Circuit board high-density protective film surface treatment method and circuit board

Abstract

The application provides a circuit board high-density protective film surface treatment method and a circuit board. The circuit board high-density protective film surface treatment method comprises the following steps: obtaining a circuit board; placing the circuit board into a modified OSP solution for soaking, wherein the modified OSP solution comprises an alkyl amide benzimidazole composition, a transition metal salt, an organic acid solvent, a chelating agent and water; using a cooling circulation spraying device to spray the soaked circuit board; and drying the sprayed circuit board to obtain the circuit board. By the method, the heat resistance of a traditional organic compound film is improved, the stability of the metal-organic compound film itself is improved, a high-density metal-organic compound film is obtained to improve the protection of the copper surface, the wastewater discharge amount is reduced, energy saving and emission reduction are achieved, and the water recycling rate is improved.

Description

Technical Field

[0001] This invention relates to the field of circuit board surface treatment technology, and in particular to a method for surface treatment of a high-density protective film on circuit boards and a circuit board thereof. Background Technology

[0002] In the final production process of circuit boards, a copper surface protectant is generally used for surface treatment. This involves immersing the circuit board in an OSP (Organic Solderability Preservatives) solution to form a thin film of organic compound on the copper surface. The organic compound film is then washed and dried to allow it to adhere to the outer surface of the copper. This provides excellent protection for the circuitry and pads on the copper surface, effectively preventing rusting of the copper pads under normal conditions. It also improves the solderability of the copper pads, ensuring the quality of soldering between the copper pads and electronic components and effectively preventing components from detaching.

[0003] However, the water temperature during the washing process of organic compound films is easily affected by the external environment. For example, hot weather or the heat generated by the operation of the pump head can raise the water temperature. In addition, the heat resistance of organic compound films will deteriorate when exposed to high external temperatures. As a result, the high temperature water can easily damage the density of the organic compound film, thereby reducing the protective effect of the organic compound film on the copper surface. This, in turn, reduces the solderability of the copper surface of the solder pads to electronic components, causing the circuit board to easily detach during use. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for surface treatment of a high-density protective film for circuit boards with good copper surface protection and high solderability of solder pads, as well as the circuit board itself.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A method for surface treatment of a high-density protective film on a circuit board includes the following steps:

[0007] Obtain the circuit board;

[0008] The circuit board is immersed in a modified OSP solution, wherein the modified OSP solution comprises an alkylamide benzimidazole composition, a transition metal salt, an organic acid solvent, a chelating agent, and water.

[0009] The circuit board after soaking was sprayed with a cooling circulating spray equipment;

[0010] The circuit board after spray treatment is dried to obtain the circuit board.

[0011] In one embodiment, the step of spraying the immersed circuit board with a cooling circulating spray device includes the following specific steps:

[0012] The soaked circuit board is sent to the spray area of ​​the cooling circulation spray equipment; the circuit board is sprayed in sections through multiple nozzles in the spray area.

[0013] In one embodiment, the segmented spraying is divided into a buffer cooling section, a rapid cooling section, and a regenerative cooling section;

[0014] The temperature of the buffer cooling section is 15℃~20℃, the time is 5S~10S, and the flow rate of the sprayed water is 1.0kg / cm. 2 ~1.5kg / cm 2 ;

[0015] The temperature of the rapid cooling section is 8℃~12℃, the time is 3S~8S, and the flow rate of the sprayed water is 1.5kg / cm2-2.0kg / cm2.

[0016] The temperature of the reheating cooling section is 15℃~20℃, the time is 5S~10S, and the flow rate of the sprayed water is 2.0kg / cm2~2.5kg / cm2.

[0017] In one embodiment, the conveying speed of the cooling circulating spray device is 2 meters / minute to 4 meters / minute.

[0018] In one embodiment, the step of drying the circuit board after the spray treatment includes the following specific steps:

[0019] The circuit board after spraying is then dried by suction.

[0020] The circuit board, after being absorbed, is then dried by blowing.

[0021] In one embodiment, before the step of immersing the circuit board in the modified OSP solution and after the step of obtaining the circuit board, the surface treatment method for the high-density protective film on the circuit board further includes the following steps:

[0022] The circuit board is then subjected to surface cleaning treatment;

[0023] The circuit board after surface cleaning is subjected to surface micro-etching.

[0024] In one embodiment, the alkylamide benzimidazole composition comprises at least one of N-(3,4-dichlorophenyl)-1H-benzo[D]imidazol-2-carboxamide, N(1H-benzo[D]imidazol-2-yl)-2-methylbenzamide, N-(1H-benzo[D]imidazol-2-yl)-2,4-difluorobenzamide, and N-(1H-benzo[D]imidazol-2-yl)-4-fluorobenzamide.

[0025] In one embodiment, the transition metal salt includes at least one sulfate of copper, iron, nickel, cobalt, or manganese metals.

[0026] In one embodiment, the organic acid solvent includes at least one of formic acid, acetic acid, propionic acid, octanoic acid, heptanoic acid, acrylic acid, and aminosulfonic acid.

[0027] A circuit board is prepared using the surface treatment method for a high-density protective film on a circuit board as described in any one of the above-mentioned methods.

[0028] Compared with the prior art, the present invention has at least the following advantages:

[0029] 1. The above-mentioned surface treatment method for high-density protective films on circuit boards, due to the presence of alkylamide benzimidazole compositions, transition metal salts, organic acid solvents, chelating agents, and water in the modified OSP solution, allows the alkylamide benzimidazole compositions to form a high-density metal-organic compound film on the copper surface when the circuit board is immersed in the modified OSP solution, with the metal in the transition metal salt as the central ion. Combined with the use of organic acid solvents, chelating agents, and water, the alkylamide benzimidazole compositions and transition metal salts can form a high-density metal-organic compound film. Simultaneously, the generated high-density metal-organic compound film can improve the heat resistance of traditional organic compound films, thereby enhancing the stability of the metal-organic compound film itself. Then, a cooling circulating spray system is used. The circuit board is then sprayed after soaking to ensure that the temperature of the water sprayed from the cooling circulating spray equipment is low and constant. This ensures that the water temperature of the high-density metal-organic compound film is maintained within a constant range during the washing process, effectively preventing the water temperature from being easily disturbed by the external environment. This avoids the phenomenon where the water temperature rises during the washing process, which could damage the density of the metal-organic compound film. As a result, the high-density metal-organic compound film can be better adhered and fixed to the copper surface, thereby improving the protection of the copper surface and the solderability between the copper pads and electronic components. This ensures that the circuit board is less likely to detach during use.

[0030] 2. The above-mentioned high-density protective film surface treatment method for circuit boards uses a cooling circulating spraying equipment to spray the immersed circuit boards, which can cool and circulate the water multiple times. This can effectively save the amount of water added, thereby reducing the amount of wastewater discharged, which is not only energy-saving and emission-reducing, but also environmentally friendly. Attached Figure Description

[0031] 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.

[0032] Figure 1 This is a flowchart of a method for surface treatment of a high-density protective film on a circuit board according to an embodiment of the present invention;

[0033] Figure 2 This is a schematic diagram of the structure of a cooling circulation spray device according to an embodiment of the present invention from one direction;

[0034] Figure 3 for Figure 2 The enlarged view of point A shown below;

[0035] Figure 4 This is a structural diagram illustrating the connection between the buffer tank and the first cooling circulation component according to an embodiment of the present invention;

[0036] Figure 5 This is a schematic diagram of the structure of a conveying assembly according to an embodiment of the present invention;

[0037] Figure 6 This is a partial structural diagram of a conveying component according to an embodiment of the present invention;

[0038] Figure 7 This is a diagram showing the flow direction of fresh water entering the water tank according to one embodiment of the present invention.

