Detachable cofferdam and encapsulating method

Abstract

The invention discloses a detachable cofferdam and an encapsulating method, and aims to solve the technical problem that the space utilization rate of a base plate is reduced due to the fact that a cofferdam structure cannot be detached after the cofferdam is encapsulated in the prior art. A removable cofferdam includes a cofferdam frame and a dissolvable adhesive, allowing easy removal after completion of the encapsulation process, reducing damage to the substrate and encapsulation material. The encapsulating method comprises the following steps: coating a release agent on the surface of the cofferdam frame, bonding the cofferdam by using a dissolvable adhesive, disassembling the cofferdam frame after encapsulating, and cleaning the adhesive. The invention provides a simple and effective method for removing the cofferdam frame after encapsulation, and the surface of the treated substrate has no bonding residue and no redundant space occupation.

Description

Technical Field

[0001] The invention relates to the field of electronic manufacturing technology, and in particular to a detachable cofferdam and an encapsulation method. Background Art

[0002] In the microelectronics industry, it is a critical step to implement local protection packaging of components on local areas of the substrate with organic materials. This packaging not only protects the components from physical damage and environmental factors such as humidity, temperature changes, dust and chemicals, but also ensures the long-term stability and reliability of the components, thereby extending the service life of the product. In addition, packaging also helps to improve the electrical insulation performance of components, prevent circuit short circuits and electrical interference, and ensure the normal operation of the circuit.

[0003] In the manufacture of microelectronic products, there are two main methods for local protection packaging (COB operation): Glob-Topencapsulate and Dam-and-Fillencapsulate. Glob-Topencapsulate is a method that drips the packaging material directly onto the installed chip or other components, allowing the material to flow naturally to cover the entire chip surface. It is suitable for protecting the entire chip or component surface, especially when rapid and large-area coverage is required. Dam-and-Fillencapsulate builds a dam structure around the components to be encapsulated, and then injects the packaging material into the dam. This can control the overflow range of the material and is suitable for situations where the position of the packaging material needs to be precisely controlled.

[0004] In the dam encapsulation method, the dam is usually constructed by dispensing and marking with a special dam glue. In the implementation of this method, the dam glue adheres to both the substrate and the encapsulation glue, making it difficult to remove the dam structure. Therefore, the dam structure is generally left on the product substrate, occupying the substrate area, thereby reducing the effective layout area of ​​the substrate. This practice not only limits the space utilization of the substrate, but also affects the miniaturization and integration of electronic products, resulting in a waste of resources. At the same time, this also increases the overall volume and weight of the product, which is not conducive to achieving a lightweight design of the product.

[0005] Therefore, a new solution is needed to replace the traditional method of building dams and glue dots and lines. This new method should be able to easily remove the dam structure after completing the protective packaging of the components, freeing up the occupied substrate space to improve the space utilization of the substrate and the integration of the product. Summary of the invention

[0006] The object of the present invention is to provide a detachable cofferdam and encapsulation method to overcome the disadvantage of the prior art that the cofferdam structure cannot be removed after cofferdam encapsulation, resulting in a decrease in substrate space utilization.

[0007] In order to achieve the above object, the present invention adopts the following technical solution: A detachable cofferdam, comprising: A cofferdam frame is used to bond to the pre-packaged area on the substrate to be processed to perform cofferdam encapsulation; Release agent to enable the cofferdam frame to be disassembled after the cofferdam is enclosed.

[0008] The cofferdam frame is prepared according to the geometry of the pre-encapsulated area on the substrate to be processed.

[0009] The material of the cofferdam frame is selected to be close to the substrate and encapsulation material.

[0010] A method of encapsulation using a removable cofferdam, the method comprising: S1, coating a release agent on the surface of the cofferdam frame and drying it to obtain a cofferdam frame with the release agent on the surface; S2, bonding a cofferdam frame having a release agent on the surface to a pre-packaged area on the substrate to be processed using an adhesive to form a cofferdam encapsulation area; S3, performing dispensing encapsulation and curing in the cofferdam encapsulation area, removing the cofferdam frame with a release agent on the surface, and obtaining the substrate to be cleaned; S4, using a corresponding solvent to clean the remaining adhesive on the substrate to be cleaned to obtain an encapsulated substrate.

[0011] The release agent applied in step S1 is a soluble release agent, which can be dissolved by a corresponding solvent in a subsequent step.

