Test method of solder mask dry film

Abstract

The invention provides a method for testing a solder mask dry film, which comprises the following steps of: preparing a film layer coating and coating the film layer coating on a substrate to obtain a pretreated film body; curing the pretreated film body to form a solder mask layer, and adjusting curing data according to thermal stress change data of the solder mask layer of the pretreated film body in the curing operation until the thermal stress change data of the solder mask layer is within a preset range to obtain a solder mask dry film; and placing the solder mask dry film in a vacuum laminating machine, and laminating the release film to the surface of the solder mask layer of the solder mask dry film. Therefore, the overall production efficiency and reliability are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor packaging, and particularly relates to a method for testing a solder mask dry film. Background Art

[0002] During the chip packaging process, a solder mask dry film (SMDF) is usually covered on specific areas of the packaging substrate or around the chip to isolate solder or other metal contact materials and provide mechanical and chemical protection for subsequent bonding, soldering, and electrical interconnection processes.

[0003] However, during the chip packaging process and the long-term operation of integrated circuits, under the action of thermal stress, if abnormal phenomena such as internal cracking or bursting occur, it will lead to system working failure or complete loss of function, resulting in relatively serious batch scrap losses.

[0004] In related technologies, sampling is used to conduct destructive thermal shock tests or floating tin tests on it. On the one hand, it causes sample loss. On the other hand, if quality defects are found in the sampling, it is necessary to expand the inspection or scrap the entire batch, affecting production efficiency and revenue. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a processing method for a solder mask dry film, aiming to solve the problems of lagging detection methods for solder mask dry films, resulting in low production efficiency and poor product reliability.

[0006] To solve the above technical problems, the present invention is implemented as follows. A method for testing a solder mask dry film, the steps include: S1. Modulate a film layer coating and apply the film layer coating onto a substrate to obtain a pre-treated film body; S2. Perform a curing operation on the pre-treated film body to form a solder mask layer, and adjust the curing data according to the thermal stress change data of the solder mask layer of the pre-treated film body during the curing operation until the thermal stress change data of the solder mask layer is within a preset range to obtain a solder mask dry film; S3. Place the solder mask dry film in a vacuum laminator and laminate a release film onto the surface of the solder mask layer of the solder mask dry film.

[0007] In some embodiments of the present invention, in the step S1, the film layer coating includes a resin raw material, ceramic particles, and a toughening agent. Calculated by mass percentage, the resin raw material accounts for 50 - 70%, the ceramic particles account for 20 - 30%, and the toughening agent accounts for 10 - 20%.

[0008] In some embodiments of the present invention, the resin raw material includes at least one of epoxy resin, acrylic resin, and polyamide resin, the ceramic particles include at least one of silica particles, alumina particles, and silicon nitride particles, and the toughening agent includes at least one of polyurethane, polyvinyl alcohol ether, and styrene-butadiene rubber; The substrate includes at least one of polyimide, polytetrafluoroethylene, and polycarbonate.

[0009] In some embodiments of the present invention, the step S1 includes: S1.1. Wash the surface of the substrate with deionized water and organic solvents multiple times, and dry the substrate at 60 - 80 °C for 10 - 30 min; S1.2. Mix the resin raw material and the toughening agent in a predetermined ratio, and stir at a stirring rate of 2000 - 3000 rpm for 30 min; S1.3. Reduce the stirring rate to 500 - 1000 rpm, and gradually add ceramic particles during stirring until the addition is complete to obtain a film coating; S1.4. Coat the film coating on the substrate to obtain a pretreated film body.

[0010] In some embodiments of the present invention, in the step S1.3, after the step of gradually adding ceramic particles during stirring until the addition is complete, it further includes: Judge whether the viscosity of the system reaches a preset viscosity range, If so, obtain a film coating; If not, add an organic solvent until the viscosity of the system reaches the preset viscosity range, where the organic solvent includes at least one of acetone, toluene, ethanol, and butyl acetate.

