CN108447634B

CN108447634B - Surface-mounted thermistor assembly

Info

Publication number: CN108447634B
Application number: CN201810081333.XA
Authority: CN
Inventors: 王绍裘
Original assignee: KUNSHAN JUDA ELECTRONIC CO Ltd
Current assignee: KUNSHAN JUDA ELECTRONIC CO Ltd
Priority date: 2018-01-26
Filing date: 2018-01-26
Publication date: 2020-01-10
Anticipated expiration: 2038-01-26
Also published as: CN108447634A

Abstract

The invention discloses a surface-mounted thermistor component, which comprises a first chip, a second chip, a first pin and a second pin, wherein the first chip comprises a first PTC core material and two metal electrode layers attached to the upper surface and the lower surface of the first PTC core material, the second chip comprises a second PTC core material and two metal electrode layers attached to the upper surface and the lower surface of the second PTC core material, and the first chip and the second chip are stacked in layers, the first pin is connected with one metal electrode layer of the first chip and one metal electrode layer of the second chip, the second pin is connected with the other metal electrode layer of the first chip and the other metal electrode layer of the second chip, the second pin comprises a shared electrode which is stacked between the first chip and the second chip, whereby the first chip and the second chip form a parallel circuit, the first PTC core material comprises a conductive ceramic filler and carbon black, and the second PTC core material comprises carbon black. The invention can withstand the cycle life test of 30V/40A for 300 times without burning.

Description

Surface-mounted thermistor assembly

[ technical field ] A method for producing a semiconductor device

The present invention relates to a thermistor assembly, and more particularly, to a surface-mount thermistor assembly having high withstand voltage and low resistance characteristics.

[ background of the invention ]

Since the voltage of a single battery is low, such as Lead-Acid (Lead-Acid)2V, nickel-metal hydride (Ni-MH) and nickel-cadmium (Ni-Cd) batteries 1.2V, and Lithium Ion (Lithium Ion) batteries 3.7V, in many applications, when the voltage required by a load is higher than that of a single battery, a plurality of batteries are connected in series to supply power, so as to meet the requirement of increasing the voltage.

The battery can be connected with a Positive Temperature Coefficient (PTC) protection component in series to achieve overcurrent protection. The traditional PTC protection component still mainly uses a carbon black and polymer composite material system, and because the conductivity of the carbon black material is insufficient, the protection component consumes excessive energy, relatively limits the loadable current amount of the battery, and reduces the standby time of the battery, but the relative withstand voltage can meet the requirements due to the higher impedance of the battery. If the original carbon black material is replaced by the ceramic powder with lower resistance, it is expected that a low-resistance composite material can be developed, but the low-resistance characteristic of the composite material is insufficient relative to the voltage resistance. The conventional surface mount SMD protection device is limited by the original PCB process design, material selection and inherent structure, so that the withstand voltage thereof can only reach about 20V, and the conventional surface mount SMD protection device cannot meet the protection requirements thereof when the battery voltage continues to increase. In order to break through the traditional carbon black conductive electrode limit and the insufficient withstand voltage problem of the low-resistance ceramic material at one stroke, the invention is beneficial to improving the withstand voltage of the product and meeting the requirement of low resistance through material integration and new structure design.

[ summary of the invention ]

The invention aims to provide a surface-mounted thermistor component which has excellent low resistance and voltage resistance characteristics, can pass a cycle life test of 30V/40A for 300 cycles without burning, and effectively solves the problem that the low resistance and the high voltage resistance are not easy to be compatible at the same time.

The invention realizes the purpose through the following technical scheme: a surface mount thermistor assembly includes a first chip, a second chip, a first pin, and a second pin. The first chip comprises a first PTC core material and two metal electrode layers attached to the upper surface and the lower surface of the first PTC core material. The second chip comprises a second PTC core material and two metal electrode layers attached to the upper surface and the lower surface of the second PTC core material, and the first chip and the second chip are stacked in a layered mode. The first pin is connected with a metal electrode layer of the first chip and a metal electrode layer of the second chip. The second pin is connected with the other metal electrode layer of the first chip and the other metal electrode layer of the second chip. The second pin includes a shared electrode stacked between the first chip and the second chip, so that the first chip and the second chip form a parallel circuit. The first PTC core material comprises a conductive ceramic filler and carbon black, and the second PTC core material comprises carbon black. The surface-mounted thermistor assembly can withstand a 30V/40A cycle life test for 300 times without being burnt out. The conductive ceramic filler of the first PTC core material comprises tungsten carbide. The first PTC core material contains 30-45% by volume of tungsten carbide and 2-20% by volume of carbon black.

