A solder paste mounting and positioning structure for NTC thermistors

Abstract

This utility model discloses an NTC thermistor solder paste mounting and positioning structure, relating to the field of SMT technology. It includes an FPC, a pick-and-place machine, an SMT stencil, and an NTC thermistor. The FPC has reference points and NTC pads. The SMT stencil has two circular openings corresponding to the spacing between the two NTC pads. The diameter of the circular openings is larger than the size of the electrodes of the corresponding NTC thermistor. Solder paste is printed onto the NTC pads through the openings in the SMT stencil, forming two circular solder pastes on the NTC pads. The pick-and-place machine is equipped with a vision camera to identify the circular solder pastes. The vision camera uses the circular solder pastes as the mounting reference points for the NTC thermistors, and the two electrodes of the NTC thermistors are mounted onto the two NTC pads. This utility model, by optimizing the solder paste shape and adding solder paste reference point positioning, compensates for printing deviations caused by FPC expansion and contraction, ensures uniform solder distribution on both sides of the NTC, solves the problem of cold solder joints, and improves product reliability.

Description

Technical Field

[0001] This utility model relates to the technical field of surface mount technology (SMT) with integrated circuit components, and in particular to an NTC thermistor solder paste mounting and positioning structure. Background Technology

[0002] NTC (Negative Temperature Coefficient) thermistors are commonly used for temperature monitoring in new energy products. For example... Figure 1 As shown, the traditional placement method uses a pick-and-place machine to position the NTC thermistor 2' according to the reference point 11' (MARK point) on FPC1' and complete the placement according to the preset placement coordinates. However, the NTC thermistor 2' is small in size, and the FPC1' in new energy products is prone to expansion and contraction due to environmental or processing factors, leading to deviations in the solder paste 3' printing. Since the pick-and-place machine relies solely on the reference point 11' of FPC1' for positioning, even if the pad 4' is accurately positioned, uneven solder distribution on both sides of the NTC thermistor 2' can still occur due to solder paste 3' printing deviations, easily resulting in cold solder joints and affecting product quality and reliability.

[0003] In view of this, this utility model addresses the many shortcomings and inconveniences caused by the imperfections in the existing NTC thermistor solder paste mounting and positioning structure design, and has been developed through in-depth conceiving, active research, improvement and trial production. Utility Model Content

[0004] The purpose of this invention is to overcome the problems of solder paste printing deviation and uneven solder amount on both sides of NTC thermistors that cause poor soldering in the prior art, and to provide an NTC thermistor solder paste mounting and positioning structure.

[0005] To achieve the above objectives, the solution of this utility model is: A solder paste mounting and positioning structure for NTC thermistors includes an FPC, a pick-and-place machine, an SMT stencil, and NTC thermistors. The FPC has at least two reference points, and each NTC thermistor has two NTC pads. The SMT stencil has two circular openings corresponding to the distance between the two NTC pads. The diameter of the circular openings is larger than the size of the electrodes of the corresponding NTC thermistor. Solder paste is printed onto the NTC pads through the openings of the SMT stencil, forming two circular solder pastes on the NTC pads. The pick-and-place machine is equipped with a vision camera to identify the circular solder pastes. The vision camera uses the circular solder pastes as the mounting reference points for the NTC thermistors. The pick-and-place machine selects a nozzle corresponding to the size of the NTC thermistor, picks up the NTC thermistor, and mounts it onto the FPC, so that the two electrodes of the NTC thermistor correspond to the two circular solder pastes.

[0006] Furthermore, the placement machine's vision camera calculates the placement center coordinates of the NTC thermistor based on the position of the circular solder paste, and the placement center coordinates are the midpoint of the line connecting the centers of the two circular solder pastes.

[0007] Furthermore, the two circular solder pastes are symmetrically distributed along the length of the NTC thermistor.

[0008] Furthermore, the diameter of the circular solder paste is 1.5mm ± 0.1mm.

[0009] Furthermore, the FPC is provided with two reference points, and the two reference points are located in the diagonal area of ​​the NTC pads.

