JP2008177435A - Ptc device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a PTC device in which the effect of the curvature of a clad plate on a PTC element can be reduced. <P>SOLUTION: A PTC device 1 includes a PTC element 2. A terminal electrode 3A is fixed onto the lower surface of the PTC element 2. A terminal electrode 3B is fixed onto the upper surface of the PTC element 2. The terminal electrodes 3A and 3B are formed of Ni and the like. The terminal electrode 3A is bonded with solder S<SB>1</SB>to a clad plate 4 constituted by laminating an Ni plate 4a and an Al plate 4b. The solder S<SB>1</SB>is provided on a region corresponding to a portion other than the edge of the terminal electrode 3A between the terminal electrode 3A and the clad plate 4. That is, a void 6 constituting a buffer portion for reducing the deformation of the PTC element 2 caused by the curvature of the clad plate 4 is formed in a region corresponding to the edge of the terminal electrode 3A between the terminal electrode 3A and the clad plate 4. The terminal electrode 3B is bonded to the Ni plate 5 with solder S<SB>2</SB>. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a PTC (Positive Temperature Coefficient) element having a characteristic that a resistance value increases as a temperature rises.

As a conventional PTC element, for example, as described in Patent Document 1, a metal plate (Cu foil) for forming a terminal electrode is bonded to the surface of a PTC element body having a positive resistance temperature characteristic. It has been.
JP-A-5-9921

  By the way, in an electronic device including a PTC element, the PTC element may be mounted on a clad plate formed by stacking two kinds of metals, for example, in order to reduce the size and cost. However, in such a clad plate mounting type PTC element, for example, when heat is applied in a reflow process or a test, the clad plate warps to the PTC element body side due to a difference in linear expansion of two kinds of metals constituting the clad plate, The PTC element body may be deformed. When the deformation of the PTC element body due to the warping of the clad substrate is repeated, the PTC element body is damaged and the characteristics of the PTC element are deteriorated.

  An object of the present invention is to provide a PTC element capable of reducing the influence on the PTC element body due to the warping of the clad plate.

  The PTC element of the present invention is bonded to a PTC element body, a first terminal electrode and a second terminal electrode fixed to the PTC element body so as to face each other with the PTC element element sandwiched therebetween, and a plurality of types. And a metal plate joined to the second terminal electrode, and in a region corresponding to the edge of the first terminal electrode between the first terminal electrode and the clad plate, A buffer portion for reducing deformation of the PTC element body due to warpage of the clad plate is provided.

  As described above, in the PTC element of the present invention, since the first terminal electrode is joined to the clad plate formed by superimposing a plurality of kinds of metals, for example, when heat is applied by a reflow process or a test, the clad plate The clad plate may warp to the PTC element body side due to the difference in linear expansion of a plurality of types of metals. At this time, since the buffer portion is provided in the region corresponding to the edge of the first terminal electrode between the first terminal electrode and the clad plate, even if the clad plate warps to the PTC element body side, The deformation of the PTC element body is mitigated by the buffer portion. Thereby, the influence which the curvature of a clad board has on a PTC element body can be reduced.

  Preferably, a gap constituting the buffer portion is formed in a region corresponding to the edge portion of the first terminal electrode between the first terminal electrode and the clad plate. In this case, by applying heat to the PTC element, even if the clad plate warps to the PTC element body side, the clad plate can smoothly pass through the gap (space) formed between the first terminal electrode and the clad plate. It becomes possible to move. For this reason, since the force applied to the PTC element body due to the warp of the clad plate is sufficiently reduced, the deformation of the PTC element body due to the warp of the clad plate can be sufficiently mitigated.

  Further, a coating resin portion constituting a buffer portion may be provided in a region corresponding to the edge portion of the first terminal electrode between the first terminal electrode and the clad plate. In this case, when heat is applied to the PTC element, the resin that forms the coating resin portion provided between the first terminal electrode and the clad plate is softened by the heat. For this reason, by applying heat to the PTC element, the clad plate can move in the coating resin portion even if the clad plate is warped toward the PTC element body. For this reason, since the force added to a PTC element body by the curvature of a clad board is reduced, the deformation | transformation of the PTC element body by the curvature of a clad board can be relieved. Further, by providing such a coating resin portion, the bonding strength between the first terminal electrode and the clad plate can be increased.