[0012] In step S2, adhesive is applied on the substrate to be processed by using a continuous dot-dash glue line method.

[0013] The soluble adhesive used to bond the cofferdam frame in step S2 can maintain a certain strength after curing to ensure the stability of the cofferdam frame during the glue dispensing and encapsulation process.

[0014] The process of removing the cofferdam frame in step S3 is to make the soluble adhesive lose its viscosity by heating or using a chemical solvent, thereby realizing the disassembly of the cofferdam frame.

[0015] The solvent used to clean the remaining adhesive in step S4 is harmless to the substrate and the encapsulation material and can be completely volatilized.

[0016] This encapsulation method is applicable to pre-encapsulated areas of various geometric shapes and sizes, and the shape and size of the cofferdam frame can be customized according to specific encapsulation requirements.

[0017] Compared with the prior art, the present invention has the following beneficial technical effects: A detachable cofferdam is used for cofferdam encapsulation in a pre-packaged area on a substrate to be processed. The cofferdam of the present invention is prepared in a targeted manner according to the geometric shape of the pre-packaged area on the substrate to be processed, and accurately matches the layout requirements of various components. For pre-packaged areas with regular geometric shapes, such as rectangles and circles, it can fit tightly; for irregular shapes, it can also fit accurately, play a blocking role, firmly restrain the encapsulation material, reduce the risk of overflow, significantly improve the packaging accuracy and stability, and ensure the consistency of product packaging. The coating of the release agent allows the cofferdam frame to be easily disassembled after the cofferdam encapsulation operation, avoiding the cofferdam frame remaining on the substrate to continue to occupy the substrate space and add unnecessary weight to the substrate, effectively solving the technical problem that the traditional cofferdam cannot be removed after being fixed, does not occupy the substrate area, and improves the utilization rate of substrate resources.

[0018] A packaging method provides an efficient, clean and customizable packaging solution by using a removable cofferdam. The method obtains a cofferdam frame with a release agent on the surface by coating a soluble release agent on the surface of the cofferdam frame and drying it, laying the foundation for subsequent demoulding. In the method, the continuous dot-dash glue line is used to lay the adhesive, which can accurately control the amount of adhesive on the one hand, and evenly distribute the adhesive on the other hand, so that the cofferdam frame and the substrate are seamlessly connected, the cofferdam encapsulation area is firmly built, and the encapsulation material leakage is prevented. The soluble adhesive used has appropriate strength after curing, maintains the stability of the cofferdam frame, and ensures a smooth packaging process. After completing the dot-dash encapsulation and curing, the remaining adhesive is cleaned with a solvent that is harmless to the substrate and encapsulation material and has good volatility, so as to cause the adhesive to lose its viscosity, thereby leaving no adhesive residue on the surface of the substrate. The entire operation process is convenient and efficient, and the damage to the substrate and encapsulation material is low, which provides convenience for subsequent inspection, assembly and other processes. This encapsulation method has excellent versatility and can flexibly customize the cofferdam frame according to specific packaging requirements. It can be applied to various pre-packaging areas of various substrates, reducing process adaptation costs and improving production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of a detachable cofferdam in an embodiment of the present invention.

[0020] Figure 2 The figure is a schematic flow chart of an encapsulation method in an embodiment of the present invention. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0023] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "provided with", "set / connected", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0024] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "several" is two or more, unless otherwise clearly and specifically defined.

[0025] Embodiment 1: The specific embodiment of the present invention provides a practical application scenario of a detachable cofferdam and an encapsulation method. First, the detachable cofferdam is processed according to the geometric shape of the substrate to be processed and the packaging area. In this embodiment, the substrate to be processed is S1000-2M, and FR4 material is used to prepare the cofferdam frame, wherein the structure of the detachable cofferdam is as follows: Figure 1 As shown, including: A cofferdam frame is used to bond to the pre-packaged area on the substrate to be processed to perform cofferdam encapsulation; The release agent is evenly sprayed on the surface of the cofferdam frame through a nozzle, so that the cofferdam frame can be disassembled after the cofferdam is encapsulated.

