Lithium battery protection plate structure with double-sided device layout and double-sided plastic package and manufacturing method

Abstract

The invention relates to a lithium battery protection plate structure with double-sided device layout and double-sided plastic package and a manufacturing method thereof. The lithium battery protection plate structure comprises a rigid PCB (Printed Circuit Board) substrate, a front plastic package layer and a back plastic package layer, a battery protection chip and a precision resistor are mounted on the front surface of the rigid PCB substrate, and an MOS switch chip and a solder ball array are mounted on the back surface of the rigid PCB substrate; a front surface plastic package layer covering the front surface protects the battery protection chip and the precision resistor; the back plastic package layer covering the back wraps the MOS switch chip and exposes the solder ball array; wherein the welding height of the welding ball array is higher than the surface of the MOS switch chip. According to the lithium battery protection plate structure provided by the invention, through reasonable layout and plastic package design, the space of a circuit board is utilized to the maximum extent, the overall size of the protection plate is reduced, and the protection performance and the welding reliability are improved. The invention further provides a manufacturing method of the protection plate, double-sided processing conflicts can be avoided, the production yield is improved, the influence of thermal stress on the sensitive device is reduced, and the method is suitable for large-scale efficient production.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery protection boards, and in particular to a lithium battery protection board with a double-sided device layout and a double-sided plastic packaging structure and a manufacturing method thereof. Background Art

[0002] With the rapid development of portable electronic devices, the performance and size requirements for lithium battery protection boards are becoming increasingly stringent. Traditional lithium battery protection boards typically use a single-sided layout, which results in low board space utilization and a large overall size, making it difficult to meet the lightweight and thin requirements of modern portable devices.

[0003] Furthermore, existing protection boards lack sufficient protection. Devices like battery protection chips and precision resistors are susceptible to moisture, dust, and mechanical shock, impacting their long-term stability and performance. Furthermore, soldering reliability when connecting to flexible printed circuits (FPCs) needs to be improved. For example, poor soldering and short circuits can occur, impacting the normal operation of the entire battery system.

[0004] Furthermore, traditional manufacturing processes are prone to processing conflicts when processing double-sided devices, resulting in low production yields. Furthermore, thermal stress can significantly impact sensitive components, hindering efficient large-scale production. Therefore, a new lithium battery protection board structure and manufacturing method are needed to address these issues. Summary of the Invention

[0005] In light of this, the present invention provides a lithium battery protection board structure with a double-sided device layout and double-sided plastic sealing. Through a rational layout and plastic sealing design, this structure maximizes circuit board space utilization, reduces the overall size of the protection board, and improves protective performance and welding reliability. Furthermore, the present invention provides a manufacturing method for this protection board, which avoids double-sided processing conflicts, improves production yield, and reduces the impact of thermal stress on sensitive components, making it suitable for large-scale and efficient production.

[0006] The purpose of the present invention is achieved through the following technical solutions: A lithium battery protection board structure with a double-sided device layout and double-sided plastic sealing comprises a rigid PCB substrate, a front plastic sealing layer covering the front of the rigid PCB substrate, and a back plastic sealing layer covering the back of the rigid PCB substrate. A battery protection chip and precision resistors are mounted on the front of the rigid PCB substrate, while a MOS switch chip and solder ball array are mounted on the back. The front plastic sealing layer, covering the front, protects the battery protection chip and precision resistors; the back plastic sealing layer, covering the back, wraps the MOS switch chip and exposes the solder ball array. The solder ball array is soldered to a height higher than the surface of the MOS switch chip.

[0007] Through a double-sided design, core components are mounted on both sides of the PCB, maximizing board space and significantly reducing the overall size of the protection board, meeting the demand for lightweight and thin portable devices. The front plastic layer fully protects the battery protection chip and precision resistors from moisture, dust, and mechanical shock, ensuring long-term stability. The back plastic layer protects the MOS switch chip while exposing the solder ball array, ensuring reliable welding to the flexible printed circuit board (FPC). The overall structure is compact and highly resistant to environmental interference. The solder ball height design ensures full contact with the FPC pads, avoiding poor welding caused by insufficient height. At the same time, the height difference prevents molten solder from overflowing onto the surface of the MOS switch chip and causing short circuits. The protruding solder balls provide a buffer during assembly, reducing the risk of damage from external impact.

