JPWO2015198615A1 - PTC thermistor and manufacturing method thereof - Google Patents

Abstract

The PTC thermistor includes an element body, an internal electrode provided in the element body, an external electrode that is electrically connected to the internal electrode and covers a part of the outer surface of the element body, and a metal film provided on the external electrode. The outer surface of the element body has a covered region covered with the external electrode and an uncovered region that is not covered with the external electrode and exposed to the outside. The non-covering region is at a lower position than the portion of the covering region connected to the non-covering region.

Description

  The present invention relates to a PTC thermistor and a method for manufacturing the same.

  Conventionally, as a PTC thermistor, there exist some which were described in Unexamined-Japanese-Patent No. 2012-38811 (patent document 1). As shown in FIG. 4, the PTC thermistor 100 includes an element body 101 made of ceramics having a positive resistance temperature characteristic, and a plurality of internal electrodes 102A and 102B provided by being laminated in the element body 101. Have.

  In two adjacent internal electrodes 102A and 102B, the end portion 102a of the first internal electrode 102A is exposed from the first end surface 101a of both end surfaces of the outer surface of the element body 101, and the second internal electrode 102B The end portion 102 b is exposed from the second end surface 101 b of both end surfaces of the outer surface of the element body 101.

  A coating layer 103 made of a glass material is formed on the side surface 101c of the outer surface of the element body 101 excluding both end surfaces 101a and 101b. First and second external electrodes 104A and 104B are provided on both end faces 101a and 101b of the element body 101, respectively. The first external electrode 104A covers the first end surface 101a of the element body 101 and is electrically connected to the end portion 102a of the first internal electrode 102A. The second external electrode 104B covers the second end surface 101b of the element body 101 and is electrically connected to the end portion 102b of the second internal electrode 102B. A metal film 105 is provided on the first and second external electrodes 104A and 104B.

  A method for manufacturing the conventional PTC thermistor 100 will be described. The coating layer 103 is formed on the side surface 101c of the element body 101, and the first and second external electrodes 104A and 104B are formed on both end faces 101a and 101b of the side element body 101. Thereafter, the element body 101 is immersed in a plating solution, and the metal film 105 is formed on the first and second external electrodes 104A and 104B by plating. At this time, since the coating layer 103 is made of a glass material, the metal film 105 is not formed on the coating layer 103.

  Here, if the coating layer 103 is not provided, since the element body 101 is made of ceramics having a positive resistance temperature characteristic, the specific resistance of the element body 101 becomes low. The metal film 105 is also deposited on the 101c by plating (for example, plating growth). As a result, the appearance defect rate of the PTC thermistor 100 increases. The appearance defect rate means that the metal film 105 on the first external electrode 104A and the metal film 105 on the second external electrode 104B are electrically connected via the metal film 105 on the side surface 101c of the element body 101. Indicates the probability of being connected.

  As described above, in the conventional PTC thermistor 100, the coating layer 103 is provided to suppress the deposition of the metal film 105 on the side surface 101 c of the element body 101.

JP 2012-38811 A

  However, in the conventional PTC thermistor 100, the coating layer 103 for suppressing the deposition of the metal film 105 on the element body 101 is required, and there is a problem that the cost increases.

  Therefore, an object of the present invention is to provide a PTC thermistor that does not require a coating layer for suppressing the deposition of a metal film on an element body and a method for manufacturing the same.

In order to solve the above problems, the PTC thermistor of the present invention is
An element body composed of ceramics having a positive resistance temperature characteristic;
An internal electrode provided in the element body and having an end exposed from an outer surface of the element element;
An external electrode electrically connected to the end of the internal electrode and covering a part of the outer surface of the element body;
A metal film provided on the external electrode,
The outer surface of the element body is
A covering region covered with the external electrode;
An uncovered region that is not covered by the external electrode and exposed to the outside,
The non-covering region is characterized by being located at a position lower than a portion of the covering region connected to the non-covering region.

  According to the PTC thermistor of the present invention, the metal film is provided on the external electrode, and the outer surface of the element body is covered with the external electrode and exposed to the outside without being covered with the external electrode. The non-covered area is at a lower position than the portion of the covered area connected to the non-covered area.

