Prepreg and multilayer circuit board
By introducing a fully cured PTFE layer and reinforcing materials into the prepreg, the drilling problem caused by insufficient prepreg hardness is solved, and the dielectric properties are improved, making it suitable for high-frequency and high-speed PCB products.
Patent Information
- Application Number
- CN202423077639.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-12
- Publication Date
- 2026-01-09
- Estimated Expiration
- 2034-12-12
AI Technical Summary
Existing prepregs have low hardness in high-frequency and high-speed PCB products, which makes them prone to stringing and hole clogging during drilling, and makes it difficult to meet dielectric performance requirements.
The structure includes a fully cured PTFE layer and two semi-cured resin layers. The fully cured PTFE layer contains reinforcing material, and the semi-cured resin layers are bonded to the core board. The fully cured PTFE layer is made of PTFE with low dielectric constant and low dielectric loss, and the reinforcing material is glass fiber cloth.
It improves the hardness of the prepreg, reduces wire pulling and hole clogging during drilling, and enhances dielectric properties to meet the requirements of high-frequency and high-speed PCB products.
Smart Images
Figure CN223777991U_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the field of circuit board technology, specifically relating to a prepreg and a multilayer circuit board. Background Technology
[0002] Prepreg, also known as PP sheet, is one of the main materials in the production of multilayer circuit boards, serving as an adhesive and insulator between multiple core boards. It mainly consists of reinforcing material and resin in a semi-cured state covering the reinforcing material. However, conventional prepregs often fail to meet dielectric performance requirements when used in high-frequency, high-speed PCB products. To reduce dielectric loss and improve dielectric performance, the common practice is to remove the reinforcing material and retain only the resin portion. This type of prepreg is called pure resin. However, pure resin has low hardness and is prone to stringing during drilling, with the resulting debris easily adhering to the hole walls, leading to hole blockage. Utility Model Content
[0003] The purpose of this application is to provide a prepreg and a multilayer circuit board, which aims to solve the technical problem in the prior art that the pure adhesive has low hardness, is prone to stringing during drilling, and is prone to hole blockage.
[0004] On the one hand, in order to achieve the above objectives, the technical solution adopted in this application is: a semi-cured sheet, comprising a fully cured PTFE layer and two semi-cured resin layers, wherein a reinforcing material is disposed in the fully cured PTFE layer, and the two semi-cured resin layers are respectively bonded to the opposite sides of the fully cured PTFE layer.
[0005] Compared with existing technologies, the advantages of the prepreg provided in this application are as follows: The prepreg can be used in the production of multilayer circuit boards, and the two semi-cured resin layers in the prepreg are used to bond to the two core boards respectively. The semi-cured resin layers have low hardness. By setting a fully cured PTFE layer between the two semi-cured resin layers and adding reinforcing materials within the fully cured PTFE layer, the two semi-cured resin layers can be supported, increasing the overall hardness of the prepreg. This reduces the likelihood of stringing when drilling holes in the fully cured prepreg, effectively reducing debris adhering to the hole walls and preventing hole blockage. Furthermore, the fully cured PTFE layer is made of PTFE with low dielectric constant and low dielectric loss, which improves the overall dielectric properties of the prepreg and meets the dielectric performance requirements of high-frequency and high-speed PCB products.
[0006] Furthermore, the ratio of the thickness of the fully cured PTFE layer to the thickness of the precured sheet is less than one-half.
[0007] Furthermore, the thickness of a single semi-cured resin layer is greater than or equal to 35 μm.
[0008] Furthermore, the semi-cured resin layer is one of a hydrocarbon resin layer, an epoxy resin layer, a polyimide resin layer, a BT resin layer, or a polyphenylene ether resin layer.
[0009] Furthermore, the reinforcing material is fiberglass cloth.
[0010] Furthermore, the fiberglass cloth is positioned at the middle of the thickness direction of the fully cured PTFE layer.
[0011] On the other hand, in order to achieve the above objectives, the technical solution adopted in this application is: a multilayer circuit board, including multiple stacked core boards and the above-mentioned prepreg, wherein an adhesive material layer is provided between each pair of adjacent core boards, at least one adhesive material layer is a prepreg, and the two prepreg resin layers of the same prepreg are respectively bonded to the two adjacent core boards.
