A method for preventing circuit board explosion by drilling through broken electroplated metal leads

Abstract

This invention discloses a method for preventing the breakage of electroplated metal leads during drilling in circuit boards. The method includes: setting a solder mask window at the location of two drill holes on the back of the electroplated metal lead; the solder mask window is 3 mil larger on each side than the target hole and the solder bridge is ≥4 mil; employing progressive step-by-step drilling, dividing the secondary drilling into multiple stages, with the difference in drill bit diameter between adjacent stages controlled between 0.05-0.15 mm; after each stage, the hole wall quality is monitored in real time and the parameters for the next stage are adjusted; dynamically and collaboratively controlling the drill bit speed and feed rate, adjusting parameters in real time according to changes in circuit board material and drilling depth to maintain the cutting force within a preset range. This invention, through window pretreatment, micro-incremental step-by-step drilling, and closed-loop dynamic control, effectively avoids problems such as hole bursting, delamination, and fiber tearing during secondary drilling, significantly improving hole wall quality and product reliability. It is suitable for high-precision secondary drilling of circuit boards of various materials.

Description

Technical Field

[0001] This invention relates to the field of circuit board manufacturing technology, specifically a method for preventing the breakage of electrolytic leads in circuit boards. Background Technology

[0002] Against the backdrop of the rapid development of the electronics industry, circuit boards, as a key basic component of electronic devices, directly affect the performance and quality of electronic products through their manufacturing processes. As electronic products develop towards miniaturization, thinness, and high performance, the traditional secondary drilling process for circuit boards has revealed serious problems with hole bursts, manifested as defects such as cracks, delamination, and fiber tearing in the hole walls or openings, which endanger electrical connectivity and structural stability.

[0003] In existing technologies, stress concentration areas exist around the hole wall after primary drilling; differences in the thermal expansion coefficients of materials in multilayer circuit boards lead to uneven thermal deformation during drilling; and factors such as drill bit wear and unreasonable parameter settings can easily induce hole bursts. Therefore, developing an efficient and reliable secondary drilling hole burst improvement process has become an urgent need in the industry. Summary of the Invention

[0004] This invention provides a method for preventing circuit board breakage during metal lead drilling, which aims to eliminate material height differences in the secondary drilling area, disperse cutting stress, and dynamically optimize drilling parameters, thereby effectively suppressing the bursting phenomenon and improving hole wall quality and product reliability.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a method for preventing circuit board explosion by drilling through broken electroplated metal leads, comprising the following steps:

[0006] S1. Setting up a window: A solder resist window is set at the position of the second drilling hole on the back of the metal lead of the circuit board to be drilled a second time. The size of the solder resist window is larger than the single side of the target drilling hole by a first length value, and the width of the solder bridge formed by the solder resist window is not less than the second length value.

[0007] S2. Progressive step-by-step drilling: Secondary drilling is performed at the two drilling locations, and the secondary drilling process is divided into multiple stages. A drill bit of the corresponding diameter is selected for each stage. After each stage of drilling is completed, the current hole wall quality is detected in real time, and the drilling parameters for the next stage are adjusted according to the detection results.

[0008] S3. Dynamic Drilling Parameter Adjustment: During the secondary drilling process, the intelligent control system dynamically coordinates and controls the rotation speed and feed rate of the drill bit, and adjusts the rotation speed and / or feed rate in real time according to the changes in the circuit board material and the increase in drilling depth, so as to control the cutting force of the drill bit to be maintained within the preset range.

[0009] As a further description of the above technical solution:

[0010] In step S1, the weld shielding window is formed by pattern transfer and development process, and the alignment accuracy between its edge and the center of the target drill hole is within ±1mil. The first length value is 3mil and the second length value is 4mil.

[0011] As a further description of the above technical solution:

[0012] Before step S2, there is also a drill bit matching step: based on the material, thickness and drilling diameter of the circuit board, the corresponding drill bit type and geometric parameters are matched through big data analysis and simulation technology.

