Active solid-state devices (e.g. – transistors – solid-state diode – Integrated circuit structure with electrically isolated... – Passive components in ics
Reexamination Certificate
2001-06-05
2004-03-09
Zarabian, Amir (Department: 2822)
Active solid-state devices (e.g., transistors, solid-state diode
Integrated circuit structure with electrically isolated...
Passive components in ics
C257S775000, C338S309000, C338S332000
Reexamination Certificate
active
06703683
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a chip resistor in which a resistor film is provided on a chip-type insulating substrate and a manufacturing method thereof. More specifically, the present invention relates to a chip resistor and a manufacturing method thereof, wherein the manufacturing process is simple to enable economical production, while high-performance properties can be obtained.
BACKGROUND OF THE INVENTION
Conventional chip resistance element include a thick-film resistor wherein electrodes and resistance element are formed by printing and firing, and a thin-film resistor wherein electrodes and resistance element are formed by sputtering. Though there are differences in the thick film and the thin film, and in the upper and lower sides of the resistance element and the top electrodes, the structures thereof are almost the same, and for example, are as shown in FIG.
14
. That is to say, in
FIG. 14
, a pair of electrodes
2
,
3
are formed of top surface electrodes
21
,
31
, back surface electrodes
22
,
32
, and side surface electrodes
23
,
33
connecting these top and back surface electrodes, at both of the opposite ends of an insulating substrate
1
comprising alumina or the like, and a resistance element
4
is formed on the insulating substrate
1
, so as to be connected to the both electrodes. A protective film
5
is also formed in one to three layers on the surface side of the resistance element. The thick film is formed in a thickness of, for example, 5 to 10 &mgr;m, and the thin film is formed in a thickness of, for example, 0.1 to 0.5 &mgr;m.
The thick-film resistor is obtained by applying a paste material by printing or the like using a glass or a resin, and firing the material at 600 to 900° C. (in the case of glass) or curing this at 200 to 240° C. (in the case of resin), to thereby form each layer. As an electrode material, a metal paste of an Ag type in which Pd is added to Ag, or an Au type in which Au is used as a main component is used. As a resistance element material, there is used one obtained by mixing Ag or the like in ruthenium oxide (RuO
2
) in order to have a necessary value of resistance, and forming a paste by a glass or a resin. Also, the thin-film resistor is obtained by forming a film from a metal material by sputtering or the like and patterning this film. As the electrode material, Al, Ni, Cr or Cu is used, and as the resistance element material, an Ni—Cr alloy or the like is used.
Thus, the manufacturing processes are different in that one is provided by printing and heat processing, and the other is provided by sputtering. Also these are different in view of equipment such as printing apparatus or sputtering apparatus, and the production line is quite different. Therefore, use of the both films together makes the production process complicated, and it is practically difficult.
As described above, there is a thick-film resistor or a thin-film resistor in chip resistor, and the thick-film resistor has an advantage in that the production equipment is very cheap, and such a resistor itself can be manufactured economically. However, since the resistance element is obtained by making a paste of ruthenium oxide, the accuracy of resistance value is poor based on the heterogeneous composition, the non-uniform thickness at the time of application, and a difference in dosage of Ag or the like in order to adjust the resistance value, and there is a problem in that it is inferior in performance, such as poor noise performance, as well. On the other hand, the thin-film resistor is excellent in the accuracy of resistance value and noise performance, but there is a problem in that expensive sputtering apparatus has to be used, and its production takes time, thereby making such a resistor considerably expensive.
On the other hand, if the thick film and the thin film are combined, not only the production line becomes complicated as described above, but also there are problems in that when a thick film is formed on a thin film, adhesion decreases, contact resistance increases, and the quality thereof is not uniform, though there is no problem in adhesion when a thin film is formed on a thick film.
SUMMARY OF THE INVENTION
In order to solve these problems, it is an object of the present invention to provide a chip resistor and a manufacturing method thereof, wherein accuracy of resistance value is improved, and productivity is improved, while increasing resistance characteristics such as noise performance.
It is another object of the present invention to provide a chip resistor capable of surface mounting, while improving a connection between a resistance element and electrodes, in case that a thin-film is used as the resistance element, and a thick-film is used as the electrodes.
The chip resistor according to the present invention comprises: an insulating substrate; a resistance element formed by a thin film so as to extend from one end to the opposite other end of the insulating substrate on the surface thereof; top surface electrodes formed by a thick film at the opposite ends of the insulating substrate, so as to be connected to the opposite ends of the resistance element, respectively; back surface electrodes formed by a thick film on the backside of the insulating substrate, the back surface electrodes being electrically connected to the top surface electrodes via thick-film electrodes, respectively; and a protective film provided on the surface of the resistance element.
The thick film herein stands for a film formed thick by applying materials of an electrode or a resistance element in a paste form and firing or curing this paste, and the thin film stands for a film formed thin by directly forming a metal film or the like by sputtering or the like.
By having such a construction, since a resistance element is formed by a thin film, the resistance performance such as accuracy of resistance value and noise performance can be obtained with high accuracy. On the other hand, since electrodes and the like are formed by a thick film, the production process becomes simple, enabling economical production.
Specifically, the construction may be such that each of the top surface electrodes comprises a first top surface electrode and a second top surface electrode, and each of the opposite ends of the resistance element is clamped in a sandwich construction by the first top surface electrode and the second top surface electrode provided on the surface of the insulating substrate, with a part of each of the opposite ends of the resistance element removed so that the first top surface electrode and the second top surface electrode come in direct contact with each other, and the second top surface electrode and each of the back surface electrodes are connected by a side surface electrode formed by a thick film on the side of the insulating substrate, respectively.
By having such a construction, a part of the resistance element is removed so that the first top surface electrode and the second top surface electrode come in direct contact with each other, and the first top surface electrode and the second top surface electrode are both formed by a thick film. Hence, these have excellent adhesion. The resistance element sandwiched therebetween has excellent adhesion with the first top surface electrode, since it is a thin film on a thick film, and can be also connected electrically with the second top surface electrode via the first top surface electrode with low resistance. As a result, even if a side surface electrode or a bump electrode is provided in a thick film on the second top surface electrode, both of the second top surface electrode and the side surface electrode are similarly thick film and have good adhesion. Hence, an electrode structure having excellent contact state can be obtained.
Another specific construction may be such that the resistance element formed by a thin film comprises a laminated structure having a first layer and a second layer, each of the opposite ends of the resistance element clamps the top surface
Arent Fox Kintner & Plotkin & Kahn, PLLC
Perkins Pamela E
Rohm & Co., Ltd.
Zarabian Amir
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