JPH0878217A - Manufacture of rectangular-shaped thin film chip resistor - Google Patents

Abstract

PURPOSE: To prevent both the generation of deterioration in linearity and the generation of disconnection failure by a method wherein a resistance pattern is formed by conducting two or more exposing operations in a photolithography process without increasing number of man-hours. CONSTITUTION: Dividing grooves 2, in vertical and horizontal directions opposing with each other, are formed on the front and back sides of an alumina substrate 1. These dividing grooves 2 are formed in such a manner that the groove on the front side is deeper than the grooves on the back side. Then, after a thin film front side electrode layer 3 and a thin film back side electrode layer have been formed, a thin resistance film 5 is formed on the whole back side of the substrate 1, and a photolithography process is conducted for formation of the thin resistance film 5 on the prescribed resistance pattern 6. First, positive type resist is uniformly coated on the thin resistance film 5, and after the resist has been dried up, an exposing operation is conducted. The exposing operation is conducted twice using different photomasks of different pattern. A photomask, which is designed to expose the dividing grooves 2 only, is used in the exposing operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to a method of manufacturing a rectangular thin film chip resistor used in electronic circuits.

[0002]

2. Description of the Related Art In recent years, with the downsizing of electronic equipment, there is an increasing demand for miniaturization of electronic components to be mounted in order to increase the packaging density of the circuit board. Along with the miniaturization of the rectangular chip resistors, there is an increasing demand for rectangular thin film chip resistors with high accuracy (resistance tolerance, resistance temperature characteristics) and excellent current noise characteristics.

An example of a conventional method for manufacturing a rectangular thin film chip resistor is shown in FIG. First, the insulating substrate 21 made of 96% alumina having a plurality of vertical and horizontal dividing grooves 22 provided so as to face each other on the front and back surfaces is received.
This insulating substrate 21 is also used as a rectangular thick film chip resistor in order to reduce the material cost.
Therefore, the dividing groove 22 provided on the insulating substrate 21 is
In order to improve the individual divided shape in the subsequent dividing step, when the surface on which the thick film resistor is formed is the front surface, the front surface is generally formed deeper than the back surface.

Next, an electrode paste made of a metal organic material containing Au as a main component is screen-printed and dried on the front and back surfaces of the 96% alumina substrate 21. Thereafter, in order to remove only the organic component of the electrode paste and burn only the metal component onto the alumina substrate 21, a belt type continuous firing furnace was used at a temperature of 850 ° C. for a peak time of 6 minutes, IN-OU.
A step of forming the thin film upper surface electrode layer 23 and the thin film back surface electrode layer is performed by firing according to a profile of T time 45 minutes.

Next, a sputtering step of forming a thin film resistance film 24 of Ni-Cr or the like on the entire surface of the insulating substrate 21 (the surface where the dividing groove is deep), and the thin film resistance film 24 is formed into a predetermined resistance pattern 25. Photolithography process steps (resist coating / drying, exposure, development, etching, resist stripping)
Then, in order to make the resistance pattern 25 a stable film, a heat treatment process at 350 to 400 ° C. is performed in nitrogen or the like. After that, the thin film resistance film 2 remaining in the dividing grooves 22 of the insulating substrate 21
In order to remove No. 4, a resistance film removing process is performed by a laser, and in order to correct the resistance value of the resistance pattern 25 to a predetermined value, a resistance value correcting process is performed by laser trimming. Then, the resistance pattern 2 whose resistance value has been corrected
In order to protect No. 5, a step of forming the protective coat 26 made of a thermosetting resin is performed. Further, a primary substrate dividing step of dividing the insulating substrate 21 into strip substrates 21a is performed, and an end face electrode forming step of forming the thin film end face electrode layer 27 is performed by using sputtering on the end faces of the strip substrate 21a. Finally, a secondary substrate dividing step of dividing the strip substrate 21a into individual substrates 21b is performed, and finally an electrode plating step of forming an electrode plating layer 28 for ensuring reliability at the time of soldering is performed. Formed a thin film chip resistor.

[0006]

However, the conventional method of manufacturing a thin film chip resistor has the following problems.

(1) When the thin film resistance film 24 is formed on the surface of the insulating substrate 21 having the dividing grooves 22, the thin film resistance film 24 formed in the dividing grooves 22 cannot be completely removed by the photolithography process step. This is because when a resist is applied to the entire surface of the insulating substrate 21 for pattern formation, it flows into the dividing grooves 22 and the resist pattern 2
This is because the film thickness of the resist becomes thicker than the part where 5 is formed, and the resist remains in the dividing groove 22 part after exposure and development. That is, when the exposure condition is set to the resist film thickness of the portion where the resistance pattern 25 is formed, the resist remains in the dividing groove 22 and the thin film resistance film 24 is left covered. Therefore, if the thin film resistance film 24 remains in the dividing groove 22, a parallel resistance is formed between adjacent elements, and it becomes impossible to correct the resistance value to a target resistance value. In addition, if the parallel resistance is partially left even if it is not formed, the plating will adhere to that part in the final electrode plating step,
The appearance was also impaired. Therefore, in order to remove the resist remaining in the dividing groove 22, a resistance film removing process using a laser is required, which causes a problem of increasing the number of steps.

