Defect repair process of fine circuit board

Abstract

The invention relates to the technical field of integrated circuits, in particular to a defect repair process of a fine circuit board, which comprises the following steps of: A, carrying out surface treatment on the fine circuit board; b, determining a defect area according to the open circuit position of the fine circuit board after surface treatment; c, placing the metal microfilament right above the defect area, and forming an included angle between the metal microfilament and the defect area; d, respectively electrifying the fixed ends of the metal microwires and the fine circuit board subjected to surface treatment to generate potential difference; and E, under the protection of inert gas, enabling the free end of the metal microwire to periodically vibrate up and down in a reciprocating manner and translate along the length direction of the defect area until metal liquid drops formed by melting the free end of the metal microwire due to periodic pulse discharge are deposited and cover the surface of the defect area. According to the defect repairing process of the fine circuit board, on the premise that the repairing precision is improved and thermal damage is reduced, the electrical conductivity and the durability of the repairing effect are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of integrated circuits, and in particular to a defect repair process for a fine circuit board. Background Art

[0002] A fine circuit board refers to a high-density interconnected circuit board made of fine conductive lines with a line width / line spacing of ≤50μm. It has the advantages of high integration, high-frequency and high-speed performance, lightweight and flexibility, and is widely used in consumer electronics, semiconductor packaging, automotive electronics, medical equipment and other fields.

[0003] Fine circuit boards are typically manufactured through precise photolithography, etching, and electroplating processes. However, during the manufacturing process, defects such as open circuits can occur in the fine lines of fine circuit boards due to factors such as photolithography deviations, uneven electroplating, or mechanical stress. These defects not only significantly reduce product yield, reliability, and lifespan, but in high-end applications (such as chip packaging), these defects can render the entire module useless, resulting in significant financial losses.

[0004] In order to overcome the above-mentioned defects, the existing technology uses the following processes to repair fine circuit boards: (1) Metal paste sintering method, printing metal paste on the defective area of the fine circuit board, and then repairing it after sintering. However, during the sintering process, it is difficult for the metal paste to be completely melted, resulting in unmelted metal particles easily remaining at the interface between the repair area and the fine circuit board, making the interface bonding strength between the repair area and the fine circuit board insufficient, and the interface peeling phenomenon is easy to occur during use, and the durability of the repair effect is poor; at the same time, the insufficient interface bonding strength is easy to cause pores at the interface between the repair area and the fine circuit board, thereby increasing the interface contact resistance and affecting the conductivity of the repair area. In addition, when unmelted metal particles remain inside the repair area, it is easy to cause high resistance points inside the repair area, thereby increasing the resistance of the repair area, which also affects the conductivity of the repair area. In addition, during the sintering process, due to the easy generation of high temperatures, the fine circuit board is prone to thermal deformation, thereby causing thermal damage. Furthermore, the accuracy of metal paste printing is poor, resulting in poor repair accuracy. (2) Metal ion reduction method: negative electricity is applied to the fine circuit board, and the fine circuit board after being energized is immersed in a metal salt solution. A positive potential is applied to the metal probe, so that a potential difference is formed between the metal probe and the fine circuit board; the potential difference is used to reduce the metal ions to metal particles and deposit them in the defect area to achieve the repair of the fine circuit board. However, the metal particles generated by reduction are only combined by intermolecular forces (such as van der Waals forces), lacking the strong interaction of metal bonds, resulting in insufficient internal density of the repair area and insufficient strength. When subjected to external force or thermal stress, the repair area is very easy to be damaged, and delamination and peeling may occur during use, which also makes the repair effect difficult to be long-lasting and effective. In addition, the insufficient density of the repair area is easy to induce closed pores, destroying the continuity of the conductive path, forming a local high resistance area, and ultimately leading to poor conductivity. In addition, since the entire fine circuit board is immersed in the metal salt solution, metal particles are also present in the non-defective area after repair, and the repair accuracy is poor. Furthermore, the process of reducing metal ions to metal particles is an exothermic reaction. Since the exothermic reaction continues for a short period of time, the heat generated is not easy to dissipate, which can easily cause thermal deformation of fine circuit boards and thus thermal damage.

[0005] In summary, existing repair processes generally have defects such as thermal damage, poor repair accuracy, poor conductivity and poor durability of repair effects. Summary of the Invention

[0006] The purpose of the present invention is to propose a defect repair process for fine circuit boards. By innovating the repair process, it is beneficial to improve the conductivity and durability of the repair effect while improving the repair accuracy and reducing thermal damage, so as to overcome the shortcomings of the existing technology.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] A defect repair process for a fine circuit board comprises the following steps:

[0009] A. Performing surface treatment on the fine circuit board to obtain a fine circuit board after surface treatment;

[0010] B. Determine the defective area based on the disconnection location of the fine circuit board after surface treatment;

[0011] C. placing a metal microwire directly above the defect area, such that an angle is formed between the metal microwire and the defect area;

[0012] D. The metal microwire includes a fixed end and a free end. The fixed end of the metal microwire is electrified to make the metal microwire negatively charged. The surface-treated fine circuit board is electrified to make the surface-treated fine circuit board positively charged, thereby generating an electric potential difference between the surface-treated fine circuit board and the metal microwire.

