JPH10335114A - Thermistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to perform surface mounting by bump junction by a method wherein the first and the second electrodes are opposingly arranged on one surface of a thermistor element and a bump is formed on the first and the second electrodes. SOLUTION: The first electrode 3 is formed in such a manner that it is extended from the edge of the edge face 2b on the lower face 2a to the center direction. Also, the second electrode 4 is formed in such a manner that it is extended to center direction from the edge of the edge face 2c side. Accordingly, the first and the second electrodes 3 and 4 are opposing with each other on the lower face 2a. The first and the second electrodes 3 and 4 have contact layers 3a and 4a and the external electrode layers 3b and 4b formed on the contract layers. Also, Au bumps 5 and 6 are formed on the external electrode layers 3b and 4b. The bumps 5 and 6 are formed using photolithography technique after formation of the external electrode layers 3b and 4b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermistor element used for temperature detection and circuit temperature compensation, and more particularly, to a thermistor element having an external electrode structure suitable for surface mounting.

[0002]

2. Description of the Related Art In order to enable high-density mounting of electronic components, it is required that a thermistor element be surface-mounted on a printed circuit board or the like. An example of a conventional thermistor element capable of surface mounting is disclosed in Japanese Patent Application Laid-Open No. 7-29704.
No. 6,086,045. This thermistor element is shown in FIG.
This will be described with reference to FIG. In the thermistor element 65, first and second electrodes 67 and 68 are formed so as to face a lower surface of a rectangular parallelepiped thermistor element 66 at a predetermined distance. When the facing distance between the first and second electrodes 67 and 68 is shortened due to miniaturization, the first and second electrodes 67 and 68 may be short-circuited due to generation of a solder bridge during soldering. .

Therefore, in the thermistor element 65, the first,
The external electrodes 69 and 70 are arranged such that the distance between the second electrodes 67 and 68 is greater than the distance between the second electrodes 67 and 68.
Are formed on the electrodes 67, 68. In order to prevent a short circuit, the insulating inorganic material layer 71 is provided with the external electrodes 69 and 7.
It is formed so as to cover the lower surface of the thermistor element body 66 in a region between 0.

In the thermistor element 65, the first and second electrodes 67 and 68 and the external electrodes 69 and 70 are formed only on the lower surface of the thermistor body 66, and are provided so as not to reach the other surfaces. ing. When mounting the thermistor element 65 on the printed circuit board, the thermistor element 6
The thermistor element 65 is placed on the printed circuit board from the lower surface 66a side of 6. Next, the external electrodes 69 and 70 are connected to the printed circuit board using solder by reflow mounting or flow mounting.

In the thermistor element 65, external electrodes 69 and 70 for connection are formed only on the lower surface of the thermistor element 66. Therefore, since no fillet is generated, the mounting area can be reduced and high-density mounting can be achieved.

[0006]

However, the thermistor element 65 is conceived on the premise of a reflow mounting method using a solder paste or a flow mounting method using a molten solder. It has been difficult to achieve a higher density. That is, in the above-described mounting method, unless the solder lands formed on the printed circuit board or the like are printed with high accuracy, the surface mounting cannot be performed with high accuracy, but the printing accuracy of the solder lands is limited. That the thermistor element is displaced from the solder land on the board when the solder is melted, and that it is difficult to control the thickness of the solder, and thus it is difficult to suppress the mounting displacement of the thermistor element in the height direction. As a result, there has been a limit in improving the mounting density.

On the other hand, in recent years, a mounting method called bump mounting has become widespread as a mounting method capable of higher density mounting as compared with the reflow mounting method or the flow mounting method. Bump mounting means that a columnar or prismatic projection, usually called a bump made of Au or Sn-Pb, is interposed between a chip component and a substrate, and the bump and the substrate and the bump and the chip component are thermally bonded. This is a joining technique by crimping or eutectic alloying.

In bump mounting, bumps can be formed on a chip component or a substrate with high precision. Moreover,
As long as the bump can be formed with high precision, the chip component can be bonded to the substrate with high precision. In addition, fillets and the like due to the molten solder hardly occur.

However, the conventional thermistor element 65
Is based on the premise of the soldering method,
The underlying layer of the electrode was formed using a conductive paste. That is, in the thermistor body 65, the first and second electrodes 67 and 68 are formed by applying a conductive paste such as Ag to the lower surface 66a of the thermistor body 66 and baking.

Therefore, for example, Ni or Sn-P is formed on the electrode formed by applying and baking the conductive paste.
Even if an external electrode for connection to the outside is formed by plating b or the like, the underlying layer is formed of a thick film and the unevenness is large, so that the unevenness of the surface of the upper external electrode layer cannot be large. Did not get.

