A PCB resin plug hole process method without residual glue

Abstract

This invention belongs to the field of PCB board processing technology, specifically relating to a residue-free PCB resin via-filling process. The process includes the following steps: applying a high-temperature and acid / alkali-resistant process protective film to both sides of a fully dried PCB; laser drilling corresponding to the through-holes to burn off the process protective film, exposing the holes requiring resin filling; placing the laser-filled PCB into a vacuum plasma treatment device for plasma pretreatment using process gases; after treatment, cooling while maintaining vacuum conditions, filling with nitrogen to atmospheric pressure, and then removing the PCB. This invention, by adding a temperature- and pressure-controlled plasma pretreatment step after laser burning, utilizes the synergistic effect of chemical removal and physical bombardment to remove the copper oxide layer and carbide residue generated during laser burning, restoring the copper surface to a clean and activated state, and improving the interfacial bonding strength between the resin and copper.

Description

Technical Field

[0001] This invention belongs to the field of PCB board processing technology, specifically relating to a PCB resin via plugging process method with no residual adhesive. Background Technology

[0002] With the rapid development of 5G communication, automotive electronics, and high-end equipment, printed circuit boards (PCBs) are continuously upgrading towards higher density, more layers, and higher reliability. Among these advancements, stacked blind and buried via structures have become a key technology for achieving high-density interconnects, while resin plugging is a core process ensuring its electrical performance and reliability. The fundamental purpose of resin plugging is to fill the vias and then metallize the via openings through subsequent electroplating, forming a complete conductive path. Its quality directly affects the signal transmission performance and long-term reliability of PCB products.

[0003] In existing technologies, the core process of "applying protective film on both sides → laser windowing to expose the hole to be plugged → plugging the hole → removing the film → polishing" has been widely used. However, this process still faces three key technical challenges: First, residual adhesive on the board surface. During resin plugging, resin tends to adhere to non-plugged areas of the PCB. Removing residual adhesive can lead to insufficient copper thickness, causing PCB signal distortion. Additionally, residual adhesive can block etching solutions, resulting in incomplete etching and short circuits. Second, the heat-affected zone (HAZ) at the hole opening after laser burning. Laser energy inevitably has a thermal effect on the copper foil surface and hole walls around the hole opening, forming copper oxide and carbide residues. This significantly reduces the bonding strength between the resin and copper, easily leading to microcrack propagation, interface delamination, and even copper breakage during thermal cycling. Third, residual stress from laser processing. Laser burning is a rapid energy pulse process. The copper layer around the hole opening experiences instantaneous thermal expansion and rapid cooling, generating residual thermal stress. This residual stress can induce microscopic deformation of the copper layer during subsequent resin curing and thermal cycling, amplifying hole opening defects.

[0004] To address the aforementioned issues, existing technologies primarily improve via plugging quality by optimizing plugging parameters and curing processes. However, they generally neglect the impact mechanism of residual material in the heat-affected zone after laser windowing on the quality of the resin-plugged via interface, and have not proposed targeted residual stress relief solutions. Therefore, developing a residue-free resin plugging process that can simultaneously solve the problems of residual adhesive on the board surface, laser heat-affected zone, and residual stress has significant industrial application value. Summary of the Invention

[0005] The purpose of this invention is to provide a residue-free PCB resin via-filling process. By adding a temperature- and pressure-controlled plasma pretreatment step after laser ablation, the copper oxide layer and carbide residue generated by laser ablation are removed through the synergistic effect of chemical removal and physical bombardment, so that the copper surface is restored to a clean and activated state, and the interfacial bonding strength between the resin and copper is improved.

[0006] The specific technical solution adopted by this invention is as follows: A residue-free PCB resin via-filling process includes the following steps: St1: Double-sided film application: Apply a high-temperature resistant and acid / alkali resistant process protective film to both sides of the fully dried PCB. St2: Laser burning: Laser drilling is performed on the corresponding through holes to burn off the process protective film and expose the holes that need to be filled with resin. St3: Temperature and pressure controlled plasma pretreatment: The PCB after laser burning is placed into a vacuum plasma treatment equipment and pretreated with process gas. After treatment, the temperature is lowered while maintaining vacuum conditions, and nitrogen is introduced to atmospheric pressure before removal. St4: Resin plugging and curing: Resin plugging is performed, then the process protective film is physically peeled off, and the resin is pre-cured using a segmented semi-baking process; St5: Resin plugging and polishing: Use non-woven fabric to polish the overflowing resin at the through hole position to ensure the board surface is flat. St6: Resin Post-Cure: The polished PCB board is baked at high temperature to complete the resin curing. St7: Electroplating Filling: Electroplating fills the entire PCB board after post-curing to achieve metallization of the holes and flatness of the board surface; The process gas is a mixture of oxygen and argon, wherein the volume percentage of oxygen in the mixture is 30% to 50%, and the volume percentage of argon is 50% to 70%.