[0008] Preferably, the surface of the back plastic sealing layer is provided with a concave-convex texture to increase the contact area with the external heat dissipation component.

[0009] The concave-convex texture, pre-designed in the mold, increases the surface area of ​​the back-molded plastic layer, improving heat dissipation efficiency. The double-sided plastic structure inherently has a high thermal capacity. Combined with the surface texture, it quickly transfers heat generated by the MOS switch chip to the external heat sink or device housing, preventing heat accumulation that can lead to performance degradation or shortened lifespan. The textured structure also strengthens the mechanical bond between the back-molded plastic layer and heat dissipation interface materials (such as thermal grease), preventing interface separation caused by vibration or temperature fluctuations, making it suitable for high-power battery management systems.

[0010] Preferably, the back plastic sealing layer is formed by using epoxy molding compound (EMC) through a molding process.

[0011] Epoxy molding compound (EMC) offers excellent resistance to high temperatures and chemical corrosion. The molding process can evenly wrap the MOS switch chip, forming a dense protective layer to prevent chip failure due to environmental factors or mechanical stress. EMC's high insulation properties prevent circuit short circuits, and its thermal expansion compatibility with the PCB substrate reduces the risk of interface delamination and improves the durability of the package structure.

[0012] Preferably, the middle layer of the rigid PCB substrate is provided with an embedded interconnection circuit.

[0013] The embedded interconnect circuits achieve electrical connection between the front and back devices through a multi-layer design, avoiding surface wiring from occupying layout space and further reducing the size of the protection board; the shielding design of the inner layer circuits reduces electromagnetic interference, improves signal transmission accuracy, and prevents circuit oxidation or physical damage, ensuring long-term reliability.

[0014] Preferably, the solder ball array corresponds to the full matrix of FPC pads.

[0015] The solder balls and pads are perfectly matched in position, number and arrangement. The full matrix layout ensures precise alignment of the solder balls and FPC pads, reducing the length of the signal transmission path and impedance mismatch; the symmetrical design disperses welding stress, reduces the risk of solder joints falling off, adapts to a variety of FPC specifications, and improves product versatility.

[0016] Preferably, the length and width of the packaging structure are significantly smaller than those of a conventional single-sided plastic-sealed protective plate.

[0017] The double-sided layout and double-sided plastic sealing work together to significantly reduce the area of ​​the protection board, adapting to the internal space limitations of ultra-thin electronic devices; the compact design shortens the internal circuit path, improves signal response speed, and optimizes the real-time performance of the battery management system.

[0018] A method for manufacturing a double-sided plastic-sealed lithium battery protection plate comprises the following steps: (a) Mounting a battery protection chip and precision resistors on the front of a rigid PCB substrate; (b) Plastic encapsulation of the front device; (c) Mounting the MOS switch chip and solder ball array on the back of the rigid PCB substrate; (d) Plastic encapsulating the back-side device; (e) Grind the back plastic layer to expose the solder balls, and mechanically grind until the top of the solder balls are exposed.

[0019] The step-by-step placement and plastic encapsulation processes avoid conflicts in double-sided processing and improve production yield; the back grinding step accurately controls the thickness of the back plastic encapsulation layer to ensure consistent solder ball exposure height and guarantee welding reliability; independently optimized front and back process parameters reduce the impact of thermal stress on sensitive devices, making it suitable for large-scale and efficient production.

[0020] Preferably, when the back MOS is plastic-sealed in step (d), a staged pressure molding process is adopted, with low-pressure filling followed by high-pressure curing.

[0021] The staged pressure molding process uses the initial low-pressure stage to allow the epoxy molding compound (EMC) to flow evenly into the gap between the MOS switch chip and the PCB, avoiding bubbles or uneven filling caused by direct high-pressure injection; the subsequent high-pressure stage ensures that the EMC material is fully compacted to form a defect-free, dense protective layer. This process, combined with the requirements of double-sided plastic packaging, is particularly suitable for high-density device layouts, effectively preventing cracking of the back plastic packaging layer caused by material shrinkage or thermal expansion, while improving the overall mechanical strength of the packaging structure. By controlling the pressure in stages, It reduces stress impact on sensitive devices (such as precision resistors), ensures the stability of plastic-sealed devices on the front, and is suitable for industrial battery systems with high reliability requirements.

