JP2012159310A - Thin film thermistor sensor and manufacturing method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin film thermistor sensor that permits satisfactory joining of leads by laser-welding without using a bump, and a manufacturing method for the same.SOLUTION: In a thin film thermistor sensor comprising an insulative substrate 2, a thermistor thin film 3 patterned over the upper face of the insulative substrate 2, a pair of electrodes 4 patterned from the upper face of the insulative substrate 2 to the upper face of the thermistor thin film 3, and a pair of leads 5 connected to the pair of electrodes 4, wherein the leads 5 in a state of being fitted into groove parts 4c formed in the electrodes 4 are laser-welded in the contact parts between flanks and the groove parts 4c.

Description

  The present invention relates to a thin film thermistor sensor used for sensors such as a temperature sensor and a flow rate sensor, and a method for manufacturing the same.

  For example, there is a thermistor chip made of an oxide semiconductor sintered body having a large negative temperature coefficient as a temperature sensor and a flow rate sensor for information equipment, communication equipment, medical equipment, housing equipment, automobile transmission equipment, and the like. A thin film thermistor sensor using the thermistor chip has a terminal electrode, and a lead wire or a lead frame (hereinafter referred to as a lead) is attached to the electrode surface by soldering, bumping, conductive adhesive or welding. The structure is known.

  For example, Patent Document 1 proposes a thin film temperature sensor in which a bump is formed on an electrode using a wire bump method in order to connect a heat-sensitive film and a lead wire, and then the lead wire is connected to the bump by laser welding. ing.

JP 2008-241666 A

The following problems remain in the conventional technology.
That is, in the above conventional technique, bumps are formed on electrodes, and leads are placed thereon for laser welding. However, the thermistors are covered so as to cover the leads in order to enhance heat resistance, heat stress, and tensile stress. When the chip surface is molded with a ceramic mold material or the like, it is necessary to cover the bump + lead height, which increases the capacity of the thermistor chip and increases the heat capacity, leading to a delay in the thermal response speed. . In particular, this tendency becomes more prominent as the chip size of the thermistor chip decreases.
When laser welding is performed, laser light is irradiated from above the lead. However, when the lead is thick (thick), a material that hardly absorbs laser light or a reflective plating film (a film of Cu, Au, Ag, etc.) is used. When it is applied to the surface, it is difficult to adjust the output of the laser beam, and the heat energy cannot be absorbed by the bumps, reaching the substrate of the chip, and there is a problem that peeling between the substrate and the electrode occurs.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a thin film thermistor sensor capable of satisfactorily joining leads by laser welding without using bumps and a method for manufacturing the same.

  The present invention employs the following configuration in order to solve the above problems. That is, the thin film thermistor sensor of the present invention includes an insulating substrate or a substrate having an insulating layer formed on a surface thereof, a thermistor thin film patterned on the insulating layer or the upper surface of the insulating substrate, and the insulating layer or the insulating substrate. A pair of electrodes patterned from the upper surface to the upper surface of the thermistor thin film, and a pair of leads connected to the pair of electrodes, and the leads are fitted into grooves formed in the electrodes. In this state, laser welding is performed at a contact portion between the side surface and the groove portion.

  The method for producing a thin film thermistor sensor of the present invention is a method for producing the thin film thermistor sensor of the present invention, wherein the thermistor thin film is formed on the upper surface of the insulating substrate and the upper surface of the insulating layer of the substrate. Patterning a pair of electrodes from the upper surface of the insulating layer or the insulating substrate to the upper surface of the thermistor thin film, and a lead connecting step of connecting a pair of leads to the pair of electrodes. The lead connection step includes a step of forming a groove portion in the pair of electrodes, and a step of laser welding at a contact portion between the side surface and the groove portion in a state where the lead is fitted in the groove portion. It is characterized by that.

  In these thin film thermistor sensors and manufacturing methods thereof, the lead is laser welded at the contact portion between the side surface and the groove while being fitted in the groove formed in the electrode. The heat capacity can be reduced, and the electrode is melted and joined by laser welding at the contact portion between the lead side surface and the groove, thereby preventing damage to the electrode and the substrate without melting the substrate immediately below. it can. In addition, even a lead material having a low laser beam absorption rate melts an electrode having a laser beam absorption rate better than that of the lead material, so that welding becomes possible and the degree of freedom of selection of the lead material is increased. Further, the contact area between the lead and the electrode is increased to obtain a high bonding strength, and the lead can be accurately positioned and welded.