[0010] Furthermore, the vision camera is also used to identify reference points on the FPC, and the vision camera first identifies the reference points of the FPC and then identifies the circular solder paste as the mounting reference points for the NTC thermistor.

[0011] Furthermore, the pick-and-place machine selects a nozzle corresponding to the size of the NTC thermistor to pick up the NTC thermistor.

[0012] With the above structure, the NTC thermistor solder paste mounting and positioning structure of this utility model is designed with a circular opening through the SMT stencil, which facilitates solder paste printing and forming. Simultaneously, the pick-and-place machine adds NTC reference point recognition after the original FPC recognition reference point, that is, it identifies and then mounts the printed circular solder paste, placing the NTC thermistor between two circular solder pastes. Although there is a deviation between the printed circular solder paste and the NTC pads, it ensures the amount of solder on both sides of the NTC thermistor. Mounting the NTC thermistor between the two circular solder pastes ensures uniform solder on both sides of the NTC thermistor, fundamentally solving the problem of cold solder joints and improving product yield and reliability. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the existing NTC thermistor solder paste being soldered onto an FPC.

[0014] Figure 2 This is a schematic diagram of the NTC thermistor solder paste being soldered onto an FPC according to this utility model.

[0015] Label Explanation: 1. FPC; 11. Base point; 12. NTC pad; 2. NTC thermistor; 3. Circular solder paste. Detailed Implementation

[0016] To further explain the technical solution of this utility model, the following detailed description is provided through specific embodiments.

[0017] like Figure 2As shown, this utility model discloses an NTC thermistor solder paste mounting and positioning structure, which includes an FPC1, a pick-and-place machine, an SMT stencil, and an NTC thermistor 2. The FPC1 has at least two reference points 11, and the FPC1 has two NTC pads 12 corresponding to each NTC thermistor 2. The SMT stencil has two circular openings corresponding to the distance between the two NTC pads 12. The diameter of the circular openings is larger than the size of the electrodes of the corresponding NTC thermistor 2. Solder paste is printed onto the NTC pads 12 through the openings of the SMT stencil, forming two circular solder pastes 3 on the NTC pads 12. The pick-and-place machine is equipped with a vision camera for identifying the circular solder pastes 3. The vision camera uses the circular solder pastes 3 as the mounting reference points for the NTC thermistors 2. The pick-and-place machine mounts the NTC thermistors 2 using the circular solder pastes 3 as reference points, so that the electrodes of the NTC thermistors 2 are precisely aligned with the circular solder pastes. Reference point 11 refers to the positioning mark printed on FPC1, which can be formed by metal etching or ink printing, and is used to establish the initial coordinate system of the pick-and-place machine. The circular opening of the SMT stencil refers to the through-hole structure that matches the spacing of the solder pads. It can be made by laser cutting. The enlarged diameter design of the circular opening ensures that the solder paste coverage area is larger than the electrode contact surface. After the reference point 1 achieves the coarse positioning of the pick-and-place machine, the vision camera of the pick-and-place machine performs secondary positioning on the actual printed circular solder paste 3. Since the formed area of ​​the circular solder paste 3 after printing has clear geometric features, the vision camera can accurately identify its center coordinates. The pick-and-place machine determines the placement position of the NTC thermistor 2 based on the midpoint of the line connecting the centers of the two circular solder paste 3s, and selects the appropriate nozzle size according to the model of the NTC thermistor. When the NTC thermistor 2 is placed, its electrodes completely cover the area of ​​the circular solder paste 3, ensuring uniform solder distribution. This invention's placement machine employs a two-stage positioning mechanism, adding precise positioning of the circular solder paste 3 on top of coarse positioning, forming a closed-loop correction system. In existing technologies, theoretical deviations between the pad positions and placement coordinates directly lead to placement misalignment. This invention, however, uses the printed circular solder paste as a reference, ensuring the placement position dynamically matches the printed position of the circular solder paste, guaranteeing uniform solder paste distribution on both electrodes of the NTC thermistor. This invention effectively eliminates the impact of FPC1 deformation on placement accuracy, solves the problem of uneven solder distribution caused by solder paste position deviation, and uses a vision camera to dynamically capture the actual position of the printed circular solder paste 3 as a placement reference, ensuring complete overlap between the electrodes of the NTC thermistor 2 and the circular solder paste 3, avoiding cold solder joint defects, and significantly improving soldering reliability and product yield.

