JP2015184206A - Current detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow a current detector to keep an excellent accuracy of current detection over a long period of time.SOLUTION: According to the present invention, there is provided a current detector including: a resistor for current detection; a pair of lands having the resistor for allowing a current to flow between both ends of the resistor; a pair of connecting materials connecting the resistor and the pair of lands together; and a pair of bonding wires connected to the resistor for detecting a voltage, the bonding wires and the resistor being connected together in a region located in an inward direction from the inside edge part of the pair of connecting materials.

Description

  The present invention relates to a current detection technique.

It is well known to use a chip resistor having a very small resistance value of about milliohm for current detection. The chip resistor includes, for example, a resistor made of a noble metal alloy or a metal alloy, a highly conductive electrode, and a molten solder material.
For example, Patent Document 1 below discloses a mounting structure of a current detection resistor.

JP 2012-233706 A

  FIG. 9 is a side view showing an example of a mounting structure of a shunt resistor that is an example of the current detection device (current detection resistor) described in Patent Document 1.

  A metal substrate 102 such as aluminum for mounting the shunt resistor 100 is provided between the wiring patterns 103a and 103b and the wiring patterns 103a and 103b that are formed on the metal substrate 102 and allow current to flow through the resistor 100. The resistor 101 includes solder layers 105a and 105b that connect the resistor 101 and the wiring patterns 103a and 103b. In addition, a pair of voltage detection wirings 107 a and 107 b that detect voltages generated at both ends of the shunt resistor 100 formed on the substrate 102 are provided. As an example of the shunt resistor 100, a resistor made of a metal material such as Cu—Mn or Ni—Cr is used.

  The tip ends of the voltage detection wirings 107a and 107b and the voltage detection positions at both ends of the shunt resistor 100 are connected by bonding wires 109a and 109b.

  A detection current I flows through the shunt resistor 100, and a voltage V obtained by multiplying the detection current I by the resistance value R of the shunt resistor 100 is extracted from the voltage detection wirings 107a and 107b to a voltage detection circuit (not shown).

  By the way, in recent years, the current density in the product portion has increased due to the progress of miniaturization of components and the increase in current. As the current density increases, attention has been paid to the problem that electromigration occurs at the solder joint. In particular, there is a high possibility of electromigration at locations where the temperature is high and the current density is high.

  In the structure of FIG. 9, the current concentrates particularly on the circled portion 111. If the use is continued for a long time in this state, the solder layers 105a and 105b of the circled portion 111 may be lost by electromigration. As a result, since the L dimension of the resistor is increased, the potential difference between the bonding wires 109a and 109b which are voltage detection terminals is increased. That is, the resistance value drifts to the higher one.

  For this reason, in long-term use, such as 10 years, there existed a problem that it became difficult to maintain the current detection accuracy of a current detection apparatus (current detection resistor) favorable.

  An object of the present invention is to maintain good current detection accuracy in a current detection device over a long period of time.

  According to an aspect of the present invention, a current detection resistor, a pair of lands for mounting a current detection resistor, a current flowing between both ends of the current detection resistor, and the current detection resistor A pair of connecting materials for connecting the resistor and the pair of lands, respectively, and a pair of bonding wires connected to the current detection resistor for detecting voltage, the bonding wire and current detection A current detection device is provided in which the connection position with the resistor is set to a region further inside than the inner ends of the pair of connection members.

  According to the structure of this current detection device, the connecting material was scraped in a direction in which the distance between the opposite inner end portions of the connecting material adhesion region becomes longer due to electromigration at the junction between the resistor and the wiring pattern. However, since the resistance between the voltage detection positions which are voltage detection terminals does not change, the detection accuracy can be maintained. In addition to the electromigration, the detection accuracy can be maintained even if there is a crack in the joint between the resistor and the wiring pattern for some reason.

  The connection material may be interposed between an end portion of the resistor of the current detection resistor and the land. The connecting material directly connects the end of the resistor and the land.

  The current detection resistor includes a resistance portion and a terminal portion using a single resistance material.

  For example, a recess is formed in a region excluding the end, and this recess is used as the main body. By forming the step by the recess or the like, it is also possible to prevent the connecting material such as a solder material from climbing up to the portion corresponding to the connecting portion of the bonding wire.

  It is preferable that the current detection resistor has a structure that regulates a connection position with the bonding wire.

