JP2012229950A - Current sensor and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve sensitivity of a current sensor while saving work and reducing costs in manufacturing the current sensor.SOLUTION: A current sensor is mainly manufactured by first forming a lead frame with an island part 12, a primary conductor 13, and sensor lead terminals 14 embossed on the same flat plate, then cutting off electrical connection between the primary conductor 13 and the island part 12, and finally forming a U-shaped part 31 having an almost U shape that surrounds an island body 21, of the island part, having almost the same shape as an IC chip 11 rectangular in a plain view. The IC chip 11 is stuck to the island body 21, and the IC chip 11 and the sensor lead terminals 14 are connected by bonding wires 15. In this step, one or more magnetic field conversion devices 41 are disposed on virtual chamfer curves of corner parts of the IC chip 11a and 11b as opposed to corner parts of the U-shaped part 31. The total of detection signals from each magnetic field conversion device 41 are calculated and outputted as the output signal of the current sensor 10.

Description

  The present invention relates to a current sensor for measuring a current value of a current flowing through a conductor and a method for manufacturing the current sensor.

Conventionally, as a current sensor for measuring a current flowing through a conductor, a method of detecting a magnetic field generated around a conductor through which a measurement current flows is known.
For example, in order to obtain the sensitivity of a current sensor, a method of arranging a magnetic field conversion element in the vicinity of a primary conductor through which a measurement current flows, or a method of concentrating magnetic flux using a magnetic material and arranging a magnetic field conversion element in the vicinity thereof, For example, using a LOC (lead on chip) technique, a device in which a magnetic field conversion element is arranged in the vicinity immediately below the edge of the primary conductor has been proposed (see, for example, Patent Document 1).

  In addition, for example, the primary conductor is formed in a U-shape, and the Hall element is placed in the conductor portion so that the Hall element as the magnetic field conversion element is directly above the position where the maximum magnetic flux density near the U-shaped center point is given. Further, the primary conductor has a T-shaped cross section or a rectangular cross section with a minimum dimension smaller than the thickness of the lead frame, or the primary conductor is used in combination with a magnetic flux concentration layer in addition to the primary conductor. There has also been proposed one formed such that the magnetic flux density is more concentrated above the conductor surface (see, for example, Patent Document 2 and Patent Document 3).

International Publication No. 99/14605 Pamphlet International Publication No. 2005/026749 Pamphlet International Publication No. 2006/130393 Pamphlet

  However, as in the above-mentioned Patent Document 2 and Patent Document 3, in the method of providing the Hall element so as to be directly above the center point of the U-shaped primary conductor, the sensitivity fluctuation due to the maximum sensitivity and the positional deviation. In order to minimize it, it is the most suitable form to arrange one Hall element at the center point where the magnetic flux is most concentrated. Further, even if a plurality of U-shapes are formed, there are at most two places in terms of mounting on the package, and it is difficult to have many U-shapes.

  Further, in Patent Document 2 and Patent Document 3 described above, in order to improve the sensitivity, when the Hall element is arranged immediately above the center point of the U shape corresponding to the magnetic field center position of the U-shaped primary conductor, By arranging the element close to the U-shaped primary conductor, the observed magnetic flux density is increased to increase the magnetic field sensitivity, that is, the current sensitivity. Therefore, it is necessary to perform a process of attaching the chip by flip chip bonding so that the IC chip is turned over and the Hall element is close to the primary conductor.

  For this purpose, an insulating layer is disposed between the primary conductor and the IC chip (including the Hall element), and the chip electrical terminal and the package lead terminal are bump-connected. While adjusting the bump thickness, the height position is adjusted so that the insulating part and the bump connection part are at the same surface position, thereby stabilizing the bump connection process. In this way, although it is for improving sensitivity, it is necessary to perform bump connection processing in a state where the height is balanced with the horizontal position as described above, and the balance between manufacturing effort, manufacturing accuracy and cost is required. Was not good.

Further, as in the above-mentioned Patent Document 1, in the case where sensitivity is improved by arranging a magnetic field conversion element near the primary conductor edge using the LOC technique, normal IC packaging processing is performed. In addition, the formation process of the insulating layer is essential.
As described above, although any method can improve sensitivity, it is not sufficient from the viewpoint of simplicity of production, and a method capable of improving sensitivity by a simple method has been desired.
The present invention has been made paying attention to the above-mentioned conventional unsolved problems, and is intended to reduce the labor and cost in manufacturing, and to provide a current sensor capable of improving sensitivity and a method of manufacturing the current sensor. It is intended to provide.

  As a result of extensive research, the present inventor has noticed that the magnetic field distribution in the vicinity of the primary conductor having a finite shape and a finite dimension does not change so much numerically in the vicinity of the dimension area of the same level as the primary conductor. It was made. The primary conductor and the magnetic field conversion element are arranged so as to surround the IC chip including the magnetic field conversion element by the primary conductor in a positional relationship in the same plane or substantially in the same plane within the step range of the thickness of the primary conductor. And, by arranging one or more magnetic field conversion elements around the corner portion of the primary conductor, and arranging one or more corner portions of the primary conductor where the magnetic field conversion element is arranged in such a positional relationship, It has been found that sufficient magnetic sensitivity can be obtained.

  That is, a current sensor according to claim 1 of the present invention includes a primary conductor through which a measurement current flows, a magnetic field conversion element that detects a magnetic flux induced from the measurement current, and a rectangular IC chip in plan view, and the IC A current sensor comprising: an island portion on which a chip is placed; a lead terminal; and a lead frame in which the primary conductor is integrally formed, wherein the primary conductor is electrically insulated from the island portion. In a plan view, at least one corner portion having a shape extending from the outside at one corner and two right and left sides of the IC chip is provided, and the magnetic field conversion element includes the corner portion of the IC chip. It is arrange | positioned at the corner | angular part located inside.

A current sensor according to a second aspect includes a plurality of the magnetic field conversion elements.
The current sensor according to claim 3 is characterized in that the plurality of magnetic field conversion elements are arranged along a chamfer curve virtually drawn at the corner of the IC chip.
The current sensor according to claim 4 is characterized in that the virtually drawn chamfer curve is a curve along an equal magnetic flux density line formed by a magnetic flux induced in the primary conductor by the measurement current. .
The current sensor according to claim 5 is characterized in that the island portion is down-pressed so that a vertical position is lower than the primary conductor.
The current sensor according to claim 6 is characterized in that the magnetic field conversion element is a silicon Hall element.

  A current sensor manufacturing method according to claim 7 includes: a primary conductor through which a measurement current flows; and an IC chip having a magnetic field conversion element for detecting a magnetic flux induced from the measurement current and having a square shape in plan view. A method for manufacturing a sensor, comprising: an island portion having an island body having a shape equivalent to that of the IC chip; a primary conductor and a lead terminal electrically separated from the island portion; and the primary conductor is a plan view. Placing the IC chip on the island body of the lead frame having at least one corner portion that is shaped from the outside at one corner of the island body and two left and right sides thereof. Electrically connecting the IC chip placed on the island body and the lead terminal, the island portion and the IC chip Characterized in that it and a step of packaging with integrally molded with said lead terminals and said primary conductor.

