Circuit board processing method for 3dB bridge mounting and circuit board

Abstract

The invention provides a circuit board processing method for 3dB bridge mounting and a circuit board. The circuit board processing method for 3dB bridge mounting comprises the following steps: carrying out lamination processing on a plurality of layers of substrates to obtain a circuit board semi-finished product; drilling the circuit board semi-finished product to form a to-be-plated-through hole region; carrying out metal immersion plating treatment on the circuit board semi-finished product after drilling so as to form a plated-through hole region in the to-be-plated-through hole region; performing outer-layer circuit forming processing on the circuit board semi-finished product to form a bonding pad area and an outer-layer circuit area; wherein the bonding pad region is electrically connected with the outer layer circuit region and the plated-through hole region respectively; carrying out rough milling treatment on the circuit board semi-finished product; performing UV laser fine trimming treatment on the circuit board semi-finished product after rough milling; and carrying out edge cleaning and finish milling treatment on the semi-finished circuit board subjected to UV laser finishing. According to the circuit board processing method for mounting the 3dB bridge, the use reliability of the 3dB bridge after the 3dB bridge is mounted on the circuit board is relatively good.

Description

Technical Field

[0001] This disclosure relates to the technical field of circuit boards, and in particular to a circuit board processing method and circuit board for 3dB bridge mounting. Background Technology

[0002] A 3dB bridge is a signal component that uses a specific internal transmission line structure to achieve signal power distribution and phase adjustment. 3dB bridges are widely used in mobile communication base stations, satellite communications, millimeter-wave systems, radio frequency circuits, test instruments, and medical equipment. 3dB bridges are mounted on circuit boards, as shown in the attached diagram in the manual. Figure 1 As shown. The circuit board is manufactured using circuit board processing methods.

[0003] The circuit board processing method of the related technology includes the following steps: S1, preparing a circuit board to be processed, wherein the circuit board to be processed includes multiple conductive metal layers and multiple dielectric layers, wherein the multiple conductive metal layers and multiple dielectric layers are sequentially overlapped; wherein the multiple dielectric layers include a microwave product layer and a digital product layer;

[0004] S2. Drill holes in the circuit board to be processed to connect the multilayer dielectric layers and the multilayer conductive metal layers; S3. Divide at least all the microwave product layers of the circuit board to be processed into multiple spaced dielectric units, wherein the microwave product layers of the multiple spaced dielectric units are not connected to each other and at least one digital product layer is connected; S4. Completely wrap the sides of the microwave product layers of the dielectric units with protective metal; S5. Electroplat conductive metal on the surface of the multiple dielectric units and etch a pre-set circuit pattern on the surface of the units; S6. Divide along the edges of the dielectric units to form independent sub-circuits, as in patent publication number CN112449494B.

[0005] However, since the circuit board undergoes drilling and splitting processes, burrs are easily retained around the pads and vias during these processes. When a 3dB bridge is mounted on the circuit board, these burrs can easily puncture the insulating coating, making the 3dB bridge more susceptible to damage. This results in poor reliability of the 3dB bridge after mounting on the circuit board. Summary of the Invention

[0006] The purpose of this disclosure is to overcome the shortcomings of the prior art and provide a circuit board processing method and circuit board for mounting a 3dB bridge, which improves the reliability of the 3dB bridge after mounting on the circuit board.

[0007] The purpose of this disclosure is achieved through the following technical solution:

[0008] A circuit board fabrication method for 3dB bridge mounting includes:

[0009] The multilayer substrate is laminated to obtain a semi-finished circuit board.

[0010] The circuit board semi-finished product is drilled to form a hole area to be metallized;

[0011] The semi-finished circuit board after drilling is subjected to metal plating treatment to form a metallized hole area in the area to be metallized.

[0012] The circuit board semi-finished product undergoes outer layer circuit forming processing to form a pad area and an outer layer circuit area; wherein, the pad area is electrically connected to the outer layer circuit area and the metallized via area respectively;

[0013] The circuit board semi-finished product is rough milled;

[0014] The semi-finished circuit board after rough milling is then subjected to UV laser finishing treatment.

[0015] The semi-finished circuit board after UV laser finishing is then subjected to edge clearing and final milling.

[0016] In one embodiment, the step of performing metal plating on the semi-finished circuit board after drilling to form a metallized hole area includes: performing copper plating on the semi-finished circuit board after drilling to form a thin copper hole area; and performing electroplating on the semi-finished circuit board after copper plating to form a thick copper hole area; wherein both the thin copper hole area and the thick copper hole area are the metallized hole areas.

[0017] In one embodiment, the step of forming the outer layer circuitry of the circuit board semi-finished product to form the pad area and the outer layer circuitry includes: performing a lamination process on the circuit board semi-finished product; performing an exposure process on the laminated circuit board semi-finished product; performing a development process on the exposed circuit board semi-finished product; and performing an etching process on the developed circuit board semi-finished product to form the pad area and the outer layer circuitry.

[0018] In one embodiment, after the step of forming the outer layer circuitry of the circuit board semi-finished product to form the pad area and the outer layer circuitry area, and before the step of rough milling the circuit board semi-finished product, the circuit board processing method for 3dB bridge mounting further includes: performing solder mask treatment on the circuit board semi-finished product after the outer layer circuitry is formed.