  ADVANTAGE OF THE INVENTION According to this invention, the electric current detection precision in an electric current detection apparatus can be kept favorable over a long period of time.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows one structural example of the current detection apparatus by the 1st Embodiment of this invention, the upper figure is a perspective view of a current detection apparatus, and the lower figure is a top view of the current detection apparatus corresponding to the upper figure is there. 2 (a) and 2 (b) show the relationship between the resistor and the wiring pattern by the solder layer in the current detection device having the bonding wire connection structure shown in the lower part of FIG. 1 (corresponding to FIG. 2 (a)). It is a figure which shows the example of a time-dependent change of a joining area | region. FIG. 3 is an equivalent circuit diagram for performing 4-terminal measurement with the structure shown in FIG. 2. It is sectional drawing which shows the example of 1 structure of the electric current detection apparatus by the 2nd Embodiment of this invention. It is a perspective view which shows the example of 1 structure of the electric current detection apparatus by the 3rd Embodiment of this invention. It is a perspective view which shows one structural example of the electric current detection apparatus by the 4th Embodiment of this invention. It is a perspective view which shows one structural example of the electric current detection apparatus by the 4th Embodiment of this invention. It is a perspective view which shows one structural example of the electric current detection apparatus by the 4th Embodiment of this invention. It is a side view which shows an example of the mounting structure of the shunt resistor which is an example of the electric current detection apparatus (current detection resistor) of patent document 1.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram showing a configuration example of a current detection device according to a first embodiment of the present invention, an upper diagram is a perspective view of the current detection device, and a lower diagram is a current detection device corresponding to the upper diagram. FIG. The basic structure, material, and the like may be the same as the structure described in FIG.

  The current detection device 1 includes, for example, wiring patterns 5a and 5b for flowing a current between both ends of a current detection resistor 3 formed on a metal substrate (not shown) and having a low-resistance resistor, and a wiring pattern 5a. 5b, and connecting layers connecting the terminal portions 3b and 3c at both ends of the resistor 3 and the wiring patterns 5a and 5b, for example, solder layers 7a and 7b formed of Sn-Ag-Cu solder or the like. Have. As the connection material, in addition to solder, a conductive adhesive, a brazing material, or the like may be used. Regarding the influence of electromigration, the present invention is particularly effective for Sn-based connecting materials, for example. Further, in the current detection device 1, a pair of voltage detection wirings 8 a and 8 b that are formed on the substrate and detect voltages generated at both ends of the resistor 3, and voltage detection positions P 1 and P 2 that are separated from each other by a certain distance in the resistor 3. However, the main body 3a of the resistor 3 is connected by bonding wires 11a and 11b. The bonding wires 11a and 11b function as voltage detection terminals. In FIG. 1 and the like, the resistor and the resistor are illustrated as a simple structure. Electrodes may be formed on both ends of the resistor of the resistor 3.

A detection current I flows between the terminal portions 3b and 3c of the resistor 3, and a voltage V obtained by multiplying the resistance value R of the resistor 3 is extracted from the voltage detection wirings 8a and 8b to a voltage detection circuit (not shown).
With this structure, 4-terminal measurement in the resistor 3 becomes possible.

  Here, one end of the voltage detection terminals (bonding wires 11a and 11b) on the side of the resistor 3 has voltage detection positions P1 and P2 that do not reach the solder adhesion regions (mounting regions, lands, hereinafter the same) AR1 and AR2 in plan view. In FIG. The solder layers 7a and 7b are interposed in the solder adhesion regions (AR1 and AR2) so as to be directly connected to, for example, resistors at both ends of the wiring patterns 5a and 5b and the resistor 3, respectively.

  2 (a) and 2 (b) show a resistor 3 made of a solder layer in the current detection device 1 having a connection structure with bonding wires 11a and 11b shown in the lower part of FIG. 1 (corresponding to FIG. 2 (a)). It is a figure which shows the example of a time-dependent change of the junction area | region of the wiring pattern 5a, 5b. As shown in FIG. 2B, the solder adhesion areas AR1 and AR2, which are the joining areas, are scraped off from the opposite inner end side due to the influence of electromigration as described in FIG. The positions of the inner end portions of the solder layers 7a and 7b change in the direction in which the distance between the opposite inner end portions of the solder attachment regions AR1 and AR2 increases, that is, in the direction indicated by the arrows 14a and 14b, and the solder attachment regions AR1a and AR1a, It changes as shown in AR2a.