According to an eighth aspect of the present invention, there is provided a current sensor manufacturing method including a plurality of the magnetic field conversion elements.
The current sensor manufacturing method according to claim 9 is characterized in that the plurality of magnetic field conversion elements are arranged along a chamfered curve virtually drawn at the corner of the IC chip.
In the method of manufacturing a current sensor according to claim 10, the virtually drawn chamfer curve is a curve along an equal magnetic flux density line formed by a magnetic flux induced in the primary conductor by the measurement current. Features.

  According to the present invention, an island portion having a magnetic field conversion element for detecting a magnetic flux induced from a measurement current and having an IC chip having a rectangular shape in plan view, a lead terminal, and a primary conductor are connected to one lead. A corner portion formed from a frame, and further, the primary conductor is electrically separated from the island portion, and in a plan view, the corner portion has a shape extending from the outside to one corner of the IC chip and two left and right sides thereof. Since the magnetic field conversion element is arranged at the corner portion located inside the corner portion of the IC chip, normal packaging is not required without requiring flip chip technology or bump connection. A current sensor can be produced using the technology, and magnetic sensitivity can be ensured. Therefore, it is possible to reduce manufacturing effort and cost, and to improve sensitivity.

It is an example of the lead frame applied to the current sensor of the present invention. It is an example of a current sensor in which an IC chip is mounted on a lead frame. It is explanatory drawing for demonstrating the positional relationship of an IC chip and a conductor main body. It is a block diagram which shows the structure of IC chip. It is a figure which shows the manufacturing process of the current sensor of this invention. It is a block diagram which shows the other structure of an IC chip. (A) is explanatory drawing of the parameter showing the positional relationship of a magnetic field conversion element (observation point) and a primary conductor, (b) is projecting the triaxial resultant force of the magnetic flux density formed in space on the X-axis-Z-axis plane. It is the schematic which shows an example of magnetic flux density distribution. It is a figure which shows an example which represented the magnetic flux density intensity of the Z-axis direction in the X-axis-Y-axis plane with the contour line. (A) is an example of a magnetic field simulation result representing the magnetic flux density strength in the Z-axis direction on the X-axis-Z axis plane, and (b) is a magnetic field simulation representing the magnetic flux density strength in the Z-axis direction on the Y-axis-Z axis plane. It is an example of a result. (A) is an example of a magnetic field simulation result representing the magnetic flux density strength in the Z-axis direction on the X-axis-Z axis plane, and (b) is a magnetic field simulation representing the magnetic flux density strength in the Z-axis direction on the Y-axis-Z axis plane. It is an example of a result. It is an example of the current sensor which expanded the width about a part of primary conductor.

Hereinafter, an embodiment of the present invention will be described. The slits and dimples are not shown in the figure.
FIG. 1 shows an example of a lead frame applied to the current sensor of the present invention. It is an example which shows a part of lead frame 1 which formed a plurality of current sensors, and shows the state where the below-mentioned IC chip is not carried about one current sensor. FIG. 2 shows a state in which an IC chip is mounted on the lead frame 1 of FIG.

  As shown in FIGS. 1 and 2, a current sensor 10 according to the present invention includes an IC chip 11 that includes a magnetic field conversion element and has a square shape in plan view, an island portion 12 on which the IC chip 11 is placed, and a measurement current flows. The primary conductor 13 and each terminal of the IC chip 11 are connected via PADs 44a and 44b, and are composed of sensor lead terminals 14 for inputting / outputting signals from the outside. It is stored in. The package 5 is formed of a small IC package such as SOP (Small Outline Package) or SSOP (Shrink SOP).

As shown in FIG. 1, the island portion 12, the primary conductor 13, and the sensor lead terminal 14 are formed from the same lead frame 1 and are disposed so as to surround the island portion 12 with the primary conductor 13 and the sensor lead terminal 14. The
As shown in FIG. 1 and FIG. 2, the island portion 12 has a substantially alphabetic T-shape, and is composed of an island body 21 and a terminal portion 22 that are substantially the same in plan view as the IC chip 11. One end of the island body 21 is vertically connected to one side of the island body 21, and the other end of the terminal portion 22 is divided into two to form a lead terminal.

The primary conductor 13 is formed of a substantially Katakana U-shaped portion 31 and terminal portions 32 and 33, and the terminal portion 32 and the terminal portion 33 have a symmetrical shape and sandwich the island portion 12. Are arranged at symmetrical positions.
The U-shaped portion 31 is formed in a substantially Katakana U-shape along the three sides of the island body 21 having a rectangular shape in plan view, excluding the side to which the terminal portion 22 is joined, and the island body. 21 and three substantially linear portions of the U-shaped portion 31 are formed with a constant gap distance m1.

  The terminal portion 32 is formed in a substantially rectangular shape, and one of the long sides is joined to one end of the U-shaped portion 31. At this time, one of the long sides of the terminal portion 32 is connected to the U-shaped portion 31, but is joined at a position slightly inside the end portion of the long side. Further, the terminal portion 32 is arranged so that a part of the long side of the terminal portion 32 is along a part of the side of the island body 21 joined to the terminal portion 22 and with the constant gap distance m1. Furthermore, the gap is arranged between the long side of the terminal portion 22 and the short side of the terminal portion 32 with a constant gap distance m2.

A plurality of lead terminal forming holes 34 for forming lead terminals are formed along the longitudinal direction on the long side opposite to the side connected to the U-shaped portion 31 of the terminal portion 32. The package 5 is formed by molding up to the lead terminal forming hole 34, and the lead terminal forming hole 34 outside the package 5 forms the lead terminal of the terminal portion 32.
The terminal part 33 has a symmetrical shape with the terminal part 32 as described above, and is arranged at a symmetrical position. As a result, as shown in FIG. 2, the primary conductor 13 surrounds the three sides of the island body 21 of the island portion 12 with a U-shaped portion 31 and surrounds the remaining one side with terminal portions 32 and 33. Placed in.

Further, at this time, the U-shaped portion 31 and the island body 21 and the terminal portions 32 and 33 and the island body 21 are arranged with a certain gap distance m1, and the terminal portion 22 and the terminal portion 32. And 33 are disposed with a constant air gap distance m2, so that the island portion 12 and the primary conductor 13 are physically and electrically separated.
A mold resin may enter between the island portion 12 and the primary conductor 13 by the molding.

  A plurality of sensor lead terminals 14 are arranged so as to surround the U-shaped portion 31. For example, in FIG. 2, one end of the sensor lead terminal 14 is disposed so as to surround the U-shaped portion 31, and the other end of the sensor lead terminal 14 is formed with lead terminals of the terminal portions 32 and 33 of the package 5. It is arranged along the longitudinal direction of the long side opposite to the opposite side, and is formed so as to protrude from the package 5.

