consistency, while traditional processes ( Figure 3 (b) The resulting coating exhibits uneven and distorted interfaces, large thickness variations, and internal pinholes, plating nodules, and interlayer microcracks. Traditional processes result in individual electrode coating thickness deviations ≥ ±8 μm and batch deviations ≥ ±12 μm; the preparation method used in this application yields individual electrode coating thickness deviations ≤ ±2 μm and overall batch deviations ≤ ±5 μm, improving uniformity by more than 3 times. The nickel, copper, and tin multilayer coating of the single inductor electrode obtained in this application shows compositional content fluctuations of ≤ ±1.5 wt%; while traditional processes show fluctuations of ±4~8 wt%.

[0063] Salt spray corrosion resistance results show that the salt spray corrosion resistance time of single electrodes obtained by this application is improved by more than 40% compared with the traditional preparation method. Salt spray test: Neutral salt spray test was conducted according to the current national standard GB / T 2423.17-2024 "Environmental Testing Part 2: Test Methods Test Ka: Salt Spray", with test conditions of 5% sodium chloride aqueous solution, solution pH value of 6.5-7.2, test chamber temperature of 35℃, and salt spray deposition of 1.0-2.0 mL / 80 cm. 2•h, using the appearance of peeling, rust, and coating corrosion on the electrodes as the failure criteria, and grouping equal-quantity sampling for comparative testing.

[0064] The peel test results show that the single electrode coating obtained by the preparation method used in this application is generally smooth, the deposited coating has uniform adhesion, no local stress concentration, and the peel test pass rate is 100%; while the traditional process has uneven stress in irregular areas of the coating, and the defect rate is as high as 8%-15%; Peel test: According to the national standard GB / T 5270-2022 "Test method for adhesion strength of electrodeposited and chemically deposited metal coatings on metal substrates", the cross-cut tape peel test is conducted. A cross-cut knife (square side length 1mm) is used, and 3M 600 special adhesion tape is used for vertical tearing and peeling. The coating is considered qualified if there is no peeling or flaking.

[0065] The single inductor electrodes obtained by the preparation method used in this application exhibit good consistency in both size and electrical performance across different batches. Specifically, for the same model electrode, the average difference in plating thickness between different production batches is ≤0.2 μm, while the batch difference using traditional processes is 0.6~1.2 μm. The dimensional tolerance of the electrode's external dimensions (length, width, and thickness) between batches in this application fluctuates within ±0.006 mm, while the electrode dimensions obtained using traditional processes are ±0.008~0.015 mm. The DC resistance of the inductor electrodes obtained in this application has a batch range of ≤5 mΩ, while that obtained using traditional processes is 15-30 mΩ. The solderability test results for the inductor electrodes obtained in this application (wetting balance method, applicable standards: IPC-TM-650 2.4.14, IEC 60068-2-69, GB / T 2423.32; test method: the sample is vertically immersed in molten SAC305 lead-free solder, solder temperature 245±3℃, immersion speed 1 mm / s, immersion depth 1-2 mm, residence time in the tank 5 s; wetting force-time curves are collected, and the criteria for solderability qualification are zero-crossing time ≤2s, 5s wetting force ≥2s wetting force ≥90%, and no wetting retraction throughout the process.) show that the batch wetting force fluctuation is ≤±8%, while that of traditional processes is over ±20%; in salt spray testing and solder thermal shock resistance testing, the batch failure sample dispersion rate of the inductor electrodes obtained in this application is ≤2%, while that of traditional processes is 8%~18%.

[0066] This invention, through a combination of whole-piece electroplating and precise cutting processes, can achieve a stable overall yield of over 91%, representing a significant improvement of at least 4 percentage points compared to traditional single-piece or slit electroplating processes (80%-87%). Simultaneously, various process defects are effectively suppressed, with uneven plating thickness reduced by over 85%, edge plating defects and localized plating deficiencies reduced by no less than 90%, electroplating warping and substrate deformation reduced by over 75%, and cutting burrs and plating delamination defects reduced by over 60%. This comprehensive improvement demonstrates a dual enhancement in both yield and quality.