[0012] Compared with the prior art, the circuit board provided in this application has the following advantages: It uses the aforementioned prepreg, in which two semi-cured resin layers are bonded to two adjacent core boards. The semi-cured resin layers have low hardness. By setting a fully cured PTFE layer between the two semi-cured resin layers and incorporating reinforcing material within the fully cured PTFE layer, the two semi-cured resin layers can be supported, increasing the overall hardness of the prepreg. This reduces the likelihood of stringing when drilling holes in the fully cured prepreg, effectively reducing debris adhering to the hole walls and preventing hole blockage. Furthermore, the fully cured PTFE layer is made of PTFE with low dielectric constant and low dielectric loss, which improves the overall dielectric properties of the prepreg and meets the dielectric performance requirements of high-frequency, high-speed PCB products.
[0013] Furthermore, the core board includes an intermediate insulating layer and two circuit layers, which are respectively disposed on opposite sides of the intermediate insulating layer, and the semi-cured resin layer is bonded to the circuit layers.
[0014] Furthermore, the intermediate insulating layer includes one of the following: a polytetrafluoroethylene resin layer, a hydrocarbon resin layer, an epoxy resin layer, a polyimide resin layer, a BT resin layer, or a polyphenylene ether resin layer.
[0015] Furthermore, the number of core boards is three or more, and at least one adhesive material layer includes one of the following: a polytetrafluoroethylene resin layer, a hydrocarbon resin layer, an epoxy resin layer, a polyimide resin layer, a BT resin layer, or a polyphenylene ether resin layer. Attached Figure Description
[0016] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0017] Figure 1 This is a schematic diagram of the structure of the prepreg provided in Embodiment 1 of this application;
[0018] Figure 2 This is a schematic diagram of the structure of a multilayer circuit board provided in Embodiment 2 of this application.
[0019] The following are the labeling elements in the figure:
[0020] 100. Prepreg;
[0021] 10. Fully cured PTFE layer;
[0022] 20. Semi-cured resin layer;
[0023] 30. Reinforcing materials;
[0024] 200. Core board;
[0025] 201. Intermediate insulation layer;
[0026] 202. Line layer. Detailed Implementation
[0027] The embodiments of this application are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.
[0028] In the description of this application, it should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.
[0029] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.
[0030] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.
[0031] Prepreg, also known as PP sheet, is one of the main materials in the production of multilayer circuit boards. It plays a role in bonding and insulating between multilayer core boards. It mainly consists of reinforcing materials and resin covering the reinforcing materials. Common reinforcing materials include fiberglass cloth, paper-based materials, and composite materials. Prepreg used in the production of multilayer circuit boards generally uses fiberglass cloth as the reinforcing material. The prepreg is made by impregnating treated fiberglass cloth with resin, and then heat-treating it to bring the resin into the B-stage.
[0032] The resin curing process can be divided into three stages: stage A, stage B, and stage C. In stage A, the resin is a flowing liquid at room temperature; in stage B, the resin is partially cross-linked and in a semi-cured state, resembling a gel. The resin in this stage can soften under heating and pressure, and then react and cure upon cooling; in stage C, the resin is fully cross-linked and in a completely cured state, resembling a solid. This is also the state of the resin after the prepreg and the core board are bonded together under high temperature and pressure.
[0033] However, conventional prepregs often fail to meet dielectric performance requirements when used in high-frequency, high-speed PCB products. To reduce dielectric loss and improve dielectric performance, the common practice is to remove the reinforcing material and retain only the resin portion. These prepregs are known as pure resin. However, pure resin has low hardness and is prone to stringing during drilling. The resulting debris easily adheres to the hole walls and is difficult to remove, leading to hole blockage. Therefore, this application provides a prepreg that not only solves the hole blockage problem during drilling but also meets the dielectric performance requirements of high-frequency, high-speed PCB products. The specific structure of this prepreg is detailed below:
[0034] Example 1
[0035] like Figure 1 As shown, this embodiment provides a semi-cured sheet 100, including a fully cured PTFE layer 10 and two semi-cured resin layers 20. The fully cured PTFE layer 10 is provided with reinforcing material 30, and the two semi-cured resin layers 20 are respectively bonded to the opposite sides of the fully cured PTFE layer 10.
