Waterproof multilayer circuit board

Abstract

The utility model relates to electronic component manufacturing technical field, specifically discloses a waterproof multilayer circuit board, including by at least two layers of conductive layer and at least one layer of insulating substrate alternative lamination constitutes the circuit board main part, the outer surface of circuit board main part is provided with at least one layer of the encapsulation waterproof layer of integrated molding, and the encapsulation waterproof layer completely covers circuit board main part upper surface, lower surface and all side edges. Through the encapsulation waterproof layer of integrated molding completely covering circuit board main part surface and edge, combining multilayer waterproof structure and through -hole protection design, form continuous dense waterproof barrier, solved the water vapor penetration problem that traditional circuit board led to because of the incomplete waterproof layer or coating cracking, has the advantage that significantly improves waterproof performance and reliability.

Description

Technical Field

[0001] This utility model relates to the field of electronic component manufacturing technology, specifically a waterproof multilayer circuit board. Background Technology

[0002] Multilayer circuit boards (PCBs), as core components of modern electronic devices, directly impact the reliability of the entire device. With the continuous expansion of electronic device applications, PCBs frequently face harsh operating conditions such as humidity, rain, and even immersion in special environments like communication base stations, automotive electronics, medical equipment, and wearable devices. Traditional PCBs have significant shortcomings in waterproofing performance, mainly in the following aspects: First, conventional surface treatment processes are insufficient to form a complete waterproof barrier, allowing moisture to easily penetrate the PCB through edges or vias; second, existing waterproof coatings are mostly single-layer structures, prone to micro-cracks under thermal expansion and contraction or mechanical stress; third, for PCBs with metallized vias, the via ends often become weak points in waterproofing. These defects lead to problems such as short circuits, conductor corrosion, and insulation degradation when PCBs are used in humid environments, severely affecting the operational stability and lifespan of electronic devices. Especially in high-temperature and high-humidity environments such as 5G base stations and automotive engine compartments, circuit failures due to insufficient waterproofing have become one of the main factors restricting product reliability. Utility Model Content

[0003] To address the shortcomings of existing technologies, this utility model provides a waterproof multilayer circuit board, which achieves all-round waterproof protection through an integrally molded waterproof encapsulation layer, effectively preventing moisture from penetrating from the surface and edges of the circuit board, and significantly improving the reliability and service life of the circuit board in humid environments.

[0004] This application provides a waterproof multilayer circuit board, the technical solution of which is as follows:

[0005] The circuit board body comprises a circuit board body consisting of at least two conductive layers and at least one insulating substrate layer stacked alternately. The outer surface of the circuit board body is provided with at least one integrally formed waterproof encapsulation layer, which completely covers the upper surface, lower surface and all sides of the circuit board body.

[0006] Furthermore, this application also proposes that the encapsulated waterproof layer includes a first waterproof layer and a second waterproof layer arranged sequentially from the inside to the outside. The first waterproof layer is a parylene coating with a thickness of 5-30 micrometers; the second waterproof layer is a polyurethane resin layer or an epoxy resin layer with a thickness of 50-200 micrometers.

[0007] Furthermore, this application also proposes that the circuit board body has through mounting holes, and the inner wall of the mounting holes is also covered with an encapsulation waterproof layer.

[0008] Furthermore, this application also proposes that a metallized via be provided in the mounting through hole, and the end of the metallized via be covered by a waterproof encapsulation layer.

[0009] Furthermore, this application also proposes that the outer surface of the encapsulated waterproof layer is coated with a hydrophobic nano-coating.

[0010] Furthermore, this application also proposes that the insulating substrate is an epoxy glass cloth laminate, a polytetrafluoroethylene board, or a ceramic substrate.

[0011] As can be seen from the above, the waterproof multilayer circuit board and its encapsulated waterproof layer structure provided in this application completely cover the surface and edges of the circuit board body through an integrally formed encapsulated waterproof layer. Combined with the multilayer waterproof structure and through-hole protection design, a continuous and dense waterproof barrier is formed, which solves the problem of water vapor penetration caused by incomplete waterproof layer or coating cracking of traditional circuit boards. It has the advantages of significantly improving waterproof performance and reliability. Attached Figure Description

[0012] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0013] Figure 1 This is a schematic diagram of the structure of this utility model;

[0014] Figure 2 This is a schematic diagram of the main structure of the circuit board of this utility model;

[0015] Figure 3 This is a schematic diagram of the waterproof layer structure of this utility model.

