Circuit board black-edge-free bonding pad area stack-up structure and manufacturing method thereof

Abstract

The invention discloses a circuit board black-edge-free bonding pad area stacking structure which comprises a base body layer, a first conducting layer and a second conducting layer are arranged on the two sides of the base body layer respectively, a first partition layer and a first separation layer are arranged on one side of the first conducting layer, and a second partition layer and a second separation layer are arranged on one side of the second conducting layer. The invention discloses a manufacturing method of a circuit board non-black-edge bonding pad area stack structure. The manufacturing method comprises the following specific steps of S1, ink blending and silk-screen printing; s2, pre-drying is carried out; s3, performing an exposure process; s4, developing process; s5, process optimization and effect improvement; the ink disclosed by the invention not only can cover the surface of the whole circuit board, but also can accurately control the size and the shape of a curing area through subsequent exposure and development processes, so that the minimization of a black area around a bonding pad area is realized; the pre-baking, exposure and development processes are combined, so that the accurate control on the peripheral area of the bonding pad area can be realized; and the method has higher flexibility and accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of printed circuit board manufacturing, and more specifically, to a printed circuit board black-edge-free pad area stack structure; it also relates to a manufacturing method of a printed circuit board black-edge-free pad area stack structure. Background Art

[0002] In the field of electronics manufacturing, the manufacturing of printed circuit boards is one of the key processes. Especially in the manufacturing process of complex microelectronic components, the manufacturing of the pad area is crucial for the performance and reliability of the printed circuit board. Although traditional pad area manufacturing methods (such as using tapes or films) can protect the un-soldered areas, they often leave a relatively large un-soldered area, resulting in a large black area and making it difficult to meet the requirement of minimizing the area around the pad. In addition, traditional methods have high requirements for manufacturing precision, which easily leads to uneven sizes of the black areas, affecting the appearance quality and performance of the printed circuit board.

[0003] With the continuous progress of the packaging technology of electronic components, the requirements for the appearance and performance of printed circuit boards are also constantly increasing. In the manufacturing process, how to minimize the black area around the pad area has become an important technical difficulty. During the manufacturing process, traditional black inks are prone to cause a decline in the quality of printed circuit boards due to excessive curing range or uneven coverage.

[0004] Manufacturing a black-edge-free pad area stack structure for a printed circuit board is a high-precision manufacturing process, involving multiple key steps, including ink formulation, pre-baking, exposure, and development, etc. Traditional pad manufacturing methods have multiple problems, such as the ink is easy to penetrate into the holes, the development is not clean, there are many defects, etc., resulting in low manufacturing yield, high cost, and low efficiency. In addition, traditional methods have high requirements for materials and processes, and it is difficult to adapt to the rapid development of new processes and new materials.

[0005] However, traditional pad manufacturing methods have the following defects:

[0006] The ink is easy to penetrate into the holes, resulting in the inability to achieve a black-edge-free stack structure;

[0007] The development is not clean, and it is difficult to remove the residual ink, affecting the manufacturing quality;

[0008] There are many defects, including unclean development, ink clogging of holes, etc., reducing the yield;

[0009] There are high requirements for process conditions, and it is difficult to adapt to the rapid development of new processes and new materials.

[0010] In view of these problems, the present invention proposes an improved manufacturing process for a printed circuit board black-edge-free pad area stack structure. By optimizing the ink formulation, pre-baking, exposure, and development processes, the manufacturing efficiency, yield, and stability are significantly improved, the generation of waste is reduced, and it has the advantages of environmental protection and energy conservation. Summary of the Invention

[0011] One object of the present invention is to provide a new technical solution for a structure of a solder pad area without black edges on a circuit board and a manufacturing method thereof.

[0012] According to a first aspect of the present invention, there is provided a structure of a solder pad area without black edges on a circuit board, including a substrate layer, a first conductive layer and a second conductive layer are respectively provided on both sides of the substrate layer, a first spacer layer and a first separation layer are provided on one side of the first conductive layer, and a second spacer layer and a second separation layer are provided on one side of the second conductive layer.

[0013] Further, the substrate layer, the first conductive layer, the second conductive layer, the first spacer layer, the first separation layer, the second spacer layer and the second separation layer form a circuit board.

[0014] Further, through vias, embedded vias, first settling vias and second settling vias are embedded inside the circuit board, and the through vias, the embedded vias, the first settling vias and the second settling vias are connected by transmission lines and bead connection lines.

[0015] Further, the substrate layer is made of a copper oxide board or other high-temperature resistant material board, the first conductive layer and the second conductive layer are made of a copper foil or a copper-plated material board, the first spacer layer and the second spacer layer are made of a high-temperature glue or other bonding materials, and the first separation layer and the second separation layer are made of a solder mask ink or other isolation materials.

[0016] Further, a plurality of solder pad areas are provided on one side of the first conductive layer and the second conductive layer, a brushing area is provided outside the solder pad areas, and the solder pad areas penetrate through the first spacer layer, the first separation layer, the second spacer layer and the second separation layer and are located at the end face of the circuit board.

[0017] A manufacturing method of a structure of a solder pad area without black edges on a circuit board is as follows:

[0018] S1. Ink preparation and screen printing: In the manufacturing of the solder pad area of the circuit board, a structure without black edges is manufactured. The solder mask ink is mixed with thinner in a certain proportion to obtain the ink, a film is pasted on the solder pad area, and then the ink is applied to the circuit board.

[0019] S2. Pre-baking: The ink is pre-baked to make the ink semi-cured and volatilize the solvent, improving the subsequent exposure accuracy.

[0020] S3. Exposure process: The ultraviolet light is used to make the ink undergo a photopolymerization reaction to cure the area that needs to be protected, and the ink in the unexposed area is soluble in the developer.

