Preparation method of board card, board card and application

Abstract

The invention discloses a preparation method of a board card, the board card and application, and relates to the technical field of board card processing, and the method comprises the step of welding a printed circuit board, a tin sheet and a copper bar through reflow soldering, can effectively improve the uniformity of solder filling, inhibits gas residues in the flowing process of molten solder, effectively reduces the voidage of the board card, and improves the quality of the board card. The current conduction sectional area is effectively improved, the VR far-end conversion efficiency is improved with low cost, and the Rpath is reduced.

Description

Technical Field

[0001] This application relates to the technical field of board card processing, and particularly to a preparation method, a board card and an application of a board card. Background Art

[0002] In the power supply system of a central control unit (CPU), the printed circuit board (PCB) path impedance (Rpath) from the output inductor of a voltage regulator (VR) to the CPU load end is one of the core parameters affecting the power supply performance. The physical essence of the path impedance is the ohmic impedance generated when the current flows through the copper layer of the PCB, and its value is jointly determined by the copper foil thickness, the trace length / width, the stack-up structure, and the operating temperature.

[0003] The related technologies mainly rely on the upgrade of the PCB stack-up and copper thickness to reduce the path impedance of the PCB, but this method will bring a substantial increase in the cost of the PCB. Thus, how to improve the VR far-end conversion efficiency and reduce Rpath without increasing the cost is a technical problem that urgently needs to be solved. Summary of the Invention

[0004] This application provides a board card, a preparation method and an application thereof, so as to solve the problem of high cost in improving the VR far-end conversion efficiency and reducing Rpath in the related technologies.

[0005] This application provides a preparation method of a board card, including:

[0006] Performing tin plating treatment on one surface of a copper substrate to obtain a first intermediate copper row including a tin layer;

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

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

[0009] Stacking the copper row and a tin sheet, and then packaging them with a rigid tray, with the tin layer close to the tin sheet;

[0010] Using a fitting to attach the copper row and the tin sheet after being packaged with the rigid tray to the surface of the printed circuit board, with the tin sheet close to the printed circuit board;

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

[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 insulating layer ≥ 200 V / μm;

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

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

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

[0018] In the method for preparing the board card of the present application, a prefabricated tin sheet is used to solder a copper row with a special structure onto the surface of a printed circuit board through one-time reflow soldering 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 soldering process, inhibit gas residues during the flow of molten solder, effectively reduce the void ratio of the board card, effectively increase the current conduction cross-sectional area, improve the VR remote conversion efficiency at a lower cost, and reduce the Rpath; while the copper row 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 endow the board card with excellent heat dissipation, electrical isolation and mechanical properties. Therefore, the preparation method of the present invention can obtain a board card with a low void ratio, excellent heat dissipation, electrical isolation and mechanical properties at an extremely low cost, and is suitable for wide promotion and application.

[0019] The present application provides a board card prepared by the above-mentioned method for preparing a board card.

[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 ratio, can solve the problem of high cost in improving the VR remote conversion efficiency and reducing the Rpath in the related art, and the board card of the present invention also has excellent heat dissipation, electrical isolation and mechanical properties, and can be widely applied and promoted.

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

[0022] The server including the above-mentioned board card has a high VR remote conversion efficiency, a low Rpath, and 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 will briefly introduce the drawings required for the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0024] Figure 1 It is a schematic diagram of a preparation process of a board card provided for an embodiment of the present application;

[0025] Figure 2Schematic diagram of the manufacturing process of another board card provided by the embodiments of the present application;

[0026] Figure 3 Schematic diagram of the structure of a copper bar from a perspective provided by the embodiments of the present application;

[0027] Figure 4 Schematic diagram of the structure of a copper bar from another perspective provided by the embodiments of the present application;

[0028] Figure 5 Schematic diagram of the structure of a tin sheet from the first perspective provided by the embodiments of the present application;

[0029] Figure 6 Schematic diagram of the structure of a tin sheet from the second perspective provided by the embodiments of the present application;

[0030] Figure 7 Schematic diagram of the structure of a tin sheet from the third perspective provided by the embodiments of the present application.

