JP3092451B2 - Rectangular thin film chip resistor and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In recent years, with the downsizing of electronic devices, there has been an increasing demand for smaller electronic components to be mounted in order to increase the mounting density of circuit boards. Along with the miniaturization of square chip resistors, the demand for square thin film chip resistors having high accuracy (resistance tolerance, resistance temperature characteristics) and excellent current noise characteristics is increasing.

FIG. 3 is a cross-sectional view showing the structure of a conventional rectangular thin-film chip resistor, and FIG.

The structure of a product will be described with reference to FIG. A pair of thin film upper electrode layers 12 made of Au formed on the surface of a square 96% alumina substrate 11 and Au formed on the back surface
A thin-film resistor layer 14 made of Ni-Cr alloy, which covers the pair of thin-film upper electrode layers 12 and is formed between the thin-film upper-electrode layers 12; An epoxy-based resin protective film layer 15 completely covering 14 and a Ni-Cr alloy formed on both end surfaces of the 96% alumina substrate 11 so as to connect the exposed thin film resistor layer 14 and the thin film back electrode layer 13 to each other. And an electrode plating layer 18 made of nickel and solder formed on the exposed electrode portion.

Next, the steps will be described with reference to FIG. First, 9
An insulating substrate 11 made of 6% alumina is prepared. next,
An electrode paste composed 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 11, and then fired in a belt-type continuous firing furnace to remove only the organic components of the metal organic material electrode paste. A step of forming the thin film upper electrode layer 12 and the thin film rear electrode layer 13 by baking only the metal component on the alumina substrate 11 is performed.

Next, Ni-C is applied to the entire upper surface of the insulating substrate 11.
The thin film resistor layer 14 is subjected to a sputtering process for forming a thin film resistor layer 14 such as a r.
Photolithography process (resist coating and drying, exposure, development, etching, resist stripping)
In order to make the resistance pattern 14a a stable film,
A heat treatment process is performed in a 400 ° C. atmosphere. Thereafter, a resistance value correcting step is performed by laser trimming to correct the resistance value of the resistance pattern to a predetermined value.

[0007] Next, the resistance value corrected resistance pattern 14b
Is formed, a step of forming a resin protective film layer 15 of a thermosetting resin is performed. Next, an end face electrode forming step of forming the thin film end face electrode layer 17 is performed by using sputtering on the end face of the insulating substrate 11. Finally, an electrode plating step of forming an electrode plating layer 18 on the exposed electrode portion to ensure reliability at the time of soldering was performed to form a rectangular thin film chip resistor.

[0008]

In the structure of the conventional thin film chip resistor, the thin film resistor layer is covered with a resin protective film layer, and an electrode plating layer is formed on the exposed electrode portion.
If sufficient adhesion is not formed at the boundary between the resin protective film layer and the electrode plating layer, the thin-film resistor layer is likely to be affected by the outside. Even if the thin film resistor layer has sufficient adhesion, a gap is formed at the boundary due to thermal stress when actually used in a state where the thin film resistor layer is mounted on an electronic device, and the thin film resistor layer is easily affected by the outside. When an influence from the outside, that is, moisture and Na ions, Cl ions, K ions, Ca ions, etc. penetrates and an electric field is applied, corrosion of the thin-film resistor layer, so-called electrolytic corrosion, occurs, thereby changing the resistance value. In the worst case, there is a problem that a resistance open (disconnection) failure occurs.

Although the thin-film resistor layer is covered with the resin protective film layer, the exposed portions (the portions other than the resin protective film layer) are exposed to the plating solution when forming the electrode plating layer. Naturally, there is a danger of the plating solution entering from the boundary between the thin film upper electrode layer connected to the thin film resistor layer, particularly the resin protective film layer. In this case as well, a change in resistance value occurs as described above.

[0010] The present invention solves the above-mentioned problems, and provides electrical characteristics and
An object of the present invention is to provide a rectangular thin film chip resistor excellent in characteristics such as moisture resistance.

[0011]

In order to achieve the above object, a rectangular thin-film chip resistor according to the present invention comprises a pair of thin-film upper electrode layers formed on a main surface of a rectangular insulating substrate, and a pair of thin-film upper electrode layers. A thin-film resistor layer formed between the thin-film upper electrode layers so as to overlap the respective electrode layers, a resin protective film layer covering the thin-film resistor layer, and covering the pair of thin-film upper electrode layers or the thin-film resistor layers; A pair of conductive resin upper surface electrode layers formed so as to partially overlap both ends of the resin protective film layer, and a pair of thin films respectively formed at both end portions of the insulating substrate so as to overlap the pair of conductive resin upper surface electrode layers, respectively; It has an end face electrode layer and an electrode plating layer formed on the exposed conductive resin top electrode layer and the thin film end face electrode layer.

[0012]

According to the present invention, the thin-film resistor layer is covered with the resin protective film layer, and the thin-film upper electrode layer connected to the thin-film resistor layer is overlapped with a part of both ends of the resin protective film layer. Since the electrode layer is formed, the thin film resistor layer is not affected by the plating solution in the plating step. In addition, since the resin protective film layer and the conductive resin upper electrode layer are made of a resin material, the adhesiveness between the conventional protective film layer and the electrode plating layer is superior to that of the conventional protective film layer. It is possible to realize a rectangular thin-film chip resistor in which a change in resistance value (including disconnection) due to corrosion hardly occurs.

