Surface mount thermistor

Abstract

The utility model discloses a patch type thermistor, through setting up heat conduction element in the casing, and setting up the flow guide hole on the casing, heat conduction element installs on the chip, and the flow guide hole communicates heat conduction element with the outside world. When using, when the chip is triggered, and the heat of the chip is transmitted to the heat conduction element after the self-heating temperature rise, the heat conduction element again disperses the heat to the outside world through the flow guide hole, thereby realizing the accelerated dispersion of the heat of the chip, preventing the chip from being damaged by the self-heating too high, and simultaneously, when being applied to the overcurrent protection circuit, the accelerated dispersion of the heat of the chip through the heat conduction element and the flow guide hole makes the chip return to normal temperature faster after the self-heating, reduces the delay of the circuit recovery, and simultaneously, the bottom of the casing is arranged as a heat conduction seat, the heat conduction seat can guide the heat of the chip to the PCB board, the loss of the heat of the chip can be accelerated by the PCB board, thereby further protecting the chip, and preventing the chip from gathering too much heat.

Description

Technical Field

[0001] This utility model relates to the field of thermistor technology, and in particular to a surface mount thermistor. Background Technology

[0002] Existing surface-mount thermistors typically consist of a chip, electrodes, and a protective casing. The chip is encapsulated within the protective casing, and its two ends are connected to electrodes on the PCB board via electrodes penetrating the casing. The chip's resistance changes with temperature. Surface-mount PTC (Positive Temperature Coefficient) thermistors are commonly used for overcurrent protection in circuits. When the current exceeds the safe range, the excessive current flowing through the thermistor causes the PTC chip to heat up continuously, increasing its resistance and thus limiting the current and protecting the circuit.

[0003] Protective housings are used to protect thermistor chips from external environmental influences such as humidity, dust, or mechanical shock, thereby extending the thermistor's lifespan. Existing protective housings are typically made of materials with good insulation and heat resistance, such as epoxy resin or glass. However, these materials often have poor thermal conductivity, which can prevent the self-heat generated by the chip from dissipating, easily leading to overheating and damage. Furthermore, poor heat dissipation can cause delays in circuit recovery; even after the fault is cleared, the chip temperature remains high, the circuit current is still limited, and the circuit cannot quickly return to normal, resulting in a delayed recovery. Utility Model Content

[0004] The main purpose of this invention is to propose a surface-mount thermistor, which aims to solve the technical problem of poor heat dissipation caused by the chip of the existing surface-mount thermistor being sealed and encased in a protective shell with poor thermal conductivity.

[0005] To achieve the above objectives, the present invention proposes a surface-mount thermistor comprising: a chip and a housing, wherein a heat-conducting element is mounted on the chip; a through-hole is provided on the side wall or top wall of the housing; both the chip and the heat-conducting element are mounted inside the housing, and the through-hole connects the heat-conducting element to the outside.

[0006] Optionally, the thermally conductive element includes a base plate and a heat sink; the base plate is mounted on a first side of the chip; the heat sink is mounted on a second side of the base plate, and at least one contact surface of the heat sink is wholly or partially located within a flow guide hole.

[0007] Alternatively, the heat sink is zigzag-shaped to form several V-shaped grooves; the air guide holes are located within the space formed by the V-shaped grooves, and both sidewalls of the V-shaped grooves are partially located within the air guide holes.

[0008] Optionally, a fifth placement slot is provided inside the housing, the shape of which matches the heat-conducting element; the heat-conducting element is placed inside the fifth placement slot; and the flow guide hole communicates with the fifth placement slot.

[0009] Alternatively, a heat-conducting base is provided at the bottom of the housing, the chip is mounted on top of the heat-conducting base, and a heat-conducting element is mounted on top of the chip.