[0031] Among them, the above-mentioned drawings include the following reference numerals:

[0032] 1: Printed circuit board;

[0033] 2: Tin sheet;

[0034] 3: Copper bar;

[0035] 4: Soft pad;

[0036] 5: Fixture;

[0037] 21: Solder assistant layer;

[0038] 22: Tin body layer;

[0039] 23: Side wall;

[0040] 31: Tin layer;

[0041] 32: Insulating layer;

[0042] 33: Tin-copper composite layer;

[0043] 34: Copper layer. Detailed implementation manners

[0044] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0045] It should be noted that in the description of this application, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly 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 specific order or sequence.

[0046] With the upgrade of the CPU, the demand for the board is getting higher and higher, and there are restrictive factors such as difficult PCB wiring, increased board layer or copper thickness. In view of this, the inventor found in the research that optimizing the connection between the copper busbar and the PCB can improve the performance of the board and save costs.

[0047] In order to enable those skilled in the art of this technology to better understand the solution of this application, the following further detailed description of this application will be given in conjunction with the drawings and specific embodiments.

[0048] In this application, the void ratio refers to the volume ratio of the tiny bubbles (voids) formed inside the solder joints due to factors such as gas residue, solder shrinkage or contamination after welding, and is usually expressed as a percentage (%). Void ratio = (total volume of voids / total volume of solder joints) × 100%. Exemplarily, the void ratio of the board refers to the volume percentage of the voids in the board.

[0049] Figure 1 Schematic diagram of a preparation process for a board provided by an embodiment of this application; Figure 2 Schematic diagram of another preparation process for a board provided by an embodiment of this application; Figure 3 Schematic diagram of the structure of a copper busbar from a perspective provided by an embodiment of this application; Figure 4 Schematic diagram of the structure of a copper busbar from another perspective provided by an embodiment of this application. As Figure 1 ,[[]]END]] Figure 2 ,[[]]END]] Figure 3 and Figure 4 shown, the first aspect of this application provides a method for preparing a board, including:

[0050] Perform tin plating treatment on one surface of the copper substrate to obtain a first intermediate copper busbar including a tin layer 31;

[0051] Age 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] Set an insulating layer 32 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 laminating the copper busbar 3 and the tin sheet 2, they are packaged with a rigid tray, and the tin layer 31 is arranged close to the tin sheet 2;

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

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

[0056] Among them, 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 ≥ 200 V / μm;

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

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

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

[0062] Specifically, perform tin plating on one surface of the copper substrate, thereby forming a tin layer 31 on one surface of the copper substrate to obtain a first intermediate copper busbar including the tin layer 31; then perform an aging treatment on the first intermediate copper busbar to make the tin layer 31 and the copper substrate fuse with each other to form a tin - copper composite layer 33 including a tin - copper composite phase (for example, Cu6Sn5 phase), and the remaining copper substrate forms a copper layer 34 to obtain a second intermediate copper busbar including the tin - copper composite layer 33 and the copper layer 34; set an insulating layer 32 on the surface of the second intermediate copper busbar away from the tin layer 31 to form 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 lamination direction;

[0063] After laminating the copper busbar 3 and the tin sheet 2 in sequence according to 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, they are packaged with a rigid tray and adsorbed by the automatic suction device of the mounter; at the same time, use a fitting to attach the copper busbar 3 and the tin sheet 2 after being packaged with the rigid tray to the surface of the printed circuit board 1;