[0036] The prepreg 100 can be used in the production of multilayer circuit boards. The two semi-cured resin layers 20 in the prepreg 100 are used to bond to two core boards respectively. The semi-cured resin layers 20 have relatively low hardness. By setting a fully cured PTFE layer 10 between the two semi-cured resin layers 20 and incorporating reinforcing material 30 within the fully cured PTFE layer 10, the two semi-cured resin layers 20 can be supported, increasing the overall hardness of the prepreg 100. This reduces the likelihood of stringing when drilling holes in the fully cured prepreg 100, effectively reducing debris adhering to the hole walls and preventing hole blockage. Furthermore, the fully cured PTFE layer 10 is made of PTFE (Polytetrafluoroethylene), which has a low dielectric constant and low dielectric loss, improving the overall dielectric properties of the prepreg 100 and meeting the dielectric performance requirements of high-frequency, high-speed PCB products.
[0037] In this embodiment, the fully cured PTFE layer 10 is in stage C of resin curing, meaning it is fully cured and solid, with a higher hardness than the semi-cured resin layer 20, providing support for the semi-cured resin layer 20. The semi-cured resin layer 20 is in stage B of resin curing, meaning it is semi-cured and capable of bonding with the core board. When the semi-cured resin layer 20 is bonded to the core board, it transforms from a semi-cured state to a fully cured state, and the semi-cured sheet 100 is fully cured.
[0038] Furthermore, the ratio of the thickness of the fully cured PTFE layer 10 to the thickness of the prepreg 100 is less than one-half. With a fixed thickness of the prepreg 100, by controlling the ratio of the thickness of the fully cured PTFE layer 10 to the thickness of the prepreg 100 to less than one-half, the prepreg resin layer 20 is ensured to have sufficient thickness, thereby guaranteeing reliable adhesion between the prepreg resin layer 20 and the core board.
[0039] Furthermore, the thickness of a single semi-cured resin layer 20 is greater than or equal to 35 μm, which ensures reliable adhesion between the semi-cured resin layer 20 and the core board. Specifically, the thickness of the semi-cured sheet 100 is generally designed to be 5 mil, or 127 μm, the total thickness of the two semi-cured resin layers 20 is greater than or equal to 70 μm, and the thickness of the fully cured PTFE layer 10 is less than 57 μm.
[0040] Furthermore, the semi-cured resin layer 20 is one of a hydrocarbon resin layer, an epoxy resin layer, a polyimide resin layer, a BT resin layer, or a polyphenylene ether resin layer.
[0041] Hydrocarbon resin, also known as petroleum resin, has excellent dielectric properties. The semi-cured resin layer 20 is formed by using hydrocarbon resin, which can improve the overall dielectric properties of the prepreg 100 and is suitable for the manufacture of high-frequency and high-speed PCBs. In addition, the hydrocarbon resin layer also has advantages such as good adhesion, low crosslinking density, high strength, high solid content, high temperature resistance, and good compatibility with a variety of materials.
[0042] Epoxy resin has excellent dielectric properties. The semi-cured resin layer 20 is formed by applying epoxy resin, which improves the overall dielectric properties of the prepreg 100, making it suitable for the fabrication of high-frequency, high-speed PCBs. In addition, the epoxy resin layer also has advantages such as high hardness, high strength, high temperature resistance, corrosion resistance, easy processing, and environmental safety.
[0043] Polyimide resin has excellent dielectric properties. The semi-cured resin layer 20 is formed by making polyimide resin, which can improve the overall dielectric properties of the prepreg 100 and is suitable for the manufacture of high-frequency and high-speed PCBs. In addition, the polyimide resin layer also has advantages such as high strength, high temperature resistance, and fatigue resistance.
[0044] BT resin, also known as bismaleimide triazine resin, possesses excellent dielectric properties. The semi-cured resin layer 20, formed by processing BT resin, improves the overall dielectric properties of the prepreg 100, making it suitable for high-frequency, high-speed PCB manufacturing. Furthermore, BT resin also offers advantages such as high temperature resistance, corrosion resistance, environmental friendliness, safety, and good processability.
