A method for preparing a board and a board and its application

Abstract

The present application discloses a method for preparing a board and a board and application thereof, relating to the field of board processing technology, including using reflow soldering to solder a printed circuit board, a tin sheet, and a copper busbar, which can effectively improve the uniformity of solder filling, inhibit gas residue during the flow of molten solder, effectively reduce the void rate of the board, effectively increase the current conduction cross-sectional area, improve VR remote conversion efficiency at a lower cost, and reduce Rpath.

Description

Technical Field

[0001] The present application relates to the technical field of board processing, and in particular to a method for preparing a board, and the board and its application. Background Art

[0002] In the power supply system of a central control unit (CPU), the printed circuit board (PCB) path impedance (Rpath), from the voltage regulator (VR) output inductor to the CPU load, is a key parameter affecting power supply performance. The physical essence of path impedance is the ohmic resistance generated by current flowing through the PCB copper layer. Its value is determined by copper foil thickness, trace length / width, stackup structure, and operating temperature.

[0003] Related technologies primarily rely on PCB stacking and copper thickness upgrades to reduce PCB path impedance, but this approach significantly increases PCB costs. Therefore, improving VR remote conversion efficiency and reducing Rpath without increasing costs are urgent technical challenges that need to be addressed. Summary of the Invention

[0004] The present application provides a board and its preparation method and application to solve the problems in related technologies of improving VR remote conversion efficiency and reducing high Rpath costs.

[0005] The present application provides a method for preparing a board, comprising:

[0006] Performing tin plating on one surface of the copper substrate to obtain a first middle copper busbar including a tin layer;

[0007] Performing an aging treatment on the first intermediate copper busbar to obtain a second intermediate copper busbar including a tin-copper composite layer and a copper layer;

[0008] An insulating layer is provided on the other surface of the copper substrate to form a copper busbar including a tin layer, a tin-copper composite layer, a copper layer and an insulating layer in a stacking direction;

[0009] After the copper busbar and tin sheet are stacked, they are packaged in a hard tray with the tin layer placed close to the tin sheet;

[0010] Using a fitting, the copper busbar and the tin sheet packaged in the hard tray are attached to the surface of the printed circuit board, wherein the tin sheet is placed close to the printed circuit board;

[0011] Performing a reflow soldering to obtain the board;

[0012] Wherein, the thickness of the tin layer is 3-5 μm;

[0013] The thickness of the tin-copper composite layer is 1.5-2 μm;

[0014] The dielectric strength of the insulation layer is ≥200V / μm;

[0015] The thermal conductivity of the insulation layer is 1-1.5 W / m·K;

[0016] The conductivity of the copper layer is ≥58MS / m;

[0017] The yield strength of the copper layer is ≥240MPa.

[0018] In the preparation method of the board card of the present application, a prefabricated tin sheet is used to reflow solder a copper busbar with a special structure on the surface of a printed circuit board to obtain the board card. The prefabricated tin sheet is a solid tin sheet, which can effectively improve the uniformity of solder filling during the welding process, suppress gas residue during the flow of molten solder, effectively reduce the void rate of the board card, effectively increase the current conduction cross-sectional area, improve VR remote conversion efficiency at a lower cost, and reduce Rpath; and the copper busbar with a special structure has excellent electrical conductivity, thermal conductivity and processability, which can not only improve the electrical conductivity of the board card, but also enable the board card to have excellent heat dissipation, electrical isolation and mechanical properties. Therefore, the preparation method of the present invention can obtain a board card with low void rate, excellent heat dissipation, electrical isolation and mechanical properties at an extremely low cost, which is suitable for wide promotion and application.

[0019] The present application provides a board card, which is prepared by the above-mentioned board card preparation method.

[0020] Since the board card of the present application is prepared by the above-mentioned preparation method, the board card of the present application has a low void rate, which can solve the problems of improving VR remote conversion efficiency and reducing high Rpath costs in related technologies. Moreover, the board card of the present invention also has excellent heat dissipation, electrical isolation and mechanical properties, and can be widely used and promoted.

[0021] The present application provides a server including the above-mentioned board.