[0022] Preferably, after step (e), laser grooving is performed around the solder balls.

[0023] Laser grooving releases thermal stress between the back plastic layer and the solder balls, preventing structural cracking caused by temperature changes; the grooves accommodate excess solder, avoiding bridging short circuits between solder balls and improving soldering yield; the non-contact processing method ensures no mechanical damage and is suitable for the refined processing of high-density solder ball arrays.

[0024] Preferably, the depth of the laser groove is less than the thickness of the back plastic sealing layer, and the inner wall of the groove is a stepped structure, comprising at least two steps of different widths.

[0025] The stepped groove design is formed by laser ablation layer by layer. The groove depth is less than the thickness of the back plastic layer to avoid damaging the PCB substrate. At the same time, the stepped structure increases the mechanical bite force of the groove inner wall, preventing the back plastic layer from peeling from the groove edge due to temperature cycling or vibration. This design further releases thermal stress between the solder balls and the back plastic layer, reducing the risk of microcrack propagation, and accommodating excess solder that may overflow during soldering to prevent bridging short circuits. The stepped groove also enhances the interfacial bonding strength between the back plastic layer and the solder balls, ensuring the long-term reliability of the package structure in extreme environments (such as high humidity or salt spray), making it suitable for harsh application scenarios such as automotive batteries.

[0026] Preferably, the solder balls are formed into protruding structures by reflow soldering.

[0027] The reflow process causes the solder balls to melt and self-form into uniform protrusions, eliminating shape deviations and increasing solder contact area and conductivity. The protrusions are fixed in height after cooling, ensuring a tight connection with the FPC. At the same time, their flexibility absorbs mechanical stress and extends the life of the solder joints.

[0028] Preferably, the molding material is cured by a high-pressure molding process.

[0029] High-pressure molding ensures that the epoxy resin fully fills the gaps between devices, forming a bubble-free and delamination-free protective layer; the high fluidity of the material covers complex structures, providing uniform mechanical support and heat dissipation paths, enhancing the overall strength and heat dissipation efficiency of the package.

[0030] Preferably, before plastic-sealing the front device in step (b), the step further includes cleaning the rigid PCB substrate on which the device is mounted with flux.

[0031] Flux cleaning of rigid PCB substrates, where components are mounted, effectively removes residual flux and other impurities from the previous mounting process. Excessive residual flux after soldering can attract dust, moisture, and other impurities, affecting the electrical performance and long-term stability of the circuit board. Cleaning ensures surface cleanliness, allowing the subsequent front-side plastic encapsulation layer to adhere better to the PCB. This reduces gaps or delamination between the front-side plastic encapsulation layer and the PCB caused by impurities, improving the quality and effectiveness of the plastic encapsulation and enhancing the reliability and stability of the entire protective plate structure.

[0032] Preferably, before the plastic encapsulation in step (b), the protective chip on the front side is subjected to a low-fill glue treatment.

[0033] Before the front protective chip is plastic-sealed, a low-fill glue treatment is implemented, with the filling height lower than the chip surface, which is of great significance in many aspects. On the one hand, the low-fill glue can fill the tiny gap between the protective chip and the PCB, playing a role in mechanical fixation, enhancing the stability of the chip on the PCB, and reducing the risk of the chip loosening or even falling off due to external factors such as vibration and impact. On the other hand, the low-fill glue has good electrical insulation properties, which can effectively isolate the chip from the external environment, prevent static electricity, leakage and other problems from damaging the chip, and improve the safety and stability of the chip operation. In addition, the low-fill glue can also assist in heat dissipation, transferring the heat generated by the chip operation more evenly to the PCB and the front plastic sealing layer, which helps to improve the heat dissipation efficiency of the entire protective board and extend the service life of the chip.

[0034] Preferably, after the plastic sealing in step (b), the process further includes laser coding the plastic cover to identify the position of the individual modules.

