JPH08330102A - Ship resistor - Google Patents

Abstract

PURPOSE: To provide a chip resistor which can cope with a bulk cassette, prevents a change in a resistance value, and has terminal electrodes with increased strength by making the thickness of the terminal electrode sections on a substrate the same as that of a resistor film section on the substrate. CONSTITUTION: Terminal electrodes 2, 3 are formed on front faces, end faces, and rear faces of a pair of facing edges of a nearly square-shaped ceramic substrate. Then, a resistor film 4 is formed so as to be connected to a pair of the terminal electrodes 2, 3. On the resistor film 4, protective glass films 5, 6 are formed. Thus, a chip resistor is manufactured. In this chip resistor, surface electrodes 2a, 3a have such sections 21a, 31a as to have a difference in level in the thickness direction of inner sides of the surface electrodes which are connected to the resistor film 4. The thickness of the surface electrodes 21, 31 is substantially the same as that of a resistor film section (the resistor film 4 and the protective glass films 5, 6).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chip resistor such as a chip fixed resistor and a chip multiple resistor.

[0002]

2. Description of the Related Art Conventionally, a typical structure of a chip-shaped electronic component, for example, a chip-shaped fixed resistor, is shown in a sectional view of FIG. The terminal electrodes 12 and 13 are formed over the three surfaces of the front surface, the end surface, and the back surface of the part, and the resistor film 14 is formed so as to be connected to the pair of terminal electrodes 12 and 13. Further, a primary overglass film 15 and a secondary overglass film 16, which are protective glass films, are adhered and formed on the resistor film 14 (JP-A-60-2710).
No. 4, No. 63-182501.

Here, the primary overglass film 15 is burned and removed by irradiating the primary overglass film 15 and the resistor film 14 with a laser when adjusting the resistor film 14 to have a predetermined resistance characteristic. However, at this time, the secondary overglass film 16 is provided in order to reduce the impact on the resistor film 14 due to the laser irradiation, and the secondary overglass film 16 covers the removal traces due to the laser irradiation and the terminal electrodes 12, 1
It is provided for protection when the surface of 3 is plated, and for moisture resistance when it is mounted on a printed wiring board.

Any of the primary and secondary overglass films 1
Nos. 5 and 16 are formed by screen-printing a low-melting-point glass paste containing silica or the like into a predetermined shape, followed by drying and baking.

In the terminal electrodes 12 and 13, the portions exposed from the secondary overglass film 16 are provided with Ni plating or solder plating layers 12a and 13a in order to ensure solder joint to the printed wiring board. It had been.

This type of chip-shaped resistor is housed in a taping member or a bulk cassette having a storage recess formed therein, and at a predetermined position of the printed wiring board, the chip-shaped resistor is separated from the taping member or the bulk cassette. The resistor is extracted and placed / mounted on a predetermined printed wiring board.

In particular, when the chip-shaped resistor is extracted from the taping member in which the storage recess is formed, since the front surface side of the chip-shaped resistor is usually located on the opening side of the storage recess, mounting is performed. It was not necessary to distinguish between the front and back.

However, when stored in a bulk cassette,
Since the chip resistors are randomly stored in the cassette, it is necessary to determine the front and back of the chip resistor with respect to the printed wiring board in order to perform stable mounting.

If the front surface and the back surface are not discriminated, if the surface of the chip-shaped resistor contacting the mounting surface of the printed wiring board is the back surface side, it can be mounted without trouble, but if the surface is the front surface side. , Stable implementation is not done.

This is because in the structure of the substrate surface of the chip resistor, the thickness of the terminal electrodes 12 and 13 and the resistor film 14 are different, so the surface side of the chip resistor contacts the printed wiring board. When implemented as
The terminal electrodes 12 and 13 will not come into stable contact with the mounting surface of the printed wiring board.

For example, the terminal electrode 12 of the chip resistor,
About 13 μm from the surface of the substrate 11 in the 13th part
Base conductor film to be the terminal electrodes 12 and 13, plating layers 12a and 13a of about 10 μm (Ni plating layer of about 5 μm, about 5
There is a solder plating layer) having a thickness of about 20 μm. On the other hand, the resistance film 14 has a thickness of about 10 μm.
The resistor film 14, the primary overglass film 15 of about 10 μm, and the secondary overglass film 16 of about 30 μm are present and have a thickness of about 50 μm.

In order to reduce the difference in thickness between the terminal electrodes 12 and 13 in order to reduce the difference in thickness between the resistor film 14 portion, Japanese Unexamined Patent Application Publication No. Hei.
No. 102302 discloses forming an auxiliary terminal electrode on the surface portion of the terminal electrode.