[0022] The server including the above-mentioned board has high VR remote conversion efficiency and low Rpath, and has excellent stability and service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0024] Figure 1 A schematic diagram of a process for preparing a board provided in an embodiment of the present application;

[0025] Figure 2A schematic diagram of another board manufacturing process provided in an embodiment of the present application;

[0026] Figure 3 A schematic diagram of the structure of a copper busbar from one perspective provided in an embodiment of the present application;

[0027] Figure 4 A schematic diagram of the structure of a copper busbar from another perspective provided in an embodiment of the present application;

[0028] Figure 5 A schematic diagram of the structure of the tin sheet under the first viewing angle provided in an embodiment of the present application;

[0029] Figure 6 A schematic diagram of the structure of the tin sheet under the second viewing angle provided in an embodiment of the present application;

[0030] Figure 7 This is a schematic diagram of the structure of the tin sheet from the third perspective provided in an embodiment of the present application.

[0031] The above drawings include the following reference numerals:

[0032] 1: Printed circuit board;

[0033] 2: tin sheet;

[0034] 3: Copper busbar;

[0035] 4: Soft cushion;

[0036] 5: Fixture;

[0037] 21: solder paste layer;

[0038] 22: tin body layer;

[0039] 23: lateral wall;

[0040] 31: tin layer;

[0041] 32: insulation layer;

[0042] 33: tin-copper composite layer;

[0043] 34: Copper layer. DETAILED DESCRIPTION

[0044] The following will be combined with the accompanying drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0045] It should be noted that, in the description of this application, the terms "comprises," "includes," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. The terms "first," "second," etc., in this application are used to distinguish similar objects, and are not used to describe a particular order or sequence.

[0046] With the upgrade of CPUs, the demand for boards is increasing. However, there are constraints such as difficulty in PCB routing and increased board layer or copper thickness. In view of this, the inventors discovered that optimizing the connection between the copper busbar and the PCB can improve board performance and save costs.

[0047] In order to enable those skilled in the art to better understand the present application, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0048] In this application, void ratio refers to the volume ratio of tiny bubbles (voids) formed within the solder joint after soldering due to factors such as residual gas, solder shrinkage, or contamination. It is usually expressed as a percentage (%). Void ratio = (total void volume / total solder joint volume) × 100%. For example, the void ratio of a board refers to the volume percentage of the board that is occupied by voids.

[0049] Figure 1 A schematic diagram of a process for preparing a board provided in an embodiment of the present application; Figure 2 A schematic diagram of another board manufacturing process provided in an embodiment of the present application; Figure 3 A schematic diagram of the structure of a copper busbar from one perspective provided in an embodiment of the present application; Figure 4 This is a schematic diagram of the structure of the copper busbar from another perspective provided in the embodiment of the present application. Figure 1 、 Figure 2 、 Figure 3 as well as Figure 4 As shown, the first aspect of the present application provides a method for preparing a board, comprising:

[0050] Tinning is performed on one surface of the copper substrate to obtain a first middle copper busbar including a tin layer 31;

[0051] Performing an aging treatment on the first intermediate copper busbar to obtain a second intermediate copper busbar including a tin-copper composite layer 33 and a copper layer 34;

[0052] An insulating layer 32 is provided on the other surface of the copper substrate to form a copper busbar 3 including a tin layer 31, a tin-copper composite layer 33, a copper layer 34 and an insulating layer 32 in the stacking direction;

[0053] After the copper busbar 3 and the tin sheet 2 are stacked, they are packaged in a hard tray, with the tin layer 31 placed close to the tin sheet 2;

[0054] Use a fitting to attach the copper busbar 3 and the tin sheet 2 packaged in the hard tray to the surface of the printed circuit board 1, with the tin sheet 2 being placed close to the printed circuit board 1;

[0055] Perform a reflow soldering to obtain a board;

[0056] Wherein, the thickness of the tin layer 31 is 3-5 μm;

[0057] The thickness of the tin-copper composite layer 33 is 1.5-2 μm;

[0058] The dielectric strength of the insulating layer 32 is ≥ 200 V / μm;

[0059] The thermal conductivity of the insulating layer 32 is 1-1.5 W / m·K;

[0060] The electrical conductivity of the copper layer 34 is ≥58MS / m;

[0061] The yield strength of the copper layer 34 is ≥240 MPa.