[0019] In one embodiment, the step of rough milling the circuit board semi-finished product specifically involves using a CNC machine to rough mill the circuit board semi-finished product.

[0020] In one embodiment, the step of performing UV laser finishing on the semi-finished circuit board after rough milling is specifically as follows: using a UV laser finishing device to perform UV laser finishing on the semi-finished circuit board after rough milling.

[0021] In one embodiment, after performing edge cleaning and final milling on the semi-finished circuit board after UV laser finishing, the circuit board processing method for 3dB bridge mounting further includes: performing micro-etching on the semi-finished circuit board; performing plasma cleaning on the micro-etched semi-finished circuit board; and performing surface treatment on the semi-finished circuit board.

[0022] In one embodiment, after the step of plasma cleaning treatment of the micro-etched circuit board semi-finished product and before the step of surface treatment of the circuit board semi-finished product, the circuit board processing method for 3dB bridge mounting further includes: mechanical finishing treatment of the circuit board semi-finished product.

[0023] In one embodiment, the step of mechanical finishing the circuit board semi-finished product specifically involves using finishing tools to perform mechanical finishing on the circuit board semi-finished product.

[0024] A circuit board is manufactured using the circuit board manufacturing method for 3dB bridge mounting described in any of the above embodiments.

[0025] Compared with the prior art, this disclosure has at least the following advantages:

[0026] 1. The circuit board processing method for 3dB bridge mounting disclosed herein firstly involves laminating a multilayer substrate, i.e., bonding the multilayer substrates together tightly with resin under high temperature and pressure to obtain a circuit board semi-finished product, thereby improving the structural stability of the circuit board semi-finished product and forming inner layer circuitry. Next, the circuit board semi-finished product is drilled to form metallized hole areas, which facilitates subsequent metal plating. Then, the drilled circuit board semi-finished product undergoes metal plating, i.e., metal plating is performed on the metallized hole areas and the surface of the circuit board semi-finished product, forming metallized hole areas and simultaneously forming a surface metal layer on the surface of the circuit board semi-finished product. The metallized hole areas are connected to the surface metal layer, and the metallized hole areas are used to achieve interlayer electrical interconnection, forming the conductive foundation of the circuit board. Finally, the circuit board semi-finished product undergoes outer layer circuitry forming, i.e., outer layer circuitry forming is performed on the surface metal layer to form pad areas and outer layers. The circuit area and pad area are electrically connected to the outer circuit area and the metallized hole area, respectively, to achieve electrical interconnection between the outer and inner circuit areas. Next, the semi-finished circuit board undergoes rough milling, where the forming edges are removed to allow for a certain machining allowance before the final dimensions are achieved. This allows for subsequent edge cleaning and final milling. After rough milling, the semi-finished circuit board undergoes UV laser finishing, where the edges of the pad area and the area around the metallized holes are removed to eliminate burrs generated during drilling, preparing for the subsequent 3dB bridge mounting. Finally, the UV laser-finished semi-finished circuit board undergoes edge cleaning and final milling, where the remaining machining allowance is removed to ensure the circuit board's dimensions meet processing requirements and to remove burrs generated during rough milling, facilitating the mounting of the 3dB bridge.

[0027] 2. Since the pad area is used for mounting and connecting with the 3dB bridge, and the metallized hole area is used to realize interlayer electrical interconnection of the semi-finished circuit board, the pad area is electrically connected to the outer layer circuit area and the metallized hole area respectively, so as to realize electrical interconnection between the outer layer circuit area and the inner layer circuit, thereby effectively realizing the electrical connection between the inner layer circuit, the 3dB bridge and the outer layer circuit area. In the circuit board processing method for mounting the 3dB bridge disclosed herein, before mounting the 3dB bridge on the pad area, UV laser finishing is used to remove the forming burrs generated during drilling, and edge clearing and final milling are performed. Used to remove burrs generated after rough milling, making it less likely for burrs to remain around the edges of the pad area and the area around the metallized holes on the circuit board. This solves the problem in the prior art where burrs are easily retained around the edges of the pads and the area around the vias on the circuit board. Therefore, when the 3dB bridge is used to mount on the circuit board, the insulating coating of the 3dB bridge is less likely to be punctured by burrs, thus avoiding the problem in the prior art where burrs easily puncture the insulating coating of the 3dB bridge. This makes the 3dB bridge less prone to damage, resulting in better reliability of the 3dB bridge after mounting on the circuit board. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this disclosure and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 The image shows a photograph of a 3dB bridge used in the background technology for mounting on a circuit board.

[0030] Figure 2 This is a flowchart illustrating a circuit board fabrication method for 3dB bridge mounting, according to one embodiment. Detailed Implementation

[0031] To facilitate understanding of this disclosure, a more complete description will be given below with reference to the accompanying drawings, which illustrate preferred embodiments of the present disclosure. However, this disclosure can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure.

[0032] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly attached to the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0033] 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 disclosure belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this disclosure. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0034] like Figure 2 As shown, one embodiment of the circuit board processing method for 3dB bridge mounting is used to process a circuit board for mounting with a 3dB bridge. Further, the circuit board processing method for 3dB bridge mounting includes some or all of the following steps:

[0035] S101, the multilayer substrate is laminated to obtain a semi-finished circuit board.