  Preferably, the clad plate is joined to the first terminal electrode by solder, and the solder is in a region corresponding to a portion excluding the edge of the first terminal electrode between the first terminal electrode and the clad plate. Is provided. Thus, even when the clad plate and the first terminal electrode are joined by solder, the buffer portion is reliably formed in the region corresponding to the edge of the first terminal electrode between the first terminal electrode and the clad plate. Can do.

  The clad plate is welded to the first terminal electrode via a metal spacer, and the metal spacer corresponds to a portion excluding the edge of the first terminal electrode between the first terminal electrode and the clad plate. It may be interposed in the region. Thereby, even when the clad plate and the first terminal electrode are joined by welding, the buffer portion can be reliably formed in the region corresponding to the edge of the first terminal electrode between the first terminal electrode and the clad plate. it can.

  According to the present invention, the influence on the PTC element body due to the warping of the clad substrate can be reduced. Thereby, it becomes possible to prevent the deterioration of the resistance temperature characteristic of the PTC element.

  Hereinafter, preferred embodiments of a PTC element according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a sectional view showing a first embodiment of the PTC element according to the present invention, and FIG. 2 is a plan view of the PTC element shown in FIG. In each figure, the PTC element 1 of this embodiment is a polymer PTC (P-PTC) element used for protecting a secondary battery pack of a mobile phone, for example.

  The PTC element 1 includes a rectangular parallelepiped PTC element body 2 in which a conductive filler is dispersed in a crystalline polymer resin, for example. The PTC element body 2 has a positive resistance-temperature characteristic, that is, a characteristic that electric resistance increases as the temperature rises. Examples of the crystalline polymer resin include thermoplastic resins such as linear low-density polyethylene resins, but thermosetting resins may also be used. Ni powder or the like is used as the conductive filler. The dimensions of the PTC element body 2 are, for example, about 3.0 mm long × 4.0 mm wide. Further, the thickness of the PTC element body 2 is, for example, about 0.4 to 0.5 mm.

  A terminal electrode 3 A is fixed to the lower surface of the PTC element body 2, and a terminal electrode 3 B is fixed to the upper surface of the PTC element body 2. That is, the terminal electrodes 3A and 3B are opposed to each other with the PTC element body 2 interposed therebetween. The terminal electrodes 3A and 3B are made of Ni (nickel), Ni alloy or the like. The thickness of the terminal electrodes 3A and 3B is, for example, about 20 to 200 μm.

Terminal electrodes 3A is joined to the clad plate 4 with solder S _1. The clad plate 4 is a single plate obtained by superimposing a Ni plate (nickel plate) 4a and an Al plate (aluminum plate) 4b by rolling or the like. The terminal electrode 3 </ b> A is bonded to the Ni plate 4 a of the clad plate 4. The Al plate 4b of the clad plate 4 is welded to a battery cell (not shown).

At this time, the solder S ₁ is provided in a region corresponding to the portion except for the entire edge of the terminal electrodes 3A between the terminal electrodes 3A and the cladding plate 4. As a result, a gap 6 is formed in a region corresponding to the entire edge of the terminal electrode 3A between the terminal electrode 3A and the clad plate 4. The gap 6 constitutes a buffer portion for relaxing deformation of the PTC element body 2 due to warpage of the clad plate 4. Incidentally, the solder _{S 1} thickness, i.e. the distance between the terminal electrodes 3A and the cladding plate 4, for example, is preferably about 50 to 150 [mu] m. The length between the width W, i.e. the edge of the edge and the solder _{S 1} terminal electrode 3A of the gap 6 (buffer portion) is, for example, is preferably about 0.3 to 1.5 mm.