[0011] In some embodiments of the present invention, the step S2 includes: S2.1. Uniformly raise the pretreated film body from room temperature to 80 - 100 °C at a heating rate of 10 - 12 °C / min, and maintain the temperature for 20 - 30 min to form a solder mask layer; S2.2. Raise the temperature to 100 - 125 °C, and then lower it to - 55 - 20 °C. While cycling the temperature change, obtain the thermal stress change data of the solder mask layer at a frequency of 1 - 2 Hz, and the thermal stress change data includes stress value and deformation amount; S2.3. Judge whether the thermal stress change data is within a preset range. If so, obtain a solder mask dry film; S2.4. If not, adjust the curing data, and execute the step S2.2 until the thermal stress change data is within the preset range.

[0012] In some embodiments of the present invention, the curing data includes the temperature change rate; In the step S2.4, the step of adjusting the curing data includes: If it is monitored that the change amount of the stress value within a certain range is greater than the preset change amount, the temperature change rate is reduced.

[0013] In some embodiments of the present invention, the step S3 includes: S3.1. Perform a surface coating treatment on the release film; S3.2. Place the solder mask dry film on the platform of the vacuum laminator with its solder mask layer facing up, fix the release film on the fitting head or the top feeding mechanism of the laminator, and align the position through optical alignment or fiducial points; S3.3. Evacuate to -0.06 MPa to -0.1 MPa, cover the release film on the surface of the solder mask dry film, the lamination pressure is 0.1 to 0.3 MPa, and at the same time heat to 40 to 70 °C and maintain for 5 to 20 min; S3.4. While maintaining the lamination pressure, slowly cool down to room temperature. After the temperature stabilizes, slowly release the vacuum and let the outside air enter the cavity to complete the vacuum lamination.

[0014] Compared with the prior art, the beneficial effect of a test method for a solder mask dry film in the present invention lies in: The reason why this test method for the solder mask dry film can solve the problems such as test lag and low production efficiency brought by the traditional technology is mainly due to: thermal stress monitoring and adjustment are carried out during the curing process, so that defects are exposed as early as possible and corrected in time, taking into account the S1 formula and coating quality control, providing a stable basis for S2 thermal stress analysis, ensuring the quality and consistency of the surface of the finished film layer and the release film through the S3 vacuum lamination process, and the whole process closed-loop management greatly reduces the problems of whole batch return or large-scale scrapping caused by defects found late, thereby improving the overall production efficiency and reliability. Brief Description of the Drawings

[0015] Figure 1 is a flow schematic diagram of a test method for a solder mask dry film in an embodiment of the present invention. Detailed Embodiments

[0016] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0017] Please refer to Figure 1 , the present invention provides a test method for a solder mask dry film, and the steps include: S1. Modulate the film layer coating and coat the film layer coating onto the substrate to obtain a pretreated film body.

[0018] In step S1, the film coating includes a resin raw material, ceramic particles, and a toughening agent. Calculated by mass percentage, the resin raw material accounts for 50 - 70%, the ceramic particles account for 20 - 30%, and the toughening agent accounts for 10 - 20%.

[0019] The resin raw material includes at least one of epoxy resin, acrylic resin, and polyamide resin. The ceramic particles include at least one of silica particles, alumina particles, and silicon nitride particles. The toughening agent includes at least one of polyurethane, polyvinyl alcohol ether, and styrene-butadiene rubber. The substrate includes at least one of polyimide, polytetrafluoroethylene, and polycarbonate.

[0020] Step S1 includes: S1.1. Use deionized water and organic solvents to clean the surface of the substrate multiple times, and dry the substrate at 60 - 80°C for 10 - 30 min.

[0021] Remove surface contaminants, oil stains, and dust, ensure the cleanliness of the substrate surface, and reduce local delamination or poor film adhesion caused by impurities. Using organic solvents (such as isopropyl alcohol, acetone, etc.) can further remove organic dirt that cannot be removed by water solubility, and improve the film adhesion. Drying the substrate in an environment of 60 - 80°C can effectively remove residual moisture and solvents on the surface, avoid forming bubbles or voids during subsequent coating or curing processes. Improve the activity of the substrate surface, so that subsequent coating molecules can better infiltrate and bond.