In one embodiment, the first lead includes a first horizontal portion and a second horizontal portion which are branched, and the first horizontal portion and the second horizontal portion are located on different planes, so as to connect a metal electrode layer of the first chip and a metal electrode layer of the second chip, respectively.

In one embodiment, the second lead includes a third horizontal portion as the common electrode.

In one embodiment, the first horizontal portion and the second horizontal portion have the same area.

In one embodiment, the first lead and the second lead further comprise a soldering portion for surface mounting.

In one embodiment, the first pin and the second pin are integrally formed.

In one embodiment, the thickness of the metal electrode layer is 50 to 90 μm.

Compared with the prior art, the surface mounting type thermistor assembly has the beneficial effects that: through the parallel design of a plurality of chips, the proper matching of the conductive ceramic filler and the carbon black and the optimization of the thickness of the metal electrode layer, the requirements of low resistance and high voltage resistance can be met simultaneously, so that the voltage resistance can reach more than 30V or 60V.

[ description of the drawings ]

FIG. 1 is a schematic side view of a surface-mount thermistor assembly according to an embodiment of the present invention;

FIG. 2 is an exploded view of a surface mount thermistor assembly according to an embodiment of the present invention;

fig. 3 is a schematic diagram of a first lead of a surface mount thermistor assembly according to another embodiment of the invention.

Description of reference numerals:

10 surface mounting type thermistor assembly

11 first chip

12 first pin

13 second pin

14 electrode connection part

15 vertical part

16 welding part

17 electrode connection part

18 vertical part

19 welding part

21 second chip

111 first PTC core material

112 metal electrode layer

211 second PTC core material

141 first horizontal part

142 second horizontal portion

[ detailed description ] embodiments

The invention will now be further described with reference to the accompanying drawings.

Fig. 1 shows a schematic view of a surface mount thermistor assembly 10 according to an embodiment of the present invention, and fig. 2 shows an exploded perspective view of the surface mount thermistor assembly 10. The surface mount thermistor assembly 10 includes a first chip 11, a second chip 21, a first lead 12, and a second lead 13 stacked in layers. In this embodiment, the first chip 11 has a sandwich structure including a PTC core 111 and metal electrode layers 112 attached to the upper and lower surfaces of the PTC core 111. Similarly, the second chip 21 is also a sandwich structure including a PTC core 211 and metal electrode layers 112 attached to the upper and lower surfaces of the PTC core 211. The first lead 12 and the second lead 13 are bent structures, wherein the bent structures are bent into a plurality of portions, or particularly include horizontal and vertical portions, but not limited thereto. Preferably, the first leads 12 or the second leads 13 are all integrally formed, that is, the whole of the first leads 12 or the second leads 13 is from the same metal electrode plate, and a plurality of comb-shaped electrodes including a plurality of first leads 12 and second leads 13 can be manufactured by stamping, and then combined with the first chip 11 and the second chip 21, and then bent and cut to form a plurality of surface mount thermistor assemblies 10. One metal electrode layer 112 in the first chip 11 and one metal electrode layer 112 in the second chip 21 are electrically connected to the first lead 12, and the other metal electrode layer 112 in the first chip 11 and the other metal electrode layer 112 in the second chip 21 are electrically connected to the second lead 13. In this embodiment, one end of the second lead 13 forms a horizontal portion, and is stacked between the first chip 11 and the second chip 21 above and below, and serves as a common electrode for the first chip 11 and the second chip 21, so that the first chip 11 and the second chip 21 form a parallel circuit.

In the present embodiment, the first lead 12 includes an electrode connecting portion 14, a vertical portion 15 and a soldering portion 16, wherein the electrode connecting portion 14 and the soldering portion 16 extend in a horizontal direction, and the vertical portion 15 extends in a vertical direction and connects the electrode connecting portion 14 and the soldering portion 16. The electrode connecting portion 14 connects one metal electrode layer 112 of the first chip 11 and one metal electrode layer 112 of the second chip 21, and the first bonding portion 16 serves as a surface mount bonding interface. In particular, in the present embodiment, the electrode connecting portion 14 includes a first horizontal portion 141 and a second horizontal portion 142 which are branched, and the first horizontal portion 141 and the second horizontal portion 142 are located at different levels. The first horizontal portion 141 includes two electrode strips disposed on two sides of the upper surface and physically contacts the upper surface of the first chip 11. The second horizontal portion 142 is offset from the first horizontal portion 141 in a front-to-back direction and physically contacts about a central portion of the lower surface of the second chip 21. The second horizontal portion 142 and the first horizontal portion 141 are formed by bending two cutting lines from the same plate (e.g., nickel plate). The first horizontal portion 141 and the second horizontal portion 142 have substantially the same area, that is, the area of the first horizontal portion 141 including the two electrode bars is approximately equal to the area of the second horizontal portion 142, thereby providing the same effective electrode area. In one embodiment, the width of each electrode stripe of the first horizontal portion 141 is about 0.75mm, and the width of the second horizontal portion 142 is about 1.5mm, so as to provide equivalent effective electrode areas of the upper and lower first chips 11 and the second chip 21.