[0035] Laser coding the plastic cover to identify the location of individual modules greatly facilitates production management and product traceability. During large-scale production, clear laser coding allows for quick and accurate identification of each protective plate module, facilitating the categorization and management of products across batches and models, improving production efficiency and quality control. If product issues arise and require tracing, the laser code can quickly locate information such as the module's production date, batch, and related production parameters, facilitating rapid analysis of the cause and implementation of appropriate corrective measures. Furthermore, laser coding is permanent and highly visible, resisting wear and erasure. It remains legible even in complex operating environments, ensuring the reliability and effectiveness of the marking.

[0036] The beneficial effects of the present invention compared to the prior art are: Space utilization and size optimization: Through a double-sided layout design, core components are mounted on the front and back sides of the PCB respectively, maximizing the use of circuit board space and significantly reducing the overall size of the protection board to meet the demand for lightweight and thin portable devices.

[0037] Improved protection: The front plastic layer provides comprehensive protection for the battery protection chip and precision resistors, isolating them from moisture, dust, and mechanical shock, ensuring long-term stability. The back plastic layer protects the MOS switch chip while exposing the solder ball array, ensuring reliable welding with the flexible printed circuit board (FPC). The overall structure is compact and highly resistant to environmental interference.

[0038] Improved welding reliability: The solder ball height design ensures full contact with the FPC pad, avoiding poor welding due to insufficient height. At the same time, the height difference prevents molten solder from overflowing onto the surface of the MOS switch chip and causing a short circuit. The protruding solder ball provides a buffer space during assembly, reducing the risk of damage to the device due to external impact.

[0039] Manufacturing process advantages: Step-by-step placement and plastic encapsulation processes avoid double-sided processing conflicts and improve production yield; the back grinding step accurately controls the thickness of the back plastic encapsulation layer to ensure consistent solder ball exposure height and guarantee welding reliability; independently optimized front and back process parameters reduce the impact of thermal stress on sensitive devices, making it suitable for large-scale and efficient production. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0041] Figure 1 This is an exploded view of the double-sided device layout and double-sided plastic-sealed lithium battery protection board structure according to one embodiment of the present invention.

[0042] Figure 2 This is a cross-sectional view of a lithium battery protection board structure with double-sided device layout and double-sided plastic sealing according to an embodiment of the present invention.

[0043] Explanation of reference numerals: rigid PCB substrate (1), battery protection chip (11), precision resistor (12), MOS switch chip (13), solder ball array (14), embedded interconnection circuit (15), front plastic sealing layer (2), back plastic sealing layer (3). DETAILED DESCRIPTION

[0044] To make the objectives, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Generally, the components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0045] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments in the present application without creative work are within the scope of protection of the present application.

[0046] It should be noted that similar numbers and letters represent similar items in the following figures, so once an item is defined in one figure, it does not need to be further defined and explained in the subsequent figures. In the description of the embodiments of the present application, it should be understood that the orientation or position relationship indicated by the terms "upper", "lower", "left", "right", "vertical", "horizontal", etc. is based on the orientation or position relationship shown in the drawings, or is the orientation or position relationship in which the product of the application is usually placed when in use, or is the orientation or position relationship commonly understood by those skilled in the art. It is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application.

[0047] It should be noted that, unless there is any conflict, the embodiments and features in the embodiments of this application can be combined with each other.

[0048] The technical solution in this application will be described below with reference to the accompanying drawings. Example 1

[0049] This embodiment provides a lithium battery protection board structure with a double-sided device layout and double-sided plastic encapsulation, comprising a rigid PCB substrate 1, a front plastic encapsulation layer 2 covering the front, and a back plastic encapsulation layer 3 covering the back. A battery protection chip 11 and a precision resistor 12 are mounted on the front of the rigid PCB substrate 1, while a MOS switch chip 13 and a solder ball array 14 are mounted on the back. The front plastic encapsulation layer 2, covering the front, protects the battery protection chip 11 and the precision resistor 12. The back plastic encapsulation layer 3, covering the back, encapsulates the MOS switch chip 13 and exposes the solder ball array 14. The soldering height of the solder ball array 14 is higher than the surface of the MOS switch chip 13.