[0016] In the diagram: 1. Circuit board body; 101. Conductive layer; 102. Insulating substrate; 103. Encapsulation waterproof layer; 1031. First waterproof layer; 1032. Second waterproof layer; 2. Mounting through hole; 3. Metallized via. Detailed Implementation

[0017] The following drawings will disclose several embodiments of this utility model. For clarity, many practical details will be described in the following description. However, it should be understood that these practical details should not be used to limit this utility model. That is, in some embodiments of this utility model, these practical details are not essential. In addition, for the sake of simplicity, some conventional structures and components will be shown in the drawings in a simple schematic manner.

[0018] Please see Figure 1-3In existing technologies, multilayer circuit boards, as core components of electronic devices, have long faced reliability challenges in humid environments. Traditional manufacturing processes typically employ localized coating or sealant treatment on the circuit board surface; however, due to limitations in material properties and processing methods, achieving complete sealing is difficult. For example, in automotive engine compartments or outdoor communication equipment, liquid water can seep through capillary action along interlayer gaps, causing oxidation and short circuits in the internal conductive layer 101, and a decrease in dielectric properties after the insulating substrate 102 absorbs water, severely impacting the equipment's lifespan.

[0019] To address these issues, researchers discovered that existing waterproofing measures suffer from incomplete coverage and weak interfacial adhesion. Analysis of water vapor penetration pathways revealed that the edges of the circuit board and mounting holes are the primary channels for liquid intrusion. By studying the film-forming properties of polymer materials, they attempted to shift the packaging structure from localized repair to complete encapsulation. Based on interfacial chemistry theory, a polymer material with excellent adhesion was selected, and a seamless protective layer was formed through a continuous film-forming process.

[0020] Therefore, this application proposes a circuit board body 1 consisting of at least two conductive layers 101 and at least one insulating substrate 102 stacked alternately, with at least one integrally formed encapsulation waterproof layer 103 disposed on the outer surface of the circuit board body 1, the encapsulation waterproof layer 103 completely covering the upper surface, lower surface and all sides of the circuit board body 1.

[0021] The integrally molded waterproof encapsulation layer 103 refers to a continuous protective film layer formed by chemical vapor deposition or impregnation molding processes. Specifically, it can be achieved using parylene vapor deposition, a process that can form a pinhole-free film on complex surfaces, eliminating seam defects caused by traditional coatings. Completely covering the upper surface, lower surface, and all sides of the circuit board body 1 means that the protective layer covers all exposed interfaces. This can be achieved through three-dimensional encapsulation technology, ensuring that moisture cannot penetrate the interlayer structure from the board edges or holes.

[0022] Specifically, the waterproof encapsulation layer 103 is formed through a material deposition process under vacuum after the circuit board has undergone etching and lamination. This layer forms a dense molecular-level structure on the substrate surface, effectively blocking the penetration paths of liquid and gaseous water. During the encapsulation process, by controlling the deposition angle and material flowability, the protective layer completely covers the top, bottom, and surrounding sidewalls of the board, eliminating uncovered areas present in traditional dispensing processes. The encapsulation layer is chemically bonded to the substrate, preventing peeling due to differences in thermal expansion coefficients.

[0023] Compared to existing technologies, traditional methods employ a split sealing structure, using silicone rings to press and seal the edges of the circuit board, which creates assembly gaps that can lead to water leakage. This solution creates seamless protection through overall encapsulation, completely eliminating all-directional penetration channels. Existing technologies often use locally sprayed waterproof coatings, which can create uneven thickness areas at board corners. This solution, however, utilizes vapor deposition technology to achieve isotropic film formation, ensuring uniform protective layer thickness.

[0024] Through the above technical solution, this application effectively blocks the capillary penetration of liquid water along the edge of the board into the interlayer structure, preventing electrochemical corrosion of the conductive layer 101 in a humid environment. The encapsulation layer forms a physical isolation on the circuit board surface, preventing water molecules from directly contacting the metal lines and causing short circuit faults. This structure significantly improves the long-term operational stability of the equipment in rain and high humidity environments while maintaining the original circuit board size.

[0025] This application further proposes that the encapsulated waterproof layer 103 includes a first waterproof layer 1031 and a second waterproof layer 1032 arranged sequentially from the inside to the outside. The first waterproof layer 1031 is a parylene coating with a thickness of 5-30 micrometers; the second waterproof layer 1032 is a polyurethane resin layer or an epoxy resin layer with a thickness of 50-200 micrometers.