[0021] S4, Development Process: Use a gas-liquid two-phase nozzle and air hole spray gun combination system for development, and then remove the uncured ink to ensure that there is no residual ink on the circuit board;

[0022] S5, Process Optimization and Effect: By adjusting the nozzle layout and development time, using air pressure water resistance instead of solid rollers, reducing ink back contamination, and optimizing the overflow rate of composite water washing, reducing the pressure of wastewater treatment.

[0023] Further, the specific steps of ink formulation and screen printing in S1 are as follows:

[0024] Mix the solder mask ink and thinner in proportion, and use a magnetic stirrer or ultrasonic stirrer for uniform mixing;

[0025] Use an infrared sensor to measure the ink viscosity and ensure that the viscosity is in the range of 130 - 150 Pa·s;

[0026] Then, stick a film on the pad area, and then apply the ink on the circuit board through ink screen printing;

[0027] Control the ink screen printing thickness to be 15 - 25 μm, and use a thickness controller for precise measurement and adjustment;

[0028] Select a squeegee with a Shore hardness of 75 degrees, and set the pressure to 0.4 - 0.6 MPa to ensure uniform ink coverage and no penetration into the holes;

[0029] Apply a PET release film to the area that needs to be protected, and ensure that the light transmittance is ≥95% to ensure the exposure accuracy.

[0030] Further, the specific steps of pre-baking in S2 are as follows:

[0031] Set the pre-baking temperature to 70 - 75 °C, and use a constant temperature device to keep the temperature stable;

[0032] Control the pre-baking time within 38 - 40 minutes to ensure that the ink is semi-cured and the solvent is volatilized;

[0033] After the pre-baking is completed, check whether the ink surface is dry and there is no solvent residue, and use an infrared detector to confirm the ink state.

[0034] Further, the specific steps of the exposure process in S3 are as follows:

[0035] Use a 7 kW high-pressure tungsten lamp as the light source, and control the wavelength within the range of 350 - 450 nm;

[0036] Set the exposure energy to 8 - 9 levels to ensure appropriate light intensity;

[0037] Adopt a vacuum negative pressure system with a pressure of 85 - 90 kPa to ensure the tight fit of the film and the board surface, and reduce the pattern deviation caused by light scattering;

[0038] Manufacture a light-blocking area on the circuit board to block ultraviolet rays from penetrating the substrate and prevent the ink on the other side from being accidentally cured.

[0039] During the exposure process, use a CCD camera or a holographic detector to monitor the light coverage range and intensity in real time to ensure uniform exposure.

[0040] Furthermore, the specific steps of the developing process in S3 are as follows:

[0041] Prepare the developer as a 1.0 - 1.2% Na2CO3 solution and mix it thoroughly using a magnetic stirrer.

[0042] Set the developing temperature to 30 - 35°C and maintain the temperature stability using a constant temperature water bath.

[0043] Use a gas-liquid two-phase nozzle and a pore spray gun combination system for developing: set the upper spray pressure to 1.8 - 2.0 kg / cm 2 , the nozzle height is 13 cm; set the lower spray pressure to 2.0 - 2.5 kg / cm 2 , and use a pore spray gun to ensure that the ink in through holes and blind holes is completely removed.

[0044] The developing equipment adopts a stepped overflow design: first perform high-pressure spraying, then medium-pressure water washing, and finally pure water composite washing.

[0045] Then, ensure that the board surface is free of water stains through cold air drying and hot air drying to avoid subsequent oxidation.

[0046] Use an ultraviolet lamp to check for defects such as unclean development, ink clogging of holes, and residue in blind holes to ensure that the board surface quality meets the standards.

[0047] The beneficial effects of the present invention are as follows:

[0048] By using ink to manufacture the pad area, the present invention can complete the coverage of ink on the entire circuit board. Subsequently, through precise exposure and developing processes, only the areas that need to be cured are processed, thereby minimizing the black area around the pad area; this method can significantly reduce the size of the black area and achieve the manufacturing effect of "only a little black area and ink around it".

[0049] Through the process method of the present invention, problems caused by excessive curing range or uneven coverage during the traditional black ink manufacturing process can be avoided, ensuring that the black area of the pad area is precise and consistent. This high-precision manufacturing process can significantly improve the appearance quality and reliability of the circuit board.

[0050] Through the above beneficial effects, the present invention uses ink to manufacture the pad area. The ink can not only cover the entire circuit board surface, but also accurately control the size and shape of the solidified area through subsequent exposure and development processes, thereby minimizing the black area around the pad area; by mixing the solder resist ink with the oil-opening water in proportion to prepare the ink, and combining the pre-baking, exposure and development processes, it is possible to achieve precise control of the area around the pad area; it has higher flexibility and accuracy; through the ink and precise manufacturing process, it is possible to leave a very small black area around the pad area, which has significant technical advantages.

[0051] Further features and advantages of the present invention will become apparent from the following detailed description of exemplary embodiments of the present invention with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

[0053] Figure 1 A schematic diagram of a circuit board without a black-border pad region stacking structure in one embodiment;

[0054] Figure 2 A circuit board without a black edge pad area stacking structure in an embodiment Figure 1 The enlarged schematic diagram at A in the middle;

[0055] Figure 3 A schematic cross-sectional view of a stacked structure of a circuit board without a black-border pad area in an embodiment;

[0056] Figure 4 A schematic diagram of ink preparation and silk-screen printing of a manufacturing method of a circuit board without a black-edge pad area stacking structure in another embodiment;

[0057] Figure 5 A schematic diagram of an exposure process of a method for manufacturing a circuit board without a black-border pad region stacked structure in another embodiment;

[0058] Figure 6 A schematic diagram of a development process of a method for manufacturing a circuit board without a black-border pad region stacked structure in another embodiment;

[0059] Figure 7 The figure is a schematic flow chart of the steps of a method for manufacturing a circuit board black-border-free pad area stacking structure in another embodiment.

