Immersed mainboard, forming method and power supply module

Abstract

The invention provides an immersed mainboard, a forming method and a power module, the immersed mainboard comprises at least one power module and a mainboard main body, and the at least one power module is arranged on the mainboard main body; the power supply module comprises at least one surface-mounted element; the carrier plate is provided with a first surface and a second surface which are opposite to each other, and the surface-mounted element is arranged on the first surface and / or the second surface; the insulating layer is at least partially arranged on the pin of the surface-mounted element and / or the surface of a connecting welding spot between the pin and the carrier plate; the mainboard body is opposite to the second surface of the carrier plate; the insulating layer is formed in a chemical vapor deposition mode; a gap is formed between the surface-mounted element and the carrier plate, the gap is not completely filled with the insulating layer, and the insulating layer is at least partially arranged on the surface of the space where the gap is located. The insulating layer is formed in a chemical vapor deposition mode, the problem that the insulating layer cannot be covered by a shadow area caused by a spraying mode is avoided, and meanwhile the problem that the connecting terminal is polluted caused by an immersion mode is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of power supply modules, and in particular to the technical field of insulation layers of power supply modules. Background Art

[0002] With the increasing demand for artificial intelligence and data processing, the computing power of various boards is constantly improving, and the power consumption of computing chips is also increasing year by year. At the same time, since these computing units have extremely high size restrictions, they put forward higher and higher requirements on the floor space and heat dissipation of energy processing units.

[0003] In the prior art, 3D stacking has become a trend in order to reduce the footprint of energy processing units. However, 3D stacking is exposed to the environment, and pollutants such as dust, conductive particles, and liquids in the environment can easily lead to the risk of short circuits between metal electrodes of 3D stacked devices in space.

[0004] In addition, in order to improve heat dissipation performance, immersion cooling (single-phase immersion cooling and dual-phase immersion cooling) has become the main cooling method. In immersion cooling, it is easier for some conductive particles to be mixed in the liquid, such as solder balls from the surface of PCBA components. These conductive particles may bridge between adjacent electrodes along with the flow of liquid, resulting in some functional failures and even some secondary disasters, causing the power module and computing chip to fail or even burn out.

[0005] In order to solve this problem, it is usually necessary to apply conformal coating to the PCBA surface to achieve surface insulation. However, due to the 3D stacking, the commonly used surface insulation methods, such as spraying conformal coating, will have shadow areas. Immersion coating will also have the risk of contaminating various connection terminals. Summary of the invention

[0006] The present invention aims at forming the insulating layer, avoiding the problem that the shadow area caused by the spraying method cannot cover the insulating layer, and at the same time avoiding the problem of contaminating the connecting terminal caused by the immersion method.

[0007] In one aspect, the present invention provides a mainboard for immersion, comprising:

[0008] At least one power module and a main board body, wherein the at least one power module is arranged on the main board body;

[0009] The power module comprises:

[0010] At least one surface mount component;

[0011] A carrier board, the carrier board having a first surface and a second surface opposite to each other, the surface mount component being arranged on the first surface and / or the second surface;

[0012] An insulating layer, wherein the insulating layer is at least partially disposed on the surface of the pins of the surface-mounted component and / or the connection solder joints between the pins and the carrier board;

[0013] Wherein, the main board body faces the second surface of the carrier board; the insulating layer is formed by chemical vapor deposition; a gap is provided between the surface-mounted component and the carrier board, and the gap is not completely filled by the insulating layer, and the insulating layer is also at least partially disposed on the surface of the space where the gap is located.

[0014] Optionally, the average thickness of the insulating layer is less than 10 um.

[0015] Optionally, the elongation rate of the insulating layer is greater than 20%.

[0016] Optionally, the power supply module further includes a connecting member, and the connecting member is disposed on the second surface.

[0017] Optionally, the power supply module further includes an adapter board, and the adapter board faces the second surface of the carrier board.

[0018] Optionally, both ends of the connecting member are respectively connected to the carrier board and the adapter board.