[0036] In this embodiment, the multilayer substrate is subjected to a lamination process, that is, the multilayer substrate is tightly bonded together with resin under high temperature and high pressure to obtain a circuit board semi-finished product, so that the circuit board semi-finished product has good structural stability and inner layer circuitry.

[0037] S103, Drill holes in the semi-finished circuit board to form a hole area to be metallized.

[0038] In this embodiment, the circuit board semi-finished product is drilled to form a hole area to be metallized, which is beneficial for subsequent metal plating.

[0039] S105, perform metal plating on the semi-finished circuit board after drilling to form a metallized hole area in the area to be metallized.

[0040] In this embodiment, the semi-finished circuit board after drilling is subjected to metal plating treatment, that is, the metal plating treatment is performed on the area to be metallized and the surface of the semi-finished circuit board, so that the area to be metallized becomes a metallized area, and at the same time, a surface metal layer is formed on the surface of the semi-finished circuit board. The metallized area is connected to the surface metal layer. The metallized area is used to realize the interlayer electrical interconnection of the semi-finished circuit board to form the conductive foundation of the circuit board.

[0041] S107 performs outer layer circuit forming processing on the semi-finished circuit board to form a pad area and an outer layer circuit area; wherein, the pad area is electrically connected to the outer layer circuit area and the metallized via area respectively.

[0042] In this embodiment, the circuit board semi-finished product undergoes outer layer circuit forming treatment, that is, the surface metal layer undergoes outer layer circuit forming treatment to form pad area and outer layer circuit area. The pad area is electrically connected to the outer layer circuit area and the metallized hole area respectively, so that the outer layer circuit area and the inner layer circuit can be electrically interconnected.

[0043] S109, rough milling is performed on the semi-finished circuit board.

[0044] In this embodiment, the circuit board semi-finished product is rough milled. The forming edge of the circuit board semi-finished product is removed by milling with a tool so that the circuit board semi-finished product retains a certain machining allowance from the final shape size, thereby controlling the machining allowance within a small range to facilitate the subsequent edge cleaning and final milling process.

[0045] S111, the semi-finished circuit board after rough milling is subjected to UV (ultraviolet) laser finishing treatment.

[0046] In this embodiment, the semi-finished circuit board after rough milling is subjected to UV laser finishing treatment. The forming burrs around the edges of the pad area and the metallized hole area are removed by the tool to eliminate the forming burrs generated during the drilling process, in preparation for the subsequent 3dB bridge mounting.

[0047] S113, perform edge cleaning and final milling on the semi-finished circuit board after UV laser finishing.

[0048] In this embodiment, the semi-finished circuit board after UV laser finishing is subjected to edge clearing and final milling. That is, the forming edge with a certain amount of machining allowance retained by rough milling is removed by a tool to ensure that the shape and size of the circuit board meet the processing requirements. At the same time, it can remove the forming burrs generated after rough milling, which is beneficial to completing the mounting process of the 3dB bridge.

[0049] The aforementioned circuit board processing method for 3dB bridge mounting first involves laminating a multilayer substrate, i.e., bonding the multilayer substrates together tightly with resin under high temperature and pressure to obtain a semi-finished circuit board. This process ensures good structural stability and forms inner layer circuitry. Next, the semi-finished circuit board is drilled to create metallization areas, facilitating subsequent metal plating. Then, metal plating is performed on the drilled semi-finished circuit board, applying metal to both the metallization areas and the surface of the semi-finished circuit board. This forms metallization areas in the areas to be metallized and a surface metal layer on the surface of the semi-finished circuit board. The metallized areas are connected to the surface metal layer, providing interlayer electrical interconnection and forming the conductive foundation of the circuit board. Finally, the semi-finished circuit board undergoes outer layer circuitry forming, i.e., the surface metal layer is formed to create pad areas and outer layer circuitry. The circuit board is first divided into two parts: the pad area and the metallized hole area. The pad area is electrically connected to the outer layer circuit area and the metallized hole area, respectively, to achieve electrical interconnection between the outer layer circuit area and the inner layer circuit. Then, the circuit board semi-finished product is rough milled. The forming edges of the circuit board semi-finished product are milled off with a tool to leave a certain machining allowance between the circuit board semi-finished product and the final shape size. This machining allowance is kept within a small range to facilitate the subsequent edge cleaning and final milling process. After rough milling, the circuit board semi-finished product is subjected to UV laser finishing treatment. The forming burrs around the edges of the pad area and the metallized hole area are removed with a tool to eliminate the forming burrs generated during the drilling process and prepare for the subsequent 3dB bridge mounting. After UV laser finishing, the circuit board semi-finished product is subjected to edge cleaning and final milling treatment. The forming edges with a certain machining allowance left by rough milling are milled off with a tool to ensure that the shape size of the circuit board meets the processing requirements. At the same time, it can remove the forming burrs generated after rough milling, which is beneficial to the 3dB bridge mounting process.