[0013] E. Under an inert atmosphere, the free end of the metal microwire is made to vibrate periodically up and down directly above the defect area. During the periodic up and down vibration, the free end of the metal microwire is translated along the length direction of the defect area until the free end of the metal microwire is melted by the periodic pulse discharge generated by the periodic up and down vibration to form metal droplets that are deposited and cover the surface of the defect area.

[0014] Furthermore, in step C, the angle is 15 to 75 degrees.

[0015] Furthermore, in step C, the diameter of the metal microwire is 40 to 80 μm.

[0016] Furthermore, in step D, the potential difference is 0.5-2V.

[0017] Furthermore, in step E, the vibration frequency of the periodic up and down reciprocating vibration is 20 to 50 Hz.

[0018] Furthermore, in step E, the amplitude of the periodic up and down reciprocating vibration is 20 to 50 μm.

[0019] Furthermore, in step E, during the periodic up and down reciprocating vibration, when the free end of the metal microwire vibrates to the lowest point, the vertical distance between the free end of the metal microwire and the surface of the defective area is 5 to 40 μm.

[0020] Furthermore, step B specifically includes: placing the surface-treated fine circuit board on a detection platform, using an automatic optical detection module to determine the circuit break position of the surface-treated fine circuit board, and obtaining the defective area.

[0021] Furthermore, in step A, the specific method of the surface treatment is: purging the surface of the fine circuit board with high-purity nitrogen to remove dust; immersing the fine circuit board after dust removal in a dilute sulfuric acid solution at 25-35°C for 0.03-0.08h, taking it out and rinsing it with clean water, and drying it to obtain the fine circuit board after surface treatment.

[0022] The technical solution provided by the present invention can have the following beneficial effects:

[0023] 1. The periodic pulse discharge method of this technical solution can achieve precise control of the discharge time of a single pulse and the time interval between pulses, which is beneficial to ensure that the metal droplet particle size is appropriate and uniform. The metal droplets with appropriate and uniform particle size have good size matching with the defect area, avoiding the problem of insufficient or excessive deposition caused by metal droplets that are too large or too small, which is beneficial to improve the repair accuracy. At the same time, the amount of metal droplets generated can be adjusted by regulating the discharge time of a single pulse and the time interval between pulses, so that the metal droplets can be basically accurately deposited in the defect area, thereby achieving precise deposition of metal droplets. In addition, the metal microwire has completed precise positioning before it begins to periodically melt to form metal droplets for repair, and an angle is formed between its free end and the defect area (such as Figure 1 (shown as ∠m in the figure). This angle setting effectively suppresses splashing and rebounding of the metal droplets, ensuring that the metal droplets are accurately deposited and fully fill the defect area. Therefore, through the synergistic effect of the angle setting and periodic pulse discharge, this technical solution facilitates the high-precision directional deposition of metal droplets, significantly improving repair accuracy.

[0024] 2. In the process of repairing by melting the metal microwires to form metal droplets, metallurgical bonding is formed between the metal droplets and the fine circuit board through atomic thermal diffusion, rather than simple physical adsorption. The above-mentioned metallurgical bonding mechanism enables the repair area formed by the deposited metal droplets after superposition, fusion and cooling to establish a strong metal bond connection with the fine circuit board, thereby significantly improving the interface bonding strength between the repair area and the fine circuit board (i.e., the repair interface). At the same time, the setting of the angle between the free end of the metal microwire and the defective area can optimize the deposition trajectory of the metal droplets, so that the metal droplets contact the surface of the fine circuit board with the best kinetic energy and thermodynamic state, promote the diffusion bonding between the atoms between the metal droplets and the fine circuit board, and also help to improve the interface bonding strength of the repair interface. Furthermore, this technical solution also performs surface treatment on the fine circuit board before positioning the metal microwires. This surface treatment effectively removes dust contamination and metal passivation films from the fine circuit board's surface, fully exposing the active metal atoms on the fine circuit board's surface. This facilitates a more complete metallurgical bond between the metal droplets and the fine circuit board, further enhancing the interfacial bonding strength of the repair interface. Furthermore, the metal droplets in this technical solution completely melt, preventing unmelted metal particles from remaining at the interface between the repair area and the fine circuit board, which could lead to insufficient interfacial bonding strength between the repair area and the fine circuit board. This helps ensure the bonding strength of the repair interface. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the repair process in Example 1 of the present invention. DETAILED DESCRIPTION

[0026] This technical solution provides a defect repair process for a fine circuit board, comprising the following steps:

[0027] A. Performing surface treatment on the fine circuit board to obtain a fine circuit board after surface treatment;

[0028] B. Determine the defective area based on the disconnection location of the fine circuit board after surface treatment;

[0029] C. placing a metal microwire directly above the defect area, such that an angle is formed between the metal microwire and the defect area;

[0030] D. The metal microwire includes a fixed end and a free end. The fixed end of the metal microwire is electrified to make the metal microwire negatively charged. The surface-treated fine circuit board is electrified to make the surface-treated fine circuit board positively charged, thereby generating an electric potential difference between the surface-treated fine circuit board and the metal microwire.