[0019] Optionally, the power supply module further includes a magnetic component, and the pins of the magnetic component are respectively connected to the adapter board and the carrier board.

[0020] Optionally, the material of the insulating layer includes parylene.

[0021] Optionally, the melting point of the material of the insulating layer is greater than 260 °C.

[0022] Optionally, micro-protrusions are provided on the surface of the insulating layer.

[0023] Optionally, the micro-protrusions are formed by adjusting the process conditions of the chemical vapor deposition.

[0024] Optionally, the main board body includes opposite third and fourth surfaces, and the third surface faces the second surface of the carrier board.

[0025] Optionally, the main board further includes a computing power chip, the computing power chip is disposed on the third surface of the main board body, and at least one of the power modules is disposed on the fourth surface of the main board body.

[0026] Optionally, the main board further includes a connector, and the connector is disposed on the fourth surface of the main board body.

[0027] Optionally, the main board further includes a support heat dissipation component, the support heat dissipation component is in a "mouth" shape, and is disposed on the third surface of the main board body.

[0028] The present invention also provides a method for forming the above-mentioned mainboard, comprising the steps of:

[0029] S1, performing a chemical vapor deposition process on the power module to form the insulating layer;

[0030] S2, mounting the processed power module on the mainboard body.

[0031] The present invention also provides a method for forming the above-mentioned mainboard, comprising the steps of:

[0032] S1, mounting at least one power module on a mainboard body to form a mainboard;

[0033] S2. Performing a chemical vapor deposition process on the mainboard to form the insulating layer.

[0034] The present invention also provides a power supply module, comprising:

[0035] At least one surface mount component;

[0036] At least two carriers, the carriers are stacked vertically, the carriers have a first surface and a second surface opposite to each other, and the surface mount component is at least disposed between the two carriers;

[0037] An insulating layer, the insulating layer being at least partially disposed on the surface of the pins of the surface mount component and / or the connection solder joints between the pins and the carrier board;

[0038] Wherein, the insulating layer is formed by chemical vapor deposition; a gap is set between the surface-mount component and the carrier, the gap is not completely filled by the insulating layer, and the insulating layer is also at least partially set on the surface of the space where the gap is located.

[0039] Compared with the prior art, the present invention has the following advantages:

[0040] The power module provided by the present invention can effectively prevent the risk of short circuit between electrodes caused by pollutants such as dust, conductive particles, and liquids in the environment; in addition, the insulating layer of the mainboard of the present invention is formed by chemical vapor deposition, which avoids the problem of the shadow area being unable to cover the insulating layer caused by the spraying method, and also avoids the problem of contaminating the connection terminals caused by the immersion method. At the same time, the insulating layer is extremely thin, has good heat dissipation, and will not completely fill the gap. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0042] Figure 1 It is a partial schematic diagram of a power module;

[0043] Figure 2-4 is an example of a power module;

[0044] Figure 5 A top view of the main board;

[0045] Figure 6 This is a bottom view of the main board;

[0046] Figure 7 A schematic diagram of the mainboard and supporting heat dissipation components;

[0047] Figure 8 A bottom view of another embodiment of the mainboard. DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] Figure 1 Figure 1 is a partial schematic diagram of the power module. Figure 1 As shown, the power module 100 includes: at least one surface mount component 103, an insulating layer 109 and a carrier 101; the carrier 101 has a first surface and a second surface relative to each other, and the surface mount component 103 is arranged on the first surface and / or the second surface; the insulating layer 109 is at least partially arranged on the pin 105 of the surface mount component and / or the surface of the connecting solder joint 107 between the pin 105 and the carrier 101; the above-mentioned second surface is the surface facing the main board body 200 (mentioned below), and the first surface and the second surface in the present invention are only used to express relative positions.

[0050] The insulating layer 109 is formed by chemical vapor deposition (CVD). The surface mount component 103 is disposed on the carrier 101 through its pins 105, and then the surface mount component 103 is soldered to the carrier 101 by reflow soldering. Figure 1As shown, the insulating layer is disposed on the entire surface of the surface mount component 103 , the entire surface of the pin 105 of the surface mount component 103 , the entire surface of the connection solder joint 107 between the pin 105 and the carrier 101 , and the first and second surfaces of the carrier 101 .