[0022] S1.2. Mix the resin raw material and the toughening agent in a predetermined ratio, and stir at a stirring rate of 2000 - 3000 rpm for 30 min.

[0023] Make the resin and the toughening agent fully contact and disperse to form a relatively uniform premixed system. Use high shear force to break large particles or aggregates, improve the mixing uniformity. Stirring for 30 min can ensure the mutual dispersion of chemical components, avoid local enrichment or local lack of toughening agent, and ensure the consistency of the overall performance of the coating. The high-speed range of 2000 - 3000 rpm can achieve a balance between dispersion efficiency and preventing excessive foaming, and avoid introducing too many bubbles or causing resin structure degradation.

[0024] S1.3. Reduce the stirring rate to 500 - 1000 rpm, and gradually add ceramic particles during stirring until the addition is completed to obtain the film coating.

[0025] Ceramic particles usually have a relatively high density. If high-speed stirring is still maintained, intense collisions, accelerated wear, or agglomeration are likely to occur. Adding particles gradually under medium-speed stirring can evenly disperse the particles, reduce the generation of bubbles, prevent agglomeration or poor dispersion caused by a large amount of particles added at one time, ensure that the viscosity and fluidity of the film layer are within a controllable range, and make it easier to control the uniformity of the overall mixture.

[0026] In step S1.3, after gradually adding ceramic particles during the stirring process until the addition is completed, it further includes: Judging whether the viscosity of the system reaches a preset viscosity range, If so, a film layer coating is obtained; If not, an organic solvent is added until the viscosity of the system reaches the preset viscosity range, where the organic solvent includes at least one of acetone, toluene, ethanol, and butyl acetate.

[0027] When the viscosity is too high, the film layer coating has insufficient fluidity during subsequent coating (such as spin coating, blade coating, or spraying), and unevenness or scratches are likely to occur; if the viscosity is too low, it is likely to cause the coating film to be too thin or sagging. Controlling the viscosity by adjusting the solvent content can make the coating more suitable for specific coating methods and process requirements.

[0028] An appropriate viscosity helps prevent excessive sedimentation or re-agglomeration of ceramic particles in the system. If the viscosity is too low, the deposition rate of the particles may increase; if the viscosity is too high, the particles are likely to aggregate locally. Maintaining the viscosity within a suitable range can evenly disperse and stably exist the particles in the matrix.

[0029] Viscosity is a key parameter affecting film thickness, adhesion, and subsequent curing quality. By precisely adjusting the viscosity at this stage, film layer defects caused by subsequent poor leveling, drying, or stress concentration can be reduced, ensuring that the prepared film layer has better mechanical properties, appearance uniformity, and heat resistance during subsequent applications.

[0030] The preset viscosity range can form a standardized control in production. Once it exceeds the range, appropriate correction can be made by adding a solvent. This can make the coatings of different batches reach the same rheological properties, thereby ensuring product consistency between batches and process repeatability.

[0031] The preset viscosity range is not from a single source, but is the comprehensive result determined through trade-offs and verification in multiple aspects such as coating process, material properties, film thickness requirements, equipment conditions, and previous experimental data. For example, if the resin raw material is epoxy resin, for spin coating and spraying to form a thin film, the viscosity is controlled within 300 - 800 cP; for knife coating to form a medium-thick film, the viscosity is controlled within 800 - 1500 cP. If the resin raw material is acrylic resin, for high-speed spin coating and spraying to form a thin film, the viscosity is controlled within 100 - 500 cP; for low-speed spin coating and knife coating to form a medium film thickness, the viscosity is controlled within 500 - 1000 cP. If the resin raw material is polyamide resin, for screen printing and knife coating to form a medium film thickness, the viscosity is controlled within 500 - 1000 cP to form a thick film, and the viscosity is controlled within 1000 - 2000 cP.