[0050] Since the pad area is used for mounting and connecting with the 3dB bridge, and the metallized via area is used to realize interlayer electrical interconnection of the semi-finished circuit board, the pad area is electrically connected to the outer layer circuit area and the metallized via area respectively, so as to realize electrical interconnection between the outer layer circuit area and the inner layer circuit, thereby effectively realizing the electrical connection between the inner layer circuit, the 3dB bridge and the outer layer circuit area. In the circuit board processing method for mounting the 3dB bridge disclosed herein, before mounting the 3dB bridge to the pad area, UV laser finishing is used to remove forming burrs generated during drilling, and edge clearing and final milling are also performed. The process removes the burrs generated after rough milling, making it less likely for burrs to remain around the edges of the pads and the metallized vias on the circuit board. This solves the problem in the prior art where burrs are easily retained around the edges of the pads and vias. Therefore, when the 3dB bridge is mounted on the circuit board, the insulating coating of the 3dB bridge is less likely to be punctured by burrs, thus avoiding the problem in the prior art where burrs easily puncture the insulating coating of the 3dB bridge. This makes the 3dB bridge less prone to damage, resulting in better reliability after the 3dB bridge is mounted on the circuit board.

[0051] In one embodiment, the step of performing metal plating on the drilled circuit board semi-finished product to form the metallized hole area includes: firstly, performing copper plating on the drilled circuit board semi-finished product to deposit a uniform conductive copper layer on the hole wall of the metallized hole area, forming a thin copper hole area, and simultaneously forming a surface thin copper layer on the surface of the circuit board semi-finished product. The thin copper hole area is connected to the surface thin copper layer, and the thin copper hole area is used to realize interlayer electrical interconnection of the circuit board semi-finished product; then, the copper plating process is performed on the circuit board semi-finished product... The semi-finished board undergoes electroplating to deposit a uniform conductive copper layer on the hole walls of the thin copper hole area, transforming it into a thick copper hole area. Simultaneously, a uniform conductive copper layer continues to be deposited on the outer wall of the surface thin copper layer, transforming it into a surface thick copper layer. This thickens the copper layers on the hole walls and board surface, improving the reliability of the circuit board. Both the thin copper hole area and the thick copper hole area are metallized hole areas, which are copper layer hole areas, and the surface metallized layer is the surface copper layer, effectively achieving reliable connections between the interlayer traces of the circuit board.

[0052] In one embodiment, the step of forming the outer layer circuitry area and the outer layer circuitry area by performing outer layer circuitry forming on the circuit board semi-finished product includes: firstly, performing a lamination process on the circuit board semi-finished product, that is, laminating a photosensitive dry film onto the surface copper layer; then, performing an exposure process on the laminated circuit board semi-finished product, that is, aligning and positioning the film with the circuit pattern printed on it with the surface copper layer, and irradiating the photosensitive dry film with ultraviolet light to trigger a photochemical reaction to achieve precise transfer of the circuit pattern, so that the light-exposed part of the photosensitive dry film is cured, while the unexposed part remains soluble, laying the foundation for subsequent development, etching and other processes. The foundation is established; then, the exposed circuit board semi-finished product is developed, and the unexposed areas of the photosensitive dry film are selectively removed by the developer, while the exposed and cured pattern is retained, so that the circuit structure such as circuits and pads are clearly visible on the circuit board semi-finished product, ensuring that subsequent etching only acts on the copper foil in non-circuit areas; the developed circuit board semi-finished product is etched, and the exposed copper foil is etched by an acidic solution (such as copper chloride), retaining only the pads and circuits covered by the photosensitive dry film, forming the pad area and the outer circuit area, which makes the circuit board more reliable in use.

[0053] In one embodiment, after the step of forming the outer layer circuitry of the circuit board semi-finished product to create the pad area and the outer layer circuitry area, and before the step of rough milling the circuit board semi-finished product, the circuit board processing method for 3dB bridge mounting further includes: applying a solder mask treatment to the circuit board semi-finished product after the outer layer circuitry has been formed. In this embodiment, applying a solder mask treatment to the circuit board semi-finished product after the outer layer circuitry has been formed is used to form a permanent insulating protective coating on the surface of the circuit board semi-finished product, which is used to prevent short circuits in non-soldering areas, protect the surface copper layer, and improve the reliability of the circuit board.

[0054] In one embodiment, the step of rough milling the semi-finished circuit board specifically involves using a CNC machine to perform rough milling on the semi-finished circuit board. In this embodiment, using a CNC machine to perform rough milling on the semi-finished circuit board involves milling off the forming edges of the semi-finished circuit board with a cutting tool, so that the semi-finished circuit board retains a certain machining allowance from the final external dimensions. This keeps the machining allowance within a small range, facilitating subsequent edge cleaning and final milling. This effectively avoids problems such as increased tool wear or decreased machining accuracy due to excessive cutting volume during edge cleaning and final milling, resulting in higher processing efficiency for the circuit board.

[0055] Furthermore, in one embodiment, the tool used for rough milling is a single-edged micro-end mill with a diameter of 0.5-0.8 mm and a new tool entry runout ≤3 μm; the spindle speed for rough milling is 120k-180k rpm, the feed rate is 80-160 mm / s, and the feed per tooth is 0.6-1.0 μm / tooth; the depth of cut for rough milling is 0.05-0.10 mm / step. In this embodiment, the new tool entry runout ≤3 μm reduces tool vibration and runout during cutting, ensuring a stable cutting path and resulting in high machining accuracy; simultaneously, the spindle speed of 120k-180k rpm for rough milling significantly increases the cutting speed, and the feed rate of 80-160 mm / s improves machining efficiency.