[0051] Preferably, the insulating layer 109 is disposed at least on the surface of the pins 105 of the surface mount component and the connection solder joints 107 between the pins 105 and the carrier 101 .

[0052] Optionally, the insulating layer 109 includes insulating layers 109a, 109b, 109c, and 109d disposed on surfaces at different positions. The insulating layer 109a of the present invention can not only be disposed on the outer surfaces of the surface mount component 103 and the connection solder joint 107, but the insulating layer 109b of the present invention can also be disposed on the inner surface of the connection solder joint 107, the insulating layer 109c can also be disposed on the inner surface of the surface mount component 103, and the insulating layer 109d can also be disposed on the inner surface of the carrier 101 between the surface mount components. The insulating layer 109 formed by chemical vapor deposition in the present invention can be uniformly disposed on the surface of each component.

[0053] Preferably, the average thickness of the insulating layer is less than 10um. The elongation of the insulating layer is greater than 20%. A gap 102 is set between the surface mount component 103 and the carrier 101, and the gap 102 is not completely filled by the insulating layer. The thickness is less than 10um, which is very thin, not only can achieve insulation protection, but also is conducive to improving heat dissipation, and will not completely fill the gap 102, so it is conducive to better absorbing the expansion and deformation of the solder joints during the reflow soldering of the components, and preventing the adjacent pins from causing the interface peeling due to the volume expansion of the solder and causing solder bridging. At the same time, the method of forming the insulating layer in the prior art cannot form such a thin insulating layer. Specifically, the surface mount component 103 is a component arranged on the second surface facing the main board body 200. The extremely thin coating is conducive to rework and can be quickly removed by plasma treatment, laser ablation, mechanical uncovering, etc., and the time consumption can be controlled within a few minutes. Compared with the traditional immersion removal of the three-proof paint, which often takes more than twenty hours and consumes a large amount of solvent, it can greatly reduce the cost and time consumption of the product repair and avoid environmental pollution.

[0054] Optionally, the insulating layer 109 is at least partially disposed on the surface of the space where the gap is located. Figure 1 Only the case where the insulating layer completely covers the surface of the space where the gap 102 is located is shown. For example, the insulating layer only covers the inner surface of the surface mount component 103 and the inner surface of the connection pad 107. Figure 2 An example of a power module 100 is shown. Figure 1As shown, the power module 100 also includes a connector 110, which is arranged on the second surface of the carrier 101 (i.e., the lower surface in the figure) for realizing the electrical connection of at least one surface-mount component 103. In this example, the surface-mount component 103 is arranged on the first surface (i.e., the upper surface in the figure) and the second surface (i.e., the lower surface in the figure) of the carrier 101. In this example, due to the use of the insulating layer formed by chemical vapor deposition, the risk of short circuit between electrodes caused by pollutants such as dust, conductive particles, and liquids in the environment can be effectively prevented. In addition, there is a shadow area between the carrier 101 and the main board body 200, so the surface-mount component 103 arranged between the carrier 101 and the main board body 200 cannot be well protected. When spraying the three-proof paint, due to the existence of the shadow area, the spraying effect of the three-proof paint is not good. When immersion coating is used, there is a risk of contaminating various connection terminals. However, the insulating layer formed by chemical vapor deposition can solve the above problems well.