On the other hand, when the thermistor element is mounted on a substrate by bump bonding, the bump and the electrode of the thermistor element must be sufficiently adhered. Therefore, in the conventional thermistor element having the external electrode having large irregularities as described above, there is a problem that it is difficult to realize a highly reliable connection when mounted on a substrate by a bump bonding method.

[0012] Further, when mounting on a printed circuit board or a lead frame by bump bonding using the thermistor element 65, there is another problem that a complicated operation is required. This will be described with reference to FIG.

FIG. 18 is a partially cutaway side view for explaining a step of joining the lead frame 72 to the thermistor element 65 using the bumps 73. At the time of joining, it is necessary to place the bump 73 on the electrode 70 of the thermistor element 65 and heat the bump 73 while sandwiching the bump 73 between the electrode 70 and the lead frame 72. Accordingly, the bump 73 and the lead frame 72 are prepared, and the electrode 70 and the lead frame 72 are positioned so as to have a predetermined positional relationship.
A complicated series of operations such as holding the bump 73 between the two and heating while maintaining the holding state is forced.

In place of the lead frame 72,
Even when the thermistor element 65 is mounted on the printed circuit board by bump bonding, complicated positioning work and heating steps have to be performed as described above.

Further, as another method, the bump is first transferred to either the lead frame or the electrode of the thermistor element, and then the lead frame or the electrode is brought into contact with the bump transferred to the lead frame or the electrode and heated. A method is also conceivable. However, also in this method, the step of transferring the bump to the thermistor element or the lead frame must be performed in advance, so that the number of steps is increased and the joining operation is complicated. An object of the present invention is suitable for surface mounting by bump bonding,
An object of the present invention is to provide a thermistor element that can provide a junction having excellent reliability.

[0016]

According to a first aspect of the present invention, there is provided a thermistor element comprising: a thermistor element; first and second electrodes disposed on one surface of the thermistor element; And a bump formed on the second electrode.

In the thermistor element according to the present invention,
Since the second electrode is disposed to face the one surface of the thermistor body, it can be surface-mounted on a printed circuit board or the like using the thermistor body surface on which the first and second electrodes are arranged. That is, the thermistor element according to the first aspect of the present invention can be used as a surface mount thermistor element.

Further, in the thermistor element according to the present invention,
Since the bumps are formed on the first and second electrodes, the bumps can be bonded to a printed circuit board or a lead frame by bump bonding. That is, the thermistor element according to the present invention is surface-mountable by arranging the first and second electrodes on one surface of the thermistor body and bumps are formed on the first and second electrodes in advance. This simplifies the process of bonding to a lead frame, a printed circuit board, or the like by bump bonding.

Further, the thermistor element according to the present invention, as described in claim 2, further comprises a third electrode formed on the thermistor body surface opposite to the thermistor body surface on which the bump is formed. May be.

Similarly, the thermistor element according to the present invention may further include an internal electrode formed in the thermistor body. In this case, both the third electrode and the internal electrode may be provided.

In the present invention, the material forming the bump is not particularly limited as long as it has sufficient conductivity.
It is made of Au, Sn or an alloy containing any of these. Au, Sn or an alloy containing any of them has been conventionally used in bump bonding, and therefore, a conventional bump material can be easily used as the bump of the thermistor element according to the present invention in the same manner as in the conventional bump bonding method. Can be used as is.

In the thermistor element according to the present invention, preferably, at least the first and second electrodes are formed on the surface of the thermistor body on which the first and second electrodes are formed. An insulating resin layer is formed so as to cover the region.

By forming the insulating resin layer, it is possible to improve the moisture resistance and the temperature characteristics, and it is possible to suppress the adhesion of the solder bridge when used in the reflow mounting or the flow mounting method. Even when the facing distance of the second electrode is short, the possibility of a short circuit can be reduced.

The insulating resin layer is formed on the first and second electrodes on the surface of the thermistor body facing the first and second electrodes.
It is formed so as to cover at least the thermistor body surface other than the portion where the electrodes are formed, in this case,
The insulating resin layer may be formed so as to cover a part of the first and second electrodes. For example, the insulating resin layer may be formed so as to reach opposite end surfaces of the first and second electrodes and a part of the upper surfaces of the first and second electrodes. Further, the insulating resin layer may be formed so as to extend to a surface other than the thermistor body surface facing the first and second electrodes.

In the sixth aspect of the present invention, the second insulating resin layer is formed on the thermistor body surface opposite to the thermistor body surface on which the first and second electrodes are arranged to face each other. . As described above, by forming the insulating resin layers on the two surfaces, the moisture resistance and temperature characteristics of the thermistor body can be further improved.