[0010] Optionally, the bottom and top surfaces of the heat-conducting base form a first heat-conducting surface and a second heat-conducting surface, respectively; the width of the first heat-conducting surface is greater than that of the second heat-conducting surface; the first heat-conducting surface is used to contact the PCB board; and a chip is mounted on the second heat-conducting surface.

[0011] Optionally, a limiting groove is provided on the side wall of the heat-conducting base; the limiting groove is an arc-shaped groove, and the cross-section of the limiting groove is an arc; the bottom of the housing has a first placement groove, and limiting protrusions matching the shape of the limiting groove are formed on both sides of the first placement groove; the limiting protrusions are located in the limiting groove.

[0012] Optionally, the sidewall of the heat-conducting base is connected to the first heat-conducting surface and the second heat-conducting surface via an arc surface.

[0013] Optionally, the housing may also have a second, a third, and a fourth placement slot connected in sequence; a chip is installed in the third placement slot; a first electrode is installed in the second placement slot, with the two opposite sides of the first electrode abutting against the heat-conducting base and the chip respectively; a second electrode is installed in the fourth placement slot, with the two opposite sides of the second electrode abutting against the chip and the heat-conducting element respectively.

[0014] 1) The surface-mount thermistor of this utility model incorporates a heat-conducting element within a housing and a flow-guiding hole on the housing. The heat-conducting element is mounted on a chip, and the flow-guiding hole connects the heat-conducting element to the outside environment. During use, when the chip is triggered and self-heats, the heat from the chip is transferred to the heat-conducting element, which then dissipates the heat to the outside environment through the flow-guiding hole. This accelerates the dissipation of heat from the chip, preventing damage from excessive self-heating. Furthermore, when applied to overcurrent protection circuits, the accelerated heat dissipation from the chip via the heat-conducting element and flow-guiding hole allows the chip to recover to room temperature more quickly after self-heating, resulting in faster circuit recovery and reduced recovery delay.

[0015] 2) This utility model also sets the bottom of the shell as a heat-conducting seat. The first heat-conducting surface and the second heat-conducting surface of the heat-conducting seat are respectively connected to the PCB board and the chip. The PCB board is usually equipped with a cooling device. By introducing the heat of the chip to the PCB board, the PCB board can be used to accelerate the dissipation of the chip's heat, thereby further protecting the chip and preventing excessive heat accumulation in the chip. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the structure of this utility model; Figure 2 This is an exploded view of the present invention; Figure 3 This is a half-sectional schematic diagram of the present invention; Figure 4 This is a schematic diagram of the three-dimensional structure of the shell; Figure 5 This is a three-dimensional sectional view of the shell; Figure 6 This is a top view of the shell. Figure 7 for Figure 6 Cross-sectional view of BB; Figure 8 for Figure 6 Schematic diagram of the cross section of AA; Figure 9 This is a schematic diagram of the heat-conducting base. Figure 10 This is a schematic diagram of the thermal conductive element.

[0018] Explanation of icon numbers: 1. Heat-conducting base; 11. First heat-conducting surface; 12. Second heat-conducting surface; 13. Limiting groove; 2. First electrode; 3. Chip; 4. Second electrode; 5. Heat-conducting element; 51. Base plate; 52. Heat sink; 53. V-groove; 6. Housing; 61. First placement groove; 62. Second placement groove; 63. Third placement groove; 64. Fourth placement groove; 65. Fifth placement groove; 66. Guide hole.

[0019] The realization of the purpose, functional features and advantages of this utility model will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0020] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0021] It should be noted that if the embodiments of this utility model involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0022] Furthermore, the use of terms such as "first" and "second" in this utility model is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the term "and / or" throughout the text includes three solutions; taking A and / or B as an example, it includes technical solution A, technical solution B, and a technical solution that simultaneously satisfies A and B. Furthermore, the technical solutions of various embodiments can be combined with each other, provided that they are feasible for those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this utility model.

[0023] This invention proposes a surface-mount thermistor.

