Active solid-state devices (e.g. – transistors – solid-state diode – Responsive to non-electrical signal – Magnetic field
Reexamination Certificate
2001-12-06
2004-04-20
Wilson, Scott R. (Department: 2826)
Active solid-state devices (e.g., transistors, solid-state diode
Responsive to non-electrical signal
Magnetic field
C257S421000, C257S423000, C438S077000
Reexamination Certificate
active
06724059
ABSTRACT:
DESCRIPTION
1. Technical Field
The present invention relates to a very thin magnetoelectric transducer, and more specifically, to a small magnetoelectric transducer which allows the correctness of its mounting to be determined without being destroyed and that allows magnetoelectric transducers to be easily formed.
Furthermore, the present invention relates to a method for producing a very thin magnetoelectric transducer, and more specifically, to a method for producing a small magnetoelectric transducer which allows the correctness of its mounting to be determined nondestructively and that allows magnetoelectric transducers to be easily formed.
2. Background Art
Hall elements, which are among the magnetoelectric transducers, are widely used as rotational position sensors for drive motors for VTRs, flexible disks, CD-ROMs, and the like or as potentiometers or gear sensors. Owing to the trend to reduce the sizes of these electronics, there is a growing demand for a reduction in the thickness of Hall elements.
The current common Hall elements are produced as follows: First, a magnetoelectric transducer is constructed that is composed of a thin semiconductor film that has internal electrodes and that senses magnetism. Then, the magnetoelectric transducer is secured to a portion call an “island portion” of a lead frame, and the lead frame and the inner electrodes are connected together with metal wires. Then, a portion of the lead frame which covers the magnetoelectric transducer is molded using a resin. Subsequently, steps including deburring, lead formation, and electromagnetic inspections are executed.
FIGS. 7A and 7B
show the appearance of the relatively small element described above as an example of an element produced in the above manner.
FIGS. 7A and 7B
are a side view and a plan view, respectively. This element has a height h of 0.8 mm and a width w of 1.25 mm. The length L and width W of this element, including a lead frame, are each 2.1 mm.
The smallest commercially available Hall elements, including a lead frame that functions as an external electrode after mounting, have outside dimensions including a height of 0.6 mm on a projected area of
2.5×l.5
mm or a height of 0.55 mm on a projected area of 2.1×2.1 mm. These elements are characterized by their small height.
To further reduce the size of the element, a tape carrier method that uses no intervening lead frames has been proposed. This method comprises connecting the electrode portion of the magnetoelectric transducer to a tape via bumps to mount it on a substrate. This method is still limited by the thickness of the tape.
The present invention is provided in view of these problems, and it is an object thereof to provide a very thin magnetoelectric transducer that allows the correctness of its mounting to be determined nondestructively, as well as a production method therefor.
It is another object of the present invention to provide a magnetoelectric transducer that allows a magnetoelectric transducer to be easily formed and that is of a pellet size, that is, has a size substantially equal to that of a pellet, as well as a production method therefor.
DESCRIPTION OF THE INVENTION
After wholehearted examinations, the inventors have concluded that notably the size and thickness reductions on the projected area are limited as long as a lead frame such as the one described previously is used. Even if the magnetoelectric transducer has a mold size of about 1.5×1.5 mm, lead frames projecting from the element must be formed so as to be suited for mounting. Thus, these projecting parts pose a problem. Further, since the reduction of the thickness of the lead frames is limited and the front and back sides of the lead frames must be covered with a mold resin, the reduction of the height is limited.
The present invention is based on this conclusion, and makes the size of the entire magnetoelectric transducer, including mounted electrodes, substantially equal to the mold size.
That is, a magnetoelectric transducer according to the present invention is characterized in that the element comprises a magnetosensitive section and internal electrodes formed on an upper surface of any insulating substrate having conductive layers formed on side surfaces thereof, an insulating portion and each of the conductive layers are formed of a sintered compact, the sintered compact of the conductive layer is mainly composed of metal of a high melting point of 1,600° C. or higher and ceramic powders, and the sintered compact of the conductive layer contains 10% to 90% of the high-melting-point metal.
Further, the magnetoelectric transducer according to the present invention is characterized in that the high-melting-point metal is W, Mo, Ta, or a mixture thereof, and the sintered compact of the insulating layer is a substrate composed of alumina.
Furthermore, the magnetoelectric transducer according to the present invention is characterized in that an adhesive resin layer or an inorganic layer is formed on a upper surface of the insulating substrate, and the magnetosensitive layer and each of the internal electrodes are formed thereon.
Moreover, the magnetoelectric transducer according to the present invention is characterized in that the sintered compact of the conductive layer and each internal electrode, separated from each other at least via a step of the adhesive resin layer or the inorganic layer, are electrically connected together using a conductive resin or a metal material.
Further, the magnetoelectric transducer according to the present invention is characterized in that an inorganic layer is formed on the upper surface of the insulating substrate, and an InSb-based thin film having an electron mobility of 10,000 cm
2
/V/sec. or more is formed on the inorganic layer. The inorganic layer may be made of silica, alumina, or glass.
Furthermore, the magnetoelectric transducer according to the present invention is characterized in that a resin layer is formed on the upper surface of the insulating substrate, and an InSb-based thin film having an electron mobility of 20,000 cm
2
/V/sec. or more is formed thereon.
Moreover, the magnetoelectric transducer according to the present invention is characterized in that a metal coat is formed at least on a surface of the sintered compact of the conductive layer.
Further, the magnetoelectric transducer according to the present invention is characterized in that a strain buffering layer is formed on the magnetosensitive section, and a protective film is formed thereon.
Furthermore, a method for producing a magnetoelectric transducer according to the present invention is characterized by comprising the steps of forming a thin film that senses magnetism, on a surface of an insulating substrate via an insulating layer, the substrate having a conductive layer formed therein and mainly composed of a high-melting-point metal layer and ceramic powders in a thickness direction of the substrate, a sintered compact of each of the conductive layers containing 10% or more to 90% of the high-melting-point metal; forming a large number of magnetosensitive sections and internal electrodes of metal on the thin film in a pattern of final elements to collectively form a large number of magnetoelectric transducers; cutting the insulating layer on the conductive layer of the substrate; electrically connecting the internal electrodes and conductive layers of each of the magnetoelectric transducers together; forming a protective layer at least on the magnetosensitive section; and cutting a central portion of each of the conductive layers of the substrate to individualize a large number of magnetoelectric transducers.
Moreover, a method for producing a magnetoelectric transducer according to the present invention is characterized by comprising the steps of forming a thin film that senses magnetism, on a surface of an insulating substrate via an insulating layer, the substrate having a conductive layer formed therein and mainly composed of a high-melting-point metal layer and ceramic powders in a thickness
Asahi Kasei Electronics Co. Ltd.
Finnegan Henderson Farabow Garrett & Dunner LLP
Wilson Scott R.
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