As the material constituting the insulating resin layer, preferably, at least one resin selected from the group consisting of polyimide, epoxy resin and fluorine-based resin is used.

Further, in the thermistor element according to the present invention,
Preferably, the first and second electrodes are made of Cr, Ni, Ag, P
an electrode layer made of a metal selected from the group consisting of d, Pt, Ti and an alloy containing any of these, wherein the bumps
As described above, it is made of a metal selected from the group consisting of Au, Sn and alloys containing these metals. In this case, since the bump and the electrode layers of the first and second electrodes can be alloyed, the bonding strength between the bump and the first and second electrodes is further increased.

The first and second electrodes need not necessarily be formed on one surface of the thermistor body, and the first and second electrodes are opposed to each other on a plurality of surfaces of the thermistor body. It may be arranged.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIGS. 1A and 1B are a side view and a bottom view showing a negative temperature coefficient thermistor element according to a first embodiment of the present invention. The thermistor element 1 has a thermistor element 2 made of a sintered body having a negative resistance-temperature characteristic and configured using a plurality of transition metal oxides. The thermistor body 2 has a rectangular parallelepiped shape, and a first electrode 3 and a second electrode 4 are formed on a lower surface 2 a of the thermistor body 2.

In the present embodiment, the first electrode 3 is
Is formed so as to extend in the center direction from the edge on the end face 2b side. The second electrode 4 is formed to extend from the edge on the end face 2c side toward the center. No electrode is formed at the center of the lower surface 2a, and therefore, the first and second electrodes 3 and 4 are opposed to each other on the lower surface 2a.

The first and second electrodes 3 and 4 have contact layers 3a and 4a, respectively, and external electrode layers 3b and 4b formed on the contact layers. Contact layer 3a,
4a is made of a material that comes into ohmic contact with the thermistor body 2, and in this embodiment, is made of a Ni—Cr alloy. The contact layers 3a and 4a can be formed using other ohmic contact materials, for example, Cr or Ni, or an alloy thereof such as Cu or a Ni-Cu alloy. Further, the contact layers 3a, 4
a is formed by a thin film forming method such as vapor deposition, sputtering, electroless plating or electrolytic plating. In this embodiment, as described later, a Ni—Cr alloy is applied to the thermistor body 2 by vacuum vapor deposition. Contact layer 3
a, 4a are formed.

Accordingly, since the contact layers 3a and 4a are formed by the thin film forming method, the contact layers 3a and 4a have less irregularities than the thick film electrodes formed by applying and baking a conductive paste.

The external electrode layers 3b and 4b are provided to enhance the reliability of the electrical connection with the outside, and in this embodiment, are formed of a vacuum-deposited Ag film. However, the material constituting the external electrodes 3b and 4b may be formed of Au, Pd, or Ag-Pd, Au-Sn, or Au-S.
i, an alloy containing the above metal such as Au-Ge can be used.

In this embodiment, the first and second electrodes 3 and 4 are respectively composed of contact layers 3a and 4a made of a Ni—Cr alloy and external electrode layers 3b and 4b made of an Ag film. 4b, but the first and second electrodes 3 and 4 may be formed of a single layer.
However, a structure in which a plurality of layers using different metal materials are stacked as in the present embodiment is preferable because it has superior stability over time.

When the first and second electrodes 3 and 4 are composed of a single layer, for example, Cr, Ni, Ag, Pd, Pt, T
A metal material selected from the group consisting of i and an alloy containing any of these metals can be used. Further, the combination of the electrode materials in the case of the two-layer structure as in the present embodiment is not limited to the above-described embodiment, and any one of Ni, Cr, Cu, or an alloy containing these may be used as the first layer. Formed of a metal selected from the group consisting of Cr, Ni, Ag, Pd, Pt, T
i and a metal selected from the group consisting of alloys containing any of these metals.

The bumps 5 and 6 made of Au are formed on the external electrode layers 3b and 4b, respectively. The bumps 5 and 6 are connected to the external electrode layers 3b and 4b as described later.
Is formed by using a photolithography technique, and in the present embodiment, is configured to have a columnar shape.

The thickness of the bumps 5 and 6 depends on the size of the joint portion in order to prevent the bumps 5 and 6 from dropping and deforming during mounting, but is usually preferably 5 μm or more and 100 μm or less.

In the thermistor element 1 according to the present embodiment, as described above, since the bumps 5 and 6 are formed on the thermistor element 1 in advance, the bumps can be directly mounted on a printed circuit board or a lead frame. .

Further, since the first and second electrodes 3 and 4 are arranged opposite to each other on the lower surface 2a of the thermistor body 2, they can be easily mounted on the printed circuit board by using the bumps 5 and 6. Surface mountable.