[0024] In the embodiments of this utility model, such as Figures 1-10 The surface mount thermistor shown includes a chip 3, a thermally conductive element 5, and a housing 6. The thermally conductive element 5 is mounted on the chip 3. A through-hole 66 is provided on the side wall or top wall of the housing 6. Both the chip 3 and the thermally conductive element 5 are installed inside the housing 6, and the through-hole 66 connects the thermally conductive element 5 to the outside.

[0025] Specifically, a heat-conducting element 5 is installed inside the housing 6, and a flow-guiding hole 66 is opened on the housing 6. The heat-conducting element 5 is mounted on the chip 3, and the flow-guiding hole 66 connects the heat-conducting element 5 to the outside. In use, when the chip 3 is triggered and heats up on its own, the heat from the chip 3 is transferred to the heat-conducting element 5, and the heat-conducting element 5 then dissipates the heat to the outside through the flow-guiding hole 66, thereby accelerating the dissipation of heat from the chip and preventing the chip 3 from being damaged due to excessive self-heating. At the same time, when applied to overcurrent protection circuits, the accelerated dissipation of heat from the chip 3 by the heat-conducting element 5 and the flow-guiding hole 66 allows the chip 3 to recover to room temperature more quickly after self-heating, thus enabling the circuit to recover faster and reducing the circuit recovery delay.

[0026] Optionally, the heat-conducting element 5 includes a base plate 51 and a heat sink 52; the base plate 51 is mounted on the first side of the chip 3; the heat sink 52 is mounted on the second side of the base plate 51, and at least one contact surface of the heat sink 52 is wholly or partially located within the flow guide hole 66.

[0027] Specifically, the heat-conducting element 5 is made of a material with high thermal conductivity, such as copper, and covers the top surface of the chip 3 over a large area through the base plate 51, so that the heat of the chip 3 can be transferred to the heat sink 52 with higher efficiency. At least one contact surface of the heat sink 52 is located inside the guide hole 66, which is connected to the outside. When the chip 3 is working, it generates heat, making its temperature higher than the external environment. The chip 3 causes the temperature of the heat sink 52 to rise, and the heat sink 52 radiates heat to the outside through the guide hole 66 for heat dissipation. Furthermore, through the radiative heat dissipation of the contact surface of the heat-conducting element 5 within the guide hole 66, the environment in which the chip 3 is located remains a sealed environment covered by the casing 6.

[0028] In this embodiment, the first side of the base plate 51 is the bottom end surface, and the second side of the base plate 51 is the top end surface.

[0029] In some other embodiments, the first side of the base plate 51 is the bottom end face, the second side of the base plate 51 can be the side face, the heat sink 52 can be disposed on both sides of the base plate 51, and the position of the guide hole 66 needs to be adapted to the position of the heat sink 52.

[0030] In this embodiment, the housing 6 is made of epoxy resin. The thermistor in this embodiment is formed by stacking the heat-conducting base 1, the first electrode 2, the chip 3, the second electrode 4 and the heat-conducting element 5 in a molding mold from bottom to top, and then injecting liquid epoxy resin into the mold. After the epoxy resin solidifies, the housing 6 is formed. The housing 6 bonds the heat-conducting base 1, the first electrode 2, the chip 3, the second electrode 4 and the heat-conducting element 5 into a whole.

[0031] Specifically, a molding die refers to a die with an internal cavity that has the same structure as the shell.

[0032] Optional, such as Figure 7 and Figure 10 As shown, the heat sink 52 is bent so that it forms several V-shaped grooves 53; the guide hole 66 is opened in the V-shaped groove 53, and both sidewalls of the V-shaped groove 53 are partially located in the guide hole 66.