[0050] Through a double-sided layout design, core components are mounted on both sides of the PCB, maximizing board space and significantly reducing the overall size of the protection board, meeting the demand for lightweight and thin portable devices. The front plastic layer 2 provides comprehensive protection for the battery protection chip 11 and precision resistor 12, isolating them from moisture, dust, and mechanical shock, ensuring long-term stability. The back plastic layer 3 protects the MOS switch chip 13 while exposing the solder ball array 14, ensuring reliable welding with the flexible circuit board (FPC). The overall structure is compact and highly resistant to environmental interference. The height design of the solder balls 14 ensures full contact with the FPC pads, avoiding poor welding caused by insufficient height. At the same time, the height difference prevents molten solder from overflowing onto the surface of the MOS switch chip 13 and causing a short circuit. The protruding solder balls 14 provide a buffer during assembly, reducing the risk of damage from external impact.

[0051] In this embodiment, the surface of the back plastic packaging layer 3 is provided with a concave-convex texture to increase the contact area with the external heat dissipation component.

[0052] The concave-convex texture is pre-designed in the mold to increase the surface area of ​​the back plastic layer 3 and improve heat dissipation efficiency. The double-sided plastic structure itself has a high thermal capacity. Combined with the surface texture design, it can quickly transfer the heat generated by the MOS switch chip 13 to the external heat sink or device housing, avoiding performance degradation or shortened life due to heat accumulation. The texture structure also enhances the mechanical bond between the back plastic layer 3 and the heat dissipation interface material such as thermal conductive silicone grease, preventing interface separation caused by vibration or temperature changes, making it suitable for high-power battery management systems.

[0053] In this embodiment, the back plastic sealing layer 3 is formed by using epoxy molding compound EMC through a molding process.

[0054] Epoxy resin molding compound (EMC) has excellent high temperature resistance and chemical corrosion resistance. The molding process can evenly wrap the MOS switch chip 13 to form a dense protective layer to prevent the chip from failing due to environmental factors or mechanical stress. The high insulation of EMC avoids circuit short circuits, and its thermal expansion matching with the PCB substrate reduces the risk of interface delamination, thereby improving the durability of the packaging structure.

[0055] In this embodiment, an embedded interconnection circuit 15 is provided on the middle layer of the rigid PCB substrate 1 .

[0056] The embedded interconnect circuit 15 uses a multi-layer design to achieve electrical connection between the front and back devices, avoiding surface wiring from occupying layout space and further reducing the size of the protection board; the shielding design of the inner layer circuit reduces electromagnetic interference, improves signal transmission accuracy, and prevents circuit oxidation or physical damage, ensuring long-term reliability.

[0057] In this embodiment, the solder ball array 14 corresponds to the full matrix of the FPC pads.

[0058] The full matrix layout ensures precise alignment of the solder balls 14 with the FPC pads, reducing signal transmission path length and impedance mismatch; the symmetrical design disperses welding stress, reduces the risk of solder joints falling off, adapts to a variety of FPC specifications, and improves product versatility.

[0059] In this embodiment, the length and width of the packaging structure are significantly smaller than those of a conventional single-sided plastic-sealed protective plate.

[0060] The double-sided layout and double-sided plastic sealing work together to significantly reduce the area of ​​the protection board, adapting to the internal space limitations of ultra-thin electronic devices; the compact design shortens the internal circuit path, improves signal response speed, and optimizes the real-time performance of the battery management system. Example 2

[0061] This embodiment provides a method for manufacturing a double-sided plastic-sealed lithium battery protection plate, comprising the following steps: Step (a): Mount the battery protection chip and precision resistor on the front of the rigid PCB substrate.