[0013] As a further description of the above technical solution:

[0014] In step S2, the number of stages is determined based on the thickness of the circuit board and the target drilling diameter, and the diameter difference of the drill bits selected in adjacent stages is controlled between 0.05mm and 0.15mm.

[0015] As a further description of the above technical solution:

[0016] In step S2, the drill bit is a nano-coated cemented carbide drill bit, and the circuit board is made of FR-4 or BT resin.

[0017] As a further description of the above technical solution:

[0018] The drill bit has a apex angle of 118° to 135° and a helix angle of 25° to 40°.

[0019] As a further description of the above technical solution:

[0020] In step S2, the pore wall quality is detected in real time by optical detection or ultrasonic detection to detect the cracking, delamination or fiber tearing of the pore wall.

[0021] As a further description of the above technical solution:

[0022] In step S2, the drilling parameter adjustment in the next stage includes adjusting the drill bit rotation speed, feed rate, or selecting the drill bit diameter for the next stage.

[0023] As a further description of the above technical solution:

[0024] In step S3, the rotational speed of the drill bit is controlled within the range of 9000 rpm to 13000 rpm, and the feed rate is controlled within the range of 0.06 mm / rpm to 0.12 mm / rpm.

[0025] In summary, due to the adoption of the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0026] This invention eliminates the height difference between the front and back sides of the secondary drilling area by opening a weld-proof window, reducing the impact stress concentration at the moment of drill bit contact and fundamentally reducing the risk of hole bursting. The progressive step drilling, combined with a small diameter increment of 0.05-0.15mm, disperses the cutting force across multiple small steps, avoiding hole wall tearing or delamination caused by a single large drilling depth. The hole wall quality is detected in real time and the parameters of the next stage are dynamically adjusted to form a closed-loop control, adapting to different circuit board materials and hole depth variations. The intelligent control system dynamically coordinates the rotation speed and feed rate, and can automatically fine-tune parameters according to changes in material hardness (such as alternating layers of FR-4 and BT resin) or chip removal difficulties caused by increased drilling depth, always keeping the cutting force within the optimal range. The nano-coated carbide drill bit and optimized geometric parameters further reduce friction, improve chip removal performance, extend tool life, and improve hole wall finish. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a flowchart of a method for drilling through broken metal leads to prevent circuit board explosion. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0030] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0031] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0032] In the description of the embodiments of the present invention, it should be noted that the terms "upper" and "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the present invention.

[0033] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection, an indirect connection through an intermediate medium, or a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0034] Example 1:

[0035] Please see Figure 1 This invention provides a technical solution: a method for preventing circuit board explosion by drilling through broken electroplated metal leads, comprising the following steps:

[0036] Taking an FR-4 material circuit board with a thickness of 2.0mm and a target hole diameter of 3.0mm as an example, the circuit board has been drilled once and needs to be drilled a second time on the back of the electroplated lead.

[0037] Step 1: Install windows

[0038] A pattern transfer process is employed, with a solder mask window designed at the location to be drilled a second time. The window size is 3 mil larger on each side than the target hole diameter (i.e., the window diameter is 3.0 mm + 2 × 3 mil ≈ 3.15 mm). After development, the width of the solder mask bridge is ensured to be 4.5 mil (meeting ≥ 4 mil). A high-precision exposure machine is used to control the alignment accuracy between the window edge and the drill hole center within ±1 mil. This window eliminates the height difference between the solder mask and the copper surface, ensuring uniform force distribution on the drill bit upon contact.

[0039] Step 2: Drill bit matching and progressive step drilling

[0040] Using a big data analysis system, the material (FR-4), plate thickness (2.0mm), and target hole diameter (3.0mm) were input, and a nano-coated carbide drill bit with a 130° apex angle and a 35° helix angle was matched. Following the principle of progressive step-by-step drilling, the drilling process was divided into 5 stages, with a drill bit diameter difference of 0.10mm between adjacent stages (within the range of 0.05-0.15mm). The specific sequence was: 2.6mm → 2.7mm → 2.8mm → 2.9mm → 3.0mm. In the initial stage, a 2.6mm drill bit was used. After drilling to a depth of 2.0mm, the drill bit was lifted, and an optical inspection system was used to scan the hole wall to confirm the absence of cracks or delamination. Subsequently, 2.7mm, 2.8mm, 2.9mm, and 3.0mm drill bits were used sequentially, and the hole wall quality was checked after each step. If tiny fibrous burrs were found in a step, the rotation speed of the next step was automatically reduced by 5%, and the feed rate was reduced by 0.01mm / revolution.