[0060] In the figure: 1, matrix layer; 2, first conductive layer; 3, second conductive layer; 4, first isolation layer; 5, second isolation layer; 6, first separation layer; 7, second separation layer; 8, pad area; 9, oil-brushing area; 10, embedded through-hole; 11, first settling through-hole; 12, second settling through-hole; 13, full through-hole; 14, electric bead connection line; 15, transmission line. Detailed implementation manners

[0061] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that: unless otherwise specifically stated, the relative arrangements of components and steps, numerical expressions and values set forth in these embodiments do not limit the scope of the present invention.

[0062] The following description of at least one exemplary embodiment is merely illustrative in nature and in no way serves as a limitation to the present invention and its application or use.

[0063] Technologies, methods and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the said technologies, methods and devices should be regarded as part of the specification.

[0064] In all the examples shown and discussed here, any specific values should be construed as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values.

[0065] As Figure 1-3 shown, a laminated structure of a circuit board with a pad area without black edges includes a matrix layer 1, a first conductive layer 2 and a second conductive layer 3 are respectively provided on both sides of the matrix layer 1, a first isolation layer 4 and a first separation layer 6 are provided on one side of the first conductive layer 2, and a second isolation layer 5 and a second separation layer 7 are provided on one side of the second conductive layer 3.

[0066] In this embodiment, preferably, the matrix layer 1, the first conductive layer 2, the second conductive layer 3, the first isolation layer 4, the first separation layer 6, the second isolation layer 5 and the second separation layer 7 form a circuit board;

[0067] It should be noted that the first conductive layer 2 and the second conductive layer 3 are symmetrically distributed on both sides of the matrix layer 1. Through the buffering effects of the first isolation layer 4 and the second isolation layer 5, the internal stress during the hot pressing process is effectively offset; in the pressing experiment of a 6-layer HDI board, the warpage of the traditional structure is 0.25 mm, and that of the present application is reduced to 0.09 mm.

[0068] Reliability verification data

[0069]

[0070] In this embodiment, preferably, through-holes 13, embedded vias 10, first sunken vias 11, and second sunken vias 12 are embedded inside the circuit board, and the through-holes 13, the embedded vias 10, the first sunken vias 11, and the second sunken vias 12 are connected by transmission lines 15 and bead connection lines 14;

[0071] It should be noted that: The through-holes 13 penetrate the entire circuit board to provide global electrical connection, and the impedance consistency is optimized to ±3%; the embedded vias 10 are for local interlayer interconnection, reducing the via stub effect, and the high-speed signal loss is reduced by 30%; the stepped depth design of the first sunken vias 11 and the second sunken vias 12 realizes selective connection between different layers, and the wiring density is increased by 40%; the combination of the transmission lines 15 and the bead connection lines 14 provides mechanical stress buffering and realizes power supply connection, and passes 3000 times of thermal cycle tests (-40°C to 125°C) without failure; the transmission lines 15 adopt differential pair serpentine traces, and the delay deviation < 5ps / inch.

[0072] Comparison data:

[0073] Parameter Traditional via design This embodiment Improvement amplitude Signal integrity (eye diagram height) 0.6UI 0.85UI +41.6％ Via impedance deviation ±8％ ±3％ +62.5％ 。

[0074] In this embodiment, preferably, the base layer 1 is made of copper oxide board or other high-temperature resistant material boards, the first conductive layer 2 and the second conductive layer 3 are made of copper foil or copper-plated material boards, the first isolation layer 4 and the second isolation layer 5 are made of high-temperature glue or other bonding materials, and the first separation layer 6 and the second separation layer 7 are made of solder mask ink or other isolation materials;

[0075] It should be noted that the first isolation layer 4 and the second isolation layer 5 are made of high-temperature glue or other bonding materials, with a shear strength > 15MPa, Tg > 180°C, and the thickness uniformity after lamination is ±2μm; the first separation layer 6 and the second separation layer 7 are made of solder mask ink or other isolation materials, with a dielectric strength > 1000V / mil, a leakage current < 1pA, and the CAF resistance performance is improved by 5 times; the hardness of the solder mask ink after curing > 6H, and it can withstand chemical solvent wiping > 50 times.

[0076] In this embodiment, preferably, a number of pad areas 8 are provided on one side of the first conductive layer 2 and the second conductive layer 3, a painted area 9 is provided outside the pad areas 8, and the pad areas 8 penetrate through the first isolation layer 4 and the first separation layer 6, as well as the second isolation layer 5 and the second separation layer 7 and are located at the end face of the circuit board;

[0077] It should be noted that the pad area 8 is accurately exposed by laser drilling with a position accuracy of ±10μm, avoiding the undercut problem of traditional etching processes; the soldermask area 9 adopts a gradient solder mask thickness design to solve the "pillow effect" during soldering; the copper layer thickness of the pad area 8 is ≥30μm, enabling it to withstand multiple reworkings (it can actually withstand more than 5 reflow solders); the solder mask contact angle of the soldermask area 9 is >80°, preventing bridging defects caused by solder climbing.

[0078] Measured performance:

[0079]

[0080]

[0081] Comprehensive advantage comparison

[0082]

[0083] Reference Figure 4-7 : A manufacturing method for a non-black-edge pad area stack structure of a circuit board, the specific steps are as follows:

[0084] S1. Ink formulation and screen printing: For the non-black-edge stack structure manufacturing in the pad area of the circuit board, mix the solder mask ink and thinner in proportion to obtain the ink, stick a film on the pad area, and then apply the ink on the circuit board.

[0085] S2. Pre-baking: Perform pre-baking on the ink to semi-cure the ink and volatilize the solvent, improving the subsequent exposure accuracy.

[0086] S3. Exposure process: Use ultraviolet light to cause the ink to undergo a photopolymerization reaction, curing the areas that need to be protected. The ink in the unexposed areas is soluble in the developer.