[0026] During the processing, a CNC milling machine is used to accurately cut and shape the FR4 sheet. The operator programs the processing according to the design size to ensure that the size accuracy of the processed cofferdam frame is within the range. After the processing is completed, in order to make the surface of the cofferdam frame reach the ideal smoothness, it needs to be finely ground and polished. During the grinding process, sandpaper of different grits is used for gradual grinding, starting with coarse sandpaper to remove larger processing marks, and then gradually replaced with fine sandpaper to reduce the surface roughness. Finally, polishing is performed to make the surface roughness reach Ra0.4μm. Such a smooth and flat surface is conducive to the subsequent bonding and demolding operations with the substrate, and can effectively reduce the bonding gap and resistance during demolding.

[0027] Then, the substrate is encapsulated using a cofferdam frame. The encapsulation process is as follows: Figure 2 A packaging method is shown, comprising: S1, coating a release agent on the surface of the cofferdam frame and drying it to obtain a cofferdam frame with the release agent on the surface; S2, bonding a cofferdam frame having a release agent on the surface to a pre-packaged area on the substrate to be processed using an adhesive to form a cofferdam encapsulation area; S3, performing dispensing encapsulation and curing in the cofferdam encapsulation area, removing the cofferdam frame with a release agent on the surface, and obtaining the substrate to be cleaned; S4, using a corresponding solvent to clean the remaining adhesive on the substrate to be cleaned to obtain an encapsulated substrate.

[0028] In step S1, when applying the release agent to the cofferdam frame, long-chain alkyl silicone oil is used as the release agent, and anhydrous ethanol is used as the release agent solvent, which is evenly mixed in a volume ratio of 1:5 to prepare a release agent solution. When applying the release agent, a spray gun is used for operation, and the nozzle of the spray gun should be kept perpendicular to the surface of the cofferdam frame at a distance of about 15-20cm to ensure that the release agent solution can be evenly sprayed on the surface of the cofferdam frame. The operator needs to control the spraying speed and spraying amount so that the coating thickness is between 30-50μm. After the coating is completed, the cofferdam frame is placed in a constant temperature oven for drying. The temperature of the oven should be pre-set to 70°C, and the drying time is 45 minutes. During the drying process, the solvent in the release agent solution will gradually evaporate, causing the release agent to solidify on the surface of the cofferdam frame, forming a uniform release agent layer, thereby obtaining a cofferdam frame with a release agent on the surface.

[0029] The soluble adhesive used in step S2 is selected as positive photoresist. The prepared positive photoresist is loaded into a dispensing syringe and installed on a dispensing machine for dispensing. When operating the dispensing machine, the operator needs to continuously dot and draw glue lines along the edge of the pre-packaged area on the substrate to be processed to ensure the integrity and uniformity of the glue line and achieve seamless bonding between the cofferdam frame and the substrate. After the cofferdam frame coated with adhesive is accurately placed on the pre-packaged area, press gently and fix it with a positioning fixture to ensure that the relative position of the cofferdam frame and the substrate is accurate, so that the cofferdam frame fits tightly with the substrate. Then the substrate is placed in a UV curing box for preliminary curing to form a cofferdam encapsulation area, providing a stable cofferdam structure for subsequent encapsulation operations.

[0030] In step S3, an encapsulation material of model FP4450 is used for dispensing and encapsulation operations. In the cofferdam encapsulation area, an automatic dispensing machine is used to perform dispensing and encapsulation operations. Before dispensing, it is necessary to calculate the amount of dispensing based on the area of ​​the pre-packaged area and the layout of the components to ensure that the amount of encapsulation material per square centimeter is controlled at about 0.18 ml. After the dispensing is completed, the substrate is placed in a constant temperature curing oven for curing. The temperature of the constant temperature curing oven should be precisely controlled at 100°C, and the curing time is 1.5 hours. During the curing process, the FP4450 encapsulation material will undergo a chemical reaction, gradually solidify and form, forming effective protection for the components.

[0031] After the curing is completed, the cofferdam frame is removed because the surface of the cofferdam frame is coated with a release agent and can be disassembled. The disassembled substrate still has adhesive left over from the encapsulation process, so the substrate is cleaned with an adhesive solvent, and acetone is selected as the adhesive solvent. The substrate is placed in a container filled with acetone and soaked for 12 minutes. During the soaking process, acetone will gradually penetrate into the positive photoresist, causing its molecular structure to change, thereby dissolving the adhesive. After the soaking is completed, use a soft brush to gently scrub the surface of the substrate to remove the residual adhesive and release agent by scrubbing. Finally, rinse with deionized water and blow dry with compressed nitrogen. After these steps, the encapsulated substrate is obtained, and the substrate area originally occupied by the cofferdam frame and adhesive is exposed, and subsequent component welding, wiring and other operations can be performed according to design requirements.

