A manufacturing method of a printed circuit board cavity island structure

Abstract

The application discloses a manufacturing method of a printed circuit board cavity island structure and relates to the field of printed circuit boards. The manufacturing method of the printed circuit board cavity island structure comprises the following steps: preparing a sub-board laminated structure containing a target cavity region; processing a blind groove by adopting an optical positioning depth control milling process, and the depth tolerance is controlled within ±0.05 mm; embedding a polymer gasket with non-stick characteristics, such as a polytetrafluoroethylene gasket coated with a nano-silicon dioxide coating; performing post-process treatment after overall lamination; and extracting the gasket laterally to form a double-through cavity structure. The lamination parameters and the gasket size are accurately controlled, the cavity structure meets high-precision requirements, the Z direction penetrates through multiple conductive layers, and the XY plane lateral opening width and the side wall angle are accurate. The application has the advantages of high-precision cavity structure, good manufacturability, clear steps, simple and reliable process, and convenience for large-scale production, and provides a more reliable solution for high-end electronic manufacturing.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of printed circuit board, in particular to a manufacturing method of a printed circuit board cavity island structure. BACKGROUND

[0002] Cavity technology has been widely applied in various fields, including wireless communication, automotive electronics, high-speed computing and radio frequency applications, etc. For example, in 5G antenna modules, cavity design can effectively solve the problem of signal transmission loss and achieve autonomous control. In addition, cavity technology also shows its superior performance in high-end automotive electronics and power amplifiers, etc.

[0003] However, the traditional printed circuit board cavity structure mostly uses mechanical milling blind slot or chemical etching process. The traditional process has the following shortcomings:

[0004] Firstly, the precision problem: the traditional mechanical milling blind slot process relies on the physical cutting of the tool, and its machining precision is limited by factors such as equipment rigidity, tool wear and vibration, resulting in poor matching of blind slot depth and filling material. For example, the physical cutting process is prone to cause interlayer stress concentration, which eventually causes product or cavity structure deformation. Although the chemical etching process can realize blind slot machining with certain precision, it is limited by the uniformity of etching liquid and reaction time control, and it is difficult to meet the demand of high-precision cavity structure.

[0005] Secondly, the risk of material residue: conventional filling materials are prone to adhere to the PCB substrate during processing, making it difficult to remove later. Even if removed by chemical dissolution or mechanical peeling, etc., material debris or chemicals may be left in the cavity inner wall, affecting the cleanliness and electrical performance of the cavity. For example, in high-frequency radio frequency applications, residual materials may cause signal reflection or increased loss, reducing device performance.

[0006] Thirdly, the process complexity problem: the traditional process needs multiple processing and detection, such as first processing blind slot, then filling material, and finally removing the filler, each step needs to be controlled and detected independently, resulting in long production cycle and high cost, and multiple processing is easy to introduce cumulative error, reducing the yield. In view of the shortcomings of the prior art, the present application provides a manufacturing method of a printed circuit board cavity island structure to solve the above problems. SUMMARY

[0007] In view of the shortcomings of the prior art, the present application provides a manufacturing method of a printed circuit board cavity island structure. The traditional printed circuit board cavity structure manufacturing process has three core problems of insufficient precision, material residue and process complexity, which limits its application in high-precision and high-performance electronic devices. The present application solves the above problems by innovative process design, providing a more reliable solution for high-end electronic manufacturing.

[0008] In order to achieve the above object, the present application is implemented by the following technical scheme: a manufacturing method of a printed circuit board cavity island structure, comprising the following steps:

[0009] Step S1, preparing a sub-board, laminating to form a sub-board stack structure containing a target cavity region;

[0010] Step S2, processing a blind groove, processing a blind groove on the surface of the laminated sub-board by an optical positioning depth control milling process;

[0011] Step S3, embedding a removable gasket, placing a polymer gasket with non-stick properties into the blind groove, the gasket length being greater than the blind groove length to form an operation margin;

[0012] Step S4, overall lamination, pressing the sub-board with an external laminated plate, so that the polymer gasket is covered in the stack;

[0013] Step S5, post-process treatment, processing a through hole and surface treatment on the printed board after lamination;

[0014] Step S6, removing the gasket, extracting the polymer gasket from the side to form a double-pass cavity structure connected laterally.