[0087] S4. Development process: Use a gas-liquid two-phase nozzle and air hole spray gun combination system for development, and then remove the uncured ink to ensure that there is no residual ink on the circuit board.

[0088] S5. Process optimization and effect: By adjusting the nozzle layout and development time, using air pressure water resistance instead of a solid roller, reducing ink back contamination, and optimizing the composite water washing overflow rate, reducing the waste water treatment pressure.

[0089] In this embodiment, preferably, the specific steps of the ink formulation and screen printing in S1 are as follows:

[0090] Mix the solder mask ink and thinner in proportion, and use a magnetic stirrer or ultrasonic stirrer for uniform mixing.

[0091] Use an infrared sensor to measure the ink viscosity and ensure that the viscosity is within the range of 130 - 150 Pa·s.

[0092] Then, stick a film on the pad area, and then apply the ink on the circuit board through screen printing;

[0093] Control the screen printing thickness of the ink to be 15 - 25μm, and use a thickness controller to accurately measure and adjust;

[0094] Select a squeegee with a Shore hardness of 75 degrees, and set the pressure to 0.4 - 0.6MPa to ensure that the ink is evenly covered and does not seep into the holes;

[0095] Apply a PET release film to the area that needs to be protected, ensuring that the light transmittance is ≥95% to ensure the exposure accuracy;

[0096] It should be noted that by adjusting the ink viscosity and controlling the screen printing thickness, ensure that the ink is evenly covered and there are no penetration holes. The application of the PET protective film avoids the formation of depressions due to the extrusion of the ink, improving the manufacturing accuracy;

[0097] The ratio of ink to thinner is usually controlled at 5:1 to 7:1 (i.e., the ink amount is about 60% - 70% of the total mixture); the specific ratio needs to be optimized according to the type of ink, viscosity requirements, and process conditions;

[0098] If the ratio of ink to thinner is 6:1, then the ink accounts for 60% and the thinner accounts for 40% in the mixture; if the ratio is 7:1, then the ink accounts for 70% and the thinner accounts for 30%;

[0099] Viscosity requirements of the ink: Too high viscosity (>150Pa·s) will result in poor ink fluidity and difficulty in uniform coverage; too low viscosity (<130Pa·s) will cause the ink to easily flow away or seep into the holes;

[0100] Volatility and curing performance of the ink: The solvent evaporation rate of the ink is directly related to the ratio. Too high a ratio (too much ink) will lead to too fast evaporation rate, affecting the curing effect; too low a ratio (too little ink) will result in too much solvent, affecting the coverage performance of the ink.

[0101] Process conditions:

[0102] Temperature and time: The ratio needs to be adjusted according to the pre - baking temperature (70 - 75°C) and time (38 - 40 minutes) to ensure that the ink reaches a semi - cured state and volatilizes the solvent during pre - baking.

[0103] Exposure accuracy: The ratio needs to ensure that the ink is evenly covered and does not seep into the holes during exposure, avoiding the cured area beyond the design range.

[0104] In this embodiment, preferably, the specific steps of pre - baking in S2 are as follows:

[0105] Set the pre - baking temperature to 70 - 75°C, and use a constant - temperature device to keep the temperature stable;

[0106] The pre-baking time is controlled within 38 - 40 minutes to ensure that the ink is semi-cured and the solvent is volatilized;

[0107] After the pre-baking is completed, check whether the surface of the ink is dry and there is no solvent residue, and use an infrared detector to confirm the state of the ink;

[0108] It should be noted that through the pre-baking treatment, the solvent in the ink is volatilized, reducing subsequent exposure errors and improving manufacturing stability;

[0109] Selection and control of pre-baking temperature

[0110] Temperature setting range:

[0111] Too low temperature: It is not sufficient to effectively volatilize the solvent, affecting the subsequent exposure effect;

[0112] Too high temperature: It may cause the ink to cure too quickly or volatilize too much, affecting manufacturing precision;

[0113] Optimal temperature: 70 - 75 °C is the best range for the ink to volatilize and cure, which can not only effectively volatilize the solvent but also prevent the ink from over-curing;

[0114] Application of constant temperature equipment: Use a constant temperature equipment (such as an electric thermostatic oven) to maintain the stability of the pre-baking temperature and ensure that the ink is preheated and partially cured at a uniform temperature.

[0115] Control of pre-baking time:

[0116] Too short time: The solvent in the ink may not be completely volatilized, resulting in poor exposure effect;

[0117] Too long time: The ink may be over-cured, affecting the subsequent developing process;

[0118] Optimal time: 38 - 40 minutes is the best time for the ink to be preheated and cured, which can fully volatilize the solvent and partially cure the ink without affecting the subsequent processes.

[0119] Detection of the dry state of the ink:

[0120] Detection method: Use an infrared detector (such as an infrared meter) to check whether the surface of the ink is dry and there is no solvent residue.

[0121] Infrared detection principle: Infrared rays can penetrate the surface of the ink to detect its dry state. The transmittance of infrared rays through dry ink is relatively high, while the reflectance of infrared rays by ink containing solvent is relatively high.

[0122] Detection result: If the detection result shows that the surface of the ink is dry and there is no solvent residue, the pre-baking treatment is completed and the next process step can be entered; otherwise, the pre-baking time needs to be extended or the temperature parameters need to be adjusted.

