JPH10125508A - Chip thermistor and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a chip thermistor and a method for manufacturing it which is easy to handle at manufacture and which has less variation in resistance value. SOLUTION: In a chip thermistor, a thin film thermistor is formed on a trapezoid-shaped insulating substrate 1. In the thin film thermistor, a pair of electrode pads 4 are formed, an insulating layer 5a is formed between the electrode pads 4, leader electrode parts 6a and 6b extending over the electrode pads 4 are formed so as to be in contact with the insulating layer 5a, a thermosensitive film 7a is formed between the leader electrode parts 6a and 6b, and the thermosensitive film 7a is covered with a glass protective film 9a. U-shaped terminal electrode parts are formed on side parts of the insulating substrate 1 while being in contact with the leader electrodes 6 and 6b, respectively, and the terminal electrode part comprises four layers of a lower metal thin film layer 15, intermediate metal thin film layers 16 and 17 and a surface metal thin film layer 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chip thermistor and a method for manufacturing the same, and more particularly, to a chip thermistor suitable for mounting as a surface mount component on a printed circuit board and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, there are various structures and manufacturing methods for a chip resistor as one of chip-shaped electronic components. For example, in the case of a thick film type chip resistor, a resistive film is printed on one substrate and baked, and then the substrate is divided into rods for forming end electrodes, and Ag-P is formed on the side surface thereof.
A structure is known in which d is applied and baked, and thereafter, the rod-shaped substrate is separated and divided into chips and plated with Ni, Pb-Sn, or the like.

FIG. 9 shows another conventional chip resistor disclosed in Japanese Patent Publication No. 5-36921. This chip resistor will be described with reference to FIGS.
0 indicates that a plurality of slits 21 are formed in advance,
A substrate in which a plurality of rod-shaped portions 22 are formed between the substrates, a so-called perforated insulating substrate 20 is used. As shown in FIG. 1B, a resistive thick film 23 is formed on the perforated insulating substrate 20, and sputtering, ion plating, P -By thin film technology such as CVD
An end electrode 24 made of a laminated metal thin film layer is formed.

As shown in FIG. 1C, the end electrode 24 is composed of a lower metal thin film layer 24a and an intermediate metal thin film layer 24b.
And a surface metal thin film layer 24c. The lower metal thin film layer 24a is formed of Cr, Cr alloy, Ti or the like having good adhesion to the resistive thick film 23, and the middle metal thin film layer 24b is formed of Ni, NiCr alloy, AgNi alloy, which can secure soldering resistance. The surface metal thin film layer 24c is formed of an SnNi alloy or the like, and is formed of Ag, Pb-Sn, Sn, or the like, which is easily compatible with solder. afterwards,
After forming the protective layer following the end electrode 24, the rod-shaped portion 2 is formed.
2 is cut into a plurality of pieces to form a chip resistor.

[0005]

However, as shown in FIG. 9, in the manufacturing method using a perforated insulating substrate in which slits are formed in advance, the work is performed with great care for cracking of the substrate during the work. However, there is a disadvantage that mass productivity and lot management are complicated. Also, a method of forming a large number of slits on a single insulating substrate and manufacturing from a single substrate having an apparently large number of rod-shaped portions generally involves forming a slit in a green sheet state and firing the green sheet. In addition, it is difficult to increase the dimensional accuracy due to shrinkage or warpage during firing, and it is difficult to form a particularly thin substrate.

Further, by using a substrate having a slit formed thereon, when patterning is performed by a photolithography technique in a subsequent step, the thickness of the photoresist film at the edges and the center of the slit portion and the rod-like portion is reduced. There is a disadvantage that variation occurs. There is a disadvantage that patterning becomes more difficult as the width of the rod-shaped portion becomes smaller. Such variations in the photolithography process appear as variations in the characteristics of the device, and cause a reduction in yield. Furthermore, the substrate on which the slit is formed has a disadvantage that the substrate strength is weak,
There is a disadvantage that it is easily broken during handling during the process.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a chip thermistor which is easy to handle at the time of manufacture and has a small variation in resistance value, and a method of manufacturing the same. And Also, the present invention
By forming an extremely small thin-film thermistor with high dimensional accuracy and reliability on an insulating substrate and forming electrodes on the side surface, handling during mounting on a printed circuit board, solder erosion resistance, solder wettability and peeling It is an object of the present invention to provide a chip thermistor having high strength and a method for manufacturing the same.