In addition, since the contact layers 3a and 4a are formed by a thin film forming method and have a small amount of irregularities, the external electrode layers 3b and 4b formed on the contact layers 3a and 4a by vacuum deposition also have a small amount of irregularities. Therefore, the adhesion strength of the bumps 5, 6 formed by the photolithography technique to the external electrode layers 3b, 4b is also increased. Therefore, when bumps are mounted, the bonding strength between the bumps 5 and 6 and the first and second electrodes 3 and 4 is sufficiently large.

Next, an example of a manufacturing process of the thermistor element 1 will be described. Mn oxide, Ni oxide, and Co oxide were kneaded with a binder to prepare a slurry. Using this slurry, it is formed into a sheet by a doctor blade method, and the obtained sheet having a predetermined thickness is 65 × 65 mm
To obtain a plurality of green sheets.

Next, a plurality of green sheets are laminated,
After being pressed in the thickness direction, it was baked at a temperature of about 1300 ° C. for one hour to obtain a thermistor body wafer of 50 × 50 × 0.5 mm.

Next, a Ni-Cr alloy film having a thickness of 0.2 μm was formed on the thermistor body wafer by vacuum heating evaporation, and subsequently, an Au film having the same thickness of 0.2 μm was formed. Thus, a laminated metal film was formed on the thermistor body wafer.

Next, a photoresist was formed on the metal film by spin coating so as to have a thickness of 20 μm. Further, a photomask was placed on the photoresist, exposed, and the photoresist was developed using a solvent.

Next, the portion of the laminated metal film not covered with the photoresist was etched using an acid. That is, first, the Au film of the laminated metal film was etched with an acid, and then the Ni—Cr film was etched with the acid, leaving only the laminated metal film covered with the photoresist.

Further, by removing the resist,
A laminated metal film patterned on the thermistor body wafer was obtained. Next, a photoresist is applied to the surface of the thermistor body wafer by spin coating so as to have a thickness of 20 μm, and a photomask having a shape exposing the laminated metal film in a portion where a bump is to be formed is brought into contact. Exposure,
The photoresist was developed, and an Au bump was formed by electrolytic plating on the laminated metal film not covered by the photoresist.

Next, the thermistor body wafer was cut and diced so as to have a planar shape of 1.6 mm × 0.8 mm to obtain a large number of thermistor elements 1 shown in FIG.

In the thermistor body wafer, the smoothness of the thermistor body surface is increased by lapping or the like, for example, the surface roughness is set to Ra 0.46 μm or less.
As a result, the unevenness of the contact layer on the surface of the thermistor body and the bumps on the contact layer can be reduced, and the surface mounting bonding to a printed board or the like using the bump bonding method can be more effectively improved.

(Second Embodiment) FIGS. 2A and 2B
FIG. 3 is a side view and a bottom view showing a thermistor element according to a second embodiment of the present invention.

The thermistor element 11 is a thermistor element 1
2 is used. The thermistor body 12 has the same configuration as the thermistor body 2 used in the first embodiment.

On the lower surface 12a of the thermistor body 12, first and second electrodes 13 and 14 are formed. The first and second electrodes 13 and 14 are respectively
a, 14a, electrode layers 13b, 14b and bonding layer 13c,
14c. The contact layers 13a, 14a and the electrode layers 13b, 14b have the same configuration as the contact layers 3a, 4a and the external electrode layers 3b, 4b used in the first embodiment, respectively, and extend to the end faces 12b, 12c. Are not arranged. The difference is that the bonding layer 13
c, 14c.

In this embodiment, the bonding layers 13c and 14c are
It is formed by vacuum-depositing Ti. However, for the bonding layers 13c and 14c, in addition to Ti, C
It can be made of r, Ni, Ag, Pt, Pd or Al or an alloy containing any of these metals and Ti. In any case, since the bonding layers 13c and 14c are provided to enhance the bonding strength with the bumps 15 and 16, the structural material is the bumps 15 and 16
May be appropriately selected according to the material.

In the present embodiment, the bumps 15 and 16 are
It is made of Au similarly to the embodiment. The bonding layers 13c and 14c and the bumps 15 and 16 are formed by using the photolithography technique as described in the manufacturing method of the first embodiment.

Also in the thermistor element 11 of this embodiment, since the bumps 15 and 16 are formed on the thermistor element 11 in advance, the bumps 15 and 16 can be easily surface-mounted on a printed circuit board by a bump bonding method, and can be mounted on a lead frame. Bump bonding can be easily performed.

In addition, since the bumps 15 and 16 are made of Au and the bonding layers 13c and 14c are provided, the bumps 15 and 16 and the bonding layers 13c and 14c are alloyed at the time of bump bonding, and The joining strength between the first and second electrodes 13 and 14 and the first and second electrodes 13 and 14 is effectively increased.

