Structure for preventing welding voidage

Abstract

The utility model provides a structure for preventing welding voidage, which comprises a PCB (printed circuit board) and a welding piece, and further comprises a bus bar, a support block and a tray frame in a SMT (surface mount technology) secondary welding state, the PCB, the welding piece, the bus bar, the support block and the tray frame are arranged from top to bottom in sequence, the welding piece is positioned on the B surface of the PCB, and device welding is performed on the A surface of the PCB during secondary welding. According to the embodiment of the invention, the bus bar is applied only during the second reflow soldering, so that the welding void rate is reduced, and the through-current capability is improved.

Description

Technical Field

[0001] The present invention relates to the field of SMT process technology, and in particular to a structure for preventing soldering voids. Background Art

[0002] Soldering busbars on PCBs (Printed Circuit Boards) is a solution to improve the flow capacity of PCBs. However, during the SMT production process, the flux components in the soldering sheet are vaporized, and the gas is difficult to be discharged from the large-sized soldering surface, and eventually remains in the solidified solder interface to form solder voids. During the secondary processing of SMT, during the second reflow, the solder voids generated by the first reflow will further increase, resulting in an increase in the solder void rate, affecting the flow capacity of the PCB.

[0003] As far as the inventors know, the above problems can usually be overcome by increasing the thickness of the copper foil of the PCB or increasing the number of PCB layers. However, both solutions will bring problems of structural reliability and high cost. Summary of the invention

[0004] In order to overcome the problems existing in the related art, this specification provides a structure for preventing welding void rate, which can reduce welding void rate and avoid the problems of high cost and structural reliability.

[0005] According to an embodiment of the present specification, a structure for preventing solder void rate is provided, including a PCB board and a soldering part. In the SMT second soldering state, the structure also includes a bus bar, a support block and a tray frame. The structure is arranged from top to bottom in the order of a PCB board, a soldering part, a bus bar, a support block and a tray frame. The soldering part is located on the B side of the PCB board, and the device is soldered on the A side of the PCB board during the second soldering.

[0006] Preferably, the PCB board, the welding piece, the bus bar and the supporting block are positioned by a positioning piece.

[0007] Furthermore, the positioning piece is a buckle.

[0008] Preferably, the support block and the tray frame are supported by support members.

[0009] Furthermore, the supporting member is a screw.

[0010] Preferably, a spring is provided on the screw, the screw passes through one side of the tray frame, and the spring is located between the tray frame and the support block.

[0011] Preferably, the support block and the tray frame are supported by elastic support members.

[0012] Furthermore, the tray frame includes a bottom plate and a surrounding edge, the surrounding edge is arranged around the bottom plate, the support block is supported on the bottom plate by a support member, and the height of the surrounding edge is flush with or slightly lower than the A surface of the PCB board.

[0013] Furthermore, the bottom plate of the tray frame is provided with a plurality of hollow holes.

[0014] Furthermore, a positioning column is provided at the edge of the hollow hole in the middle part of the bottom plate of the tray frame, and the positioning column passes through the PCB board from bottom to top.

[0015] Preferably, in the first SMT welding state, a PCB board, a welding part, a support block and a tray frame are arranged from top to bottom, and components are welded on the B side of the PCB board during the first welding.

[0016] The technical solutions provided by the embodiments of this specification may have the following beneficial effects:

[0017] In the embodiments of this specification, the bus bar is only used during the second reflow soldering, which reduces the soldering void rate and improves the flow capacity.

[0018] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the specification and, together with the description, serve to explain the principles of the specification.

[0020] Figure 1 is a cross-sectional view of the tooling structure of an embodiment of the present application;

[0021] Figure 2 This is a schematic diagram of the pallet frame structure of an embodiment of the present application;

[0022] Figure 3 It is a schematic diagram of the busbar structure of an embodiment of the present application;

[0023] Figure 4 This is a bottom view of the support block of the present application installed on the PCB board.