[0008]

Means for Solving the Problems The present invention has been made to achieve the above-mentioned object, and the invention according to claim 1 has an insulating substrate and a pair of electrodes formed on the insulating substrate. A pad, an insulating film formed on an insulating substrate surface between the electrode pads, a pair of external lead electrodes extending on the electrode pads in contact with the insulating film, and the external lead electrodes having the insulating film as a base. A heat-sensitive film formed therebetween, a thin-film thermistor composed of a protective film covering the heat-sensitive film, and an end electrode electrically connected to the external extraction electrode formed on a side surface of the insulating substrate, A chip thermistor characterized in that the end electrode is formed of four metal thin-film layers and covers a side surface of the insulating substrate and has a substantially U-shape. The chip thermistor of the present invention is formed on a trapezoidal insulating substrate. A substantially U-shaped end electrode is formed. And it is suitable for mounting on a printed board of a chip-like parts small thin film thermistor is formed,
Also, the bottom side surface of the trapezoidal insulating substrate is chamfered,
Disconnection of the end electrode can be reduced.

According to a second aspect of the present invention, in the chip thermistor according to the first aspect, the pair of electrode pads is made of any one of titanium, chromium, nickel, molybdenum, tungsten, and a Ni—Cr alloy. A metal thin film layer formed by sequentially depositing any one of palladium, a palladium alloy, and gold on the insulating substrate surface, wherein the external extraction electrode is made of at least one metal of platinum, palladium, and a palladium alloy. By being a chip thermistor, the above problem could be solved.

According to a third aspect of the present invention, in the chip thermistor according to the first aspect, the end electrodes are sequentially formed from a lower metal thin film layer of chromium, a middle metal thin film layer of copper or nickel, and nickel from an insulating substrate surface. The above problem was solved by a chip thermistor characterized by comprising a metal thin film layer composed of an electroplating layer and a metal thin film layer of tin or a tin-lead alloy.

According to a fourth aspect of the present invention, there is provided the chip thermistor according to the first, second or third aspect, wherein the external extraction electrode is made of palladium or a palladium alloy. Could be solved. The invention of claim 5 is based on claim 1,
5. The chip thermistor according to 2, 3, or 4, wherein the end electrode is in contact with the external extraction electrode and extends on the protective film, and the external extraction electrode is protected. As a result, the above problem was solved.

According to a sixth aspect of the present invention, after forming a plurality of thin film thermistors on an insulating substrate, a slit-like hole is formed between the thin film thermistors by a sandblast method.
On the side surface of the slit-shaped hole, a chromium, copper or nickel, nickel electroplating layer, an end electrode composed of four metal thin-film layers of tin-lead alloy is formed in a substantially U-shape, and then the thin-film thermistor is formed. A method for manufacturing a chip thermistor characterized by cutting and separating parts into individual chip thermistors, which is an easy-to-handle manufacturing method for manufacturing a chip thermistor, after forming a thin film thermistor on an insulating substrate. Since the end electrodes are formed by forming slit-shaped holes, the accuracy of the photolithography process when forming the thin-film thermistor can be improved, and the resistance value of the heat-sensitive film can be made with high accuracy. We were able to. According to a seventh aspect of the present invention, in the method for manufacturing a chip thermistor according to the sixth aspect, the insulating substrate has a trapezoidal shape by the sandblasting method. The above problem was able to be solved.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a chip thermistor according to the present invention and a method for manufacturing the same will be described below with reference to the drawings. FIG. 1 shows a chip thermistor. When a thin-film thermistor is formed on one surface of a substantially trapezoidal insulating substrate 1, electrode pads 4 composed of a metal base layer 2 and a metal thin-film layer 3 are formed to face each other. . An insulating film 5a is formed between these electrode pads 4, and furthermore, lead-out electrodes 6a and 6b which are in contact with the electrode pad 4 and extend on the electrode pad 4 in contact with the insulating film 5a are formed facing each other. Have been. A heat-sensitive film 7a is formed in contact with the extraction electrodes 6a and 6b. The heat-sensitive film 7a may be a single layer if the electrical characteristics are satisfied, but may have a two-layer structure to adjust the electrical characteristics. The heat-sensitive film 7a is covered with a glass protective film 9a. At the end surfaces of the extraction electrodes 6a and 6b, the first side lower metal thin film layer 15 which surrounds the side surface of the substrate in a U-shape and contacts the extraction electrodes 6a and 6b and is in contact with the side surface of the insulating substrate; 15 and intermediate metal thin film layers 16 and 17
And the surface electrode layer 18. Further, a pair of end electrodes of the chip thermistor on the side to be bonded to the printed board is formed on the long side of the bottom of the trapezoidal insulating substrate 1,
Since the interval between the end electrodes is sufficiently provided, it is suitable for mounting the chip thermistor on a printed circuit board.