(Third Embodiment) FIGS. 3A and 3B
FIGS. 7A and 7B are a side view and a bottom view for explaining a thermistor element according to a third embodiment of the present invention. FIGS.

In the thermistor element 21 of the third embodiment, the electrode layers 13b and 14b are made of Al instead of Ag, and the insulating resin layer 17 is provided on the lower surface 12a of the thermistor body 12. Except that
The configuration is the same as that of the thermistor element 11 of the second embodiment. Therefore, the same portions are denoted by the same reference numerals, and description thereof will be omitted.

In the thermistor element 21 of this embodiment, the electrode layers 13b and 14b are made of Al. However, as in the second embodiment, an Al film is formed by a thin film forming method such as vacuum evaporation. Therefore, since the bumps 15 and 16 are formed by the same thin film forming method, the adhesion strength between the bumps 15 and 16 and the first and second electrodes 13 and 14 is increased because there is little unevenness. obtain.

Although the insulating resin layer 17 is made of polyimide, the insulating resin layer 17 may be made of an insulating resin other than polyimide, for example, an epoxy resin or a fluorine resin.

In the third embodiment, since the insulating resin layer 17 made of polyimide is formed on the lower surface 12a of the thermistor body 12, the moisture resistance and the stability of temperature characteristics are improved. Moreover, since the insulating resin layer 17 is formed so as to cover at least the lower surface 12a of the thermistor body 12 other than the portions where the first and second electrodes 13 and 14 are formed, the first and second electrodes are formed. Undesired short circuit between the electrodes 13 and 14 is also prevented.

The insulating resin layer 17 is formed on the lower surface 12a of the thermistor body 12 by the first and second electrodes 13,
14 is formed so as to cover a portion other than the portion where the insulating resin layer 14 is formed.
May be formed so as to partially cover the end surfaces of the first and second electrodes 13 and 14 and a part of the first and second electrodes 13 and 14.

(Modification) FIGS. 4A and 4B show the third embodiment.
It is the side view and bottom view which show the modification of the thermistor element 21 which concerns on Example. In the thermistor element 31 shown in FIG.
Except that the insulating resin layer 18 of
The configuration is the same as that of the thermistor element 21 according to the third embodiment. The second insulating resin layer 18 is formed of the insulating resin layer 1.
Like in the case of 7, it is made of polyimide, but may be made of another insulating resin having excellent heat resistance and moisture resistance such as epoxy resin and fluorine resin. In the thermistor element 31, the upper surface 12d and the lower surface 1 of the thermistor body 12
Since the insulating resin layers 17 and 18 are formed on both of the layers 2a, the moisture resistance and the stability of temperature characteristics can be further improved.

In the thermistor elements of the first to third embodiments and the modifications described above, one bump 15, 16 is formed on each of the first and second electrodes 13, 14. The number of bumps formed in the thermistor element is not limited to this.

For example, as shown in FIG.
In 4, each of the plurality of bumps 15 and 16 may be dispersedly formed in a direction orthogonal to the direction in which the first and second electrodes 13 and 14 face each other. In this case, for example,
When bump bonding is performed by the lead frame, even if the position of the lead frame 32 (shown by imaginary lines) is shifted from the center in the width direction, the bump can be reliably bonded to the lead frame 32 by one of the bumps 16.

That is, the bump A is formed only at the center of the electrode 14.
(Shown by a broken line), the lead frame 3
If 2 is shifted in the width direction of the thermistor element 31, there is a possibility that bump bonding cannot be performed. On the other hand, as shown in FIG. 5, if a plurality of bumps 15 and 16 are formed, the electrodes 13 and 14 can be moved with respect to the lead frame 32 even if the position of the lead frame 32 in the width direction is shifted. Bump bonding can be performed reliably.

Also, as shown in FIG.
In each of the above, a plurality of bumps 15 and 16 may be arranged in the length direction of the thermistor element 1. In this case, even if the position of the lead frame is shifted in the length direction of the thermistor element, Bump bonding can be performed reliably.

In each of the electrodes 13 and 14, a plurality of bumps may be formed in both the length direction and the width direction of the thermistor element. In the thermistor element of the present invention, the dimensions of the bumps 15 and 16 cannot be uniquely determined because they differ depending on the dimensions of the electrode lands on the lead frame or the printed circuit board to be joined. When joining to a lead frame, referring to FIG. 5, if the width of the lead frame is b and the dimension of the bump along the width direction of the lead frame is a,
It is desirable that ≦ b.