  Then, in a state where the IC chip 11 is placed on the island body 21 of the island part 12, the support part 5a, the sensor lead terminal 14, and the end parts of the terminal parts 22, 32, 33 are left to be molded, thereby forming a package. A plurality of sensor lead terminals 14 are formed on one of the long sides of 5, and a lead terminal for the primary conductor 13 and a lead terminal for the island portion 12 are formed on the other side. Note that the lead terminal for the island portion 12 is housed in the package 5 and may be connected inside the package 5.

Further, the positional relationship between the IC chip 11 and the U-shaped portion 31 of the primary conductor 13 is such that the IC chip 11 has a thickness of the island body 21 with respect to the U-shaped portion 31 as shown in FIG. It is located at a considerable distance and is arranged with a certain gap distance m1 in the center between two substantially straight opposite sides forming a substantially U-shaped portion of the U-shaped portion 31. .
3A and later-described (b) schematically show the AA 'cross section of FIG.

  In FIG. 3A, the case where the IC chip 11 and the U-shaped portion 31 of the primary conductor 13 are arranged so as to be located on the same plane has been described. However, the present invention is not limited to this, and is shown in FIG. As described above, the island body 21 may be subjected to a down-press process that works to improve the magnetic sensitivity. At this time, if the vertical position of the magnetic field conversion element included in the IC chip 11 is down-pressed so as to be equal to the vertical position of the conductor center (corresponding to the center in the thickness direction) of the U-shaped portion 31 of the primary conductor 13, The induced magnetic flux induced in the primary conductor 13 can be detected more efficiently. FIG. 3B shows that when the magnetic field conversion element is near the upper surface of the IC chip 11, the magnetic field conversion element is positioned at the center in the thickness direction of the U-shaped portion 31 in order to obtain the maximum magnetic flux density strength. The state where the height positions of the magnetic field conversion elements are aligned is shown.

As shown in FIG. 4, for example, the IC chip 11 includes magnetic field conversion elements 41a and 41b, adders 42a and 42b, a signal processor 43, and PADs 44a and 44b.
The magnetic field conversion elements 41a and 41b are formed of the same sensor capable of detecting a magnetic field such as a silicon Hall element, and three magnetic field conversion elements 41a and 41b are provided, for example.

The adder 42 a is an adder for the magnetic field conversion element 41 a, adds the detection signals of the three magnetic field conversion elements 41 a, and outputs the addition result to the signal processor 43. The adder 42b is an adder for the magnetic field conversion element 41b, adds the detection signals of the three magnetic field conversion elements 41b, and outputs the addition result to the signal processor 43.
The signal processor 43 adds up the addition results from the adders 42a and 42b and amplifies them. In addition, other necessary predetermined signal processing is performed.

For example, three PADs 44a and 44b are provided. The PADs 44a and 44b are connected to the signal processor 43 by internal wiring (not shown).
As shown in FIG. 2, when the corners sandwiching one long side of the IC chip 11 having a square shape in plan view are 11a and 11b, the corners 11a and 11b of the IC chip 11 are substantially in the shape of a U-shape. The U-shaped portion 31 is placed on the island body 21 so as to face the two corner portions 31a and 31b.

As shown in FIG. 2, the magnetic field conversion elements 41 a and 41 b are provided at the corners 11 a and 11 b of the IC chip 11. Specifically, the magnetic field conversion elements 41a and 41b are arranged along a chamfer curve virtually drawn in the corner portions 11a and 11b.
That is, as described above, the IC chip 11 is placed on the island body 21 so that the corners 11a and 11b are opposed to the corners 31a and 31b of the U-shaped part 31, so that the magnetic field conversion element 41a, 41b is arrange | positioned along a chamfering curve so that the corner parts 31a and 31b of the U-shaped part 31 may be opposed.

In FIG. 2, for example, the magnetic field conversion elements 41 a and 41 b are arranged along the chamfer curve over the entire surfaces of the corner portions 11 a and 11 b (not necessarily the magnetic field conversion elements 41 a and 41 b over the entire surface of the corner portions 11 a and 11 b. 41b need not be provided, and may be locally disposed as long as it is disposed on a chamfered curve.
In FIG. 2, for example, the PADs 44 a and 44 b are disposed along the short sides of the IC chip 11, and are disposed at positions near the terminal portions 32 and 33 away from the magnetic field conversion elements 41 a and 41 b (not necessarily). , It does not have to be arranged near the terminal portions 32 and 33).

In FIG. 2, for example, the signal processor 43 includes a PAD 44 a that is closer to the center in the left-right direction along the long side of the IC chip 11 and slightly lower than the center in the up-down direction along the short side. , 44b is located in the vicinity of the position (it is not necessarily arranged at this position).
In FIG. 2, for example, the adder 42 a is disposed near the signal processor 43 between each magnetic field conversion element 41 a and the signal processor 43, and the adder 42 b includes each magnetic field conversion element 41 b and the signal processor. It is arrange | positioned in the location near the signal processor 43 between 43 (it does not necessarily need to be arrange | positioned in this position).

  With the above configuration, the induced magnetic flux generated in the corner portions 31 a and 31 b according to the measurement current flowing through the primary conductor 13 is detected by the magnetic field conversion elements 41 a and 41 b constituting the IC chip 11. Then, signals corresponding to the induced magnetic flux detected by the magnetic field conversion elements 41a and 41b are added by the adders 42a and 42b, and necessary signal processing such as amplification is performed by the signal processor 43, and according to the measurement current. The sensor output is transmitted to the PADs 44a and 44b through internal wiring (not shown), and is output to the outside through the bonding wire 45 and the sensor lead terminal 14 from there.

Next, a method for manufacturing the current sensor 10 will be described with reference to FIG.
FIG. 5 shows a part corresponding to one current sensor by taking out a part of the lead frame 1.
First, as shown in FIG. 5A, the island portion 12, the primary conductor 13, the sensor lead terminal 14, and the support portion 5a are driven out of the same plate material in the region corresponding to the current sensor 10, and the lead frame 1 is attached. Form.

Next, as shown in FIG. 5B, the IC chip 11 is placed on the island portion 12.
Further, as shown in FIG. 5C, the PADs 44 a and 44 b of the IC chip 11 and the sensor lead terminal 14 are connected by a bonding wire 45.
Finally, the IC chip 11, the island portion 12, the primary conductor 13, and the sensor lead terminal 14 are integrally molded to form the package 5. Thereby, the current sensor 10 is formed.

Then, the current sensor 10 formed on the lead frame 1 is cut from the lead frame 1 and a lead terminal is formed, thereby forming a package in a small IC package such as SOP or SSOP as shown in FIG. A current sensor can be obtained.
Here, as described above, the primary conductor 13 shown in FIG. 2 is arranged so as to surround the IC chip 11 in the lead frame plane. Therefore, the primary conductor 13 has corner portions 31a and 31b. In the IC chip 11, the magnetic field conversion elements 41a and 41b face the corner portions 31a and 31b and are virtually drawn on the corner portions 11a and 11b of the IC chip 11. Is placed on the chamfer curve.