Next, a method of manufacturing the chip thermistor of the above embodiment will be described with reference to FIGS. First, the insulating substrate 1 is a ceramic substrate such as alumina, quartz, mullite, steatite or the like having a thickness of about 100 to 300 [mu] m, and the surface of which is polished to a smoothness of 0.05 [mu] m or less is used. On the polished surface of the insulating substrate 1, a metal base layer 2 and a metal thin film layer 3 are deposited by a method such as sputtering or vapor deposition (FIG. 2A).
The metal underlayer 2 is made of titanium (Ti), chromium (Cr), nickel (Ni), molybdenum (Mo), tungsten (W), a Ni—Cr alloy, or the like, which is adhered to the insulating substrate 1. Platinum (Pt) and palladium (P
d) or a metal thin film layer 3 of a palladium alloy, gold (Au), or the like. Further, since the metal base layer 2 and the metal thin film layer 3 are formed continuously in a vacuum chamber, a peeling layer such as an oxide film is not formed at the boundary between the metal base layer 2 and the metal thin film layer 3. Has been done like that. The metal base layer 2 is formed to improve the adhesion to the insulating substrate 1, and the total thickness of the metal base layer 2 and the metal thin film layer 3 is about 100 to 500 nm.

Subsequently, unnecessary portions of the metal base layer 2 and the metal thin film layer 3 are removed by a photoetching method, and an electrode pad 4 is formed by the metal base layer 2 and the metal thin film layer 3 (FIG. 2B). )). Then, sputtering method, plasma CV
An insulating film 5 having a thickness of 100 to 500 nm, such as silicon dioxide (SiO ₂ ) or silicon nitride (Si ₃ N ₄ ), is formed by a method D or the like, and is patterned by photoetching to insulate between the electrode pads 4. The film 5a is formed (FIG. 2C). The insulating film 5a has an effect of preventing a heat-sensitive film, which will be described later, and an insulating substrate from reacting during heat treatment to prevent the characteristics from becoming unstable.

Next, the process proceeds to a step of forming an external extraction electrode. First, a metal thin film layer 6 of platinum (P), palladium (Pd) or a palladium alloy, gold (Au) or the like is formed by sputtering, ion plating, vapor deposition or the like (FIG. 2D). Then, the metal thin film layer 6 is patterned by a photo-etching method to form the electrode pads 4.
And the external extraction electrodes 6a and 6b in contact with the insulating layer 5a are formed so as to face each other (FIG. 2E).

Subsequently, 100 to 500 nm is formed by sputtering or the like so as to cover the external extraction electrodes 6a and 6b.
The heat-sensitive film 7 is formed to a thickness of (FIG. 3A).
Is patterned to form a heat-sensitive film 7a between the external extraction electrodes 6a and 6b (FIG. 3B). Then, the heat-sensitive film 7
a is heat-treated at a temperature of 500 to 1000 ° C. for 1 to 5 hours. The heat-sensitive film 7a targets a sintered body of a composite oxide made of manganese (Mn), nickel (Ni), gobalt (Co), iron (Fe), etc., has a sputtering pressure of 0.2 to 0.7 Pa, and has insulation. The temperature of the substrate 1 is 200 to 50
It is formed by performing sputtering at 0 ° C.
When forming the insulating film 5a and the heat-sensitive film 7a, the insulating substrate 1
Is preferably heated to a temperature of 200 to 500 ° C.

When it is necessary to finely adjust the electric characteristics of the heat-sensitive film 7a, the heat-sensitive film is formed by forming a second heat-sensitive film 7 'on the heat-sensitive film 7a to adjust the electric characteristics (FIG. 3).
(C)). Further, the second heat-sensitive film 7 'is patterned to form a second heat-sensitive film 7'a (FIG. 3D).
In this case, the second heat-sensitive film 7'a is preferably formed to be larger than the heat-sensitive film 7a, and it is preferable to improve the coverage of the film steps when forming the insulating film thereafter. Second heat-sensitive film 7'a
Is not necessarily required as long as the electrical characteristics can be satisfied by the first heat-sensitive film 7a.

Further, in order to protect the heat-sensitive films 7a and 7'a, silicon dioxide (SiO ₂ ) of 0.5 to 2.0 μm,
An insulating protective film 8 made of silicon nitride (Si ₃ N ₄ ) or the like is formed (FIG. 4A), and a glass paste is screen-printed on the insulating protective film 8 as needed for the purpose of further improving moisture resistance. It is applied by a method or the like, and is heat-treated at 400 to 800 ° C. to form a glass protective film 9 (FIG. 4B). In addition to the screen printing method, the glass protective film 9 is formed by forming a glass film on the entire surface of the substrate, and then, as shown in FIG.
a and the glass protective film 9a may be formed.