[0026] The parylene coating refers to a polymer film formed through chemical vapor deposition, specifically using a vacuum deposition process. This coating fills the micropores on the circuit board surface and forms a pinhole-free covering layer, thereby blocking the penetration path of water molecules. The polyurethane resin layer or epoxy resin layer refers to a thermosetting polymer layer formed through spraying or impregnation processes, specifically using a two-component curing process. This coating forms a protective layer with a certain degree of elasticity through a cross-linking reaction, used to resist the damage to the internal structure caused by external mechanical stress. The thickness of the first waterproof layer 1031 can be controlled between 5 and 30 micrometers, for example, by using a multiple deposition process to achieve uniform coverage; the thickness of the second waterproof layer 1032 can be controlled between 50 and 200 micrometers, for example, by adjusting the number of spraying operations to control the cumulative thickness of the coating.

[0027] Specifically, after the parylene coating is applied to the circuit board surface, its molecular structure can tightly adhere to the interface between the conductor and the substrate, eliminating the coverage blind spots caused by surface tension in traditional coating materials. The subsequent formation of a polyurethane or epoxy resin layer forms a continuous protective film through cross-linking and curing, providing impact resistance while maintaining flexibility. The composite structure of the two materials forms a gradient protection system, with the inner layer blocking moisture penetration through its molecularly dense structure and the outer layer resisting physical damage through mechanical strength, thereby maintaining the dryness of the circuit board interior in humid environments.

[0028] Compared to existing technologies, traditional single-layer waterproof coatings are prone to stress cracking during thermal expansion and contraction, leading to protective failure. However, the composite structure of parylene and polyurethane or epoxy resin complements each other's material properties. The former, with its low elastic modulus, alleviates deformation stress, while the latter maintains structural integrity through its high cross-linking density. Their synergistic effect prevents coating cracking. Furthermore, the low-temperature deposition process of parylene avoids the impact of high temperatures on circuit board components, solving the substrate deformation problem caused by traditional high-temperature curing coatings.

[0029] Through the above technical solution, this application achieves all-round anti-penetration protection for circuit boards. In long-term humid and hot environments, it can effectively prevent water molecules from penetrating the internal circuits through the gaps between conductors. At the same time, the mechanical protection of the outer layer material extends the service life of the waterproof coating, solving the problem of metal circuit oxidation and short circuit caused by coating cracking or penetration in existing circuit boards.

[0030] This application further proposes that the circuit board body 1 has a through mounting hole 2, and the inner wall of the mounting hole 2 is also covered with an encapsulation waterproof layer 103.

[0031] Among them, the mounting via 2 refers to a hole-like structure that penetrates the thickness direction of the multilayer circuit board. It can be implemented by mechanical drilling or laser drilling processes and is used to fix the pins of electronic components or to achieve interlayer electrical connections. The encapsulation waterproof layer 103 refers to a continuous protective structure that completely covers the outer surface of the circuit board. It can be formed by vapor deposition or spraying processes using a parylene coating or a polyurethane resin coating and is used to prevent liquid from penetrating into the interior of the circuit board along the inner wall of the via.

[0032] Specifically, after the conductive layer 101 and the insulating substrate 102 are laminated together on the circuit board body 1, through-holes 2 are formed through the board body using a drilling process. Subsequently, during the preparation of the waterproof layer 103, a directional spraying or vacuum coating process is used to uniformly adhere the waterproof material to the inner wall surface of the through-hole, forming a sealed structure that is integrated with the waterproof layer on the outer surface of the circuit board. This process allows the inner wall of the through-hole and the outer surface of the circuit board to form a gapless protective layer simultaneously, effectively eliminating liquid penetration channels caused by the lack of a waterproof layer in the through-hole area in traditional processes.

[0033] Compared to existing technologies, traditional circuit boards only waterproof the outer planar area of ​​the board, neglecting the protection requirements of the inner walls of the mounting vias. This solution, through a process that simultaneously covers the inner walls of the vias with a waterproof layer, fundamentally solves the problem of internal circuit corrosion caused by liquid axial penetration along the vias, making it particularly suitable for harsh working environments that require resistance to liquid splashes or water pressure penetration.