(2) When the exposure time in the photolithography process step is extended and a sufficient amount of light is given to the positive resist in the dividing groove 22 to make it soluble, the thin film resistance film 24 in the dividing groove 22 is formed in the etching step. Can be completely removed. However, the exposure time of the predetermined resistance pattern 25 is also extended at the same time, causing halation of light,
There are problems that the linearity is deteriorated and a disconnection failure occurs when the resistor has a narrow line width.

The present invention solves the above problems and provides a method for inexpensively manufacturing a small rectangular thin film chip resistor which prevents deterioration of linearity and occurrence of disconnection defects without increasing man-hours. The purpose is to do.

[0010]

In order to achieve the above object, a method of manufacturing a rectangular thin film chip resistor according to the present invention is provided with a plurality of vertical and horizontal dividing grooves so as to face each other. A step of forming a thin film resistance film on the back surface of the insulating substrate, a photolithography process step of forming the thin film resistance film in a predetermined resistance pattern, and a step of forming a chip resistor on the predetermined resistance pattern, In the photolithography process step, the resistance pattern is formed by performing exposure at least twice.

[0011]

According to the present invention, when the resistance pattern is formed by the thin film resistance film by using the insulating substrate having the dividing grooves on both surfaces by performing the exposure twice or more, the linearity thereof is deteriorated. Since the resist in the dividing groove can be completely exposed to light, the thin film resistance film in that portion can be completely removed. Further, since the insulating substrate having the dividing grooves on both sides, which is conventionally used in the thick film chip resistor, is used, it is possible to form a small rectangular thin film chip resistor having a good dividing shape.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a rectangular thin film chip resistor according to an embodiment of the present invention will be described below with reference to the process chart shown in FIG.

First, 96% excellent in heat resistance and insulation.
Step A of receiving the alumina substrate 1 is performed. This 96%
The front and back surfaces of the alumina substrate 1 are divided into strip-shaped and individual pieces so as to face each other in the vertical and horizontal dividing grooves 2 (molding at the time of green sheet).
Are formed. The formed dividing groove 2 is formed so that the front surface is deeper than the back surface in order to improve the individual divided shape in the subsequent dividing step. 1.0 × 0.
In order to manufacture a square thin film chip resistor of 5 mm square, the thickness of the alumina substrate 1 is 0.3 mm, and the size of each unit partitioned by the vertical and horizontal dividing grooves 2 is 1.0 × 0.5 mm. , The depth of the dividing groove 2 on the surface is about 150
μm, and the depth of the dividing groove on the back surface was about 30 μm. This is because the alumina substrate 1 serves as an insulating substrate used for the rectangular thick film chip resistor, and thus has the best divided shape.

Next, an electrode paste made of a metal organic material containing Au as a main component is screen-printed and dried on the front and back surfaces of the 96% alumina substrate 1. After that, in order to remove only the organic component of the metal organic electrode paste and burn only the metal component onto the alumina substrate 1, a belt type continuous firing furnace was used at a temperature of 850 ° C. for a peak time of 6 minutes, and the IN
Step B of forming a thin film upper surface electrode layer 3 and a thin film back surface electrode layer by firing according to a profile of -OUT time 45 minutes
I do.

Next, the entire back surface of the 96% alumina substrate 1 is filled with N.
Sputtering step C for forming a thin film resistance film 5 such as i-Cr
I do.

Next, a photolithography process step is performed to form the thin film resistance film 5 on the predetermined resistance pattern 6.
This photolithography process step will be described in detail.
First, a positive type resist is uniformly applied onto the thin film resistance film 5 and dried (step D), and then exposed. Here, the exposure is performed twice, and a photomask having a different pattern is used for each exposure. The first time, exposure is performed using a photomask designed to expose only the dividing groove 2 (step E). The exposure time at this time was set so that a sufficient amount of light was ensured so that all the resist applied in the dividing groove 2 was soluble. Next, the second exposure is performed using a photomask having a predetermined pattern 6 (step F). The exposure time at this time may be the same as the conventional setting.
This completes two exposures. By this method, the portion where the resistance pattern 6 is formed can be exposed only for the same time as the conventional one, and the dividing groove 2 can be sufficiently exposed. After that, etching (step H) is performed through development (step G) post-baking, and finally the resist is peeled off to form a thin film resistance film 5 of Ni—Cr formed on a predetermined resistance pattern 6.