In the thin film thermistor sensor of the present invention, the groove portion is formed in a rectangular cross section, and the lead is a rectangular bar-like lead frame having substantially the same cross sectional shape that can be fitted in the groove portion. .
That is, in this thin film thermistor sensor, since the lead is a rectangular bar-shaped lead frame having substantially the same cross-sectional shape that can be fitted into the groove having a rectangular cross section, the lead can be positioned more accurately in the groove and the lead. Even in the state of fitting, the upper surface becomes flat, and the height can be further reduced.

The thin film thermistor sensor according to the present invention is characterized in that at least the inner wall of the groove of the electrode is formed of Ni.
That is, in this thin film thermistor sensor, since at least the inner wall of the groove portion of the electrode is made of Ni, the groove portion is well dissolved by Ni having a high laser light absorption rate, so that the lead having a low laser light absorption rate can be obtained. Even if the material or the surface is covered with a plating film having a low absorption rate of laser light such as Ag, Au, or Cu, the lead can be satisfactorily bonded.

The present invention has the following effects.
That is, according to the thin film thermistor sensor and the manufacturing method thereof according to the present invention, the lead is laser-welded at the contact portion between the side surface and the groove portion in a state of being fitted in the groove portion formed in the electrode. In addition, the heat capacity can be reduced, and the thermal response can be improved. Moreover, it is possible to satisfactorily bond even a lead material having a low laser light absorption rate while suppressing damage to the electrode and the substrate. Therefore, the present invention is suitable as a thin film thermistor sensor used in a copying machine or the like that requires bonding strength, high-speed response, high heat resistance, and the like.

1 is a perspective view showing a thin film thermistor sensor excluding an insulating coating layer in one embodiment of a thin film thermistor sensor and a manufacturing method thereof according to the present invention. In this embodiment, it is sectional drawing which shows the lead periphery at the time of laser welding. In this embodiment, it is a perspective view which shows the production | generation process in a wafer form, a groove part formation process, and the state cut out to the chip shape. In this embodiment, it is a perspective view which shows a lead insertion process and a laser welding process.

  Hereinafter, an embodiment of a thin film thermistor sensor and a manufacturing method thereof according to the present invention will be described with reference to FIGS. In each drawing used for the following description, the scale of each member is appropriately changed in order to make each member or configuration recognizable.

  As shown in FIG. 1, the thin film thermistor sensor 1 of the present embodiment includes an insulating substrate 2 made of an alumina substrate, a thermistor thin film 3 patterned on the upper surface of the insulating substrate 2, and a thermistor thin film 3 from the upper surface of the insulating substrate 2. A pair of electrodes 4 patterned over the upper surface and a pair of leads 5 connected to the pair of electrodes 4 are provided.

The thermistor thin film 3 is made of, for example, Mn—Co based composite metal oxide (for example, Mn ₃ O ₄ —Co ₃ O ₄ based composite metal oxide) or Mn—Co based composite metal oxide with Ni, Fe, Cu. It is a composite metal oxide film made of a composite metal oxide (for example, Mn ₃ O ₄ —Co ₃ O ₄ —Fe ₂ O ₃ -based composite metal oxide) containing at least one element.

The thermistor thin film 3 of this embodiment is formed on the upper surface of the insulating substrate 2 in a substantially square shape in plan view by a sputtering method.
The thermistor thin film 3 has the properties of a semiconductor, and has a negative characteristic in which the resistance decreases as the temperature rises, that is, a so-called NTC thermistor (Negative Temperature Coefficient Thermistor).

The lead 5 is laser welded at least at a contact portion between the side surface and the groove 4c in a state where the lead 5 is fitted in the groove 4c formed in the electrode 4.
At least the inner wall of the groove 4c of the electrode 4 is made of Ni. That is, the pair of electrodes 4 includes a pair of Pt bonding layers patterned with Pt from the upper surface of the insulating substrate 2 to the upper surface of the thermistor thin film 3, and a pair of Ni formed with Ni on these Pt bonding layers. The groove portion 4c is formed in the Ni plating layer.

  The pair of Pt bonding layers is formed from the upper surface of the thermistor thin film 3 to the upper surface of the insulating substrate 2. The pair of Pt bonding layers is an underlayer for the pair of Ni plating layers, and the bonding strength with the material of the surface to be formed (in this embodiment, the insulating substrate 2 and the thermistor thin film 3) is Ni plating layer. Higher than. Note that the thickness of the Pt bonding layer is set to 100 to 1000 nm. The thickness of the Ni plating layer is about 100 μm.