Terminal electrodes 3B are joined with solder _{S 2} to Ni plate 5. The Ni plate 5 is welded to a protection circuit board (not shown). Solder S ₂ is in correspondence with the solder S ₁ described above, is provided in a region corresponding to the portion excluding the entire edge of the terminal electrode 3B between the terminal electrodes 3B and Ni plate 5. Thereby, the space | gap 7 will be formed in the area | region corresponding to the whole edge part of the terminal electrode 3B between the terminal electrode 3B and the Ni plate 5. FIG.

  Next, a method for manufacturing the PTC element 1 configured as described above will be described with reference to FIG.

  First, the PTC element body 2 is produced. Specifically, a conductive filler such as Ni powder and a crystalline polymer such as polyethylene resin are prepared, and these are kneaded to form a block. And after heating and pressurizing (thermocompression bonding) this block to a disk shape, it cuts into chip size, thereby obtaining a PTC element body 2 as shown in FIG.

  Subsequently, each Ni foil is thermocompression bonded in a state where the PTC element body 2 is sandwiched from above and below by two Ni foils, whereby the terminal electrode 3A, 3B is formed. Thereby, the element main body 8 which consists of the PTC element | base_body 2 and terminal electrode 3A, 3B is obtained. At this time, for example, the thermocompression treatment is performed under the conditions of a heating temperature of 150 ° C., a pressing time of 1 minute, and a pressing force of 1 ton. Then, the element body 8 is punched into a predetermined dimension as shown in FIG.

Subsequently, as shown in FIG. 3 (d), the solder S ₁ is printed on a predetermined area of the Ni plate 4 a of the clad plate 4, and the solder S ₂ is printed on a predetermined area of the Ni plate 5. At this time, as the solders S ₁ and S _{2 to} be used, it is necessary to select a solder (for example, Eco Solder M705 manufactured by Senju Metal Industry Co., Ltd.) that can maintain the printed shape when melted in a reflow process (described later).

Subsequently, as shown in FIG. 3E, the clad plate 4 is joined to the terminal electrode 3A and the Ni plate 5 is joined to the terminal electrode 3B by reflow soldering. Specifically, overlapping element body 8 on the cladding plate 4 solder S ₁ is printed, placed in a reflow furnace in a further state overlaid on the Ni plate 5 an element body 8 in which the solder S ₂ is printed Then, the solders S ₁ and S ₂ are heated and melted. The heating temperature at this time is about 230 ° C., for example. Thereafter, by solidifying the solders S ₁ and S ₂ , the terminal electrode 3A and the clad plate 4 are joined by the solder S ₁ , and the terminal electrode 3B and the Ni plate 5 are joined by the solder S ₂ . Thus, the above-described PTC element 1 is completed.

In addition, as a manufacturing method of the PTC element 1, it is not restricted to said process. For example, the bonding in advance by solder S ₁ and Ni plate 4a and the terminal electrode 3A of the cladding plate 4, after joining the terminal electrodes 3B and Ni plate 5 beforehand with solder S _2, clad plate 4 with the terminal electrodes 3A The terminal electrodes 3A and 3B may be thermocompression bonded to the PTC element body 2 in a state where the PTC element body 2 is sandwiched from above and below by the terminal electrode 3B with the Ni plate 5 attached.

  By the way, although the clad plate 4 is comprised from the Ni plate 4a and the Al plate 4b, the linear expansion of Ni and Al differs greatly. For this reason, when heat of about 230 ° C. is applied to the clad plate 4 in the above reflow process, the Al plate 4b located on the opposite side of the PTC element body 2 is melted first, so that the Al plate 4b becomes the Ni plate 4a. It becomes easier to stretch. As a result, the clad plate 4 is deformed and tends to warp in a U shape toward the PTC element body 2 side.

FIG. 4 is a cross-sectional view and a plan view showing a conventional PTC element as a comparative example. PTC element 50 shown in this figure, that the solder S ₁ is printed on the entire surface of the terminal electrodes 3A, above the gap in the region corresponding to the edge of the terminal electrodes 3A between the terminal electrodes 3A and the cladding plate 4 6 has a structure that does not exist.

