JP2668239B2 - Magnetic sensor - Google Patents

Description

The present invention relates to an improvement of a magnetic sensor used as a non-contact type displacement sensor or the like.

(Prior Art) A non-contact displacement sensor using a magnetoresistive element is known as a sensor that detects the position of a movable part in various OA equipment, home electric appliances, and the like and converts the detected information into an electric signal. .

2 (a), 2 (b) and 2 (c) show an example of a conventional magnetoresistive element as a non-contact displacement sensor, and a sensing unit 2 connected in series to a substrate 1 of alumina, glass or the like.
3 are integrally fixed adjacent to each other, and
The first to third lead terminals 4, 5, and 6 are connected to the outer end portions and the intermediate connecting portions of the first and second lead terminals, respectively. The sensing elements (quadrant elements) 2 and 3 are, for example, In—Sb thin film raster plate type magnetoresistive elements, and have the same magnetic characteristics.

When magnetic fields having different magnitudes are applied to the two sensing element elements 2 and 3, respectively, the electrical midpoint moves. Only the resistance of the sensing element 2 or 3 located immediately below the magnetic pole increases due to the magnetoresistance effect. Utilizing this property,
The magnet 7 is contacted with the fixed sensing element in a non-contact state x
By arranging the magnet 7 so as to be movable in any direction, the movement of the magnet 7 can be detected as a relative displacement between the sensing unit elements 2 and 3 and the magnet 7.

FIG. 3A is a cross-sectional view of the vicinity of the sensing element 2 in the conventional magnetic sensor, and shows the electrode pattern on the substrate 1.
10 and the electrode pattern
The lead terminals 4 are fixed to the solder 10 with solder 11, and the entire surface is covered with a protective plate 12 such as a glass thin plate, and fixed with a resin adhesive or the like. However, with such a configuration of the protective plate, it is difficult to bring the protective plate 12 into close contact with the sensing element 2 and the soldering portion 11, and the protective plate is
12 Since it is easy for outside air to enter through the gap formed below, oxidation of the element due to moisture could not be prevented. Also,
Although the lead terminals 4, 5, and 6 were fixed by soldering, sufficient strength could not be obtained by soldering.

FIG. 3 (b) shows that only the upper surface of the element 2 is covered with the protective plate 12, while the soldered portion 11 is covered with the epoxy resin 13. For this reason, the connection strength at the soldered portion 11 can be improved. However, in this case as well, oxidation of the element 2 due to invasion of moisture cannot be prevented, and the lead terminals 4, 5, and 6 are fixed by soldering, but the connection strength of the terminals is actually increased. Since the adhesive 13 is responsible for this, it is not suitable for applications requiring large terminal strength.

Further, in any of the above-described embodiments, since the elements and the like project from the substrate 1, the overall thickness of the sensor increases, which is an obstacle to miniaturization.

Furthermore, when the arrangement of the pair of sensing element elements 2 and 3 is performed, since there is no reference element, it is difficult to accurately arrange the magnet 7 along the moving direction x.

(Object of the Invention) The present invention has been made in view of the above, and an object of the present invention is to provide a magnetic sensor capable of reducing the overall thickness and improving the moisture resistance.

(Summary of the Invention) In order to achieve the above object, the present invention provides a magnetic sensor using a sensing element having a magnetoresistive effect, wherein the sensing element is provided on a printed circuit board having a pattern wiring on its upper surface. It is positioned in the formed recess, and is connected to the outside via a lead terminal disposed in close contact with the pattern wiring on the upper surface of the printed board to the inner wall of the recess, and furthermore, the sensing portion in the recess is provided. The element is formed by laminating and filling a filler having a moisture resistance effect. The recess has a recess main body having a predetermined depth and a predetermined diameter in which the sensing element can be fitted. And a mortar portion continuously formed downward from the lower end of the main body.

Also, by mounting a thermistor for temperature compensation on the upper surface of the printed circuit board and connecting it to the sensing element, the current flowing into the sensing element can be increased or decreased in response to a change in the ambient temperature, thereby increasing the sensing element. It is characterized in that the characteristic variation due to the temperature of the element is prevented.