  Thereby, the coating layer such as a glass material is not on the non-covering region, and the metal film is not formed on the non-covering region. Therefore, since there is no coating layer for suppressing the deposition of the metal film on the uncovered region, the cost can be reduced.

In the PTC thermistor of one embodiment,
The element body has a first end face and a second end face located on opposite sides of each other;
There are two external electrodes, the first external electrode covers the first end face of the element body, and the second external electrode covers the second end face of the element body.

  According to the PTC thermistor of the embodiment, the first external electrode covers the first end face of the element body, and the second external electrode covers the second end face of the element body. Thereby, since there is no metal film in the uncovered region of the element body between the first external electrode and the second external electrode, the first external electrode and the second external electrode are not short-circuited.

  In one embodiment of the PTC thermistor, the element body is made of a barium titanate semiconductor ceramic and contains at least one element of Mn, Pb, Ni, and Co.

  According to the PTC thermistor of the embodiment, the element body is made of barium titanate-based semiconductor ceramics and includes at least one element of Mn, Pb, Ni, and Co. Thereby, when the metal film is formed on the external electrode by plating, the element body is easily dissolved in the plating solution. Therefore, when the metal film is formed on the external electrode by plating, the rate at which the element body melts can be faster or equal to the rate at which the metal film is deposited on the element body, so that the metal film is deposited on the element body. Without being deposited on the external electrode.

Moreover, in the manufacturing method of the PTC thermistor of one embodiment,
An internal electrode is provided in a body made of ceramic having positive resistance temperature characteristics, an end of the internal electrode is exposed from an outer surface of the base body, and an external electrode is electrically connected to the end of the internal electrode. A first step of covering a part of the outer surface of the element body with the external electrode while being connected;
A second step of immersing the element body in a plating solution and forming a metal film on the external electrode by plating;
The second step includes
Forming the metal film on the external electrode while dissolving the uncovered area of the outer surface of the element body not covered by the external electrode with a plating solution so as not to form the metal film in the uncovered area. Thus, the uncovered region is positioned lower than the covered region of the outer surface of the element body covered with the external electrode.

  According to the manufacturing method of the PTC thermistor of the above embodiment, the second step is to dissolve the uncovered area on the outer surface of the element body not covered with the external electrode with a plating solution so as not to form a metal film in the uncovered area. On the other hand, a metal film is formed on the external electrode, so that the uncovered region is positioned lower than the covered region of the outer surface of the element body covered with the external electrode.

  Thereby, even if a coating layer such as a glass material is not provided on the non-covering region, the metal film is not deposited on the non-covering region. Therefore, a step of providing a coating layer for suppressing the deposition of the metal film on the uncovered region is not required, and the cost can be reduced.

  In one embodiment of the method for producing a PTC thermistor, the plating solution has a property that the rate at which the element body melts is faster than or equal to the rate at which the metal film is deposited on the element body. Have.

  According to the method for manufacturing a PTC thermistor of the above embodiment, the plating solution has a property that the rate at which the element body dissolves is faster or equal to the rate at which the metal film is deposited on the element body. Thereby, the metal film can be deposited on the external electrode without being deposited on the element body.

  In one embodiment of the method for manufacturing a PTC thermistor, the element body is made of barium titanate semiconductor ceramics and contains at least one of Mn, Pb, Ni, and Co.

  According to the method for manufacturing a PTC thermistor of the above embodiment, the element body is made of barium titanate-based semiconductor ceramics and contains at least one of Mn, Pb, Ni, and Co. As a result, the element body is easily dissolved in the plating solution, and the rate at which the element body itself dissolves can be faster or equal to the rate at which the metal film is deposited on the element body, so that the metal film is deposited on the element body. Without being deposited on the external electrode.

  According to the PTC thermistor and the manufacturing method thereof of the present invention, a coating layer for suppressing the deposition of a metal film on the element body can be made unnecessary.

It is sectional drawing which shows the PTC thermistor of one Embodiment of this invention. It is an enlarged view of the A section of FIG. It is explanatory drawing explaining the manufacturing method of the PTC thermistor of one Embodiment of this invention. It is explanatory drawing explaining the manufacturing method of the PTC thermistor of one Embodiment of this invention. It is explanatory drawing explaining the manufacturing method of the PTC thermistor of one Embodiment of this invention. It is sectional drawing which shows the conventional PTC thermistor.

  Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

  FIG. 1 is a cross-sectional view showing a PTC thermistor according to an embodiment of the present invention. FIG. 2 is an enlarged view of a portion A in FIG. As shown in FIGS. 1 and 2, a PTC (Positive Temperature Coefficient) thermistor 1 includes an element body 10 made of ceramics having positive resistance temperature characteristics, and a plurality of layers provided in the element body 10. Internal electrodes 21 and 22. The PTC thermistor 1 has a characteristic that electrical resistance rapidly increases at the Curie temperature.

  The element body 10 is formed in a substantially rectangular parallelepiped shape. The outer surface of the element body 10 has a first end surface 10a and a second end surface 10b located on opposite sides, and a side surface 10c in the circumferential direction between the first end surface 10a and the second end surface 10b. The element body 10 is made of, for example, a barium titanate semiconductor ceramic. The element body 10 may be composed of other ceramics having positive resistance temperature characteristics. The element body 10 preferably contains, for example, at least one element of Mn, Pb, Ni, and Co. By doing so, the element body 10 is easily dissolved in the plating solution, as will be described later. .

  The internal electrodes 21 and 22 are formed in a substantially flat plate shape. The internal electrodes 21 and 22 include, for example, at least one element of Ni, Cu, Fe, Co, W, Ta, Ti, and Mo.

  The plurality of internal electrodes 21 and 22 are arranged substantially in parallel with a space therebetween. In the two adjacent internal electrodes 21 and 22, the end 21a of the first internal electrode 21 is exposed from the first end surface 10a of the element body 10, and the end 22a of the second internal electrode 22 is exposed to the element body. 10 is exposed from the second end face 10b.

  A first external electrode 41 is provided on the first end face 10 a of the element body 10. A second external electrode 42 is provided on the second end face 10 b of the element body 10. The first and second external electrodes 41 and 42 are made of Ag, for example. For example, the first and second external electrodes 41 and 42 are formed by baking after applying an Ag paste to the element body 10.

  The first external electrode 41 is in contact with and electrically connected to the end 21 a of the first internal electrode 21. The first external electrode 41 covers a part of the outer surface of the element body 10. Specifically, the first external electrode 41 covers all of the first end face 10 a of the element body 10 and also covers the end of the side face 10 c of the element body 10 on the first end face 10 a side.

  The second external electrode 42 is in contact with and electrically connected to the end 22 a of the second internal electrode 22. The second external electrode 42 covers a part of the outer surface of the element body 10. Specifically, the second external electrode 42 covers all of the second end face 10 b of the element body 10 and also covers the end of the side face 10 c of the element body 10 on the second end face 10 b side.

  A metal film 50 is provided on the external electrodes 41 and 42. The metal film 50 is formed by plating. The external electrodes 41 and 42 are joined to the wiring on the substrate (not shown) via the metal film 50 by solder or the like. The metal film 50 includes a first layer 51 that is in contact with the first and second external electrodes 41 and 42, and a second layer 52 that is stacked on the first layer 51. The first layer 51 is made of, for example, Ni, and the second layer 52 is made of, for example, Sn. The first layer 51 made of Ni prevents contact between the second layer 52 made of Sn and the external electrodes 41, 42, and prevents corrosion of the external electrodes 41, 42 by the second layer 52. Further, the second layer 52 improves solder wettability.

  The metal film 50 is formed in the entire area of the upper surface of the external electrodes 41 and 42, but may be formed in a partial area of the upper surface of the external electrodes 41 and 42. A part or all of the second layer 52 of the metal film 50 may be melted into solder at the time of soldering.

  The outer surface of the element body 10 has a covered region Z1 covered with the external electrodes 41 and 42 and a non-covered region Z2 which is not covered with the external electrodes 41 and 42 and is exposed to the outside. Specifically, the covering region Z1 includes the first region at the end of the side surface 10c on the first end surface 10a side and the entire region of the first end surface 10a covered by the first external electrode 41. These are the entire region of the second end surface 10b and the second region at the end of the side surface 10c on the second end surface 10b side, which are covered by the two external electrodes 42. The uncovered area Z2 is all the third areas except for the first and second areas of the side surface 10c.