Here, as shown in FIG. 2, for example, when the corner portions 31a and 31b of the primary conductor 13 are bent in an L-shape of the alphabet, the equal magnetic flux density lines around the corner portions 31a and 31b are shown in FIG. As shown in FIG.
Therefore, in the IC chip 11, for example, as shown in FIG. 2, a plurality of magnetic field conversion elements 41 are arranged along the arc-shaped equal magnetic flux density lines, and detection signals output from the plurality of magnetic field conversion elements 41 are output. Can be summed by the adder 42, and the sum can be obtained as a sensor output to improve the sensitivity.

  As shown in FIG. 5, in the manufacturing process of the current sensor 10, the IC chip 11 is placed on the island body 21 of the island portion 12, and the PADs 44a and 44b of the IC chip 11 and the sensor lead terminal 14 are bonded to the bonding wire. All that is required is to connect at 45 and mold. That is, the IC chip 11 does not need to be flip chip bonded or bump-connected, and it is not necessary to provide an insulating film. Further, in order to obtain a desired magnetic field sensitivity (that is, current sensitivity), it can be realized by providing a plurality of magnetic field conversion elements 41 as required.

Therefore, it is possible to improve the sensitivity of the current sensor 10 while reducing manufacturing effort and cost.
As described above, the case where the magnetic field conversion elements 41 are arranged at the corner portions 11a and 11b in a line along the chamfer curve has been described with reference to FIG.
Arranging a plurality of magnetic field conversion elements 41 along the equal magnetic flux density line means that a signal obtained by adding a plurality of magnetic field conversion element outputs having the same signal level, the same noise level, and the same SN ratio. Since it is obtained as a sensor output, the total sensitivity is also effective since there is no deterioration in the SN ratio (less) and high magnetic sensitivity can be obtained.

  In addition to the case where the magnetic field conversion elements 41 are arranged in a line along the equal magnetic flux density line, it is possible to arrange a plurality of magnetic field conversion elements so as to obliquely cross the equal magnetic flux density line. It is also possible to arrange the lines so as to cross the lines vertically. Further, the magnetic field conversion elements are not limited to being arranged in a single row, but may be arranged in parallel in several rows or in a planar shape. Further, the plurality of magnetic field conversion elements 41 may be densely arranged, or may be sparsely arranged. Furthermore, the magnetic field conversion element 41 may be locally disposed on a virtual chamfer curve or an equal magnetic flux density line, or may be disposed over the entire surface.

  When multiple Hall elements are arranged on the same magnetic flux density line, the magnetic flux density increases in one Hall element on one end, and the magnetic flux density decreases in the Hall element on the opposite end. Since the sensor output obtained by adding the outputs works in a direction in which the fluctuation is canceled out in total, it works in a direction that becomes stronger against the sensitivity change due to the assembly variation in manufacturing.

  In the above embodiment, as shown in FIGS. 2 and 4, the case where the IC chip 11 is configured including the plurality of magnetic field conversion elements 41 has been described, but the present invention is not limited to this. For example, as shown in FIG. 6A, it is also possible to provide one magnetic field conversion element 41 only on either the left or right corner 11a or 11b of the IC chip 11, and in this case, signal addition The detector 42 is not necessarily passed, and the detection signal of the magnetic field conversion element 41 can be output to the signal processor 43 as it is. It is also possible to provide one magnetic field conversion element 41 at each of the left and right corners 11a, 11b of the IC chip 11.

  Further, as shown in FIG. 6B, a plurality of magnetic field conversion elements 41 are provided in the left and right corners 11 a and 11 b of the IC chip 11, and detection signals of the plurality of magnetic field conversion elements 41 are obtained by one adder 42. It is also possible to amplify the addition result and perform other signal processing by the signal processor 43. Furthermore, the adder 42 can be included in the signal processor 43, and these are also within the scope of the present invention.

  Also, as shown in FIGS. 1, 2, and 5, in the above-described embodiment, the primary conductor 13 has been described as having a U-shaped portion 31 having a substantially U-shaped U-shaped portion. It is not limited to. For example, the primary conductor 13 can be formed in an L-shape of the alphabet so as to follow only one of the corner portions 11a and 11b of the IC chip 11.

In this case, the magnetic field conversion element for the corner portion 11a or 11b in the IC chip 11 so that the magnetic field conversion device 41 is arranged on the virtual chamfer curve or the equal magnetic flux density line of this one corner portion. The position 41 may be laid out and the positional relationship between the IC chip 11 and the primary conductor 13 may be determined.
In the description so far, the primary conductor 13 has at least one corner portion having a shape extending from the outside at one corner and two left and right sides of the island body 21 having the same shape as the IC chip 11 in plan view. The case of having one has been described.

  As described above, since the equal magnetic flux density lines are formed at the corner portions of the primary conductor 13, the primary conductor 13 only needs to have one or more corner portions that form the equal magnetic flux density lines. Then, the positional relationship between the primary conductor 13 and the IC chip 11 and the position of the magnetic field conversion element 41 in the IC chip 11 may be determined so that the magnetic field conversion element 41 is positioned facing the corner portion.

  Further, the angles of the corner portions 31a and 31b of the primary conductor 13 do not necessarily have to be approximately 90 °, and the number of the magnetic flux density lines that can be formed and a desired magnetic sensitivity (that is, current sensitivity) can be obtained. Any angle may be used as long as the magnetic field conversion element 41 can be arranged at the corner. Further, the shape of the primary conductor 13 is not limited to a specific shape such as an L-order shape or a U-shape.

As can be seen from the above, the current sensor according to the configuration of the present application can further improve the sensitivity and improve the SN ratio while achieving the effect of suppressing the sensitivity variation.
In FIG. 2, the IC chip 11 is placed in the package 5 so that the long side of the package 5 and the long side of the IC chip 11 correspond (or the short side of the package 5 and the short side of the IC chip 11). The area occupation rate occupied by the IC chip 11 in the package 5 is relatively high.

  The arrangement is not limited to this, and in order to further improve the sensitivity, the long side of the package 5 and the short side of the IC chip 11 (or the short side of the package 5 and the long side of the IC chip 11). You may arrange | position so that it may respond | correspond. That is, in FIG. 2, the IC chip 11 may be configured to be rotated 90 degrees. By doing in this way, since the width | variety of the U-shaped part 31 of the primary conductor 13 arrange | positioned along the IC chip 11 can be made narrower, the improvement of magnetic flux density can be aimed at by that, ie, The sensitivity can be improved.