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a rectangular thin film chip resistor according to an embodiment of the present invention;

FIG. 1 is a sectional view of a rectangular thin film chip resistor according to one embodiment of the present invention, and FIG. 2 is a process chart showing a method of manufacturing the same.

The structure of the product will be described with reference to FIG. A pair of thin-film upper electrode layers 2 of Au formed on the surface of a square 96% alumina substrate 1, a pair of thin-film rear electrode layers 3 of Au formed on the back surface, and a pair of thin-film upper electrode layers 2 Ni-covered and formed between the thin film top electrode layers 2
A thin film resistor layer 4 made of a Cr alloy, an epoxy resin protective film layer 5 completely covering the thin film resistor layer 4, and a resin covering the thin film resistor layer 4 exposed on the pair of thin film upper electrode layers 2; A pair of conductive resin upper electrode layers 6 formed so as to partially overlap both ends of the protective film layer 5, and a 96% alumina substrate 1 on both sides so as to connect the conductive resin upper electrode layer 6 and the thin film rear electrode layer 3. It comprises a pair of thin-film end face electrode layers 7 respectively formed on the end faces, an exposed thin-film back face electrode layer 3, a conductive resin top electrode layer 6, and an electrode plating layer 8 formed of nickel and solder formed on the thin-film end face electrode layer 7. You.

Next, the manufacturing method will be described with reference to FIG. First, a step A of preparing a 96% alumina substrate 1 having excellent heat resistance and insulation properties is performed. Next, after an electrode paste composed 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,
In order to remove only the organic components of the electrode paste made of a metal organic material and bake only the metal components on the 96% alumina substrate 1, a belt-type continuous firing furnace at a temperature of 850 ° C. was used for a peak time of 6 minutes and an IN-OUT time of 45 minutes. A process B is performed in which the thin film top electrode layer 2 and the thin film back electrode layer 3 are simultaneously formed by baking according to a minute profile.

Next, Ni-Cr is placed on a 96% alumina substrate 1.
And a photolithography process D (resist coating / drying, exposure, development, etching, resist peeling) for forming the thin film resistor layer 4 into a predetermined resistance pattern 4a through the sputtering process C for forming the thin film resistor layer 4 of FIG. Then, in order to make the resistance pattern 4a a stable film, 350 to 400
A heat treatment step E is performed in a temperature atmosphere of ° C.

Thereafter, a resistance value correcting step F is performed by laser trimming to correct the resistance value of the resistance pattern 4a to a predetermined value.

Next, a resin paste is screen-printed to protect the resistance-corrected resistance pattern 4b.
Step G of forming a resin protective film layer 5 by thermosetting with a profile of 00 ° C. for 30 minutes is performed.

Next, Ag is contained as a conductive metal material so as to cover the resistance-corrected resistance pattern 4b which is not covered with the resin protective film layer 5 and to partially overlap both ends of the resin protective film layer 5. Screen printing of conductive resin paste,
Step H of forming the conductor resin upper surface electrode layer 6 by thermosetting with a profile of 200 ° C. for 30 minutes is performed.

Here, it is indispensable that the resin protective film layer 5 and the conductive resin upper surface electrode layer 6 are formed by printing and thermosetting individually. That is, when the respective portions of the resin protective film layer 5 and the conductive resin upper surface electrode layer 6 are printed and thermally cured simultaneously in a temporarily dried state (that is, when the number of manufacturing steps is reduced by performing only one thermal curing step), Once each of them is softened by heat and then starts hardening by a crosslinking reaction, mutual diffusion occurs between the resin protective film layer 5 as an insulating material and the conductive resin upper surface electrode layer 6 as a conductive material, and the resin is protected. Membrane layer 5
In this case, the desired function cannot be achieved due to a decrease in insulation resistance and an increase in conductor resistance in the conductor resin upper electrode layer 6.

Next, an end face electrode forming step I of forming a Ni—Cr thin film end face electrode layer 7 on the end face of the 96% alumina substrate 1 by sputtering is performed.

Finally, in order to prevent electrode erosion during soldering and to ensure reliability during soldering, the exposed thin film back electrode layer 3, conductive resin upper electrode layer 6, and thin film end electrode layer 7 are An electrode plating step J of forming a plating layer 8 of Ni and Sn-Pb by electroplating is performed.

Through the above steps, a rectangular thin-film chip resistor according to an embodiment of the present invention was manufactured on a trial basis. When the rectangular thin film chip resistor of the present invention and a conventional rectangular thin film chip resistor were compared by a moisture resistance load life test, the results shown in FIG. 4 were obtained. That is, in the conventional product, a resistance value change (0.5% or more) occurred in 1000 hours, but in the developed product according to the present invention, the resistance value change was almost 0%.