[0062] Specifically, a tin plating treatment is performed on one surface of the copper substrate, thereby forming a tin layer 31 on the one surface of the copper substrate, thereby obtaining a first intermediate copper busbar including the tin layer 31; then, the first intermediate copper busbar is subjected to an aging treatment to cause the tin layer 31 and the copper substrate to fuse with each other, thereby forming a tin-copper composite layer 33 including a tin-copper composite phase (e.g., a Cu6Sn5 phase), while the remaining copper substrate forms a copper layer 34, thereby obtaining a second intermediate copper busbar including the tin-copper composite layer 33 and the copper layer 34; an insulating layer 32 is provided on a surface of the second intermediate copper busbar away from the tin layer 31, thereby forming a copper busbar 3 including the tin layer 31, the tin-copper composite layer 33, the copper layer 34, and the insulating layer 32 in the stacking direction;

[0063] The copper busbar 3 and the tin sheet 2 are stacked in the order of the insulating layer 32, the copper layer 34, the tin-copper composite layer 33, the tin layer 31, and the tin sheet 2, and then packaged in a hard tray. The hard tray is then automatically sucked by the placement machine. At the same time, the copper busbar 3 and the tin sheet 2 packaged in the hard tray are attached to the surface of the printed circuit board 1 using a bonding member.

[0064] Then, reflow soldering is performed, during which the solid tin sheet 2 melts into liquid tin. After the liquid tin solidifies, the copper bus 3 is bonded to the printed circuit board 1 to obtain a board.

[0065] This application does not impose any special restrictions on the bonding parts, as long as the copper busbar 3, tin sheet 2 and printed circuit board 1 can be tightly fitted. For example, when the bonding part is a soft pad 4, not only can the copper busbar 3, tin sheet 2 and printed circuit board 1 be tightly fitted, but also the copper busbar 3, tin sheet 2 and printed circuit board 1 can be prevented from breaking.

[0066] In this application, dielectric strength refers to the ability of the insulation layer 32 to withstand the highest electric field strength without breaking. Thermal conductivity refers to the amount of heat transferred through one square meter of area in one second under stable heat transfer conditions, with a temperature difference of one degree (K, °C) between the two surfaces of a one-meter-thick insulation layer 32. The unit is watts per meter·K (W / (m·K), where K can be replaced by °C). Electrical conductivity is the ratio of current intensity to power intensity. Yield strength is the yield limit of a metal material when it yields, that is, the stress at which it resists minimal plastic deformation. For metal materials without significant yielding, the yield limit is defined as the stress that produces 0.2% residual deformation, also known as yield strength. The copper layer 34 in this application has a conductivity of ≥58 MS / m (IACS 98%) and a yield strength of ≥240 MPa. The copper busbar 3 including this copper layer 34 has excellent electrical conductivity and mechanical properties, thereby improving the electrical conductivity and mechanical properties of the board. In order to obtain a copper layer 34 having the above-mentioned conductivity and yield strength, the copper substrate is selected from a copper material whose conductivity and yield strength meet the above-mentioned ranges; the thickness of the tin layer 31 of the present application is 3-5 μm, and the tin layer 31 can be more fully melted with the tin sheet 2 during reflow soldering, thereby improving the efficiency and quality of reflow soldering, and thus improving the conductivity and quality of the board; and the tin-copper composite layer 33 with a thickness of 1.5-2 μm can not only achieve a close combination of the tin layer 31 and the copper layer 34, but also further ensure the mechanical properties of the copper busbar 3, avoiding the copper busbar 3 from breaking due to excessive brittleness during long-term use; the insulating layer 32 that meets the above-mentioned dielectric strength and thermal conductivity has excellent electrical isolation and auxiliary heat dissipation functions, which can improve the electrical isolation and heat dissipation performance of the board.