[0056] In one embodiment, the step of performing UV laser finishing on the rough-milled circuit board semi-finished product specifically involves: using a UV laser finishing device to perform UV laser finishing on the rough-milled circuit board semi-finished product. In this embodiment, the UV laser finishing device is used to perform UV laser finishing on the rough-milled circuit board semi-finished product. The tool removes the forming burrs around the edges of the pad area and the metallized hole area, eliminating forming burrs generated during drilling. This prepares the circuit board for subsequent 3dB bridge mounting, resulting in better reliability after the 3dB bridge is mounted on the circuit board.

[0057] Furthermore, in one embodiment, the UV laser-treated spot diameter is 15-25 μm, and the energy density is 0.6-1.2 J / cm². 2 The scanning speed is 200-600 mm / s. In this embodiment, the spot diameter of the UV laser during fine finishing is small, which can achieve fine finishing and removal of forming burrs around the edges of the pad area and the metallized hole area. At the same time, the low energy density can avoid thermal damage to the surrounding area, making the UV laser fine finishing process more convenient.

[0058] Furthermore, in one embodiment, the UV laser finishing process is performed 2-4 times. In this embodiment, the UV laser finishing process is performed 2-4 times, that is, the forming burrs around the edge of the pad area and the metallized hole area are repeatedly processed 2 to 4 times, thereby effectively ensuring that the burrs are removed cleanly, resulting in better reliability of the circuit board.

[0059] In one embodiment, after the UV laser-refined circuit board semi-finished product undergoes edge cleaning and final milling, the circuit board processing method for 3dB bridge mounting further includes: firstly, performing micro-etching on the circuit board semi-finished product to remove surface contaminants, oxide layers, and burrs remaining from the edge cleaning and final milling process, i.e., eliminating burrs and smoothing edges. Moreover, micro-etching can form a uniform micro-rough structure (such as honeycomb or granular) on the surface copper layer, increasing surface activity and specific surface area; then, performing plasma decontamination treatment on the micro-etched circuit board semi-finished product, using the physical bombardment and chemical activity of plasma to remove organic contaminants and polish the edges of the circuit board semi-finished product to remove appearance defects such as burrs, flash, and wire drawing, effectively optimizing the surface state of the circuit board semi-finished product, compensating for the limitations of micro-etching, and providing a surface with high cleanliness and activity for subsequent surface treatment; finally, performing surface treatment on the circuit board semi-finished product to form a protective film or functional coating on the exposed surface copper layer to prevent oxidation of the surface copper layer, thereby effectively ensuring the reliability of the circuit board.

[0060] In one embodiment, after the plasma cleaning treatment of the micro-etched circuit board semi-finished product and before the surface treatment of the circuit board semi-finished product, the circuit board processing method for 3dB bridge mounting further includes: mechanical finishing of the circuit board semi-finished product. In this embodiment, mechanical finishing of the circuit board semi-finished product involves mechanically brushing and polishing the forming burrs around the edges of the pad area and the metallized hole area to eliminate forming burrs generated during drilling, thereby improving the reliability of the 3dB bridge after mounting on the circuit board.

[0061] In one embodiment, the step of mechanically finishing the circuit board semi-finished product specifically involves using a finishing tool to mechanically finish the circuit board semi-finished product. In this embodiment, the finishing tool is an ultra-fine abrasive belt or a nylon brush, wherein the ultra-fine abrasive belt is an ultra-fine abrasive belt with an abrasive particle size of 1200 mesh or higher, such as a 1500 mesh abrasive belt; the nylon brush uses brush filaments with a fiber diameter not exceeding 0.1 mm.

[0062] Specifically, ultra-fine grinding belts are used to mechanically finish the circuit board semi-finished products. The abrasive particles of the ultra-fine grinding belts are finer, which can accurately remove micro burrs, copper shavings and resin flash left over from drilling. This avoids problems such as surface scratches or over-cutting caused by traditional coarse grinding, thus improving the surface quality of the circuit board semi-finished products.

[0063] Nylon brushes are used to mechanically finish the semi-finished circuit boards. The nylon brushes can selectively remove burrs around the edges of the pad area and the metallized hole area through precise pressure control. This is used to eliminate burrs generated during drilling, resulting in better reliability of the 3dB bridge after it is mounted on the circuit board.

[0064] Furthermore, in one embodiment, the step of rough milling the circuit board semi-finished product includes: firstly, performing a stacking clamping process on the circuit board semi-finished product, that is, using a combination of aluminum sheet and acrylic sheet to stack and clamp the circuit board semi-finished product, so that the aluminum sheet is on top of the circuit board semi-finished product and the acrylic sheet is on the bottom, so that the aluminum sheet, circuit board semi-finished product and acrylic sheet are stacked. The aluminum sheet provides uniform downward pressure due to its metal rigidity, ensuring that the circuit board semi-finished product is subjected to consistent force during rough milling, avoiding local warping or misalignment. The acrylic sheet uses the slight elasticity of the polymer material to buffer the rigid pressure of the aluminum sheet, avoiding problems such as indentation and circuit damage on the surface of the circuit board semi-finished product due to stress concentration. The aluminum sheet and acrylic sheet are used to achieve a combination of rigid support and flexible buffering, improving the stability of the stacked board clamping process. Then, the semi-finished circuit board is rough milled, and the forming edge of the semi-finished circuit board is milled off by a tool to leave a certain machining allowance between the semi-finished circuit board and the final shape size. This machining allowance is controlled within a small range to facilitate the subsequent edge cleaning and final milling process. At the same time, the aluminum sheet and acrylic sheet are used to clamp and fix the semi-finished circuit board, avoiding the problem of the semi-finished circuit board shaking during rough milling and effectively suppressing the generation of burrs. After that, the semi-finished circuit board is depaneled, and the aluminum sheet and acrylic sheet are removed from the semi-finished circuit board, so that the aluminum sheet and acrylic sheet can be reused and the production cost of the circuit board can be reduced.