[0015] Preferably, the optical positioning depth control milling process adopts a closed-loop control system composed of a CCD vision system and a piezoelectric ceramic feedback module, and the blind groove depth tolerance is controlled within ±0.05mm.

[0016] Preferably, the polymer gasket is polytetrafluoroethylene, and its physical properties meet:

[0017] Shore hardness 20-25D;

[0018] Surface roughness ;

[0019] Density .

[0020] Preferably, the surface of the polymer gasket is coated with a nano-silicon dioxide coating, the coating thickness is 50-100nm, and the surface energy .

[0021] Preferably, the gasket length in step S3 is 2-5mm longer than the blind groove, and the thickness is 0.05-0.15mm smaller than the blind groove depth.

[0022] Preferably, the overall lamination process parameters of step S4 are: the pressure is controlled within 1.0-1.5MPa; and temperature is controlled in stages during the lamination process: the initial stage is set to 50-100℃, the time length is controlled within 20min, the middle stage temperature is set to 150℃, the time length is controlled within 30min, and the tail stage temperature is set to 200℃, the time length is controlled within 60min.

[0023] Preferably, the double-through cavity structure satisfies:

[0024] The Z direction penetrates at least 6 conductive layers;

[0025] The XY plane lateral opening width is 105-110% of the blind slot width;

[0026] The cavity side wall and the horizontal plane angle is 85-90°.

[0027] Preferably, the spacer removal in step S6 adopts a hard metal tool with a rectangular cross section to apply a lateral pushing force, and the pushing force is 10-15 N.

[0028] Preferably, after step S5, solder mask baking is performed:

[0029] From 50℃ to 150℃, the temperature is increased by 2℃ / min per stage; every 20℃ is a stage, and each stage is kept for 10 min; finally, 150℃ is kept for 60 min.

[0030] Preferably, the laminated sub-plate comprises:

[0031] At least 6 layers of prepreg sheets and alternately stacked copper foils;

[0032] The blind slot is processed in the L3-L12 sub-plate layer, corresponding to the D5-D10 layer cavity position;

[0033] The outer laminated plate comprises L1-L2 and L13-L14 laminated structures.

[0034] The beneficial effects thereof are as follows:

[0035] 1. The printed circuit board cavity island structure manufacturing method, first, the finished product has a high-precision cavity structure, by adopting the optical positioning depth control milling process and the accurate spacer size design, the blind slot depth tolerance and the cavity structure size can be strictly controlled, and the high-precision double-through cavity structure is formed. The cavity penetrates multiple conductive layers in the Z direction, the XY plane lateral opening width and the cavity side wall and the horizontal plane angle all satisfy the accurate design requirements, which provides stable and accurate installation space for components in electronic equipment, and is beneficial to improve the performance and reliability of electronic equipment, second, the finished product has good manufacturability, the design of removable spacer and the selection of polymer spacer material with non-stick characteristics make the spacer easy to operate in the embedding and removing process, and reduce the damage to the printed circuit board. Third, the overall manufacturing method steps are clear, the process operation is simple and reliable, and it is convenient for large-scale production and manufacturing, which can improve the production efficiency and product consistency.

[0036] 2、The manufacturing method of the printed circuit board cavity island structure has optimized electrical performance. The double-pass cavity structure provides a better heat dissipation channel for the printed circuit board, which can effectively reduce the temperature of the components during operation and reduce the problem of electrical performance degradation caused by temperature rise. In addition, the precise via processing and surface treatment process ensure the electrical connection reliability between layers, reduce signal transmission loss, improve the high-frequency and high-speed performance of the printed circuit board, and are suitable for electronic devices with high electrical performance requirements.

[0037] 3、The manufacturing method of the printed circuit board cavity island structure has wide application adaptability. The manufacturing method can flexibly adjust the size, shape and position of the cavity structure, and select different surface treatment processes according to different electronic device requirements to meet the requirements of different application scenarios. Whether it is in the fields of aerospace, communication equipment or consumer electronics, etc., the manufacturing method can be used to produce printed circuit boards that meet specific requirements, and has wide market application prospects. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and those skilled in the art can obtain other drawings according to these drawings without creative labor.

[0039] Figure 1 The method flowchart of the present application;

[0040] Figure 2 The layering legend schematic diagram of the present application;

[0041] Figure 3 The cavity island schematic diagram of the present application. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0043] In order to better understand the above technical solutions, the above technical solutions will be described in detail in combination with the drawings in the specification and specific embodiments.