[0123] In this embodiment, preferably, the specific steps of the exposure process in S3 are as follows:

[0124] Use a 7kW high-pressure tungsten lamp as the light source, and control the wavelength within the range of 350 - 450nm;

[0125] Set the exposure energy to levels 8 - 9 to ensure moderate light intensity;

[0126] Adopt a vacuum negative pressure system with a pressure of 85 - 90kPa to ensure the tight fit between the film and the board surface, reducing graphic deviation caused by light scattering;

[0127] Make a light-blocking area on the circuit board to block ultraviolet rays from penetrating the substrate and prevent the ink on the other side from being accidentally cured;

[0128] During the exposure process, use a CCD camera or a holographic detector to monitor the light coverage range and intensity in real time to ensure uniform exposure;

[0129] It should be noted that the exposure process is a key step in the manufacturing process of the non-black-edge pad area stack structure of the circuit board. Through the selection of the high-pressure tungsten lamp, the application of the vacuum negative pressure system, the design of the light-blocking area, and real-time monitoring technology, precise control and curing of the area around the pad area are achieved; not only improving the manufacturing accuracy and yield, but also reducing the generation of waste products and energy consumption, which has important technical and economic value;

[0130] Selection and application of the high-pressure tungsten lamp: Use a 7kW high-pressure tungsten lamp as the ultraviolet (UV) light source, and control the wavelength within the range of 350 - 450nm.

[0131] Wavelength control: The selection of the ultraviolet wavelength is crucial. If the wavelength is too short (e.g., <350nm), it may cause excessive light scattering. If the wavelength is too long (e.g., >450nm), it may not be able to effectively cure the ink;

[0132] Light source intensity: The high-pressure tungsten lamp provides high-intensity ultraviolet rays, which can complete the exposure in a short time while avoiding uneven exposure caused by a too weak light source.

[0133] Application effect:

[0134] Shorten the exposure time: The high-power light source can complete the photopolymerization reaction of the ink in a shorter time, improving the process efficiency.

[0135] Reduce light scattering: The light intensity of the high-pressure tungsten lamp is moderate, which can reduce the scattering of light on the chip surface and ensure the exposure accuracy.

[0136] Control of exposure energy: The exposure energy is precisely controlled at levels 8 - 9 (specific unit: mJ / cm 2 ), ensuring moderate light intensity.

[0137] Too low energy: Insufficient exposure energy may cause incomplete curing of the ink, affecting the manufacturing quality.

[0138] Too high energy: Excessive exposure energy may cause accidental curing of the ink in the uncured area, leading to quality problems.

[0139] Optimal energy: Exposure energy at levels 8 - 9 can achieve precise curing of the ink, avoiding unnecessary losses.

[0140] Energy control method: Use a light energy meter or sensor to monitor the light intensity in real - time, ensuring that the exposure energy is within the range of 8 - 9 levels; dynamically adjust the exposure energy by adjusting the light source voltage or distance to ensure stable light intensity.

[0141] Application of the vacuum negative pressure system: Use a vacuum negative pressure system with the pressure controlled within the range of 85 - 90 kPa.

[0142] Too low pressure: Insufficient vacuum negative pressure may cause the film to be loose from the board surface, affecting the exposure effect.

[0143] Too high pressure: Excessive vacuum negative pressure may cause damage to the board surface or increased light scattering.

[0144] Optimal pressure: A negative pressure system of 85 - 90 kPa can ensure the tight fit between the film and the board surface, reduce light scattering, and optimize the exposure effect.

[0145] System composition:

[0146] Vacuum pump: Use a mechanical vacuum pump or other vacuum equipment to ensure negative pressure stability.

[0147] Sealing system: Through a sealing design, prevent external gas from entering and ensure a negative pressure environment inside the system.

[0148] Light - blocking area design and implementation: Design a light - blocking area (such as an etched copper layer or a photoresist coating) in the core board or PP layer to block ultraviolet rays from penetrating the substrate and prevent accidental curing of the ink on the other side.

[0149] Width of the light - blocking area: The width of the light - blocking area should be 0.05 - 0.1 mm larger than the unilateral size of the actual ghosting area to compensate for the alignment error and ensure exposure accuracy.

[0150] Fabrication of the light - blocking area:

[0151] Etched copper layer: Use an etching technique on the core board to fabricate the light - blocking area, forming a photoresist layer in the area to be protected through chemical or physical methods.

[0152] Photoresist coating: Coat the area to be protected on the core board with a photoresist material and achieve the light - blocking effect through photolithography or other methods.

[0153] Real-time monitoring and adjustment during the exposure process: Use a CCD camera or a holographic detector to monitor the light coverage and intensity in real time to ensure uniform exposure.

[0154] CCD camera: Through the image sensing of the CCD camera, monitor the light coverage and intensity in real time, and when uneven exposure or deviation is found, adjust it in a timely manner.

[0155] Holographic detector: Through holographic imaging technology, accurately measure the light coverage and intensity to ensure the exposure effect.

[0156] Monitoring and adjustment:

[0157] Real-time monitoring: Through the monitoring device, find uneven exposure or deviation, and adjust the light source position, light angle or exposure energy in a timely manner to ensure exposure accuracy.

[0158] Data recording: Record the monitoring data to provide a reference for subsequent process optimization.

[0159] In this embodiment, preferably, the specific steps of the developing process in S4 are as follows:

[0160] Prepare the developer as a 1.0 - 1.2% Na2CO3 solution and mix it well using a magnetic stirrer;

[0161] Set the developing temperature to 30 - 35°C and maintain the temperature stability using a constant temperature water bath;

[0162] Use a gas-liquid two-phase nozzle and a pore gun combination system for development: The upper spray pressure is set to 1.8 - 2.0 kg / cm 2 , the nozzle height is 13 cm; the lower spray pressure is set to 2.0 - 2.5 kg / cm 2 , and use a pore gun to ensure that the ink in through holes and blind holes is completely removed;

[0163] The developing equipment adopts a stepped overflow design: First, perform high-pressure spraying, then medium-pressure water washing, and finally pure water composite water washing;

[0164] Then, ensure that the board surface is free of water stains through cold air drying and hot air drying to avoid subsequent oxidation;

[0165] Use an ultraviolet lamp to check for defects such as unclean development, ink clogging of holes, and residue in blind holes to ensure that the board surface quality meets the standards;

[0166] It should be noted that the developing process is a key step in printed circuit board manufacturing. Through a gas-liquid two-phase nozzle and air hole spray gun combination system, stepped overflow design, and multi-stage drying and detection, it achieves the complete removal of uncured ink and the improvement of board surface quality; not only improves manufacturing efficiency and yield, but also reduces waste generation and energy consumption, with important technical and economic value;

[0167] Preparation and mixing of developer

[0168] Preparation of developer: Prepare a 1.0 - 1.2% sodium carbonate (Na2CO3) solution as the developer, and use a magnetic stirrer to mix thoroughly to ensure the uniformity of the developer.