[0039] 10. Cooling circulating spray equipment; 100. Frame; 110. Spraying area; 111. Buffer cooling section; 112. Rapid cooling section; 113. Regeneration cooling section; 200. Conveying assembly; 210. Conveying roller; 220. Driver; 230. Drive gear set; 240. Driven gear; 300. Cooling circulation assembly; 310. First cooling circulation component; 311. Intermediate pipe; 3111. Inlet; 312. Circulating pipe; 3121. Outlet; 320. Second cooling circulation component; 330. Third cooling circulation component; 400 500. First spray assembly; 610. Second spray assembly; 620. First buffer nozzle; 630. Second buffer nozzle; 640. First cooling nozzle; 650. Second cooling nozzle; 660. First reheat nozzle; 700. Second reheat nozzle; 711. Water tank; 712. Buffer tank; 713. First pump suction port; 714. First overflow tank; 720. Cooling tank; 721. Second pump suction port; 730. Reheat tank; 731. Third pump suction port; 732. Water inlet channel; 714. Third overflow tank. Detailed Implementation

[0040] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0041] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly attached to the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to limit the scope of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0043] This application provides a method for surface treatment of a high-density protective film on a circuit board, comprising the following steps: obtaining a circuit board; immersing the circuit board in a modified OSP solution, wherein the modified OSP solution comprises an alkylamide benzimidazole composition, a transition metal salt, an organic acid solvent, a chelating agent, and water; spraying the immersed circuit board with a cooling circulating spray device; and drying the sprayed circuit board to obtain the circuit board.

[0044] The aforementioned method for surface treatment of high-density protective films on circuit boards utilizes a modified OSP solution containing alkylamide benzimidazole compositions, transition metal salts, organic acid solvents, chelating agents, and water. When the circuit board is immersed in the modified OSP solution, the alkylamide benzimidazole compositions, with the metal in the transition metal salt as the central ion, along with the organic acid solvent, chelating agent, and water, allow the alkylamide benzimidazole compositions and transition metal salts to form a high-density metal-organic compound film on the copper surface. Simultaneously, the resulting high-density metal-organic compound film improves the heat resistance of traditional organic compound films, thereby enhancing the stability of the metal-organic compound film itself. Finally, a cooling circulating spray system is employed. The circuit boards are sprayed after soaking to ensure that the water temperature from the cooling circulating spray equipment is low and constant. This ensures that the water temperature of the high-density metal-organic compound film is maintained within a constant range during the washing process, effectively preventing the water temperature from being easily disturbed by the external environment. This avoids the phenomenon where the water temperature rises during the washing process, which could damage the density of the metal-organic compound film. This ensures that the high-density metal-organic compound film adheres better to the copper surface, thereby improving the protection of the copper surface and the solderability between the copper pads and electronic components. This also ensures that the circuit board is less likely to detach during use. Furthermore, the above-mentioned surface treatment method for the high-density protective film on circuit boards uses a cooling circulating spray equipment to spray the soaked circuit boards, allowing for multiple cooling cycles of the water. This effectively saves on the amount of water added, thereby reducing wastewater discharge, which is not only energy-saving and emission-reducing but also environmentally friendly.

[0045] Please see Figure 1 To better understand the technical solution and beneficial effects of this application, the following detailed description is provided in conjunction with specific embodiments. One embodiment of the high-density protective film surface treatment method for circuit boards includes some or all of the following steps:

[0046] S100. Obtain the circuit board for future use.

[0047] S200. The circuit board is immersed in a modified OSP solution, wherein the modified OSP solution comprises an alkylamide benzimidazole composition, a transition metal salt, an organic acid solvent, a chelating agent, and water.

[0048] It is understandable that, since the modified OSP solution contains alkylamide benzimidazole compositions, transition metal salts, organic acid solvents, chelating agents, and water, when the circuit board is immersed in the modified OSP solution, the alkylamide benzimidazole compositions can complex with the metal in the transition metal salt as the central ion on the copper surface to form the main body of the OSP film. This allows the alkylamide benzimidazole compositions and transition metal salts to form a highly dense metal-organic compound film on the copper surface. At the same time, the generated highly dense metal-organic compound film can also improve the heat resistance of traditional organic compound films, thereby improving the stability of the metal-organic compound film itself.

[0049] S300. The circuit board after soaking is sprayed with a cooling circulating spray device.

[0050] It is understandable that the water temperature after being treated by the cooling circulation spray equipment can be maintained within a relatively stable range, thus ensuring that the temperature of the water sprayed by the cooling circulation spray equipment is low and constant. This effectively ensures that the water temperature is not easily affected by the external environment during the water washing process, thereby avoiding the phenomenon that the high-density metal-organic compound film is prone to damage to the density of the metal-organic compound film due to the high water temperature during the water washing process. In this way, it can ensure that the high-density metal-organic compound film can better adhere and fix to the copper surface, thereby improving the protection of the copper surface, improving the solderability of the copper surface of the solder pads and electronic components, and ensuring that the circuit board is less likely to fall off during use.

[0051] S400. The circuit board after spraying is dried to obtain the circuit board, thereby removing the moisture from the circuit board and obtaining a dried circuit board.

[0052] The aforementioned method for surface treatment of high-density protective films on circuit boards utilizes a modified OSP solution containing alkylamide benzimidazole compositions, transition metal salts, organic acid solvents, chelating agents, and water. When the circuit board is immersed in the modified OSP solution, the alkylamide benzimidazole compositions, with the metal in the transition metal salt as the central ion, along with the organic acid solvent, chelating agent, and water, allow the alkylamide benzimidazole compositions and transition metal salts to form a high-density metal-organic compound film on the copper surface. Simultaneously, the resulting high-density metal-organic compound film improves the heat resistance of traditional organic compound films, thereby enhancing the stability of the metal-organic compound film itself. Finally, a cooling circulating spray system is employed. The circuit boards are sprayed after soaking to ensure that the temperature of the water sprayed from the cooling circulation spray equipment is low and constant. This ensures that the water temperature of the high-density metal-organic compound film is maintained within a constant range during the washing process, effectively preventing the water temperature from being easily disturbed by the external environment. This avoids the phenomenon that the high-density metal-organic compound film is prone to damage due to high water temperature during the washing process. As a result, the high-density metal-organic compound film can be better adhered and fixed to the copper surface, thereby improving the protection of the copper surface and the solderability between the copper pads and electronic components. This ensures that the circuit board is less likely to fall off during use.

[0053] Furthermore, the above-mentioned high-density protective film surface treatment method for circuit boards uses a cooling circulating spraying equipment to spray the immersed circuit boards, which can cool and circulate the water multiple times. This effectively saves the amount of water added, thereby reducing the amount of wastewater discharged, which is not only energy-saving and emission-reducing, but also environmentally friendly.

[0054] In this embodiment, the circuit board is immersed in the modified OSP solution for 40 to 90 seconds.