[0024] Number Description:

[0025] 1-tray frame; 11-bottom plate; 111-hollow hole; 112-positioning column; 12-edge; 2-bus bar; 21-alignment groove; 3-PCB board; 4-welding piece; 5-support block; 51-positioning buckle; 6-support piece; 7-positioning piece DETAILED DESCRIPTION

[0026] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementations described in the following exemplary embodiments do not represent all implementations consistent with this specification. Instead, they are merely examples of devices and methods consistent with some aspects of this specification as detailed in the appended claims.

[0027] The terms used in this specification are for the purpose of describing specific embodiments only and are not intended to limit this specification. The singular forms "a", "the" and "the" used in this specification and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0028] It should be understood that although the terms first, second, third, etc. may be used in this specification to describe various information, this information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of this specification, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining".

[0029] First of all, it should be explained that the solder void rate in this application refers to the fact that during the SMT production process, due to the gasification of the flux components in the soldering sheet, the gas is difficult to be discharged in the large-sized soldering surface, and finally remains in the solidified solder interface to form solder voids. Such solder voids will cause the soldering area between the busbar and the PCB board to decrease, the resistance value to increase, and ultimately affect the busbar flow performance. The PCB board includes side A and side B, side A refers to the top of the PCB board, and side B refers to the back of the PCB board. SMT processing is the abbreviation of surface mount technology (Surface Mount Technology), which is a method for installing and soldering electronic components. In SMT processing, electronic components are directly mounted on the surface of the printed circuit board (PCB board) instead of being assembled through traditional plug-in components. The SMT processing process includes the first soldering and the second soldering. The first soldering refers to the device soldering on the A side of the PCB board, and most of the devices such as connectors, resistors, capacitors, and chips are located on the front of the PCB board. The second soldering refers to the device soldering on the B side of the PCB board. In order to provide current to the CPU at low cost and high efficiency, the busbar is welded on the channel that provides current to the CPU to increase the cross-sectional area of ​​the current-carrying conductor, reduce circuit resistance, and improve current carrying capacity. The busbar is usually made of conductive materials, such as copper or aluminum, to ensure sufficient conductivity and durability. If the busbar is used in both the first and second welding, it will cause the voids to expand and increase the void rate.

[0030] like Figure 1As shown, the embodiment of the present application provides a structure for preventing the void rate of welding. During the processing of SMI, at least a PCB board 3 and a welding piece 4 are required. The embodiment of the present application requires that only during the second welding of SMI, the tooling structure includes a bus bar 2, a support block 5 and a tray frame 1. From the setting point of view, from top to bottom, it is arranged in sequence as a PCB board 3, a welding piece 4, a bus bar 2, a support block 5 and a tray frame 1. A welding piece 4 is arranged on the B side of the PCB board 3, and other components are arranged in sequence. The second welding is to perform device welding on the A side of the PCB board. The embodiment of the present application also requires that during the first welding of SMI, from the setting point of view, when it is arranged in sequence from top to bottom, the bus bar is cancelled, and only the PCB board 3, the welding piece 4, the support block 5 and the tray frame 1 are included. The first welding is to perform device welding on the B side of the PCB board. In the embodiment of the application, the first welding and the second welding can be in the form of reflow soldering. In the embodiment of the present application, during the first welding, the PCB board 3 is directly supported by the support block 5 for welding. The busbar 2 is used only during the second welding, so the void rate is only generated during the second welding, which reduces the welding void rate and improves the current carrying capacity. Because the busbar is powered on and used after the PCB board is manufactured, and the PCB board printing process usually makes the B side first and then the A side, the busbar is only added during the second welding of the SMT process and will not affect the performance of the PCB board. The current carrying capacity here refers to the maximum current value that electrical equipment, components or conductive materials can withstand and transmit. It is a measure of the ability of equipment or materials to conduct current continuously under normal operating conditions. In the above structure, the tray frame gives the busbar a stable and uniform thrust, so that the busbar is still in reliable contact with the PCB when the installation surface is facing down, and welding is achieved on the B side of the PCB board. Because the tray frame provides appropriate pressure on the busbar, it helps to discharge the air formed during the welding process and reduce the welding void rate.