[0041] Step 3: Dynamic Drilling Parameter Adjustment and Dynamic Coordinated Control

[0042] During each drilling step, the intelligent control system collects real-time data on the spindle load current and vibration sensor signals. The system's preset cutting force threshold range is 80N-120N. Initial parameters: spindle speed 11000 rpm, feed rate 0.09 mm / rpm. When the drill bit penetrates the circuit board to a depth of 1.0 mm, due to increased chip removal resistance and rising load current, the system automatically reduces the spindle speed to 10500 rpm and the feed rate to 0.08 mm / rpm, lowering the cutting force to approximately 100N. When drilling reaches approximately 0.2 mm into the hole, to prevent bursting at the exit, the system further reduces the feed rate to 0.07 mm / rpm while maintaining a constant spindle speed. Through these dynamic adjustments, the cutting force is maintained between 90-115N throughout the entire process, resulting in a smooth, intact hole without bursting.

[0043] Specifically, the intelligent control system includes: a spindle drive module, a feed servo module, a sensor module (load current sensor, accelerometer, acoustic emission sensor), and a controller (with built-in fuzzy PID algorithm). The controller pre-stores reference cutting force curves for different materials (FR-4, BT resin, polyimide, etc.). During drilling, the sensors acquire signals at a 1kHz sampling rate, and the controller calculates the estimated cutting force in real time and compares it with a preset range. When the estimated value exceeds the range, the feed rate is adjusted first (in steps of 0.005mm / revolution). If the value still exceeds the limit after adjustment, the rotational speed is finely adjusted (in steps of 100 rpm). At the same time, the target range is corrected in segments according to the drilling depth (feedback from the encoder): shallow holes (<0.3 times the plate thickness) allow higher cutting forces, while deep holes (>0.7 times the plate thickness) reduce the cutting force range by 10% to prevent hole bursting at the exit.

[0044] Example 2:

[0045] Taking a 1.2mm thick BT resin multilayer board with a target hole diameter of 0.8mm as an example, the drill bit diameter difference between adjacent stages was set to 0.05mm, with the sequence: 0.65mm → 0.70mm → 0.75mm → 0.80mm. Based on the high hardness of BT resin, the intelligent control system set the base rotation speed to 12,500 rpm and the feed rate to 0.07mm / rpm. During drilling, when a drill bit wear signal (increased torque fluctuation) was detected, the system automatically increased the rotation speed by 200 rpm and decreased the feed rate by 0.005mm / rpm to compensate for the decrease in cutting force. Ultimately, all holes were drilled without bursting, and the hole wall roughness was less than 5μm.

[0046] Comparative example:

[0047] When drilling the same board material using the traditional secondary drilling method (no window opening, single hole enlargement of 0.5mm, constant speed and constant feed), the bursting rate is as high as 12%, and there are obvious delamination and fiber tearing on the hole wall.

[0048] The pore breakage rate using the method of this invention is less than 0.3%. The electroplated metal lead drilling method provided by this invention can be widely applied in the manufacturing process of high-density interconnect circuit boards for mobile phones, computers, automotive electronics, and communication equipment, and is especially suitable for applications requiring precision secondary drilling of electroplated metal leads. This method significantly reduces pore defects, improves product yield and reliability, and has extremely high industrial application value.