[0064] Then perform reflow soldering. In the reflow soldering, the solid tin sheet 2 will melt into liquid tin, and after the liquid tin solidifies, it will attach the copper busbar 3 and the printed circuit board 1 together, thereby obtaining 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 row 3 with a special structure and a printed circuit board 1 to prepare a board card. 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 ratio of the board card, effectively increase the current conduction cross-sectional area, improve the VR remote conversion efficiency at a lower cost, and reduce the Rpath. During the welding process, a fitting is used to fit the tin sheet 2 and the copper row 3 to the printed circuit board 1, which can improve the welding quality and further reduce the void ratio of the board card. At the same time, the board card can be prepared by the present application only through one-time reflow soldering, which is not only simple in operation but also can greatly reduce the void ratio of the board card. The copper row 3 with a special structure can not only improve the electrical isolation, heat dissipation performance and mechanical performance of the board card, but also better melt with the solid tin sheet 2, further improving the welding quality, reducing the void ratio of the board card, and improving the conductivity of the board card. In summary, the preparation method of the present application can prepare a board card with excellent electrical conductivity, heat dissipation, electrical isolation and mechanical properties, and the preparation method is simple in operation and low in cost, suitable for wide promotion and application.

[0068] In some embodiments, compared with the related art, 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, tin plating treatment and aging treatment can be first performed on one surface of the copper substrate, and then an insulating layer 32 is provided on the other surface of the copper substrate to form the copper row 3; alternatively, an insulating layer 32 can be first provided on one surface of the copper substrate, and then tin plating treatment and aging treatment are performed on the other surface of the copper substrate.

[0070] The present application does not make a special limitation on the specific form of realizing reflow soldering. For example, reflow soldering can be performed through at least one of a reflow oven, an infrared heating lamp, and a hot air gun.

[0071] In the present application, the tin sheet 2 and the copper row 3 can be provided on one surface of the printed circuit board 1, and the board card is prepared by reflow soldering; alternatively, the tin sheet 2 and the copper row 3 can be respectively provided on the two surfaces of the printed circuit board 1, and the board card is prepared by reflow soldering.

[0072] When the tin sheet 2 and the copper row 3 are respectively provided on the two surfaces of the printed circuit board 1 and reflow soldering is performed to prepare the board card, when welding on the second surface, a jig 5 is required to locally shield the position of the copper row 3 to prevent the position of the copper row 3 from reaching the molten tin temperature.

[0073] In the present application, the external dimensions of the copper row 3 and the tin sheet 2 can be selected according to the current-carrying requirements and the PCB layout design.

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

[0075] Exemplarily, the dielectric constant of the insulating layer 32 can be any one of 200V / μm, 250V / μm, 270V / μm, 300V / μm, 400V / μm or the range composed of any two of them; the thermal conductivity of the insulating layer 32 can be any one of 1 W / m·K, 1.2 W / m·K, 1.3 W / m·K, 1.4 W / m·K, 1.5 W / m·K or the range composed of any two of them. Preferably, the thermal conductivity of the insulating layer 32 is 1.2W / m·K;

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

[0077] Exemplarily, the conductivity of the copper layer 34 can be any one of 58MS / m, 60MS / m, 63MS / m, 67MS / m, 80MS / m, 100MS / m or the range composed of any two of them; the yield strength of the copper layer 34 can be any one of 240MPa, 243MPa, 250MPa, 270MPa, 300MPa or the range composed of any two of them. In some embodiments, the copper layer 34 can be T2Y2 oxygen-free copper (purity greater than or equal to 99.95%) with excellent electrical conductivity, thermal conductivity, corrosion resistance and processability. Compared with conventional C1100 copper material (conductivity is 56MS / m, yield strength is 200MPa), T2Y2 oxygen-free copper has more excellent electrical conductivity and mechanical properties.

[0078] In some embodiments of the present application, the tin plating treatment can be matte tin deposition treatment. Compared with the traditional bright tin treatment, the surface roughness of the tin layer 31 formed by the matte tin deposition treatment is larger, which can increase the interfacial bonding area between the tin layer 31 and the tin sheet 2, improve the fusibility between the tin layer 31 and the tin sheet 2, improve the welding quality, and further improve the electrical conductivity of the board. For example, the surface roughness Ra of the tin layer 31 formed by the matte tin deposition treatment is 0.3 - 0.5μm, and the surface roughness Ra of the tin layer 31 formed by the bright tin treatment is 0.1μm.