[0044] Embodiment 1, the present embodiment discloses a manufacturing method of a printed circuit board cavity island structure, according to the drawingsFigures 1-3 As shown, the method comprises the following steps:

[0045] Step S1: Preparation of sub-plate;

[0046] First, the preparation of the sub-plate is carried out, and a sub-plate laminated structure containing a target cavity region is formed through a lamination process. Specifically, the laminated sub-plate contains at least 6 layers of prepreg sheets and alternately laminated copper foils. The prepreg sheet is a commonly used material in the manufacture of printed circuit boards, which is composed of resin and reinforcing material. The reinforcing material can be a glass fiber cloth, which can soften and solidify under the conditions of heating and pressure, firmly bonding the copper foils together. The copper foil is the basic material for forming the circuit pattern. By alternately laminating the prepreg sheet and the copper foil, a sub-plate with a multi-layer structure can be constructed.

[0047] In this embodiment, the blind slot is processed in the L3-L12 sub-plate layer, corresponding to the D5-D10 layer cavity position. This specific layer design is to meet the subsequent requirement of forming a cavity island structure. By accurately controlling the position of the blind slot in the sub-plate layer, it can ensure that the final formed cavity structure meets the design requirements. For example, in some high-frequency high-speed electronic devices, the signal transmission performance requirements of printed circuit boards are extremely high. By reasonably designing the cavity structure, the loss and interference in the signal transmission process can be effectively reduced, and the performance stability of the device can be improved.

[0048] Step S2: Processing of blind slot;

[0049] The blind slot is processed on the surface of the laminated sub-plate through an optical positioning controlled depth milling process. According to the attached Figure 2 As shown, the optical positioning controlled depth milling process adopts a closed-loop control system composed of a CCD vision system and a piezoelectric ceramic feedback module. This closed-loop control system has high precision. The CCD vision system can capture image information of the sub-plate surface in real time, determine the processing position of the blind slot through image processing algorithm, and realize accurate optical positioning. The piezoelectric ceramic feedback module can monitor the tool position and processing depth in real time during milling, and feed back the monitoring data to the control system. The control system adjusts the processing parameters in time according to the feedback information, ensuring that the blind slot depth tolerance is controlled within 0.05mm.

[0050] The accuracy of blind slot processing mainly affects the accuracy of subsequent cavity structure formation. If the blind slot depth tolerance is too large, it may cause uneven gap when embedding the removable gasket, which will affect the overall lamination effect, so that the polymer gasket cannot be accurately covered, and finally affect the quality of the cavity island structure. For example, in the field of aerospace electronics, the reliability requirements of printed circuit boards are extremely high, and any slight processing error may cause the device to malfunction in extreme environments, so high-precision blind slot processing technology is an important link to ensure product quality.

[0051] Step S3: Embed the removable gasket;

[0052] A non-stick polymer gasket is placed into the blind groove, with the gasket length exceeding the blind groove length to create an operating margin. In this embodiment, the polymer gasket is polytetrafluoroethylene (PTFE), whose physical properties meet the requirements of Shore hardness 20-25D and surface roughness... ,density Polytetrafluoroethylene (PTFE) possesses excellent non-stick properties, chemical stability, and high-temperature resistance, making it uniquely advantageous as a removable gasket in printed circuit board manufacturing.

[0053] A Shore hardness of 20-25D ensures the gasket possesses a certain degree of flexibility, allowing it to deform appropriately without cracking during embedding in blind slots and subsequent lamination, while simultaneously possessing sufficient hardness to maintain its shape and ensure stable support when forming cavity structures. Surface roughness This makes the gasket surface smooth, reducing friction with surrounding materials and facilitating lateral removal in subsequent steps. Density This ensures that the gasket has a certain quality, can be better positioned when embedded in the blind slot, and is not easy to move during the lamination process.

[0054] Furthermore, the polymer gasket surface is coated with a nano-silica coating, with a coating thickness of 50-100 nm and a surface energy... The nano-silica coating further enhances the non-stick properties of the gasket, reducing the adhesion between the gasket and surrounding materials, making gasket removal easier and reducing damage to the printed circuit board surface. Simultaneously, the low surface energy also helps prevent the gasket from sticking to surrounding materials during lamination, ensuring the integrity of the cavity structure.