[0055] In other examples, the power module 100 includes at least two carriers 101 , the carriers 101 are vertically stacked, and the surface mount component 103 is at least disposed between the carriers 101 . Figure 3-4 Other examples of power modules 100 are shown, such as Figure 3-4 As shown, the number of carriers 101 of the power module 100 is two. Optionally, the first surface (exemplarily representing the upper surface) and the second surface (exemplarily representing the lower surface) of the upper carrier 101 are both provided with the surface-mount component 103, and the first surface (exemplarily representing the upper surface) of the lower carrier 101 is provided with the surface-mount component 103, and the height spacing between the surface-mount component 103 on the lower surface of the upper carrier and the surface-mount component 103 on the upper surface of the lower carrier is less than or equal to 0.5mm, further optionally, the spacing is less than or equal to 0.3mm, and further preferably, the spacing is less than or equal to 0.1mm. Furthermore, the surface of the surface-mount component 103 provided on the second surface (exemplarily representing the lower surface) of the upper carrier 101 and the surface-mount component 103 on the upper surface of the lower carrier are both provided with metal electrodes, and the projections of the metal electrodes in the vertical direction at least partially overlap, and the spacing between the exposed metal electrodes is less than or equal to 0.5mm, further optionally, the spacing is less than or equal to 0.3mm, and further preferably, the spacing is less than or equal to 0.1mm. In this example, since the insulating layer is formed by chemical vapor deposition, the risk of short circuit between electrodes caused by pollutants such as dust, conductive particles, liquids, etc. in the environment can be effectively prevented. In addition, although there is a shadow area between the surface-mounted components of the upper carrier 101 and the lower carrier, since the insulating layer is formed by chemical vapor deposition, the surface-mounted components 103 can also be well protected by the insulating layer to prevent short circuit or pollution.

[0056] Optional, such as Figure 3-4 As shown, the second surface of the carrier 101 below (exemplarily representing the lower surface), the pads arranged on the surface are used for external connection. In order to avoid the pads being covered by the insulating layer during the chemical vapor deposition process, they are protected by means of film or the like. In order to enhance the protection effect, at least the outermost pads are in the form of green oil definition (solder mask defined pad). Furthermore, at least part of the pads in the interior can be in the form of non-solder mask defined pad, so as to facilitate sufficient exhaust during the welding process of external connection and prevent defects such as tin beads and voids.

[0057] Optionally, two ends of the connecting member 110 are respectively connected to the upper carrier board 101 and the lower carrier board 101 .

[0058] Optionally, the power module 100 further includes a magnetic element 120, and pins of the magnetic element 120 are respectively connected to the upper carrier 101 and the lower carrier 101. The magnetic element 120 is a magnetic core.

[0059] Figure 5-8 A schematic diagram of a motherboard for immersion is shown. Figure 5-8 As shown, the immersion motherboard includes: at least one power module 100 and a motherboard body 200; at least one power module 100 is disposed on the motherboard body 200, and the motherboard body 200 is opposite to the second surface of the carrier board 101. Figure 1-4 Any power module shown.

[0060] A shadow area is also formed between the carrier board 101 of the power module 100 and the main board body 200 . Therefore, the spray coating method in the prior art cannot cover the above shadow area with an insulating layer. The insulating layer of the present invention can solve this problem.

[0061] Optionally, at least two carriers in the power module 100 are stacked vertically and arranged on the main board body 200. Since a shadow area is also formed between the carriers 101 of the stacked power module 100, in this case, the spraying method in the prior art cannot cover the insulating layer in the above-mentioned shadow area, but the insulating layer of the present invention can solve this problem.

[0062] The main board body 200 includes a third surface 203 and a fourth surface 204 that are opposite to each other, and the third surface 203 is opposite to the second surface of the carrier board 101. The main board body 200 includes a first side, a second side, a third side and a fourth side that are sequentially connected, and the power module 100 includes a first front-stage power module 100a, a first rear-stage power module 100b, a second front-stage power module 100c and a second rear-stage power module 100d, wherein the first front-stage power module 100a is arranged close to the first side, the first rear-stage power module 100b is arranged close to the second side, the second front-stage power module 100c is arranged close to the third side, and the second rear-stage power module 100d is arranged close to the fourth side. The power module 100 also includes a computing power chip module 205, and the computing power chip module 205 is arranged on the third surface 203 of the main board body 200, specifically, in the middle part of the third surface. Figure 6 As shown, the mainboard further includes a connector 207, which is disposed on the fourth surface 204 of the mainboard body, and the connector 207 is an external connector of the computing chip module 205. The mainboard further includes a support heat dissipation component 209 and a support component 206, the support heat dissipation component 209 is in the shape of a "mouth", and is disposed on the third surface 203 of the mainboard body; the support component 206 is a frame structure, which is disposed on the fourth surface 204 of the mainboard body, and the fourth surface 204 of the mainboard body can also be provided with the power module 100e, the frame structure of the support component 206 is in the shape of a "eye", and the power module 100e and the connector 207 are respectively disposed at the opening of the frame structure.