[0079] Exemplarily, the surface roughness of the tin layer 31 can be any one of 0.3μm, 0.35μm, 0.4μm, 0.43μm, 0.45μm, 0.5μm or the range composed of any two of them.

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

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

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

[0083] Figure 5 It is a schematic structural diagram of the tin sheet from the first perspective provided by the embodiment of this application; Figure 6 It is a schematic structural diagram of the tin sheet from the second perspective provided by the embodiment of this application; Figure 7 It is a schematic structural diagram of the tin sheet from the third perspective provided by the embodiment of this application. According to Figure 5 、 Figure 6 and Figure 7 , in some embodiments of this 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 irradiates 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; part of the edge of the orthographic projection can be 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 coincides 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 located within the edge of the copper busbar 3 or part of the edge of the orthographic projection is located within the edge of the copper busbar 3 and the other part coincides 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 less than or equal to the size of the copper busbar 3, during welding, the tin sheet 2 is not likely to overflow, which can save the tin sheet 2 and improve the welding quality.

[0088] Further, 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 at any position and the edge of the copper busbar 3. 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 retracted by 0.1 - 0.2 mm relative to the edge of the copper busbar 3. This setting can further avoid tin overflow during welding, save the tin sheet 2, and improve the welding quality at the same time.

[0089] Exemplarily, the distance between the edge of the orthographic projection and the edge of the copper busbar 3 can be any one of 0.1 mm, 0.12 mm, 0.13 mm, 0.14 mm, 0.16 mm, 0.19 mm, 0.2 mm or the range composed of any two of them.

[0090] As Figure 5 shown, in some embodiments of the present invention, the tin sheet 2 includes a stacked tin body layer 22 and a soldering aid layer 21, and the soldering aid layer 21 is arranged close to the printed circuit board 1. Among them, the soldering aid 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] Further, when the thickness of the tin sheet 2 is 0.15 - 0.25 mm, the bonding force between the copper busbar 3 and the printed circuit board 1 can be improved while saving the tin sheet 2, thereby improving the comprehensive performance of the board.

[0092] Exemplarily, the thickness of the tin sheet 2 can be any one of 0.15 mm, 0.16 mm, 0.17 mm, 0.2 mm, 0.22 mm, 0.24 mm, 0.25 mm or the range composed of any two of them. Specifically, the thickness of the tin sheet 2 can be 0.2 mm.

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

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

[0095] Exemplarily, the porosity of the tin body layer 22 can be any one of 4%, 3%, 2%, 1%, 0.5% or the range composed of any two of them.

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

[0097] Exemplarily, based on the total mass of the tin sheet 2, the mass percentage content of the soldering aid layer 21 can be any one of 3.5%, 4%, 5%, 6%, 7%, 9%, 10% or the range composed of any two of them.

[0098] In some embodiments, the mass percentage content of the soldering aid layer 21 can be further selected according to the surface composition of the printed circuit board 1, so as to further promote the soldering of the tin sheet 2 and the printed circuit board 1 and improve the comprehensive performance of the board. Exemplarily, if the surface of the printed circuit board 1 is plated with an oxide film (OSP), then in the tin sheet 2, the mass percentage content of the soldering aid layer 21 is 8-10%; if the surface of the printed circuit board 1 is treated by immersion gold, then in the tin sheet 2, the mass percentage content of the soldering aid layer 21 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 aid layer 21 to avoid blocking the nozzle of the mounter by the soldering aid layer 21.

[0100] In some embodiments of the present invention, before the reflow soldering, it further includes arranging copper wires on the side peripheral wall 23 of the tin sheet 2.

[0101] As Figure 7 shown, from this perspective, the tin sheet 2 has a side peripheral wall 23. By arranging copper wires on the side peripheral wall 23 of the tin sheet 2, the liquid tin is not easy to escape to the periphery of the copper row 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 row 3 and the PCB can be further improved. Preferably, the diameter of the copper wire is 0.1 mm.