That is, when a ≦ b as described above, as shown in FIG. 7A, the bump 15 is easily deformed by heating, and the lead frame 32 is securely joined to the electrode 13 of the thermistor element. be able to.

On the other hand, when the dimension of the bump 15 ′ in the lead frame width direction is larger than the dimension of the lead frame 32 in the width direction, that is, when a ≧ b, FIG.
As shown in FIG. 7, the width of the bump 15 ′ in the width direction is too large, and the bump 15 ′ is hardly deformed by heating, so that it may be difficult to perform the bump bonding between the lead frame 32 and the electrode 13.

Further, in the present invention, the shape of the bump formed integrally with the thermistor element is not limited to the above-mentioned columnar bumps 15 and 16, but may be a mushroom-like bump as shown in FIG. 33
Alternatively, FIG. 8 has a shape obtained by deleting a part of a sphere.
The bump 34 shown in FIG. In addition, the shape of the bump may be an appropriate shape such as a prism.

(Example of the Method for Joining a Thermistor Element of the Present Invention) The thermistor element according to the present invention can be mounted in a package by bump bonding to a lead frame, or can be directly surface mounted on a printed circuit board or the like. Can be done. This is shown in FIG. 9 and FIG.
0 is shown.

FIG. 9 is a partially cutaway side view showing a state where a lead frame is joined to the thermistor element according to the present invention. The thermistor element 1 is turned upside down from the state shown in FIG. 1, and the lead frames 32, 32 are brought into contact with the bumps 15, 16 as shown in FIG. 32 and the first and second electrodes 13 and 14 can be joined.

FIG. 10 is a partially cutaway side view showing a step of surface mounting the thermistor element 1 on the printed circuit board 37 from the lower surface 2a side of the thermistor body 2. Here, the electrode lands 37a, 3a on the printed circuit board 37 are used.
The bumps 15 and 16 may be brought into contact with 7b, and heating may be performed in that state.

As described above, the bumps 15 and 16 are previously formed on the thermistor element 1 side in any of the joining methods shown in FIGS. 9 and 10, so that the conventional bump joining is complicated. A complicated positioning operation can be omitted.

(Other Modifications) In the present invention, a third electrode is further formed on the thermistor body surface opposite to the thermistor body surface on which the first and second electrodes are formed. You may. A modification of the thermistor body on which such a third electrode is formed is shown in FIG.
1 to 13 are shown.

The thermistor elements shown in FIGS.
Except that a third electrode is provided, the configuration is almost the same as that of the thermistor element 1 shown in FIG. Therefore, the same portions are denoted by the same reference numerals, and description thereof will be omitted.

In the thermistor element 41 shown in FIGS. 11A to 11C, the thermistor element surface 2a opposite to the thermistor element surface 2a on which the first and second electrodes 3 and 4 are formed.
A third electrode 42 is formed so as to cover the entire surface of d. The third electrode 42 can be made of an appropriate metal material such as a NiCr alloy. In the thermistor element 41, the resistance between the first and second electrodes 3 and 4 can be reduced by forming the third electrode 42.

In the thermistor element 43 shown in FIGS. 12A to 12C, the third electrode 42 is provided on the thermistor body surface 2d.
A is formed. Here, the third electrode 42A is
It is formed so as to leave a gap region around the thermistor body surface 2d. That is, the third electrode 42A is formed on the thermistor body surface 2d so as not to reach the outer peripheral surface. Also in the thermistor element 43,
Since the third electrode 42A is formed, the resistance of the thermistor element 43 can be reduced.

Further, in the thermistor element 43, since the third electrode 42A is formed so as not to reach the outer peripheral surface of the element body surface 2d, cutting when the thermistor element 43 is cut out from the mother thermistor element is performed. Variations in resistance value due to variations can be suppressed, and a thermistor element having a desired resistance value can be provided with higher accuracy.

In the thermistor element 44 shown in FIG. 13, third electrodes 45a and 45b are formed on the thermistor body surface 2d so as to face each other. Third electrode 45
a and 45b are formed so as not to reach the full width of the thermistor body surface 2d. Also in the thermistor element 44, the resistance can be reduced by forming the third electrodes 45a and 45b.

FIGS. 14 to 16 are views for explaining still another modification of the thermistor element according to the present invention.
Here, at least one internal electrode is formed in the thermistor body. The structures shown in FIGS. 14 to 16 are the same as the thermistor element 1 shown in FIG. 1 except that the internal electrodes are formed, and therefore, the same portions are denoted by the same reference numerals. Thus, the description thereof will be omitted.