[0034] Through the above technical solution, this application achieves comprehensive waterproof protection for the three-dimensional structure of the circuit board, with a focus on strengthening the protection capability of the mounting via 2, a traditionally weak waterproof area. This design can effectively prevent liquid from entering the circuit board through the inner wall of the via, avoiding interlayer short circuits or signal transmission abnormalities caused by moisture in the metallized via 3, and significantly improving the working stability of the circuit board in humid environments.

[0035] This application further proposes that a metallized via 3 is provided in the mounting through hole 2, and the end of the metallized via 3 is covered by a waterproof encapsulation layer 103.

[0036] The metallized via 3 refers to a conductive metal layer formed on the inner wall of a through-hole in a circuit board through-hole by chemical plating or electroplating. Specifically, it can be made of metals such as copper, nickel, or gold, and is used to achieve electrical connections between different conductive layers 101. The encapsulated waterproof layer 103 covers the ends of the metallized via 3, meaning the waterproof material completely encapsulates the opening edges of the metallized via 3 on the upper and lower surfaces of the circuit board. Specifically, it can be achieved using a composite structure of a parylene coating and a polyurethane resin layer, used to block the path of liquid penetration along the metal-substrate interface.

[0037] Specifically, after a metallized via 3 is formed within the mounting via 2, its end is exposed on the circuit board surface to form a conductive contact. By extending the encapsulation waterproof layer 103 to cover the edge of the metallized via 3, the minute gap between the metallized via 3 and the insulating substrate 102 can be eliminated. When the circuit board is in a humid environment, the continuous barrier formed by the encapsulation waterproof layer 103 can prevent moisture from penetrating into the internal conductive layer 101 through the contact interface between the metallized via 3 and the substrate, while maintaining the surface flatness for normal operation of the conductive contacts.

[0038] Compared to existing technologies, the ends of metallized vias on traditional circuit boards are typically directly exposed. The difference in thermal expansion coefficients between the vias and the substrate can easily lead to microcracks at the interface, becoming a preferred path for moisture intrusion. This solution eliminates this weak point by completely encapsulating the ends with a waterproof layer 103, achieving comprehensive sealing protection for the interface between the conductive contacts and the substrate.

[0039] Through the above technical solution, this application effectively prevents moisture from seeping into the circuit board through the contact interface between the metallized via 3 and the substrate, avoiding short circuits or corrosion caused by moisture in the metal lines, and improving the long-term working reliability of the multilayer circuit board in a humid environment.

[0040] This application further proposes that the outer surface of the encapsulated waterproof layer 103 is also coated with a hydrophobic nano-coating.

[0041] Hydrophobic nanocoatings refer to material layers with low surface energy formed through chemical vapor deposition or spraying processes, specifically using fluorosilane compounds or silica nanoparticle dispersions. This coating increases the water contact angle by creating a micro-rough structure, thereby forming a physical barrier against liquid water on the encapsulation layer surface.

[0042] Specifically, a hydrophobic nano-coating is applied to the outermost layer of the encapsulation waterproof layer 103, with hydrophobic groups in its molecular structure arranged outwards to form a dense protective layer. When the circuit board is exposed to a high-humidity environment, liquid water forms spherical droplets on the coating surface due to surface tension and rolls off quickly, preventing water from penetrating into the encapsulation layer through capillary action. This coating and the encapsulation waterproof layer 103 form a synergistic protective system, where the encapsulation layer provides basic barrier function, and the hydrophobic layer further eliminates surface liquid water residue.

[0043] Compared to existing technologies, traditional circuit boards rely solely on a single-layer resin encapsulation structure for waterproofing, and their surfaces still suffer from water film residue due to the hydrophilicity of the materials. This solution adds a hydrophobic nano-coating, preventing liquid water from forming a continuous liquid film on the circuit board surface, fundamentally blocking the path of water penetration through microcracks or pores in the encapsulation layer.

[0044] Through the above technical solution, this application effectively reduces the amount of liquid water adsorbed by the circuit board under rain, condensation or short-term immersion conditions, avoids water retention on the surface of the encapsulation layer to form an osmotic pressure difference, thereby improving the long-term working reliability of the multilayer circuit board in a humid environment.

[0045] This application further proposes a waterproof multilayer circuit board, wherein the insulating substrate 102 is an epoxy glass cloth laminate, a polytetrafluoroethylene board, or a ceramic substrate.