[0055] According to the appendix Figure 2 As shown in the diagram, in step S3, the length of the gasket is 2-5mm longer than the blind groove, and its thickness is 0.05-0.15mm less than the depth of the blind groove. The 2-5mm difference in length provides an operational margin, facilitating the operator's gripping and manipulation during gasket insertion and removal. The 0.05-0.15mm difference in thickness creates a gap between the gasket and the bottom of the blind groove after insertion. This gap allows for some resin flow during the overall lamination process, ensuring uniform coating of the polymer gasket after lamination. It also helps reduce friction between the gasket and the bottom of the blind groove during removal, making the removal process smoother.

[0056] Step S4: Perform overall lamination;

[0057] The sub-board is pressed together with the outer laminate, encapsulating the polymer gasket within the laminate. The outer laminate comprises L1-L2 and L13-L14 laminated structures. The overall lamination process parameters are: pressure controlled at 1.0-1.5 MPa; and temperature control is implemented in stages during lamination: the initial stage is set at 50℃-100℃ for 20 minutes, the middle stage at 150℃ for 30 minutes, and the final stage at 200℃ for 60 minutes.

[0058] According to the appendix Figure 2 As illustrated, precise pressure control is crucial during the overall lamination process. Maintaining pressure within the range of 1.0-1.5 MPa ensures sufficient bonding between the sub-board and the outer laminate, allowing the resin to evenly fill the spaces between layers and achieve a good adhesion. Insufficient pressure may lead to weak interlayer bonding and delamination; while excessive pressure may damage the printed circuit board structure, such as crushing copper foil or causing excessive deformation of the prepreg sheet.

[0059] Secondly, the overall lamination process also requires precise temperature segmentation control. The initial stage temperature is set at 50℃-100℃ for 20 minutes. This stage primarily softens the resin gradually, preparing it for subsequent full flow and bonding. The middle stage temperature is set at 150℃ for 30 minutes, at which point the resin reaches a suitable flow state, fully filling the gaps between layers and achieving good interlayer bonding. The final stage temperature is set at 200℃ for 60 minutes. This high-temperature stage ensures complete resin curing, forming a stable structure and ensuring the printed circuit board has sufficient mechanical strength and electrical properties. This segmented temperature control ensures the lamination process proceeds gradually, allowing the resin's performance to be fully utilized, thereby improving the quality of the printed circuit board.

[0060] Step S5: Perform post-processing;

[0061] The laminated printed circuit board (PCB) undergoes via fabrication and surface treatment. Visible via fabrication is used to achieve electrical connections between different layers. Visible vias are formed on the PCB using processes such as mechanical drilling or laser drilling, followed by hole metallization, which deposits a layer of conductive metal on the hole walls, thereby enabling electrical conduction between the layers.

[0062] Surface treatment is to improve the solderability, corrosion resistance of the printed circuit board surface. Common surface treatment process has chemical gold plating, electroplating nickel gold, tin spraying, etc. Chemical gold plating process can form a uniform and dense gold layer on the surface of the printed circuit board, so that the printed circuit board has good solderability and corrosion resistance, and is suitable for electronic equipment with high reliability requirements; electroplating nickel gold process is based on chemical gold plating, first plating a layer of nickel layer, and then plating a gold layer. The nickel layer can act as a barrier layer to prevent mutual diffusion between copper and gold, further improving the performance of the printed circuit board; the tin spraying process is to spray molten tin-lead alloy on the surface of the printed circuit board to form a tin layer, which has the advantages of low cost and simple process, and is widely used in the manufacture of general electronic products. In actual operation process, the surface treatment can be configured according to actual needs.

[0063] In this embodiment, after step S5, solder mask baking is performed: stepwise heating from 50℃ to 150℃, with a heating rate of 2℃ / min per stage; each 20℃ is a stage, and each stage is kept for 10min; finally, 150℃ is kept for 60min. The purpose of solder mask baking is to fully cure the solder mask ink and improve the adhesion and chemical corrosion resistance of the solder mask layer. By stepwise heating, the solder mask ink can be gradually heated, avoiding excessive internal stress of the ink due to rapid temperature rise, and cracks and other defects. Keeping for 10min at each stage ensures that the ink can fully react and cure at each temperature stage. Keeping for 60min at 150℃ can make the solder mask ink completely cured to form a stable and reliable solder mask layer to protect the circuit pattern on the printed circuit board from the influence of the external environment.