[0013]

However, in the above chip-shaped resistor, the auxiliary terminal electrode is formed of the terminal electrode, the resistor film, the primary overglass film, and the resistance value of the resistor film. It was formed after the adjustment and the formation of the secondary overglass film. That is, after the resistance value is adjusted, the resistor film is subjected to baking of the secondary overglass film, baking of the terminal electrode portion of the substrate end face portion, and further baking processing for forming the auxiliary terminal electrode. And a total of 3 heat treatments are applied. As described above, due to the large number of baking treatments, the resistance film having the adjusted resistance value has a characteristic variation.

Further, after forming the primary overglass film 15 and the secondary overglass 16, the auxiliary terminal electrodes are formed. In particular, the secondary overglass 16
Since it is used as the entire protective film, its thickness becomes particularly thick, about 30 μm. Therefore, when the glass paste that should form the secondary overglass 16 is printed, the glass paste is widely attached to the already formed front surface side terminal electrode due to the sagging of the paste or the like. As described above, when the auxiliary terminal electrode is formed on the glass film, the dissimilar materials are bonded and the bonding strength is lowered, and the bonding reliability between the surface side terminal electrode and the auxiliary terminal electrode is reduced. It will decrease.

The present invention has been devised in view of the above-mentioned problems, and an object thereof is to make the thickness of the terminal electrode portion and the thickness of the resistor film portion equal to each other and to cope with the bulk cassette. Moreover, it is an object of the present invention to provide a chip resistor in which fluctuations in resistance value are suppressed and terminal electrode strength is improved.

[0016]

SUMMARY OF THE INVENTION According to the present invention, a pair of terminal electrodes are attached to the surfaces, end surfaces and back surfaces of opposing ends of a substantially rectangular ceramic substrate, and the pair of terminals are provided on the surface of the ceramic substrate. A resistor film connected to the electrode,
In a chip resistor formed by sequentially depositing a protective glass film that protects the resistor film, the thickness of the region of the pair of terminal electrodes that is adhered to the surface of the ceramic substrate is the protective glass from the substrate surface. A chip resistor having substantially the same thickness as the surface of the film and having a step in the thickness direction on the inner side of the region to which the resistor film is connected.

[0017]

According to the present invention, the thickness of the region of the pair of terminal electrodes that is adhered to the surface of the ceramic substrate, that is, the surface electrode portion, is determined by the resistor film portion (resistor film, protective glass) on the substrate surface. The total thickness of the film) is substantially the same, and a step is formed on the inner side of the surface electrode portion connected to the resistor film. The surface electrode part having such a structure is
It can be easily formed by multiple times of overprinting.

As a result, it becomes possible to substantially eliminate the displacement of the thickness of the terminal electrode portion and the resistor portion on the insulating substrate, and the printed wiring board can be mounted without discriminating between the front and back sides of the printed wiring board. It can be stably arranged on the wiring board. This improves the adaptability for bulk cassettes.

Further, since the superposed connection between the surface electrode portion and the resistor film can be performed at the step portion having a small thickness, disconnection due to the superposed connection of the resistor film can be suppressed, and stable resistance characteristics can be derived. can do.

Further, the formation of the surface electrode portion can be achieved by one-time firing like a typical chip resistor, and the number of heat treatments to the resistance film whose resistance value is adjusted becomes the minimum number. Therefore, it is possible to effectively suppress the characteristic variation of the resistor film whose resistance value is adjusted.

Further, when printing the primary overglass film or the secondary overglass film, the terminal electrode of this multi-layer structure acts as a barrier for preventing sagging of the glass paste, so that the surface of the surface electrode portion is provided with a conductive member. Since it is possible to expose a wide area, the plating coating area is increased, and the solder bonding on the printed wiring board becomes more stable.

Further, while the surface electrode portion is formed in one step, in the conventional chip-shaped resistor, the auxiliary electrode is formed on the surface electrode portion in another step. Therefore, the process does not become complicated, and since a glass film is not interposed between the surface electrode portion and the auxiliary electrode as in the conventional case, a strong terminal electrode can be formed.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A chip resistor according to the present invention will be described below with reference to the drawings.

FIG. 1 is a plan view of the chip resistor of the present invention in a partially broken state, and FIG. 2 is a structural view taken along the line AA in FIG. In the figure, the chip resistor 10 having one resistor film on the ceramic substrate will be described as an example.

The chip resistor 10 comprises a rectangular ceramic substrate 1, terminal electrodes 2, 3, a resistor film 4, a primary overglass film 5, and a secondary overglass film 6.