  Further, it is assumed that the magnetic field conversion element 41 is a Hall element that occupies an area of about 30 μm square and 40 μm square including wiring, and the chip size of the IC chip 11 is assumed to be 2.7 × 1.4 mm. As shown in FIG. 2, the PAD 44 is arranged on the IC chip 11 so as to avoid the corners 11a and 11b, and passes through a position of 200 μm inward from the two sides of the IC chip 11 forming the corners 11a and 11b. It is assumed that the magnetic field conversion elements 41a and 41b are arranged in a circular arc shape at the corners 11a and 11b, and are arranged on the entire surface of the corners 11a and 11b with an angle of 90 degrees.

In this case, each of the corner portions 11a and 11b has a space for arranging about 14 to 15 magnetic field conversion elements 41a and 41b when physically arranged in one row, and the degree of freedom regarding the number and position. Is expensive.
In the current sensor 10 shown in FIG. 2, the magnetic field conversion element 41 can be disposed at a position that satisfies the following range equation.
Range formula:
Primary conductor aspect ratio A / D: 4 ≧ A / D ≧ 0
Vertical separation distance E [mm]: + 1 ≧ E ≧ −1
Horizontal separation distance C [mm]: 2 ≧ C ≧ A / 2
A, C, D, and E in the formula are parameters for specifying the element arrangement position of the magnetic field conversion element 41 and the position of an observation point described later.

The coordinate origin P, which is the position reference for the parameters, is set as follows.
That is, as shown in FIG. 1, among the three sides forming the U-shaped portion 31, the facing portions are the facing portions 31α and 31β, and the portion sandwiched between the facing portions 31α and the facing portion 31β is the intermediate portion 31γ. . And the thickness direction center of the corner part 31b on the straight line passing through the intersection of the conductor width center which is the width direction center position of the intermediate part 31γ and the conductor width center of the facing part 31β and along the thickness direction of the corner part 31b Is a coordinate origin P that serves as a position reference for the parameter. The direction along the conductor width center of the intermediate portion 31γ is taken as the X-axis direction, the direction along the conductor width center of the facing portion 31β is taken as the Y-axis direction, and the thickness direction of the U-shaped portion 31 is taken as the Z-axis direction.

In the XYZ coordinate system thus set, as shown in the schematic diagram of the AA ′ cross section of FIG. 2 shown in FIG. 7A, the X axis from the coordinate origin P to the magnetic field conversion element 41 or the observation point. The distance in the direction is defined as a horizontal distance C [mm].
A separation distance in the Z-axis direction from the coordinate origin P to the magnetic field conversion element 41 or the observation point is defined as a vertical separation distance E [mm].
The conductor width of the U-shaped portion 31 is A [mm], and the thickness of the U-shaped portion 31 is D [mm].

  Here, in Example 1 and Example 2 described later, the gap distance m1 between the IC chip side edge of the U-shaped portion 31 and the primary conductor side edge of the IC chip 11 is set to 0.100 [mm]. Assuming a case where one of the center of the magnetic sensitive surface on the equal magnetic flux density line exists at a position of 0.3 [mm] inside the IC chip 11 from the two sides forming the corners 11a and 11b of the IC chip 11. doing. In other words, it is assumed that the center of the magnetosensitive surface is located at a location that is 0.4 [mm] inside from the primary conductor 13.

  On the other hand, the gap distance m1 is set to 0.200 [mm], and the equal magnetic flux density is set at a location of 0.2 [mm] from the two sides forming the corner portions 11a and 11b of the IC chip 11 to the inside of the IC chip. Even when there is one of the magnetic sensitive surface centers on the line, the magnetic sensitive surface center is present at a location which is 0.4 [mm] inside from the primary conductor 13. Therefore, it is necessary to determine the position of the center of the magnetic sensitive surface according to the gap distance m1.

Moreover, the observation point 2 (observation point 2 of Example 2 mentioned later) shown to Fig.7 (a) can be represented as the following range expressions, for example.
Range formula:
Conductor width A [mm] of the U-shaped portion 31: 0.780 ≧ A ≧ 0.390
Conductor thickness D [mm]: D = 0.230
Aspect ratio A / D of primary conductor 13:
(0.780 / 0.230 =) 3.4 ≧ A / D ≧ (0.390 / 0.230 =) 1.6
Vertical separation distance E = D / 2 + E ′ [mm]:
(0.230 / 2 + 0.300 =) + 0.42 ≧ E ≧ −0.42
(E ′ is the vertical separation distance between the coordinate origin P and the upper surface of the U-shaped portion 31)
Horizontal separation distance C = C ′ + m1 + A / 2 [mm]:
(0.3 + 0.1 + 0.780 / 2 =) 0.79 ≧ C ≧ (A / 2 = 0.390 / 2 =) 0.19

Moreover, the observation point 3 (observation point 3 of Example 2 described later) shown in FIG. 7A can be expressed, for example, as the following range expression.
Range formula:
Conductor width A [mm] of the U-shaped portion 31: 0.780 ≧ A ≧ 0.390
Conductor thickness D [mm]: D = 0.230
Primary conductor aspect ratio A / D:
(0.780 / 0.230 =) 3.4 ≧ A / D ≧ (0.390 / 0.230 =) 1.6
Vertical separation distance E = D / 2 + E ′ [mm]:
(0.230 / 2 + 0.300 =) + 0.42 ≧ E ≧ −0.42
Horizontal separation distance C = C ′ + m1 + A / 2 [mm]:
(About 0.85 + 0.3 + 0.1 + 0.780 / 2 =) 1.6 ≧ C ≧ (A / 2 = 0.390 / 2 =) 0.19

In addition, FIG. 9 (a), (b) of FIG. 9 mentioned later, FIG. 10 (a), (b) satisfies the said range.
Therefore, the arrangement position of the magnetic field conversion element 41 in the current sensor 10 shown in FIG. 2 can be set to a position that satisfies the range equation. However, the present invention is not limited to this.

Examples of the present invention will be described below, but the present invention is not limited to these examples.
Regarding the analysis accuracy of static magnetic field analysis, separately, when a current is passed through the primary conductor of the current sensor, a parallel magnetic field is applied to the current sensor so as to be perpendicular to the magnetic sensing surface of the Hall element as the magnetic field conversion element. The relationship between current sensitivity and magnetic sensitivity was determined from these measurement results. As a result, the value of the induced magnetic flux density obtained from the static magnetic field analysis by rough 3D modeling was about 10% or more different from the magnetic flux density (per 1 [A]) obtained from the measurement. Even if the dimensions were different, the difference was similar. It was confirmed that a certain degree of certainty was obtained in the calculation of the induced magnetic flux density by the current by numerical simulation.

Example 1
The thickness of the lead frame 1 is 0.230 [mm].
As shown in FIG. 2, the primary conductor 13 has a substantially U-shaped shape with the corners 31 a and 31 b of the primary conductor 13 on the left and right in a plan view. The U-shaped portion 31 of the primary conductor 13 and the island body 21 are arranged with a gap distance m1 = 0.1 [mm]. In other words, the gap distance m1 between the IC chip side edge of the U-shaped portion 31 of the primary conductor 13 and the side edge of the primary conductor 13 of the IC chip is set to 0.100 [mm].