  The uncovered region Z2 is at a lower position than the portion of the covered region Z1 that is connected to the uncovered region Z2. Here, the height reference position (lowest position) is the center of the element body 10. Specifically, the third region of the side surface 10c corresponding to the non-covered region Z2 is located lower than the first and second regions of the side surface 10c corresponding to a part of the covered region Z1. A concave portion 11 is provided in the third region of the side surface 10c of the element body 10, and the concave portion 11 corresponds to the non-covered region Z2. The shape of the recess 11 is a shape that is recessed with a uniform depth over the entire circumference of the side surface 10 c of the element body 10. The difference in height (hereinafter referred to as step H) between the lowest portion of the non-covering region Z2 and the portion of the covering region Z1 connected to the non-covering region Z2 is the depth of the recess 11. Matches. The level difference H is, for example, 10 μm when the thickness of the external electrodes 41 and 42 is 30 μm and the thickness of the metal film 50 is 3 μm.

  As described later, the step H (recess 11) is formed by immersing the element body 10 in a plating solution used when the metal film 50 is formed by plating, and dissolving the element body 10 with the plating solution. . The uncoated region Z2 of the element body 10 has a melting mark and a surface roughness melted by the plating solution.

  Next, a method for manufacturing the PTC thermistor 1 will be described.

  First, as shown in FIG. 3A, a plurality of ceramic sheet bodies 5 made of ceramics having positive resistance temperature characteristics are formed. Then, the electrode paste is printed on the upper surface of a predetermined number of ceramic sheet bodies 5 to form internal electrodes 21 and 22. When printing the internal electrodes 21, 22, only the one end surfaces 21 a, 22 a of the internal electrodes 21, 22 extend to the outer edge of the ceramic sheet body 5, and the other end surfaces of the internal electrodes 21, 22 are positioned inside the ceramic sheet body 5. To do.

  Then, the plurality of ceramic sheet bodies 5 on which the internal electrodes 21 and 22 are printed are overlapped so that the ceramic sheet bodies 5 and the internal electrodes 21 and 22 are alternately positioned. At this time, the one end surfaces 21 a and 22 a of the internal electrodes 21 and 22 are alternately positioned on the left and right end surfaces of the ceramic sheet body 5.

  Thereafter, the plurality of laminated ceramic sheet bodies 5 are pressure-bonded by a press to form a laminated body 6 as shown in FIG. 3B. The laminated body 6 includes an element body 10 formed by press-bonding a plurality of ceramic sheet bodies 5 and internal electrodes 21 and 22 provided in the element body 10. The end 21a of the first internal electrode 21 is exposed from the first end face (left end face) 10a of the element body 10, and the end 22a of the second internal electrode 22 is exposed to the second end face ( (Right end face) 10b is exposed.

  Thereafter, as shown in FIG. 3C, Ag paste is applied to the left and right end portions of the first and second end faces 10a and 10b and the side face 10c of the element body 10, and then baked to form the external electrodes 41 and 42. The first external electrode 41 covers the entire region of the first end surface 10a and the region of the left end portion of the side surface 10c. The first external electrode 41 is in contact with and electrically connected to the end 21 a of the first internal electrode 21. The second external electrode 42 covers the entire region of the second end surface 10b and the region of the right end portion of the side surface 10c. The second external electrode 42 is in contact with and electrically connected to the end 22 a of the second internal electrode 22.

  Thereafter, the element body 10 is immersed in a plating solution, and as shown in FIGS. 1 and 2, a metal film 50 is formed on the external electrodes 41 and 42 by plating. That is, the element body 10 is immersed in a first plating solution containing the components of the first layer 51 of the metal film 50 (for example, the solute is Ni and the solvent is water) to form the first layer 51. The body 10 is immersed in a second plating solution containing the components of the second layer 52 of the metal film 50 (for example, the solute is Sn and the solvent is water) to form the second layer 52.

  At this time, the external electrodes 41 and 42 are not formed in the uncovered region Z2 by dissolving the uncovered region Z2 on the outer surface of the element body 10 not covered by the external electrodes 41 and 42 with a plating solution. A metal film 50 is formed thereon. That is, melting of the element body 10 and plating formation of the metal film 50 are performed simultaneously. As a result, the uncovered region Z1 is positioned lower than the covered region Z1 and the uncovered region Z2 on the outer surface of the element body 10 covered by the external electrodes 41 and 42.

