A welding method

Abstract

The present application relates to the technical field of PCB, and discloses a welding method for welding an electronic component on a solder pad of a PCB corresponding to the electronic component, comprising the following steps: S101. Arranging a first soldering position at each of four corner regions of the solder pad, and printing first solder on the first soldering position; the four first soldering positions are arranged in a rectangular array and form a rectangular soldering area; S102. Arranging at least a second soldering position at a central position of the solder pad, and printing second solder on the second soldering position; S103. Printing a tin sheet on the first solder and the second solder, the size of the tin sheet being the same as the area of the soldering area; S104. Mounting the electronic component on the solder pad with the tin sheet; S105. Using reflow soldering to weld the electronic component on the solder pad. In this way, the area of air bubbles after welding is greatly reduced, and the welding quality is improved.

Description

Technical Field

[0001] This invention relates to the field of PCB technology, and more particularly to a soldering method. Background Technology

[0002] SMT (Surface Mount Technology) is currently one of the most popular technologies and processes in the electronics assembly industry. It is an electronic assembly technology that mounts leadless or short-lead surface mount components onto the surface of a printed circuit board or other substrate, and then solders them using methods such as reflow soldering or dip soldering. In SMT, a stencil is a special mold whose main function is to aid in the deposition of solder paste, aiming to transfer the precise amount of solder paste to the corresponding pads on the printed circuit board.

[0003] Currently, QFN (Quad Flat No Lead) packages are experiencing rapid growth in device applications due to their superior performance, including being lightweight, small, thin, having low self-inductance, and efficient heat dissipation. QFN packaged components have pads on their bottom that are level with the bottom surface. During operation, the heat generated by the QFN packaged component is primarily conducted to the printed circuit board through these pads, thereby reducing the component's own temperature. However, during surface mount technology (SMT) soldering, defects in the solder paste placement on the pads, coupled with the presence of air, water, and flux in the solder paste, can easily lead to problems such as air bubbles and voids in the pads. These issues directly affect the heat dissipation performance and efficiency of the QFN packaged components. Summary of the Invention

[0004] The purpose of this invention is to provide a welding method that greatly reduces the area of ​​air bubbles after welding and improves welding quality.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A soldering method for soldering an electronic component onto a pad on a PCB board corresponding to the electronic component includes the following steps: S101. Arranging a first solder position at each of the four corner areas of the pad, and printing first solder on the first solder position, wherein the four first solder positions are arranged in a rectangular array to form a rectangular soldering area; S102. Arranging at least one second solder position at the center of the pad, and printing second solder on the second solder position; S103. Printing a solder sheet on the first solder and the second solder, wherein the size of the solder sheet is the same as the area of ​​the soldering area; S104. Mounting the electronic component onto the pad with the solder sheet; S105. Soldering the electronic component onto the pad using reflow soldering.

[0007] Preferably, in step S101, the four first solder positions are arranged in a rectangular array.

[0008] Preferably, both the first solder and the second solder are Sn-Ag-Cu based solders.

[0009] Preferably, before step S104, the method further includes the following step: preheating the pads and the electronic components at a temperature between 100° and 150°.

[0010] Preferably, in step S103, the thickness of the tin sheet is set to be less than 0.05 mm.

[0011] Compared with the prior art, the beneficial effects of the present invention are: through the steps of the above welding method, the bubbles at the welding point of electronic components after welding can be effectively reduced, which solves the shortcomings of the prior art and improves the welding quality. Attached Figure Description

[0012] Figure 1 This is a flowchart of a welding method according to an embodiment of the present invention. Detailed Implementation

[0013] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0014] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0015] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0016] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0017] See Figure 1 This invention provides a soldering method for soldering a standard electronic component onto a corresponding pad on a PCB board. The electronic component can be a standard surface mount component such as a resistor, capacitor, or chip. The soldering method includes steps S101-S105.

[0018] Step S101: Arrange the first solder positions in the four corner areas of the pad, and apply the first solder to the first solder positions. The four first solder positions are arranged in a rectangular array to form a rectangular soldering area.

[0019] In this step, first solder pads are arranged in a rectangular array at the four corners of the solder pad to ensure stable positioning of the components during the soldering process, effectively restricting the position of the electronic components to be soldered and avoiding the generation of a large number of air bubbles. The first solder applied to each first solder pad is Sn-Ag-Cu based solder. Sn-Ag-Cu based solder has excellent mechanical properties and corrosion resistance, and is inexpensive, making it very suitable for soldering electronic components.