[0031] like Figure 1 As shown, during the second welding, the PCB board 3, the welding part 4, the bus bar 2 and the support block 5 are positioned by the positioning part 7. As an example, the positioning part in the embodiment of the present application is a buckle. As an example, the welding part here can be a welding sheet, and the bus bar can be T-shaped, L-shaped or other shapes. The shape of the bus bar is mainly related to the location of the multi-phase power supply above the bus bar that powers the CPU in the PCB board and the position of the CPU's pads. For example: If the multi-phase power supply above the CPU is arranged horizontally and the PCU's pads are arranged vertically, then the bus bar can be T-shaped, such as Figure 3-Figure 4As shown. The shape of the support block is consistent with the shape of the busbar. In order to position the busbar, an alignment groove 21 is provided on the busbar 2, and the positioning buckle 51 on the support block 5 cooperates with the alignment groove to achieve positioning installation. The support block can be made of aluminum alloy material, such as 7075 aluminum alloy. Of course, other models can also be used. This is only related to the service life. The support block in contact with the busbar is made of aluminum alloy, which can reduce the local temperature of the busbar during reflow soldering, reduce the vaporization of flux, and promote the reduction of welding void rate.

[0032] In the embodiment of the present application, the support block 5 and the tray frame 1 are supported by a support member 6. The support member can be formed by screws, rivets, welding, adhesive bonding, etc., which is only used as an example and does not constitute a limitation.

[0033] Embodiment 1: Figure 1 As shown, the screw can be provided with a spring to achieve flatness adjustment. The screw passes through one side of the tray frame, and the spring is located between the tray frame and the support block. Because (1) there are problems with the tooling that is easy to deform, such as the PCB board; (2) there are many tolerance problems, such as the height of the busbar or the tooling step. Therefore, it is necessary to adjust the flatness through a spring.

[0034] Embodiment 2: The support block and the tray frame may be supported by an elastic support member (not shown in the figure), such as a polymer elastic material, a magnetic material, etc., because the basic principle is basically the same as that of embodiment 1, it will not be repeated here. The flatness is adjusted by the method of embodiment 2.

[0035] In the present application embodiment, Figure 1-Figure 2As shown, the tray frame 1 includes a bottom plate 11 and a surrounding edge 12, and the surrounding edge 12 is arranged around the bottom plate 11. The support block 5 is supported on the bottom plate 11 by the support member 6, and the height of the surrounding edge 12 is flush with or slightly lower than the A surface of the PCB board 3. In the SMT processing process, the PCB board needs to be bonded with the steel mesh, so the surrounding edge cannot exceed the A surface of the PCB board to avoid affecting the bonding printing of the steel mesh and the PCB board. The bottom plate 11 of the tray frame is provided with a plurality of hollow holes 111, which is conducive to ventilation so that the hot air can fully contact the PCB board. The temperature difference between the A surface and the B surface of the PCB board should not be too large. Usually, the A surface of the PCB board is fully in contact with the environment, and the temperature is higher than the B surface. If the temperature difference between the A surface and the B surface of the PCB board is too large, it is easy to cause the PCB board to arch due to thermal expansion and contraction. The hollow holes are mostly rectangular or square, because the positioning points on the PCB board are used to set the positioning columns 112, and the positioning points are set in advance. In order to shorten the path, the hollow holes 111 are mostly set to be rectangular or square. In addition, because the device arrangement is mainly rectangular or square projection, regional ventilation is convenient and interference and obstruction are not easy. The edge of the hollow hole 111 in the middle part of the bottom plate 11 of the tray frame 1 is provided with a positioning column 112, and the positioning column is passed from bottom to top to the PCB board. The positioning column is conducive to the more convenient and quick installation of the PCB board, welding parts, bus bars and support parts during tooling.

[0036] Embodiment (1) of the present application can improve the busbar welding void rate and help the busbar achieve a better flow effect.

