Circuit board, circuit structure and server

Abstract

The embodiment of the utility model relates to the technical field of impedance adjustment, in particular to a circuit board, a circuit structure and a server. According to the circuit board provided by the embodiment of the invention, a layer of insulating material is added between the conducting layer on the outermost layer of the circuit board and the external environment medium in the pressing process of the circuit board generation process flow, so that the distance between the conducting layer and the external environment medium is increased; the distance between the outermost conducting layer of the circuit board and the air medium or the cooling liquid medium is increased, the coupling degree between the external environment medium and the conducting layer of the circuit board is reduced, and the influence on the impedance of wiring on the surface layer of the circuit board due to the change of the dielectric constant of the external medium is avoided.

Description

Technical Field

[0001] The embodiments of the utility model relate to the technical field of impedance adjustment, and in particular to a circuit board, a circuit structure and a server. Background Art

[0002] With the development of science and technology, server computing power is getting bigger and bigger, and the heat generation power of the whole machine is also increasing. Air cooling is gradually unable to meet the cooling needs of fully loaded servers. Liquid cooling has advantages such as high heat exchange efficiency. Many server manufacturers have begun to study liquid cooling.

[0003] After purchasing a server, consumers will place the server in different cooling environments according to their personal preferences, for example, placing it in an air-cooled environment or a liquid-cooled environment with different coolant media.

[0004] In different cooling environments, the impedance of the signal transmitted on the printed circuit board (PCB) in the server changes to varying degrees, causing the transmitted signal to be reflected. This prevents the signal from being fully and effectively transmitted on the PCB, seriously reducing the communication quality of the server.

[0005] Therefore, when signals on a PCB are transmitted in different cooling environments, how to keep the impedance of the transmitted signals as consistent as possible has become a technical problem that needs to be solved urgently. Utility Model Content

[0006] In view of the above problems, the embodiments of the present invention provide a circuit board, a circuit structure and a server to solve the above technical problems existing in the prior art.

[0007] In some embodiments, a circuit board is provided, comprising: a substrate;

[0008] A first conductive layer is provided on at least one surface of the substrate, and a first insulating layer is provided on a surface of the first conductive layer away from the substrate;

[0009] A solder resist layer is provided on a surface of the first insulating layer away from the first conductive layer.

[0010] Preferably, a plurality of second insulating layers and a plurality of second conductive layers are alternately arranged between the first conductive layer and the substrate.

[0011] Preferably, the thickness of the first insulating layer is 8-15 mil.

[0012] Preferably, the thickness of the first insulating layer is greater than or equal to the thickness of the second insulating layer.

[0013] Preferably, a third insulating layer is provided on the side of the substrate;

[0014] The third insulating layer is used to cover the side surfaces formed between the solder resist layers on both sides of the substrate.

[0015] Preferably, the thickness of the third insulating layer is 8-12 mil.

[0016] Preferably, the second insulating layer is provided with a conductive hole, and the conductive hole is used to electrically connect adjacent first conductive layers and second conductive layers, or to electrically connect adjacent second conductive layers.

[0017] Preferably, the thickness of the solder resist layer is 0.5 mil.

[0018] In some other embodiments, a circuit structure is further proposed, which includes an electronic component and any one of the circuit boards proposed in the above embodiments, wherein the electronic component is arranged on the circuit board.

[0019] In some other embodiments, a server is further proposed. The server includes the circuit structure and the heat dissipation system proposed in the above embodiments. The heat dissipation system is used to dissipate heat from the circuit structure.

[0020] The circuit board proposed in the embodiment of the present application increases the distance between the conductive layer and the external environment medium by adding a layer of insulating material between the outermost conductive layer of the circuit board and the external environment medium during the pressing process of the circuit board production process, that is, increases the distance between the outermost conductive layer of the circuit board and the air medium or the coolant medium, reduces the degree of coupling between the external environment medium and the conductive layer of the circuit board, and avoids the influence of the impedance of the surface wiring of the circuit board due to the change of the dielectric constant of the external medium.

[0021] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present invention. The same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0023] Figure 1 Shows a schematic diagram of the existing circuit board structure;

[0024] Figure 2 A schematic diagram of the circuit board structure proposed in an embodiment of the present application is shown;

[0025] Figure 3 A schematic diagram of the circuit board structure proposed in another embodiment of the present application is shown.