[0063] Since the connector 207 can be protected by, for example, a film when the chemical vapor deposition insulating layer is formed, the connector 207 will not be contaminated. However, the immersion coating in the prior art, even if the film is applied to the surface of the connector, still has the risk of contaminating the connection terminal due to the immersion method; in addition, the power module and the connector are arranged on the same surface, and the traditional immersion coating method of conformal coating cannot achieve this arrangement.

[0064] The present invention also provides a method for forming the mainboard, comprising the steps of:

[0065] Provide at least one power module and at least one mainboard body; the power module is Figure 1-4 In any power module 100 shown in FIG. 1 , the main board body is Figure 5-8 Any motherboard body 200 shown in .

[0066] S1, performing a chemical vapor deposition process on the power module 100 to form the insulating layer 109;

[0067] S2, mounting the processed power module 100 on the mainboard body 200.

[0068] or,

[0069] S1, mounting at least one power module 100 on a mainboard body 200 to form a mainboard;

[0070] S2, performing a chemical vapor deposition process on the mainboard to form the insulating layer 109.

[0071] The above steps also include: performing a protection step on the connector 207, specifically, applying a film on the surface of the connector 207; the protection step is performed before the chemical vapor deposition process.

[0072] The above steps also include: removing the insulating layer on the surface of the unprotected area. Specifically, the insulating layer on the surface of the unprotected area is removed by laser ablation. The unprotected area is an area that does not require insulation protection, such as the surface of the heating chip of the power module. This removal step is performed after step S2, thereby further increasing the heat dissipation effect.

[0073] In the above steps, before the chemical vapor deposition process is performed, a pre-cleaning step is also included, that is, the surface of the power module 100 or the motherboard equipped with the power module is cleaned to remove the residual flux, tin beads, dust, etc., so as to prevent the insulation layer formed by CVD from having insufficient bonding strength with the substrate, causing interface peeling during reflow, and causing tin creeping short circuit between opposite electrodes. Furthermore, a plasma surface treatment step is added after the cleaning process to further improve the interface bonding strength.

[0074] The material of the insulating layer includes polyparaxylene, and the specific models are at least one of type C, type D, type E, type F, and type N. Polyparaxylene has excellent insulation performance and a stable production process. The insulating layer grows layer by layer with molecular thickness, so it can be used to process safety reinforced insulation with an extremely thin thickness, such as less than 50um. In addition to greatly reducing the surface creepage distance required for safety insulation, due to the extremely thin thickness, the conductive thermal resistance when the module is installed on the radiator can be reduced. In addition to high insulation performance, polyparaxylene material also has excellent density, which can further enhance the weather resistance of the product, such as moisture resistance, corrosion resistance, etc. At the same time, the dielectric constant of polyparaxylene material is relatively low, usually less than 4 and close to the dielectric constant of immersion coolant, which can effectively avoid local electric field distortion caused by material mutation. In addition, the melting point of the material of the insulating layer is greater than 260°C. In particular, in the first method, since the melting point is greater than 260°C, the temperature of the reflow soldering does not affect the insulating layer. Preferably, micro-protrusions are arranged on the surface of the insulating layer, and the micro-protrusions are formed by adjusting the process conditions of the chemical vapor deposition. The micro-protrusions can increase the surface area, which is beneficial to heat dissipation.