[0055] It should be noted that, compared to traditional water washing, spray equipment increases the water flow rate of the tank (6L / min) to maintain a relatively low water temperature when washing circuit boards, ensuring that the incoming water can effectively maintain the washing temperature. However, this application uses a cooling circulating spray equipment to spray the soaked circuit boards, which only requires controlling the water flow rate of the tank to 4L / min to achieve the water washing cooling effect. This effectively reduces water consumption and thus greatly reduces wastewater discharge, achieving energy saving, emission reduction, and environmental protection.

[0056] In one embodiment, the step of spraying the immersed circuit board with a cooling circulating spray device includes the following specific steps: sending the immersed circuit board to the spray area of ​​the cooling circulating spray device; and spraying the circuit board in segments through multiple nozzles in the spray area.

[0057] It is understandable that the cooling circulation spray equipment is equipped with spray zones to allow the soaked circuit boards to be delivered to these zones. Multiple nozzles within the spray zones then spray cooling water from the equipment onto the high-density metal-organic compound (MOC) film, achieving rapid cooling and ensuring the high density of the MOC film structure. Furthermore, the water jets from the nozzles are fan-shaped, ensuring a large spray area for enhanced cooling and a large contact surface between the spray water and the MOC film. This effectively disperses the water pressure and prevents the water from penetrating the MOC film structure.

[0058] Please see Figures 2 to 3 In one embodiment, the cooling circulation spray device 10 includes a frame 100, a conveying assembly 200, a cooling circulation assembly 300, a first spraying assembly 400, and a second spraying assembly 500. The frame 100 has a connected spraying area 110 and a water tank 700. The water tank 700 is located below the spraying area 110 and is used to hold water. The cooling circulation assembly 300 is located within the water tank 700 and is used to cool the water in the water tank 700 to maintain the water in the water tank 700 at a preset temperature. The conveying assembly 200 is movably disposed within the spraying area 110 and is used to convey the circuit board. The first spraying assembly 400 and the second spraying assembly 500 are located on opposite sides of the spraying area 110, and are used to spray water from the water tank 700 onto both sides of the circuit board.

[0059] It is understandable that, since the first spray assembly 400 and the second spray assembly 500 are located on both sides of the spray area 110, the first spray assembly 400 and the second spray assembly 500 can simultaneously spray the cooled water in the water tank 700 onto both sides of the circuit board, so as to achieve rapid cooling of the high-density metal-organic compound film covering the copper surface of the circuit board. This can effectively protect the density of the high-density metal-organic compound film, thereby ensuring the integrity of the high-density metal-organic compound film structure, and thus improving the protection of the copper surface by the high-density metal-organic compound film and the solderability of the copper surface of the pads.

[0060] Please see Figure 2 In one embodiment, the segmented spraying is divided into a buffer cooling section 111, a rapid cooling section 112, and a regenerative cooling section 113; the temperature of the buffer cooling section 111 is 15℃~20℃, the time is 5S~10S, and the flow rate of the sprayed water is 1.0kg / cm2~1.5kg / cm2; the temperature of the rapid cooling section 112 is 8℃~12℃, the time is 3S~8S, and the flow rate of the sprayed water is 1.5kg / cm2-2.0kg / cm2; the temperature of the regenerative cooling section 113 is 15℃~20℃, the time is 5S~10S, and the flow rate of the sprayed water is 2.0kg / cm2~2.5kg / cm2.

[0061] It is understandable that the segmented spraying is divided into a buffer cooling section 111, a rapid cooling section 112, and a regenerative cooling section 113 to achieve different segmented cooling of the circuit board, so that the high-density metal-organic compound film can be cooled well, thereby ensuring that the high-density metal-organic compound film can be better adhered and fixed on the copper surface, so as to provide better protection for the copper surface.

[0062] Specifically, by setting the temperature of the buffer cooling section 111 to 15℃~20℃, the time to 5S~10S, and the flow rate of the sprayed water to 1.0kg / cm2~1.5kg / cm2, the water temperature in the buffer cooling section 111 is lower than that of room temperature water. This ensures a relatively small temperature drop upon entering the buffer cooling section 111, preventing the high-density metal-organic compound film from being unable to adapt to lower temperatures from higher room temperatures. This avoids a decrease in the migration rate of particles of alkylamide benzimidazole compositions and transition metal salts, thus preventing the high-density film from becoming too dense. The low density, porosity, and rough surface of high-density metal-organic compound films can lead to poor density, thus preventing the destruction of the high density of high-density metal-organic compound films. Water temperatures above 20°C not only easily cause the crystal nuclei of alkylamide benzimidazole compositions and transition metal salts spread on the copper surface to grow too quickly, thus destroying the high density structure of high-density metal-organic compound films, but also increase the solubility of alkylamide benzimidazole compositions, further destroying the high density structure of high-density metal-organic compound films. In other words, when the temperature of the circuit board after soaking is 15℃~20℃ in the buffer cooling section 111, the thin film of alkyl amide benzimidazole composition and transition metal salt that has just been spread on the copper surface can form relatively stable particles at 15℃~20℃. This effectively avoids the impact of high or low water washing temperature on the density of the high-density metal-organic compound film, so that the high-density metal-organic compound film can form a semi-solid state in the buffer cooling section 111.

[0063] It is understood that after the processing of the buffer cooling section 111, the copper surface of the circuit board will form a semi-solid, highly dense metal-organic compound film. That is, at this time, the outer surface of the highly dense metal-organic compound film attached to the copper surface has become solid, while the interior of the highly dense metal-organic compound film is semi-liquid or liquid. In order to allow the interior of the highly dense metal-organic compound film, which is semi-liquid or liquid, to be cooled to form a dense structure, this application sets the temperature of the rapid cooling section 112 to 8℃~12℃, the time to 3S~8S, and the flow rate of the sprayed water to 1.5kg / cm2-2.0kg / cm2. Thus, the temperature of the 8℃~12℃ section is... The sprayed water serves two purposes: firstly, it continues to cool the semi-solid, highly dense metal-organic compound film, preventing the internal energy of the film from diffusing outwards and affecting the cooled and solidified outer surface; secondly, it ensures that the sprayed water at 8°C to 12°C reaches a relatively low temperature inside the film, thus better suppressing the migration rate of alkylamide benzimidazole compositions and transition metal salt particles within the film. This results in a uniform and highly dense metal-organic compound film forming both on the outer surface and inside.

[0064] It is understandable that when the circuit board exits the rapid cooling section 112, the high-density metal-organic compound film is solidified both internally and externally. It then enters the reheat cooling section 113, where the temperature is controlled at 15℃~20℃ for 5S~10S, and the spray water flow rate is 2.0kg / cm²~2.5kg / cm². This process, by increasing the temperature of the spray water in the reheat cooling section 113, can quickly remove excess modified OSP solution remaining on the high-density metal-organic compound film. Furthermore, it avoids the situation where the circuit board directly enters a higher temperature from a lower temperature, where a large temperature difference can easily cause the high-density... Uneven heating of metal-organic compound (MOC) films or circuit boards can cause localized expansion and bulging of the high-density MOC film, affecting its structural density. After passing through the reheat cooling stage 113, the copper surface of the circuit board is covered with a relatively moderately thick high-density MOC film. This allows the high-density MOC film to be quickly removed by flux during subsequent high-temperature soldering of the pads, exposing clean pads. This enables the pads to bond with molten solder in a very short time, forming strong solder joints and ensuring a strong solder joint between the pads and electronic components.