[0032] S1.4. Coat the film layer coating on the substrate to obtain a pretreated film body.

[0033] Make the uniformly prepared coating form a dense and uniform coating on the substrate surface, maximizing the functions of each component of the formulation. Different coating methods (such as spin coating, knife coating, or spraying) can meet different film thickness and uniformity requirements, and can be flexibly selected according to the application scenario. At the same time, it can also remove residual solvents, reduce the risk of bubbles or stress in the film layer, and ensure stable film formation quality during subsequent thermal curing / photo-curing.

[0034] S2. Perform a curing operation on the pretreated film body to form a solder mask layer. Adjust the curing data according to the thermal stress change data of the solder mask layer of the pretreated film body during the curing operation until the thermal stress change data of the solder mask layer is within the preset range to obtain a solder mask dry film.

[0035] Step S2 includes: S2.1. Uniformly raise the temperature of the pretreated film body from room temperature to 80 - 100 °C at a heating rate of 10 - 12 °C / min, and maintain the temperature for 20 - 30 min to form a solder mask layer.

[0036] Maintaining in the range of 80 - 100 °C allows the resin and toughening agent to react initially or volatilize solvents, avoiding the sudden accumulation of internal stress caused by a rapid increase in temperature. In this relatively mild temperature stage of this phase, the bubbles or residual solvents inside the film layer can be gradually discharged, reducing the sudden stress generated when the temperature rises to 125 °C or even higher subsequently. Maintaining the temperature for 20 - 30 min allows the leveling and molecular cross-linking on the film layer surface to be initially shaped, providing a better basic structure for the more intense thermal changes in the next step. Ensure that the resin still has a certain fluidity but is not overly cured, thus avoiding brittle cracking during subsequent thermal shock.

[0037] S2.2. Raise the temperature to 100 - 125 °C and then lower it to -55 - -20 °C. While cycling the temperature, obtain the thermal stress change data of the solder mask at a frequency of 1 - 2 Hz. The thermal stress change data includes stress values and deformation amounts.

[0038] Repeatedly cycling between 100 - 125 °C and -55 - -20 °C can truly simulate the rapid temperature rise and fall of the product in extreme environments and test the resistance of the film layer to thermal stress. This rapid cycling across high and low temperatures helps to detect or trigger potential failure modes such as microcracks and edge peeling in advance. Collecting data at a frequency of 1 - 2 Hz allows for immediate understanding of the stress and deformation generated by the film layer as the temperature changes, and for finding the stress peak and the moment of stress concentration. The deformation amount (such as the microscopic expansion and contraction of the film layer or the substrate) can further verify whether the stress is confined to a certain area or distributed throughout the film layer.

[0039] Through the stress data of multiple thermal cycles, the fatigue degree and functional attenuation of the film layer under thermal shock can be quickly evaluated. If the stress values are always within the acceptable range, it indicates that the reliability of the film layer is relatively high; otherwise, the process or formulation needs to be adjusted.

[0040] S2.3. Judge whether the thermal stress change data is within the preset range. If so, obtain the solder mask dry film. S2.4. If not, adjust the curing data and execute step S2.2 until the thermal stress change data is within the preset range.

[0041] The curing data includes the temperature change rate. In step S2.4, the steps for adjusting the curing data include: When it is monitored that the change amount of the stress value within a certain interval is greater than the preset change amount, lower the temperature change rate.

[0042] When it is monitored that the stress exceeds the standard or the deformation amount is too large, relieve the thermal shock intensity of the film layer by lowering the temperature change rate, so that the material has more time to respond to volume changes during heating or cooling and avoid the rapid accumulation of thermal stress. Enabling the thermal stress management to enter the dynamic adjustment mode allows for continuous multi-round cyclic adjustment until the film layer stress drops within the target range.

[0043] If the stress frequently exceeds the standard, it means that the film layer still needs further optimization in terms of formulation or process. By repeatedly testing and adjusting, the problem areas (such as too fast heating rate, too short heat preservation time, improper filler ratio, etc.) can be found and improved. To a certain extent, slowing down the heating / cooling rate can significantly improve the reliability and qualification rate of the film layer and reduce the risk of batch failure.