[0067] In the preparation method of the present application, a tin sheet 2 is used to weld a copper busbar 3 with a special structure to a printed circuit board 1 to prepare a board. The solid tin sheet 2 melts to form liquid tin, which can effectively improve the uniformity of solder filling, inhibit gas residue during the flow of molten solder, effectively reduce the void rate of the board, effectively increase the current conduction cross-sectional area, improve the VR remote conversion efficiency at a lower cost, and reduce Rpath; during the welding process, a bonding piece is used to bond the tin sheet 2 and the copper busbar 3 to the printed circuit board 1, which can improve the welding quality and further reduce the void rate of the board; at the same time, the present application can prepare the board through only one reflow soldering, which is not only simple to operate, but also can greatly reduce the void rate of the board; the copper busbar 3 with a special structure can not only improve the electrical isolation, heat dissipation and mechanical properties of the board, but also can better melt with the solid tin sheet 2, further improve the welding quality, reduce the void rate of the board, and improve the conductivity of the board. In summary, the preparation method of the present application can produce a board with excellent electrical conductivity, heat dissipation, electrical isolation and mechanical properties, and the preparation method is simple to operate, low in cost, and suitable for wide promotion and application.

[0068] In some embodiments, compared with related technologies, the void ratio of the board card obtained by the preparation method of the present application can be reduced from 15-25% to within 4.7%, and the current conduction cross-sectional area can be increased by more than 30%.

[0069] In the present application, a tin plating treatment and an aging treatment can be performed on one surface of the copper substrate first, and then an insulating layer 32 is provided on the other surface of the copper substrate to form the copper busbar 3; or an insulating layer 32 can be provided on one surface of the copper substrate first, and then a tin plating treatment and an aging treatment can be performed on the other surface of the copper substrate.

[0070] The present application does not particularly limit the specific form of implementing reflow soldering. For example, reflow soldering can be performed by at least one of a reflow furnace, an infrared heating lamp, and a hot air gun.

[0071] In this application, a tin sheet 2 and a copper bus 3 can be set on one surface of the printed circuit board 1 to prepare the board by reflow soldering, or a tin sheet 2 and a copper bus 3 can be set on both surfaces of the printed circuit board 1 to prepare the board by reflow soldering.

[0072] When tin sheets 2 and copper busbars 3 are respectively set on the two surfaces of the printed circuit board 1 and reflow soldering is performed to prepare the board, when soldering on the second side, the copper busbar 3 needs to be partially shielded using a jig 5 to prevent the copper busbar 3 from reaching the tin melting temperature.

[0073] In this application, the dimensions of the copper bus 3 and the tin sheet 2 can be selected according to the flow requirements and the PCB layout design.

[0074] For example, the thickness of the tin layer 31 can be any one of 3 μm, 3.4 μm, 3.5 μm, 3.6 μm, 4.5 μm, 5 μm, or any two thereof; the thickness of the tin-copper composite layer 33 can be any one of 1.5 μm, 1.6 μm, 1.8 μm, 2 μm, or any two thereof.

[0075] For example, the dielectric constant of the insulating layer 32 may be any one of 200 V / μm, 250 V / μm, 270 V / μm, 300 V / μm, and 400 V / μm, or any two thereof. The thermal conductivity of the insulating layer 32 may be any one of 1 W / m·K, 1.2 W / m·K, 1.3 W / m·K, 1.4 W / m·K, and 1.5 W / m·K, or any two thereof. Preferably, the thermal conductivity of the insulating layer 32 is 1.2 W / m·K.

[0076] In some embodiments, an insulating material may be sprayed on the other surface of the copper substrate to form an insulating layer 32. The insulating layer 32 may be nano-aluminum oxide modified polyimide.

[0077] For example, the conductivity of copper layer 34 may be in the range of 58 MS / m, 60 MS / m, 63 MS / m, 67 MS / m, 80 MS / m, or 100 MS / m, or any combination thereof. The yield strength of copper layer 34 may be in the range of 240 MPa, 243 MPa, 250 MPa, 270 MPa, or 300 MPa, or any combination thereof. In some embodiments, copper layer 34 may be T2Y2 oxygen-free copper (purity greater than or equal to 99.95%), which exhibits excellent electrical conductivity, thermal conductivity, corrosion resistance, and workability. Compared to conventional C1100 copper (conductivity of 56 MS / m and yield strength of 200 MPa), T2Y2 oxygen-free copper exhibits superior electrical conductivity and mechanical properties.