[0075] The "equal" or "same" or "equal" disclosed in the present invention must take into account the parameter distribution of the project, and the error distribution is within ±30%; the definition of "parallel" of two line segments or two straight lines is that the angle between the two line segments or two straight lines is less than or equal to 45 degrees; the definition of "perpendicular" of two line segments or two straight lines is that the angle between the two line segments or two straight lines is within the range of [60, 120] degrees; the definition of "phase mismatch" also needs to take into account the parameter distribution of the project, and the error distribution of the degree of mismatch is within ±30%. In addition, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. Without more constraints, an element defined by the phrase "comprising a..." does not exclude the existence of other identical elements in the process, method, article or apparatus comprising the element.

[0076] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0077] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A motherboard for immersion, characterized in that: Comprising: At least one power supply module and a main board body, the at least one power supply module being disposed on the main board body; The power supply module includes: At least one surface-mounted component; A carrier board having opposite first and second surfaces, the surface-mounted component being disposed on the first surface and / or the second surface; An insulating layer at least partially disposed on the surface of the pins of the surface-mounted component and / or the connection solder joints between the pins and the carrier board; Wherein, the main board body faces the second surface of the carrier board; the insulating layer is formed by chemical vapor deposition; a gap is provided between the surface-mounted component and the carrier board, the gap is not completely filled by the insulating layer, and the insulating layer is also at least partially disposed on the surface of the space where the gap is located.

2. The mainboard according to claim 1, wherein: The average thickness of the insulating layer is less than 10 um.

3. The mainboard according to claim 1, characterized in that: The elongation rate of the insulating layer is greater than 20%.

4. The mainboard according to claim 1, characterized in that: The power supply module further includes a connecting member disposed on the second surface.

5. The mainboard according to claim 4, characterized in that: The power supply module further includes an adapter board opposite to the second surface of the carrier board.

6. The mainboard according to claim 5, characterized in that: Both ends of the connecting member are respectively connected to the carrier board and the adapter board.

7. The mainboard according to claim 6, characterized in that: The power supply module further includes a magnetic component, and the pins of the magnetic component are respectively connected to the adapter board and the carrier board.

8. The mainboard according to claim 1, wherein: The material of the insulating layer includes parylene.

9. The mainboard according to claim 1, wherein: The melting point of the material of the insulating layer is greater than 260 °C.

10. The mainboard according to claim 1, wherein: Micro-protrusions are provided on the surface of the insulating layer.

11. The mainboard according to claim 10, characterized in that: The micro-protrusions are formed by adjusting the process conditions of the chemical vapor deposition.

12. The mainboard according to claim 1, wherein: The main board body includes opposite third and fourth surfaces, and the third surface faces the second surface of the carrier board.

13. The mainboard according to claim 12, characterized in that: The main board further includes a computing power chip disposed on the third surface of the main board body, and at least one of the power modules is disposed on the fourth surface of the main board body.

14. The mainboard according to claim 13, wherein: The main board further includes a connector disposed on the fourth surface of the main board body.

15. The mainboard according to claim 13, characterized in that: The main board further includes a support heat dissipation assembly in a "mouth" shape disposed on the third surface of the main board body.

16. A method for forming a mainboard according to any one of claims 1 to 13, characterized in that: Including steps: S1. Perform a chemical vapor deposition process on the power supply module to form the insulating layer; S2. Mount the processed power supply module on the main board body.

17. A method for forming a mainboard according to any one of claims 1 to 13, characterized in that: Including steps: S1. Mount at least one power supply module on the main board body to form a main board; S2. Perform a chemical vapor deposition process on the main board to form the insulating layer.

18. A power module, characterized in that: Comprising: At least one surface-mounted component; At least two carrier boards stacked vertically between the carrier boards, the carrier boards having opposite first and second surfaces, and the surface-mounted component being disposed at least between the two carrier boards; An insulating layer at least partially disposed on the surface of the pins of the surface-mounted component and / or the connection solder joints between the pins and the carrier boards; Wherein, the insulating layer is formed by chemical vapor deposition; a gap is provided between the surface-mounted component and the carrier board, the gap is not completely filled by the insulating layer, and the insulating layer is also at least partially disposed on the surface of the space where the gap is located.

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