In the thermistor element 46 shown in FIGS. 14A to 14C, an internal electrode 47 is formed at a predetermined height position in the thermistor body 2 so as to reach the outer peripheral surface of the thermistor body 2. ing. By forming the internal electrode 47,
The resistance value between the first and second electrodes 3 and 4 can be reduced, so that the resistance can be reduced, and variation in the resistance value can be reduced.

In the thermistor element 48 shown in FIGS. 15A to 15C, a pair of internal electrodes 49a and 49b are opposed to each other at a plurality of height positions in the thermistor body 2.
Are formed. The internal electrodes 49a and 49b are
It is formed so as not to reach the outer peripheral surface of the thermistor body 2.

By forming the internal electrodes 49a and 49b, the resistance of the thermistor element 48 can be reduced and the variation in the resistance value can be suppressed. In addition, in the thermistor element 48, since the internal electrodes 49a and 49b are formed so as not to reach the outer peripheral surface of the thermistor body 2, the resistance due to the variation in cutting when the thermistor element 48 is cut out from the mother thermistor element. The value does not easily fluctuate.

In the thermistor element 50 shown in FIGS. 16A to 16C, the plurality of internal electrodes 51
Are arranged to overlap each other. Further, the plurality of internal electrodes 51 are alternately formed on the end face 2a or the end face 2b.
And extends into the thermistor body 2.

In the thermistor element 50 as well, the formation of the plurality of internal electrodes 51 can reduce the resistance and reduce the variation in the resistance value. Further, any of the third electrodes 42, 42A, 45a, 45b shown in FIGS. 11 to 13 and the internal electrodes 47, 49a, 49b,
Any one of 51 may be used in any combination. Further, also in the thermistor element shown in FIGS. 11 to 16, the above-described first and second insulating resin layers may be further formed.

[0087]

According to the first aspect of the present invention, the first and second electrodes are arranged on one surface of the thermistor body so as to face each other. It can be surface-mounted on, for example, a printed circuit board or the like from the side where the two electrodes are opposed to each other.

Moreover, since the bumps are formed on the first and second electrodes, the bumps can be surface-mounted on the printed circuit board without any complicated positioning operation. Further, a lead frame can be joined to the thermistor element according to the present invention by bump joining without using a complicated positioning operation using the bumps.

Further, the third electrode is formed on the thermistor body surface opposite to the thermistor body surface on which the bumps are formed, or as described in claim 3. When the structure in which the internal electrode is formed in the thermistor body is adopted, the resistance between the first and second electrodes can be reduced, and the resistance can be reduced. It becomes possible to suppress.

According to the fourth aspect of the present invention, the bump is
u, Sn or a metal selected from the group consisting of alloys containing any of these, has excellent conductivity, and uses a conventionally known bump material to form a thermistor element according to the present invention. obtain.

According to the fifth aspect of the present invention, since the insulating resin layer is formed on the surface of the thermistor body, a thermistor element having excellent moisture resistance and temperature characteristics can be provided. In the invention according to claim 6, the second insulating resin layer is formed also on the thermistor body surface opposite to the thermistor body surface on which the first and second electrodes are formed. Moisture resistance and temperature characteristics can be further improved.

According to the invention described in claim 8, the first and second electrodes are formed of Cr, Ni, Ag, Pd, Pt, Ti, and Al.
And an electrode layer made of a metal selected from the group consisting of alloys containing any of these, wherein the bumps are made of A
Since the electrode layer is made of a metal selected from the group consisting of u, Sn, and an alloy containing any of these metals, the electrode layer is alloyed with the bump when heated at the time of bump bonding. Therefore, the bonding strength between the bump and the first and second electrodes can be effectively increased, and a more excellent thermistor element can be provided in the reliability of electrical connection.

[Brief description of the drawings]

FIGS. 1A and 1B are a side view and a bottom view of a thermistor element according to a first embodiment of the present invention.

FIGS. 2A and 2B are a side view and a bottom view of a thermistor element according to a second embodiment of the present invention.

FIGS. 3 (a) and (b) respectively show a third embodiment of the present invention.
The side view and bottom view of the thermistor element which concerns on Example of FIG.

4A and 4B are a side view and a bottom view showing a modified example of the thermistor element according to the present invention.

FIG. 5 is a side view and a bottom view illustrating another modified example of the thermistor element according to the present invention and illustrating a structure in which a plurality of bumps are formed in a width direction.

FIG. 6 is a side view showing still another modified example of the thermistor element according to the present invention and illustrating a structure in which a plurality of bumps are formed on each electrode in a length direction of the element.

FIGS. 7A and 7B are cross-sectional views for explaining a preferable relationship between a dimension in a width direction of the lead frame and a dimension of a bump when the lead frame is joined to the lead frame.

FIGS. 8A and 8B are perspective views for explaining another example of the shape of the bump used in the present invention.