[0031] E. Under an inert atmosphere, the free end of the metal microwire is made to vibrate periodically up and down directly above the defect area. During the periodic up and down vibration, the free end of the metal microwire is translated along the length direction of the defect area until the free end of the metal microwire is melted by the periodic pulse discharge generated by the periodic up and down vibration to form metal droplets that are deposited and cover the surface of the defect area.

[0032] In order to overcome the defects of existing repair technologies such as poor conductivity after repair and difficulty in maintaining effective repair effects, this technical solution proposes a defect repair process for fine circuit boards. By optimizing the repair process, the repair of fine circuit boards is completed. The entire repair process is simple and easy to operate, which is conducive to improving conductivity and durability of repair effects while improving repair accuracy and reducing thermal damage, so as to meet actual usage needs.

[0033] The specific working principle of the free end of the metal microwire in the present technical solution to melt and form metal droplets due to the periodic pulse discharge generated by the periodic up and down reciprocating vibration is as follows: when the free end of the metal microwire approaches the fine circuit board, the reduction in the distance between the two causes the local electric field strength to increase sharply. Once the breakdown electric field strength threshold of the gas medium between the free end of the metal microwire and the fine circuit board is reached, an instantaneous arc discharge is triggered, causing the free end of the metal microwire to complete the melting and form metal droplets within a few milliseconds; when the free end of the metal microwire is away from the fine circuit board, the electric field strength rapidly decays to below the breakdown electric field strength threshold of the gas medium between the free end of the metal microwire and the fine circuit board, the arc discharge is terminated immediately, and the melting process of the free end of the metal microwire is stopped immediately, so that the free end of the metal microwire periodically melts and forms metal droplets under the periodic pulse discharge mode.

[0034] The periodic pulse discharge method of the present technical solution can achieve precise control of the discharge time of a single pulse and the time interval between pulses, which is beneficial to ensure that the metal droplet size is appropriate and uniform. The metal droplets with appropriate and uniform particle size have good size matching with the defect area, avoiding the problem of insufficient or excessive deposition caused by metal droplets that are too large or too small, which is beneficial to improve the repair accuracy. At the same time, the amount of metal droplets generated can be adjusted by regulating the discharge time of a single pulse and the time interval between pulses, so that the metal droplets can be basically accurately deposited in the defect area, thereby achieving precise deposition of metal droplets. In addition, the metal microwire has completed precise positioning before it starts to periodically melt to form metal droplets for repair, and an angle is formed between its free end and the defect area (such as Figure 1(shown as ∠m in the figure). This angle setting effectively suppresses splashing and rebounding of the metal droplets, ensuring that the metal droplets are accurately deposited and fully fill the defect area. Therefore, through the synergistic effect of the angle setting and periodic pulse discharge, this technical solution facilitates the high-precision directional deposition of metal droplets, significantly improving repair accuracy.

[0035] Furthermore, the time interval between pulses provides the necessary heat diffusion time for the fine circuit board, effectively avoiding the defect of fine circuit board deformation caused by heat accumulation, thereby helping to reduce thermal damage to the fine circuit board. At the same time, the uniformity of the particle size of the metal droplets ensures that each metal droplet carries a similar amount of heat, preventing the technical problem of local overheating causing deformation of the fine circuit board, further reducing thermal damage to the fine circuit board. In addition, the controllable amount of metal droplet generation means that the heat input is controllable, which is also beneficial to avoid the situation where excessive metal melting introduces additional heat and causes deformation of the fine circuit board, further reducing thermal damage to the fine circuit board. That is, the present technical solution helps to avoid thermal damage to the fine circuit board through the mutual cooperation of the above-mentioned multiple effects.

[0036] Secondly, in the process of repairing by melting the metal microwires to form metal droplets, metallurgical bonding is formed between the metal droplets and the fine circuit board through atomic thermal diffusion, rather than simple physical adsorption. The above-mentioned metallurgical bonding mechanism enables the deposited metal droplets to form a strong metal bond connection with the fine circuit board after superposition, fusion and cooling, thereby significantly improving the interfacial bonding strength between the repair area and the fine circuit board (i.e., the repair interface). At the same time, the setting of the angle between the free end of the metal microwire and the defective area can optimize the deposition trajectory of the metal droplets, so that the metal droplets contact the surface of the fine circuit board with the optimal kinetic energy and thermodynamic state, promote the diffusion bonding between the atoms between the metal droplets and the fine circuit board, and also help to improve the interfacial bonding strength of the repair interface. In addition, the present technical solution also performs surface treatment on the fine circuit board before positioning the metal microwires. By performing surface treatment on the fine circuit board, dust pollution and metal passivation film on the surface of the fine circuit board can be effectively removed, and the active metal atoms on the surface of the fine circuit board are fully exposed, which is conducive to forming a more complete metallurgical bond between the metal droplets and the fine circuit board, thereby further improving the interfacial bonding strength of the repair interface. In addition, the metal droplets of the present technical solution are completely melted, which avoids the unmelted metal particles remaining at the interface between the repair area and the fine circuit board, thereby eliminating the defect of insufficient interface bonding strength between the repair area and the fine circuit board, thereby facilitating ensuring the bonding strength of the repair interface.