[0065] Further, in one embodiment, the step of rough milling the circuit board semi-finished product using a CNC machine includes: firstly, performing a first climb milling process on the circuit board semi-finished product using a CNC machine. During climb milling, the cutting thickness of the tool entering the workpiece gradually decreases from its maximum, stabilizing the cutting force, reducing chatter of the CNC machine, obtaining higher surface finish (i.e., lower Ra value), and extending tool life. Climb milling is a milling method where the milling cutter rotation direction is the same as the workpiece feed direction. Then, performing a first combined process of circumferential cutting and deceleration through-hole cutting on the circuit board semi-finished product using a CNC machine. This involves performing a combined circumferential cutting and deceleration through-hole cutting in the half-hole area. The half-hole area refers to the edge area of ​​the hole, i.e., the edge of the pad area and the area around the metallized hole. Circumferential cutting means that the tool cuts along a circular path around the contour of the hole. Circumferential cutting ensures uniform surface quality of the hole wall and avoids tool marks that may occur with linear cutting. Deceleration through-hole cutting means that the feed rate is reduced when the tool passes through the edge or inside the hole. Deceleration improves cutting stability and protects the tool and the circuit board semi-finished product. In this embodiment, the cutting thickness is 0.5-3mm.

[0066] Furthermore, in one embodiment, the peripheral wall of the metallized hole area is provided with a first micro-lug and a second micro-lug, which are arranged opposite to each other. The first micro-lug is where the cutting tool begins cutting, and the second micro-lug is where the cutting tool ends cutting. This prevents complete separation of the cutting areas, effectively avoiding tearing and resulting in better structural stability of the circuit board semi-finished product. In this embodiment, the cross-sectional size of the first micro-lug is 0.2-0.3 mm, so that a very small connecting portion is reserved at the entrance of the circuit board semi-finished product to facilitate the start of cutting; the cross-sectional size of the second micro-lug is 0.2-0.3 mm, so that a very small connecting portion is reserved at the exit of the circuit board semi-finished product, which is beneficial for tool retraction, thereby improving the processing convenience of the tool.

[0067] Furthermore, in one embodiment, the step of performing edge clearing and final milling on the semi-finished circuit board after UV laser finishing specifically involves using a CNC machine to perform edge clearing and final milling on the semi-finished circuit board after UV laser finishing. In this embodiment, using a CNC machine to perform edge clearing and final milling on the semi-finished circuit board after UV laser finishing removes a certain amount of machining allowance retained during rough milling, ensuring that the external dimensions of the circuit board meet the processing requirements. Simultaneously, it removes the burrs generated after rough milling, which is beneficial for completing the mounting process of the 3dB bridge, resulting in better reliability of the 3dB bridge after mounting on the circuit board.

[0068] Furthermore, in one embodiment, the tool used for edge milling is a single-edged micro-milling cutter with a diameter of 0.5-0.8 mm and a new cutter entry runout ≤3 μm; the spindle speed for edge milling is 120k-180k rpm, the feed rate is 80-160 mm / s, and the feed per tooth is 0.6-1.0 μm / tooth; the depth of cut for edge milling is 0.05-0.10 mm / step. In this embodiment, the combination of a depth of cut of 0.05-0.10 mm / step and a feed per tooth of 0.6-1.0 μm / tooth in edge milling enables the removal of minute amounts of burrs, reduces cutting force and thermal impact, and results in a smaller surface roughness around the metallized hole area, thus making the copper layer around the metallized hole area smoother.

[0069] Furthermore, in one embodiment, the step of performing edge clearing and final milling on the semi-finished circuit board after UV laser finishing using a CNC machine includes: firstly, performing a second climb milling process on the semi-finished circuit board after UV laser finishing using a CNC machine. During climb milling, the cutting thickness of the tool entering the workpiece gradually decreases from its maximum, the cutting force is stabilized, which can reduce the chatter of the CNC machine, obtain higher surface machining accuracy (i.e., lower Ra value), and extend tool life. Climb milling is a milling method in which the milling cutter rotation direction is the same as the workpiece feed direction; then, performing a second combined process of circumferential feed and deceleration through-hole in the semi-hole area using a CNC machine. The combined processing of deceleration through-holes involves using a half-hole area, which refers to the edge region of the hole, i.e., the edge of the pad area and the area around the metallized hole. Circular cutting involves the tool cutting along a circular path around the hole's contour. Circular cutting ensures uniform surface quality of the hole wall and avoids tool marks that may occur with linear cutting. Deceleration through-holes involves reducing the feed rate when the tool passes the edge or inside the hole. Deceleration improves cutting stability and protects the tool and the semi-finished circuit board. Subsequently, CNC equipment is used to remove the ear loops from the semi-finished circuit board. The CNC equipment uses a tool to remove the first and second ear loops separately, achieving a smooth transition in the metallized hole area, reducing the risk of burr formation, and improving the reliability of the circuit board. In this embodiment, the cutting thickness is 0.5-1.5 mm.