Next, in order to form a stable film of the resistance pattern 6, a heat treatment step I at a temperature of 350 to 400 ° C. is performed in nitrogen.

Then, a resistance value correcting step J is performed by laser trimming in order to correct the resistance value of the resistance pattern 6 to a predetermined value.

Next, in order to protect the resistance pattern 6 whose resistance value has been corrected, an epoxy resin paste is screen-printed and heat-cured to form a protective coat 7.

Then, a primary dividing step L for dividing the 96% alumina substrate 1 into strip substrates 1a is performed, and the thin film upper surface electrode layer 3 is formed on the end face of the strip substrate 1a by sputtering.
An end face electrode forming step M for forming the Ni—Cr-based thin film end face electrode layer 8 is performed so as to connect the thin film back face electrode layer with.

Finally, the strip-shaped substrate 1a is replaced with the individual substrate 1b.
A secondary dividing step N is performed to divide the exposed thin film upper surface electrode layer 3, thin film back surface electrode layer, and thin film end surface electrode layer 8 to prevent electrode erosion during soldering and ensure reliability during soldering. Therefore, by electrolytic plating, Ni, Sn-Pb
The electrode plating step O for forming the plating layer 9 is performed.

By the steps described above, the thin film resistance film 5 is not left in the dividing groove 2 generated by the conventional manufacturing method, and the linearity of the resistance pattern 6 is deteriorated by changing the exposure process. Moreover, the product division shape after division can be made equal to the conventional one.

Although the resistor is formed on the back surface of the alumina substrate 1 in the present invention, the same effect can be obtained by using the front surface. In this case, since the dividing groove 2 is deep, the exposure time in the first exposure (the dividing groove 2 portion) may be set longer than when the back surface is used. In general, the insulating substrate used for the rectangular thick film chip resistor is formed such that one surface has a greater depth of the dividing groove 2 than the other surface to improve the dividing shape. ing. Therefore, when using this insulating substrate, it is advantageous to use the shallow back surface of the dividing groove 2. Further, the same effect can be obtained when the depth of the division groove 2 on the back surface is deeper than 30 μm, but the division shape is the best in the square thick film chip resistor when the depth is 30 μm. It is more advantageous that the dividing groove on the surface on which the resistance pattern is formed is shallower in consideration of the photolithography process step, but since the dividing shape must be taken into consideration, 30 μm is most suitable.

In the present invention, an example of a rectangular thin film chip resistor of 1.0 × 0.5 mm square is shown, but the present invention can be applied to a larger shape.

Further, although the alumina substrate 1 is used as the insulating substrate in the present invention, other substrates may be used as long as they have insulating properties.

[0026]

As described above, according to the present invention, since the division groove portion and the resistance pattern portion are separately exposed, the thin film resistance film in the division groove is completely removed, and a straight line having a predetermined resistance pattern is formed. The resistance pattern having excellent properties can be formed, and the defect rate in the resistance pattern forming step can be reduced. Moreover, since an insulating substrate having split grooves on both sides, which has been conventionally used in large amounts in thick film chip resistors, can be used, and the conventionally required resistance film removing step can be eliminated, the manufacturing cost is greatly reduced. (It is possible to significantly reduce the number of steps and improve the productivity by increasing the number of exposure steps rather than the resistance film removing step). Further, since the insulating substrate having the dividing grooves on both sides is used, it is possible to inexpensively supply a small-sized rectangular thin film chip resistor having a good dividing shape and excellent mountability.

[Brief description of drawings]

FIG. 1 is a process diagram showing a method of manufacturing a prismatic thin film chip resistor according to an embodiment of the present invention.

FIG. 2 is a process diagram showing a method of manufacturing a conventional rectangular thin film chip resistor.

[Explanation of symbols]

 1 Alumina substrate 2 Dividing groove 3 Thin film upper surface electrode layer 5 Thin film resistance film 7 Protective coat 8 Thin film end face electrode layer 9 Plating layer

Claims (3)

[Claims] 1. A step of forming a thin film resistance film on the back surface of an insulating substrate provided with a plurality of vertical and horizontal dividing grooves so as to face each other on the front and back surfaces, and the thin film resistance film having a predetermined resistance pattern. And a photolithography process step of forming a chip resistor on the predetermined resistance pattern. In the photolithography process step, a rectangular thin film chip resistor for forming a resistance pattern by performing at least two exposures. Manufacturing method. 2. The method of manufacturing a rectangular thin film chip resistor according to claim 1, wherein the insulating substrate has a depth of the dividing groove provided on the back surface thereof smaller than that of the dividing groove provided on the front surface. 3. The method of manufacturing a rectangular thin film chip resistor according to claim 1, wherein only the dividing groove is exposed at least once.