[0064] Step S6: removing the gasket;

[0065] The polymer gasket is pulled out from the side to form a double-channel structure that is laterally connected. According to the drawings Figure 3 As shown in the drawings, the gasket removal in step S6 uses a hard metal tool with a rectangular cross section to apply a lateral pushing force, and the pushing force is 10-15N. Using a hard metal tool with a rectangular cross section can ensure that the direction of the force is stable when the pushing force is applied, and it is not easy to deviate, so that the gasket can be accurately pulled out. The pushing force is controlled to be 10-15N, which can overcome the friction between the gasket and the surrounding material and smoothly pull out the gasket, and will not cause excessive stress to the printed circuit board, avoiding damage to the cavity structure or the surrounding circuit pattern.

[0066] Particularly disclosed, the double-pass cavity structure satisfies: the Z direction penetrates at least 6 conductive layers; the XY plane lateral opening width is 105-110% of the blind groove width; the cavity side wall and the horizontal plane form an angle of 85°-90°. The double-pass cavity structure with the Z direction penetrating at least 6 conductive layers can provide larger installation space and better heat dissipation channel for the elements in the electronic device, and is also conducive to realizing complex circuit layout and signal transmission. The XY plane lateral opening width is 105-110% of the blind groove width, and this size design ensures that after the gasket is removed, the cavity lateral opening is large enough for the installation and disassembly of the elements, and also avoids the problem that the opening is too large to cause instability of the cavity structure. The cavity side wall and the horizontal plane form an angle of 85°-90°, and the nearly vertical side wall design makes the cavity internal space utilization rate higher, and also facilitates the control of the size precision of the cavity during the manufacturing process.

[0067] Embodiment 2, this embodiment also discloses a manufacturing method of a printed circuit board cavity island structure, which is based on embodiment 1 and further optimizes part of process parameters and material properties to adapt to the needs of different application scenarios.

[0068] Step S1: preparing a sub-board;

[0069] The same as embodiment 1, a sub-board stack structure containing a target cavity region is formed through a laminating process, and the laminated sub-board contains at least 6 prepreg sheets and alternatingly stacked copper foils. The blind groove is processed in the L3-L12 sub-board layers, and corresponds to the D5-D10 layer cavity positions. However, in this embodiment, the resin content of the prepreg sheet is precisely controlled. According to different sub-board thicknesses and performance requirements, the prepreg sheet with a resin content of 40%-60% is selected. Precise control of the resin content can affect the flexibility and bonding performance of the sub-board. Higher resin content can make the sub-board softer, which is beneficial for subsequent processing and forming, but can reduce the mechanical strength of the sub-board. Lower resin content can improve the mechanical strength of the sub-board, but can affect the interlayer bonding effect. Therefore, by precisely controlling the resin content, the mechanical properties of the sub-board can be ensured while meeting the requirements of subsequent processing technology.

[0070] Step S2: processing the blind groove;

[0071] This embodiment still processes the blind groove by using the optical positioning depth-controlled milling process. The closed-loop control system is composed of a CCD vision system and a piezoelectric ceramic feedback module, and the blind groove depth tolerance is controlled to be within ±0.02 mm. The depth tolerance of the blind groove is controlled to be within ±0.02 mm, which can ensure the accuracy of the depth of the blind groove and the size of the cavity. 0.05mm. But in this embodiment, the milling tool is optimized, and a smaller diameter cemented carbide milling cutter is selected. The tool diameter is accurately matched according to the width of the blind groove, generally 0.8-0.9 times the width of the blind groove. Smaller tool diameter can reduce the cutting force in the machining process, reduce the damage to the surface of the sub-plate, and also help to improve the machining accuracy of the blind groove, making the side wall of the blind groove smoother, reducing the accumulation of resin on the side wall in the subsequent lamination process, and improving the quality of the cavity structure.

[0072] Step S3: embedding the removable gasket;

[0073] Polytetrafluoroethylene is selected as the polymer gasket, and the physical properties meet the Shore hardness of 20-25D, the surface roughness , the density , the surface is coated with a nano-silicon dioxide coating, the coating thickness is 50-100nm, and the surface energy . The length of the gasket is 3-4mm longer than the blind groove, and the thickness is 0.08-0.12mm smaller than the depth of the blind groove. In this embodiment, the surface flatness of the gasket is strictly controlled, and a high-precision flatness detection instrument is used to detect the surface of the gasket to ensure that the flatness error of the surface of the gasket is not more than 0.02mm. The flatness of the surface directly affects the fit between the gasket and the blind groove. If the surface of the gasket is uneven, it will cause uneven gaps after embedding in the blind groove, affecting the lamination effect and the quality of the cavity structure. By strictly controlling the flatness of the gasket surface, good fit between the gasket and the blind groove can be ensured, and the precision and stability of the cavity structure can be improved.