[0032] Embodiment 2: This specific embodiment provides another practical application scenario of a detachable cofferdam and encapsulation method.

[0033] In this specific embodiment, the pre-packaged area on the substrate to be processed is circular with a diameter of 35mm. According to this size, FR4 material is selected to make a circular cofferdam frame. CNC machining technology is adopted. The trajectory and size parameters of the circle need to be accurately calculated during programming to ensure that the diameter tolerance of the circular cofferdam frame is controlled within ±0.05mm and the height is 4mm. After processing, the surface of the cofferdam frame is chemically polished. The formula of the chemical polishing solution is selected according to the characteristics of the FR4 material, and contains an oxidant, a chelating agent and a buffer. Polishing removes tiny surface defects and makes the surface roughness less than Ra0.2μm, thereby improving the demolding effect, reducing the friction during demolding, and reducing the impact on the substrate and encapsulation materials.

[0034] The release agent long-chain alkyl silicone oil and the release agent solvent anhydrous ethanol are mixed in a volume ratio of 1:4, and the release agent solution is obtained after stirring evenly. The cofferdam frame is immersed in the release agent solution by dipping method, and the dipping time is 30 seconds. During the dipping process, it is necessary to ensure that the cofferdam frame is completely immersed in the solution and the solution can fully infiltrate the surface of the cofferdam frame. After the dipping is completed, the cofferdam frame is slowly removed to allow the excess solution to drip naturally to avoid the formation of liquid accumulation or uneven thickness on the surface. The cofferdam frame coated with the release agent is placed in a well-ventilated environment and dried naturally for 10 minutes to partially evaporate the solvent and reduce the gas pressure generated by the evaporation of the solvent in the oven. Then put it in a constant temperature oven and dry it at 65°C for 1 hour to ensure that the release agent is firmly attached to the surface of the cofferdam frame to obtain a cofferdam frame with a release agent on the surface.

[0035] Choose positive photoresist as a soluble adhesive. Before use, check its viscosity and curing performance. Positive photoresist should be stored in a dark, low-temperature (generally 5-10°C) environment to prevent its performance from changing. Use it within the shelf life, and before use, take it out of the storage environment and leave it at room temperature for a period of time (about 1-2 hours) to balance its temperature and avoid viscosity changes due to temperature differences that affect the dispensing effect.

[0036] Plasma surface treatment is performed on the substrate to be processed. The plasma treatment equipment should have precise gas flow control and power regulation functions. The oxygen flow rate is set to 40sccm, the power is 250W, and the treatment time is 3 minutes. During the plasma treatment process, oxygen plasma reacts physically and chemically with the surface of the substrate to remove organic matter, oxides and other impurities on the surface, while increasing the active groups on the surface and improving the surface energy, thereby enhancing the activity and wettability of the substrate surface and improving the bonding effect. After treatment, the substrate should be immediately transferred to a clean operating environment to avoid re-contamination of the surface. During the transfer process, a special substrate handling tool should be used to prevent the substrate surface from being scratched or collided.

[0037] Load the soluble adhesive positive photoresist into the dispensing valve with a precision needle and connect it to the dispensing equipment for dispensing operation. The parameters of the dispensing valve are set as follows: dispensing pressure 0.3MPa, dispensing time 40ms, dispensing interval 0.8mm, and a glue line with a width of about 1-1.2mm is formed. When operating the dispensing equipment, the operator should have rich experience and precise operating skills to ensure the continuity and uniformity of the glue line. When continuously dotting and marking the glue line along the circumference of the pre-packaged area on the substrate to be processed, pay attention to the connection between the starting point and the end point to avoid breakpoints or uneven overlap of the glue line. Carefully place the cofferdam frame with a release agent on the surface on the pre-packaged area coated with the adhesive, and accurately align it through the optical positioning system. The optical positioning system should have high-precision image recognition and positioning functions, and be able to accurately coincide the center of the cofferdam frame with the center of the pre-packaged area, with an error control within ±0.05mm. Then let it stand at room temperature for 1.5 hours to allow the adhesive to fully cure and form a cofferdam encapsulation area. During the static process, the ambient temperature should be kept stable to avoid temperature fluctuations affecting the curing of the adhesive.