[0007] In a preferred embodiment, in step St1, the PCB drying temperature is 150–170°C, and the drying time is 2–3 hours; the application speed of the process protective film is 1 m / min, the application temperature is 110°C, and the application pressure is 6 kg / cm². 2 .

[0008] In a preferred embodiment, in step St2, the parameters for laser drilling are: suction pressure -3 to -13 kPa, reference energy 18 mJ, aperture 18 μm, pulse width 14*6*4 μs, number of pulses 1*1*2 shots, photomask level 5, and ultrasonic cleaning after laser drilling.

[0009] In a preferred embodiment, in step St3, the total flow rate of the process gas is 200–400 sccm; the parameters of the plasma treatment are: excitation power 500–800 W, chamber pressure 50–200 mTorr, treatment temperature 45–65 °C, and treatment time 3–8 minutes; after treatment, the temperature is lowered to below 30 °C.

[0010] In a preferred embodiment, in step St4, the parameters for resin plugging are: vacuum degree 15000~25000Pa, scraper speed 3~7mm / s, plugging pressure 70~100kgf; the parameters for the segmented semi-baking process are: first baking at 80℃ for 30min, then baking at 110℃ for 30min for semi-baking, with a temperature change rate of 0.5~1℃ / min.

[0011] In a preferred embodiment, in step St5, the parameters of the nonwoven grinding plate are: 600-800 mesh nonwoven fabric, current 1.5A, and speed 2.5m / min.

[0012] In a preferred embodiment, in step St6, the parameters for the high-temperature post-baking are: baking at 150°C for 30 minutes, with a temperature change rate of 0.5–1°C / min, followed by natural cooling to room temperature after cooling down to 80°C.

[0013] In a preferred embodiment, in step St7, the electroplating leveling process employs an acidic sulfate copper plating process. The plating solution composition is 180–220 g / L copper sulfate, 50–70 g / L sulfuric acid, and 50–80 mg / L chloride ions. The electroplating parameters are: current density 1.5–3.0 A / dm³. 2 The plating bath temperature is 20–25℃, the electroplating time is 20–40 min, and the air stirring speed is 2–3 m / s. 3 / h.

[0014] Application of the residue-free PCB resin via plugging process described in any of the above descriptions in the manufacture of high-density interconnect boards and multilayer stacked blind and buried via PCB structures.

[0015] The technical effects achieved by this invention are as follows: This invention adds a temperature- and pressure-controlled plasma pretreatment step after laser ablation, using a mixture of oxygen and argon gas. Through the synergistic effect of chemical removal and physical bombardment, it removes the copper oxide layer and carbide residue generated by laser ablation, eliminates residues in the laser heat-affected zone, restores the copper surface to a clean and activated state, and improves the interfacial bonding strength between the resin and copper. This solves the problems of microcrack propagation, interfacial delamination, and copper hole fracture caused by poor interfacial bonding in the prior art. At the same time, it provides an activated copper surface substrate for the electroplating filling step. This invention releases residual thermal stress introduced by laser processing in the orifice area through continuous micro-bombardment of argon ions during plasma treatment, allowing the copper layer to return to a state closer to thermodynamic equilibrium. This suppresses the generation of orifice depression defects from the source, provides a smooth orifice morphology for electroplating, and avoids uneven electroplating thickness and void defects. This invention effectively blocks resin residue by applying a process protective film to both sides of the PCB, achieving a residue-free PCB surface and avoiding the problem of incomplete etching caused by resin residue. At the same time, the use of non-woven fabric abrasion method reduces copper thickness loss, ensures the signal transmission performance of the PCB, and also leaves sufficient copper thickness allowance for subsequent electroplating. Attached Figure Description

[0016] Figure 1 This is a process flow diagram from Embodiment 1 of the present invention; Figure 2 This is a morphology image of the PCB hole surface after laser burning in Embodiment 1 of the present invention; Figure 3 This is a cross-sectional view of the resin plug pore fullness in Embodiment 1 of the present invention; Figure 4 This is a diagram of the electroplating filler morphology in Embodiment 1 of the present invention; Figure 5 This is a slice image of the PCB hole thermal shock test in Test Example 2 of this invention; Figure 6 This is a cross-sectional view of the PCB hole reflow soldering test in Test Example 2 of this invention; Figure 7 This is a schematic diagram of the XPS analysis results in Test Example 3 of this invention. Detailed Implementation

[0017] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0018] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0019] Secondly, the term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in a preferred embodiment" appearing in different places throughout this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that mutually excludes other embodiments.