[0065] It should be noted that the rapid cooling section 112 or the reheat cooling section 113 is performed first primarily because the temperature of the rapid cooling section 112 is relatively lower than that of the buffer cooling section 111. The density of the metal-organic compound film newly formed on the copper surface is easily affected by the lower temperature, resulting in lower density, porosity, and a rough surface. Furthermore, the flow rate of the sprayed water in the rapid cooling section 112 is greater than that in the buffer cooling section 111. Since the metal-organic compound film has just adhered to the copper surface and is relatively thin, using a higher flow rate of sprayed water would be detrimental. During spraying, the water flow can easily break through the metal-organic compound (MOC) film or cause uneven thickness, thus affecting the density of the MOC film and reducing its protective effect on the copper surface. Similarly, if the reheat cooling section 113 is performed first, the flow rate of the sprayed water in the reheat cooling section 113 is 1.5 kg / cm²-2.0 kg / cm², which is greater than the flow rate of the sprayed water in the buffer cooling section 111 (1.0 kg / cm²-1.5 kg / cm²), making the structure of the MOC film more susceptible to damage. Therefore, this application first applies the circuit board to the buffer cooling section 111, then the rapid cooling section 112, and finally the reheat cooling section 113. This allows the MOC film to form a dense and uniform MOC film in a shorter cooling time, ensuring a highly dense and uniform MOC film.

[0066] In one embodiment, the spray area 110 is divided into a buffer cooling area, a rapid cooling area, and a reheat cooling area to achieve segmented spraying of the circuit board.

[0067] Please see Figure 2 and Figure 3In one embodiment, the multiple nozzles can be divided into a first buffer nozzle 610, a first cooling nozzle 630, a first reheating nozzle 650, a second buffer nozzle 620, a second cooling nozzle 640, and a second reheating nozzle 660. The water tank 700 includes a buffer tank 710, a cooling tank 720, and a reheating tank 730. The buffer cooling section 111 includes a first buffer connecting pipe, a second buffer connecting pipe, and the first buffer nozzle 610 and the second buffer nozzle 620. The first buffer nozzle 610 is connected to the buffer tank 710 through the first buffer connecting pipe, and the second buffer nozzle 620 is connected to the buffer tank 710 through the second buffer connecting pipe, so as to achieve slow cooling of the high-density metal-organic compound film by the buffer cooling section 111. The rapid cooling section 112 includes a first cooling connecting pipe, a second cooling connecting pipe, and a second cooling connecting pipe. The cooling section 112 includes a first cooling connecting pipe, a second cooling connecting pipe, a first cooling nozzle 630, and a second cooling nozzle 640. The first cooling nozzle 630 is connected to the cooling tank 720 via the first cooling connecting pipe, and the second cooling nozzle 640 is connected to the cooling tank 720 via the second cooling connecting pipe, so as to achieve rapid cooling of the high-density metal-organic compound film by the rapid cooling section 112. The reheating cooling section 113 includes a first reheating connecting pipe, a second reheating connecting pipe, a first reheating nozzle 650, and a second reheating nozzle 660. The first reheating nozzle 650 is connected to the reheating tank 730 via the first reheating connecting pipe, and the second reheating nozzle 660 is connected to the reheating tank 730 via the second reheating connecting pipe, so as to achieve slow cooling and reheating of the high-density metal-organic compound film by the reheating cooling section 113.

[0068] Please see Figure 3 In one embodiment, the cooling circulation assembly 300 includes a first cooling circulation component 310, a second cooling circulation component 320, and a third cooling circulation component 330. The first cooling circulation component 310 is disposed within the buffer tank 710, the second cooling circulation component 320 is disposed within the cooling tank 720, and the third cooling circulation component 330 is disposed within the reheat tank 730. When the first cooling circulation component 310, the second cooling circulation component 320, and the third cooling circulation component 330 are connected to an external refrigeration pump assembly, they can individually cool the water in the buffer tank 710, the cooling tank 720, and the reheat tank 730, respectively. This achieves a better segmented spraying effect, better protects the thickness and density of the high-density metal-organic compound film during cooling, and ensures a thinner and more dense high-density metal-organic compound film, thereby ensuring a thinner and lighter circuit board to better meet market demands.

[0069] Please see Figure 4 In one embodiment, the first cooling circulation component 310 includes a central tube 311 and a surrounding tube 312 connected to each other. The central tube 311 has an inlet 3111, and the surrounding tube 312 has an outlet 3121. The surrounding tube 312 is arranged around the outer surface of the central tube 311. Both the inlet 3111 and the outlet 3121 are used to connect with an external refrigeration component to ensure the cooling effect of the first cooling circulation component 310 on the water in the buffer tank 710. Similarly, the second cooling circulation component 320 and the third cooling circulation component 330 have the same structure as the first cooling circulation component 310 to ensure the cooling effect of the second cooling circulation component 320 on the water in the cooling tank 720 and the reheat tank 730.

[0070] Furthermore, since the cooling circulation assembly 300 is located below the conveying assembly 200, it can effectively cool the conveying assembly 200 and the circuit board on it. On the one hand, it can effectively dissipate heat from the conveying assembly 200, and on the other hand, it can quickly cool the circuit board on the conveying assembly 200 to ensure the cooling effect of the high-density metal-organic compound film. In addition, the cooling water sprayed by the first spray assembly 400 and the second spray assembly 500 can also provide good lubrication for the operation of the conveying assembly 200 itself, effectively avoiding wear on the parts inside the conveying assembly 200. Thus, not only is the energy utilization rate of the cooling circulation assembly 300 improved, but the wear on the parts inside the conveying assembly 200 is also reduced, thereby extending the service life of the conveying assembly 200.

[0071] Specifically, the first cooling circulation component 310, the buffer tank 710, the second cooling circulation component 320, the cooling tank 720, and the second cooling circulation component 320 and the reheat tank 730 are all located below the conveying assembly 200, while the first buffer nozzle 610, the first cooling nozzle 630, the first reheat nozzle 650, the second buffer nozzle 620, the second cooling nozzle 640, and the second reheat nozzle 660 are all located above the conveying assembly 200. This arrangement ensures that the first buffer nozzle 610, the first cooling nozzle 650, the second buffer nozzle 620, the second cooling nozzle 640, and the second reheat nozzle 660 are all located above the conveying assembly 200. The water sprayed from nozzle 630, first reheating nozzle 650, second buffer nozzle 620, second cooling nozzle 640, and second reheating nozzle 660 will be recycled and fall into the corresponding buffer tank 710, cooling tank 720, and reheating tank 730. In this way, water recycling is achieved, which improves the water recycling rate. Furthermore, by controlling the water inlet flow rate of water tank 700 to 4L / min, the water washing and cooling effect can be achieved, thereby effectively reducing water consumption and significantly reducing wastewater discharge, achieving energy conservation, emission reduction, and environmental protection.