[0074] Step S4: overall lamination;

[0075] The sub-plate is pressed with an external lamination plate, and the external lamination plate includes L1-L2 and L13-L14 lamination structures. The overall lamination process parameters are: the pressure is controlled at 1.2-1.4MPa; the temperature is controlled in stages: the initial stage is set to 60-80℃, the time is controlled for 25min, the middle stage temperature is set to 150℃, the time is controlled for 35min, and the tail stage temperature is set to 200℃, the time is controlled for 70min. In this embodiment, in order to further improve the lamination quality, vacuum assisted technology is used in the lamination process. A vacuum chamber is set in the lamination equipment, and the vacuum chamber is vacuumized during the pressing process, so that the pressure in the lamination process is more uniform, and the air between the layers can be removed, reducing the generation of air bubbles between the layers, improving the tightness of the interlayer adhesion, and thus improving the overall performance of the printed circuit board.

[0076] Step S5: post-process treatment;

[0077] The printed board after lamination is processed for through-hole and surface treatment. In terms of through-hole processing, laser drilling process is adopted to replace part of mechanical drilling process. Laser drilling has the advantages of high precision, fast speed and small damage to the printed board, and is especially suitable for processing small-diameter through-holes. By accurately controlling laser parameters such as laser power, pulse frequency and focusing depth, through-holes of different diameters and depths are realized to meet the needs of different circuit designs.

[0078] In terms of surface treatment, different surface treatment processes are selected according to different application scenarios. For high-frequency and high-speed electronic devices, chemical gold plating process is adopted, and the thickness and uniformity of the gold layer are strictly controlled during the chemical gold plating process. The thickness of the gold layer is controlled between 0.05-0.1 μm, and the uniformity error is not more than 10%. The thin and uniform gold layer can reduce the loss in the process of signal transmission and improve the transmission quality of high-frequency signals.

[0079] After step S5, solder mask baking is performed: from 50℃ to 150℃ in steps, with a heating rate of 2℃ / min for each step; each step is 20℃, and each step is kept for 12min; finally, 150℃ is kept for 70min. Compared with Example 1, the holding time of each step is appropriately extended, which is to make the solder mask ink more fully cured and reacted on the printed circuit board with higher quality requirements, and further improve the performance of the solder mask layer. By extending the holding time, the solvent in the solder mask ink can be fully volatilized, and the resin can be fully cured to form a more dense and durable solder mask layer to better protect the circuit pattern on the printed circuit board.

[0080] Step S6: remove the gasket;

[0081] The polymer gasket is pulled out from the side, and a hard metal tool with a rectangular cross section is used to apply a lateral pushing force, with a pushing force of 12-14N. In this embodiment, in order to further improve the stability and accuracy of gasket removal, a force sensor and a displacement sensor are installed on the hard metal tool. The force sensor can monitor the pushing force applied to the gasket in real time, ensuring that the pushing force is always controlled within the range of 12-14N, avoiding problems caused by excessive or insufficient pushing force. The displacement sensor can accurately measure the movement distance of the gasket, and the operator can accurately control the pulling-out process of the gasket according to the feedback information of the displacement sensor, to ensure the size accuracy and quality stability of the cavity structure.

[0082] The working principle of the printed circuit board cavity island structure manufacturing method is as follows:

[0083] ​The manufacturing method is based on the multi-layer laminated structure and precision machining process of printed circuit boards. By machining blind grooves in the sub-plate and embedding removable shims, and then through overall lamination, post-process treatment and shim removal, a cavity island structure with a specific structure is formed. In the preparation of the sub-plate stage, the laminated structure containing the target cavity area is constructed through the lamination process, providing a basis for subsequent processing. When machining the blind groove, high-precision optical positioning depth control milling process is used to ensure the position and depth accuracy of the blind groove, providing a guarantee for the accurate embedding of the shim and the formation of the cavity structure.