The second lead 13 includes an electrode connecting portion 17, a vertical portion 18, and a soldering portion 19. The electrode connection portion 17 connects the other metal electrode layer 112 of the first chip 11 and the second chip 21 as a third horizontal portion, and the second vertical portion 18 connects the electrode connection portion 17 and the soldering portion 19. In particular, the electrode connection portion 17 physically contacts the metal electrode layers 112 on the opposite surfaces of the first chip 11 and the second chip 21, that is, the electrode connection portion 17 is stacked between the adjacent metal electrode layers 112 of the first chip 11 and the second chip 21, and serves as a common electrode of the first chip 11 and the second chip 21. The soldering portion 16 and the soldering portion 19 are bent inward such that the soldering portion 16 and the soldering portion 19 are located on the same plane as a soldering surface for surface mounting to a circuit board. In this embodiment, the welding portion 16 is bent inward from the vertical portion 15, and the welding portion 19 is bent inward from the vertical portion 18. The bending direction of the

welding portions

16 and 19 can be adjusted according to actual requirements, but is not limited thereto.

Referring to fig. 3, the first leads 12 may also be formed by making a cutting line in the center of the same plate, and then bending to form a first horizontal portion 141 and a second horizontal portion 142 with the same width and staggered back and forth, for example, with a width of 1.5mm, which may also provide the equivalent effective electrode area for the upper and lower first chips 11 and the second chip 21. Since the first horizontal portion 141 of fig. 3 is not divided into two electrode bars as in fig. 2, it has better strength and is simpler to manufacture.

In order to prevent the unexpected short circuit problem of the first leads 12 and the second leads 13, the surface mount type over current protection device 10 may be further coated with an insulating layer, which at least covers the first chip 11 and the second chip 21 and a portion of the first leads 12 and the second leads 13, particularly covers the electrode connecting portion 14 and the electrode connecting portion 17, but at least exposes the soldering portion 16 and the soldering portion 19 for surface mounting. The insulating layer may be selected from thermosetting polymers that must withstand the high temperatures of a subsequent reflow (reflow) process. Besides the insulation, the insulation layer can be selected from materials with heat dissipation characteristics to provide better heat dissipation effect for the first chip 11 and the second chip 21, so as to increase the holding current value. The thermal conductivity of the insulating layer can reach 1W/mK, 2W/mK or 4W/mK, depending on the requirement. The insulating layer can be manufactured by injection molding, spraying or coating with a heat conductive insulating sheet.

The PTC core materials 111 and 211 contain a crystalline high molecular polymer and a conductive filler interspersed therebetween. The crystalline high-molecular polymer is generally a polyolefin-based polymer, for example: polyethylene. The conductive filler is carbon black, metal or conductive ceramic powder. Carbon black is inexpensive, but has a high volume resistance. The metal and conductive ceramic powders have low bulk resistance values and are suitable for component miniaturization and low resistance applications. The particle size of the conductive filler is between 0.01 and 30 μm. The metal powder may be selected from nickel, cobalt, copper, iron, tin, lead, silver, gold, platinum or other metals and alloys thereof. The conductive ceramic powder in the conductive filler may be selected from metal carbides, such as: titanium carbide (TiC), carbide (WC), Vanadium Carbide (VC), zirconium carbide (ZrC), niobium carbide (NbC), tantalum carbide (TaC), molybdenum carbide (MoC), and hafnium carbide (HfC);or from metal borides, such as: titanium boride (TiB2) and Vanadium Boride (VB)₂) Zirconium boride (ZrB)₂) Niobium boride (NbB)₂) Molybdenum boride (MoB)₂) And hafnium boride (HfB)₂) (ii) a Or from metal nitrides, such as: zirconium nitride (ZrN). The conductive filler of the present invention can be selected from a mixture, an alloy, a solid solution or a core-shell formed by physical or chemical means of the aforementioned metal or conductive ceramic.