The shape of the IC chip 11 placed on the island body 21 is a square in plan view having a width of about 2.3 × length of about 1.4 × thickness of 0.20 mm.
The conductor width A that becomes the current path of the U-shaped portion 31 of the primary conductor 13 is 0.390 [mm], and the thickness D of the primary conductor 13 is 0.230 [mm], which is the same as that of the lead frame.
As shown in FIG. 7A, assuming the arrangement of the Hall element as the magnetic field conversion element 41 constituting the IC chip 11, the center of the magnetic sensitive surface of the Hall element is the observation point of the magnetic flux density, and the magnetic flux at the observation point. The density was determined by magnetic field simulation based on the integral element method.

  In FIG. 7A, as an example of the arrangement of the magnetic field conversion elements, it is drawn so as to overlap with the position of observation point 2 (in the drawing, observation point 2 is drawn on the upper surface of IC chip 11 as an example). From the edge of the IC chip 11 toward the inside of the IC chip 11, a portion having a distance C ′ = 0.3 [mm] entering from both sides forming the corners of the IC chip 11 is indicated on the equal magnetic flux density line. Is one of the magnetosensitive surface centers. That is, the distance C ′ from the edge of the IC chip 11 to the magnetic flux density observation point (center of the magnetic sensitive surface of the Hall element) entering the inside of the chip is set to 0.300 [mm]. In this example, the observation point 2 is located there.

The observation point 1 is located on a line passing through the coordinate origin P in the X-axis direction (C = 0). Further, the observation point 1 is separated from the coordinate origin P in the Z-axis direction by a distance of E ′ = 0.070 [mm] further upward from the upper surface of the primary conductor 13 through a half of the primary conductor thickness D. (E = D / 2 + E ′ = 0.230 / 2 + 0.070).
The observation point 2 is half of the conductor width A in the X-axis direction as viewed from the observation point 1 passing through the coordinate origin P in the X-axis direction 0.390 / 2 + (m1 =) 0.100 + from the edge of the IC chip 11 It is in a position where only (C ′ =) 0.3 mm is inside. In the Z-axis direction, from the coordinate origin P (the thickness center of the primary conductor 13), through the half of the primary conductor thickness D, further upward from the upper surface of the primary conductor 13 (separation distance E '=) 0.070 [mm ] At a distance of

The position of the observation point 2 in the X-axis direction, that is, the horizontal separation distance C [mm] from the coordinate origin P is expressed as follows.
C = C '+ m1 + A / 2
= 0.300 + 0.100 + 0.390 / 2 = 0.595
The position of the observation point 2 in the Z-axis direction, that is, the vertical separation distance E [mm] from the coordinate origin P is expressed as follows.
E = E ′ + D / 2 = 0.070 + 0.230 / 2 = 0.185

  The observation point 3 is located on the extension of the line connecting the observation point 1 and the observation point 2 and corresponds to a position in the X-axis direction corresponding to the half position of the long side of the IC chip 11 in this example (FIG. 7A ) At the center of the primary conductor 13 in the X-axis direction). Then, the observation point 3 is half of the conductor width A 0.390 / 2 + m1 (= 0.100) + IC chip 11 in the X-axis direction (as viewed from the observation point 1 in the Z-axis direction passing through the coordinate origin P). In the Z-axis direction, it is separated from the long side width (horizontal width) by half (about 2.3 / 2 = about 1.4 [mm]), and from the coordinate origin P through half of the primary conductor thickness D, This represents a position further away from the upper surface of the primary conductor 13 by a distance of 0.070 [mm] (separation distance E ′ =).

The position of the observation point 3 in the X-axis direction (horizontal separation distance from the coordinate origin P) C [mm] is expressed as follows.
C = C '+ m1 + A / 2
= About 2.3 / 2 [mm] + 0.100 + 0.390 / 2 = About 1.4 [mm]
The position of the observation point 3 in the Z-axis direction (vertical separation distance from the coordinate origin P) E [mm] is expressed as follows.
E = E ′ + D / 2 = 0.070 + 0.230 / 2 = 0.185

  For the current sensor 10 with the observation points set in this way, by conducting the static magnetic field analysis by energizing 1 [A] to the primary conductor 13 by the integral element method, and around the corners 11a and 11b of the IC chip 11, FIG. 7B shows the magnetic flux density plotted so as to include the periphery of the corner portions 31 a and 31 b of the primary conductor 13.

FIG. 7B shows the strength of the magnetic flux density and the direction of the magnetic flux of the triaxial resultant force in terms of vector length and direction at an interval of 0.05 mm in the X-axis to Z-axis plane in FIG. FIG. In the cross section of the primary conductor 13 shown in FIG. 7A, current enters from the right U-shaped portion 31R and exits from the other left U-shaped portion 31 (in FIG. 2, the measured current is output from the terminal portion 33). In and out of the terminal portion 32).
In FIG. 7B, a space region in the X-axis direction sandwiched between the corner portions 31a and 31b of the primary conductor 13, and a space region in the + Z-axis direction and the −Z-axis direction around the space region (for example, observation point 2, observation At point 3), it can be seen that the direction of the magnetic flux is substantially along the + Z-axis direction.

FIG. 8 shows an example in which the magnetic flux density strength in the Z-axis direction is expressed by contour lines of 0.0001 [T] intervals at intervals of 0.05 [mm] on the X-axis-Y-axis plane in FIG. .
Observation point 1, observation point 2, and observation point 3 in FIG. 8 are the same observation points as observation points 1 to 3 set in FIG. 7A, and observation point 1, observation point 2, and observation point 3 are the same. The line segment passing through is parallel to the X axis. Further, the line segments passing through observation point 4, observation point 2, and observation point 5 in FIG. 8 are parallel to the Y axis.

That is, the position of the observation point 4 in the X-axis direction is the same as the position of the observation point 2 in the X-axis direction. As shown in FIG. 8, the observation point 4 is positioned at the center in the conductor width direction, and the Z-axis direction is a position where the separation distance E ′ = 0.070 [mm].
The observation point 5 is on the extension of the line segment connecting the observation point 4 and the observation point 2 in the −Y-axis direction, and the position in the X-axis direction is {the half of the conductor width A 0.390 / 2} from the coordinate origin P. + {M1 (= 0.100 [mm])} + {Half side length (vertical width) of the IC chip 11 (1.4 / 2 [mm])} = 0.993 [mm]. Further, the position in the Z-axis direction is a position where the separation distance E ′ = 0.070 [mm].

  The observation point 2 is a point at the center of the magnetic sensitive surface that enters C ′ = 0.3 [mm] from both ends of the two sides forming one corner 11 b of the IC chip 11. In the present example, the induced magnetic flux density at the observation point 2 was about 0.5 [mT] with respect to the energizing current 1 [A]. It can be seen that the equal magnetic flux density lines in the range of 0.5 to 0.6 [mT] including the observation point 2 are distributed on the arc with respect to the corner portion 11b. In the vicinity of observation point 2, the magnetic flux density in the Z-axis direction changes at intervals of 0.1 [mT] with an interval width of about 0.15 to about 0.2 [mm] on the X-axis-Y-axis plane. .