[0078] In some embodiments of the present application, the tin plating process may be a matte tin deposition process. Compared to conventional bright tin treatment, the matte tin deposition process forms a tin layer 31 with a greater surface roughness, which can increase the interfacial bonding area between the tin layer 31 and the tin sheet 2, improve the solubility between the tin layer 31 and the tin sheet 2, improve the soldering quality, and thus improve the conductivity of the board. For example, the surface roughness Ra of the tin layer 31 formed by the matte tin deposition process is 0.3-0.5 μm, while the surface roughness Ra of the tin layer 31 formed by the bright tin treatment is 0.1 μm.

[0079] For example, the surface roughness of the tin layer 31 may be in the range of any one of 0.3 μm, 0.35 μm, 0.4 μm, 0.43 μm, 0.45 μm, and 0.5 μm, or any two of the ranges.

[0080] In the present application, specific parameters of the aging treatment can be selected to ensure that the tin layer 31 does not change color or accumulate tin, and to form a tin-copper composite layer 33 of a specific composition and specific thickness. In some embodiments of the present application, the aging treatment is performed at a temperature of 240-270° C. and for a time of 40-70 seconds.

[0081] For example, during the aging treatment, the temperature can be any one of 240°C, 250°C, 255°C, and 270°C, or a range consisting of any two of them; the time can be any one of 40s, 45s, 60s, 65s, and 70s, or a range consisting of any two of them.

[0082] In a specific embodiment, during the aging treatment, the temperature is 260° C. and the time is 60 seconds.

[0083] Figure 5 A schematic diagram of the structure of the tin sheet under the first viewing angle provided in an embodiment of the present application; Figure 6 A schematic diagram of the structure of the tin sheet under the second viewing angle provided in an embodiment of the present application; Figure 7 This is a schematic diagram of the structure of the tin sheet under the third viewing angle provided in the embodiment of this application. Figure 5 、 Figure 6 as well as Figure 7 In some embodiments of the present application, the edge of the orthographic projection of the tin sheet 2 on the copper busbar 3 coincides with the edge of the copper busbar 3 and / or is located within the edge of the copper busbar 3 .

[0084] In this application, the orthographic projection refers to the projection formed on the surface of the copper busbar 3 when the incident light illuminates the tin sheet 2 in a direction perpendicular to the copper busbar 3 .

[0085] It can be understood that in this application, the edge of the orthographic projection can completely coincide with the edge of the copper busbar 3; the edge of the orthographic projection can be completely located within the edge of the copper busbar 3; the edge of the orthographic projection can be partially located within the edge of the copper busbar 3 and the other part coincides with the edge of the copper busbar 3.

[0086] When the edge of the orthographic projection completely overlaps with the edge of the copper busbar 3, the size of the tin sheet 2 is the same as the size of the copper busbar 3. When the edge of the orthographic projection is completely within the edge of the copper busbar 3, or when part of the edge of the orthographic projection is within the edge of the copper busbar 3 and the other part overlaps with the edge of the copper busbar 3, the size of the tin sheet 2 is smaller than the size of the copper busbar 3.

[0087] When the size of the tin sheet 2 is smaller than or equal to the size of the copper busbar 3 , the tin sheet 2 is not likely to overflow during welding, which can save the tin sheet 2 and improve the welding quality.

[0088] Furthermore, the distance between the edge of the orthographic projection and the edge of the copper busbar 3 is 0.1-0.2 mm. In this application, the distance between the edge of the orthographic projection and the edge of the copper busbar 3 refers to the vertical distance between the edge of the orthographic projection and the edge of the copper busbar 3 at any position. That is, the size of the tin sheet 2 is smaller than that of the copper busbar 3, and the edge of the tin sheet 2 is indented by 0.1-0.2 mm relative to the edge of the copper busbar 3. This configuration further prevents tin overflow during soldering, conserving tin sheet 2 while improving soldering quality.

[0089] For example, the distance between the edge of the orthographic projection and the edge of the copper busbar 3 may be any one of 0.1 mm, 0.12 mm, 0.13 mm, 0.14 mm, 0.16 mm, 0.19 mm, and 0.2 mm, or a range consisting of any two of these.