[0020] Example 1

[0021] Please see Figures 1 to 4 As shown, this embodiment provides a PCB resin via plugging process with no residue, and the specific steps are as follows: The PCB was dried at 160℃ for 2.5 hours, and then Y314AC process protective film was applied to both sides of the PCB at a speed of 1 m / min, a temperature of 110℃, and a pressure of 6 kg / cm². 2 Next, laser ablation was performed with the following parameters: suction pressure -8 kPa, aperture 18 μm, energy 14*6*4, reference 18 mJ, pulse width: 14 μs (first pulse), 6 μs (second pulse), 4 μs (third pulse), pulse count 1*1*2 shots, photomask level 5. After ablation, ultrasonic cleaning was performed (e.g., Figure 2 (As shown); The cleaned PCB is placed in a vacuum plasma treatment device, treated with a mixture of oxygen and argon gas, with oxygen accounting for 40% by volume and argon accounting for 60% by volume, a total gas flow rate of 300 sccm, a plasma excitation power of 650W, a chamber pressure of 80 mTorr, a treatment temperature of 55℃, and a treatment time of 6 minutes. After treatment, the chamber temperature is cooled to 28℃ while maintaining a vacuum (cooling rate ≤ 5℃ / min), and nitrogen is introduced to atmospheric pressure before removal; then resin plugging is performed, with a vacuum degree of 18773Pa, a plugging pressure of 84 kgf, and a scraper speed of 4.82 mm / s (e.g. Figure 3 (As shown in the image). After plugging the holes, the protective film is physically peeled off, and a segmented semi-baking process is performed. First, it is baked at 80℃ for 30 minutes, then at 110℃ for 30 minutes, with a temperature change rate of 0.8℃ / min. Next, the board is polished sequentially using 600-mesh and 800-mesh non-woven fabrics at a current of 1.5A and a speed of 2.5m / min. After polishing, it is baked at 150℃ for 30 minutes for post-curing, with a temperature change rate of 0.8℃ / min. After cooling to 80℃, it is allowed to cool naturally to room temperature. Finally, electroplating is performed to fill the gaps using an acidic sulfate copper plating process. The plating solution consists of 200g / L copper sulfate, 60g / L sulfuric acid, and 65mg / L chloride ions, with a current density of 2.2A / dm³. 2 The plating bath temperature was 22℃, the electroplating time was 30 minutes, and the air stirring speed was 2.5 m / s. 3 / h, achieving metallization of the vias and a flat board surface, resulting in a resin-filled PCB with no residual adhesive (such as...). Figure 4 (As shown).

[0022] Furthermore, in this embodiment, the process protection film is obtained commercially, specifically model Y314AC (Shenzhen Yixin Electronics Co., Ltd.). It is made by coating a layer of silicone pressure-sensitive adhesive onto a heat-resistant transparent PET film and then laminating it with a release film. It has the characteristics of high temperature resistance and acid and alkali resistance. Of course, other process protection films with the same properties can also be selected, which does not constitute a specific limitation here.