[0026] Reference numerals:

[0027] 100, circuit board; 110, substrate; 120, first conductive layer; 130, first insulating layer; 140, solder resist layer; 150, second insulating layer; 160, second conductive layer; 170, third insulating layer; 180, conductive via. DETAILED DESCRIPTION

[0028] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0030] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0031] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0032] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists, A and B exist at the same time, and B exists. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0033] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0034] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0035] In the description of the embodiments of the present application, unless otherwise expressly specified or limited, technical terms such as "installed," "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; internal connections between two components or interactions between two components. Those skilled in the art can understand the specific meanings of the above terms in the embodiments of the present application based on specific circumstances.

[0036] The difference in cooling media between liquid cooling and air cooling can affect PCB transmission characteristics. For air cooling, the dielectric constant of air is approximately 1.0006. Current coolants are generally classified as oil-based or fluorine-based, with dielectric constants generally ranging from 1.5 to 3. This change in dielectric constant significantly impacts the high-speed signal integrity of the PCB. Since there are currently no servers specifically designed for liquid cooling, most servers are converted from air-cooled environments to liquid-cooled servers. This change in dielectric constant significantly affects the impedance of the PCB's surface traces, causing signal reflections and further affecting the signal eye diagram, increasing the system's bit error rate (BER) and reducing system performance.

[0037] The applicant has found in research that when a circuit board is placed in different cooling environments, the change in impedance at a certain point on its signal transmission line is mainly caused by a change in the capacitance formed by the capacitance relationship between the point and other structures on the circuit board.

[0038] Figure 1 Schematic diagram of the structure of each stacked layer on the circuit board provided by the embodiment of the present application is shown. Figure 1As shown, the circuit board 100 is a multi-layer board, including a substrate 110, a second conductive layer 160 is provided on one side or both sides of the substrate, a first insulating layer 130 is provided on one side of the second conductive layer 160, a first conductive layer 120 is provided on the first insulating layer 130, a solder resist layer 140 is coated on the first conductive layer 120, a first insulating layer 130 is provided between the first conductive layer 120 and the second conductive layer 160, the first insulating layer 130 is provided between the first conductive layer 120 and the second conductive layer 160, the first insulating layer 130 is used to isolate different conductive layers from each other to avoid short circuits, and transmission lines are etched on the conductive layers for transmitting signals.

[0039] In the current circuit board stackup, the solder mask layer is directly outside the conductive layer. The thickness of this layer is small, and the surface traces are easily affected by external media.

[0040] According to the definition of impedance Z0:

[0041]

[0042] It can be seen that changes in capacitance C at a point on a transmission line will cause changes in impedance Z0 at that point. Here, L is the inductance value at that point on the transmission line, and C is the capacitance value at that point. The characteristic impedance of a point on a transmission line on a circuit board is related to the inductance and capacitance values ​​at that point. When the external medium changes from air to coolant, the dielectric constant of air is approximately 1, while the dielectric constant of current mainstream coolants is approximately 2 to 3. The dielectric constant is also called the permittivity. According to Formula 1, this will change the characteristic impedance Z0 of the transmission line.

[0043] When the external environment medium changes, the capacitance C in the parallel plate is calculated by the formula:

[0044] C=ε*A / h (Formula 2)

[0045] It can be seen that changes in the external environment medium will cause changes in the capacitance C on the parallel plates, thereby affecting the change in the characteristic impedance of the transmission line. Here, ε is the dielectric constant, A is the relative area of ​​the parallel plates, and h is the distance between the parallel plates. Therefore, from the above analysis, it can be concluded that when the dielectric constant ε of the external environment medium in which the transmission line is located changes, it will cause the capacitance between the transmission line and the reference plane to change, and thus cause the impedance of the transmission line to change. From Formula 2, it can be seen that the greater the distance h, the smaller the capacitance C, indicating that the degree of coupling is smaller. In order to prevent the change in the dielectric constant of the external medium from affecting the characteristic impedance of the transmission line, it is necessary to increase the distance between the external environment medium and the transmission conductor.

[0046] Based on this, the applicant proposes to increase the distance between the conductive layer and the external environment medium by adding a layer of insulating material between the outermost conductive layer of the circuit board and the external environment medium in the pressing process of the circuit board production process, that is, to increase the distance between the outermost conductive layer of the circuit board and the air medium or the coolant medium, reduce the degree of coupling between the external environment medium and the conductive layer of the circuit board, and avoid the impact of changes in the dielectric constant of the external medium on the impedance of the surface wiring of the circuit board.

[0047] like Figure 2 As shown, a circuit board proposed in an embodiment of the present application includes a substrate 110, a first conductive layer 120 is provided on at least one side surface of the substrate 110, a first insulating layer 130 is provided on the side surface of the first conductive layer 120 away from the substrate 110; and a solder resist layer 140 is provided on the side surface of the first insulating layer 130 away from the first conductive layer 120.