In this structure, the clad plate 4 is going Hanro the PTC element body 2 side, the force due to warping of the cladding plate 4 is added to the PTC element body 2 through the solder S ₁ and the terminal electrodes 3A, PTC element body 2 becomes deformed. When the deformation of the PTC element body 2 due to the warping of the clad plate 4 is repeated, the PTC element body 2 is damaged, and therefore the characteristics of the PTC element 50 are deteriorated such that the resistance value of the PTC element 50 cannot be returned while increasing. Resulting in. This phenomenon also occurs when the PTC element 50 receives heat from a temperature test or the like.

  In contrast, in the present embodiment, since the gap 6 is provided in the region corresponding to the edge of the terminal electrode 3A between the terminal electrode 3A and the clad plate 4, when the clad plate 4 receives heat, the clad plate 4 However, it is difficult for the force due to the warping of the clad plate 4 to be applied to the PTC element body 2 because it is bent and warped in the gap 6 portion conveniently toward the PTC element body 2 side. Thereby, deformation of the PTC element body 2 due to warping of the clad plate 4 is suppressed, and damage to the PTC element body 2 is reduced. As a result, it is possible to ensure desired resistance-temperature characteristics without degrading the characteristics of the PTC element 1.

  In order to demonstrate such an operational effect, an on / off test is performed in which a predetermined voltage is intermittently applied to the PTC element of the present embodiment as shown in FIG. 1 and the PTC element of the comparative example as shown in FIG. And evaluated.

  Specifically, a cycle in which the PTC element that normally operates at a voltage of about 6 V was used and energized for 15 seconds under the condition of 20 V-20 A and then stopped for 165 seconds was repeated until the PTC element was destroyed. In an actual product, it is desired not to be destroyed even when such an abnormal voltage is applied. For example, it is necessary not to break for about 10 cycles.

サンプル１〜５は、比較例のＰＴＣ素子についての試験結果であり、サンプル６〜１０は、本実施形態のＰＴＣ素子についての試験結果である。 Such an on / off test was performed, and the number of cycles at which destruction occurred was compared. The test results are shown below.

Samples 1 to 5 are test results for the PTC element of the comparative example, and samples 6 to 10 are test results for the PTC element of the present embodiment.

  As can be seen from Table 1, the PTC element of the comparative example was destroyed in the first cycle, and the best one was broken in the seventh cycle. This is because the PTC element body is repeatedly deformed due to warpage of the clad plate as a result of heat generated in the clad plate by applying a high voltage.

  On the other hand, it is clear from Table 1 that the PTC element of this embodiment takes 10 to 15 cycles to break down and can withstand the on / off test up to about twice that of the comparative example. The reason is that by providing a gap in a region corresponding to the edge of the terminal electrode between the terminal electrode and the clad plate, deformation of the PTC element body due to the warp of the clad plate is suppressed. From the above, it can be said that the effectiveness of the present invention has been sufficiently demonstrated.

  FIG. 5 is a cross-sectional view showing a second embodiment of the PTC element according to the present invention. In the figure, the same or equivalent members as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In the figure, the PTC element 10 of this embodiment is different from the PTC element 1 of the first embodiment only in that a coating resin portion 11 is additionally provided. The coating resin part 11 constitutes a buffer part for alleviating deformation of the PTC element body 2 due to warpage of the clad plate 4.

  Specifically, the coating resin portion 11 is provided so as to cover all or part of the side surface of the PTC element body 2 in the region between the clad plate 4 and the Ni plate 5. The coating resin portion 11 corresponds to a region corresponding to the edge portion of the terminal electrode 3A between the terminal electrode 3A and the clad plate 4 and an edge portion of the terminal electrode 3B between the terminal electrode 3B and the Ni plate 5. It is also provided in the area. As resin which forms the coating resin part 11, the epoxy resin etc. which become soft when heat | fever of the temperature of 100 degreeC or more is added, for example are preferable.

  Thus, since the coating resin part 11 was provided so that the side surface of the PTC element body 2 might be covered, the PTC element body 2 can be protected from oxygen. Further, since the coating resin portion 11 is also provided between the terminal electrode 3A and the clad plate 4 and between the terminal electrode 3B and the Ni plate 5, the bonding strength between the terminal electrode 3A and the clad plate 4 due to the anchor effect. The bonding strength between the terminal electrode 3B and the Ni plate 5 is increased, and the terminal electrodes 3A and 3B can be reliably prevented from peeling off.

