JP2627279B2 - Magnetoresistive element assembly - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is mainly used for a facsimile, a telephone line input current detecting element such as a telephone, a current detecting element of various electric circuits, or a position detecting element. The present invention relates to a magnetoresistive element assembly using a ferromagnetic thin film element.

[Prior Art] FIG. 9 is an external perspective view of a conventional magnetoresistive element.
FIG. 10 is a configuration diagram of the fine pattern, and FIG. 11 is an equivalent circuit diagram thereof. Reference numeral 11 denotes the entire magnetoresistive element, and its structure is such that a fine pattern portion 112 is formed on a substrate 71 (silicon or alumina substrate) by vapor deposition or sputtering. 31,32,33,34 appear, 34,32
The output voltage is taken out more. On the other hand, a bias magnet 81 is adhered to the back side of the magnetoresistive element 11 .

The configuration of the fine pattern 112 is as shown in FIG.
Folded magnetoresistive element elements 102 and 103 are arranged close to each other, and thin-film yokes 105 and 106 are arranged outside thereof. On the other hand, elements 101 and 104 are arranged mutually and are arranged with a step difference from 102 and 103. element
102, 103 and 101, 104 are as shown in the equivalent circuit of FIG.
This corresponds to the combination of opposing sides in the bridge circuit configuration.

FIG. 12 shows a conventional application example for current detection. 9
Is a head (permalloy material), and its air gap portion is arranged so as to sandwich the elements 102 and 103 of the fine pattern.

 Fig. 13 shows that current and voltage are applied between terminals,
Output voltage V (Terminal side is +).
Output voltage V It is a characteristic example of the primary current I.
Focusing on the characteristics at room temperature of 25 ° C, the magnetic field of the bias MG81 is
The elements 102, 103 join at right angles to the length of the
In the negative and positive directions of the current,
Thus, a substantially linear characteristic is obtained.

Here, when setting the corresponding to the current to be detected, for example, a threshold voltage V _A and V _B (set at subsequent processing circuit.) At the negative current -I ₁ corresponds, and positive current + I
₁ can be detected.

[Problems to be solved by the invention]

Here, the conventional problem is that the offset voltage V _off itself varies within a lot in FIG. 13 and the offset voltage V _off itself has temperature characteristics in FIG. In this case, the temperature rises to 0 ° C., 25 ° C., and 60 ° C., but the entire characteristic tends to shift upward. Therefore, there is a problem that the detected current value largely fluctuates due to temperature fluctuations within the lot with respect to a preset threshold voltage.

The causes of the offset voltage variations and temperature fluctuations are considered to be mainly caused by variations in the elements 101, 102, 103, and 104 themselves and loss of resistance balance of the bridge circuit due to non-uniform thermal distortion. The lot in which the offset voltage shows a rising tendency with respect to the rising, or a lot in which the offset voltage shows a falling trend like a dotted line.

Conventionally, as a method of correcting the temperature fluctuation of the offset voltage, a method such as adding an element such as an NTC thermistor to the subsequent amplifier circuit and performing correction by the latter amplifier circuit as shown in FIG. 15 has been adopted. For example, even if the actual magnetoresistive element and the amplifying circuit are in, for example, a one-piece case, a slight temperature difference occurs between them, and due to this effect, accurate offset voltage temperature correction cannot be performed. When the resistance element and the amplifier circuit are installed at a distance from each other, a large temperature difference causes an effect, so that an error due to the temperature characteristic of the current measurement cannot be completely corrected.

[Object of the invention]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a magnetoresistive element assembly capable of performing temperature characteristic correction of an offset voltage in a range of a sensor portion before an amplifier circuit and improving the accuracy of the correction more than the conventional method.

[Configuration of the invention]

According to the present invention, a resin-molded magnetoresistive element composed of a magnetoresistive element composed of a ferromagnetic thin film element and a thin film yoke is electrically connected to an external substrate on which a thick film resistive element is printed. The pattern configuration of the magnetoresistive element is such that four magnetoresistive element elements bridge-connected to each other, one of the two opposing elements are close to each other, and thin-film yokes are arranged on both sides thereof. The other two opposing elements are separated from each other on both sides of the thin film.

The thick-film resistance element printed on the external substrate is electrically arranged so that at least mutually separated magneto-resistance elements in the pattern of the magneto-resistance element are included in a parallel circuit, and is externally provided. The resistance value can be adjusted for trimming.

Further, the thick-film resistance element has a negative temperature coefficient of resistance NT.
It is also possible to use a C thermistor or a PTC thermistor having a positive temperature coefficient of resistance.

〔Example〕

FIG. 1 shows an external view of a magnetoresistive element assembly according to the present invention. The magnetoresistive element 1 has a bias magnet 8 adhered to its lower side, and is electrically connected to the substrate 5 on which the wiring pattern is printed.

The configuration of the fine pattern portion of the magnetoresistive element 1 is the tenth
As shown in the figure, the magnetoresistive element elements 101, 102, 103, and 104, which are bridge-connected to each other, have opposing combinations 102 and 103 on the sides of the bridge, respectively.
101,104 are separated. The yokes 105 and 106 are located on both sides of the magnetoresistive element elements 102 and 103 and have a function of efficiently applying an applied magnetic field to the elements 102 and 103.

 Here, 102 and 103 have the role of receiving an external magnetic field, while 1
01 and 104 are fixed against the bridge circuit without receiving an external magnetic field.
It acts as a constant resistance. FIG. 3 shows the magnetoresistive element 1
An equivalent circuit is shown. Fine pattern is formed on substrate 7
To the external terminal 3 via the bonding wire 311
It is electrically connected. Terminal is the power input terminal,
Is an output terminal, and R_Two
And R_ThreeChanges in the direction in which the resistance decreases, the output power
V (The terminal is on the + side) tends to change in the positive direction
Is shown.