[0048] The circuit board can be a single-sided board or a multi-sided board. When the circuit board is a single-sided board, the first conductive layer 120 can be provided on only one side of the substrate 110; when the circuit board is a multi-sided board or a multi-layer board, the first conductive layer 120 can be provided on both sides of the substrate 110. The substrate 110 can be made of a variety of materials, such as PTFE (polytetrafluoroethylene) or Teflon, polyimide (PI), ceramic PCB, and metal substrate, etc. Different materials can be used for different scenarios and needs, which is not limited in the embodiments of this application.

[0049] The first conductive layer 120 is a metal conductive layer, typically made of copper foil, aluminum foil, or other materials, and is used to electrically connect to electronic components. Through an etching process, different patterns of traces are formed on the circuit board for signal transmission. The first conductive layer 120 can be laminated to the substrate 110 through a thermal lamination process.

[0050] In order to increase the distance between the first conductive layer 120 and the external environmental medium and reduce the interference of the external environmental medium on the first conductive layer 120, the embodiment of the present application continues to set a first insulating layer 130 outside the first conductive layer 120 through a hot pressing process. The first insulating layer 130 is mainly used to reduce the interference of the external environmental medium on the first conductive layer 120. It can be made of materials with excellent heat resistance, mechanical properties and electrical insulation, such as epoxy resin (Epoxy Resin), phenolic resin (Phenolic Resin) and polyimide (Polyimide, PI).

[0051] To improve the isolation effect of the first insulating layer 130 from the external environment, the thickness of the first insulating layer can be set between 8 mils and 15 mils. The selection of the thickness of the first insulating layer should take into account the isolation effect and the overall thickness requirements of the circuit board. From the perspective of isolation effect from the external environment, a thickness of 15 mils can achieve the best isolation effect. To reduce the overall thickness of the circuit board, the first insulating layer can also be 8 mils thick.

[0052] Continue to refer Figure 2 , a solder resist layer 140 is provided on the surface of one side of the first insulating layer 130 away from the first conductive layer 120. The solder resist layer 140 is usually made of special ink materials, which have good heat resistance, chemical resistance and wear resistance after curing. The thickness, color and material of the solder resist layer can be selected according to the specific application requirements. Common solder resist materials include epoxy resin, acrylic resin and polyurethane, etc. In the embodiment of the present application, since a first insulating layer 130 is provided outside the first conductive layer 120, in order to reduce the overall thickness of the circuit board, the thickness of the solder resist layer 140 can be appropriately reduced, preferably set to 0.5 mil. By reducing the thickness of the solder resist layer 140, on the one hand, it will not affect the overall performance of the circuit board. On the other hand, while ensuring the isolation effect to the external environmental medium, the overall thickness of the circuit board can be reduced as much as possible.

[0053] From the above, it can be seen that the circuit board proposed in the embodiment of the present application increases the distance between the outermost first conductive layer and the external environment medium by adding an insulating layer on the outside of the first conductive layer of the outermost layer of the circuit board, thereby reducing the change in capacitance on the parallel plate caused by changes in the external environment medium, and further reducing the change in impedance of the transmission line, thereby avoiding the impact of changes in the dielectric constant of the external medium on the impedance of the surface wiring of the circuit board.

[0054] For some circuit boards that use multilayer technology, such as Figure 3 As shown, the circuit board structure includes multiple insulating layers and multiple conductive layers, and multiple second insulating layers 150 and multiple second conductive layers 160 are alternately arranged between the first conductive layer 120 and the substrate 110.

[0055] For a multi-layer board, the first insulating layer 130 only needs to be provided on the outer surface of the outermost conductive layer. Figure 3 In the embodiment, the first insulating layer 130 is arranged on the surface of the outermost conductive layer, the first conductive layer 120, and different conductive layers are isolated by the insulating layer. Figure 3 In the figure, only a four-layer board structure is shown. In practice, it can be a six-layer board or other forms of circuit boards. This is not limited in the embodiments of the present application.

[0056] In order to reduce the thickness of the circuit board as much as possible while ensuring the isolation effect from the external environment medium and the conductive layer, in an embodiment of the present application, the thickness of the first insulating layer 130 is set to be greater than or equal to the thickness of the second insulating layer 150.

[0057] Setting the thickness of the first insulating layer 130 to the maximum can maximize the isolation effect of the first insulating layer 130 on the external environmental medium. Setting the thickness of the second insulating layer 150 to a smaller value can ensure the overall thickness of the circuit board, thereby achieving an overall balance between the isolation effect and the overall thickness of the circuit board.