[0169] Developer concentration: A 1.0 - 1.2% sodium carbonate solution can effectively remove uncured ink without causing corrosion or other side effects to the board surface.

[0170] Mixing method: Use a magnetic stirrer for rough mixing to ensure the uniform distribution and stability of the developer.

[0171] Mixing effect: After magnetic stirring, the developer becomes uniform and stable, capable of evenly covering the surface of the printed circuit board; the sodium carbonate solution can remove uncured ink, ensuring a clean board surface without residue.

[0172] Control of developing temperature

[0173] Temperature setting range: Control the developing temperature between 30 - 35°C;

[0174] Too low temperature: Insufficient developing temperature may cause the developer to volatilize too quickly or the ink not to dissolve completely;

[0175] Too high temperature: Too high developing temperature may cause heat damage to the board surface or excessive volatilization of the developer;

[0176] Optimal temperature: A developing temperature of 30 - 35°C can achieve effective volatilization of the developer and complete dissolution of the ink, ensuring a clean effect.

[0177] Temperature control effect: The developing temperature is moderate, capable of effectively dissolving uncured ink and ensuring a thorough cleaning of the board surface; the application of a constant temperature device ensures the stability of the developing temperature, avoiding the influence of temperature fluctuations on the developing effect.

[0178] Application of gas-liquid two-phase nozzle and air hole spray gun combination system

[0179] Combination of nozzle and spray gun: Use a gas-liquid two-phase nozzle and air hole spray gun combination system for developing to achieve the complete removal of ink in vias and blind vias;

[0180] Gas-liquid two-phase nozzle: The nozzle adopts a gas-liquid two-phase design, which can spray the developing solution and, at the same time, use gas assistance to remove the ink residue in the holes.

[0181] Air-hole spray gun: The spray gun is designed with an air-hole structure, which can use air flow assistance to remove the ink in the holes and avoid the problem of hole blockage.

[0182] Setting of nozzle height and pressure:

[0183] Upper spray pressure: Set to 1.8 - 2.0 kg / cm 2 , and the nozzle height is 13 cm;

[0184] Lower spray pressure: Set to 2.0 - 2.5 kg / cm 2 , and use the air-hole spray gun;

[0185] Pressure control: The upper spray and lower spray pressures are set in layers to ensure that the developing solution can evenly cover the through holes and blind holes, while avoiding ink back-adhesion or hole blockage.

[0186] Synergistic effect of nozzle and spray gun:

[0187] Upper spray: Spray the developing solution through the gas-liquid two-phase nozzle to cover the surface of the circuit board.

[0188] Lower spray: Use air flow through the air-hole spray gun to remove the ink residue in the holes and ensure no residue in the through holes and blind holes.

[0189] Application effect:

[0190] Cleaning of through holes and blind holes: The combination of the gas-liquid two-phase nozzle and the air-hole spray gun can completely remove the ink in the through holes and blind holes and avoid the problem of hole blockage.

[0191] Reduction of ink back-adhesion: Through layered spray pressure control, the back-adhesion of the developing solution is reduced, and the influence of ink residue on the manufacturing quality is avoided.

[0192] Step overflow design of the developing equipment

[0193] Realization of the overflow design: The developing equipment adopts a step overflow design, including three stages: high-pressure spraying, medium-pressure water washing, and pure water composite water washing.

[0194] High-pressure spraying: First, perform high-pressure spraying (3.0 - 5.0 kg / cm 2 ), to ensure that the developing solution fully enters the holes and covers the through holes and blind holes.

[0195] Medium-pressure water washing: Then, perform medium-pressure water washing (3.0 - 5.0 kg / cm 2 ), to remove the ink residue in the holes.

[0196] Pure water composite water washing: Finally, perform pure water composite water washing (5.0 kg / cm2 Above), ensure that the board surface is thoroughly clean and residue-free.

[0197] Function of stepped overflow:

[0198] Efficiency improvement: By segmental processing, the development speed can be significantly increased while reducing the waste of developing solution.

[0199] Environmental protection and energy conservation: The stepped overflow design reduces the consumption of developing solution and the pressure of wastewater treatment, showing advantages in environmental protection and energy conservation.

[0200] Drying and board surface cleaning

[0201] Cold air drying: Use a cold air blower (10 - 15 m / min) to dry the board surface, ensuring that the board surface is free of water stains and avoiding subsequent oxidation or contamination.

[0202] Air speed control: The cold air speed is moderate, which can dry quickly without causing the board surface to heat up.

[0203] Hot air drying: For high-density areas or areas that need to be dried quickly, use hot air drying (55 - 75 °C, 5 - 10 minutes) to ensure that the board surface is thoroughly dry.

[0204] Effect of board surface cleaning:

[0205] No water stains: Cold air and hot air drying can ensure that the board surface is free of water stains, avoiding contamination or oxidation in subsequent processes.

[0206] Drying stability: Hot air drying can dry quickly, ensuring that the board surface is dry and free of residual developing solution.

[0207] Inspection and quality control

[0208] Ultraviolet lamp inspection: Use an ultraviolet lamp to check for defects such as unclean development, ink blockage of holes, and residual in blind holes, ensuring that the board surface quality meets the standards.

[0209] Inspection method: Observe the board surface through an ultraviolet lamp, find areas that have not been developed or residual ink, and adjust the development process parameters in a timely manner.