[0023] It should be noted that, firstly, by applying a process protective film to both sides of the PCB, resin residue can be effectively blocked, achieving a residue-free PCB surface and avoiding incomplete etching problems caused by resin residue; secondly, adding a temperature- and pressure-controlled plasma pretreatment step after laser ablation allows the active oxygen free radicals in the oxygen plasma to convert carbides into gaseous products such as CO and CO2, reducing copper oxide or converting it into easily removable intermediate products. Argon plasma removes surface contaminants and produces a surface roughening effect through physical bombardment. The two work synergistically to remove the copper oxide layer and carbide residue generated by laser ablation, restoring the copper surface to a clean and activated state. At the same time, the continuous micro-bombardment of argon ions is equivalent to micro-scale "stress vibration," which helps to locally release and redistribute residual stress from laser processing, suppressing hole depression defects from the source. Furthermore, the low-temperature treatment of 45–65°C prevents the copper surface from undergoing re-oxidation during the treatment process. Finally, the segmented curing method and gentle temperature change rate can fully degas the resin, avoid the formation of bubbles and voids, slow down the resin curing reaction, reduce volume shrinkage and residual internal stress, and further improve the bonding force between the resin and the hole wall and the copper layer. Finally, in the electroplating filling step, the clean and activated copper surface and the low-recession (≤15μm) hole can significantly improve the nucleation uniformity and bonding force of the copper plating layer, avoid defects such as voids, peeling, and uneven thickness of the electroplating layer, form a complete and continuous conductive path, and ensure the electrical performance of the PCB. Through the synergistic effect of the above process steps, the process in this embodiment has multiple technical effects, including eliminating impurities at the source, activating the interface to improve bonding, and releasing stress in advance.

[0024] Example 2

[0025] This embodiment is based on Embodiment 1, with the plasma excitation power in the plasma pretreatment process adjusted to 800W, the oxygen ratio in the mixed gas adjusted to 50%, and the grinding plate method changed to a ceramic brush, while all other aspects remain unchanged. Specifically: The PCB was dried at 160℃ for 2.5 hours, and then Y314AC process protective film was applied to both sides of the PCB at a speed of 1 m / min, a temperature of 110℃, and a pressure of 6 kg / cm². 2Next, laser ablation was performed with the following parameters: suction plate pressure -8 kPa, aperture 18 μm, energy 14*6*4, reference 18 mJ, pulse width: 14 μs (first pulse), 6 μs (second pulse), 4 μs (third pulse), photomask level 5. After ablation, ultrasonic cleaning was performed. The cleaned PCB was then placed in a vacuum plasma treatment device, treated with a mixture of oxygen and argon gas (50% oxygen, 50% argon, total gas flow rate 300 sccm, plasma excitation power 800 W, chamber pressure 80 mTorr, treatment temperature 55℃, and treatment time 6 minutes. After treatment, the chamber temperature was cooled to 28℃ under vacuum (cooling rate ≤ 5℃ / min), then filled with nitrogen to atmospheric pressure before removal. Subsequently, denaturation was performed. The pores were plugged with grease under a vacuum of 18773 Pa, a plugging pressure of 84 kgf, and a scraper speed of 4.82 mm / s. After plugging, the protective film was physically peeled off, followed by segmented semi-baking: first at 80℃ for 30 min, then at 110℃ for 30 min, with a temperature change rate of 0.8℃ / min. Next, the plate was polished using two sections of 400-mesh and 600-mesh ceramic brushes at a current of 1.5 A and a speed of 2.6 m / min. After polishing, it was post-cured at 150℃ for 30 min, with a temperature change rate of 0.8℃ / min, then cooled to 80℃ and allowed to cool naturally to room temperature. Finally, electroplating was performed to fill the gaps using an acidic sulfate copper plating process. The plating solution consisted of 200 g / L copper sulfate, 60 g / L sulfuric acid, and 65 mg / L chloride ions, with a current density of 2.2 A / dm³. 2 The plating bath temperature was 22℃, the electroplating time was 30 minutes, and the air stirring speed was 2.5 m / s. 3 / h, to achieve metallization of the hole opening and flatness of the board surface, resulting in a resin-filled PCB with no residual adhesive.