  More specifically, the metal film 50 is deposited also in the uncovered region Z2, but the metal film 50 cannot remain in the element body 10 because the element body 10 is dissolved by the plating solution after the metal film 50 is deposited. . As a result, the recess 11 is formed in the uncovered region Z2, and the metal film 50 is not formed.

  The step H is obtained from the relationship between the area of the outer surface of the element body 10 and the surface area of the external electrodes 41 and 42. For example, the area of the outer surface of the element body 10 is Sc, the specific resistance of the element body 10 is ρc, the surface area of the external electrodes 41 and 42 is Se, the specific resistance of the external electrodes 41 and 42 is ρe, and the metal on the external electrodes 41 and 42 The film forming speed of the film 50 (plating) is P (μm / H), and the step H is H = P * ρe * Se / (ρc * Sc).

  Further, the level difference H can be changed depending on, for example, the type and amount of the element added to the element body 10, the pH of the plating solution, the magnitude of the voltage applied to the plating solution, and the temperature of the plating solution. For example, as for the level difference H, the larger the amount of the element added to the element body 10, the lower the pH of the plating solution, the greater the voltage applied to the plating solution, and the higher the temperature of the plating solution, Can be big.

  The plating solution preferably has a property that the speed at which the element body 10 is melted is faster or equivalent to the speed at which the metal film 50 is deposited on the element body 10. The properties of the plating solution are determined by, for example, the pH of the plating solution, the temperature of the plating solution, or the plating current. The speed at which the element body 10 is melted is determined by measuring the melt thickness of the element body 10 per hour. The rate at which the metal film 50 is deposited on the element body 10 is determined by measuring the deposition thickness of the element body 10 per hour. As a result, the metal film 50 can be deposited on the external electrodes 41 and 42 without depositing on the element body 10 more reliably.

  The element body 10 is preferably made of barium titanate-based semiconductor ceramics and contains at least one of Mn, Pb, Ni, and Co. As a result, the element body 10 is easily dissolved in the plating solution, and the speed at which the element body 10 itself dissolves can be made faster or equal to the speed at which the metal film 50 is deposited on the element body 10. Can be deposited on the external electrodes 41 and 42 without being deposited on the element body 10. The greater the amount of Mn, Pb, Ni, and Co added, the easier the element body 10 dissolves in the plating solution. For example, in the case of Mn, there is an effect when the addition amount is 0.001 mol% to 0.2 mol%, and in the case of Pb, the addition amount is 0.001 mol% to 20 mol%. If the mol% is low, BaTiO3 is the main component, which makes it difficult to dissolve, and if it is too much, the properties are affected.

  According to the PTC thermistor 1 of the above-described embodiment, the metal film 50 is provided on the external electrodes 41 and 42, and the outer surface of the element body 10 is covered with the covering region Z1 covered with the external electrodes 41 and 42, and the external electrode 41 and 42 and is exposed to the outside, and the non-covering region Z2 is lower than the portion of the covering region Z1 connected to the non-covering region Z2. It is in.

  Thereby, the coating layer such as a glass material is not on the non-covering region Z2, and the metal film 50 is not formed on the non-covering region Z2. Therefore, since there is no coating layer for suppressing the deposition of the metal film 50 on the uncovered region Z2, the cost can be reduced. Moreover, since there is no coating layer, reduction in thermal conductivity and heat dissipation resulting from the coating layer is suppressed.

  Further, since the metal film 50 is not present in the uncovered region Z2 of the element body 10 between the first external electrode 41 and the second external electrode 42, the first external electrode 41, the second external electrode 42, Are not electrically connected. That is, the appearance defect rate (the probability that the metal film 50 on the first external electrode 41 and the metal film 50 on the second external electrode 42 are electrically connected) can be reduced.

  According to the manufacturing method of the PTC thermistor 1 of the above embodiment, the metal film 50 is formed in the non-covered region Z2 by dissolving the non-covered region Z2 on the outer surface of the element body 10 not covered by the external electrodes 41 and 42 with the plating solution. In such a manner, the metal film 50 is formed on the external electrodes 41 and 42 so that the uncovered region Z2 is lower than the portion of the covered region Z1 connected to the uncovered region Z2. Become.