[0103] Furthermore, in a single reflow soldering, the oxygen content in the protective gas ≤ 50 ppm. Using a protective gas with an oxygen content ≤ 50 ppm can inhibit the oxidation of tin during the soldering process and improve the preparation efficiency of the board. Exemplarily, the protective gas can be nitrogen.

[0104] When the slope of the preheating zone is 1-2 °C / s, the peak temperature is 242-248 °C, and the time above the liquid phase is 50-60 s, the board can be prepared by a single reflow soldering, reducing the void ratio of the board, and then effectively increasing the current conduction cross-sectional area, improving the VR remote conversion efficiency at a lower cost and reducing the Rpath. And the preparation method of the present invention can shorten the preparation time by at least 20 s, improving the preparation efficiency.

[0105] Among them, the slope of the preheating zone refers to the heating rate of preheating, the peak temperature refers to the temperature of reflow soldering, and the time above the liquid phase refers to the time when the temperature is maintained after the tin sheet 2 melts into a liquid state.

[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, 2 °C / s or a range composed of any two of them; the peak temperature can be any one of 242 °C, 243 °C, 245 °C, 247 °C, 248 °C or a range composed of any two of them; the time above the liquid phase can be any one of 50 s, 52 s, 54 s, 56 s, 58 s, 60 s or a range composed of any two of them.

[0107] The second aspect of the present application provides a board card 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 low void ratio and can solve the problems of improving the VR remote conversion efficiency and high Rpath cost in the related art.

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

[0110] The preparation method, the board card and the application of a board card provided by the present application are introduced in detail above. Specific examples are used herein to elaborate the principle and implementation manner of the present application. The description of the above embodiments is only used to help understand the method and its core idea of the present application. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims

1. A method for preparing a board card, characterized in that, Comprising: Tin plating is performed on one surface of a copper substrate to obtain a first intermediate copper row including a tin layer; The first intermediate copper row is subjected to an aging treatment to obtain a second intermediate copper row 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 row including a tin layer, a tin-copper composite layer, a copper layer, and an insulating layer in the stacking direction; After the copper row and the tin sheet are stacked, they are packaged with a rigid tray, and the tin layer is disposed close to the tin sheet; A fitting is used to attach the copper row and the tin sheet after being packaged with the rigid tray to the surface of a printed circuit board, and the tin sheet is disposed close to the printed circuit board; One-time reflow soldering is performed to obtain the board card; 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 ≥ 200 V / μm; The thermal conductivity of the insulating layer is 1 - 1.5 W / m·K; The conductivity of the copper layer ≥ 58 MS / m; The yield strength of the copper layer ≥ 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, In the aging treatment, the temperature is 240 - 270 °C and the time is 40 - 70 s.

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 row coincides with the edge of the copper row and / or is located within the edge of the copper row.

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 row is 0.1 - 0.2 mm.

5. The preparation method according to claim 1, wherein The tin sheet includes a stacked tin body layer and a soldering aid layer, and the soldering aid layer is disposed close to the printed circuit board.

6. The preparation method according to claim 5, wherein The thickness of the tin sheet is 0.15 - 0.25 mm; and / or, The tin body layer includes, by mass percentage: Sn 96.5%, Ag 3%, Cu 0.5%; and / or, The porosity of the tin body layer is less than 5%; and / or, Based on the total mass of the tin sheet, the mass percentage content of the soldering aid layer is 3.5 - 10%.

7. The preparation method according to claim 1, characterized in that, Before the reflow soldering, it further includes arranging copper wires on the side peripheral wall 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, In the one-time reflow soldering, the oxygen content in the protective gas ≤ 50 ppm; 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 card, characterized in that, Prepared by the preparation method according to any one of claims 1 - 9.

11. A server, characterized in that, Including the board card according to claim 10.

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