[0026] Example 3

[0027] This embodiment is based on Embodiment 1, with the plasma excitation power in the plasma pretreatment process adjusted to 500W, the oxygen ratio in the mixed gas adjusted to 30%, and the grinding method changed to a leveling machine, while all other aspects remain unchanged. Specifically: The PCB was dried at 160℃ for 2.5 hours, and then Y314AC process protective film was applied to both sides of the PCB at a speed of 1 m / min, a temperature of 110℃, and a pressure of 6 kg / cm². 2Next, laser ablation was performed with the following parameters: suction plate pressure -8 kPa, aperture 18 μm, energy 14*6*4, reference 18 mJ, pulse width: 14 μs (first pulse), 6 μs (second pulse), 4 μs (third pulse), pulse count 1*1*2 shots, photomask level 5. After ablation, ultrasonic cleaning was performed. The cleaned PCB was then placed in a vacuum plasma treatment device, using a mixture of oxygen and argon gas (30% oxygen, 70% argon, total gas flow rate 300 sccm, plasma excitation power 500 W, chamber pressure 80 mTorr, treatment temperature 55℃, and treatment time 6 minutes. After treatment, the chamber temperature was cooled to 28℃ while maintaining a vacuum (cooling rate ≤ 5℃ / min), and then nitrogen was introduced. After reaching atmospheric pressure, the plate is removed; then resin plugging is performed under a vacuum of 18773 Pa, a plugging pressure of 84 kgf, and a scraper speed of 4.82 mm / s; after plugging, the process protective film is physically peeled off, followed by segmented semi-baking: first at 80℃ for 30 min, then at 110℃ for 30 min, with a temperature change rate of 0.8℃ / min; then, the plate is successively ground using 600-mesh abrasive belt at a current of 1.5 A and a speed of 2 m / min; after grinding, it is baked at 150℃ for 30 min for post-curing, with a temperature change rate of 0.8℃ / min, and then cooled to 80℃ and allowed to cool naturally to room temperature; finally, electroplating is performed to fill the gaps using an acidic sulfate copper plating process, with a plating solution composition of 200 g / L copper sulfate, 60 g / L sulfuric acid, and 65 mg / L chloride ions, and a current density of 2.2 A / dm³. 2 The plating bath temperature was 22℃, the electroplating time was 30 minutes, and the air stirring speed was 2.5 m / s. 3 / h, to achieve metallization of the hole opening and flatness of the board surface, resulting in a resin-filled PCB with no residual adhesive.

[0028] Comparative Example 1 This comparative example is based on Example 1, but the plasma pretreatment process step is omitted. Specifically: The PCB was dried at 160℃ for 2.5 hours, and then Y314AC process protective film was applied to both sides of the PCB at a speed of 1 m / min, a temperature of 110℃, and a pressure of 6 kg / cm². 2Next, laser ablation was performed with the following parameters: suction pressure -8 kPa, aperture 18 μm, energy 14*6*4, reference 18 mJ, pulse width: 14 μs (first pulse), 6 μs (second pulse), 4 μs (third pulse), pulse count 1*1*2 shots, photomask level 5. After ablation, ultrasonic cleaning was performed. Subsequently, resin plugging was performed with a vacuum of 18773 Pa, plugging pressure of 84 kgf, and scraper speed of 4.82 mm / s. After plugging, the process protective film was physically peeled off, and segmented semi-baking was performed, first baking at 80℃ for 30 minutes. Then, bake at 110℃ for 30 minutes, with a temperature change rate of 0.8℃ / min; then grind the plate sequentially using 600-mesh and 800-mesh non-woven fabrics, with a current of 1.5A and a speed of 2.5m / min; after grinding, bake at 150℃ for 30 minutes for post-curing, with a temperature change rate of 0.8℃ / min, then cool to 80℃ and allow to cool naturally to room temperature; finally, perform electroplating leveling treatment using an acidic sulfate copper plating process, with a plating solution composition of 200g / L copper sulfate, 60g / L sulfuric acid, and 65mg / L chloride ions, and a current density of 2.2A / dm³. 2 The plating bath temperature was 22℃, the electroplating time was 30 minutes, and the air stirring speed was 2.5 m / s. 3 / h, to achieve metallization of the hole openings and flatness of the board surface, resulting in a resin-filled PCB.

[0029] Test case

[0030] Test Example 1: Comparative test of copper reduction and copper thickness uniformity after electroplating using grinding method.

[0031] Take three identical PCB boards, 28 pieces in each group, and complete the double-sided lamination, laser hole burning, plasma pretreatment, resin hole plugging, physical peeling process protective film and semi-baking process according to the process steps in Examples 1 to 3. Then, perform board grinding. Use a copper thickness measuring instrument to measure the copper thickness before and after grinding and calculate the copper reduction. Then, all groups are subjected to post-curing and electroplating leveling treatment with the same parameters. Measure the copper thickness at 144 random points on the board surface after electroplating again and calculate the standard deviation of copper thickness. The monitoring results are shown in Tables 1 to 3.