  By arranging a plurality of magnetic field conversion elements 41, the sensitivity is improved. In particular, by arranging the magnetic field conversion elements 41b on the equal magnetic flux density line, a uniform SN ratio having the same signal level and the same noise level is obtained. A certain magnetic field conversion element output can be added. Therefore, the magnetic sensitivity, that is, the current sensitivity can be improved most efficiently. In other words, if two are arranged on the equal magnetic flux density line, the sensitivity obtained from a magnetic flux density of about 0.5 [mT] is doubled, and if four are provided, the sensitivity is also quadrupled. In addition to the corner portion 11b, the magnetic field conversion element 41a is similarly arranged in the corner portion 11a, so that double sensitivity can be obtained.

The above configuration can be stored, for example, in an IC SSOP 24-pin package having a size of 8.2 × 5.3 × 2.1 [mm]. Even if the size of the IC chip 11 to be placed on the island body 21 is slightly widened, it is sufficiently packaged even if it is a square in plan view with a width of about 2.7 × length of about 1.4 × thickness of 0.20 mm. Can fit in.
The resistance value of the primary conductor 13 is, for example, about 1.9 [mΩ].
It has been shown that the current sensor 10 according to the present application can be used as an inexpensive and practical current sensor while increasing the effect of simplification in manufacturing.

(Comparative Example 1)
As described in the background art as a comparative example, in order to improve the sensitivity, a current sensor was assumed in which the IC chip was turned over and flip chip bonding was performed, and the chip was attached so as to be close to the primary conductor. The configuration corresponds to a pattern in which all of the current 316 passes through the U-shaped current conductor portion 304a as shown in FIG. 12 of Patent Document 3 (International Publication No. 2006/130393).
Assuming that the Hall effect element 308 is arranged just below the center of the U-shape corresponding to the magnetic field center position of the U-shaped primary conductor, the magnetic flux density at the center of the magnetosensitive surface was obtained by static magnetic field analysis by the integral element method. In the magnetic field analysis, the primary conductor shape was not a triangular shape but a straight rectangular shape.

The magnetic field analysis conditions were as follows.
The thickness of the lead frame 1 was 0.230 [mm].
In the primary conductor, the current round trip path corresponding to the conductors 304a and 302 in FIG. 12 of Patent Document 3 is a simple rectangular shape, and the bent portion is a beautiful U-shape of the alphabet. The radius was 0.135 [mm], the conductor width was 0.43 [mm], and a measurement current of 1 [A] was passed through the primary conductor.

The shape of the IC chip including the magnetic field conversion element is a square in plan view having a width of about 2.3 × length of about 1.4 × 0.070 mm square, and the magnetic field conversion element in the vicinity of the IC chip surface has a thickness of 0.07 [ mm] through an insulating film of [mm], and arranged just above the center point of the U-shape of the primary conductor.
The magnetic flux density at the observation position corresponding to the center of the magnetic sensitive surface was a value of about 1 [mT].
In the method in Comparative Example 1, in order to obtain maximum sensitivity while considering sensitivity variation, when one Hall element is arranged at a U-shaped magnetic flux concentration portion and the U-shape is one location, a measurement current of 1 [ With respect to A], a magnetic field sensitivity having an induced magnetic flux density of about 1 [mT] is obtained, and a current sensitivity corresponding to that is obtained.

(Example 2)
The basic configuration is the same as that of the first embodiment.
The thickness of the lead frame 1, that is, the thickness D of the U-shaped portion 31 in FIG. 7A is 0.230 [mm]. A vertical separation distance E ′ between the coordinate origin P and the upper surface of the U-shaped portion 31 is set to 0.070 [mm]. The conductor width A of the U-shaped portion 31 is 0.390 [mm], and the gap distance m1 is 0.100 [mm]. The distance C ′ entering from the edge of the two sides forming the corner of the IC chip 11 from the edge of the IC chip 11 to the inside of the IC chip 11 is set to 0.3 [mm], and the magnetic flux density is observed there. One of the points (or the center of the magnetic sensitive surface of the Hall element as the magnetic field conversion element 41) is set. A measurement current of 1 [A] was passed through the primary conductor. The IC chip 11 has a rectangular shape in plan view with a width of about 2.3 × length of about 1.4 × thickness of 0.20 [mm]. The XYZ coordinate system and the coordinate origin P were set in the same manner as in Example 1.

Unlike the first embodiment, in the second embodiment, the conductor width A and the separation distance E ′ in FIG. 7A are changed as parameters, and the position is determined by the combination of the horizontal separation distance C and the vertical separation distance E. The magnetic flux density (in the Z-axis direction) passing through a certain observation point (or the center point of the magnetic sensitive surface of the magnetic field conversion element) was obtained by static magnetic field simulation.
At observation points 1 to 5, only the value of the separation distance E ′ in the vertical direction (Z-axis direction), and accordingly, the total vertical separation distance E is different from that of the first embodiment. , The separation distance E ′ was changed. That is, the conductor thickness D of the U-shaped portion 31 is fixed at 0.230, and the vertical separation distance E ′ between the center of the magnetic sensitive surface and the upper surface of the primary conductor is changed to 0.070, 0.200, and 0.300. I let you.

The vertical separation distance E [mm] can be expressed by the following equation.
E = E ′ + D / 2 = E ′ + 0.230 / 2
At observation point 1 to observation point 5, only the value of parameter A (conductor width) is set in the horizontal direction (X-axis direction or Y-axis direction). The parameter A was changed at each observation point. The distance C ′ entering from the edge of the two sides forming the corner of the IC chip 11 from the edge of the IC chip 11 to the inside of the IC chip 11 remains 0.3 [mm], and the gap distance m1 Was also kept at 0.1 [mm]. The conductor width A of the U-shaped portion 31 was changed to 0.390, 0.510, and 0.780.

The horizontal separation distance C [mm] can be expressed by the following equation.
C = C ′ + m1 + A / 2 = 0.300 + 0.100 + A / 2
FIG. 9A is an example of a magnetic field simulation result in which the magnetic flux density strength in the Z-axis direction is plotted along observation point 1, observation point 2, and observation point 3 on the X-axis-Z-axis plane.

  Observation point 1 in FIG. 8 (that is, the origin of the X axis in the horizontal axis in FIG. 9A) −observation point 2 along observation point 3 (that is, parameter C in FIG. The magnetic flux density penetrating in the Z-axis direction (that is, perpendicularly to the center point of the Hall element magnetic sensing surface) is examined by moving it in the direction at an interval of 0.05 mm. As in FIGS. 7A, 7B, and 8, the XYZ coordinate system was set and the origin coordinate P was set in the same manner. In FIG. 9A, the direction toward the inside of the IC chip 11 is a minus sign.