Insertion on the substrate 4 of the magnetic resistance element 1 in the example of FIG. 1 are printed (initial value R ₅₀ of the resistance value) wiring pattern and thick film resistance element 5, the thick-film resistor element 5 is in parallel to the terminal It is, as shown in an equivalent circuit of the magnetoresistive element assembly of FIG. 2, are connected in parallel to a fixed resistor R ₄ on the pattern of the magnetoresistive element 1.

The substrate 4 has connection terminals 61, 62, 63, 64 to the outside.

FIG. 4 shows the case where the thick film resistance element 5 is added. When (Between terminals 64 and 63) FIG. 5 is a diagram showing a tendency of change of the data.

The resistance ratio R ₅₀ / R ₄ is 5 or less is suitable as the intended use as a rapid offset adjustment have reduced V _{4'3 'in} response to changes in R _50, generally R ₅₀ / R It is desirable to adjust R ₅₀ by setting R ₅₀ in a range where ₄ is 5 or more.

With the characteristic curve of FIG. Interval (voltage before not connected to R ₅₀₎ is _{V 4'3 'fluctuation} width of ΔV and is on the other hand _{V 2'3'} (voltage between the terminals 61 and 62)
Is fixed, the variation width ΔV _off of the offset voltage V _{off4′2 ′} is equal to the above-mentioned variation ΔV and has a relationship of ΔV _off = ΔV.

FIG. 5 shows that the offset voltage V _{off4′2 ′ is} applied to the thick film resistor 5.
Adding cuts 51 by laser trimming or sand blasting, while monitoring an example of adjusting the resistance value until a predetermined offset voltage value V _0.

The method shown in FIG. 5 makes it possible to adjust the offset voltage to a standard value at room temperature, which is a measure for improving the offset voltage variation of the magnetoresistive element itself, which has been a problem in the past.

FIG. 6 shows another embodiment according to the present invention, in which an NTC thermistor 5 ″ (see FIG. 6 (b)) having a negative temperature coefficient of resistance is used for the thick film resistor for adjustment.

In this case, when the original offset voltage of the magnetoresistive element 1 has a positive temperature coefficient, it is effective for temperature characteristic correction of the offset voltage.

As shown in FIG. 6 (c), the temperature characteristics of the offset voltage can be kept flat compared to the case of the adjusting resistor 5 'in which the temperature coefficient becomes almost zero.

If the offset voltage of the original magnetoresistive element 1 has a negative temperature coefficient, the correction resistor 5 ″ may be a thick-film resistive element made of a PTC thermistor material having a positive resistance temperature gradient. Good.

FIG. 7 shows still another embodiment of the present invention, and FIG. 8 shows an equivalent circuit thereof. The element 101 of the magnetoresistive element 1 ,
(Adjustment thick film resistance element 5) is inserted in parallel with (resistance value R ₁ ).

Almost the same effects as in the embodiment of FIG. 1 can be obtained.
However, the direction of the change in the resistance value of the thick film resistor 5 and the direction of the change in the offset voltage _{off4 "2"} have the effects just opposite to those in FIGS. 1, 5, and 7, but in practical use. There is no problem with the use of.

〔The invention's effect〕

As described above, according to the present invention, it is possible to improve the variation of the offset voltage of the conventional magnetoresistive element and the temperature characteristic of the offset voltage at a stage preceding the processing amplifier circuit, and it is possible to provide a magnetoresistive element assembly with high detection accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing an embodiment according to the present invention, FIG. 2 is an equivalent circuit thereof, FIG. 3 is an equivalent circuit diagram of a single magnetoresistive element, and FIG. , FIG. 5, FIG. 6, and FIG. 7 are other embodiments according to the present invention. FIG. 8 is an equivalent circuit of FIG. 7, FIG. 10 shows the fine pattern diagram, FIG. 11 shows its equivalent circuit, FIG. 12 shows a conventional application example, FIGS. 13 and 14 show conventional characteristic diagrams, and FIG. 15 shows a conventional countermeasure example. 1 , 11 ... magnetoresistive element, 12 , 112 ... fine pattern part, 2, 21 ... resin mold, 31, 32, 33, 34 ... terminal, 31
1 ... bonding clear, 4 ... circuit board, 5,5 ', 5 ",
5 ... Thickness resistor, 51,52,53,54 ... Cut for resistance value adjustment, 61,62,63,64 ... Lead terminal, 8,81 ... Bias M
g, 7,71 …… the substrate inside the magnetoresistive element, 9 …… the head.

Claims (3)

(57) [Claims] 1. A magnetoresistive element comprising a ferromagnetic thin film element and a thin film yoke, and a resin-molded magnetoresistive element is electrically connected to an external substrate on which a thick film resistive element is printed. And the pattern configuration of the magneto-resistive elements is such that four magneto-resistive element elements bridge-connected to each other are arranged in pairs of two, one pair being close to each other. A magnetoresistive element assembly, wherein a thin film yoke is disposed on both sides of the one pair, and the other pair is separated from a region of the thin film yoke. 2. A thick-film resistive element printed on said external substrate, wherein said thick-film resistive element is at least one of said other pair of magneto-resistive element elements spaced out of said thin-film yoke area. 2. The thick-film resistance element which is electrically connected to form a parallel resistance circuit together with the magneto-resistance element, wherein the resistance of the thick-film resistance element can be further adjusted by external trimming. Item 7. The magnetoresistive element assembly according to Item 1. 3. The thick-film resistance element is an NTC thermistor having a negative temperature coefficient of resistance or a PTC having a positive temperature coefficient of resistance.
2. The magnetoresistive element assembly according to claim 1, which is a thermistor.