  Thereby, even if a coating layer such as a glass material is not provided on the non-covering region Z2, the metal film 50 is not deposited on the non-covering region Z2. Therefore, a process of providing a coating layer for suppressing the deposition of the metal film 50 on the uncovered region Z2 is not necessary, and the cost can be reduced.

  Conventionally, there has been an idea that the element body of the PTC thermistor is difficult to dissolve in the plating solution. For this reason, in the past, attention was paid only to the fact that a metal film was deposited on the surface of the element body by plating, and in order to prevent this, a glass material coating layer was formed on the surface of the element body. On the other hand, the inventor of the present application pays attention to dissolving the PTC thermistor element body in the plating solution, which is a completely opposite idea, and melting the element body with the plating solution and forming the metal film by plating. And found the idea of doing it at the same time. This prevents the metal film from being deposited on the surface of the element body without providing a coating layer of glass material on the surface of the element body.

(Example)
Next, an example of a method for manufacturing the PTC thermistor 1 will be described.

First, BaCO ₃ , SrCO ₃ , CaCO ₃ , TiO ₂ , La ₂ O ₃ , SiO ₂ , and MnCO ₃ are used as raw materials to prepare the following composition.
(Ba _0.857 Ca _0.10 Sr _0.04 La _0.003 ) TiO ₃ +0.008 Mn + 0.01 SiO ₂
The raw material is put in a container together with pure water and zirconia balls, pulverized for 5 hours, and calcined at 1100 ° C. for 2 hours. The temporarily fired body is pulverized to form a temporarily fired powder.

  Then, an organic binder, a solvent, and a dispersant are mixed with the calcined powder to form a green sheet, and the green sheet is cut into a rectangular shape having a predetermined size to form a plurality of ceramic sheet bodies. To do.

  Thereafter, as shown in FIG. 3A, a conductive powder made of Ni and a varnish are mixed to prepare an electrode paste, and this electrode paste is printed on the upper surface of a predetermined number of ceramic sheet bodies 5 to form internal electrodes 21 and 22. Form. And the several ceramic sheet body 5 is laminated | stacked, the laminated | stacked ceramic sheet body 5 is crimped | bonded by a press, and as shown to FIG. 3B, the laminated body 6 is formed.

  Thereafter, as described above, as shown in FIG. 3C, external electrodes 41 and 42 are formed on the element body 10, and then the element body 10 is immersed in a plating solution. While forming the metal film 50 on the external electrodes 41 and 42 by plating, the recess 11 (step H) is provided in the uncovered region Z2 of the element body 10.

  Next, an example of performing plating with a plating solution having a pH at which the element body melts will be described. Table 1 shows the relationship between the pH of the plating solution and the melting rate of the element body.

表１において、「異常めっき析出速度」とは、素体にめっき（金属膜）が析出する速度をいう。「素体溶融速度」とは、素体が溶融する速度をいう。「外観不良率」とは、素体にめっきが析出して、第１の外部電極上の金属膜と、第２の外部電極上の金属膜とが、素体上の金属膜を介して、電気的に接続される確率を示す。外観不良率が０％であるとき、素体の非被覆領域上に金属膜が設けられず、第１の外部電極上の金属膜と第２の外部電極上の金属膜とが、電気的に接続されるおそれがないことをいう。

In Table 1, “abnormal plating deposition rate” refers to the rate at which plating (metal film) is deposited on the element body. “Element melting rate” refers to the rate at which the element melts. "Appearance defect rate" means that the metal film on the first external electrode and the metal film on the second external electrode are deposited on the element body through the metal film on the element body. Indicates the probability of being electrically connected. When the appearance defect rate is 0%, no metal film is provided on the uncovered region of the element body, and the metal film on the first external electrode and the metal film on the second external electrode are electrically This means there is no risk of being connected.

  As can be seen from Table 1, the base body melting rate can be changed by adjusting the pH of the plating solution. That is, the lower the pH of the plating solution, the larger the element melting rate.

  As shown in Example 1, the pH of the plating solution was set to 3, and the pH of the plating solution was set to 1.5 as shown in Example 2, so that (abnormal plating deposition rate) / (element melting rate) Becomes 1 or less, and the appearance defect rate becomes 0%. This is presumably due to the fact that although the deposition of plating occurs on the element body, the element body melts after the deposition of plating, so that the deposited components of the plating cannot remain in the element body.