[0037] In summary, this technical solution significantly improves the interfacial bonding strength of the repair interface through the synergistic effect of the above-mentioned multiple factors, effectively avoiding the problem of easy detachment of the repair area caused by weak interface bonding in the existing repair process, and ensuring the long-term effectiveness of the repair effect.

[0038] Thirdly, during the repair process of the metal microwires melting to form metal droplets, the metal droplets not only form a metallurgical bond with the fine circuit board, but also form a metallurgical bond with each other through thermal diffusion, so that the repair area has a dense internal structure, and the repair area has a higher mechanical strength. At the same time, the metal droplets with uniform and appropriate particle size show a high degree of consistency in thermodynamic behavior, so that they can be evenly distributed in the repair area during the deposition process, which is also conducive to forming a more dense and uniform microstructure during the repair process, which is conducive to the repair area having a dense internal structure and a higher mechanical strength. In addition, before the repair begins, the angle between the free end of the metal microwire and the defect area creates conditions for gradient heat conduction, so that the metal droplets formed by the melting of the free end of the metal microwire can solidify sequentially along the inclined direction to form a controlled solidification process. The above-mentioned controlled solidification process not only reduces internal stress concentration, but also helps to reduce the porosity, so that the density of the repair area is close to the theoretical value, and can also make the repair area have a higher mechanical strength. Therefore, this technical solution, through metallurgical bonding, uniform and appropriate particle size of metal droplets, and angle setting, is conducive to making the repair area have a dense internal structure and higher mechanical strength. It overcomes the shortcomings of the existing repair process that relies solely on intermolecular forces (such as van der Waals forces) and causes insufficient strength inside the repair area. It significantly improves the resistance of the repair area to external forces and thermal stresses, and is also conducive to ensuring the long-term effectiveness of the repair effect.

[0039] Finally, metal microwires are easily converted into high-resistance metal oxides during the melting process, and the metal oxides are easily mixed into the metal droplets, resulting in the presence of high-resistance metal oxides in the repair area, which in turn makes it easy for high-resistance points to appear inside the repair area. Therefore, in this technical solution, under an inert atmosphere, periodic pulse discharge causes the free ends of the metal microwires to periodically melt and form metal droplets, which can effectively prevent the metal microwires from being oxidized to form high-resistance metal oxides during melting, and is also beneficial to ensuring conductivity. At the same time, the dense repair area effectively avoids the problem of discontinuous conductive paths caused by closed pores by suppressing the formation of internal pores, thereby eliminating local high-resistance points, optimizing the carrier transmission path, and achieving enhanced conductivity; in addition, the interface bonding strength between the repair area and the fine circuit to be repaired is high, which effectively avoids the situation where the interface bonding strength between the repair area and the fine circuit to be repaired is poor, resulting in the easy generation of interface pores and the increase of interface contact resistance, and is also beneficial to ensuring the conductivity of the repair area. Furthermore, the complete melting of the metal droplets in this solution prevents unmelted metal particles from remaining in the repaired area, which could lead to high-resistance points and increased resistance within the repaired area, thus improving conductivity. This multiple mechanism ensures excellent conductivity in the repaired area.

[0040] It should be noted that the discharge melting process at the free end of the metal microwire is extremely rapid, usually completed in milliseconds. If a continuous discharge method is used, the following effects will occur: (1) The metal droplet formation speed is too fast, making it difficult to accurately control the repair process, thereby affecting the repair accuracy; (2) The particle size of the metal droplet will be too large and the uniformity will deteriorate, which will not only reduce the matching degree with the defect area, affecting the repair accuracy, but also affect the density of the repair area, thereby adversely affecting the conductivity and the long-term effectiveness of the repair effect; (3) The metal droplet formation speed is too fast, which is prone to excessive accumulation, making it difficult to effectively diffuse the heat accumulated on the fine circuit board, increasing the risk of thermal damage; (4) Continuous discharge cannot provide the necessary thermal diffusion time for the fine circuit board, resulting in further accumulation of heat and aggravated thermal damage. Therefore, this technical solution cannot use the continuous discharge method for repair.

[0041] It should be noted that the inert atmosphere may be argon, nitrogen, etc., and the specific type is not limited here. The metal type of the metal microwire may be copper, silver, gold, etc., and the specific type is also not limited here.

[0042] Further description, in step C, the angle is 15 to 75 degrees.

[0043] If the angle is too small, the direction of the kinetic energy of the metal droplets will be too parallel to the surface of the fine circuit board, which can lead to insufficient spreading of the metal droplets, hindering the formation of a metallurgical bond between the metal droplets and the fine circuit board, affecting the interfacial bonding strength, and thus the durability and conductivity of the repair effect. At the same time, if the angle is too small, the metal microwires will easily interfere with the deposited metal droplets mechanically, affecting the repair accuracy. If the angle is too large, the vertical component of the metal droplet's impact velocity will be too large, which can easily cause splashing and affect the repair accuracy. Therefore, by optimizing the angle, this technical solution is conducive to improving the performance of repair accuracy and the durability and effectiveness of the repair effect.