[0210] Quality control standards:

[0211] Unclean development: There are no obvious areas on the board surface that have not been developed, the surface is evenly dry and free of ink residue.

[0212] Ink blockage of holes: There is no ink residue in through holes and blind holes, and the cleaning effect of nozzles and spray guns is good.

[0213] Residual in blind holes: There is no residual ink in blind holes, avoiding affecting subsequent manufacturing due to residual ink.

[0214] In this embodiment, preferably, the specific steps of process optimization and effects in S5 are as follows:

[0215] Adjust the nozzle layout, increase the developing speed to 2.0 m / min, and at the same time reduce the consumption of pure water;

[0216] Use air pressure water blocking to replace the solid roller to reduce ink back contamination;

[0217] Optimize the overflow rate of composite water washing (3 - 6 L / min) to reduce the pressure of wastewater treatment;

[0218] Regularly clean the nozzles and punching water knives to avoid impurity accumulation and ensure stable developing quality;

[0219] Through process optimization, improve the developing efficiency and yield, reduce resource waste, and enhance manufacturing stability;

[0220] It should be noted that process optimization and effects are key links in the manufacturing process of the non - black - edge pad area stack structure of printed circuit boards. Through nozzle layout optimization, air pressure water blocking replacement, composite water washing overflow rate optimization, and regular cleaning measures, the improvement of developing efficiency and yield is achieved, while reducing resource waste and wastewater treatment pressure. It not only improves manufacturing efficiency and quality but also has important technical and economic value;

[0221] Adjustment of nozzle layout and increase of developing speed

[0222] Nozzle layout optimization: By adjusting the nozzle layout, the developing speed is increased to 2.0 m / min.

[0223] Optimization method: According to the size and structure of the printed circuit board, reasonably arrange the nozzle positions to ensure uniform coverage of the developing solution.

[0224] Effect: Through layout optimization, the developing speed is significantly increased, and at the same time, the waste of developing solution is reduced.

[0225] Increase of developing speed: The increase of developing speed is directly related to nozzle layout optimization and improvement of developing solution fluidity. The optimized nozzle layout can more efficiently cover the surface of the printed circuit board, reducing developing time and resource consumption.

[0226] Application of air pressure water blocking replacing solid roller

[0227] Replace the solid roller: Use air pressure water blocking to replace the solid roller to reduce ink back contamination;

[0228] Replacement principle: Air pressure water blocking uses air flow resistance to replace the friction of the solid roller, avoiding ink back contamination due to roller friction.

[0229] Application effect: This replacement method can significantly reduce the problem of ink back contamination and improve manufacturing quality.

[0230] Optimization measures:

[0231] Wind pressure control: The pressure of the wind pressure water blocking system is set to 2.0 - 2.5 kg / cm 2 , ensuring that the airflow fully blocks the contact between the roller and the circuit board and preventing ink from adhering back.

[0232] Airflow design: The airflow design of the nozzle and air hole spray gun combination system can effectively support the application of wind pressure water blocking, ensuring the stability and efficiency of the system.

[0233] Optimization of the overflow rate of composite water washing

[0234] Overflow rate optimization: Optimize the overflow rate of composite water washing (3 - 6 L / min) to reduce the pressure of wastewater treatment.

[0235] Optimization method: By adjusting the overflow valve of the water washing device, optimize the overflow rate of composite water washing to ensure the efficient operation of the wastewater treatment system.

[0236] Effect: The optimized composite water washing system can significantly reduce the pressure of wastewater treatment, lower the cost of wastewater treatment, and at the same time reduce the waste of water resources.

[0237] Measures for regular cleaning of nozzles and punching water knives

[0238] Cleaning measures: Regularly clean the nozzles and punching water knives to avoid the accumulation of impurities and ensure the stable quality of development.

[0239] Cleaning frequency: According to the manufacturing cycle, it is recommended to regularly clean the nozzles and punching water knives every 30 - 60 minutes to remove the accumulated ink or impurities.

[0240] Cleaning method: Use a soft brush or a special cleaning agent to clean the nozzles and punching water knives to ensure the cleaning effect.

[0241] Application effect: Through regular cleaning, avoid the accumulation of impurities and filter plugging problems, ensure the long-term stable operation of the developing equipment, and improve the manufacturing quality and efficiency.

[0242] Comprehensive effect of process optimization

[0243] Improvement of developing efficiency: Through the optimization of nozzle layout, wind pressure water blocking and composite water washing, the developing efficiency is increased to 2.0 m / min, significantly shortening the developing time.

[0244] Time shortening: The optimized developing process can complete development in a shorter time, improving production efficiency.

[0245] Yield improvement: Through optimization measures, defects such as unclean development, ink clogging of holes and residual blind holes are reduced, significantly improving the manufacturing yield.

[0246] Defect reduction: The optimized development process can more accurately remove uncured ink, reducing the occurrence of defects.

[0247] Resource waste reduction: By optimizing the overflow rate of composite water washing and the nozzle layout, the development process reduces the waste of developing solution and pure water, lowering resource consumption.

[0248] Improved manufacturing stability: Through regular cleaning and system optimization, the development process is more stable, reducing quality problems caused by equipment failures or impurity accumulation.

[0249] Although some specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and not for limiting the scope of the present invention. Those skilled in the art should understand that the above embodiments can be modified without departing from the scope and spirit of the present invention. The scope of the present invention is defined by the appended claims.

Claims

1. A circuit board black-edge-free pad area stack structure, characterized in that: It includes a substrate layer (1), with a first conductive layer (2) and a second conductive layer (3) respectively provided on both sides of the substrate layer (1). On one side of the first conductive layer (2), there is a first isolation layer (4) and a first separation layer (6), and on one side of the second conductive layer (3), there is a second isolation layer (5) and a second separation layer (7).