[0062] Step (b): Plastic-encapsulate the front device. In this step, before plastic-encapsulating the front device, the rigid PCB substrate on which the device is mounted is also cleaned of flux. This can effectively remove the flux and other impurities remaining on the PCB surface during the previous mounting process, ensure the cleanliness of the PCB surface, and enable the subsequent front plastic-encapsulation layer to better fit the PCB, reducing the gap or delamination between the front plastic-encapsulation layer and the PCB due to the presence of impurities, improving the quality and effect of plastic-encapsulation, and enhancing the reliability and stability of the entire protection board structure. In addition, before plastic-encapsulation in step (b), the front protection chip is also subjected to low-fill glue treatment. Low-fill glue can fill the tiny gap between the protective chip and the PCB, acting as a mechanical fixation, enhancing the chip's stability on the PCB and reducing the risk of the chip loosening or even falling off due to external forces such as vibration and impact. It also has excellent electrical insulation properties, effectively isolating the chip from the external environment, preventing damage to the chip from static electricity, leakage, and other problems, and improving the safety and stability of chip operation. It also assists in heat dissipation, more evenly transferring the heat generated by the chip to the PCB and the front plastic layer, helping to improve the heat dissipation efficiency of the entire protective board and extend the chip's service life. In addition, after the plastic encapsulation in step (b), the plastic cover is laser-coded to identify the location of the individual modules. This greatly facilitates production management and product traceability. During large-scale production, clear laser coding can quickly and accurately identify each protection board module, making it easier to classify and manage products of different batches and models, thereby improving production efficiency and quality control. When a product has a problem and needs to be traced, the laser code can quickly locate the module's production time, production batch, and related production parameters, helping to quickly analyze the cause of the problem and take corresponding improvement measures. Moreover, laser coding is permanent and high-definition, not easily worn or erased, and can remain clearly legible for a long time even in complex usage environments, ensuring the reliability and effectiveness of the identification.

[0063] Step (c): Mount the MOS switch chip and solder ball array on the back of the rigid PCB substrate.

[0064] Step (d): Plastic encapsulate the back-side components. The back-side MOS is plastic encapsulated using a staged pressure molding process, initially filling at low pressure followed by high-pressure curing. The staged pressure molding process uses an initial low-pressure stage to evenly flow the epoxy molding compound (EMC) into the gap between the MOS switch chip and the PCB, preventing bubbles or uneven filling caused by direct high-pressure injection. The subsequent high-pressure stage ensures that the EMC material is fully compacted, forming a dense, defect-free protective layer. This process, combined with the requirements of double-sided plastic encapsulation, is particularly suitable for high-density device layouts, effectively preventing cracking in the back-side plastic encapsulation layer due to material shrinkage or thermal expansion, while also improving the overall mechanical strength of the package structure. By controlling the pressure in stages, stress on sensitive components (such as precision resistors) is reduced, ensuring the stability of the plastic-encapsulated components on the front side, making it suitable for industrial battery systems with high reliability requirements.

[0065] Step (e): Grind the back plastic layer to expose the solder balls. After step (e), laser grooves are formed around the solder balls. Laser grooves release thermal stress between the back plastic layer and the solder balls, preventing structural cracking caused by temperature changes. The grooves accommodate excess solder, preventing bridging short circuits between solder balls and improving soldering yield. The non-contact processing method ensures no mechanical damage and is suitable for the refined processing of high-density solder ball arrays. The depth of the laser grooves is less than the thickness of the back plastic layer, and the inner wall of the grooves has a stepped structure. The stepped groove design is formed by laser ablation layer by layer. The groove depth is less than the thickness of the back plastic layer to avoid damaging the PCB substrate. At the same time, the stepped structure increases the mechanical bite force of the inner wall of the groove, preventing the back plastic layer from peeling from the groove edge due to temperature cycling or vibration. This design further releases thermal stress between the solder balls and the back plastic layer, reduces the risk of microcrack propagation, and accommodates excess solder that may overflow during soldering to prevent bridging short circuits. The stepped grooves also enhance the interfacial bonding strength between the back plastic layer and the solder balls, ensuring the long-term reliability of the packaging structure in extreme environments (such as high humidity or salt spray), making it suitable for harsh application scenarios such as automotive batteries.

[0066] In this embodiment, the solder balls are reflowed to form raised structures. The reflow process causes the solder balls to melt and self-shape into uniform raised structures, eliminating shape deviations and increasing solder contact area and conductivity. The raised structures stabilize in height after cooling, ensuring a tight connection to the FPC. Their flexibility also absorbs mechanical stress, extending solder joint life.

[0067] In this embodiment, the encapsulation material is cured through a high-pressure molding process. High-pressure molding ensures that the epoxy resin fully fills the gaps between components, forming a bubble-free, delamination-free protective layer. The high fluidity of the material allows it to cover complex structures, providing uniform mechanical support and heat dissipation paths, enhancing the overall strength and heat dissipation efficiency of the package.