[0072] It is understandable that, since copper vias are formed in the pads on the circuit board, when the circuit board is immersed in OSP solution, the OSP solution will also form a highly dense metal-organic compound film on the inner wall of the copper vias. When the circuit board passes through the buffer cooling section 111, the surface of the highly dense metal-organic compound film has become semi-solid, that is, the semi-solid state is relatively unstable. If the first cooling nozzle 630 and the second cooling nozzle 640 spray force on the circuit board is large, it is easy to penetrate the surface of the semi-solid highly dense metal-organic compound film, thereby causing the highly dense metal-organic compound film to crack. Therefore, this application uses the first cooling nozzle 630 and the second cooling nozzle 640, both of which are inclined within the spray area 110, so that the first cooling nozzle 630 and the second cooling nozzle 640 can maintain an inclined angle with the circuit board to be pre-cooled. In this way, the water sprayed from the first cooling nozzle 630 and the second cooling nozzle 640 has a relatively small jet force on the circuit board, allowing the water to enter the inner wall of the copper through hole well, so as to quickly cool the high-density metal-organic compound film on the inner wall of the copper through hole, and the high-density metal-organic compound film is less likely to crack. It is worth mentioning that when the first cooling nozzle 630 and the second cooling nozzle 640 are tilted within the spray area 110, the water sprayed from the first cooling nozzle 630 and the second cooling nozzle 640 is blocked by the circuit board and the inner wall of the copper through-hole, causing it to splash on the surface of the circuit board and form multiple small water droplets. These droplets, under the influence of gravity, will fall back onto the surface of the circuit board, thereby achieving micro-cooling of the highly dense metal-organic compound film. This is especially true when the first cooling nozzle 630 and the second cooling nozzle 640 are tilted within the spray area 110. When the water sprayed from nozzle 640 hits the inner wall of the copper through-hole, multiple water droplets are reflected off the inner wall and reused. This ensures a more comprehensive and better cooling effect on the dense metal-organic compound film on the inner wall of the copper through-hole, and improves the energy utilization rate of the sprayed water. If the first cooling nozzle 630 and the second cooling nozzle 640 are not tilted, the water sprayed from the first cooling nozzle 630 and the second cooling nozzle 640 passes directly through the copper through-hole, resulting in lower energy utilization rate of the sprayed water and a slower and less effective cooling effect on the dense metal-organic compound film on the inner wall of the copper through-hole.

[0073] Please see Figure 3In one embodiment, the first cooling nozzle 630 and the second cooling nozzle 640 are staggered to avoid the water sprayed by the first cooling nozzle 630 and the second cooling nozzle 640 not being on the corresponding sides of the circuit board. This ensures that the water sprayed by the first cooling nozzle 630 and the second cooling nozzle 640 is relatively dispersed on the circuit board, thereby avoiding the phenomenon that the circuit board is prone to denting and deformation.

[0074] In one embodiment, the tilt angle of the first cooling nozzle 630 is the same as that of the second cooling nozzle 640 to ensure that the circuit board is subjected to relatively uniform force on both sides of the rapid cooling section 112. This not only ensures that the cooling speed on both sides of the circuit board is relatively uniform to obtain a highly dense metal-organic compound film with good uniformity, but also avoids the circuit board from easily bending to ensure that a high-quality circuit board is obtained.

[0075] In one embodiment, the tilt angle between the first cooling nozzle 630 and the spray area 110 is 5° to 10° to ensure that the angle between the water sprayed by the first cooling nozzle 630 and the circuit board is appropriate. This not only avoids the phenomenon that the spraying force of the first cooling nozzle 630 damages the high-density metal-organic compound film, but also ensures more comprehensive and faster cooling of the high-density metal-organic compound film on the inner wall of the copper through hole, and also improves the energy utilization rate of the spray water.

[0076] In one embodiment, the tilt angle between the second cooling nozzle 640 and the spray area 110 is 5° to 10° to ensure that the angle between the water sprayed by the second cooling nozzle 640 and the circuit board is appropriate. This not only avoids the phenomenon that the spraying force of the second cooling nozzle 640 damages the high-density metal-organic compound film, but also ensures more comprehensive and faster cooling of the high-density metal-organic compound film on the inner wall of the copper through hole, and also improves the energy utilization rate of the spray water.

[0077] Please see Figure 7In one embodiment, the water tank 700 has multiple pump inlets and multiple overflow channels. The multiple pump inlets are a first pump inlet 711, a second pump inlet 721, and a third pump inlet 731. The multiple overflow channels are a first overflow channel 712, a second overflow channel 713, and a third overflow channel 714. The first pump inlet 711 is located in the buffer tank 710, the second pump inlet 721 is located in the cooling tank 720, and the third pump inlet 731 is located in the reheat tank 730. The first overflow channel 712 is used to discharge wastewater, and the first overflow channel 712 and the second overflow channel 713 are respectively located in the buffer tank. The buffer tank 710 is connected to the cooling tank 720 via the second overflow tank 713 on both sides of the 710. The cooling tank 720 is connected to the reheat tank 730 via the third overflow tank 714. Thus, when the first pump suction port 711, the second pump suction port 721, and the third pump suction port 731 are powered by an external power source, fresh water can flow in from the water inlet channel 732 of the reheat tank 730, then enter the cooling tank 720 via the third overflow tank 714, then enter the second overflow tank 713 from the cooling tank 720, then flow into the buffer tank 710, and partially flow out through the first overflow tank 712. In this way, the utilization rate of water in the water tank 700 can be greatly improved.

[0078] Please see Figure 7 In one embodiment, the heights of the first overflow tank 712, the second overflow tank 713, and the third overflow tank 714 increase sequentially to ensure that fresh water can enter the buffer tank 710 from the warming tank 730. It is worth mentioning that since the circuit board soaked in OSP solution enters the buffer tank 710 first, and the water recovered from the buffer tank 710 at this time contains excess OSP solution, the water in the buffer tank 710 is prone to becoming turbid after repeated use, so that the turbidity of the water in the buffer tank 710, cooling tank 720, and warming tank 730 decreases sequentially. In order to improve the water recycling rate of the cooling circulating spray equipment 10, this application reverses the direction in which the circuit board enters the cooling circulating spray equipment 10 and the direction of water flow in the water tank 700. This ensures that the water added to the cooling circulating spray equipment 10 flows from clean to turbid, thereby avoiding the turbid water in the buffer tank 710 from contaminating the water quality in the cooling tank 720 and the reheating tank 730. In other words, it effectively avoids serious cross-contamination of the water quality in the buffer tank 710, cooling tank 720 and reheating tank 730, thereby improving the water recycling rate of the cooling circulating spray equipment 10.

[0079] In one embodiment, the cooling circulation spray device 10 has a conveying speed of 2 m / min to 4 m / min, which, in conjunction with the use of multiple nozzles, can effectively achieve the segmented spraying effect of metal-organic compound films.

[0080] Please see Figure 5 and Figure 6 In one embodiment, the conveying assembly 200 further includes a conveying roller 210, a driver 220, a drive gear set 230, and a driven gear 240. The driver 220 is mounted on the frame 100, and the driven gear 240 is sleeved on the conveying roller 210. The power output end of the driver 220 is connected to the drive gear set 230, and the drive gear set 230 meshes with the driven gear 240, causing the driver 220 to drive the driven gear 240 through the drive gear set 230, thereby driving the conveying roller 210 to rotate relative to the frame 100. Further, the drive gear set 230 includes two meshing bevel gears, one of which meshes with the driven gear 240, which is a cylindrical gear. Furthermore, each conveyor roller 210 is spaced apart within the spray area 110 and forms multiple gaps. The second buffer nozzle 620, the second cooling nozzle 640, and the second reheating nozzle 660 are respectively disposed in each of the gaps to ensure that the second buffer nozzle 620, the second cooling nozzle 640, and the second reheating nozzle 660 can spray and cool the circuit board.