[0044] S3. Place the solder mask dry film in a vacuum laminator and laminate the release film to the surface of the solder mask layer of the solder mask dry film.

[0045] Step S3 includes: S3.1. Perform surface coating treatment on the release film.

[0046] Apply a special coating (such as silicone oil, fluoride, or other release agent systems) on the surface of the release film, which can reduce the adhesion between the release film and the solder mask dry film, facilitating the subsequent film peeling while keeping the film layer intact without tearing or adhesion residue.

[0047] The special coating can form a dense protective layer, reducing the adsorption of dust, moisture, and chemicals on the film surface, maintaining the cleanliness of the release film, and avoiding particles or bubbles during the lamination process. The surface treatment can ensure the consistency of the release film's thickness and smoothness, resulting in a more uniform pressure distribution between the release film and the solder mask layer after lamination, reducing local stress concentration.

[0048] S3.2. Place the solder mask dry film on the platform of the vacuum laminator with its solder mask layer facing up, fix the release film on the laminating head or the top feeding mechanism of the laminator, and align the positions through optical alignment or fiducial marks.

[0049] Alignment through the optical system or fiducial marks can ensure that the release film accurately covers the required area of the solder mask layer during large-area lamination, reducing material waste and the incidence of lamination defects. The solder mask dry film is positioned and fixed on the platform to keep it flat and stable, avoiding film body sliding or warping during the lamination process; the release film is positioned through the feeding mechanism, which can also reduce manual placement errors. Keeping the solder mask layer facing up and clean can prevent impurities from falling into the lamination interface; it can also effectively evacuate the air on the surface and at the interface during subsequent vacuum pumping, avoiding the generation of bubbles.

[0050] S3.3. Pump the vacuum to -0.06 MPa to -0.1 MPa, cover the release film on the surface of the solder mask dry film, with a lamination pressure of 0.1 - 0.3 MPa, and heat to 40 - 70 °C while maintaining for 5 - 20 min.

[0051] Vacuum pumping can significantly evacuate the air between the release film and the solder mask dry film, avoiding the generation of bubbles, wrinkles, or weak adhesion areas during the lamination process, thus improving the lamination uniformity and tightness. The lamination pressure can ensure full contact between the release film and the solder mask layer under vacuum conditions, reducing microvoids; heating to 40 - 70 °C helps to soften or activate certain resin components or the release film coating, thereby enhancing the interfacial wettability and lamination quality, while not overly damaging the existing structure of the solder mask layer.

[0052] Maintaining for 5 - 20 min under certain temperature and pressure allows the lamination interface to fully release stress, expel residual solvents or moisture, achieving a smooth, flat, and firmly adhered effect.

[0053] S3.4. While maintaining the lamination pressure, slowly cool down to room temperature. After the temperature stabilizes, slowly release the vacuum and let outside air enter the cavity to complete the vacuum lamination.

[0054] Slow cooling can prevent local shrinkage, deformation or delamination at the bonding interface when the temperature drops suddenly; under the maintained pressure, the stress in the material is released smoothly. During the holding period of the bonding pressure, the interface remains in a tightly bonded state, and the stress difference between and within the films is minimized, enabling the bonding state to be locked in an ideal form. After the temperature and pressure return to the normal environment, the vacuum is slowly released to avoid the instant entry of external air, which may cause film layer peeling or bubbling, and to maintain the integrity of the bonding effect. The release film is fully bonded to the solder mask layer in this state, which can provide effective protection for the solder mask layer (against scratching, contamination, etc.) during storage or subsequent processes, and can be easily peeled off while maintaining the integrity of the film layer when needed.