[0090] like Figure 5 As shown, in some embodiments of the present invention, the tin sheet 2 includes a stacked tin body layer 22 and a soldering layer 21, and the soldering layer 21 is disposed close to the printed circuit board 1. The soldering layer 21 is used to remove substances on the surface of the printed circuit board 1 and promote the welding of the tin sheet 2 and the printed circuit board 1.

[0091] Furthermore, when the thickness of the tin sheet 2 is 0.15-0.25 mm, the bonding force between the copper bus 3 and the printed circuit board 1 can be improved while saving the tin sheet 2, thereby improving the overall performance of the board.

[0092] For example, the thickness of the tin sheet 2 may be any one of 0.15 mm, 0.16 mm, 0.17 mm, 0.2 mm, 0.22 mm, 0.24 mm, and 0.25 mm, or any two thereof. Specifically, the thickness of the tin sheet 2 may be 0.2 mm.

[0093] Furthermore, when the tin body layer 22 includes, by mass percentage, Sn 96.5%, Ag 3%, and Cu 0.5%, the tin sheet 2 can be more fully melted during the soldering process, thereby improving the uniformity of solder filling and obtaining a board with a low porosity rate.

[0094] In particular, when the void ratio of the tin body layer 22 is less than 5%, a board with a lower void ratio can be obtained, thereby further increasing the current conduction cross-sectional area, improving the VR remote conversion efficiency, and reducing Rpath.

[0095] For example, the void ratio of the tin body layer 22 may be any one of 4%, 3%, 2%, 1%, and 0.5%, or a range consisting of any two of the above.

[0096] Furthermore, when the mass percentage of the soldering layer 21 is 3.5-10% based on the total mass of the tin sheet 2, the tin sheet 2 can be better welded to the printed circuit board 1, thereby obtaining a board with excellent comprehensive performance.

[0097] For example, based on the total mass of the tin sheet 2 , the mass percentage of the soldering layer 21 may be in the range of any one of 3.5%, 4%, 5%, 6%, 7%, 9%, 10%, or any two of these.

[0098] In some embodiments, the mass percentage of solder paste layer 21 can be further selected based on the surface composition of printed circuit board 1 to further facilitate soldering between tin flake 2 and printed circuit board 1 and improve the overall performance of the board. For example, if printed circuit board 1 has an oxide film (OSP) coating on its surface, the mass percentage of solder paste layer 21 in tin flake 2 is 8-10%; if the surface of printed circuit board 1 has been treated with gold, the mass percentage of solder paste layer 21 in tin flake 2 is 3.5-5%.

[0099] It can be understood that the surface of the tin sheet 2 away from the printed circuit board 1 does not include the soldering layer 21 to prevent the soldering layer 21 from clogging the nozzle of the placement machine.

[0100] In some embodiments of the present invention, copper wire is further provided on the side wall 23 of the tin sheet 2 before reflow soldering.

[0101] like Figure 7 As shown, in this perspective, the tin sheet 2 has a side wall 23. Copper wire is arranged on the side wall 23 of the tin sheet 2, so that liquid tin is not easy to escape to the periphery of the copper bus 3 after welding.

[0102] Furthermore, when the diameter of the copper wire is less than or equal to 1 / 2 of the thickness of the tin sheet 2, the continuity of the soldering between the copper bus 3 and the PCB can be improved. Preferably, the diameter of the copper wire is 0.1 mm.

[0103] Furthermore, during a single reflow soldering operation, the oxygen content of the shielding gas is ≤50 ppm. Using a shielding gas with an oxygen content of ≤50 ppm can inhibit tin oxidation during soldering and improve board production efficiency. For example, the shielding gas can be nitrogen.

[0104] When the preheating zone slope is 1-2°C / s, the peak temperature is 242-248°C, and the time above liquidus is 50-60s, boards can be produced with a single reflow soldering operation, reducing the board void rate and effectively increasing the current conduction cross-sectional area. This improves VR remote conversion efficiency and reduces Rpath at a low cost. Furthermore, the preparation method of the present invention can shorten the preparation time by at least 20s, thereby improving preparation efficiency.

[0105] The preheating zone slope refers to the preheating temperature rise rate, the peak temperature refers to the reflow soldering temperature, and the time above liquidus refers to the time the temperature is maintained after the tin sheet 2 melts into liquid.