By manufacturing as described above, a thermistor aggregate substrate 11 in which a number of the thin film thermistors 10 having the above-described structure are arranged on the insulating substrate 1 is formed (FIG. 5).

Subsequently, a photosensitive film is adhered on the thermistor collective substrate 11 and patterned by the photolithography technique, so that the thin film thermistor 10 is covered with the film 14 and the adjacent film 14 is formed on the collective substrate 11. A slit-shaped opening 12 is formed between the thin film thermistors 10 covered by the above (FIG. 6).

Then, using the film 14 in which the opening 12 is formed as a mask, a slit-like hole 13 is formed in the collective substrate 11 by sandblasting (FIG. 7). FIG.
FIG. 1 shows a cross-sectional view of a part of an insulating substrate on which a large number of thin film thermistors 10 of an aggregate substrate 11 are formed. In this manufacturing process, a trapezoidal insulating substrate 1 is formed, and the abrasive blasts in the sandblasting process. With the slit-shaped hole 13
Of the back side 13 'is shaved to form a curved surface. After forming the slit holes 13, the film 14 for protecting the thin film thermistor 10 is removed (FIG. 8A). In FIG. 8, the illustration of the insulating protective film 8a is omitted.

Subsequently, the process proceeds to a process of manufacturing an end electrode of the thin film thermistor 10. First, as shown in FIGS. 8 (b) and 8 (c), by using a thin film technique such as sputtering or vapor deposition, an end portion which surrounds the side surface of the slit-shaped hole 13 in a U-shape and extends to a part of the back surface. An electrode is formed. The end electrodes are four metal thin film layers. First, metal masks 19, 19 'are fixed on both surfaces of the collective substrate 11, and the external extraction electrodes 6a, 6b and the insulating substrate 1 which are in contact with the heat-sensitive film 7a by sputtering or the like.
Tungsten (W) and chromium (C)
r), a lower metal thin film layer 15 of chromium alloy, titanium (Ti) or the like is formed to a thickness of 0.05 to 0.5 μm. An intermediate metal thin film layer 16 made of nickel (Ni) and copper (Cu) is formed thereon with a thickness of 0.1 to 1 μm. The lower metal thin-film layer 15 and the middle metal thin-film layer 16 are continuously formed in the chamber in order to enhance the adhesion for the same reason as described above.

Further, on the middle metal thin film layer 16,
A metal thin film layer 17 having a thickness of μm is formed. The metal thin film layer 17 is formed by electroplating at a high deposition rate.
The metal thin film layer 17 is electrically connected to the external extraction electrodes 6a and 6b, and not only functions as a barrier layer for preventing the lower metal thin film layer 15 from eroding the solder, but also functions as a barrier layer.
External extraction electrode 6 at the boundary between glass protective film 9a and 6b
It has a function as a barrier layer for preventing deterioration of characteristics due to solder erosion of the exposed portions a and 6b. Further, the metal thin film layer 1
7, tin (S) having good solder wettability of 3 to 10 μm
n), a surface metal thin film layer 18 made of a tin-lead alloy (Sn-Pb) is formed by electroplating (FIG. 8C).

Subsequently, the thin-film thermistor assembly substrate 11 having the U-shaped end electrodes formed thereon is affixed to a base substrate for cutting and separating into individual chip thermistors, and the thermistor assembly substrate 11 is separated by a dicing saw or the like. Is cut and separated into individual thermistor chips. Thus, a thermistor chip is formed.

[0026]

As described above, according to the present invention, a large number of thin-film thermistors are formed on a single insulating substrate by thin-film technology, and slit-shaped holes are formed in the thermistor assembly substrate in a substantially trapezoidal insulating manner by sandblasting. Since the U-shaped end electrode made of a metal thin film layer is formed on the side surface of the slit-shaped hole as a substrate, the following effects can be obtained.

(1) A substantially U-shaped end electrode is formed on an insulating substrate having a trapezoidal chip thermistor, and a large gap is formed between the end electrodes on the side mounted on the printed circuit board. The chip-like component on which the thermistor is formed is suitable for mounting on a printed board, and the trapezoidal insulating substrate has a chamfered bottom side surface, which has the effect of reducing disconnection of the end electrode.

(2) After forming a large number of thin-film thermistors on an insulating substrate, slit-shaped holes are formed in the insulating substrate to form end electrodes, and a conventional chip using an insulating substrate in which slit-shaped holes are formed in advance. Various problems observed in the manufacturing method of parts, particularly, the problem of accuracy in a photolithography process are solved, and a fine thin-film thermistor and its electrodes are easily patterned. Contributes to the improvement of the degree of integration, and has an extremely excellent effect on productivity.