  Here, when heat is applied to the clad plate 4 in a reflow process or the like, the clad plate 4 tends to warp toward the PTC element body 2 side. However, the coating resin portion 11 becomes sufficiently soft when heat of about 230 ° C. is applied as described above. For this reason, since the clad plate 4 bends and warps toward the PTC element body 2 at the soft coating resin portion 11, the force due to the warp of the clad plate 4 is less likely to be applied to the PTC element body 2. Thereby, since the deformation | transformation of the PTC element body 2 by the curvature of the clad board 4 is suppressed, the damage given to the PTC element body 2 can be reduced.

  FIG. 6 is a cross-sectional view showing a third embodiment of the PTC element according to the present invention. In the figure, the same or equivalent members as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In the figure, the PTC element 20 of the present embodiment performs the joining of the terminal electrode 3A and the clad plate 4 and the joining of the terminal electrode 3B and the Ni plate 5 not by soldering as in the first embodiment but by welding. It is a thing.

  Specifically, the PTC element 20 includes a Ni spacer 21A interposed between the terminal electrode 3A and the clad plate 4, and a Ni spacer 21B interposed between the terminal electrode 3B and the Ni plate 5. Yes. The Ni spacer 21A, the terminal electrode 3A, and the Ni plate 4a of the clad plate 4 are welded, and the Ni spacer 21B, the terminal electrode 3B, and the Ni plate 5 are welded. The terminal electrodes 3A and 3B have a thickness of about 0.1 mm, for example. The thickness of the Ni spacers 21A and 21B is, for example, about 50 μmm.

  The Ni spacer 21 </ b> A is interposed in a region corresponding to a portion excluding the entire edge portion of the terminal electrode 3 </ b> A between the terminal electrode 3 </ b> A and the clad plate 4. As a result, a gap 22 is formed in a region corresponding to the entire edge of the terminal electrode 3 </ b> A between the terminal electrode 3 </ b> A and the clad plate 4. The air gap 22 constitutes a buffer portion for relaxing deformation of the PTC element body 2 due to warpage of the clad plate 4. The gap 22 has the same width W as the gap 6 described above. The Ni spacer 21B is disposed to correspond to the Ni spacer 21A.

  Next, a method for manufacturing the PTC element 20 configured as described above will be described with reference to FIG.

  First, in the same manner as in the first embodiment, a PTC element body 2 as shown in FIG. Subsequently, each Ni plate is thermocompression bonded in a state where the PTC element body 2 is sandwiched from above and below by two Ni plates, so that as shown in FIG. 7B, the terminal electrodes 3A, 3B is formed. Thereby, the element main body 8 which consists of the PTC element | base_body 2 and terminal electrode 3A, 3B is obtained. The conditions for the thermocompression treatment at this time are the same as in the first embodiment.

  Subsequently, as shown in FIG. 7C, the Ni plate 5 is stacked on the terminal electrode 3B via the Ni spacer 21B, and the welding terminals 24a and 24b are arranged in this state. Then, the terminal electrode 3B and the Ni plate 5 are welded through the Ni spacer 21B by energizing the welding terminals 24a and 24b in the direction of the arrow shown in the drawing.

  Subsequently, as shown in FIG. 7 (d), the element body 8 to which the Ni plate 5 is welded is stacked on the clad plate 4 via the Ni spacer 21A, and the welding terminals 24a and 24b are arranged in this state. Then, the terminal electrode 3B and the clad plate 4 are welded via the Ni spacer 21A by energizing the welding terminals 24a and 24b in the direction indicated by the arrows. Thus, the above-described PTC element 20 is completed.

  In the present embodiment as described above, since the gap 22 is provided in the region corresponding to the edge of the terminal electrode 3A between the terminal electrode 3A and the clad plate 4, the clad plate 4 receives heat and receives the PTC element body. Even if warped to the second side, damage to the PTC element body 2 due to warpage of the clad plate 4 is reduced. Thereby, the characteristic deterioration of the PTC element 20 can be prevented.