[0033] Specifically, the base plate 51 has the same width and length as the chip 3, so that the base plate 51 can cover the entire top surface of the chip 3, ensuring that the heat-conducting element 5 has a larger heat conduction area; the heat sink 52 is zigzag-shaped, forming a multi-segmented zigzag plate (e.g., Figure 10As shown in the diagram, the top surface of the heat sink 52 has several V-grooves 53, which can be used to place the filling mold. The filling mold is placed in the V-grooves 53 so that when the epoxy resin fills the space inside the molding mold, the position where the filling mold is located lacks epoxy resin. After the housing 6 is formed and solidified, the filling mold is removed from the housing 6, and the position where the filling mold is located inside the housing 6 forms the guide hole 66. The tortuous arrangement of the heat sink 52 not only serves to form the V-grooves 53 to support the filling mold, but also forms several triangular areas on the lower surface of the heat sink 52. When the housing 6 is formed, the liquid epoxy resin can also penetrate into these triangular areas, thereby balancing the stress on the upper and lower surfaces of the heat sink 52; so that when the epoxy resin solidifies, the upper and lower surfaces of the heat sink 52 have the same force for balance. This prevents the heat sink 52 from not adhering firmly to the housing 6 due to unilateral stress during the molding of the housing 6, and prevents cracks, further ensuring the sealing of the chip 3 inside the housing 6.

[0034] Specifically, the filling mold is preferably a rod-shaped object with the same cross-sectional shape as the guide hole 66. In order to ensure that the filling mold can be easily removed after the shell 6 solidifies, the surface of the filling mold can be coated with powder or machine oil or other materials that are easy to fall off the surface of the filling mold before molding. This will make the inner wall of the guide hole 66 stick to the coating material on the surface of the filling mold after the shell 6 solidifies, and the filling mold can be easily removed from the guide hole 66.

[0035] In other embodiments, a filling mold may also be placed in several triangular areas formed on the lower surface of the heat sink 52, thereby forming a flow guide hole 66 on the lower surface of the heat sink 52, so that a portion of the contact surface of the lower surface of the heat sink 52 is located within the flow guide hole 66, thereby giving the heat sink 52 a larger heat dissipation area.

[0036] In this embodiment, the heat-conducting element 5 is disposed on the top surface of the chip 3, and the second electrode 4 is located between the heat-conducting element 5 and the chip 3; both the first electrode 2 and the second electrode 4 are made of copper, which has both electrical conductivity and excellent thermal conductivity. Even though the second electrode 4 is disposed between the chip 3 and the heat-conducting element 5, it does not affect the heat transfer between the heat-conducting element 5 and the chip 3.

[0037] In other embodiments, the base plate 51 of the heat-conducting element 5 may also be disposed on the side wall of the chip 3 where it does not interfere with the first electrode 2 and the second electrode 4, and the heat sink 52 is still disposed on the side of the base plate 51 away from the chip 3. In this case, the flow guide hole 66 vertically penetrates the top and bottom surfaces of the housing 6, so that at least one contact surface of the heat sink 51 is entirely or partially located in the flow guide hole 66.

[0038] Optionally, a fifth placement groove 65 is provided inside the housing 6, the shape of which matches the heat-conducting element 5; the heat-conducting element 5 is placed inside the fifth placement groove 65; the flow guide hole 66 is connected to the fifth placement groove 65.

[0039] In this embodiment, as Figures 1-3 As shown, a heat-conducting base 1 is provided at the bottom of the housing 6, the chip 3 is mounted on the top of the heat-conducting base 1, and the heat-conducting element 5 is mounted on the top of the chip 3.

[0040] When some PCB boards with thermistors are equipped with cooling or heat dissipation components, the entire thermistor is mounted on the PCB board through a ceramic heat-conducting base 1. The first electrode 2 and the second electrode 4 are electrically connected to the pins of the PCB board. The heat-conducting base 1 is in direct contact with the PCB board and senses the heat changes of the chip 3 and the PCB board through the heat-conducting base 1. When the overcurrent protection circuit is overloaded, the temperature of the chip 3 rises and the current is interrupted to protect the circuit. At this time, the temperature of the chip 3 is higher than that of the PCB board. The heat-conducting base 1 exchanges the temperature of the chip 3 with the heat of the PCB board, so that the chip 3 dissipates heat through the PCB board. Thus, the PCB board can be efficiently utilized for cooling through the heat-conducting base 1.