[0046] Among them, epoxy glass cloth laminate refers to a composite material formed by hot-pressing and curing epoxy resin-impregnated glass fiber cloth. It can be achieved using FR-4 standard boards and possesses high mechanical strength and low moisture absorption, maintaining structural stability in humid environments. Polytetrafluoroethylene (PTFE) board refers to a laminated substrate with PTFE as the main material. It can be achieved using high-frequency circuit-specific substrates, exhibiting low surface energy and strong chemical inertness, effectively blocking water molecule penetration. Ceramic substrate refers to a sintered body with alumina or aluminum nitride as the main components. It can be prepared using a low-temperature co-fired ceramic process, possessing excellent thermal stability and zero water absorption, making it suitable for high-temperature and high-humidity environments.

[0047] Specifically, the epoxy glass cloth laminate forms a physical barrier through its dense resin-glass fiber composite structure, with a moisture absorption rate controlled below 0.1%. During the circuit board stacking process, it can form a tight interface with the conductive layer 101, preventing moisture from penetrating along the interlayer gaps. The polytetrafluoroethylene (PTFE) board, with its strong hydrophobic properties due to the fluorocarbon bonds, allows liquid water to form beaded contact angles on its surface. Simultaneously, its acid and alkali corrosion resistance prevents ionic contaminants in moisture from corroding the internal circuitry. The ceramic substrate, through its closed-cell structure formed by sintering, completely isolates the liquid penetration path. Its coefficient of thermal expansion matches that of the encapsulation waterproof layer 103, allowing for coordinated deformation during drastic temperature changes to prevent cracking of the protective layer.

[0048] Compared to existing technologies, traditional multilayer circuit boards mostly use ordinary epoxy resin substrates or phenolic paper substrates, whose moisture absorption rate is generally higher than 0.5%. In humid environments, the substrate is prone to expansion, leading to the breakage of the conductive layer 101. While polytetrafluoroethylene (PTFE) material has waterproof properties, it has previously only been used in single-layer high-frequency circuits and has not been combined with multilayer lamination processes. Ceramic substrates in existing technologies are mostly used as independent heat dissipation substrates and have not formed a composite waterproof structure with the epoxy resin encapsulation layer.

[0049] Through the above technical solution, this application effectively reduces the water absorption of the insulating substrate 102 and blocks the path of moisture diffusion into the circuit board through the pores of the substrate. Among them, the epoxy glass cloth laminate is suitable for conventional electronic equipment, the polytetrafluoroethylene board meets the requirements of high-frequency signal transmission, and the ceramic substrate is suitable for high-temperature working environments. The selection of these three types of materials enables the waterproof circuit board to adapt to different application environments, fundamentally avoiding interlayer delamination or oxidation of conductive lines caused by substrate water absorption.

[0050] The above description is merely an embodiment of this utility model and is not intended to limit the scope of this utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of this utility model should be included within the scope of the claims of this utility model.

Claims

1. A waterproof multilayer circuit board, comprising a circuit board body (1) formed by alternatingly stacking at least two conductive layers (101) and at least one insulating substrate (102), characterized in that: The outer surface of the circuit board body (1) is provided with at least one integrally formed encapsulation waterproof layer (103), which completely covers the upper surface, lower surface and all sides of the circuit board body (1).

2. The waterproof multilayer circuit board according to claim 1, characterized in that: The encapsulated waterproof layer (103) includes a first waterproof layer (1031) and a second waterproof layer (1032) arranged sequentially from the inside to the outside. The first waterproof layer (1031) is a parylene coating with a thickness of 5-30 micrometers. The second waterproof layer (1032) is a polyurethane resin layer or an epoxy resin layer with a thickness of 50-200 micrometers.

3. A waterproof multilayer circuit board according to claim 1, characterized in that: The circuit board body (1) has a through mounting hole (2), and the inner wall of the mounting hole (2) is also covered with a waterproof encapsulation layer (103).

4. A waterproof multilayer circuit board according to claim 3, characterized in that: The mounting through hole (2) is provided with a metallized via (3), and the end of the metallized via (3) is covered by a waterproof encapsulation layer (103).

5. A waterproof multilayer circuit board according to claim 1, characterized in that: The outer surface of the encapsulated waterproof layer (103) is also coated with a hydrophobic nano-coating.

6. A waterproof multilayer circuit board according to claim 1, characterized in that: The insulating substrate (102) is an epoxy glass cloth laminate, a polytetrafluoroethylene board, or a ceramic substrate.

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