[0084] After embedding the removable shim, the shim plays a supporting role during the overall lamination process, preventing resin from flowing into the blind groove to form a solid structure. Its non-stick properties and specific size design facilitate subsequent removal. The overall lamination process tightly bonds the layers, forming a stable printed circuit board structure. Post-process treatment completes the via processing and surface treatment, achieving electrical connection between layers and improving the surface performance of the printed circuit board. Finally, by precisely controlling the shim removal process, a double-pass cavity structure with lateral communication is formed, meeting the special needs of different electronic devices for printed circuit board structures.

[0085] The manufacturing method of the printed circuit board cavity island structure uses the following steps:

[0086] Sub-plate preparation: According to design requirements, select appropriate prepreg sheets and copper foil, and prepare a sub-plate laminated structure containing the target cavity area through lamination process, determine the position of the blind groove in the sub-plate layer.

[0087] Blind groove machining: Use a milling equipment equipped with a CCD vision system and a piezoelectric ceramic feedback module closed-loop control system to machine blind grooves on the laminated sub-plate surface, strictly control the blind groove depth tolerance within ±0.05mm.

[0088] Shim embedding: Select polytetrafluoroethylene shims with specific physical properties and surface coatings, determine the length and thickness of the shims according to the size of the blind groove, and accurately embed the shims into the blind groove to ensure good fit between the shims and the blind groove.

[0089] Overall lamination: Press the sub-plate with external laminated plates, control the pressure and temperature parameters according to process requirements, and use vacuum assisted technology to improve the lamination quality, so that the polymer shim is evenly covered in the laminated layer.

[0090] Post-process treatment: Process the laminated printed board through via processing, select appropriate processing technology such as mechanical drilling or laser drilling according to requirements; then perform surface treatment, select processes such as chemical gold plating, electroplated nickel gold or tin spraying according to application scenarios to improve the surface performance of the printed board.

[0091] Solder mask baking: the printed board is baked in a stepwise manner to make the solder mask ink fully cured, forming a stable and reliable solder mask layer.

[0092] Gasket removal: using a hard metal tool equipped with force and displacement sensors, the polymer gasket is pulled out from the side, controlling the pushing force and the gasket movement distance, forming a double-cavity structure with lateral communication.

[0093] As an embodiment, step S4 requires the tail section to be laminated at 200℃ for 60min, but the PTFE gasket (CTE=112ppm ) and FR-4 substrate (CTE=14ppm ) have a thermal expansion coefficient difference of 8 times. At high temperature, the gasket expands radially and presses the blind groove sidewall, causing the XY plane opening width to increase to 115% of the blind groove width (exceeding the 110% upper limit), and the residual stress after cooling causes the cavity island area to warp in the Z direction.

[0094] Therefore, to solve this problem, the present embodiment introduces a thermal compensation mold system, adds an adjustable graphite mold in the laminator, and the mold cavity is designed with a compensation coefficient according to the size of the blind groove. Through finite element simulation, it is found that when the mold sidewall inclination angle is set to 87° (compensation 3° thermal deformation) and the opening width is 98% of the blind groove width, the thermal expansion difference can be offset. The mold is equipped with carbon nanotube heating film, which is synchronized with the temperature control of the laminator, and actively heats the mold to 205℃ (precision 0.5℃) at 200℃ stage, and uses the negative CTE property of graphite (-1.5ppm ) to shrink the cavity size.

[0095] The mold is linked with the pressure plate through pneumatic connecting rods and is automatically locked and positioned when the pressure rises to 1.5MPa. Actual measurement shows that the cavity opening width fluctuation is compressed from 7% to 1.2%, and the Z-direction warping amount is reduced to 8 below. At the same time, the laminating parameters are optimized: the 200℃ tail section is shortened to 45min, and the heating rate is changed to 3℃ / min, reducing the thermal hysteresis effect.

[0096] The method for manufacturing the printed circuit board cavity island structure has the following beneficial effects:

[0097] ​The finished product has a high-precision cavity structure. By using an optical positioning depth control milling process and precise gasket size design, the blind slot depth tolerance and cavity structure size can be strictly controlled, forming a high-precision double-pass cavity structure. The cavity penetrates multiple conductive layers in the Z direction, and the XY plane lateral opening width and the cavity side wall angle with the horizontal plane both meet the precise design requirements, providing stable and accurate installation space for components in electronic devices, which is conducive to improving the performance and reliability of electronic devices.