[0044] Further, in step C, the diameter of the metal microwire is 40 to 80 μm.

[0045] If the diameter of the metal microwire is too large, not only will the metal microwire require a higher discharge energy to achieve complete melting, which will easily increase energy consumption, but the particle size of the metal droplets formed will be too large, which will easily affect the repair accuracy. At the same time, the inertia of the metal microwire that is too thick increases during the vibration process, reducing the control sensitivity of the discharge process. If the diameter of the metal microwire is too small, not only will the heat capacity of the metal microwire be insufficient, which will easily lead to premature complete vaporization and difficulty in forming complete metal droplets, but the solution will also reduce the mechanical strength of the metal microwire, making it easy to break during the vibration process. At the same time, the volume of the droplets formed by the metal microwire that is too fine is too small, and more deposition times are required to complete the repair, which will easily reduce the repair efficiency. Therefore, the present technical solution limits the diameter of the metal microwire to 40 to 80 μm, which can not only achieve high-precision repair but also improve production efficiency.

[0046] Further description, in step D, the potential difference is 0.5-2V.

[0047] By limiting the potential difference, it is helpful to ensure the melting speed of the free end of the metal microwire, thereby ensuring the uniformity of the particle size of the metal droplets and regulating the amount of metal droplets generated, thereby ensuring the repair effect.

[0048] Further description: In step E, the vibration frequency of the periodic up and down reciprocating vibration is 20 to 50 Hz.

[0049] By limiting the vibration frequency, it is not only beneficial to ensure the uniformity of the particle size of the metal droplets and regulate the amount of metal droplets generated, thereby ensuring the repair effect, but also the duration of a single electric pulse discharge can be adjusted according to actual needs, thereby improving the flexibility of the repair process.

[0050] To further illustrate, in step E, the amplitude of the periodic up and down reciprocating vibration is 20 to 50 μm.

[0051] If the amplitude is too small, it will lead to insufficient changes in the electric field strength, thereby reducing the frequency of droplet formation and causing a decrease in repair efficiency. At the same time, too small an amplitude may also cause insufficient metal droplet generation, making the continuity of the metal droplet deposition process worse. The lack of the above continuity will not only weaken the interface bonding strength between the repair area and the fine circuit board, thereby affecting the conductivity and the durability of the repair effect, but will also make it easy for pores to appear inside the repair area, affecting the density of the repair area, thereby also adversely affecting the conductivity and the long-term effectiveness of the repair effect. If the amplitude is too large, the energy of a single pulse discharge will be too high, and the particle size of the metal droplets formed will be too large, thereby affecting the repair accuracy. Therefore, the present technical solution limits the amplitude of the periodic up and down reciprocating vibration, which is conducive to ensuring the repair effect.

[0052] To further illustrate, in step E, during the periodic up and down reciprocating vibration, when the free end of the metal microwire vibrates to the lowest point, the vertical distance between the free end of the metal microwire and the surface of the defective area is 5 to 40 μm.

[0053] By measuring the vertical distance between the free end of the metal microwire and the surface of the defect area (such as Figure 1 It is limited by n), so that it can be selected according to actual needs, which is not only conducive to ensuring that the particle size of the metal droplets is appropriate and uniform, but also conducive to ensuring the amount of metal droplets generated, thereby ensuring the repair effect.

[0054] To further illustrate, step B specifically includes: placing the surface-treated fine circuit board on a detection platform, using an automatic optical detection module to determine the circuit break position of the surface-treated fine circuit board, and obtaining the defective area.

[0055] The automated optical inspection module works by automatically scanning a fine circuit board with a camera, capturing images, comparing the tested solder joints with qualified parameters in a database, and then, through image processing, detecting defects on the fine circuit board. These defects are then displayed or marked on a display or with an automatic marker. Therefore, this technical solution, by using the automated optical inspection module to determine the location of breaks on fine circuit boards after surface treatment, facilitates precise identification of defect areas and accurate repairs.

[0056] Further explanation, in step A, the specific method of the surface treatment is: purging the surface of the fine circuit board with high-purity nitrogen to remove dust; immersing the fine circuit board after dust removal in a dilute sulfuric acid solution at 25-35°C for 0.03-0.08h, taking it out and rinsing it with clean water, and drying it to obtain the fine circuit board after surface treatment.

[0057] This technical solution further optimizes the surface treatment method, which is beneficial to fully expose the active metal atoms on the surface of the fine circuit board, further improve the interfacial bonding strength of the repair interface, and thus further ensure the conductivity and the lasting effectiveness of the repair effect.

[0058] The technical solution of the present invention is further illustrated below through specific implementation methods.

[0059] Test Method

[0060] Repair accuracy: Use laser confocal microscopy to measure the line width deviation of the repaired area. If the line width deviation is ≤±3μm, it is qualified.

[0061] Thermal damage performance: Use a scanning electron microscope to observe whether the repaired fine circuit board has obvious thermal deformation. If no obvious thermal deformation occurs, there is no obvious thermal damage and the thermal damage performance is qualified.