[0070] Furthermore, in one embodiment, after the rough milling step of the circuit board semi-finished product, the circuit board processing method for 3dB bridge mounting further includes: firstly, performing a first dry treatment on the circuit board semi-finished product using a high-speed dry milling cutter to reduce frictional heat generation and avoid the waste liquid problem caused by the mixing of liquid medium and pollutants in traditional wet processing; then, performing a first strong mist suction treatment on the circuit board semi-finished product after the first dry treatment to strongly collect the oil mist (such as cutting oil mist), resin dust (such as circuit board grinding dust) and metal debris (such as copper foil cutting particles) generated in the first dry treatment, preventing pollutants from spreading into the workshop air. That is, using a high-speed dry milling cutter in conjunction with a side-suction mist suction hood to collect resin dust and copper chips, achieving chip removal treatment, reducing pollutant emissions, and improving the environmental quality of the workshop.

[0071] Furthermore, in one embodiment, after the step of edge cleaning and final milling of the circuit board semi-finished product after UV laser finishing, the circuit board processing method for 3dB bridge mounting further includes: firstly, performing a second dry treatment on the circuit board semi-finished product using a high-speed dry milling cutter to reduce frictional heat generation and avoid the waste liquid problem formed by the mixing of liquid medium and pollutants in traditional wet processing; then, performing a strong mist suction treatment on the circuit board semi-finished product after the second dry treatment to strongly collect the oil mist (such as cutting oil mist), resin dust (such as circuit board grinding dust) and metal debris (such as copper foil cutting particles) generated during the second dry treatment, preventing pollutants from spreading into the workshop air, that is, using a high-speed dry milling cutter in conjunction with a side-suction mist suction hood to collect resin dust and copper chips, achieving chip removal treatment, reducing pollutant emissions, and improving the environmental quality of the workshop.

[0072] Furthermore, in one embodiment, the step of micro-etching the circuit board semi-finished product specifically involves micro-etching the circuit board semi-finished product using a combination of sulfuric acid and persulfate. In this embodiment, persulfate (S2O82-) has strong oxidizing properties under acidic conditions, which can quickly etch the surface copper layer to form a uniform "peak-valley" structure, significantly increasing the contact area between the surface copper layer and the dry film, and improving the adhesion between the surface copper layer and the dry film; at the same time, sulfuric acid provides an acidic environment, which can dissolve the natural oxide layer on the surface copper layer, while persulfate simultaneously etches the fresh copper layer, ensuring no oxide layer residue, thoroughly cleaning the copper surface, and making the circuit board more reliable.

[0073] Furthermore, in one embodiment, the amount of copper removed by the micro-etching process, i.e., the thickness of the copper layer removed, is 0.3–0.6 μm, and the micro-etching time is less than 60 s. In this embodiment, the reaction rate of persulfate (S₂O₈²⁻) under acidic conditions is 0.005–0.01 μm / s, that is, the etching rate of the circuit board semi-finished product micro-etched by combining sulfuric acid and persulfate is 0.005–0.01 μm / s, which allows the persulfate to stably remove a copper layer thickness of 0.3–0.6 μm within 60 s, thereby effectively ensuring the amount of copper removed by the micro-etching process.

[0074] This disclosure also provides a circuit board, which is manufactured using the circuit board manufacturing method for 3dB bridge mounting of any of the above embodiments.

[0075] Compared with the prior art, this disclosure has at least the following advantages:

[0076] 1. The circuit board processing method for 3dB bridge mounting disclosed herein firstly involves laminating a multilayer substrate, i.e., bonding the multilayer substrates together tightly with resin under high temperature and pressure to obtain a circuit board semi-finished product, thereby improving the structural stability of the circuit board semi-finished product and forming inner layer circuitry. Next, the circuit board semi-finished product is drilled to form metallized hole areas, which facilitates subsequent metal plating. Then, the drilled circuit board semi-finished product undergoes metal plating, i.e., metal plating is performed on the metallized hole areas and the surface of the circuit board semi-finished product, forming metallized hole areas and simultaneously forming a surface metal layer on the surface of the circuit board semi-finished product. The metallized hole areas are connected to the surface metal layer, and the metallized hole areas are used to achieve interlayer electrical interconnection, forming the conductive foundation of the circuit board. Finally, the circuit board semi-finished product undergoes outer layer circuitry forming, i.e., outer layer circuitry forming is performed on the surface metal layer to form pad areas and outer layers. The circuit area and pad area are electrically connected to the outer circuit area and the metallized hole area, respectively, to achieve electrical interconnection between the outer and inner circuit areas. Next, the semi-finished circuit board undergoes rough milling, where the forming edges are removed to allow for a certain machining allowance before the final dimensions are achieved. This allows for subsequent edge cleaning and final milling. After rough milling, the semi-finished circuit board undergoes UV laser finishing, where the edges of the pad area and the area around the metallized holes are removed to eliminate burrs generated during drilling, preparing for the subsequent 3dB bridge mounting. Finally, the UV laser-finished semi-finished circuit board undergoes edge cleaning and final milling, where the remaining machining allowance is removed to ensure the circuit board's dimensions meet processing requirements and to remove burrs generated during rough milling, facilitating the mounting of the 3dB bridge.