[0037] (2) Reducing the busbar welding void rate can reduce the CPU area temperature and alleviate the heat dissipation bottleneck.

[0038] (3) As the void rate of busbar welding decreases, the power utilization rate on the current path is improved. For example, based on an estimate for a standard 2U server with a CPU TDP350W, electricity costs can be saved by RMB 198 to RMB 337 (the electricity price is RMB 0.67 per kWh) over a five-year usage period.

[0039] (4) No additional changes are required to the PCB board. Improvements can be achieved after a one-time investment in tooling, and subsequent maintenance costs are extremely low.

[0040] The implementation process of the functions and effects of each module in the above-mentioned device is specifically described in the implementation process of the corresponding steps in the above-mentioned method, which will not be repeated here.

[0041] For the device embodiment, since it basically corresponds to the method embodiment, the relevant parts can refer to the partial description of the method embodiment. The device embodiment described above is only schematic, wherein the modules described as separate components may or may not be physically separated, and the components displayed as modules may or may not be physical modules, that is, they may be located in one place, or they may be distributed on multiple network modules. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this specification. A person of ordinary skill in the art can understand and implement it without paying creative labor.

[0042] The above is a description of a specific embodiment of the specification. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recorded in the claims can be performed in an order different from that in the embodiments and still achieve the desired results. In addition, the processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0043] Those skilled in the art will readily appreciate other embodiments of the specification after considering the specification and practicing the invention claimed herein. The specification is intended to cover any variations, uses or adaptations of the specification that follow the general principles of the specification and include common knowledge or customary techniques in the art that are not claimed in the specification. The specification and examples are to be considered exemplary only, and the true scope and spirit of the specification are indicated by the following claims.

[0044] It should be understood that the present description is not limited to the precise structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present description is limited only by the appended claims.

[0045] The above description is only a preferred embodiment of this specification and is not intended to limit this specification. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of this specification should be included in the scope of protection of this specification.

Claims

1. A structure for preventing solder void rate, comprising a PCB board and a soldering part, characterized in that: In the second SMT welding state, it also includes a bus bar, a support block and a tray frame, which are arranged from top to bottom in the order of a PCB board, a welding part, a bus bar, a support block and a tray frame. The welding part is located on the B side of the PCB board, and the device is welded on the A side of the PCB board during the second welding.

2. The structure for preventing solder voids according to claim 1, characterized in that: The PCB board, welding piece, bus bar and supporting block are positioned by positioning pieces.

3. The structure for preventing solder voids according to claim 2, characterized in that: The positioning piece is a buckle.

4. The structure for preventing solder voids according to claim 1, characterized in that: The support block and the pallet frame are supported by support members.

5. The structure for preventing solder voids according to claim 4, characterized in that: The supporting member is a screw.

6. The structure for preventing solder voids according to claim 5, characterized in that: A spring is passed through the screw, the screw passes through one side of the tray frame, and the spring is located between the tray frame and the support block.

7. The structure for preventing solder voids according to claim 1, characterized in that: The support block and the tray frame are supported by elastic support members.

8. The structure for preventing solder voids according to claim 7, characterized in that: The tray frame includes a bottom plate and a surrounding edge, wherein the surrounding edge is arranged around the bottom plate, and the support block is supported on the bottom plate by a support member, and the height of the surrounding edge is flush with or slightly lower than the A surface of the PCB board.

9. The structure for preventing solder voids according to claim 8, characterized in that: The bottom plate of the tray frame is provided with a plurality of hollow holes.

10. The structure for preventing solder voids according to claim 9, characterized in that: A positioning column is provided at the edge of the hollow hole in the middle part of the bottom plate of the tray frame, and the positioning column penetrates the PCB board from bottom to top.

11. The structure for preventing welding voids according to any one of claims 1 to 10, characterized in that: In the first SMT welding state, the arrangement from top to bottom is PCB board, welding parts, support block and tray frame. During the first welding, the components are welded on the B side of the PCB board.

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