[0062] Conductivity: Use the four-point probe method to measure the surface resistivity of the four corners and the middle position of the repair area. Take the average value of the measurement results of the above five positions as the resistivity. If the resistivity of the repair area is ≤ 1.2 times the resistivity of the fine circuit board, it is qualified.

[0063] Peel strength: The peel strength between the fine circuit board and the repaired area is measured using a tensile testing machine. If the peel strength is ≥300N / cm, it is considered qualified. It should be noted that the interfacial bonding strength between the fine circuit board and the repaired area is closely related to the peel strength between the fine circuit board and the repaired area. The greater the peel strength between the fine circuit board and the repaired area, the greater the peel strength between the fine circuit board and the repaired area. Therefore, this technical solution uses peel strength to characterize interfacial bonding strength.

[0064] Tensile strength: A nanoindenter is used to measure the tensile strength and compressive strength of the repaired area. If the tensile strength is ≥30MPa and the compressive strength is ≥80MPa, it is qualified.

[0065] Example 1

[0066] A. Use high-purity nitrogen to purge the surface of the fine circuit board to remove dust; immerse the fine circuit board after dust removal in a dilute sulfuric acid solution at 35°C for 0.05h, remove it and rinse it with clean water, and dry it to obtain the fine circuit board after surface treatment;

[0067] B. Place the surface-treated fine circuit board on the inspection platform and use the automatic optical inspection module to determine the circuit break position of the surface-treated fine circuit board and obtain the defect area;

[0068] C. Place a 40 μm diameter copper microwire directly above the defect area, with a 30° angle between the copper microwire and the defect area and between the gold microwire and the defect area;

[0069] D. The copper microwire includes a fixed end and a free end. The fixed end of the copper microwire is electrified to make it negatively charged. The surface-treated fine circuit board is electrified to make it positively charged, creating a 1V potential difference between the surface-treated fine circuit board and the copper microwire.

[0070] E. Under a nitrogen atmosphere, the free end of the copper microwire is subjected to periodic up and down reciprocating vibration directly above the defect area. During the periodic up and down reciprocating vibration, the free end of the copper microwire is translated along the length direction of the defect area until copper droplets formed by melting the free end of the copper microwire due to the periodic pulse discharge generated by the periodic up and down reciprocating vibration are deposited and cover the surface of the defect area; wherein, during the periodic up and down reciprocating vibration, when the free end of the copper microwire vibrates to the lowest point, the vertical distance between the end of the free end of the copper microwire and the surface of the defect area is 30 μm; the vibration frequency of the periodic up and down reciprocating vibration is 40 Hz, and the amplitude is 20 μm.

[0071] Example 2

[0072] A. Use high-purity nitrogen to purge the surface of the fine circuit board to remove dust; immerse the fine circuit board after dust removal in a dilute sulfuric acid solution at 30°C for 0.03h, remove it and rinse it with clean water, and dry it to obtain the fine circuit board after surface treatment;

[0073] B. Place the surface-treated fine circuit board on the inspection platform and use the automatic optical inspection module to determine the circuit break position of the surface-treated fine circuit board and obtain the defect area;

[0074] C. Place a 60 μm diameter silver microwire directly above the defect area, with a 50° angle between the silver microwire and the defect area and between the gold microwire and the defect area;

[0075] D. The silver microwire includes a fixed end and a free end. The fixed end of the silver microwire is electrified to make it negatively charged. The surface-treated fine circuit board is electrified to make it positively charged, creating a potential difference of 0.5V between the surface-treated fine circuit board and the copper microwire.

[0076] E. Under an argon atmosphere, the free end of the silver microwire is caused to vibrate periodically up and down directly above the defect area. During this periodic up and down vibration, the free end of the silver microwire translates longitudinally along the defect area until silver droplets formed by melting the free end of the silver microwire due to the periodic pulse discharge generated by the periodic up and down vibration are deposited and cover the surface of the defect area; wherein, during this periodic up and down vibration, when the free end of the silver microwire vibrates to the lowest point, the vertical distance between the end of the free end of the silver microwire and the surface of the defect area is 20 μm; the vibration frequency of the periodic up and down vibration is 30 Hz, and the amplitude is 20 μm.

[0077] Example 3

[0078] A. Use high-purity nitrogen to purge the surface of the fine circuit board to remove dust; immerse the fine circuit board after dust removal in a dilute sulfuric acid solution at 25°C for 0.08h, remove it and rinse it with clean water, and dry it to obtain the fine circuit board after surface treatment;

[0079] B. Place the surface-treated fine circuit board on the inspection platform and use the automatic optical inspection module to determine the circuit break position of the surface-treated fine circuit board and obtain the defect area;

[0080] C. Place a gold microwire with a diameter of 80 μm directly above the defect area, with the gold microwire and the defect area forming a 60° angle;

[0081] D. The gold microwire consists of a fixed end and a free end. Applying electricity to the fixed end of the gold microwire makes it negatively charged. Applying electricity to the surface-treated fine circuit board makes it positively charged, creating a 2V potential difference between the surface-treated fine circuit board and the copper microwire.