Further, the electrode 4 of this embodiment includes a pair of comb teeth 4a formed on the upper surface of the thermistor thin film 3 and facing each other, and an electrode pad section 4b that is a pair of lead electrodes connected to each comb tooth 4a, have. The groove portion 4c is formed in a line shape or a belt shape corresponding to the lead 5 in the pair of electrode pad portions 4b. Moreover, the groove part 4c is formed in the cross-sectional rectangle shape, as shown in FIG.
The lead 5 is a square bar-like lead frame made of, for example, stainless steel (SUS) and having substantially the same cross-sectional shape that can be fitted into the groove 4c. A plating film made of Ag, Au, Cu or the like is formed on the surface of the lead 5.

Further, in the thin film thermistor sensor 1, SiO ₂ film 6 is formed as a protective film on the thermistor thin film 3 and the comb teeth 4a. The thickness of the SiO ₂ film 6 is set to 100 to 1000 nm, for example. Further, the entire upper surface of the sensor, that is, the SiO ₂ film 6 and the electrode 4 to which the lead 5 is welded are sealed with an insulating coating layer (not shown).
This insulating coating layer is a protective film that seals the thermistor thin film 3 and the comb tooth portion 4a inside, and is formed, for example, by firing and molding a ceramic mold material or glass paste dropped on the surface. This insulating coating layer is set to a thickness of 10 μm, for example.

  Next, a manufacturing method of the thin film thermistor sensor 1 configured as described above will be described with reference to FIGS.

  First, as shown in FIG. 3A, a thin film forming process is performed for patterning the thermistor thin film 3 on the surface of the wafer W of the insulating substrate 2. That is, the above-described composite metal oxide film is formed on the entire surface of the insulating substrate 2 by a sputtering method under predetermined sputtering conditions.

  Subsequently, a photoresist film is patterned on the upper surface of the composite metal oxide film on the region where the thermistor thin film 3 is formed by photolithography. Then, using the photoresist film as a mask, the unmasked composite metal oxide film is selectively removed by wet etching using a predetermined solution. Then, the photoresist film used as the mask is removed. As a result, the thermistor thin film 3 having a substantially square shape in plan view can be patterned on the upper surface of the insulating substrate 2. Thereafter, annealing is performed at a predetermined temperature and for a predetermined time as necessary to improve heat resistance.

  Next, Pt, which becomes a Pt bonding layer under a predetermined sputtering condition, is formed by sputtering from the upper surface of the thermistor thin film 3 to the upper surface of the insulating substrate 2. Subsequently, a photoresist film is patterned on the upper surface of Pt by a photolithography technique in a region where a pair of electrodes is to be formed. Then, Pt that is not masked is selectively removed by dry etching using the photoresist film as a mask. Then, the photoresist film used as the mask is removed. Thereby, a comb-like electrode can be patterned on the upper surface of the thermistor thin film 3.

Subsequently, in order to prevent deposition on the comb teeth portion 4a and the groove portion 4c during Ni plating, a plating resist is applied, and Ni plating is performed on the electrode pad portion 4b of the Pt bonding layer by using a sulfamic acid Ni plating bath. A film of about 100 μm is formed to form a Ni plating layer. At this time, by forming a plating resist on the electrode pad portion 4b in a linear or strip shape, a portion where Ni is not deposited in a linear or strip shape is formed on the electrode pad portion 4b. Then, when the plating resist is removed, as shown in FIG. 3B, a pair of electrodes 4 having a linear or strip-like groove 4c is formed. The cross-sectional shape of the groove 4c is rectangular, and the cross-sectional size is set to 0.1 mm × 0.1 mm, for example. Further, a SiO ₂ film 6 is patterned as a protective film on the thermistor thin film 3 and the comb tooth portion 4a.

Thereafter, as shown in FIG. 3C, dicing is performed to cut out into chips.
Next, as shown in FIG. 4A, the tip portions of the pair of leads 5 that are rectangular bar-shaped lead frames having a rectangular cross section are fitted into the groove portions 4 c of the pair of electrodes 4. The cross-sectional size of the lead 5 is set to, for example, 0.1 mm × 0.1 mm corresponding to the groove 4c. The lead 5 has an Ag plating film formed on the surface.