In this embodiment, the thin film resistor layer is made of Ni-
Although made of a Cr-based metal material such as Cr, Cr-Si, Cr-Al, etc., if the thickness of the thin-film resistor layer is reduced in order to increase the sheet resistance, extremely electrolytic corrosion occurs. It is particularly effective to form a rectangular thin-film chip resistor by the structure and manufacturing method according to the present embodiment because it is a material that is easy to perform.

Although the conductive resin upper electrode layer is formed of a silver-based resin material, this does not define a conductive metal material, and all materials used as electrode materials such as copper and gold have the same effect. Needless to say, this is obtained.

In this embodiment, the thin-film upper electrode layer 2 is covered with the thin-film resistor layer 4, but the same effect can be obtained even when the thin-film resistor layer 4 overlaps only a part of the thin-film upper electrode layer 2. can get.

The same effect can be obtained without the thin film back electrode layer 3.

[0029]

As described above, according to the present invention, the thin film resistor layer is covered with the resin protective film layer, and one end of the resin protective film layer is formed on the thin film upper electrode layer connected to the thin film resistor layer. Since the conductive resin upper electrode layer is formed so as to overlap the portion, the thin film resistor layer is not affected by the plating solution in the plating step. Furthermore, since the protective film layer and the conductive resin upper electrode layer are made of a resin material, the adhesiveness between the protective film layer and the electrode plating layer is superior, so that the protective film layer is less susceptible to external influences, and the resistance value due to electrolytic corrosion is reduced. It is possible to realize a highly reliable rectangular thin film chip resistor in which a change (including a disconnection) does not easily occur.

According to the present invention, the following effects can be obtained in addition to the above effects. (1) In the case of forming a small rectangular thin film chip resistor, by providing the conductive resin upper electrode layer, there is no step between the resin protective film and the upper electrode layer, and the adsorption area at the time of mounting is increased, so mounting is performed. Performance can be improved. (2) Cr-based metals such as Ni-Cr are present in the thin-film resistor layer, but these are easily oxidized, so that a heat treatment in a nitrogen atmosphere is required. However, when a conductor resin upper electrode layer with a lower conductor resistance than the thin film upper electrode layer was provided, the thin film resistor layer was heat-treated in air to form an oxide film on the surface. Even so, it is possible to manufacture a rectangular thin-film chip resistor inexpensively because of good plating coverage.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a structure of a rectangular thin film chip resistor according to an embodiment of the present invention.

FIG. 2 is a process chart showing a method of manufacturing the rectangular thin film chip resistor in the embodiment.

FIG. 3 is a cross-sectional view showing the manufacture of a conventional rectangular thin film chip resistor.

FIG. 4 is a comparative diagram showing a resistance value change rate of the same example and a conventional rectangular thin film chip resistor.

FIG. 5 is a process chart showing a method of manufacturing a conventional rectangular thin film chip resistor.

[Explanation of symbols]

 1 96% alumina substrate 2 Thin film top electrode layer 3 Thin film back electrode layer 4 Thin film resistor layer 5 Resin protective film layer 6 Conductive resin top electrode layer 7 Thin film end face electrode layer 8 Electrode plating layer

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-45118 (JP, A) JP-A-5-267025 (JP, A) JP-A-62-156801 (JP, A) JP-A-7-57 169601 (JP, A) JP-A-7-176402 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01C 7/00 H01C 17/00-17/30

Claims (4)

(57) [Claims] A pair of thin film upper electrode layers formed on a main surface of a rectangular insulating substrate; a thin film resistor layer formed between the thin film upper electrode layers so as to overlap each of the pair of thin film upper electrode layers; A resin protective film layer covering the thin film resistor layer,
A pair of conductive resin upper surface electrode layers formed to cover the pair of thin film upper electrode layers or the thin film resistor layers and to partially overlap both ends of the resin protective film layer, and the pair of conductive resin upper electrode layers, respectively; A rectangular thin-film chip resistor comprising: a pair of thin-film end face electrode layers respectively formed on both ends of an insulating substrate so as to overlap with an insulating substrate; and an electrode plating layer formed on the exposed conductive resin top electrode layer and thin-film end face electrode layer. 2. The rectangular thin-film chip resistor according to claim 1, wherein the thin-film resistor layer is made of a Cr-based metal material. 3. A step of forming a pair of thin film upper electrode layers on a main surface of a rectangular insulating substrate, and forming a thin film resistor layer between the thin film upper electrode layers so as to overlap each of the pair of thin film upper electrode layers. And a step of forming a resin protective film layer so as to cover the thin film resistor layer, and covering the pair of thin film upper electrode layers or the thin film resistor layer and forming a part of both ends of the resin protective film layer. Forming a pair of conductive resin upper surface electrode layers so as to overlap, forming a pair of thin film end surface electrode layers at both end portions of the insulating substrate so as to overlap the pair of conductive resin upper surface electrode layers, respectively, Forming an electrode plating layer on the conductive resin upper surface electrode and the thin film end surface electrode layer. 4. The method for manufacturing a rectangular thin film chip resistor according to claim 3, wherein the resin protective film layer and the conductive resin upper electrode layer are individually hardened and formed.