[0018] Preferably, the two circular solder pastes 3 are symmetrically distributed along the length of the NTC thermistor 2. The symmetrically distributed circular solder pastes 3 provide uniform support force to the NTC thermistor during the placement process, ensuring consistent contact pressure between the two electrodes of the NTC thermistor 2 and the two NTC pads 12. This results in more consistent solder wetting time and coverage for the two electrodes of the NTC thermistor 2, eliminating voids or cold solder joints caused by insufficient solder paste on one side or misalignment.

[0019] In this embodiment, the diameter of the circular solder paste 3 is 1.5mm ± 0.1mm.

[0020] like Figure 2 As shown in this embodiment, the FPC1 is provided with two reference points, and the two reference points are located in the diagonal area of ​​the NTC pad.

[0021] This invention optimizes the SMT stencil opening of the NTC thermistor 2 by designing it as a 1.5mm circular opening. The pick-and-place machine, after identifying the original reference point 11 of the FPC1, adds a reference point for identifying the printed circular solder paste 3. This allows for the identification and placement of the 1.5mm circular solder paste printed by the NTC thermistor, placing the NTC thermistor 2 between the two circular solder pastes 3. Although there is a deviation between the printed circular solder paste 3 and the NTC pad 12, it ensures sufficient solder on both sides of the NTC thermistor, thus solving the problem of cold solder joints in the NTC thermistor.

[0022] The above embodiments and figures are not intended to limit the product form and style of this utility model. Any appropriate changes or modifications made by those skilled in the art should be considered as not departing from the patent scope of this utility model.

Claims

1. A tin paste mounting positioning structure of an NTC thermistor, characterized by, include: The components include an FPC (Flexible Printed Circuit), a pick-and-place machine, an SMT stencil, and NTC thermistors. The FPC has at least two reference points. For each NTC thermistor, the FPC has two NTC pads. The SMT stencil has two circular openings corresponding to the distance between the two NTC pads. The diameter of each circular opening is larger than the size of the electrode of the corresponding NTC thermistor. Solder paste is printed onto the NTC pads through the openings in the SMT stencil, forming two circular solder pastes on each NTC pad. The pick-and-place machine has a vision camera to identify the circular solder pastes. The vision camera uses the circular solder pastes as the mounting reference points for the NTC thermistors. The pick-and-place machine picks up the NTC thermistors and mounts them onto the FPC, ensuring that the two electrodes of the NTC thermistors correspond to the two circular solder pastes.

2. The tin paste mounting positioning structure of the NTC thermistor according to claim 1, wherein: The placement machine's vision camera calculates the placement center coordinates of the NTC thermistor based on the position of the circular solder paste. The placement center coordinates are the midpoint of the line connecting the centers of the two circular solder pastes.

3. The tin paste mounting positioning structure of the NTC thermistor according to claim 1, wherein: The two circular solder pastes are symmetrically distributed along the length of the NTC thermistor.

4. The tin paste mounting positioning structure of the NTC thermistor according to claim 1, wherein: The diameter of the circular solder paste is 1.5mm ± 0.1mm.

5. The tin paste mounting positioning structure of the NTC thermistor according to claim 1, wherein: The FPC has two reference points, which are located in the diagonal area of ​​the NTC pads.

6. The solder paste mounting and positioning structure for an NTC thermistor as described in claim 1 or 5, characterized in that: The vision camera is also used to identify reference points on the FPC, and the vision camera first identifies the reference points of the FPC and then identifies the circular solder paste as the mounting reference points for the NTC thermistor.

7. The solder paste mounting and positioning structure for an NTC thermistor as described in claim 1, characterized in that: The pick-and-place machine selects a nozzle corresponding to the size of the NTC thermistor to pick up the NTC thermistor.

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