[0068] The beneficial effects of this embodiment are: The step-by-step placement and plastic sealing process avoids double-sided processing conflicts and effectively improves production yield.

[0069] The back grinding step precisely controls the thickness of the back plastic layer, ensuring consistent solder ball exposure height and guaranteeing soldering reliability.

[0070] Independently optimized front and back process parameters reduce the impact of thermal stress on sensitive devices and are suitable for large-scale and efficient production.

[0071] The staged pressure molding process is applied to the back-side MOS plastic package to prevent the back-side plastic package layer from cracking, improve the mechanical strength of the package structure, and reduce stress impact on sensitive devices.

[0072] The laser grooving process releases thermal stress, prevents bridging short circuits between solder balls, improves soldering yield, and is suitable for refined processing of high-density solder ball arrays.

[0073] The stepped groove design further releases thermal stress, enhances interface bonding strength, and ensures the long-term reliability of the packaging structure in extreme environments.

[0074] The raised solder balls formed by reflow soldering increase the soldering contact area and conductivity, thus extending the life of the solder joints.

[0075] The high-pressure molding process solidifies the plastic packaging material, forming a high-quality protective layer, which enhances the overall strength of the package and the heat dissipation efficiency.

[0076] Operations such as cleaning flux from the rigid PCB substrate for mounted devices, performing low-fill glue treatment on the front protection chip, and laser coding on the plastic cover improve the quality of plastic packaging, chip stability, and the convenience of production management and product traceability from different aspects. Example 3

[0077] This embodiment provides a method for manufacturing a double-sided plastic-sealed lithium battery protection plate, comprising the following steps: Step (a): Prepare a rigid PCB substrate and precisely mount the battery protection chip and precision resistor on its front, ensuring that the mounting positions are accurate and meet the circuit design requirements.

[0078] Step (b): First, clean the flux from the rigid PCB substrate on which the components are mounted. Use professional cleaning agents and cleaning equipment, and follow the prescribed cleaning process and parameters to ensure that the flux and other impurities on the PCB surface are completely removed. Then, perform low-fill dispensing on the protective chip on the front. Select a suitable low-fill material and use the dispensing equipment to evenly fill the low-fill glue into the tiny gap between the protective chip and the PCB. The dispensing amount and dispensing position must strictly comply with the process requirements. Next, perform plastic encapsulation on the front device. Using a high-pressure molding process, the plastic encapsulation material is filled around the front device under high temperature and high pressure to form a uniform, bubble-free plastic encapsulation layer. Finally, perform laser coding on the plastic cover. Use the laser coding equipment to clearly mark the position of the single module on the plastic cover. The laser code contains key information such as production time and batch.

[0079] Step (c): Mount the MOS switch chip and solder ball array on the backside of the rigid PCB substrate. High-precision placement equipment accurately positions the MOS switch chip in the designated location, and a reflow process forms the solder ball array. During the reflow process, parameters such as soldering temperature and time are strictly controlled to ensure that the solder balls melt and self-form into a uniform raised structure with a height that meets the design requirements.

[0080] Step (d): Plastic encapsulation of the backside components. A staged pressure molding process is used for plastic encapsulation of the backside MOS. First, during the low-pressure stage, epoxy molding compound (EMC) is slowly injected into the gap between the MOS switch chip and the PCB. The process is held for a certain amount of time to allow the EMC to flow evenly and fill the gap. Then, during the high-pressure stage, higher pressure is applied to ensure that the EMC material is fully compacted and forms a dense protective layer.

[0081] Step (e): Use a grinding machine to grind the back plastic layer, precisely controlling the grinding thickness to expose the solder balls at a consistent height. After grinding, laser grooves are created around the solder balls. Laser parameters are set to ensure the groove depth is less than the thickness of the back plastic layer and the inner wall of the groove has a stepped structure. During the laser groove process, ensure the dimensional and shape accuracy of the grooves to meet design requirements.

[0082] After completing the above steps, a double-sided plastic-encapsulated lithium-ion battery protection board was successfully manufactured. Performance testing and reliability verification of the board demonstrated that all performance indicators met design requirements, significantly improved production yield, demonstrated high welding reliability, and operated stably under varying environmental conditions.