  On the other hand, as shown in Comparative Example 1, when the pH of the plating solution is set to 5, (abnormal plating deposition rate) / (element melting rate) becomes greater than 1, and the appearance defect rate increases. This is because the element melts after the deposition of the plating, but because the deposition rate of the plating is faster, the plating acts as a wall between the plating solution and the element, thereby inhibiting the melting of the element. It is thought that the defect rate increases.

  Next, an example will be described in which an element that is easily melted into the plating solution is added to the element body and plating is performed. Table 2 shows the relationship between the additive element and the element melting rate.

表２において、「異常めっき析出速度」「素体溶融速度」「外観不良率」とは、表１で既に説明しているため、その説明を省略する。

In Table 2, “abnormal plating deposition rate”, “element body melting rate”, and “appearance defect rate” have already been described in Table 1, and thus the description thereof is omitted.

  As can be seen from Table 2, the melting point of the element body can be changed depending on the additive element. As shown in Example 3, the additive element is Mn, as shown in Example 4, the additive element is Pb, as shown in Example 5, the additive element is Ni, and as shown in Example 6, By using Co as the additive element, (abnormal plating deposition rate) / (element melting rate) becomes 1 or less, and the appearance defect rate becomes 0%. This is presumably due to the fact that although the deposition of plating occurs on the element body, the element body melts after the deposition of plating, so that the deposited components of the plating cannot remain in the element body.

  The present invention is not limited to the above-described embodiment, and the design can be changed without departing from the gist of the present invention.

  In the above embodiment, the metal film is formed of two layers, but may be formed of one layer or three or more layers.

  In the embodiment, the element body is composed of barium titanate semiconductor ceramics, but may be composed of ceramics having positive resistance temperature characteristics.

  In the embodiment, the element body includes at least one of Mn, Pb, Ni, and Co. However, the element body may not include these elements.

DESCRIPTION OF SYMBOLS 1 PTC thermistor 10 Element body 10a 1st end surface 10b 2nd end surface 10c Side surface 11 Recessed part 21 1st internal electrode 21a End part 22 2nd internal electrode 22a End part 41 1st external electrode 42 2nd external electrode 50 Metal film Z1 Covered area Z2 Non-covered area H Step

Claims (6)

An element body composed of ceramics having a positive resistance temperature characteristic;
An internal electrode provided in the element body and having an end exposed from an outer surface of the element element;
An external electrode electrically connected to the end of the internal electrode and covering a part of the outer surface of the element body;
A metal film provided on the external electrode,
The outer surface of the element body is
A covering region covered with the external electrode;
An uncovered region that is not covered by the external electrode and exposed to the outside,
The PTC thermistor, wherein the non-covering region is located at a position lower than a portion of the covering region connected to the non-covering region. The element body has a first end face and a second end face located on opposite sides of each other;
The two external electrodes are provided, wherein the first external electrode covers the first end face of the element body, and the second external electrode covers the second end face of the element body. 1. The PTC thermistor according to 1.   3. The PTC thermistor according to claim 1, wherein the element body is made of a barium titanate semiconductor ceramic and includes at least one element of Mn, Pb, Ni, and Co. 4. An internal electrode is provided in a body made of ceramic having positive resistance temperature characteristics, an end of the internal electrode is exposed from an outer surface of the base body, and an external electrode is electrically connected to the end of the internal electrode. A first step of covering a part of the outer surface of the element body with the external electrode while being connected;
A second step of immersing the element body in a plating solution and forming a metal film on the external electrode by plating;
The second step includes
Forming the metal film on the external electrode while dissolving the uncovered area of the outer surface of the element body not covered by the external electrode with a plating solution so as not to form the metal film in the uncovered area. Thus, the PTC thermistor manufacturing method is characterized in that the uncovered region is positioned lower than the covered region of the outer surface of the element body covered with the external electrode.   The method for manufacturing a PTC thermistor according to claim 4, wherein the plating solution has a property that a speed at which the element body melts is faster than or equal to a speed at which the metal film is deposited on the element body. .   6. The method for manufacturing a PTC thermistor according to claim 4, wherein the element body is made of a barium titanate-based semiconductor ceramic and contains at least one of Mn, Pb, Ni, and Co.

Images