[0032] Table 1:

[0033] Table 2:

[0034] Table 3:

[0035] As shown in Tables 1 to 3, when using non-woven fabric for grinding, the average copper reduction is much lower than that of ceramic brushes and leveling machines. The standard deviation of the copper reduction is also significantly smaller. This indicates that non-woven fabric grinding removes less copper thickness from the board surface and achieves better uniformity. It can precisely control the copper reduction depth during the grinding process, avoiding uneven copper thickness caused by excessive grinding. Considering that the aperture interface has been cleaned and activated after plasma pretreatment, choosing non-woven fabric for gentle grinding can ensure board surface flatness while maximizing copper thickness retention. In contrast, ceramic brushes and leveling machines have higher average copper reduction values ​​and larger standard deviations, resulting in poor copper uniformity and a tendency for excessive copper reduction in some areas and residual adhesive in others, which can negatively impact the subsequent electroplating filling effect.

[0036] Test Example 2: Basic Reliability Test.

[0037] Twenty-eight PCB boards manufactured according to the process described in Example 1 were subjected to flying probe testing, reflow soldering testing, thermal stress testing, and solderability testing in sequence. The flying probe testing used a 250V test voltage to measure conduction resistance and insulation resistance. The reflow soldering testing employed a stepped temperature profile of 165℃, 170℃, 185℃, 225℃, 235℃, 250℃, 265℃, and 270℃. After three reflow soldering cycles, the resin-copper interface and the state of the electroplated layer were observed by cutting the edge. The thermal stress test was conducted in a 288℃ solder bath for 10 seconds each time, for a total of three times, observing the appearance and internal structure of the PCB board. The solderability test was conducted in a 255℃ solder bath for 5 seconds to observe the solder adhesion to the pads and the bonding strength of the electroplated layer. The test results are shown in Table 4. Figure 5 and Figure 6 As shown.

[0038] Table 4:

[0039] Through Table 4 and Figure 5 It can be seen that the PCB board prepared using the process in Example 1 meets all the reliability indicators of the test standard. The process of using non-woven fabric grinding combined with plasma pretreatment does not introduce additional structural defects to the PCB. The interface between the copper hole and the resin is stable, the electroplating layer has good adhesion, and the process parameters of each step are reasonably matched. The basic reliability of the prepared PCB board can meet the requirements of production and use.

[0040] Test Example 3: Comparison Test of Plasma Pretreatment Effects Two identical PCB boards, 28 pieces in each group, were selected. Group A was processed according to the process steps in Example 1, and Group B was processed according to the process steps in Comparative Example 1. XPS analysis of the copper surface at the via opening, interfacial shear strength testing, thermal cycling testing, via indentation depth testing, and electroplating adhesion testing were performed on both groups of PCB boards. XPS analysis was used to test the Cu2p3 / 2 binding energy. Interfacial shear strength testing was conducted using a universal testing machine. Thermal cycling testing was performed for 1000 cycles within a temperature range of -40 to 125°C. The via indentation depth was tested using a three-dimensional surface profilometer. Electroplating adhesion testing was conducted using the tape peeling method and the cross-cut test. The test results are shown in Table 5. Figure 7 .

[0041] Table 5:

[0042] Through Table 5 and Figure 7 As can be seen, after plasma pretreatment using the process described in Example 1, the Cu2p3 / 2 bonding energy of Group A corresponds to the characteristic peak of metallic Cu, indicating that the residual oxides on the copper surface at the orifice were effectively cleaned, avoiding the impact of oxide residues on subsequent bonding strength. In contrast, Group B, which did not use the corresponding plasma pretreatment process, had a significant CuO oxide layer on the copper surface at the orifice, resulting in poor surface wettability, which directly affected the bonding effect of the electroplated layer. In terms of interfacial shear strength, Group A showed a 25% improvement over Group B, indicating that plasma pretreatment can effectively improve the bonding strength between the resin and copper interface. After thermal cycling tests, the microcrack rate of Group A was much lower than that of Group B, and the orifice indentation depth was also smaller, indicating that after plasma pretreatment, the interface bonding at the orifice was more stable, and microcrack defects were less likely to occur during temperature changes, while the amount of material removed at the orifice was more controllable. Finally, after electroplating, the bonding strength of the electroplated layer in Group A was also better than that in Group B, and there was no problem of electroplated layer peeling off. This shows that the plasma pretreatment in Example 1 can effectively improve the orifice interface state, enhance the bonding reliability between the electroplated layer and the orifice interface, and the overall process effect is more suitable for the production requirements of high-end PCBs.