[0081] In one embodiment, the step of drying the circuit board after the spray treatment includes the following specific steps: performing a suction drying treatment on the spray-treated circuit board; and performing a blow drying treatment on the suction-dried circuit board to achieve the drying of the high-density metal-organic compound film.

[0082] First, a sponge roller is used to absorb moisture from both sides of the circuit board, quickly drying both sides of the high-density metal-organic compound film. Then, a fan is used to blow-dry the circuit board, effectively removing moisture from the pads of the high-density metal-organic compound film, thereby improving the drying efficiency. Furthermore, the sponge roller is made of PVA (polyvinyl alcohol) or PVC (polyvinyl chloride). Because PVA and PVC have excellent water absorption and are inexpensive, compared to the traditionally used PU sponge roller, this application improves the drying efficiency and significantly reduces costs while ensuring that the sponge roller does not scratch the high-density metal-organic compound film.

[0083] In one embodiment, after the step of blowing the dried circuit board, the circuit board is further subjected to a drying operation to remove moisture from the circuit board more quickly, thereby achieving a faster drying efficiency.

[0084] In one embodiment, before the step of immersing the circuit board in the modified OSP solution and after the step of obtaining the circuit board, the surface treatment method for the high-density protective film of the circuit board further includes the following steps: performing a surface cleaning treatment on the circuit board to effectively remove dirt, such as grease or impurities, so that the high-density metal-organic compound film can adhere well to the circuit board; performing a surface micro-etching treatment on the circuit board after surface cleaning to roughen the surface of the circuit board, thereby increasing the contact area between the high-density metal-organic compound film and the copper surface of the circuit board, so that the high-density metal-organic compound film can better adhere to the copper surface and improve the connection strength between the copper surface and the high-density metal-organic compound film.

[0085] In one embodiment, the modified OSP solution comprises the following parts by weight: 0.8 to 1.5 parts of an alkylamide benzimidazole composition, 0.5 to 1 part of a transition metal salt, 12 to 20 parts of an organic acid solvent, 1 to 2 parts of a chelating agent, and 80 to 90 parts of water, to ensure a highly dense metal-organic compound film of 0.2 to 0.4 micrometers on the circuit board.

[0086] In one embodiment, the alkylamide benzimidazole composition comprises at least one of N-(3,4-dichlorophenyl)-1H-benzo[D]imidazol-2-carboxamide, N-(1H-benzo[D]imidazol-2-yl)-2-methylbenzamide, N-(1H-benzo[D]imidazol-2-yl)-2,4-difluorobenzamide, and N-(1H-benzo[D]imidazol-2-yl)-4-fluorobenzamide.

[0087] It is understood that by combining N-(3,4-dichlorophenyl)-1H-benzo[D]imidazol-2-carboxamide, N-(1H-benzo[D]imidazol-2-yl)-2-methylbenzamide, N-(1H-benzo[D]imidazol-2-yl)-2,4-difluorobenzamide and N-(1H-benzo[D]imidazol-2-yl)-4-fluorobenzamide, amide bonds can be provided for alkylamide benzimidazole compositions, resulting in higher solubility of alkylamide benzimidazole compositions compared to traditional benzimidazole compositions, such as the polybenzimidazole used in patent number CN114453695A, which has lower solubility. Therefore, the alkylamide benzimidazole composition of this application is less prone to crystallization during film formation, ensuring that the alkylamide benzimidazole composition can form a high-density metal-organic compound film on the copper surface. At the same time, since the heat resistance of the alkylamide benzimidazole composition itself is not reduced and it can withstand lead-free soldering at >260°C, it can effectively improve the heat resistance of the high-density metal-organic compound film, thereby avoiding the damage to the density of the high-density metal-organic compound film caused by high water washing temperature.

[0088] It should be noted that the solubility of alkylamide benzimidazole compositions containing amide bonds is higher than that of traditional compositions, which increases the difficulty of washing highly dense metal-organic compound films. In other words, if a newly formed highly dense metal-organic compound film is washed directly with room temperature water, the alkylamide benzimidazole composition is likely to dissolve, thereby easily damaging the density of the film. However, when a newly formed highly dense metal-organic compound film is washed with cold water (below room temperature), the solubility of the alkylamide benzimidazole composition decreases, thus providing good protection for the structure of the film. Therefore, this application involves immediately subjecting the circuit board soaked in OSP solution to segmented spraying in a cooling circulation spraying device. This ensures that the newly formed high-density metal-organic compound film passes through a buffer cooling section at a temperature of 15℃~20℃ for 5S~10S, with a spray water flow rate of 1.0kg / cm²~1.5kg / cm². This allows the newly formed high-density metal-organic compound film to form relatively stable particles at 15℃~20℃, effectively preventing the high washing temperature from affecting the density of the high-density metal-organic compound film, thus ensuring the high-density metal-organic compound film... The film can form a semi-solid state in the buffer cooling section, and then enter the rapid cooling section at a temperature of 8℃~12℃ for 3S~8S. The flow rate of the sprayed water is 1.5kg / cm2-2.0kg / cm2 to ensure that a uniform and dense structure can be formed inside the high-density metal-organic compound film. Finally, it enters the reheat cooling section, which can quickly remove excess modified OSP solution remaining on the high-density metal-organic compound film, so as to ensure that a high-density metal-organic compound film of relatively moderate thickness can be coated on the copper surface of the circuit board, thereby improving the protection of the copper surface.

[0089] In one embodiment, the transition metal salt includes at least one sulfate of copper, iron, nickel, cobalt, and manganese metals. The added transition metal salt can react with the alkylamide benzimidazole composition, so that the alkylamide benzimidazole composition can form a highly dense metal-organic compound film on the copper surface of the circuit board with copper, iron, nickel, cobalt, or manganese metals in the transition metal salt as the central ion.

[0090] In one embodiment, the organic acid solvent includes at least one selected from formic acid, acetic acid, propionic acid, octanoic acid, heptanoic acid, acrylic acid, and aminosulfonic acid. In a preferred embodiment, the organic acid solvent is a mixture of octanoic acid, heptanoic acid, and formic acid.

[0091] In one embodiment, the chelating agent includes at least one of ethylenediamine, diethylenetriamine, ethanolamine, citric acid, malic acid, EDTA (ethylenediaminetetraacetic acid), EDTMPA (ethylenediaminetetramethylenephosphonica acid), and ATMP (aminotrimethylenephosphonic acid).

[0092] In a preferred embodiment, the chelating agent is a mixture of EDTA, EDTMPA, and ATMP. It is understood that, on the one hand, EDTA, EDTMPA, and ATMP can provide better complexation conditions for the alkylamide benzimidazole composition and transition metal salts; on the other hand, EDTMPA and ATMP have good scale inhibition effects. When the cooling circulating spray equipment sprays the immersed circuit board, the spray water can wash excess EDTMPA from the circuit board into the water tank. Then, the spray water collected in the water tank is sprayed back onto the circuit board through the nozzles, thus achieving the recycling of the spray water in the water tank. It is worth mentioning that, because the collected spray water is easily clogged when repeatedly recycled, scale can easily form in the nozzles and the pipes connecting the water tank and the nozzles. However, due to the good scale inhibition effect of EDTMPA and ATMP, scale formation in the nozzles and the pipes connecting the nozzles can be effectively prevented, ensuring smooth flow between the water collected in the water tank and the nozzles, thereby improving the water recycling rate.