[0058] After the first insulating layer 130 is provided on the outermost layer of the conductive layer, it can isolate the external environment medium on the surface of the circuit board to the greatest extent. However, the side boundary surface of the circuit board will also contact the external environment medium, and the external environment medium will also penetrate the circuit board through the side of the circuit board, thereby affecting the conductive layer. In order to achieve the best isolation effect, in the embodiment of the present application, Figure 3 As shown, a third insulating layer 170 is provided on the side of the substrate 110 ; the third insulating layer 170 is used to cover the side surface formed between the solder resist layers 140 on both sides of the substrate 110 .

[0059] Depend on Figure 3 It can be seen that the third insulating layer 170 is mainly used to wrap all the sides of the circuit board. The sides of the circuit board are mainly formed by the outermost solder mask layer 140 on both sides of the circuit board, including multiple conductive layers, multiple isolation layers and the sides of the substrate. Therefore, the third insulating layer 170 covers the side surfaces formed between the solder mask layer 140 on both sides of the substrate 110. Among them, the thickness of the third insulating layer 170 is 8-12 mil. The specific thickness can be determined by comprehensively considering the requirements of the circuit board for the specific application scenario. By providing the third insulating layer 170 on multiple sides of the circuit board, the circuit board is fully wrapped, which can better isolate the external environment medium.

[0060] It should be noted that the first insulating layer 130, the second insulating layer 150, and the third insulating layer 170 can be made of the same material or different materials. Since the first insulating layer 130 and the third insulating layer 170 mainly serve to isolate the external environment medium, they can be made of the same material. The second insulating layer 150 mainly serves to insulate and can be made of a different material.

[0061] In a multilayer board, to achieve electrical connection between different conductive layers, in the embodiment of the present application, conductive vias 180 are provided in the second insulating layer 150. These conductive vias 180 are used to electrically connect adjacent first conductive layers 120 and second conductive layers 160, or to electrically connect adjacent second conductive layers 160. Providing conductive vias 180 in the second insulating layer 150 does not affect the isolation of the first insulating layer 130 from the external environment.

[0062] Furthermore, in some embodiments, a circuit structure is provided, which includes electronic components and the circuit board provided in the above embodiments, wherein the electronic components are provided on the circuit board. The structure of the circuit board has been described in detail in the above embodiments and will not be repeated here.

[0063] Furthermore, in some embodiments, a server is proposed. The server includes the circuit structure and a heat dissipation system proposed in the above embodiments. The heat dissipation system is used to dissipate heat from the circuit structure.

[0064] To summarize, the circuit board, circuit structure, and server proposed in the embodiments of the present application increase the distance between the conductive layer and the external environment medium by adding a layer of insulating material between the outermost conductive layer of the circuit board and the external environment medium during the pressing process of the circuit board production process, that is, increasing the distance between the outermost conductive layer of the circuit board and the air medium or the coolant medium, reducing the degree of coupling between the external environment medium and the conductive layer of the circuit board, and avoiding the impact of changes in the dielectric constant of the external medium on the impedance of the surface wiring of the circuit board.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A circuit board, characterized in that: include: substrate; A first conductive layer is provided on at least one surface of the substrate, and a first insulating layer is provided on a surface of the first conductive layer away from the substrate; A solder resist layer is provided on a surface of the first insulating layer away from the first conductive layer.

2. The circuit board according to claim 1, wherein: A plurality of second insulating layers and a plurality of second conductive layers are alternately arranged between the first conductive layer and the substrate.

3. The circuit board according to claim 2, wherein: The thickness of the first insulating layer is 8-15 mil.

4. The circuit board according to claim 3, wherein: The thickness of the first insulating layer is greater than or equal to the thickness of the second insulating layer.

5. The circuit board according to claim 3, wherein: A third insulating layer is provided on the side of the substrate; The third insulating layer is used to cover the side surfaces formed between the solder resist layers on both sides of the substrate.

6. The circuit board according to claim 5, characterized in that The thickness of the third insulating layer is 8-12 mil.

7. The circuit board according to claim 3, wherein: The second insulating layer is provided with a conductive hole, and the conductive hole is used to electrically connect adjacent first conductive layers and second conductive layers, or to electrically connect adjacent second conductive layers.

8. The circuit board according to claim 3, wherein: The thickness of the solder resist layer is 0.5 mil.

9. A circuit structure, characterized in that: The invention comprises an electronic component and a circuit board according to any one of claims 1 to 8, wherein the electronic component is arranged on the circuit board.

10. A server, characterized in that: It comprises the circuit structure as claimed in claim 9 and a heat dissipation system, wherein the heat dissipation system is used to dissipate heat from the circuit structure.

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