2. A circuit board black-edge-free pad area stack structure according to claim 1, characterized in that: The substrate layer (1), the first conductive layer (2), the second conductive layer (3), the first isolation layer (4), the first separation layer (6), the second isolation layer (5) and the second separation layer (7) form a circuit board.

3. A circuit board black-edge-free pad area stack structure according to claim 2, characterized in that: Full vias (13), embedded vias (10), first settling vias (11) and second settling vias (12) are embedded inside the circuit board, and the full vias (13), the embedded vias (10), the first settling vias (11) and the second settling vias (12) are connected by transmission lines (15) and bead connection lines (14).

4. A circuit board black-edge-free pad area stack structure according to claim 3, characterized in that: The substrate layer (1) is made of a copper oxide board or other high-temperature resistant material board. The first conductive layer (2) and the second conductive layer (3) are made of copper foil or copper-plated material boards. The first isolation layer (4) and the second isolation layer (5) are made of high-temperature glue or other bonding materials. The first separation layer (6) and the second separation layer (7) are made of solder mask ink or other isolation materials.

5. A circuit board black-edge-free pad area stack structure according to claim 2, characterized in that: On one side of the first conductive layer (2) and the second conductive layer (3), there are several pad areas (8). On the outside of the pad areas (8), there is an oil-brushing area (9). The pad areas (8) penetrate through the first isolation layer (4), the first separation layer (6), the second isolation layer (5) and the second separation layer (7) and are located at the end face of the circuit board.

6. A manufacturing method for a non-black-edge pad area stack structure of a circuit board, characterized in that: The manufacturing process is used to prepare the structure described in any one of claims 1-5; the specific steps are as follows: S1. Ink preparation and screen printing: In the pad area of the circuit board, a non-black-edge laminated structure is manufactured. The solder mask ink and thinner are mixed in proportion to obtain the ink. A film is pasted on the pad area, and then the ink is applied to the circuit board. S2. Pre-baking: The ink is pre-baked to make the ink semi-cured and volatilize the solvent, improving the subsequent exposure accuracy. S3. Exposure process: The ink is subjected to a photopolymerization reaction using ultraviolet light to cure the area that needs to be protected. The ink in the unexposed area is soluble in the developer. S4. Development process: A gas-liquid two-phase nozzle and air hole spray gun combination system is used for development, and then the uncured ink is removed to ensure that there is no residual ink on the circuit board. S5. Process optimization and effect: By adjusting the nozzle layout and development time, using air pressure water resistance instead of solid rollers, reducing ink back contamination, and optimizing the composite water washing overflow rate, reducing the waste water treatment pressure.

7. The manufacturing method of a circuit board's black-edge-free pad area stack structure according to claim 6, characterized in that: The specific steps of ink preparation and screen printing in S1 are as follows: The solder mask ink and thinner are mixed in proportion, and a magnetic stirrer or ultrasonic stirrer is used for uniform mixing. An infrared sensor is used to measure the viscosity of the ink to ensure that the viscosity is within the range of 130-150 Pa·s. Then, a film is pasted on the pad area, and then the ink is applied to the circuit board through ink screen printing. Control the screen printing thickness of the ink to be 15 - 25 μm, and precisely measure and adjust it using a thickness controller; Select a squeegee with a Shore hardness of 75 degrees, and set the pressure to 0.4 - 0.6 MPa to ensure uniform ink coverage and no infiltration into the holes; Apply a PET release film to the area that needs to be protected, ensuring a light transmittance of ≥95% to guarantee the exposure accuracy.

8. The manufacturing method of a circuit board's black-edge-free pad area stack structure according to claim 6, characterized in that: The specific steps of pre-baking in S2 are as follows: Set the pre-baking temperature to 70 - 75 °C, and use a constant temperature device to keep the temperature stable; Control the pre-baking time within 38 - 40 minutes to ensure that the ink is semi-cured and the solvent is volatilized; After pre-baking, check whether the surface of the ink is dry and there is no solvent residue, and use an infrared detector to confirm the state of the ink.

9. The manufacturing method of a circuit board's black-edge-free pad area stack structure according to claim 6, characterized in that: The specific steps of the exposure process in S3 are as follows: Use a 7kW high-pressure tungsten lamp as the light source, and control the wavelength within the range of 350 - 450 nm; Set the exposure energy to level 8 - 9 to ensure moderate light intensity; Adopt a vacuum negative pressure system with a pressure of 85 - 90 kPa to ensure the tight fit of the film and the board surface, and reduce the graphic deviation caused by light scattering; Make a light-blocking area on the circuit board to block the ultraviolet rays from penetrating the substrate and prevent the ink on the other side from being accidentally cured; During the exposure process, use a CCD camera or a holographic detector to monitor the light coverage range and intensity in real time to ensure uniform exposure.

10. A manufacturing method of a circuit board without a black-edge pad area stack structure according to claim 6, characterized in that: The specific steps of the developing process in S3 are as follows: Prepare the developer as a 1.0 - 1.2% Na2CO3 solution, and fully mix it using a magnetic stirrer; Set the developing temperature to 30 - 35 °C, and use a constant temperature water bath to maintain the temperature stable; Developing using a gas-liquid two-phase nozzle and a vent hole spray gun combination system: The upper spray pressure is set to 1.8 - 2.0 kg / cm 2 , the nozzle height is 13 cm; the lower spray pressure is set to 2.0 - 2.5 kg / cm 2 , use a vent hole spray gun to ensure that the ink in the through holes and blind holes is completely removed; The developing equipment adopts a stepped overflow design: first, perform high-pressure spraying, then medium-pressure water washing, and finally pure water composite water washing; Then ensure that the board surface is free of water stains through cold air drying and hot air drying to avoid subsequent oxidation; Use an ultraviolet lamp to check for defects such as unclean development, ink clogging of holes, and residual blind holes to ensure that the board surface quality meets the standards.

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