[0093] It should also be noted that when the circuit board enters the buffer cooling section, the spray water collected in the water tank within the buffer cooling section is relatively turbid. Since the chelating agents in the modified OSP solution contain EDTMPA and ATMP, they can effectively ensure the normal operation of the first and second buffer nozzles for a long time, thus avoiding clogging of the first and second buffer nozzles and resulting in poor cooling effect on the metal-organic compound film. In this way, not only is the cooling circulation spray equipment well-cooled, but the cleaning cycle of the cooling circulation spray equipment is also extended, thereby effectively saving the amount of water added and reducing the amount of wastewater discharged. This not only saves energy and reduces emissions but is also environmentally friendly.

[0094] This application also provides a circuit board prepared using the high-density protective film surface treatment method described in any of the above claims. The method of this application can obtain a high-density metal-organic compound film on the surface of the circuit board, which can improve the heat resistance and density of the high-density metal-organic compound film, thereby improving the protection of the copper surface of the circuit board and the number of reflow soldering cycles.

[0095] In one embodiment, the thickness of the high-density metal-organic compound film is 0.2 micrometers to 0.4 micrometers, so that a high-density metal-organic compound film of moderate thickness is obtained on the copper surface of the circuit board. In this way, when the pads are subsequently soldered at high temperature, the high-density metal-organic compound film can be quickly removed by the flux to expose clean pads. This allows the pads to bond with molten solder in a very short time to form a strong solder joint, thereby achieving a strong solder joint between the pads and electronic components.

[0096] Compared with the prior art, the present invention has at least the following advantages:

[0097] 1. The above-mentioned surface treatment method for high-density protective films on circuit boards, due to the presence of alkylamide benzimidazole compositions, transition metal salts, organic acid solvents, chelating agents, and water in the modified OSP solution, allows the alkylamide benzimidazole compositions to form a high-density metal-organic compound film on the copper surface when the circuit board is immersed in the modified OSP solution, with the metal in the transition metal salt as the central ion. Combined with the use of organic acid solvents, chelating agents, and water, the alkylamide benzimidazole compositions and transition metal salts can form a high-density metal-organic compound film. Simultaneously, the generated high-density metal-organic compound film can improve the heat resistance of traditional organic compound films, thereby enhancing the stability of the metal-organic compound film itself. Then, a cooling circulating spray system is used. The circuit board is then sprayed after soaking to ensure that the temperature of the water sprayed from the cooling circulating spray equipment is low and constant. This ensures that the water temperature of the high-density metal-organic compound film is maintained within a constant range during the washing process, effectively preventing the water temperature from being easily disturbed by the external environment. This avoids the phenomenon where the water temperature rises during the washing process, which could damage the density of the metal-organic compound film. As a result, the high-density metal-organic compound film can be better adhered and fixed to the copper surface, thereby improving the protection of the copper surface and the solderability between the copper pads and electronic components. This ensures that the circuit board is less likely to detach during use.

[0098] 2. The above-mentioned high-density protective film surface treatment method for circuit boards uses a cooling circulating spraying equipment to spray the immersed circuit boards, which can cool and circulate the water multiple times. This can effectively save the amount of water added, thereby reducing the amount of wastewater discharged, which is not only energy-saving and emission-reducing, but also environmentally friendly.

[0099] The following are some specific examples. When %, it refers to a percentage by weight. It should be noted that the following examples do not exhaustively list all possible scenarios, and unless otherwise specified, the materials used in the following examples are commercially available.

[0100] Example 1

[0101] Obtain a circuit board; perform surface cleaning on the circuit board; perform surface micro-etching on the cleaned circuit board; immerse the circuit board in a modified OSP solution, wherein the modified OSP solution comprises 0.8 parts N-(3,4-dichlorophenyl)-1H-benzo[D]imidazolium-2-carboxamide, 0.5 parts copper sulfate, 12 parts formic acid, 1 part diethylenetriamine and 80 parts water;

[0102] The soaked circuit board is conveyed to the spray area of ​​the cooling circulation spray equipment via a conveying assembly; the conveying speed of the conveying assembly is controlled at 2 meters per minute. The circuit board is sprayed in segments through multiple nozzles in the spray area. The circuit board passes through the buffer cooling section at a temperature of 15°C for 5 seconds with a spray water flow rate of 1.0 kg / cm²; then through the rapid cooling section at a temperature of 8°C for 3 seconds with a spray water flow rate of 1.5 kg / cm²; finally, through the rewarming cooling section at a temperature of 15°C for 5 seconds with a spray water flow rate of 2.0 kg / cm².

[0103] The circuit board after spraying is then dried by suction; the dried circuit board is then blow-dried to obtain a circuit board with a high-density protective film.

[0104] Example 2

[0105] Obtain a circuit board; perform surface cleaning on the circuit board; perform surface micro-etching on the cleaned circuit board; immerse the circuit board in a modified OSP solution, wherein the modified OSP solution comprises 0.2 parts N-(1H-benzo[D]imidazol-2-yl)-2-methylbenzamide and 0.8 parts N-(3,4-dichlorophenyl)-1H-benzo[D]imidazol-2-carboxamide, 0.5 parts copper sulfate and 0.3 parts nickel sulfate, 12 parts formic acid and 4 parts octanoic acid, 1.5 parts EDTA and 85 parts water;

[0106] The soaked circuit board is conveyed to the spray area of ​​the cooling circulation spray equipment via a conveying assembly; the conveying speed of the conveying assembly is controlled at 3 meters per minute, and the circuit board is sprayed in segments through multiple nozzles in the spray area. The circuit board passes through the buffer cooling section at a temperature of 18°C ​​for 8 seconds with a spray water flow rate of 1.2 kg / cm²; then through the rapid cooling section at a temperature of 10°C for 5 seconds with a spray water flow rate of 1.8 kg / cm²; finally, through the rewarming cooling section at a temperature of 17°C for 8 seconds with a spray water flow rate of 2.2 kg / cm².

[0107] The circuit board after spraying is then dried by suction; the dried circuit board is then blow-dried to obtain a circuit board with a high-density protective film.

[0108] Example 3

[0109] Obtain a circuit board; perform surface cleaning on the circuit board; perform surface micro-etching on the cleaned circuit board; immerse the circuit board in a modified OSP solution, wherein the modified OSP solution comprises 1.5 parts N-(1H-benzo[D]imidazol-2-yl)-2,4-difluorobenzamide, 1 part cobalt sulfate, 20 parts heptanoic acid, 2 parts EDTA and 90 parts water;

[0110] The soaked circuit board is conveyed to the spray area of ​​the cooling circulation spray equipment via a conveying assembly; the conveying speed of the conveying assembly is controlled at 4 meters per minute. The circuit board is sprayed in segments through multiple nozzles in the spray area. The circuit board passes through the buffer cooling section at a temperature of 20°C for 10 seconds with a spray water flow rate of 1.5 kg / cm²; then through the rapid cooling section at a temperature of 12°C for 8 seconds with a spray water flow rate of 2.0 kg / cm²; finally, through the rewarming cooling section at a temperature of 20°C for 10 seconds with a spray water flow rate of 2.5 kg / cm².

[0111] The circuit board after spraying is then dried by suction; the dried circuit board is then blow-dried to obtain a circuit board with a high-density protective film.