[0106] Exemplarily, the slope of the preheating zone is any one of 1°C / s, 1.2°C / s, 1.3°C / s, 1.5°C / s, 1.8°C / s, and 2°C / s, or a range consisting of any two of them; the peak temperature can be any one of 242°C, 243°C, 245°C, 247°C, and 248°C, or a range consisting of any two of them; and the time above liquidus can be any one of 50s, 52s, 54s, 56s, 58s, and 60s, or a range consisting of any two of them.

[0107] The second aspect of the present application provides a board card, which is prepared by the preparation method of the first aspect.

[0108] Since the board card of the present application is prepared by the preparation method of the first aspect, the board card of the present application has a lower void rate, which can solve the problem of improving VR remote conversion efficiency and reducing high Rpath costs in related technologies.

[0109] The third aspect of the present application provides a server, including the board card of the second aspect, and the server has higher VR remote conversion efficiency and lower Rpath.

[0110] The above is a detailed introduction to the preparation method of a board provided by the present application, the board, and its application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only intended to help understand the method and core ideas of the present application. It should be pointed out that, for those skilled in the art, without departing from the principles of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the claims of the present application.

Claims

1. A method for preparing a board, characterized in that: include: Performing tin plating on one surface of the copper substrate to obtain a first middle copper busbar including a tin layer; Performing an aging treatment on the first intermediate copper busbar to obtain a second intermediate copper busbar including a tin-copper composite layer and a copper layer; An insulating layer is provided on the other surface of the copper substrate to form a copper busbar including a tin layer, a tin-copper composite layer, a copper layer and an insulating layer in a stacking direction; After the copper busbar and the tin sheet are stacked, they are packaged in a hard tray, with the tin layer being placed close to the tin sheet; Using a fitting, the copper busbar and the tin sheet packaged in the hard tray are attached to the surface of the printed circuit board, wherein the tin sheet is placed close to the printed circuit board; Performing a reflow soldering to obtain the board; Wherein, the thickness of the tin layer is 3-5 μm; The thickness of the tin-copper composite layer is 1.5-2 μm; The dielectric strength of the insulating layer is ≥200V / μm; The thermal conductivity of the insulating layer is 1-1.5 W / m·K; The electrical conductivity of the copper layer is ≥58MS / m; The yield strength of the copper layer is ≥240 MPa.

2. The preparation method according to claim 1, characterized in that The surface roughness of the tin layer is 0.3-0.5 μm; and / or, During the aging treatment, the temperature is 240-270° C. and the time is 40-70 seconds.

3. The preparation method according to claim 1 or 2, characterized in that The edge of the orthographic projection of the tin sheet on the copper busbar coincides with the edge of the copper busbar and / or is located within the edge of the copper busbar.

4. The preparation method according to claim 3, characterized in that The distance between the edge of the orthographic projection and the edge of the copper busbar is 0.1-0.2 mm.

5. The preparation method according to claim 1, characterized in that The tin sheet comprises a tin body layer and a soldering layer which are stacked together, and the soldering layer is arranged close to the printed circuit board.

6. The preparation method according to claim 5, characterized in that The thickness of the tin sheet is 0.15-0.25 mm; and / or, The tin body layer comprises, by mass percentage, 96.5% Sn, 3% Ag, and 0.5% Cu; and / or The void ratio of the tin bulk layer is less than 5%; and / or, Based on the total mass of the tin sheet, the mass percentage of the soldering layer is 3.5-10%.

7. The preparation method according to claim 1, characterized in that Before the reflow soldering, the method further includes arranging copper wires on the side walls of the tin sheet.

8. The preparation method according to claim 7, characterized in that The diameter of the copper wire is less than or equal to 1 / 2 of the thickness of the tin sheet.

9. The preparation method according to claim 1, characterized in that During the primary reflow soldering, the oxygen content in the protective gas is ≤50ppm; and / or, In the one-time reflow soldering, the slope of the preheating zone is 1-2° C. / s, the peak temperature is 242-248° C., and the liquid phase time is 50-60 s.

10. A board, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 9.

11. A server, characterized in that: Including the board described in claim 10.

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