(3) It is extremely effective when manufacturing a large number of thin film thermistors having a multilayer structure, and it is not necessary to use a perforated insulating substrate. There is an advantage that the product yield is improved.
Furthermore, since a thin film thermistor having a multilayer structure can be formed with high accuracy, it is easy to adjust electrical characteristics such as the resistance value of the thin film thermistor, and it is easy to form a protective layer.
It is also effective in increasing the moisture resistance of the thin film thermistor.

(4) The end electrode has a lower metal thin film layer of W, Cr, Cr alloy, Ti, etc., which has good adhesion between the extraction electrode of the heat-sensitive film and the insulating substrate, and has a property for resistance to solder erosion. Medium metal thin film layer of good Ni, Cu etc. and S with good solder wettability
By adopting a three-layer structure of a surface metal thin film layer of n, Sn-Pb or the like, there is an advantage that a chip thermistor having a highly reliable end electrode having high peel strength of the end electrode and excellent solder resistance can be provided. is there.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a chip thermistor of the present invention.

FIG. 2 is a sectional view showing one embodiment of a manufacturing process of the chip thermistor of the present invention.

FIG. 3 is a cross-sectional view showing a manufacturing step following FIG. 2;

FIG. 4 is a sectional view showing a manufacturing step following FIG. 3;

FIG. 5 is a plan view showing the manufacturing process of FIG. 4 (c).

FIG. 6 is a partial cross-sectional view for explaining a main part of FIG. 5;

FIG. 7 is a plan view showing a manufacturing step following FIG. 4;

8A is a cross-sectional view of a main part of FIG. 7, and FIGS. 8B and 8C are cross-sectional views showing a subsequent manufacturing process.

FIG. 9 is a view showing a conventional chip component manufacturing process.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating substrate 2 Metal underlayer 3 Metal thin film layer 4 Electrode pad 5a Insulating layer 6a, 6b External lead electrode layer 7a Heat sensitive film 8a Insulating protective film 9a Glass protective film 10 Thin film thermistor 11 Thin film thermistor integrated substrate 12 Opening 13 Slit hole 14 Film 15 Lower metal thin film layer 16 Middle metal thin film layer 17 Metal thin film layer 18 Surface metal thin film layer

Claims (7)

[Claims] An insulating substrate, a pair of electrode pads formed on the insulating substrate, an insulating film formed on the insulating substrate surface between the electrode pads, and an insulating film on the electrode pad in contact with the insulating film. A thin-film thermistor including a pair of extending external extraction electrodes, a heat-sensitive film formed between the external extraction electrodes with the insulating film as a base, a protective film covering the heat-sensitive film, and formed on a side surface of the insulating substrate. And an end electrode electrically connected to the external extraction electrode, wherein the end electrode is formed of four metal thin film layers, and has a substantially U-shape covering a side surface of the insulating substrate. Characterized chip thermistor. 2. The chip thermistor according to claim 1, wherein said pair of electrode pads are made of one of titanium, chromium, nickel, molybdenum, tungsten and a Ni—Cr alloy, and platinum, palladium, a palladium alloy and gold. A chip thermistor, characterized in that any one of them is a metal thin film layer sequentially formed on the surface of the insulating substrate, and the external extraction electrode is made of at least one metal of platinum, palladium, and a palladium alloy. 3. The chip thermistor according to claim 1, wherein the end electrodes are formed of a lower metal thin film layer of chromium, a middle metal thin film layer of copper or nickel, and an electroplating layer made of nickel sequentially from an insulating substrate surface. A chip thermistor comprising four thin film layers and a thin metal film layer of tin or a tin-lead alloy. 4. The chip thermistor according to claim 1, wherein said insulating substrate has a trapezoidal shape. 5. The chip thermistor according to claim 1, wherein said end electrode is in contact with said external lead-out electrode and extends on said protective film. . 6. After forming a plurality of thin-film thermistors on an insulating substrate, slit-like holes are formed between the thin-film thermistors by a sandblast method, and chromium, copper, nickel, or nickel electroplating is formed on side surfaces of the slit-like holes. An end electrode composed of four metal thin-film layers of tin-lead alloy is formed in a substantially U-shape, and then the thin-film thermistor is cut and separated into individual chip thermistors. Manufacturing method of chip thermistor. 7. The method for manufacturing a chip thermistor according to claim 6, wherein said insulating substrate is trapezoidal by said sandblasting method.