[0077] 2. Since the pad area is used for mounting and connecting with the 3dB bridge, and the metallized hole area is used to realize interlayer electrical interconnection of the semi-finished circuit board, the pad area is electrically connected to the outer layer circuit area and the metallized hole area respectively, so as to realize electrical interconnection between the outer layer circuit area and the inner layer circuit, thereby effectively realizing the electrical connection between the inner layer circuit, the 3dB bridge and the outer layer circuit area. In the circuit board processing method for mounting the 3dB bridge disclosed herein, before mounting the 3dB bridge on the pad area, UV laser finishing is used to remove the forming burrs generated during drilling, and edge clearing and final milling are performed. Used to remove burrs generated after rough milling, making it less likely for burrs to remain around the edges of the pad area and the area around the metallized holes on the circuit board. This solves the problem in the prior art where burrs are easily retained around the edges of the pads and the area around the vias on the circuit board. Therefore, when the 3dB bridge is used to mount on the circuit board, the insulating coating of the 3dB bridge is less likely to be punctured by burrs, thus avoiding the problem in the prior art where burrs easily puncture the insulating coating of the 3dB bridge. This makes the 3dB bridge less prone to damage, resulting in better reliability of the 3dB bridge after mounting on the circuit board.

[0078] The embodiments described above are merely illustrative of several implementations of this disclosure, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the disclosed patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this disclosure, and these all fall within the protection scope of this disclosure. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A circuit board processing method for 3dB bridge mounting, characterized in that, include: The multilayer substrate is laminated to obtain a semi-finished circuit board. The circuit board semi-finished product is drilled to form a hole area to be metallized; The semi-finished circuit board after drilling is subjected to metal plating treatment to form a metallized hole area in the area to be metallized. The circuit board semi-finished product undergoes outer layer circuit forming processing to form a pad area and an outer layer circuit area; wherein, the pad area is electrically connected to the outer layer circuit area and the metallized via area respectively; The circuit board semi-finished product is rough milled; The semi-finished circuit board after rough milling is then subjected to UV laser finishing treatment. The semi-finished circuit board after UV laser finishing is then subjected to edge clearing and final milling.

2. The circuit board processing method for 3dB bridge mounting according to claim 1, characterized in that, The step of performing metal plating on the semi-finished circuit board after drilling to form a metallized hole area includes: The semi-finished circuit board after drilling is subjected to copper plating treatment to form a thin copper hole area in the area to be metallized. The circuit board semi-finished product after copper plating is subjected to electroplating treatment to form a thick copper hole area from the thin copper hole area; wherein, both the thin copper hole area and the thick copper hole area are metallized hole areas.

3. The circuit board processing method for 3dB bridge mounting according to claim 1, characterized in that, The steps of forming the outer layer circuitry area and the outer layer circuitry area of ​​the circuit board semi-finished product include: The circuit board semi-finished product is subjected to a lamination process; The laminated circuit board semi-finished product is then exposed to light. The exposed circuit board semi-finished product is then subjected to a developing process; The developed circuit board semi-finished product is etched to form the solder pad area and the outer layer circuit area.

4. The circuit board processing method for 3dB bridge mounting according to claim 1, characterized in that, After the step of forming the outer layer circuitry of the semi-finished circuit board to create the pad area and the outer layer circuitry area, and before the step of rough milling the semi-finished circuit board, the circuit board processing method for 3dB bridge mounting further includes: The circuit board semi-finished product after the outer layer circuitry is formed is subjected to solder mask treatment.

5. The circuit board processing method for 3dB bridge mounting according to claim 1, characterized in that, The specific steps for rough milling the circuit board semi-finished product are as follows: The circuit board semi-finished product is rough milled using CNC equipment.

6. The circuit board processing method for 3dB bridge mounting according to claim 1, characterized in that, The specific steps for performing UV laser finishing on the semi-finished circuit board after rough milling are as follows: The semi-finished circuit board after rough milling is subjected to UV laser finishing treatment using UV laser finishing equipment.

7. The circuit board processing method for 3dB bridge mounting according to claim 1, characterized in that, After performing edge cleaning and final milling on the semi-finished circuit board after UV laser finishing, the circuit board processing method for 3dB bridge mounting further includes: The circuit board semi-finished product is subjected to micro-etching treatment; The micro-etched circuit board semi-finished product is then subjected to plasma cleaning treatment. The circuit board semi-finished product undergoes surface treatment.

8. The circuit board processing method for 3dB bridge mounting according to claim 7, characterized in that, After the plasma cleaning process on the micro-etched circuit board semi-finished product and before the surface treatment process on the circuit board semi-finished product, the circuit board processing method for 3dB bridge mounting further includes: The circuit board semi-finished product is subjected to mechanical finishing treatment.

9. The circuit board processing method for 3dB bridge mounting according to claim 8, characterized in that, The specific steps for mechanical finishing of the circuit board semi-finished product are as follows: The semi-finished circuit board is mechanically finished using precision finishing tools.

10. A circuit board, characterized in that, It is manufactured using the circuit board manufacturing method for 3dB bridge mounting as described in any one of claims 1 to 9.

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