The ceramic substrate 1 is made of, for example, alumina ceramic and has a shape of, for example, 1.6 mm ×
It has a quadrangular shape such as 3.2 mm or 0.5 × 1.0 mm.

Terminal electrodes 2 and 3 are formed at one end of the pair of ceramic substrates 1 facing each other, for example, at both ends in the longitudinal direction of the ceramic substrate 1.

The terminal electrodes 2 and 3 are composed of conductor films on the three surfaces of the ceramic substrate 1, that is, the end surface, the end surface, and the back surface. For example, the underlying conductor films 2x and 3 formed by printing and baking a conductor paste containing Ag as a main component.
x and N in the portion exposed from the secondary overglass film 6
Plated layers 2y, 3 that have been plated with i-plating or solder
Steps 21a and 31a are formed in the thickness direction on the side having y and connecting to the resistor film 4. here,
In particular, the conductor film portions formed on the end surface of the terminal electrodes 2 and 3 are referred to as surface electrode portions 2a and 3a.

The base conductor film 2x of the surface electrode portions 2a, 3a,
3x has a multi-layer structure, and is formed by printing the conductive paste a plurality of times so that the shape of the 3x gradually decreases from the insulating substrate 1 to the upper portion. As a result, near the center of the ceramic substrate 1 of the surface electrode portions 2a, 3a, that is,
The step portions 21a, 3 are provided on the side of the resistor film 4 on the side connected to the end portion.
1a is formed. The number of times the conductive paste is printed to form the base conductor films 2x and 3x depends on the thickness of the resistor film portion (resistor film, protective glass film), plating layer 2y,
The number of times is set so that this value is obtained by dividing the thickness of 3y.

For example, the thickness of the resistor film portion is about 50 μm.
m (thickness of resistor film 4 is 10 μm, thickness of primary overglass film 5 is 10 μm, thickness of secondary overglass film 6 is 30 μm)
μm) and the thickness of the surface plating layer of the terminal electrodes 2 and 1 is 1
0 μm (eg Ni plating layer 5 μm, solder plating 5 μm
m), the difference is 40 μm. Also,
Since the thickness of about 10 μm can be obtained by printing the conductive paste once to form the base conductor films 2x and 3x of the terminal electrodes 2 and 3, as a result, about four times of printing is required. In the step portions 21a and 31a described above, the ridge line portion is rounded or a plurality of steps are connected due to the viscosity of the conductive paste or the like, and the underlying conductor films 2x and 3x are connected.
Although the end surface of the sloping surface may be inclined, this case is acceptable.

The resistor film 4 is formed so as to overlap the stepped portions 21a and 31a of the surface electrode portions 2a and 3a of the terminal electrodes 2 and 3 of the ceramic substrate 1.

The resistor film 4 is formed of a resistor material containing a metal oxide such as ruthenium oxide as a main component. The resistor film 4 is superposed and connected to the step portions 21a and 31a formed by the base conductor films 2x and 3x of the surface electrode portions 2a and 3a, for example, with a length of about 0.05 to 0.2 mm.

A primary overglass film 5 and a secondary overglass film 6 which are glass protective films are formed on the surface of the resistor film 4.

The primary overglass film 5 is made of a low-melting glass containing SiO ₂ and the like, and is provided to alleviate the impact of the laser irradiation on the resistor film 4 as described above, and its film thickness is about 10 μm. It is a degree.

The secondary overglass film 6 is made of a low-melting glass containing SiO ₂ or the like, and is configured to completely cover the resistor film 4, the primary overglass film 5, and the trimming groove 4a formed by laser irradiation in the overlapping connection portion. It is formed, and its film thickness is, for example, 30 to 60 μm.

Next, an outline of a method of manufacturing the above chip resistor will be described.

First, a large ceramic substrate from which a plurality of ceramic substrates 1 can be extracted is formed. In the large-sized ceramic substrate, dividing grooves are formed vertically and horizontally so that one chip resistor can be extracted. That is, one element region is divided by the dividing groove.

Next, a base conductor film for the back surface side electrode portions 2b, 3b of the terminal electrodes 2, 3 is formed on the back surface of each element region of the large-sized ceramic substrate. Specifically, a conductive paste containing Ag or the like as a main component is screen-printed in a predetermined shape, dried, and then baked at about 850 ° C.

Further, the base conductor films 2x, 3x of the surface electrode portions 2a, 3a of the terminal electrodes 2, 3 are formed on the surface of each element region of the large-sized ceramic substrate. Specifically, a plurality of, for example, four times, screen printing is performed in a predetermined shape using a conductive paste containing Ag as a main component, and after drying, about 850 ° C.
The baking process is performed. This state is shown in FIG.