[0020] In one preferred embodiment, the pads are designed in a standard square or rectangular shape, with four first solder pads arranged at the four corners of the pads, forming a rectangular soldering area. This layout provides stable solder joints and facilitates the alignment and fixation of electronic components during the soldering process.

[0021] Step S102: Arrange at least one second soldering position at the center of the solder pad, and print the second solder on the second soldering position.

[0022] In this step, placing a second solder pad at the center of the pad increases the number of solder joints, thereby improving the mechanical strength and reliability of the soldering. This second solder pad at the center, acting as an additional solder joint, works in conjunction with the four first solder pads at the edge to ensure the component is more firmly fixed to the pad, helping to reduce soldering defects and prevent issues such as bubbles and voids on the pad. The second solder applied to each second solder pad is a Sn-Ag-Cu based solder. Sn-Ag-Cu based solders have excellent mechanical properties and corrosion resistance, and are inexpensive, making them very suitable for soldering electronic components.

[0023] Step S103: Print a tin sheet onto the first solder and the second solder.

[0024] In this step, the thickness of the solder sheet is controlled to be below 0.05mm to facilitate heat conduction and solder wetting during the soldering process. It also avoids problems such as excessive thickness of the solder sheet after it is placed on the pad and solder sheet movement. By printing the solder sheet on the first and second solder pads, the soldering of the solder sheet on the pad is more stable, which improves the soldering quality of subsequent electronic components on the pad.

[0025] Next, a solder sheet can be printed onto the first solder and the second solder using a solder sheet printing machine. The solder sheet uses the same Sn-Ag-Cu lead-free solder as the first solder, and its size and shape are adjusted according to the weight and size of the electronic components to ensure sufficient solder amount.

[0026] In a preferred embodiment, the size of the solder sheet is the same as the area of ​​the welding area. Matching the area of ​​the solder sheet to the area of ​​the welding area can ensure that the solder is evenly distributed during welding, avoid uneven welding caused by too much or too little solder, and reduce bubbles at the solder joints of electronic components after welding.

[0027] Step S104: Mount the electronic components onto the solder pads with solder sheets.

[0028] In this step, after the solder sheet printing is completed, an automatic pick-and-place machine is used to precisely place the electronic components onto the solder pads. The automatic pick-and-place machine uses a vision system to confirm the position and orientation of the electronic components, ensuring accurate placement.

[0029] Step S105: Solder the electronic components onto the pads using reflow soldering.

[0030] Finally, the PCB with components mounted is placed in a reflow oven. The reflow oven heats the solder sheets and solder paste using a specific temperature profile, causing the metal solder to melt and flow back, then cool and solidify, forming stable solder joints. During reflow soldering, the first solder, the second solder, and the solder sheets are activated, removing oxides from the metal surfaces and promoting solder flow and wetting, thereby achieving the soldering of electronic components onto the PCB.

[0031] As can be seen from the above, the steps of the above welding method can effectively reduce the bubbles at the solder joints of electronic components after welding, which solves the shortcomings of the background technology and improves the welding quality.

[0032] In a preferred embodiment, prior to step S104, the following step is included: preheating the pads and the electronic components at a temperature between 100°C and 150°C. Specific preheating equipment, such as infrared preheaters, hot air circulation systems, or dedicated preheating sections in reflow ovens, is typically used for this preheating process. The preheating temperature and time need to be precisely controlled based on the PCB material, component characteristics, and solder paste requirements. Preheating is a crucial step in ensuring soldering quality, especially in mass production, as it helps improve the consistency and reliability of the soldering process.

[0033] Based on the disclosure and teachings of the foregoing specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A soldering method for soldering an electronic component onto pads on a PCB board corresponding to the electronic component, characterized in that, Includes the following steps: S101. A first solder position is arranged in each of the four corner areas of the solder pad, and first solder is printed on the first solder position. The four first solder positions are arranged in a rectangular array to form a rectangular soldering area. S102. At least one second soldering position is arranged at the center of the solder pad, and a second solder is printed on the second soldering position; S103. A tin sheet is printed on the first solder and the second solder, the size of the tin sheet being the same as the area of ​​the soldering region; S104. The electronic component is mounted on the pad with the solder sheet; S105. The electronic components are soldered onto the pads using reflow soldering.

2. The welding method according to claim 1, characterized in that, Both the first solder and the second solder are Sn-Ag-Cu based solders.

3. The welding method according to claim 1, characterized in that, Before step S104, the method further includes the following step: preheating the pads and the electronic components at a temperature between 100° and 150°.

4. The welding method according to claim 1, characterized in that, In step S103, the thickness of the tin sheet is set to be less than 0.05 mm.

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