[0112] Example 4

[0113] The difference from Example 2 is that the modified OSP solution comprises 0.2 parts N-(1H-benzo[D]imidazol-2-yl)-2-methylbenzamide, 0.4 parts N-(3,4-dichlorophenyl)-1H-benzo[D]imidazol-2-carboxamide, 0.4 parts N-(1H-benzo[D]imidazol-2-yl)-4-fluorobenzamide, 0.5 parts copper sulfate, 0.3 parts nickel sulfate, 6 parts heptanoic acid, 6 parts formic acid, 4 parts octanoic acid, 0.5 parts EDTA, 0.5 parts EDTMPA, 0.5 parts ATMP, and 85 parts water; the other conditions are the same.

[0114] Comparative Example 1

[0115] The difference from Example 2 is that the modified OSP solution includes 1.0 parts polybenzimidazole, 0.5 parts copper sulfate and 0.3 parts nickel sulfate, 12 parts formic acid and 4 parts octanoic acid, 1.5 parts EDTA and 85 parts water, while the other conditions are the same.

[0116] Comparative Example 2

[0117] The difference from Example 2 lies in the different processing steps of the cooling circulation spray equipment. Specifically, the circuit board undergoes surface cleaning; the circuit board after surface cleaning undergoes surface micro-etching; and the circuit board is immersed in a modified OSP solution, wherein the modified OSP solution comprises 0.2 parts of N-(1H-benzo[D]imidazol-2-yl)-2-methylbenzamide and 0.8 parts of N-(3,4-dichlorophenyl)-1H-benzo[D]imidazol-2-carboxamide, 0.5 parts of copper sulfate and 0.3 parts of nickel sulfate, 12 parts of formic acid and 4 parts of octanoic acid, 1.5 parts of EDTA and 85 parts of water.

[0118] The soaked circuit board is conveyed to the spraying area of ​​the cooling circulation spraying equipment via a conveying assembly; the conveying speed of the conveying assembly is controlled at 3 meters / minute, and the circuit board is sprayed with room temperature water through multiple nozzles in the spraying area for 21 seconds, with a water flow rate of 1.2 kg / cm2.

[0119] The circuit board after spraying is then dried by suction; the dried circuit board is then blow-dried to obtain a circuit board with a high-density protective film.

[0120] The color changes of the dense protective film after multiple high-temperature reflow soldering tests of Examples 1-4 and Comparative Examples 1-2 were statistically analyzed. The conditions for multiple high-temperature reflow soldering tests were: lead-free soldering temperature of 260℃-270℃ and reflow time of 55S-60S.

[0121] Meanwhile, the thickness of the high-density protective film covering the circuit board was tested, and the data is shown in the table below:

[0122]

[0123]

[0124] As can be seen from the table, the high-density protective film of Examples 1-4 only turned yellow after at least four high-temperature reflow soldering cycles, while the high-density protective film of Comparative Examples 1-2 turned yellow after only two high-temperature reflow soldering cycles. Therefore, the heat resistance of the high-density protective film of Examples 1-4 is better than that of Comparative Examples 1-2, especially the high-density protective film of Example 4, which has even better heat resistance, only showing slight discoloration after six cycles. This is mainly because the modified OSP solution uses a compound of alkylamide benzimidazole, transition metal salt, organic acid solvent, chelating agent and water, which makes the synergistic effect of each component of the modified OSP solution better. At the same time, combined with the segmented spraying treatment of the cooling circulating spraying equipment, a thinner circuit board with better heat resistance can be obtained.

[0125] As can be seen from the comparison between Example 2 and Comparative Example 1, since the polybenzimidazole component used in Comparative Example 1 is different from the alkylamide benzimidazole composition in Example 2, the thickness of the high-density protective film in Example 2 is significantly thinner than that in Comparative Example 1, and the number of high-temperature reflows is more than that in Comparative Example 1. The high-density protective film of the circuit board in Example 2 is thin and has good heat resistance.

[0126] As can be seen from the comparison between Example 2 and Comparative Example 2, since Comparative Example 2 did not use cooling water for segmented spraying, the room temperature water spraying not only damaged the density of the protective film but also caused the thickness of the protective film to decrease, thereby reducing the number of high-temperature reflow soldering cycles of the circuit board of Comparative Example 2. That is, the circuit board of Comparative Example 2 turned yellow after using two high-temperature reflow soldering cycles.

[0127] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for surface treatment of a high-density protective film on a circuit board, characterized in that, Includes the following steps: Obtain the circuit board; The circuit board is immersed in a modified OSP solution, wherein the modified OSP solution comprises 0.8 to 1.5 parts of an alkylamide benzimidazole composition, 0.5 to 1 part of a transition metal salt, 12 to 20 parts of an organic acid solvent, 1 to 2 parts of a chelating agent, and 80 to 90 parts of water. The circuit board after soaking is sprayed using a cooling circulation spraying device; wherein, the soaked circuit board is sent to the spraying area of ​​the cooling circulation spraying device; the circuit board is sprayed in sections through multiple nozzles in the spraying area; The segmented spraying system is divided into a buffer cooling section, a rapid cooling section, and a regenerative cooling section. The temperature of the buffer cooling section is 15℃~20℃, the time is 5S~10S, and the flow rate of the sprayed water is 1.0kg / cm. 2 ~1.5kg / cm 2 ; The temperature of the rapid cooling section is 8℃~12℃, the time is 3S~8S, and the flow rate of the sprayed water is 1.5kg / cm. 2 ~2.0kg / cm 2 ; The temperature of the reheat cooling section is 15℃~20℃, the time is 5S~10S, and the flow rate of the sprayed water is 2.0kg / cm. 2 ~2.5kg / cm 2 ; The circuit board after spray treatment is dried to obtain the circuit board.

2. The surface treatment method for a high-density protective film on a circuit board according to claim 1, characterized in that, The conveying speed of the cooling circulating spray equipment is 2 meters / minute to 4 meters / minute.

3. The surface treatment method for a high-density protective film on a circuit board according to claim 1, characterized in that, The step of drying the circuit board after the spray treatment includes the following specific steps: The circuit board after spraying is then dried by suction. The circuit board, after being absorbed, is then dried by blowing.

4. The surface treatment method for a high-density protective film on a circuit board according to claim 1, characterized in that, Before the step of immersing the circuit board in the modified OSP solution and after the step of obtaining the circuit board, the surface treatment method for the high-density protective film on the circuit board further includes the following steps: The circuit board is then subjected to surface cleaning treatment; The circuit board after surface cleaning is subjected to surface micro-etching.

5. The surface treatment method for a high-density protective film on a circuit board according to claim 1, characterized in that, The alkylamide benzimidazole composition includes at least one of N-(3,4-dichlorophenyl)-1H-benzo[D]imidazol-2-carboxamide, N(1H-benzo[D]imidazol-2-yl)-2-methylbenzamide, N-(1H-benzo[D]imidazol-2-yl)-2,4-difluorobenzamide, and N-(1H-benzo[D]imidazol-2-yl)-4-fluorobenzamide.

6. The surface treatment method for a high-density protective film on a circuit board according to claim 1, characterized in that, The transition metal salt includes at least one sulfate of copper, iron, nickel, cobalt, or manganese metals.

7. The surface treatment method for a high-density protective film on a circuit board according to claim 1, characterized in that, The organic acid solvent includes at least one of formic acid, acetic acid, propionic acid, octanoic acid, heptanoic acid, acrylic acid, and aminosulfonic acid.

8. A circuit board, characterized in that, It is prepared by the surface treatment method of the high-density protective film for circuit boards according to any one of claims 1 to 7.

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