(Example) Hereinafter, a magnetic sensor of the present invention will be described in detail with reference to the accompanying drawings.

1 (a) and 1 (b) are a plan view and a cross-sectional view taken along the line AA, respectively, showing a configuration of an embodiment of the present invention. This magnetic sensor comprises a printed board 20 and a recess formed on the board 20. 21, a magnetic sensor chip (sensing element) 22 housed in the bottom surface of the recess 21, and lead terminals 23a, 23b, 23c wired from the upper surface of the sensor chip 22 to the upper surface of the substrate 20 via the inner wall of the recess 21. When,
A moisture-proof agent (filler) 25 such as silicon, which fills the recess 21 and covers the sensor chip 22, and an epoxy resin seal that is laminated on the moisture-proof agent 25 and on the periphery of the recess to seal the entire opening of the recess. A blocking agent (filler) 26. On the printed circuit board 20, pattern wiring 27 connected to each lead terminal 23a, 23b, 23c
a, 27b, 27c are formed by the artwork. Each lead terminal 23a, 23b, 23c and each pattern wiring 27a, 27b, 27c
Is made by soldering.

A through hole 30 is formed at the end of each pattern wiring 27a, 27b, 27c, and the through hole 30 is a printed circuit board.
It penetrates through the back surface of 20 and is connected to the electrode 32 on the back surface of the substrate 20 through the conductive metal 31 deposited on the inner wall thereof.

Each of the lead terminals 23a, 23b, and 23c is bent at a right angle where it enters the recess 21 from the upper surface of the substrate 20 as shown in the figure, and is connected to the element 22 while closely contacting the inner wall of the recess 21. For this reason, it is possible to prevent the element 22 from floating or tilting due to external mechanical force or the like via the lead terminal.

Means for forming the recess 21 in the printed circuit board include NC,
Any means such as a router and a drilling machine may be used.

As the shape of the recess 21, a cylindrical shape is the simplest,
Any shape is acceptable. Also, the depth of embedding the element can be variously set, and can be set freely as long as the sensitivity is not reduced.

As the sensor chip 22, a semiconductor magnetoresistance element, a ferromagnetic magnetoresistance element, various Hall elements, and the like can be applied.

Note that the sealing agent 26 can be omitted as long as there is a sealing agent as the moisture proofing agent 25, and when the sealing agent 26 having moisture proofing is used, the moisture proofing agent can be omitted. it can. In addition, in the claims, the filler having a moisture resistance effect is a concept including a moisture resistance agent having a sealing effect and a sealing agent having a moisture resistance effect.

Processing means of the magnetic sensor having the above configuration will be described. For example, when a sensor chip 22 having a size of 2 × 5 mm is used, a processing tool such as a router is used at a predetermined position on a printed circuit board 20 having a thickness of 1.6 mm and an area of 20 × 10 mm, for example, using a processing tool such as a router. A recess 21 having a size of 0.5 mm, a width of 2 mm and a length of 5 mm is formed. By setting the shape and the forming direction of the recess to a predetermined value, the positional accuracy of the sensor chip 22 in the x and y directions can be enhanced.

In the magnetic sensor thus prepared, the sensor chip 22 is located at the bottom of the recess and the upper surface thereof
5. Sufficient moisture resistance can be obtained because the layers are sequentially coated with the epoxy resin 26.

Also, the sensor chip 22, the dampproof agent 25, the epoxy resin 26
Since it is flush with the printed circuit board 20 or only slightly protrudes, the thickness of the entire sensor can be reduced to the minimum necessary. For this reason, there is an advantage that it can be easily applied to various small devices.

By setting the shape and direction of the recess accurately in the x and y directions, it is possible to enhance the positional accuracy of the sensor chip mounted in the recess. In other words, the positional accuracy of the sensor chip is ensured only by embedding it in the recess.

Since the sensor chip 22 is integrated with the printed circuit board 20, the pattern wirings 27a, 27b, and 27c on the circuit board 20 are arbitrarily formed by artwork to select a position for connecting the magnetic sensor to an external circuit. The range expands,
The degree of freedom in circuit design can be increased.