[0082] E. Under a nitrogen atmosphere, the free end of the gold microwire is subjected to periodic up and down reciprocating vibration directly above the defect area. During the periodic up and down reciprocating vibration, the free end of the gold microwire is translated along the length direction of the defect area until the free end of the gold microwire is melted by the periodic pulse discharge generated by the periodic up and down reciprocating vibration to form gold droplets that are deposited and cover the surface of the defect area; wherein, during the periodic up and down reciprocating vibration, when the free end of the gold microwire vibrates to the lowest point, the vertical distance between the end of the free end of the gold microwire and the surface of the defect area is 40 μm; the vibration frequency of the periodic up and down reciprocating vibration is 30 Hz, and the amplitude is 40 μm.

[0083] Comparative Example 1

[0084] In Comparative Example 1, the metal paste sintering method was used for repair, and the specific repair process was as follows:

[0085] A. Performing surface treatment on the fine circuit board to obtain a fine circuit board after surface treatment;

[0086] B. Determine the defective area based on the disconnection location of the fine circuit board after surface treatment;

[0087] C. Apply a layer of nano-copper paste on the defective area and add 0.3 mL of 1.5 mol / L copper sulfate solution to cover the nano-copper paste in the defective area. Insert a metal probe from above the copper sulfate solution and contact the nano-copper paste. Apply a 10 V, 50 Hz sharp pulse voltage to the fine circuit board to rapidly heat up the pulse copper sulfate solution and nano-copper powder. Move a laser probe with a diameter of 20 μm to a height of 100 μm from the fine circuit board and emit a laser for sintering. During the laser sintering process, the laser probe is translated along the length of the defective area until the nano-copper paste in the defective area is completely sintered into a copper circuit and covers the surface of the defective area.

[0088] Comparative Example 2

[0089] In Comparative Example 2, metal ion reduction method was used for repair, and the specific repair process was as follows:

[0090] A. Performing surface treatment on the fine circuit board to obtain a fine circuit board after surface treatment;

[0091] B. Determine the defective area based on the disconnection location of the fine circuit board after surface treatment;

[0092] C. Power is applied to the surface-treated fine circuit board to make it positively charged, thereby generating a potential difference between the surface-treated fine circuit board and the metal microwire;

[0093] D. Place the energized fine circuit board in a 10% copper sulfate solution, completely immersing the board. Move a 50μm diameter metal probe to a point 100μm above the defect area. Apply a negative charge to the probe, creating a 3V potential difference between the fine circuit board and the probe. Move the probe horizontally along the length of the defect area until the potential difference causes copper particles, reduced from the copper sulfate, to deposit and cover the surface of the defect area.

[0094] Comparative Example 3

[0095] The repair process and raw materials of Comparative Example 3 are the same as those of Example 1, except that the fine circuit board is not surface treated in Comparative Example 3.

[0096] Comparative Example 4

[0097] The repair process and raw materials of Comparative Example 4 are the same as those of Example 1, except that no tilt angle is set between the metal microwire and the defective area in Comparative Example 4, that is, the metal microwire and the defective area in Comparative Example 4 are set perpendicular to each other.

[0098] Comparative Example 5

[0099] The repair process and raw materials of Comparative Example 5 are the same as those of Example 1, except that the pulse discharge is continuously performed in Comparative Example 5.

[0100] The defective areas of the fine circuit board were repaired using the different repair processes in the above embodiment and comparative example, and performance tests were performed on the repaired areas of the fine circuit board. The test results are shown in Table 1 below.

[0101] Table 1 Performance test results of repaired areas obtained by different repair processes

[0102]

[0103] From the test data in Table 1, it can be seen that the peel strength of the present technical solution is ≥300N / cm, and the interface bonding strength between the fine circuit board and the repair area is closely related to the peel strength between the fine circuit board and the repair area. When the peel strength between the fine circuit board and the repair area is greater, the peel strength between the fine circuit board and the repair area is also greater. Therefore, the present technical solution has a higher interface bonding strength. And the interface bonding strength is conducive to ensuring the durability of the repair effect. Therefore, the repair area of the present technical solution has the durability of the repair effect. At the same time, the line width deviation of the present technical solution is ≤±3μm, which has a higher repair accuracy. In addition, the resistivity of the repair area is ≤1.2 times the resistivity of the fine circuit board, and has good conductivity. In addition, through comparative experiments, it was found that the performance of the repair area obtained by the repair process of the present technical solution is better than the performance of the repair area in Comparative Example 1 and Comparative Example 2 (Comparative Example 1 and Comparative Example 2 are both prior art) in various performance test indicators. Therefore, the repair area obtained by the defect repair process of a fine circuit board of the present technical solution is conducive to improving the conductivity and durability of the repair effect under the premise of improving the repair accuracy and reducing thermal damage.

[0104] In Comparative Example 3, since the fine circuit board was not surface treated, the interface bonding strength deteriorated, affecting the durability and conductivity of the repair effect.