  Therefore, the voltage detection terminals (bonding wires 11a and 11b) are in positions that do not cover the initial solder adhesion areas AR1 and AR2 in plan view and are opposed to the solder adhesion areas AR1 and AR2 on the upper surface of the resistor 3. The resistor 3 is connected at the voltage detection positions P1 and P2 between the inner end portions. With such a structure, even if there is a change over time due to long-term use, the voltage detection positions P1 and P2 are kept between the opposing inner ends of the solder adhesion areas AR1a and AR2a after the change over time. .

  According to the structure of the current detection device 1, soldering is performed in a direction in which the distance between the opposite inner ends of the solder adhesion regions AR <b> 1 and AR <b> 2 becomes longer due to electromigration at the joint portion between the resistor 3 and the wiring patterns 5 a and 5 b. Even if the power is removed, the resistance between the voltage detection positions P1 and P2, which are voltage detection terminals, does not change, so that the voltage detection accuracy can be maintained for a long time.

  The distance between the voltage detection positions P1 and P2 is an inner area avoiding the solder adhesion areas AR1 and AR2, and the distance between the voltage detection positions P1 and P2 only needs to be some distance away. In this case, the detection sensitivity can be improved by amplifying the detected voltage.

  FIG. 3 is an equivalent circuit diagram for performing four-terminal measurement using the structure shown in FIG. In the resistor 3 of the current detection device 1, even if the solder layers 7a and 7b are shaved, as shown in FIG. 3, a bonding wire that functions as a voltage detection terminal further inside than the inner end of the solder adhesion region is provided. The resistor 3 is connected directly or indirectly at the voltage detection positions P1, P2, and the distance between the voltage detection positions P1, P2 does not change. In addition, when a current flows straight between the voltage detection positions P1 and P2, there is no change in the voltage detection positions P1 and P2 as shown by arrows 14a and 14b in FIG. Although the distance between the opposing inner ends of the regions AR1 and AR2 becomes longer, the solder tends to be scraped while the inner ends are kept in parallel. There is almost no impact.

  Therefore, according to the current detection device according to the present embodiment, even if the solder is scraped off due to the electromigration effect and the resistance value in the mounted state of the resistor changes, the effect is not detected in the current detection in the four-terminal measurement. Since it is hard to receive, there exists an advantage that an electric current detection precision can be kept favorable over a long period of time.

(Second Embodiment)
FIG. 4 is a cross-sectional view showing an example of the configuration of the current detection device according to the second embodiment of the present invention. A current detection device 31 shown in FIG. 4 is a resistor having a low-resistance resistor, for example, formed between a wiring pattern 35a and 35b and a wiring pattern 35a and 35b. And a solder layer 37a, 37b for connecting the resistor 33 and the wiring patterns 35a, 35b. Here, in FIG. 4, the resistor 33 is composed of resistor end portions 33 b and 33 c connected to the wiring patterns 35 a and 35 b by the solder layers 37 a and 37 b, and a main body portion 33 a having a step difference. In the mounting structure shown in FIG. 4, the resistor body 33a of the resistor 33 is lifted in the height direction with respect to the end portions 33b and 33c (away from the wiring patterns 35a and 35b). Direction) structure. This step is denoted by Δh1.

  In the current detection device 31, a pair of voltage detection wirings 39 a and 39 b that are formed on the substrate and detect voltages generated at both ends of the resistor 33 and voltage detection positions P 3 and P 4 at both ends of the resistor 33 are bonded to each other. They are connected by wires 41a and 41b. The voltage detection positions P3 and P4 are located in the main body portion 33a of the resistor 33 lifted in the height direction with respect to the end portions 33b and 33c.

  A detection current I flows through the resistor 33, and a voltage V obtained by multiplying the resistance value R of the resistor 33 is extracted from the voltage detection wirings 39a and 39b to a voltage detection circuit (not shown). With this structure in the current detection device 31, four-terminal measurement is possible.

  According to this structure, even if the solder is shaved off in the direction in which the distance between the opposite inner end portions of the solder adhesion region becomes longer due to electromigration at the joint portion between the resistor 33 and the wiring patterns 35a and 35b, Since the resistance between the voltage detection positions P3 and P4 which are voltage detection terminals does not change, the current detection accuracy of the current detection device 31 can be maintained.