[0098] The finished product has good manufacturability. The removable gasket design and the use of polytetrafluoroethylene material with non-stick properties make the gasket easy to operate during embedding and removal, reducing damage to the printed circuit board. At the same time, the overall manufacturing method has clear steps and controllable process parameters, facilitating large-scale production and manufacturing, and improving production efficiency and product consistency.

[0099] The finished product has optimized electrical performance. The double-pass cavity structure provides a better heat dissipation channel for the printed circuit board, effectively reducing the temperature of the components during operation and reducing the problem of electrical performance degradation caused by temperature rise. In addition, precise via processing and surface treatment processes ensure the reliability of electrical connections between layers, reduce signal transmission loss, improve the high-frequency and high-speed performance of the printed circuit board, and are suitable for electronic devices with high electrical performance requirements.

[0100] The finished product has wide application adaptability. This manufacturing method can flexibly adjust the size, shape and position of the cavity structure, and select different surface treatment processes according to different electronic device requirements, meeting the requirements of different application scenarios. Whether it is in the fields of aerospace, communication equipment or consumer electronics, this manufacturing method can produce printed circuit boards that meet specific requirements, and has wide market application prospects.

[0101] It should be noted that in this text, relational terms such as first and second are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between the entities or operations. Moreover, the terms "include", "contain" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or device. Without more limitations, the element defined by the statement "includes a" does not exclude the presence of additional identical elements in the process, method, article or device that includes the element.

[0102] The above shows and describes the basic principles and main features of the present application and the advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above embodiments, and the above embodiments and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for manufacturing a cavity-island structure of a printed wiring board, characterized by, The method comprises the following steps: Step S1, preparing a sub-board, laminating to form a sub-board stack structure containing a target cavity region; Step S2, processing a blind slot, processing a blind slot on the laminated sub-board surface by an optical positioning controlled-depth milling process; Step S3, embedding a removable gasket, placing a polymer gasket with non-stick properties into the blind slot, the gasket length being greater than the blind slot length to form an operation margin; Step S4, performing overall lamination, pressing the sub-board with an external laminated plate, so that the polymer gasket is covered in the stack; Step S5, performing post-process treatment, processing through-holes and surface treatment on the laminated printed board; Step S6, removing the gasket, extracting the polymer gasket from the side to form a double-pass cavity structure with lateral communication; The optical positioning controlled-depth milling process adopts a closed-loop control system composed of a CCD vision system and a piezoelectric ceramic feedback module, and the blind slot depth tolerance is controlled within ±0.05mm; The polymer gasket is polytetrafluoroethylene, and its physical properties meet the following requirements: Shore hardness 20-25D; Surface roughness ; Density ; The polymer gasket surface is coated with a nano-silica coating, coating thickness 50-100 nm, surface energy .

2. The method of claim 1, wherein the method further comprises: In step S3, the gasket length is 2-5mm longer than the blind slot, and the thickness is 0.05-0.15mm smaller than the blind slot depth.

3. The method of claim 1, wherein the method further comprises: The overall lamination process parameters in step S4 are: the pressure is controlled within 1.0-1.5MPa; and temperature is controlled in stages during the lamination process: the initial stage is set to 50-100℃, the time is controlled within 20min, the middle stage temperature is set to 150℃, the time is controlled within 30min, and the tail stage temperature is set to 200℃, the time is controlled within 60min.

4. The method of claim 1, wherein the method further comprises: The double-pass cavity structure meets the following requirements: Z-direction through at least 6 conductive layers; The XY plane lateral opening width is 105-110% of the blind slot width; The cavity side wall and the horizontal plane have an included angle of 85-90°.

5. The method of claim 1, wherein the method further comprises: In step S6, the gasket removal adopts a hard metal tool with a rectangular cross section to apply a lateral pushing force, and the pushing force is 10-15N.

6. The method of claim 1, wherein the method further comprises: After step S5, perform solder mask baking: From 50℃ to 150℃ in stages, each stage has a temperature rising rate of 2℃ / min; every 20℃ is a stage, and each stage has a holding time of 10min; finally, 150℃ is held for 60min.

7. The method of claim 1, wherein the method further comprises: The laminated sub-board comprises: At least 6 pre-impregnated sheet materials and alternately stacked copper foils; The blind slot is processed on the L3-L12 sub-board layer, corresponding to the D5-D10 layer cavity position; The external laminated plate comprises L1-L2 and L13-L14 laminated structures.

Images