In general, the surface mount thermistor assembly 10 is fabricated by: (a) raw material treatment: since the original conductive powder particles have different sizes and the excessive powder size will decrease the reliability of the material, the most suitable particle size distribution and particle size can be selected by screening. Thereby improving the recovery of the assembly. (b) Blending the polymer and the conductive filler: by adjusting the material formula, the most appropriate material proportion is found, and different blending parameters are changed to observe the correlation between the material and the resistance. In addition, the glass transition temperature of the ceramic powder polymer blending system is set to be between 90 and 140 ℃, and the glass transition temperature of the high-temperature polymer blending system is set to be between 160 and 280 ℃. (c) And (3) material and metal foil laminating stage: by adjusting the rheological property of the material and the flow channel design of the ejection film head, the conductive polymer composite material with excellent thickness uniformity can be produced under the regulation and control of parameters such as equipment precision and the like. (d) And (3) assembling a finished product: and processing the plate after the pressing into a finished product, and carrying out a series of reliability and environment verification to manufacture the thermistor for the square battery.

In addition to the above embodiment comprising two chips, the present invention can also be applied to the case of connecting more chips in parallel. For example three chips in parallel. In the same way, the invention can manufacture the surface-mounted type overcurrent protection component containing more chips connected in parallel, thereby further reducing the overall resistance value.

The surface-mounted thermistor component 10 of the invention is used for carrying out voltage-resistant cycle life (cyclic life) test, the component passes the current exceeding the specification of the product instantly in a short time by utilizing a test machine, whether the structure of the test material is damaged under the condition of continuous and repeated actions can be tested, the component is burnt, the capability of protecting the product by the component can be simulated under the condition of abnormal current of the product of a customer, and the component reliability test is carried out.

The following test of the withstand voltage cycle life was performed for the surface mount type overcurrent protection component shown in fig. 1. The components are 2920 size, and the metal electrode layer on the surface of the PTC core material is 1oz copper foil, namely the thickness of the metal electrode layer is 35 mu m. The device to be tested is applied with 30V/40A to carry out cycle life test, and the resistance value after different trigger (trip) times or cycle times is measured. Table 1 shows a comparison of two different material formulations, one embodiment using a mixture of tungsten carbide (W) and carbon black (C) as the conductive filler for the first chip and a second embodiment using purely carbon black, without a conductive ceramic filler. The resistance values after different trigger (trip) times or cycle times are shown in Table 1, Ri is the initial resistance value of the device, R₁、R₁₀、R₅₀、R₁₀₀、R₂₀₀And R₃₀₀The resistance values after 1 cycle, 10 cycles, 50 cycles, 100 cycles, 200 cycles and 300 cycles are shown, respectively. Another embodiment would use a mixture of tungsten carbide and carbon black throughout the first and second chips. In contrast, the embodiment where W + C is selected as the conductive filler in the first PTC core material of the first chip and C is selected as the conductive filler in the second PTC core material of the second chip can pass the cycle life test 300 times without burning out, whereas the embodiment where W + C is used for all of the first chip and the second chip cannot pass the cycle life test 300 times. That is, one chip selects the mixture of the conductive ceramic filler and the carbon black as the conductive filler, and the other chip selects the carbon black as the conductive filler, so as to exhibit better voltage resistance. Therefore, the conductive filler selected for the chip can also influence the voltage resistance.

TABLE 1

In the structure shown in fig. 1, the thickness of the metal electrode layer selected for the surface mount type over-current protection device including two chips also has an influence on the voltage endurance. As shown in Table 2, both of the components were 2920 size components, and the same formulation of the mixture of tungsten carbide and carbon black was used, but the thicknesses of the metal electrode layers on the upper and lower surfaces were 1oz copper foil and 2oz copper foil, that is, 35 μm and 70 μm, respectively. The 1oz and 2oz examples were tested for cycle life of 30V/40A, where the resistance R of the 1oz example was tested for 200 cycles₂₀₀The test rate is obviously higher than that of the 2oz example, the 1oz example can not be burnt out through 300 times of cycle life tests, and the 2oz example can pass 300 times of cycle life tests without burning out. The thickness of the metal electrode layer cannot be too thin, preferably 50 to 90 μm, for example 60 μm, 70 μm or 80 μm.