[0105] Comparative Example 4, due to the perpendicular arrangement of the metal microwire and the defective area, will result in the following defects: (1) The tilt angle setting can effectively suppress the splashing and rebound of the metal droplets, ensuring that the metal droplets can be accurately deposited and fully fill the defective area. The failure to set the above-mentioned tilt angle setting results in a decrease in the repair accuracy; (2) The setting of the tilt angle can optimize the deposition trajectory of the metal droplets, so that the metal droplets contact the surface of the fine circuit board with the best kinetic energy and thermodynamic state, promote the diffusion and bonding between the atoms of the metal droplets and the fine circuit board, and also help to improve the interfacial bonding strength of the repair interface. Due to the failure to set the above-mentioned tilt angle setting, it is unable to play its role in improving the interfacial bonding strength, causing the interfacial bonding strength to deteriorate, thereby affecting the long-term effectiveness and conductivity of the repair effect. (3) The setting of the tilt angle creates a gradient heat conduction condition, so that the molten metal droplets at the free end of the metal microwire can solidify sequentially along the tilt direction to form a controlled solidification process. The above-mentioned controlled solidification process not only reduces the internal stress concentration, but also helps to reduce the porosity, so that the density of the repair area is close to the theoretical value. Since the above-mentioned inclination angle is not set, the density of the repair area is reduced, which not only leads to a decrease in its mechanical strength and affects the long-term effectiveness of the repair effect, but also easily induces closed pores, destroys the continuity of the conductive path, forms a local high resistance area, and ultimately leads to poor conductivity.

[0106] In Comparative Example 5, due to the continuous pulse discharge, the speed of metal droplet formation will be too fast, making it difficult to accurately control the repair process and affecting the repair accuracy. At the same time, continuous discharge will also make the particle size of the metal droplets too large and the uniformity worse, which will not only reduce its matching degree with the defective area, further affecting the repair accuracy, but also cause the density of the repair area to deteriorate, thereby adversely affecting the conductivity and the long-term effectiveness of the repair effect. In addition, continuous pulse discharge is likely to cause excessive accumulation of metal droplets, making it impossible for the heat accumulated on the fine circuit board to be effectively diffused, increasing the risk of thermal damage. In addition, continuous discharge cannot provide the necessary heat diffusion time for the fine circuit board, resulting in further accumulation of heat and exacerbating thermal damage.

[0107] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are intended solely to illustrate the principles of the present invention and are not to be construed in any way as limiting the scope of protection of the present invention. Based on the explanations herein, those skilled in the art will readily conceive of other specific embodiments of the present invention without inventive effort, and such embodiments will fall within the scope of protection of the present invention.

Claims

1. A defect repair process for a fine circuit board, characterized in that: The following steps are involved: A. Performing surface treatment on the fine circuit board to obtain a fine circuit board after surface treatment; B. Determine the defective area based on the disconnection location of the fine circuit board after surface treatment; C. placing a metal microwire directly above the defect area, such that an angle is formed between the metal microwire and the defect area; D. The metal microwire includes a fixed end and a free end. The fixed end of the metal microwire is electrified to make the metal microwire negatively charged. The surface-treated fine circuit board is electrified to make the surface-treated fine circuit board positively charged, thereby generating an electric potential difference between the surface-treated fine circuit board and the metal microwire. E. Under an inert atmosphere, the free end of the metal microwire is made to vibrate periodically up and down directly above the defect area. During the periodic up and down vibration, the free end of the metal microwire is translated along the length direction of the defect area until the free end of the metal microwire is melted by the periodic pulse discharge generated by the periodic up and down vibration to form metal droplets that are deposited and cover the surface of the defect area.

2. The defect repair process for a fine circuit board according to claim 1, characterized in that: In step C, the angle is 15 to 75 degrees.

3. The defect repair process for a fine circuit board according to claim 1, characterized in that: In step C, the diameter of the metal microwire is 40 to 80 μm.

4. The defect repair process for a fine circuit board according to claim 1, characterized in that: In step D, the potential difference is 0.5-2V.

5. The defect repair process for a fine circuit board according to claim 1, characterized in that: In step E, the frequency of the periodic up and down reciprocating vibration is 20 to 50 Hz.

6. The defect repair process for a fine circuit board according to claim 1, characterized in that: In step E, the amplitude of the periodic up and down reciprocating vibration is 20 to 50 μm.

7. The defect repair process for a fine circuit board according to claim 1, characterized in that: In step E, during the periodic up and down reciprocating vibration, when the free end of the metal microwire vibrates to the lowest point, the vertical distance between the free end of the metal microwire and the surface of the defective area is 5 to 40 μm.

8. The defect repair process for a fine circuit board according to claim 1, characterized in that: Step B specifically includes: placing the fine circuit board after surface treatment on the inspection platform, using the automatic optical inspection module to determine the circuit break position of the fine circuit board after surface treatment, and obtaining the defective area.

9. The defect repair process for a fine circuit board according to claim 1, characterized in that: In step A, the specific method of the surface treatment is: purging the surface of the fine circuit board with high-purity nitrogen to remove dust; immersing the fine circuit board after dust removal in a dilute sulfuric acid solution at 25-35° C. for 0.03-0.08 h, taking it out and rinsing it with clean water, and drying it to obtain the fine circuit board after surface treatment.

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