  In the third embodiment, the gap 22 is formed between the terminal electrode 3A and the clad plate 4 by interposing the Ni spacer 21A between the terminal electrode 3A and the clad plate 4. Without providing the Ni spacer 21A, for example, a step (notch) is formed at the edge of the terminal electrode 3A so that the terminal electrode 3A has a convex structure, whereby a gap is formed between the terminal electrode 3A and the clad plate 4. May be formed.

  Further, as in the second embodiment, a resin resin may be filled in the gap 22 formed between the terminal electrode 3A and the clad plate 4 to form a coating resin portion.

  Although several preferred embodiments of the PTC element according to the present invention have been described above, the present invention is not limited to the above embodiments. For example, in the above embodiment, the gap or the coating resin portion is formed in the region corresponding to the edge portion of the terminal electrode 3B between the terminal electrode 3B and the Ni plate 5, but between the terminal electrode 3B and the Ni plate 5 In particular, the voids and the coating resin portion need not be formed.

  In the above embodiment, the gap or the coating resin portion constituting the buffer portion is formed in the region corresponding to the entire edge portion of the terminal electrode 3A between the terminal electrode 3A and the clad plate 4. The portion may be only in a region corresponding to a part of the edge of the terminal electrode 3A between the terminal electrode 3A and the clad plate 4.

  In the above embodiment, the clad plate 4 in which Ni and Al are overlapped is used. However, the plurality of types of metal materials constituting the clad plate 4 are not particularly limited, and the clad plate 4 is welded. What is necessary is just to determine according to metal materials, such as a battery cell.

It is sectional drawing which shows 1st Embodiment of the PTC element concerning this invention. It is a top view of the PTC element shown in FIG. It is sectional drawing which shows the manufacturing process of the PTC element shown in FIG. It is sectional drawing and a top view which show the conventional PTC element as a comparative example. It is sectional drawing which shows 2nd Embodiment of the PTC element concerning this invention. It is sectional drawing which shows 3rd Embodiment of the PTC element concerning this invention. It is sectional drawing which shows the manufacturing process of the PTC element shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... PTC element, 2 ... PTC element | base_body, 3A ... Terminal electrode (1st terminal electrode), 3B ... Terminal electrode (2nd terminal electrode), 4 ... Cladding plate, 4a ... Ni plate, 4b ... Al plate, 5 ... Ni plate (metal plate), 6 ... gap (buffer part), 10 ... PTC element, 11 ... coating resin part (buffer part), 20 ... PTC element, 21A ... Ni spacer (metal spacer), 22 ... gap (buffer part) ) S ₁ ... Solder.

Claims (5)

A PTC body;
A first terminal electrode and a second terminal electrode fixed to the PTC element body so as to face each other with the PTC element body interposed therebetween;
A clad plate bonded to the first terminal electrode and overlaid with a plurality of types of metals;
A metal plate joined to the second terminal electrode,
In a region corresponding to the edge portion of the first terminal electrode between the first terminal electrode and the clad plate, a buffer portion is provided for alleviating deformation of the PTC element body due to warpage of the clad plate. A PTC element characterized by comprising:   2. The air gap constituting the buffer portion is formed in a region corresponding to an edge portion of the first terminal electrode between the first terminal electrode and the clad plate. PTC element.   The coating resin part which comprises the said buffer part is provided in the area | region corresponding to the edge part of the said 1st terminal electrode between the said 1st terminal electrode and the said clad board, The said resin part is provided. The PTC element described. The clad plate is joined to the first terminal electrode by solder;
4. The solder according to claim 1, wherein the solder is provided in a region corresponding to a portion excluding an edge of the first terminal electrode between the first terminal electrode and the clad plate. The PTC element according to one item. The clad plate is welded to the first terminal electrode through a metal spacer,
The said metal spacer is interposed in the area | region corresponding to the part except the edge part of the said 1st terminal electrode between the said 1st terminal electrode and the said clad board. The PTC element according to claim 1.

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