The lead terminals of the magnetic sensor of the present invention are
It has a sufficient terminal strength because it is in close contact with the surface and the inner wall of the recess 21 and does not have a portion protruding like a free end from the substrate unlike the lead terminal of the conventional magnetic sensor. For this reason, the types of applicable devices are greatly expanded, and the marketability can be expanded.

Since the lead wire can be led out from the back surface of the printed circuit board by forming the through hole 30 in the printed circuit board, this magnetic sensor can be made into one independent component. Hybrid as a result of independent components
It can be used as an electronic component mounted on an IC.

Next, FIGS. 4 (a) and 4 (b) are a plan view and a sectional view showing the configuration of the second embodiment of the present invention, and the same parts as those of the first embodiment are represented by the same reference numerals and are duplicated. The description that has been given is omitted. The first embodiment is different from the first embodiment in that the bottom of the recess 21 is machined into a flat shape, whereas the second embodiment has a bottom formed in a mortar shape (or conical shape). ing. Further, the recess 21 of the second embodiment is different in the configuration in which the planar shape is circular.

Since the processing accuracy of the bottom surface of the recess 21 affects the accuracy of the mounting position of the sensor chip 22, the area 21 having a flat bottom surface as in the first embodiment is formed using a simple machine tool. Difficult to do. For example, in the case where the bottom surface of the recess is processed flat by a processing means such as an end mill, the curved surface of the bottom corner of the recess becomes serious due to the progress of wear of the drill. In particular, in a magnetic sensor used for detecting displacement, it is necessary to strictly set the tolerance with respect to the xyz axes to improve the mounting accuracy of the element.
The decrease in processing accuracy as described above causes the performance of the magnetic sensor to be significantly reduced.

This second embodiment provides a magnetic sensor capable of improving the positional accuracy of the sensor chip to be installed by forming the recess 21 by processing with low accuracy using a simple processing means. The purpose is.

5 (a) and 5 (b) are a partially enlarged view of FIG. 4 (b) and a plan view showing the installation state of the sensor chip.
21 is a concave body composed of straight walls (upper concave) 21
a, and a mortar portion (lower recess) 21b formed in a mortar shape below the recess main body 21a. The distance i from the upper end to the lower end of the recess main body 21a is set to be constant. The diameter d of the body 21a is dimensioned so that the four corners of the sensor chip 22 are brought into line contact with the wall surface of the recess body to be locked. In other words, the bottom surface of the sensor chip 22 is
By setting the diameter d of the recess so as to be fixed along the boundary between the a and the mortar portion 21b, the z-
Positioning in the y-direction can be performed appropriately, and the depth i of the sensor chip 22 (position in the z-axis direction) can be made constant by setting the depth i of the recess body to be constant.

Reference numerals 31 and 32 in FIGS. 4A and 4B denote guide holes for accurately attaching the printed circuit board 20 to an external device.

As described above, according to the second embodiment of the present invention, if the accuracy of the depth and the diameter of the recess main body 21a having a straight wall surface can be strictly set, the recess bottom surface is not flattened. By forming the sensor chip 22 into a mortar shape having an appropriate taper, appropriate positioning accuracy of the sensor chip 22 can be obtained. That is, the recess can be formed by cutting using a simple processing means.

Also, since the four corners of the sensor chip 22 having a rectangular parallelepiped form line contact with the inner wall of the recess main body 21a and the bottom surface of the sensor chip is locked at the boundary with the mortar portion 21b, the entire sensor chip is horizontal. Can be kept.

In the process of manufacturing the magnetic sensor of the second embodiment, for example, a wiring pattern is first formed on a single-sided copper foil printed board by etching, and then die cutting to a predetermined size is performed. Next, a recess 21 (21a, 21b) is formed at a predetermined position on the printed board with a predetermined depth and a predetermined diameter. Next, after the sensor chip 22 is fixed in the recess 21, the pattern wirings 27a, 27b, 27c and the sensor chip 22 are connected via the lead terminals 23a, 23b, 23c. Resin sealant
And 26 are sequentially filled.

The sensing element 22 may be a semiconductor magnetoresistive element or a ferromagnetic magnetoresistive element. The thickness of the printed circuit board 20 and the depth of the recess 21 can be changed according to conditions such as the thickness of the element. The material of the printed circuit board is not limited, but a material excellent in thermal expansion coefficient and moisture resistance is preferable.