[0041] In this embodiment, the heat-conducting base 1 is preferably made of ceramic. Ceramic has excellent thermal conductivity and insulation properties, so that even if the heat-conducting base 1 is in contact with the PCB board, the chip 3 is still electrically connected to the PCB board through the first electrode 2 and the second electrode 4, thus ensuring the stability of the circuit.

[0042] Optionally, the bottom and top surfaces of the heat-conducting base 1 form a first heat-conducting surface 11 and a second heat-conducting surface 12, respectively; the width of the first heat-conducting surface 11 is greater than that of the second heat-conducting surface 12; the first heat-conducting surface 11 is used to contact the PCB board; and the chip 3 is mounted on the second heat-conducting surface 12.

[0043] Specifically, the second heat-conducting surface 12 has the same length and width as the chip 3, ensuring sufficient heat conduction area. The width of the first heat-conducting surface 11 is greater than that of the second heat-conducting surface 12, resulting in a larger contact area between the second heat-conducting surface 11 and the PCB board, enabling more efficient heat dissipation from the chip 3 using the PCB board. Simultaneously, the greater width of the first heat-conducting surface 11 compared to the second heat-conducting surface 12 results in a larger base for the heat-conducting base 1 during molding, leading to more stable installation and reducing the likelihood of tipping or tilting. Furthermore, when injecting liquid epoxy resin into the molding die, no additional support is needed for the chip 3, as the heat-conducting base 1 provides stable support.

[0044] Optionally, a limiting groove 13 is provided on the side wall of the heat-conducting base 1; the limiting groove 13 is an arc-shaped groove, and the cross section of the limiting groove 13 is an arc; the bottom of the housing 6 has a first placement groove 61, and limiting protrusions matching the shape of the limiting groove 13 are formed on both sides of the first placement groove 61; the limiting protrusions are located in the limiting groove 13.

[0045] Specifically, the limiting groove 13 allows more epoxy resin to be poured into the limiting groove 13 during the molding of the housing 6, thereby increasing the contact area between the epoxy resin and the heat-conducting base 1. This results in better adhesion between the housing 6 and the heat-conducting base 1, making it less prone to loosening. The cross-section of the limiting groove 13 is an arc, meaning that the opening size of the limiting groove 13 is smaller than its diameter. That is, the area with the largest radius of the limiting protrusion is located within the limiting groove 13, thus creating a locking connection between the limiting protrusion and the limiting groove 13, further preventing the connection between the heat-conducting base 1 and the housing 6 from loosening.

[0046] Preferably, the sidewall of the heat-conducting base 1 is connected to the first heat-conducting surface 11 and the second heat-conducting surface 12 via an arc surface.

[0047] Specifically, the arc-shaped connection can effectively prevent the corners at the connection between the side wall of the heat-conducting base 1 and the first heat-conducting surface 11 and the second heat-conducting surface 12 from being too sharp, and at the same time, it can increase the contact area between the side wall of the heat-conducting base 1 and the housing 6.

[0048] In this embodiment, as Figure 3-8 As shown, the housing 6 also has a second placement slot 62, a third placement slot 63 and a fourth placement slot 64 connected in sequence; the chip 3 is installed in the third placement slot 63; the first electrode 2 is installed in the second placement slot 62, and the two opposite sides of the first electrode 2 abut against the heat-conducting base 1 and the chip 3 respectively; the second electrode 4 is installed in the fourth placement slot 64; the two opposite sides of the second electrode 4 abut against the chip 3 and the heat-conducting element 5 respectively.