Next, as shown in FIG. 4B, laser welding is performed at the contact portion between the side surface and the groove 4c with the lead 5 fitted in the groove 4c.
At this time, the laser light L is, for example, a laser beam having a wavelength of 1064 nm or 532 nm, and condensed and irradiated with a wide spot diameter in consideration of the width of the lead 5 and the groove 4c as shown in FIG. For example, when the width of the lead 5 and the groove 4c is set to 0.1 mm, the laser beam is focused and irradiated on a rectangular spot of 0.2 mm × 0.2 mm. As a result, both inner walls of the groove 4c in contact with both side surfaces of the lead 5 absorb and melt the laser light L, and this melting heat causes a plating film of Ag, Au, Cu or the like having a low laser absorption rate on the surface of the lead 5 The both sides of the lead 5 are joined to the electrode 4.

  Thereafter, a thin film thermistor sensor 1 is manufactured by dropping a ceramic mold material or glass paste onto the surface with a dispenser so as to cover the entire surface including the tip joint portion of the lead 5 and firing, and molding as an insulating coating layer. The

  As described above, in the thin film thermistor sensor 1 and the manufacturing method thereof according to the present embodiment, the lead 5 is laser-welded at the contact portion between the side surface and the groove portion 4c in a state where the lead 5 is fitted in the groove portion 4c formed in the electrode 4. Even if it is molded, the height is lower than that of the prior art, and the heat capacity can be reduced, and the electrode 4 is melted and joined by laser welding at the contact portion between the side surface of the lead 5 and the groove 4c, so that the insulating substrate directly below Damage to the electrode 4 and the insulating substrate 2 can be suppressed without melting up to 2. Further, even if the lead material has a low absorption rate of the laser beam L, the electrode 4 having a higher absorption rate of the laser beam L than that of the lead material is melted, so that welding becomes possible and the degree of freedom in selecting the lead material is high. Become. Further, the contact area between the lead 5 and the electrode 4 is increased, so that a high bonding strength can be obtained, and the lead 5 can be accurately positioned and welded.

In addition, since the lead 5 is a square rod-like lead frame having substantially the same cross-sectional shape that can be fitted into the groove 4c having a rectangular cross section, the lead 5 can be positioned more accurately in the groove 4c and the lead 5 can be positioned. Even in the fitted state, the upper surface becomes flat and the height can be further reduced.
Further, since at least the groove 4c of the electrode 4 is made of Ni, the groove 4c is well dissolved by Ni having a high absorption rate of the laser beam L, so that a lead material or surface having a low absorption rate of the laser beam L can be obtained. Even if it is covered with a plating film having a low absorptance of laser light L such as Ag, Au, or Cu, the lead 5 can be satisfactorily bonded.

  The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

For example, in the above embodiment, the case where an insulating substrate of an alumina substrate is used is taken as an example. However, the present invention is not limited to this, and an insulating substrate such as a quartz substrate or a SiO ₂ insulating layer formed by thermal oxidation is formed on the surface. A silicon substrate or another semiconductor substrate may be used. Further, the lead is exemplified by the case of using a lead frame made of a stainless material, but the lead is not limited to this and may be made of Kovar or Invar material.

  DESCRIPTION OF SYMBOLS 1 ... Thin film thermistor sensor, 2 ... Insulating substrate, 3 ... Thermistor thin film, 4 ... Electrode, 4c ... Groove part, 5 ... Lead, L ... Laser beam

Claims (4)

An insulating substrate or a substrate with an insulating layer formed on the surface;
A thermistor thin film patterned on the upper surface of the insulating layer or the insulating substrate;
A pair of electrodes patterned from the upper surface of the insulating layer or the insulating substrate to the upper surface of the thermistor thin film;
A pair of leads connected to the pair of electrodes,
A thin film thermistor sensor, wherein the lead is laser welded at a contact portion between a side surface and the groove portion in a state where the lead is fitted in the groove portion formed in the electrode. The thin film thermistor sensor according to claim 1,
The groove is formed in a rectangular cross section,
The thin film thermistor sensor, wherein the lead is a square bar-like lead frame having substantially the same cross-sectional shape that can be fitted into the groove. The thin film thermistor sensor according to claim 1 or 2,
A thin film thermistor sensor, wherein at least an inner wall of the groove of the electrode is made of Ni. A method for producing a thin film thermistor sensor according to any one of claims 1 to 3,
Patterning a thermistor thin film on the upper surface of the insulating layer of the substrate having an insulating layer formed on the upper surface or surface of the insulating substrate;
Patterning a pair of electrodes from the upper surface of the insulating layer or the insulating substrate to the upper surface of the thermistor thin film;
A lead connection step of connecting a pair of leads to the pair of electrodes,
The lead connection step includes a step of forming a groove portion in the pair of electrodes, and a step of laser welding at a contact portion between the side surface and the groove portion with the lead fitted in the groove portion. A method for manufacturing a thin film thermistor sensor.

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