  In addition, since the main body portion 33a of the resistor 33 has a structure that is lifted in the height direction with respect to the end portions 33b and 33c, the solder detection layers 37a and 37b are voltage detection terminals. It is also possible to suppress climbing up to P3 and P4.

  Therefore, there is an advantage that good current detection accuracy can be maintained over a long period of time even if the solder is shaved due to the influence of electromigration.

(Third embodiment)
FIG. 5 is a perspective view showing a configuration example of the current detection device according to the third embodiment of the present invention. A current detection device 51 shown in FIG. 5 is formed between, for example, wiring patterns 55a and 55b that are formed on a metal substrate (not shown) and allows current to flow through the resistor 53, and the wiring patterns 55a and 55b. It has the solder layer 57a, 57b which connects the resistor 53 which has a resistor, and wiring pattern 55a, 55b. Here, in FIG. 5, a main body portion 53a formed by forming a concave portion 53d on one surface of the resistor 53 and end portions 53b and 53c located at both ends of the main body portion 53a are defined. . In the main body 53a of the resistor 53, a step h2 is formed by forming a thin portion whose thickness is reduced by the recess 53d with respect to the end portions 53b and 53c. The wiring patterns 55a and 55b and the end portions 53b and 53c are connected by providing solder layers 57a and 57b between the end portions 53b and 53c and the wiring patterns 55a and 55b, respectively. The surface of the main body 53a on the concave 53d side is covered with a protective film 58. As described above, the resistor 53 may include the resistor portion (main body portion 53a) and the terminal portions 53b and 53c using a single resistor material.

  In the current detection device 51, a pair of voltage detection wirings 59a and 59b formed on the substrate for detecting a voltage generated at both ends of the resistor 53, and voltage detection positions P5 and P6 at both ends of the resistor 53 are bonded. They are connected by wires 61a and 61b. The voltage detection positions P5 and P6 are located in the region of the main body 53a where the resistor 53 is thin relative to the ends 53b and 53c.

  A detection current I flows through the resistor 53, and a voltage V obtained by multiplying the resistance value R of the resistor 53 is extracted from the voltage detection wirings 59a and 59b to a voltage detection circuit (not shown). This structure enables four-terminal measurement.

  According to this structure, even if the solder is shaved off in the direction in which the distance between the opposite inner end portions of the solder adhesion region becomes longer due to electromigration at the joint portion between the resistor 53 and the wiring patterns 55a and 55b, Since the resistance between the voltage detection positions P5 and P6 that are voltage detection terminals does not change, the detection accuracy of the current detection device 51 can be maintained.

  In addition, since the main body portion 53a between the end portions 53b and 53c is covered with the protective layer 58, the solder layers 57a and 57b are prevented from rising up to the voltage detection positions P5 and P6 which are voltage detection terminals. You can also.

  Therefore, there is an advantage that good current detection accuracy can be maintained over a long period of time even if the solder is shaved due to the influence of electromigration.

(Fourth embodiment)
6 to 8 are perspective views showing one configuration example of the current detection device according to the fourth embodiment of the present invention. 6 to 8 are diagrams showing examples of techniques for preventing wire bonding in the solder adhesion region. Here, a description will be given by taking as an example a structure that is thinned by providing a concave portion in the main body according to the third embodiment of FIG. 5, but the present invention is applicable to other structures including the first or second embodiment. It is possible.

  The current detection device according to the present embodiment is characterized by including a structure that regulates a connection position portion with the bonding wire.

  The current detection device 71 shown in FIG. 6 has a thin main body 73a formed by providing a recess 73d on one surface of a resistor 73, and end portions 73b and 73c at both ends thereof as shown in FIG. A simple resistor is formed. Here, the configuration of electrodes, solder layers, and the like is omitted, but is basically the same as FIG.

  In FIG. 6, the regions of the end portions 73b and 73c that are connected to the wiring pattern by the solder layer are shown as regions outside the reference numerals L5 and L6. For example, marks P7 and P8 indicating a guideline of the position for wire bonding are attached in the inner region. This mark can be provided, for example, based on the position when the recess is formed. The mark can be formed by scraping the surface of the resistor, applying ink, or the like. In this embodiment, it is possible to visually identify the position of the connection position with the bonding wire.

  In the structure shown in FIG. 6, by performing the wire bonding operation using the marks P7 and P8 as a guideline, it is ensured that the wire bonding is performed in a region avoiding the solder adhesion region. A structure that maintains good current detection accuracy over a long period of time can be manufactured with high yield.