Alternatively, a double-sided copper foil plate may be used as a printed board, and lands for connection to an external circuit may be formed on the back surface through holes.

The planar shape of the recess 21 does not have to be circular as in the second embodiment, and may be a shape close to an ellipse as in the first embodiment.

The shape of the sensor chip 22 can be variously changed according to the shape of the recess, and the corners may be chamfered into a curved surface so as to make surface contact with the wall surface of the recess.

Further, as shown in FIG. 6, by mounting a temperature compensating thermistor 40 in the vicinity of the sensing portion, the current flowing into the sensing portion element is increased or decreased in response to a change in the ambient temperature due to the temperature compensation effect of the thermistor 40. By changing the characteristics, it is possible to prevent a characteristic change due to the temperature of the sensing element.

FIGS. 7 (a) and 7 (b) show a modified example of the concave shape. If a shape capable of properly locking the chip 22 is formed as the upper concave portion 21a, it is formed below the concave portion. It does not matter whether the shape of the lower recess 21b is mortar-shaped or not. In short, as long as the drill portion for forming the upper recess 21a has an accurate shape, the lower recess
The shape of the drill portion for forming 21b may be any shape (as long as it is narrower than the lower recess).

FIG. 7 (a) shows a step (tip locking step) 21c provided at the boundary between the upper recess 21a and the lower recess 21b to make the lower recess into a mortar-shaped space. The lower recess is a rectangular space.

The lower recess 21b is preferably empty, but may be filled with a filler that has fluidity and solidifies after filling, as long as the positioning accuracy of the chip 22 is not impaired.

(Effects of the Invention) As described above, according to the magnetic sensor of the present invention, the overall thickness can be reduced, the moisture resistance can be improved, and the positional accuracy of the sensing element can be improved. Since the processing step is easy, it is advantageous in terms of cost.

Further, according to the second embodiment, it is possible to improve the positional accuracy of the sensing element while simplifying the processing of the recess, and further improve the reliability of the magnetic sensor.

[Brief description of the drawings]

1 (a) and 1 (b) are a plan view and an AA sectional view showing an embodiment of a magnetic sensor of the present invention, and FIGS. 2 (a) and 2 (b).
3 (a) and 3 (c) are a plan view, a side view, and a perspective view showing the configuration of a conventional magnetic sensor, and FIGS. 3 (a) and 3 (b) are cross-sectional views showing a moisture-resistant structure of the conventional magnetic sensor, respectively. a) and (b) are plan views and sectional views showing the configuration of a second embodiment of the present invention, and FIGS. 5 (a) and (b) are partially enlarged views and plan views of the second embodiment. FIG. 6 is an explanatory view of a modified embodiment, and FIGS. 7A and 7B are explanatory views of a modified example of the present invention. 20 printed circuit board, 21 recess 21a recess body, 21b mortar section 22 magnetic sensor chip (sensing element) 23a, 23b, 23c lead terminal 25 moisture resistant, 26 …… Sealant 27a, 27b, 27c …… Pattern wiring 28 …… Solder part, 30 …… Through hole 40 …… Thermistor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Bibliography Showa 57-97284 (JP, U) Showa 52-157729 (JP, U)

Claims (2)

(57) [Claims] 1. A magnetic sensor using a sensing element having a magnetoresistive effect, wherein the sensing element is positioned in a recess formed on a printed circuit board having a pattern wiring on an upper surface. A lead terminal disposed in close contact with the pattern wiring on the upper surface of the printed board to the inner wall of the recess, connected to the outside via a lead terminal, and furthermore, the sensing element in the recess has a moisture-resistant filling. The recess is continuously formed downward from the lower end of the recess main body having a predetermined depth and a predetermined diameter in which the sensing element can be fitted. A magnetic sensor comprising: a mortar-shaped mortar portion. 2. A temperature compensation thermistor is mounted on the upper surface of the printed circuit board and connected to a sensing element, so that a current flowing into the sensing element is increased or decreased according to a change in ambient temperature. 2. The magnetic sensor according to claim 1, wherein characteristics of the sensing element are prevented from fluctuating due to temperature.