[0043] In summary, by adding a plasma pretreatment step after laser hole burning, combined with gentle non-woven fabric grinding, this application can precisely control the copper reduction depth, effectively clean the residual adhesive and copper oxides after laser blind hole processing, improve the cleanliness and activation effect of the hole interface, improve the wettability of the board surface, thereby increasing the bonding strength between the hole wall resin and the electroplated copper layer, reducing the probability of microcracks during thermal cycling, controlling the hole indentation depth, and ultimately ensuring the uniformity of copper thickness and the bonding force of the electroplated layer after electroplating. The resulting PCB board meets all reliability requirements and can adapt to the mass production needs of high-density, high-order blind hole PCBs.

[0044] The above description is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described or explained in this invention are implemented according to conventional methods in the art unless otherwise specified or limited.

Claims

1. A residue-free PCB resin via-filling process, characterized in that: Includes the following steps: St1: Apply a high-temperature resistant and acid / alkali resistant process protective film to both sides of the fully dried PCB; St2: Laser drilling is performed on the corresponding through holes to burn off the process protective film and expose the holes that need to be filled with resin. St3: The PCB after laser burning is placed into a vacuum plasma treatment equipment and pre-treated with process gas. After treatment, the temperature is lowered while maintaining vacuum conditions, and nitrogen is introduced to atmospheric pressure before removal. St4: Resin is used to plug the holes, then the process protective film is physically peeled off, and the resin is pre-cured using a segmented semi-baking process; St5: Use non-woven fabric to polish the overflowing resin at the through hole position to ensure the board surface is flat; St6: High-temperature post-baking is performed on the polished PCB board to complete the full curing of the resin; St7: Perform full-board electroplating to fill and level the PCB board after post-curing, achieving metallization of the holes and flatness of the board surface; The process gas is a mixture of oxygen and argon, wherein the volume percentage of oxygen in the mixture is 30% to 50%, and the volume percentage of argon is 50% to 70%.

2. The PCB resin via plugging process without residue according to claim 1, characterized in that: In step St1, the drying temperature of the PCB is 150-170°C, and the drying time is 2-3h; the film pasting speed of the process protection film is 1m / min, the film pasting temperature is 110°C, and the film pasting pressure is 6kg / cm 2 .

3. The method for resin-filled PCB vias without residue according to claim 1, characterized in that: In step St2, the parameters for laser drilling are: suction pressure -3 to -13 kPa, reference energy 18 mJ, aperture 18 μm, pulse width 14*6*4 μs, number of pulses 1*1*2 shots, photomask level 5, and ultrasonic cleaning after laser drilling.

4. The PCB resin via plugging process without residue according to claim 1, characterized in that: In step St3, the total flow rate of the process gas is 200-400 sccm; the parameters of the plasma treatment are: excitation power 500-800W, chamber pressure 50-200 mTorr, treatment temperature 45-65℃, treatment time 3-8 minutes; after treatment, the temperature is reduced to below 30℃.

5. The PCB resin via plugging process without residue according to claim 1, characterized in that: In step St4, the parameters for resin plugging are: vacuum degree 15000~25000Pa, scraper speed 3~7mm / s, plugging pressure 70~100kgf; the parameters for the segmented semi-baking process are: first bake at 80℃ for 30min, then bake at 110℃ for 30min for semi-baking, with a temperature change rate of 0.5~1℃ / min.

6. The PCB resin via plugging process without residue according to claim 1, characterized in that: In step St5, the grinding plate parameters for the nonwoven fabric are: 600-800 mesh nonwoven fabric, current 1.5A, speed 2.5m / min.

7. The PCB resin via plugging process without residue according to claim 1, characterized in that: In step St6, the parameters for the high-temperature baking are: baking at 150°C for 30 minutes, with a temperature change rate of 0.5 to 1°C / min, followed by natural cooling to room temperature after cooling down to 80°C.

8. The PCB resin via plugging process without residue according to claim 1, characterized in that: In step St7, the electroplating leveling adopts an acidic sulfate copper plating process. The plating solution composition is 180-220 g / L copper sulfate, 50-70 g / L sulfuric acid, and 50-80 mg / L chloride ions. The electroplating parameters are: current density 1.5-3.0 A / dm³. 2 The plating bath temperature is 20–25℃, the electroplating time is 20–40 min, and the air stirring speed is 2–3 m / s. 3 / h.

9. The application of the residue-free PCB resin via plugging process as described in any one of claims 1 to 8 in the manufacturing of high-density interconnect boards and multilayer stacked blind and buried via structure PCBs.

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