FIG. 9 is a side view for explaining a step of joining a lead frame to a thermistor element according to the present invention.

FIG. 10 is a partially cutaway side view for explaining a step of mounting the thermistor element according to the present invention on a printed circuit board.

FIGS. 11A to 11C are side views for explaining other modified examples of the thermistor element according to the present invention;
Plan view and bottom view.

FIGS. 12A to 12C are side views for explaining another modification of the thermistor element according to the present invention;
Plan view and bottom view.

FIGS. 13A to 13C are side views for explaining another modification of the thermistor element according to the present invention;
Plan view and bottom view.

FIGS. 14A to 14C are side views for explaining another modification of the thermistor element according to the present invention;
Plane sectional view and bottom view.

FIGS. 15A to 15C are a side sectional view, a plan sectional view, and a bottom view for explaining still another modification of the thermistor element of the present invention.

FIGS. 16A to 16C are a side sectional view, a plan sectional view, and a bottom view for explaining still another modified example of the thermistor element of the present invention.

FIG. 17 is a side view showing an example of a conventional thermistor element.

FIG. 18 is a side view for explaining a step of bump bonding a lead frame to a conventional thermistor element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Thermistor element 2 ... Thermistor body 2a ... Lower surface 2d ... Thermistor body surface 3, 4 ... First and second electrodes 3a, 4a ... Contact layers 3b, 4b ... External electrode layer 11 ... Thermistor element 12 ... Thermistor body 12a: Lower surface 13, 14: First and second electrodes 13a, 14a: Contact layers 13b, 14b: Electrode layers 13c, 14c: Bonding layer 15: Bump 16: Bump 17: Insulating resin layer 18: Second insulation Conductive resin layer 21 ... Thermistor element 31 ... Thermistor element 41 ... Thermistor element 42 ... Third electrode 43 ... Thermistor element 42A ... Third electrode 44 ... Thermistor element 45a, 45b ... Third electrode 46 ... Thermistor element 47 ... Inside Electrode 48: Thermistor element 49a, 49b: Internal electrode 50: Thermistor element 51: Internal electrode

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[Procedure amendment]

[Submission date] June 25, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0083

[Correction method] Change

[Correction contents]

[0083] In the thermistor element 48 shown in FIG. 15 (a) ~ (c) , the position a plurality of heights in the thermistor element 2 Noso
In each case, a pair of internal electrodes 49 are opposed to each other.
a, 49b are formed. The internal electrodes 49a,
49b is formed so as not to reach the outer peripheral surface of the thermistor body 2.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Fig. 5

[Correction method] Change

[Correction contents]

Figure 5 shows another variation of the thermistor element according to the present invention, the bottom view for illustrating a structure in which a plurality of bumps are formed in the width direction.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] Fig. 6

[Correction method] Change

[Correction contents]

It illustrates yet another variation, the bottom view for describing the structure formed in the length direction of the plurality of bumps elements on each electrode of the thermistor element according to the present invention; FIG.

[Procedure amendment 4]

[Document name to be amended] Drawing

[Correction target item name] FIG.

[Correction method] Change

[Correction contents]

FIG.

[Procedure amendment 5]

[Document name to be amended] Drawing

[Correction target item name] FIG.

[Correction method] Change

[Correction contents]

FIG. 16

Claims (8)

[Claims] 1. A device comprising: a thermistor element; first and second electrodes arranged on one surface of the thermistor element to face each other; and bumps formed on the first and second electrodes. Thermistor element. 2. The thermistor element according to claim 1, further comprising a third electrode formed on a thermistor body surface facing the thermistor body surface on which the bump is formed. 3. The thermistor element according to claim 1, further comprising an internal electrode formed in said thermistor body. 4. The thermistor element according to claim 1, wherein the bump is made of a metal selected from the group consisting of Au, Sn and an alloy containing any of them. 5. An insulating resin layer formed so as to cover at least a region other than the first and second electrodes on a surface of the thermistor body on which the first and second electrodes are formed. The thermistor element according to claim 1, further comprising: 6. The thermistor according to claim 5, further comprising a second insulating resin layer formed on a thermistor body surface opposite to the thermistor body surface on which the first and second electrodes are formed. element. 7. The thermistor element according to claim 5, wherein said insulating resin layer is made of one kind of resin selected from the group consisting of polyimide, epoxy resin and fluorine-based resin. 8. The first and second electrodes are formed of Cr, Ni, Ag,
An electrode layer made of a metal selected from the group consisting of Pd, Pt, Ti, Al and an alloy containing any of these, wherein the bump is selected from the group consisting of Au, Sn and an alloy containing any of these. Thermistor element according to claim 1, wherein the thermistor element is made of a metal.