Note that FIG. 3 shows only one element, and the surface electrode portions 2a and 3a of the terminal electrodes 2 and 3 have stepped portions 21a and 31a formed on the end faces near the center thereof. The print shape of the overprint can be easily formed by gradually reducing the print area for each overprint.

In the formation of the base conductor films 2x, 3x of the front surface electrode portions 2a, 3a and the back surface electrode portions 2b, 3b described above, printing and drying of the conductive paste are separately performed, and the firing process is performed. You may make it common.

Next, on the surface of each element region of the large-sized ceramic substrate, the surface electrode portions 2a, 3a of the terminal electrodes 2, 3 are formed.
The resistor film 4 is formed so as to partially overlap the stepped portions 21a and 31a. Specifically, for example, a resistor paste containing ruthenium oxide as a main component is screen-printed in a predetermined shape, dried, and then baked at about 850 ° C. This state is shown in FIG.

Next, the primary overglass film 5 is formed on at least the resistor film 4 on the surface of each element region of the large-sized ceramic substrate. Specifically, for example, a low melting point glass paste containing SiO ₂ or the like is used for screen printing in a predetermined shape, followed by drying and baking at about 600 ° C. This state is shown in FIG.

Next, the surface electrode portions 2a of the terminal electrodes 2 and 3,
While connecting the terminals (probes) of the resistance value measuring device to the underlying conductor films 2x and 3x of 3a, and measuring the resistance value of the resistance film 4, the resistance film 4 is connected to the resistance film 4 through the primary overglass film 5. Laser irradiation is performed to form a trimming groove 4a in a part of the resistor film 4. A part of the primary overglass film 5 and the resistor film 4 irradiated with this laser beam is burned off and removed to form the trimming groove 4a. Due to the length of the trimming groove 4a, the substantial electrical width of the resistor film 4 is reduced, and the resistance value can be set to a predetermined value. Since the resistor film 4 is irradiated with the laser through the primary overglass film 5, the impact due to the irradiation is mitigated, and unnecessary cracks and the like are not generated in the resistor film 4. It is possible to derive stable characteristics even afterward.

Next, the secondary overglass film 6 is formed on the surface of each element region of the large-sized ceramic substrate. Specifically, for example, a low melting point glass paste containing SiO ₂ or the like is used for screen printing in a predetermined shape, followed by drying and baking at about 600 ° C. This state is shown in Figure 6.
Shown in Particularly, since the thickness of the secondary overglass film 6 is much thicker than that of the primary overglass film 5,
When a glass paste is printed to form the next overglass film 6, it is feared that the glass paste may cause excessive adhesion to the surfaces of the terminal electrodes 2 and 3. However, in this step,
The underlying conductor films 2x and 3x of the surface electrode portions 2a and 3a are
Since it acts as a barrier for preventing this sagging, it is possible to effectively prevent the excess glass paste from adhering to the surfaces of the underlying conductor films 2x and 3x.

Next, a dividing process is performed along the dividing grooves in one direction, which are divided into each element region of the large-sized ceramic substrate, to obtain a strip substrate. Here, the dividing groove in one direction is a dividing groove on the side where the surfaces to be the terminal electrodes 2 and 3 are exposed at the divided end surfaces.

Next, the divided end faces of the strip-shaped substrate are aligned, and end face electrode portions to be the terminal electrodes 2 and 3 are formed on the divided end faces of each element region. Specifically, a conductive paste containing Ag as a main component is screen-printed in a predetermined shape, dried, and then baked at about 600 ° C.

Next, a dividing process is performed along the dividing grooves in the other direction, which are divided into the respective element regions of the large-sized ceramic substrate, to obtain individual elements.

After that, the front surface electrode portions 2a, 3a where the terminal electrodes 2, 3 are exposed, the end surface electrode portion, the back surface electrode portion 2b, 3
On the surface of b, plated layers 2y, 3y of Ni, solder, etc. are deposited.

In the chip resistor 10 described above, the terminal electrodes 2 and 3 located at the end portion on the front surface side of the ceramic substrate 1.
The surface electrode portions 2a and 3a are formed with step portions 21a and 31a in the thickness direction on the inner side thereof, and the thickness of the surface electrode portions 2a and 3a is set in consideration of the thickness of the resistor portion.
As a result, the terminal electrode portion and the resistor film portion on the ceramic substrate 1 are formed to have substantially the same thickness, and preferably the terminal electrode portion is slightly thicker.