[0045] Polyphenylene ether resin has excellent dielectric properties. The semi-cured resin layer 20 is formed by using polyphenylene ether resin, which can improve the overall dielectric properties of the prepreg 100, making it suitable for the fabrication of high-frequency and high-speed PCBs. In addition, polyphenylene ether resin also has advantages such as good mechanical properties, high temperature resistance, flame retardancy, low specific gravity, and good dimensional stability.
[0046] Furthermore, the reinforcing material 30 is fiberglass cloth. Fiberglass cloth has advantages such as good insulation, good heat resistance, good corrosion resistance, and high mechanical strength. By setting fiberglass cloth inside the fully cured PTFE layer 10, the overall strength of the prepreg 100 can be improved. Specifically, the fiberglass cloth is a mesh formed by multiple strands of fiberglass in the warp and weft directions, which has good structural stability and load-bearing capacity.
[0047] Furthermore, the fiberglass cloth is positioned at the midpoint of the thickness direction of the fully cured PTFE layer 10, meaning that the fully cured PTFE layer 10 is provided on both opposite sides of the fiberglass cloth, and the thickness of the fully cured PTFE layer 10 on each opposite side of the fiberglass cloth is consistent. By positioning the fiberglass cloth at the midpoint of the thickness direction of the fully cured PTFE layer 10, equal support can be provided to the two semi-cured resin layers 20, making the semi-cured sheet 100 flatter and less prone to bending.
[0048] Furthermore, the PTFE resin content in the fully cured PTFE layer 10 is 50%-80%. When the PTFE resin content is 50%-80%, the fully cured PTFE layer 10 has both sufficient strength and good dielectric properties.
[0049] Example 2
[0050] like Figure 2 As shown, this embodiment also provides a multilayer circuit board, including multiple stacked core boards 200 and a prepreg 100 of Embodiment 1. An adhesive material layer is provided between each pair of adjacent core boards 200, and at least one adhesive material layer is the prepreg 100 mentioned above. The two prepreg resin layers 20 of the prepreg 100 are respectively bonded to the two adjacent core boards 200.
[0051] The prepreg 100 of Example 1 is used. Two semi-cured resin layers 20 in the prepreg 100 are bonded to two adjacent core boards 200. The semi-cured resin layers 20 have low hardness. By setting a fully cured PTFE layer 10 between the two semi-cured resin layers 20 and incorporating reinforcing material 30 within the fully cured PTFE layer 10, the two semi-cured resin layers 20 can be supported, increasing the overall hardness of the prepreg 100. This reduces the likelihood of stringing when drilling holes in the fully cured prepreg 100, effectively reducing debris adhering to the hole walls and preventing hole blockage. Furthermore, the fully cured PTFE layer 10 is made of PTFE with low dielectric constant and low dielectric loss, improving the overall dielectric properties of the prepreg 100 and meeting the dielectric performance requirements of high-frequency, high-speed PCB products.
[0052] The number of core boards 200 is not limited. The figure shows two core boards 200, but in other embodiments, the number of core boards 200 can be three, four, five, or more. When the number of core boards 200 is three or more, at least one adhesive material layer includes one of a polytetrafluoroethylene resin layer, a hydrocarbon resin layer, an epoxy resin layer, a polyimide resin layer, a BT resin layer, or a polyphenylene ether resin layer. The polytetrafluoroethylene resin layer, hydrocarbon resin layer, epoxy resin layer, polyimide resin layer, BT resin layer, and polyphenylene ether resin layer all have good dielectric properties, meeting the dielectric performance requirements of high-frequency, high-speed PCB products. The adhesive material layer may also include fiberglass cloth; exemplaryly, the adhesive material layer can be a composite structure combining an epoxy resin layer and fiberglass cloth. Multiple adhesive material layers may be the same or different. For example, some adhesive material layers may be the prepreg 100 of Example 1, some adhesive material layers may be polytetrafluoroethylene resin layers or hydrocarbon resin layers, and some adhesive material layers may be a composite structure combining epoxy resin layers and fiberglass cloth. Of course, all adhesive material layers may be the prepreg 100 of Example 1.
[0053] The number of prepreg sheets 100 between two adjacent core boards 200 can be one. When the product thickness design changes, the thickness of the prepreg sheet 100 can be adjusted to meet the requirements without adjusting the product thickness by reducing or increasing the number of prepreg sheets 100.