[0055] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for testing a solder mask dry film, characterized in that the steps include: S1, preparing a film coating and applying the film coating to a substrate to obtain a pretreated film body; S2, performing a curing operation on the pre-treated film body to form a solder mask layer, adjusting the curing data according to the thermal stress change data of the solder mask layer of the pre-treated film body during the curing operation, until the thermal stress change data of the solder mask layer is within a preset range, thereby obtaining a solder mask dry film; S3, placing the solder mask dry film in a vacuum laminating machine, and laminating a release film to the surface of the solder mask layer of the solder mask dry film.

2. A method for testing a solder mask dry film according to claim 1, characterized in that: In the step S1, the film coating comprises a resin raw material, ceramic particles and a toughening agent, and calculated by mass percentage, the resin raw material accounts for 50-70%, the ceramic particles account for 20-30%, and the toughening agent accounts for 10-20%.

3. A method for testing a solder mask dry film according to claim 2, characterized in that: The resin raw material includes at least one of epoxy resin, acrylic resin, and polyamide resin, the ceramic particles include at least one of silicon dioxide particles, aluminum oxide particles, and silicon nitride particles, and the toughening agent includes at least one of polyurethane, polyvinyl alcohol ether, and styrene-butadiene rubber; The substrate includes at least one of polyimide, polytetrafluoroethylene, and polycarbonate.

4. The method for testing a solder mask dry film according to claim 1, characterized in that: The step S1 comprises: S1.

1. Clean the substrate surface several times with deionized water and organic solvent, and dry the substrate at 60-80°C for 10-30 minutes; S1.2, mix the resin raw material and the toughening agent in a predetermined ratio, and stir at a stirring rate of 2000-3000 rpm for 30 minutes; S1.3, reducing the stirring rate to 500-1000 rpm, gradually adding ceramic particles during stirring until the addition is complete, to obtain a film coating; S1.4, coating the film layer coating on a substrate to obtain a pre-treated film body.

5. A method for testing a solder mask dry film according to claim 4, characterized in that: In the step S1.3, the step of gradually adding ceramic particles during stirring until the addition is completed further comprises: Determine whether the system viscosity reaches the preset viscosity range. If yes, a film coating is obtained; If not, an organic solvent is added until the viscosity of the system reaches a preset viscosity range, wherein the organic solvent includes at least one of acetone, toluene, ethanol, and butyl acetate.

6. A method for testing a solder mask dry film according to claim 1, characterized in that: The step S2 comprises: S2.1, the pre-treated film is uniformly raised from room temperature to 80-100 ° C, the heating rate is 10-12 ° C / min, the temperature is maintained for 20-30 min, and a solder mask is formed; S2.2, raising the temperature to 100-125°C, and then lowering it to -55--20°C, while cyclically changing the temperature, obtaining thermal stress change data of the solder mask at a frequency of 1-2 Hz, wherein the thermal stress change data includes stress value and deformation amount; S2.3, judging whether the thermal stress change data is within a preset range, and if so, obtaining a solder mask dry film; S2.4: If not, adjust the curing data and execute step S2.2 until the thermal stress change data is within a preset range.

7. A method for testing a solder mask dry film according to claim 6, characterized in that: The curing data includes a temperature change rate; In the step S2.4, the step of adjusting and solidifying data includes: If it is detected that the change of the stress value within a certain interval is greater than the preset change, the temperature change rate is reduced.

8. A method for testing a solder mask dry film according to claim 1, characterized in that: The step S3 comprises: S3.1, performing surface coating treatment on the release film; S3.

2. Place the solder mask dry film on the platform of the vacuum laminating machine with the solder mask facing upwards, fix the release film on the laminating head or the top feeding mechanism of the laminating machine, and align the position by optical alignment or marking points; S3.3, evacuate to -0.06MPa~-0.1MPa, cover the release film on the surface of the solder mask dry film, the lamination pressure is 0.1~0.3MPa, and heat to 40~70℃ at the same time, and maintain for 5~20min; S3.

4. While maintaining the bonding pressure, slowly cool down to room temperature. After the temperature stabilizes, slowly release the vacuum and allow outside air to enter the cavity to complete the vacuum bonding.

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