Therefore, as shown in FIG. 7, even if the surface of the chip resistor 10 is arranged on the predetermined wiring conductors 71 and 72 of the printed wiring board 70 so as to face the printed wiring board 70 side, Over-glass film 5, 6 of body part
Since it can be suppressed that it projects more than the surface electrode portions 2a, 3a, it can be stably mounted on the printed wiring board.

Therefore, since it is not necessary to distinguish between the front and back of the chip resistor 10, the bulk cassette in which the chip resistors are randomly stored in the cassette is used to efficiently carry and mount the chip resistor on the printed circuit board. be able to.

Further, the surface electrode portions 2a, 3a and the resistor film 4
Since the overlapping connection with and is performed at the step portions 21a and 31a that are sufficiently smaller than the actual thickness, there is no step breakage due to the thickness, and stable resistance characteristics can be derived.

Further, since the number of times of heat treatment of the resistance film whose resistance value is adjusted is not different from that of a typical chip resistor, the characteristics of the resistance film whose resistance value is adjusted can be stably maintained.

Further, since the primary overglass film 5 and the secondary overglass film 6 are formed by printing so as to be filled between the surface electrode portions 2a, 3a of the pair of terminal electrodes 2, 3, the glass paste of The sagging can be effectively prevented, and the coating area of the surface electrode portions 2a, 3a on which the plated layers 2y, 3y are formed can be increased. As a result, the printed wiring board 70
The upper solder joint will be more stable.

Furthermore, a pair of terminal electrodes 2, 3 having a multilayer structure
Since the front surface electrode portions 2a, 3a can be formed by a series of steps, the steps are not complicated as compared with the conventional chip-shaped resistor, and the glass components are not formed on the terminal electrodes 2, 3 as in the conventional case. Since foreign matter such as
Strong terminal electrodes 2 and 3 can be formed.

In particular, in the chip resistor, the shape of the ceramic substrate 1 has become extremely small in recent years, and in such a miniaturized chip resistor, the above-mentioned action becomes more remarkable.

In the above embodiments, the chip-shaped resistor having a single resistor film formed thereon has been described as an example, but a plurality of resistor films are formed and a plurality of pairs of terminal electrodes are provided. It can also be applied to multiple resistors.

[0059]

As described above, according to the present invention, in the surface electrode portion, a step is formed in the thickness direction on the inner side connected to the resistor film, and the thickness is equal to that of the resistor film portion. It is substantially the same as the thickness. Therefore, on the surface of the chip resistor, the thicknesses of the terminal electrode portion and the resistor film portion are substantially the same.Therefore, when taking out from the bulk cassette and mounting it on the printed wiring board, the front and back discrimination work It is not necessary and can be implemented efficiently. Moreover, it is possible to prevent step breakage between the resistor film and the terminal electrode and suppress variations in the resistance value, so that it is possible to stably derive the predetermined resistance value characteristic. In addition, the strength of bonding to the printed wiring board and the strength of the terminal electrode itself can be improved.

[Brief description of drawings]

FIG. 1 is a plan view of a chip resistor, which is an example of the chip resistor of the present invention, with a part thereof broken away.

FIG. 2 is a structural diagram of a cross section taken along the line AA in FIG.

FIG. 3 is a partial cross-sectional view in a main process of the chip resistor according to the present invention.

FIG. 4 is a partial cross-sectional view in the main process of the chip resistor according to the present invention.

FIG. 5 is a partial cross-sectional view in the main process of the chip resistor according to the present invention.

FIG. 6 is a partial cross-sectional view in the main process of the chip resistor according to the present invention.

FIG. 7 is a schematic view showing a state where the chip resistor according to the present invention is mounted on a printed wiring board.

FIG. 8 is a structural diagram of a typical chip resistor.

[Explanation of Codes] 10-chip resistor 1-ceramic substrate 2, 3 --- terminal electrode 2x, 3x --- underlying conductor film 2y, 3y --- plating layer 2a, 3a ... Surface electrode portion 21a, 31a ... Step portion 4 ... Resistor film 5 ... Primary overglass film 6 ... Secondary overglass film

Claims (1)

[Claims] 1. A resistor film for depositing a pair of terminal electrodes on the surfaces, end surfaces and back surfaces of opposing ends of a substantially rectangular ceramic substrate, and for connecting the pair of terminal electrodes to the ceramic substrate surface. A chip resistor formed by sequentially depositing a protective glass film for protecting the resistor film, wherein a thickness of a region of the pair of terminal electrodes attached to the ceramic substrate surface is protected from the ceramic substrate surface. A chip resistor having substantially the same thickness as the surface of the glass film and having a step in the thickness direction on the inner side of the region to which the resistor film is connected.