TABLE 2

A cycle life test of 30V/40A was performed together with the surface mount type overcurrent protection device (double-layered PTC) including two chips shown in fig. 1 and the conventional surface mount type overcurrent protection device (single-layered PTC) including a single chip, and the test results are shown in table 3. Both components were 2920 size components, and the same formulation of tungsten carbide and carbon black mixture was used, and 2oz copper foil was also used for the thickness of the metal electrode layers on the upper and lower surfaces. As can be seen from the results in table 3, the single layer PTC embodiment fails to burn out after 50 cycles, and the dual layer PTC embodiment passes 300 cycles without burning out. It is evident that the dual layer PTC embodiment can significantly improve its voltage resistance characteristics over a single layer PTC.

TABLE 3

In the mixture of tungsten carbide and carbon black selected in the above embodiment, the volume percentage of tungsten carbide is 30 to 45%, or particularly 35% or 40%, and the volume percentage of carbon black is 2 to 20%, or particularly 5%, 10% or 15%.

Generally speaking, the conventional design can only withstand about 20V voltage after the cycle life test under different voltages, and the surface mount type over-current protection device of the present invention can withstand at least 30V, and can even further withstand 60V voltage of 40V or higher.

The invention develops the protective component material which can be suitable for the protective current of the square lithium ion battery with high voltage resistance, and the new generation of ceramic conductor and the polymer composite material are used for developing and applying the high voltage resistance, compared with the previous generation of carbon black system, under the condition of the same current, the invention can resist the voltage of more than 30V and provide higher holding current, therefore, the development in application is not limited to the application of low-voltage battery modules such as general notebook computers, can be extended to high voltage application end and the development of series-parallel batteries, such as energy storage batteries required by electric vehicles or power generation equipment, for performing appropriate over-current protection, in particular to environment-friendly vehicles such as electric vehicles, meanwhile, the product has a solution, so that the product can help a battery factory to develop high-capacity batteries and application, and the battery pack assembly has more choices so as to match and improve the development requirement of the whole industry.

While the technical content and the technical features of the invention have been disclosed, those skilled in the art can make various substitutions and modifications based on the teaching and the disclosure of the invention without departing from the spirit of the invention. Therefore, the protection scope of the present invention should not be limited to the embodiments shown, but should include various alternatives and modifications without departing from the invention and covered by the claims.

Claims

1. A surface-mount thermistor assembly characterized in that: the surface-mounted thermistor assembly can bear 30V/40A cycle life test for 300 times without burning out, and comprises

The chip comprises a plurality of first chips and a plurality of second chips which are stacked in a layered manner, wherein each first chip comprises a first PTC core material and two metal electrode layers attached to the upper surface and the lower surface of the first PTC core material;

a first pin connected to a metal electrode layer of the first chip and a metal electrode layer of the second chip; and

a second pin connected to the other metal electrode layer of the first chip and the other metal electrode layer of the second chip;

wherein the second pin comprises a shared electrode stacked between the first chip and the second chip, such that the first chip and the second chip form a parallel circuit;

wherein the first PTC core material comprises a conductive ceramic filler and carbon black, and the second PTC core material comprises carbon black but does not comprise a conductive ceramic filler, the thickness of the metal electrode layer is 35 μm; or the first PTC core material comprises conductive ceramic filler and carbon black, the second PTC core material comprises a mixture of the carbon black and the conductive ceramic filler, and the thickness of the metal electrode layer is 50-90 μm;

the conductive ceramic filler of the first PTC core material comprises tungsten carbide, the volume percentage of the tungsten carbide in the first PTC core material is 30-45%, and the volume percentage of the carbon black is 2-20%.

2. The surface-mount thermistor assembly according to claim 1, characterized in that: the first pin comprises a first horizontal part and a second horizontal part which are forked and are positioned on different horizontal planes, and the first horizontal part and the second horizontal part are respectively connected with a metal electrode layer of the first chip and a metal electrode layer of the second chip.

3. The surface-mount thermistor assembly according to claim 1, characterized in that: the second pin comprises a third horizontal part as the shared electrode.

4. The surface-mount thermistor assembly according to claim 2, characterized in that: the first horizontal portion and the second horizontal portion have the same area.

5. A surface-mount thermistor assembly according to claim 3, characterized in that: the first pin and the second pin further comprise a welding part for surface mounting.

6. The surface-mount thermistor assembly according to claim 1, characterized in that: the first pin and the second pin are both of an integrally formed structure.