[0067] Furthermore, the preparation method used in this application was applied to the mainstream surface mount inductor electrodes of 2520, 2016, and 2012. Three batches of each specification were taken, and 1000 pieces of each batch were sampled for parallel testing to further verify the feasibility of the method. Specifically, in terms of electrode plating thickness control, traditional barrel plating (the method used in the comparative example) resulted in a relative deviation of ±28% to ±42% due to stacking and obstruction. However, using the method used in Example 1 of this invention, the electric field is uniformly distributed, and after XRF multi-point detection, the relative deviation of the thickness is stable at ±3% to ±9.2%, all meeting the index within ±10%. In terms of surface flatness, traditional barrel plating (comparative example) resulted in a welding surface Ra≥0.85μm and local protrusions of 3-8μm due to friction and impact. In this invention (Example 1), there is no collision or friction, and after precision cutting, the welding surface Ra≤0.25μm and the drop ≤0.6μm, reducing roughness by more than 70% and the unevenness drop by 90%, significantly improving the welding quality.

[0068] Production efficiency and overall costs are also significantly optimized. Traditional barrel plating (comparative example) takes approximately 120 minutes per batch and has an hourly capacity of approximately 4000 pcs / h, while the present invention (Example 1) electroplating a whole board takes only 12-20 minutes per batch, with a single board supporting 60,000-100,000 electrode units, achieving an hourly output of 20,000-40,000 pcs / h, increasing capacity by 5-10 times. Based on a daily capacity of 1 million pcs, the site occupancy is reduced from 220 m². 2 Reduced to 82 m 2 (62.7% reduction), manpower reduced from 16 to 6 (62.5% reduction), unit product energy consumption decreased by about 64%, the weighted average reduction of the three items was about 63%, and the overall cost was reduced by more than 60%.

[0069] Regarding the scrap rate of plating defects, the average scrap rate of the traditional process (comparative example) reached 11.2%, while that of the present invention (Example 1) was reduced to 1.9%, a reduction of 83.04%, exceeding 80%. At the same time, the process compatibility performance covers the entire series of 2520, 2016, 2012, and 1412 surface mount inductor electrodes, with a minimum linewidth of 0.08 mm and a slice tolerance of ±0.008 mm. All reliability tests, including thermal shock, salt spray, and solderability tests, have been passed, fully verifying the stable adaptability of this process to multi-specification, small-size, high-precision products.

[0070] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A method for fabricating a patch inductor electrode, characterized in that, Includes the following steps: S1, providing pre-processed full-board surface mount inductors, wherein the periphery of the full-board surface mount inductors is provided with an invalid process edge, and a blank isolation area is provided between adjacent inductors; S2, Photosensitive material is covered on the pre-treated whole-board patch inductor, and the electrode area is exposed by patterned exposure and development to obtain a whole-board patch inductor with exposed electrode area; S3, perform pre-plating metal treatment on the electrode area of ​​the whole-board chip inductor exposed in the electrode area to obtain a pre-plated metal whole-board chip inductor. S4, perform copper electroplating on the pre-plated metal surface mount inductor; S5, the whole board of chip inductors after copper plating is divided to obtain individual inductors; S6, the single inductor is coated with an insulating layer, the electrode area is windowed, and the windowed electrode area is plated with nickel-tin to obtain the final inductor electrode.

2. The preparation method according to claim 1, characterized in that, In step S1, the pretreatment method is to grind the plated surface of the entire board of chip inductors to expose the conductive coil electrodes, and then clean it with plasma.

3. The preparation method according to claim 1, characterized in that, In step S1, the distance between the invalid process edge and the nearest inductor electrode is 4.8 mm to 6 mm.

4. The preparation method according to claim 1, characterized in that, In step S1, the size of the blank isolation area is 0.15-0.2 mm.

5. The preparation method according to claim 1, characterized in that, In step S2, the photosensitivity of the photosensitive material is 60-80 mJ / cm. 2 The coverage thickness of the photosensitive material is 60-120 μm; the linewidth resolution of the photosensitive material is 40-90 μm.

6. The preparation method according to claim 1, characterized in that, In step S3, the pre-plated metal is at least one of nickel and copper.

7. The preparation method according to claim 1, characterized in that, In step S3, the pre-plated metal is processed by at least one of electroless plating, electroplating, physical vapor deposition, chemical vapor deposition, and cold spraying.

8. The preparation method according to claim 1, characterized in that, In step S3, the thickness of the pre-plated metal is 2-5 μm.

9. The preparation method according to claim 1, characterized in that, In step S5, the segmentation is optimized through a precise alignment process, so that the cutting trajectory is strictly limited to the blank isolation area between each inductor.

10. The patch inductor electrode prepared by the preparation method according to any one of claims 1-9, characterized in that, The dimensions of the surface mount inductor are 2.5×2.0×1.0 mm to 1.4×1.2×0.8 mm; the thickness deviation of the plating on the electrode is ≤ ±2μm; the surface thickness of the plating on the electrode is Ra ≦0.5 μm and Rz ≦2.5 μm.

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