[0038] Use a manual glue dispenser to dispense glue and encapsulate in the cofferdam encapsulation area. According to the area of ​​the circular area and the required encapsulation thickness, calculate the amount of glue at each point, about 0.16 ml per square centimeter. After the dispensing is completed, put the substrate into a constant temperature curing box for curing. The temperature control accuracy of the constant temperature curing box should reach ±1°C, and cure at 95°C for 1.2 hours. During the curing process, the encapsulation material will undergo a cross-linking reaction and gradually form a solid encapsulation layer. The control of curing time and temperature has a great influence on the performance of the encapsulation material. Too high temperature or too long time may cause the encapsulation material to age and become brittle. Too low temperature or too short time may make the encapsulation incomplete, affecting the protection effect.

[0039] After curing, place the substrate in the adhesive solvent acetone solution and soak for 10 minutes. The concentration of the acetone solution should be kept above 95% to ensure a good dissolution effect. During the soaking process, the solution can be stirred appropriately to accelerate the dissolution of the adhesive, but the stirring speed should not be too fast to avoid damage to the substrate and the cured encapsulation material. After the soaking is completed, use an ultrasonic cleaning device at a frequency of 50kHz for 3 minutes to assist in cleaning. Ultrasonic cleaning can produce a strong cavitation effect, making it easier for residual adhesive and release agent to detach from the surface of the substrate. After cleaning, rinse with deionized water and blow dry with high-purity nitrogen to obtain the encapsulated substrate, which can be used for subsequent assembly, testing and other processes. During the entire disassembly and cleaning process, pay close attention to the status of the substrate and encapsulation material to ensure that there is no damage or performance degradation due to improper operation.

[0040] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only preferred examples of the present invention and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A detachable cofferdam, characterized in that: include: A cofferdam frame is used to bond to the pre-packaged area on the substrate to be processed to perform cofferdam encapsulation; Release agent to enable the cofferdam frame to be disassembled after the cofferdam is enclosed.

2. A detachable cofferdam according to claim 1, characterized in that: The cofferdam frame is prepared according to the geometric shape of the pre-packaged area on the substrate to be processed.

3. A detachable cofferdam according to claim 1, characterized in that: The cofferdam frame is made of a material similar to that of the substrate and the encapsulation material.

4. An encapsulation method, characterized in that: The encapsulation method uses a removable cofferdam, and the encapsulation method includes: S1, coating a release agent on the surface of the cofferdam frame and drying it to obtain a cofferdam frame with the release agent on the surface; S2, bonding a cofferdam frame having a release agent on the surface to a pre-packaged area on the substrate to be processed using an adhesive to form a cofferdam encapsulation area; S3, performing dispensing encapsulation and curing in the cofferdam encapsulation area, removing the cofferdam frame with a release agent on the surface, and obtaining the substrate to be cleaned; S4, using a corresponding solvent to clean the remaining adhesive on the substrate to be cleaned to obtain an encapsulated substrate.

5. A packaging method according to claim 4, characterized in that: The release agent applied in step S1 is a soluble release agent, which can be dissolved by a corresponding solvent in subsequent steps.

6. The encapsulation method according to claim 4, characterized in that: In the step S2, the adhesive is applied on the substrate to be processed by using a continuous dot-dash glue line method.

7. The encapsulation method according to claim 4, characterized in that: The soluble adhesive used to bond the cofferdam frame in step S2 can maintain a certain strength after curing to ensure the stability of the cofferdam frame during the glue dispensing and encapsulation process.

8. The encapsulation method according to claim 4, characterized in that: The process of removing the cofferdam frame in step S3 is to make the soluble adhesive lose its viscosity by heating or using chemical solvents, thereby realizing the disassembly of the cofferdam frame.

9. The encapsulation method according to claim 4, characterized in that: The solvent used to clean the remaining adhesive in step S4 is harmless to the substrate and the encapsulation material and can be completely volatilized.

10. The encapsulation method according to claim 4, characterized in that: The encapsulation method is applicable to pre-encapsulated areas of various geometric shapes and sizes, and the shape and size of the cofferdam frame can be customized according to specific encapsulation requirements.

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