[0049] Specifically, the first placement slot 61, the second placement slot 62, the third placement slot 63, the fourth placement slot 64, and the fifth placement slot 65 in the inner cavity of the housing 6 are connected sequentially from bottom to top, so that only the sidewalls of the chip 3 are covered by the housing 5 made of epoxy resin material with poor thermal conductivity. The top surface of the chip 3 can dissipate heat through the heat-conducting element 5 and the flow guide hole 66, and the bottom surface of the chip 3 can dissipate heat through the heat-conducting base 1 and the PCB board. Compared with the existing surface-mount PTC thermistor, the chip 3 of this utility model has a better heat dissipation effect, is less prone to heat accumulation, and has a lower circuit recovery delay after overcurrent protection is triggered.

[0050] The above description is only a preferred embodiment of the present utility model and does not limit the patent scope of the present utility model. All equivalent structural transformations made under the inventive concept of the present utility model using the contents of the present utility model specification and drawings, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present utility model.

Claims

1. A surface-mount thermistor, characterized in that, include: Chip (3), on which a heat-conducting element (5) is mounted; The housing (6) has a through-hole (66) on its side wall or top wall; the chip (3) and the heat-conducting element (5) are both installed inside the housing (6), and the through-hole (66) connects the heat-conducting element (5) to the outside. The heat-conducting element (5) includes a base plate (51) and a heat sink (52); the base plate (51) is mounted on the first side of the chip (3); The heat sink (52) is mounted on the second side of the base plate (51), and at least one contact surface of the heat sink (52) is located entirely or partially within the guide hole (66); The heat sink (52) is bent so that the heat sink (52) forms a number of V-shaped grooves (53). The guide hole (66) is located within the space formed by the V-groove (53), and both sidewalls of the V-groove (53) are partially located within the guide hole (66).

2. The surface mount thermistor as described in claim 1, characterized in that, The housing (6) has a fifth placement groove (65) inside, the shape of which matches the heat-conducting element (5); the heat-conducting element (5) is placed inside the fifth placement groove (65); The flow guide hole (66) is connected to the fifth placement groove (65).

3. The surface mount thermistor as described in claim 1, characterized in that, The bottom of the housing (6) is provided with a heat-conducting base (1), the chip (3) is mounted on the top of the heat-conducting base (1), and the heat-conducting element (5) is mounted on the top of the chip (3).

4. The surface mount thermistor as described in claim 3, characterized in that, The bottom and top surfaces of the heat-conducting base (1) form a first heat-conducting surface (11) and a second heat-conducting surface (12), respectively; the width of the first heat-conducting surface (11) is greater than that of the second heat-conducting surface (12). The first heat-conducting surface (11) is used to contact the PCB board; A chip (3) is mounted on the second heat-conducting surface (12).

5. The surface mount thermistor as described in claim 4, characterized in that, A limiting groove (13) is provided on the side wall of the heat-conducting seat (1); The limiting groove (13) is an arc-shaped groove, and the cross section of the limiting groove (13) is an arc. The bottom of the housing (6) has a first placement groove (61), and the two sides of the first placement groove (61) have limiting protrusions that match the shape of the limiting groove (13). The limiting protrusion is located within the limiting groove (13).

6. The surface mount thermistor as described in claim 4, characterized in that, The sidewall of the heat-conducting seat (1) is connected to the first heat-conducting surface (11) and the second heat-conducting surface (12) through an arc surface.

7. The surface mount thermistor as described in claim 1, characterized in that, The housing (6) is also provided with a second placement slot (62), a third placement slot (63) and a fourth placement slot (64) connected in sequence. The chip (3) is installed in the third placement slot (63); The second placement slot (62) is equipped with a first electrode (2), and the two opposite sides of the first electrode (2) abut against the heat-conducting base (1) and the chip (3) respectively; The second electrode (4) is installed in the fourth placement slot (64); the two opposite sides of the second electrode (4) abut against the chip (3) and the heat-conducting element (5) respectively.

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