  The current detection device 81 shown in FIG. 7 includes a thin main body 83a formed by providing a recess 83d on one surface of the resistor 83, and end portions 83b and 83c at both ends thereof. A resistor as shown in FIG. Here, the configuration of electrodes, solder layers, and the like is omitted, but is basically the same as FIG.

  In the structure shown in FIG. 7, a protective film 85 such as an epoxy resin is formed on one end of the resistor 83 of the resistor 83 on the end 83b, 83c so as to prevent bonding. Has been. In this embodiment, the position where the bonding wire is connected is restricted by the protective film so as to avoid the solder adhesion area (land).

  In the structure shown in FIG. 7, since wire bonding is surely performed in a region that avoids the solder adhesion region protected by the protective film 85, current detection accuracy is maintained over a long period in the manufacturing process of the current detection device 81. Can be manufactured with good yield.

  The current detection device 91 shown in FIG. 8 includes a thin main body portion 93a formed by providing a concave portion 93d on one surface of the resistor 93, and end portions 93b and 93c at both ends thereof. A resistor as shown in FIG. Here, the configuration of electrodes, solder layers, and the like is omitted, but is basically the same as that shown in FIGS.

  In the structure shown in FIG. 8, a protective film 95 such as an epoxy resin is formed on one surface of the resistor 93 where wire bonding is performed, and the protective film 95 is opened in a region avoiding the end portions 93b and 93c. By exposing the surface of the resistor 93, a bonding area 95a allowed to be bonded is formed. In the present embodiment, the position where the bonding wire is connected is restricted to a specific position in the main body by the protective film and the opening.

  In the structure shown in FIG. 8, since bonding areas 95a that allow wire bonding are formed in areas avoiding the solder adhesion areas protected by the protective film 95, the positions P11 and P12 to be wire bonded are Since it is limited to the inside of the bonding area 95a, a structure that maintains good current detection accuracy over a long period can be manufactured with a high yield in the manufacturing process of the current detection device.

  A structure for not bonding to other solder adhesion regions is also included in this embodiment.

  As described above, according to each embodiment of the present invention, in the resistor having the terminal portions connected to the both ends of the main body portion by wiring and solder, further inside than the inner end portion of the solder adhesion region. A bonding wire functioning as a voltage detection terminal is connected to the resistor directly or indirectly at the voltage detection position.

  In this way, wire bonding is performed on the inner area that avoids the solder adhesion area, so the solder is scraped off by electromigration at the joint between the resistor and the wiring pattern, or for some reason such as heat shrinkage or impact. Since the resistance between the voltage detection positions that are the voltage detection terminals does not change even if the bonding state changes in the direction in which the distance between the opposite inner end portions of the bonding area that is the solder adhesion area becomes longer, such as cracks entering, Current detection accuracy can be maintained over a long period of time.

  In the above-described embodiment, the configuration and the like illustrated in the accompanying drawings are not limited to these, and can be appropriately changed within a range in which the effect of the present invention is exhibited. In addition, various modifications can be made without departing from the scope of the object of the present invention.

  Each component of the present invention can be arbitrarily selected, and an invention having a selected configuration is also included in the present invention.

  The present invention is applicable to a current detection device.

AR1, AR2 ... Solder adhesion area (land)
P1, P2 ... Voltage detection position 1 ... Current detection device 3 ... Resistor (including resistor)
3a ... main body 3b, 3c ... end 5a, 5b ... wiring pattern (land)
7a, 7b ... solder (connection material) layers 8a, 8b ... voltage detection wirings 11a, 11b ... bonding wires

Claims (4)

A current sensing resistor;
The current detection resistor is mounted, and a pair of lands for flowing a current between both ends of the current detection resistor;
A pair of connecting materials for connecting the current detection resistor and the pair of lands, respectively;
A pair of bonding wires connected to the current detection resistor for detecting voltage;
A current detection device in which a connection position between the bonding wire and the current detection resistor is a region further inside than the inner ends of the pair of connection members. The connecting material is
The current detection device according to claim 1, wherein the current detection device is interposed between an end of a resistor of the current detection resistor and the land.   The current detection device according to claim 1, wherein the current detection resistor includes a resistance portion and a terminal portion using a single resistance material.   The current detection device according to claim 1, wherein the current detection resistor includes a structure that regulates a connection position with the bonding wire.

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