[0083] Based on Example 3, some process parameters were fine-tuned. For example, during the flux cleaning process in step (b), the cleaning agent concentration and cleaning time were adjusted, for example, to a concentration of 5%-10% and a cleaning time of 30-60 seconds. During the staged pressure molding process in step (d), the pressure values ​​and durations of the low-pressure and high-pressure stages were varied. Testing revealed that these fine-tuned process parameters were still capable of producing high-quality double-sided plastic-encapsulated lithium battery protection boards, with some performance improvements, further demonstrating the flexibility and adaptability of the present manufacturing method.

[0084] In summary, the present invention provides a method for manufacturing a double-sided plastic-sealed lithium battery protection plate, which effectively solves the problems existing in the prior art through a series of innovative process steps and optimized process parameters, and has significant advantages and good application prospects.

[0085] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A lithium battery protection board structure with double-sided device layout and double-sided plastic sealing, characterized in that: include A rigid PCB substrate (1) having a battery protection chip (11) and a precision resistor (12) mounted on its front side and a MOS switch chip (13) and a solder ball array (14) mounted on its back side; A front plastic sealing layer (2) covering the front of the rigid PCB substrate (1) to protect the battery protection chip (11) and the precision resistor (12); A back plastic sealing layer (3) covering the back of the rigid PCB substrate (1), encapsulating the MOS switch chip (13) and exposing the solder ball array (14); Wherein, the soldering height of the solder ball array (14) is higher than the surface of the MOS switch chip (13).

2. The double-sided device layout and double-sided plastic-sealed lithium battery protection board structure according to claim 1, characterized in that: The surface of the back plastic sealing layer (3) is provided with a concave-convex texture to increase the contact area with the external heat dissipation component.

3. The double-sided device layout and double-sided plastic-sealed lithium battery protection board structure according to claim 1, characterized in that: The back plastic sealing layer (3) is formed by a molding process using epoxy molding compound (EMC), and the middle layer of the rigid PCB substrate (1) is provided with an embedded interconnection circuit (15).

4. The double-sided device layout and double-sided plastic-sealed lithium battery protection board structure according to claim 1, characterized in that: The solder ball array (14) corresponds to the full matrix of the FPC solder pads.

5. A method for manufacturing a double-sided plastic-sealed lithium battery protection plate, characterized in that: The method for manufacturing a lithium battery protection board structure with a double-sided device layout and double-sided plastic sealing as described in any one of claims 1 to 4 comprises the following steps: (a) Mounting a battery protection chip and precision resistors on the front of a rigid PCB substrate; (b) Plastic encapsulation of the front device; (c) Mounting the MOS switch chip and solder ball array on the back of the rigid PCB substrate; (d) Plastic encapsulating the back-side device; (e) Grind the backside plastic layer to expose the solder balls.

6. The method for manufacturing a double-sided plastic-sealed lithium battery protection plate according to claim 5, characterized in that: When the back MOS is plastic-sealed in step (d), a staged pressure molding process is adopted, with low-pressure filling followed by high-pressure curing.

7. The method for manufacturing a double-sided plastic-sealed lithium battery protection plate according to claim 5, characterized in that: After step (e), laser grooving is performed around the solder balls.

8. The method for manufacturing a double-sided plastic-sealed lithium battery protection plate according to claim 5, characterized in that: The depth of the laser groove is less than the thickness of the back plastic sealing layer, and the inner wall of the groove has a stepped structure.

9. The method for manufacturing a double-sided plastic-sealed lithium battery protection plate according to claim 5, characterized in that: The solder balls are formed into convex structures through reflow soldering, and the plastic packaging material is solidified through a high-pressure molding process.

10. The method for manufacturing a double-sided plastic-sealed lithium battery protection plate according to claim 5, characterized in that: Before the front device is plastic-sealed in step (b), the process also includes cleaning the flux from the rigid PCB substrate on which the device is mounted and performing low-fill glue treatment on the front protection chip; after the front device is plastic-sealed in step (b), the process also includes laser coding the plastic cover to identify the position of a single module.

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