[0049] In summary, due to the adoption of the above technical solution, the method for preventing circuit board explosion by drilling through broken metal leads in this embodiment has the following advantages compared to the prior art:

[0050] This invention eliminates the height difference between the front and back sides of the secondary drilling area by opening a weld-proof window, reducing the impact stress concentration at the moment of drill bit contact and fundamentally reducing the risk of hole bursting. The progressive step drilling, combined with a small diameter increment of 0.05-0.15mm, disperses the cutting force across multiple small steps, avoiding hole wall tearing or delamination caused by a single large drilling depth. The hole wall quality is detected in real time and the parameters of the next stage are dynamically adjusted to form a closed-loop control, adapting to different circuit board materials and hole depth variations. The intelligent control system dynamically coordinates the rotation speed and feed rate, and can automatically fine-tune parameters according to changes in material hardness (such as alternating layers of FR-4 and BT resin) or chip removal difficulties caused by increased drilling depth, always keeping the cutting force within the optimal range. The nano-coated carbide drill bit and optimized geometric parameters further reduce friction, improve chip removal performance, extend tool life, and improve hole wall finish.

[0051] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preventing circuit board explosion by drilling through broken metal leads, characterized in that, Includes the following steps: S1. Setting up a window: A solder resist window is set at the second drilling position on the back of the gold wire of the circuit board to be drilled a second time. The size of the solder resist window is larger than the single side of the target drill hole by a first length value, and the width of the solder bridge formed by the solder resist window is not less than the second length value. S2. Progressive step-by-step drilling: Secondary drilling is performed at the two drilling locations, and the secondary drilling process is divided into multiple stages. A drill bit of a corresponding diameter is selected for each stage. After each stage of drilling is completed, the current hole wall quality is detected in real time, and the drilling parameters for the next stage are adjusted according to the detection results. S3. Dynamic Drilling Parameter Adjustment: During the secondary drilling process, the intelligent control system dynamically coordinates and controls the rotation speed and feed rate of the drill bit, and adjusts the rotation speed and / or feed rate in real time according to the changes in the circuit board material and the increase in drilling depth, so as to control the cutting force of the drill bit to be maintained within the preset range.

2. The method for drilling through broken electroplated leads to prevent circuit board explosion according to claim 1, characterized in that, In step S1, the weld shielding window is formed by pattern transfer and development process, and the alignment accuracy between its edge and the center of the target drill hole is within ±1mil. The first length value is 3mil and the second length value is 4mil.

3. The method for drilling through broken electroplated leads to prevent circuit board explosion according to claim 1, characterized in that, Before step S2, there is also a drill bit matching step, which includes matching the corresponding drill bit type and geometric parameters based on the material, thickness and drilling diameter of the circuit board through big data analysis and simulation technology.

4. The method for drilling through broken electroplated leads to prevent circuit board explosion according to claim 1, characterized in that, In step S2, the number of stages is determined based on the thickness of the circuit board and the target drilling diameter, and the diameter difference of the drill bits selected in adjacent stages is controlled between 0.05mm and 0.15mm.

5. The method for drilling through broken electroplated leads to prevent circuit board explosion according to claim 1, characterized in that, In step S2, the drill bit is a nano-coated cemented carbide drill bit, and the circuit board is made of FR-4 or BT resin.

6. The method for drilling through broken electroplated leads to prevent circuit board explosion according to claim 1, characterized in that, In step S2, the apex angle of the drill bit is 118° to 135°, and its helix angle is 25° to 40°.

7. The method for drilling through broken electroplated leads to prevent circuit board explosion according to claim 1, characterized in that, In step S2, the real-time detection process for pore wall quality involves using optical or ultrasonic detection methods to detect in real time the cracking, delamination, or fiber tearing of the pore wall.

8. The method for drilling through broken electroplated leads to prevent circuit board explosion according to claim 1, characterized in that, In step S2, the next stage of drilling parameter adjustment process includes adjusting the drill bit rotation speed, feed rate, or selecting the drill bit diameter for the next stage.

9. The method for drilling through broken electroplated leads to prevent circuit board explosion according to claim 1, characterized in that, The drill bit's rotational speed is controlled within the range of 9000 rpm to 13000 rpm, and its feed rate is controlled within the range of 0.06 mm / rpm to 0.12 mm / rpm.

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