  FIG. 9B is an example of a magnetic field simulation result in which the magnetic flux density strength in the Z-axis direction is plotted along observation point 4, observation point 2, and observation point 5 on the Y-axis-Z-axis plane (parameter A , E ′ was changed in the same manner as in FIG. Observation point 4 in FIG. 8 (that is, the origin of the horizontal axis Y-axis in FIG. 9B) −observation point 2 along observation point 5 in the Z-axis direction (that is, the center of the Hall element magnetosensitive surface) The magnetic flux density penetrating the dots vertically) was examined.

As can be seen from FIG. 9, even when the conductor width A of the U-shaped portion 31 is set to 0.390 and the separation distance E ′ is set as a parameter, 0.070, 0.200, 0.300 is changed. From 5 [mT], it can be seen that an induced magnetic flux density around that value can be obtained.
Next, the static magnetic field analysis was performed by changing the conductor width A of the U-shaped portion 31 to 0.390, 0.510, and 0.780 and fixing the vertical separation distance E ′ to 0.070. .

FIG. 10A shows a magnetic field simulation result in which the magnetic flux density strength in the Z-axis direction is plotted along observation point 1, observation point 2, and observation point 3 on the X-axis-Z-axis plane.
FIG. 10B shows a magnetic field simulation result in which the magnetic flux density strength in the Z-axis direction is plotted along observation point 4, observation point 2, and observation point 5 in the Y-axis-Z-axis plane (parameter A). , E ′ was changed in the same manner as in FIG.

  In FIG. 10B as well, as in FIG. 10A, the horizontal direction observation range of the magnetic flux density induced in the space is totaled for (32 + 1) times at a space interval of 0.05 [mm]. As above, the calculation was performed over a spatial range of 0.05 × 32 = 1.6 [mm]. The spatial range in which the magnetic flux density is observed is constant even when the calculation is performed by changing the conductor width A. Therefore, when plotting in the horizontal direction (X-axis or Y-axis direction) with the center of the conductor width A as the origin, the distance from the origin to the same magnetic flux density observation point increases as the conductor width A increases. In FIG. 10B, this is why the plot range shifts (to the minus side of the X axis or Y axis) every time the conductor width A is increased.

Even if the conductor width A increases from 0.390 to 0.780 [mm], the observation point 3 from the region close to the primary conductor on the observation point 1 side or the observation point 4 side passes through the observation point 2. From the observation point 5, the sensitivity decreased to about several tens of percent. In the examination range of this example, it was confirmed that an induction magnetic flux density of about 0.5 [mT] can be obtained at the observation point 2.
Therefore, in the primary conductor shape in plan view of FIG. 2, even if the width of the conductor portion other than the periphery of the corner portions 31a and 31b of the primary conductor 13 is locally doubled, the magnetic sensitivity is reduced by about 1/10. Without making it possible, the electrical resistance of the primary conductor 13 can be suppressed, and the heat dissipation effect can be promoted. FIG. 11 is an example of a schematic diagram of a current sensor in which the width of the conductor portion other than the periphery of the corner portions 31a and 31b of the primary conductor 13 is locally increased.

(Example 3)
In the current sensor 10 used in Example 1, the island part 12, that is, the island body 21, is down-pressed as shown in FIG. 3B, and the observation points 2, 3, and 5 set on the upper surface of the IC chip 11 are The magnetic flux density at the observation points 2, 3, and 5 was obtained under the same conditions as in Example 1 with the same vertical height as the thickness center of the U-shaped portion 31 of the primary conductor 13.

As a result, the magnetic flux density in the Z-axis direction at the observation point 2 was about 0.61 [mT]. The magnetic flux density in the Z-axis direction at the observation point 3 was about 0.49 [mT]. The magnetic flux density in the Z-axis direction at the observation point 5 was about 0.49 [mT].
In the case of Example 1 where the island portion 12 is not down-pressed, the magnetic flux density in the Z-axis direction at the observation point 2 was about 0.5 [mT] as described above, whereas the island portion 12 When it is down-pressed, it is about 0.61 [mT], and as can be seen from the change in the value of the magnetic flux density at the observation point 2, as compared with Example 1 in which the island portion 12 is not down-pressed, In Example 3 in which the island portion 12 is down-pressed, the magnetic flux density is improved, and it can be seen that down-pressing is useful for improving the signal strength.

DESCRIPTION OF SYMBOLS 1 Lead frame 5 Package 10 Current sensor 11 IC chip 11a, 11b Corner | angular part 12 Island part 13 Primary conductor 14 Sensor lead terminal 21 Island main body 22 Lead terminal 31 U-shaped part 31a, 31b Corner part 32, 33 Terminal part 41 Magnetic field conversion element

Claims (10)

An IC chip having a primary conductor through which a measurement current flows, a magnetic field conversion element for detecting a magnetic flux induced from the measurement current and having a square shape in plan view, an island portion on which the IC chip is placed, a lead terminal, and the primary A lead frame integrally formed with a conductor, and a current sensor comprising:
The primary conductor is electrically insulated from the island portion, and has at least one corner portion having a shape extending from the outside at one corner and two left and right sides of the IC chip in plan view. Have
The current sensor, wherein the magnetic field conversion element is disposed at a corner portion located inside the corner portion of the IC chip.   The current sensor according to claim 1, comprising a plurality of the magnetic field conversion elements.   The current sensor according to claim 1, wherein the plurality of magnetic field conversion elements are arranged along a chamfered curve virtually drawn at the corner of the IC chip.   4. The current sensor according to claim 3, wherein the chamfered curve drawn virtually is a curve along an isomagnetic flux density line formed by a magnetic flux induced in the primary conductor by the measurement current.   5. The current sensor according to claim 1, wherein the island portion is down-pressed so that a position in a vertical direction is lower than that of the primary conductor.   The current sensor according to claim 1, wherein the magnetic field conversion element is a silicon Hall element. A method of manufacturing a current sensor comprising: a primary conductor through which a measurement current flows; and an IC chip having a magnetic field conversion element for detecting a magnetic flux induced from the measurement current and having a square shape in plan view,
An island part having an island body having the same shape as the IC chip, a primary conductor and a lead terminal electrically isolated from the island part are formed, and the primary conductor is one corner of the island body in plan view. And placing the IC chip on the island body of the lead frame having at least one corner portion formed on the left and right sides thereof from the outside; and
Electrically connecting the IC chip placed on the island body and the lead terminal;
And a step of integrally molding the island part, the IC chip, the primary conductor, and the lead terminal into a package, and manufacturing the current sensor.   The method of manufacturing a current sensor according to claim 7, comprising a plurality of the magnetic field conversion elements.   The method of manufacturing a current sensor according to claim 8, wherein the plurality of magnetic field conversion elements are arranged along a chamfer curve virtually drawn at the corner of the IC chip.   10. The current sensor according to claim 9, wherein the virtually drawn chamfer curve is a curve along an equal magnetic flux density line formed by a magnetic flux induced in the primary conductor by the measurement current. Method.

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