[0054] Specifically, the core board 200 includes an intermediate insulating layer 201 and two circuit layers 202, which are respectively disposed on opposite sides of the intermediate insulating layer 201. A semi-cured resin layer 20 is bonded to the circuit layers 202. The intermediate insulating layer 201 includes one of a polytetrafluoroethylene resin layer, a hydrocarbon resin layer, an epoxy resin layer, a polyimide resin layer, a BT resin layer, or a polyphenylene ether resin layer. The polytetrafluoroethylene resin layer, hydrocarbon resin layer, epoxy resin layer, polyimide resin layer, BT resin layer, and polyphenylene ether resin layer all possess good dielectric properties, meeting the dielectric performance requirements of high-frequency and high-speed PCB products. The intermediate insulating layer 201 may also include fiberglass cloth; exemplarily, the intermediate insulating layer 201 can be a composite structure combining an epoxy resin layer and fiberglass cloth. The intermediate insulation layers 201 of the multiple core boards 200 may be the same or different. For example, some intermediate insulation layers 201 may be polytetrafluoroethylene resin layers or hydrocarbon resin layers, and some intermediate insulation layers 201 may be a composite structure of epoxy resin layers and glass fiber cloth.
[0055] It should be noted that, in addition to the resin materials themselves, the polytetrafluoroethylene resin layer, hydrocarbon resin layer, epoxy resin layer, polyimide resin layer, BT resin layer, and polyphenylene ether resin layer mentioned above may also include small amounts of additives, fillers, etc.
[0056] Depending on the specific type of product, among the multiple core boards 200, the core board 200 can be a rigid core board, meaning that the insulating dielectric layer of the core board 200 is not flexible, or the core board 200 can be a flexible core board, meaning that the insulating dielectric layer of the core board 200 is flexible. When the multilayer circuit board is composed of rigid core boards and flexible core boards to form a rigid-flex board, the prepreg 100 of Embodiment 1 is only disposed between the rigid core boards to avoid the prepreg 100 affecting the flexibility of the flexible core board.
[0057] It should be noted that the above are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the scope of protection of this application.
Claims
1. A semi-cured sheet, characterized in that, It includes a fully cured PTFE layer and two semi-cured resin layers. The fully cured PTFE layer contains reinforcing material, and the two semi-cured resin layers are respectively bonded to opposite sides of the fully cured PTFE layer.
2. The prepreg according to claim 1, characterized in that: The ratio of the thickness of the fully cured PTFE layer to the thickness of the precured sheet is less than one-half.
3. The prepreg according to claim 1, characterized in that: The thickness of a single semi-cured resin layer is greater than or equal to 35 μm.
4. The prepreg according to claim 1, characterized in that: The semi-cured resin layer is one of a hydrocarbon resin layer, an epoxy resin layer, a polyimide resin layer, a BT resin layer, or a polyphenylene ether resin layer.
5. The prepreg according to claim 1, characterized in that: The reinforcing material is glass fiber cloth.
6. The prepreg according to claim 5, characterized in that: The fiberglass cloth is positioned at the middle of the thickness direction of the fully cured PTFE layer.
7. A multilayer circuit board, characterized in that, The invention comprises a plurality of stacked core boards and a prepreg as described in any one of claims 1-6, wherein an adhesive material layer is provided between each pair of adjacent core boards, at least one of the adhesive material layers is the prepreg, and the two prepreg layers of the same prepreg are respectively bonded to the two adjacent core boards.
8. The multilayer circuit board according to claim 7, characterized in that: The core board includes an intermediate insulating layer and two circuit layers, with the two circuit layers respectively disposed on opposite sides of the intermediate insulating layer, and the semi-cured resin layer is bonded to the circuit layers.
9. The multilayer circuit board according to claim 8, characterized in that: The intermediate insulating layer includes one of the following: a polytetrafluoroethylene resin layer, a hydrocarbon resin layer, an epoxy resin layer, a polyimide resin layer, a BT resin layer, or a polyphenylene ether resin layer.
10. The multilayer circuit board according to claim 7, characterized in that: The number of core boards is three or more, and at least one of the adhesive material layers includes a polytetrafluoroethylene resin layer, a hydrocarbon resin layer, an epoxy resin layer, a polyimide resin layer, a BT resin layer, or a polyphenylene ether resin layer.