JP2015094646A - Dynamic quantity measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dynamic quantity measuring device that can reduce the amount of strain applied to substrates and electronic components so as to secure reliability.SOLUTION: A dynamic quantity measuring device includes: a semiconductor chip that includes a plurality of semiconductor piezoresistors and includes a plurality of electrodes electrically connected to the plurality of semiconductor piezoresistors; an electrode section that includes a plurality of wirings electrically connected to the plurality of electrodes; a chip mounting surface where the semiconductor chip is mounted; a loading surface that is located on an opposite side of the chip mounting surface and fixed to an object to be measured; a plate material where the semiconductor chip is fixed via a bonding material so as to make a rear surface of the semiconductor chip face the chip mounting surface; a resin substrate that is fixed in an identical direction on a surface parallel to the chip mounting surface of the plate material via an adhesive material; and a wiring section that connects the electrode section and an electrode section of the resin substrate. The plate material includes: a first region facing the rear surface of the semiconductor chip; and a second region facing a rear surface of the resin substrate. The thickness of the second region of the plate material is greater than the thickness of the first region of the plate material.

Description

  The present invention relates to a mechanical quantity measuring apparatus using a semiconductor strain sensor capable of measuring strain and stress of a structure.

  As a background art, for example, Patent Document 1 describes a semiconductor strain sensor using a semiconductor such as silicon and having higher sensitivity than a conventional strain gauge using a metal thin film. Further, Patent Document 2 discloses that an electric circuit unit substrate attached to a load cell, which is the same as a mechanical quantity measuring device, can operate stably even if the rigid body portion of the load cell is distorted. A simple load cell is described. Patent Document 3 describes a strain gauge FPC (Flexible Printed Circuits) including a stretchable part that relieves strain.

JP 2009-264976 A Japanese Patent Laid-Open No. 10-176964 Japanese Patent Application Laid-Open No. 2012-225685

  The most popular method for measuring the strain and stress of a structure is a method using a strain gauge. A strain gauge has a structure in which a wiring pattern of a Cu-Ni alloy or Ni-Cr alloy metal thin film is formed on a polyimide or epoxy resin film and a lead wire is provided. Adhere with and use. The amount of strain can be calculated from the change in resistance value resulting from the deformation of the metal thin film.

  On the other hand, development of semiconductor strain sensors using semiconductors is progressing as a method for measuring strain with higher accuracy. This is a device that uses a semiconductor piezoresistor formed by doping an impurity in a semiconductor such as silicon (Si) instead of a metal thin film. A semiconductor strain sensor has a resistance change rate with respect to strain as large as several tens of times that of a strain gauge using a metal thin film, and can measure a minute strain. In addition, since the resistance change is small in the metal thin film strain gauge, an external amplifier for amplifying the obtained electric signal is required. Since the semiconductor strain sensor has a large resistance change, the obtained electrical signal can be used without using an external amplifier, and it is also possible to build an amplifier circuit on the semiconductor chip of the semiconductor strain sensor. It is expected that the convenience of use and usage will be greatly expanded.

There is a load cell in which the strain gauge or the semiconductor strain sensor is attached to a strain generating body as a means for converting a load or force into an electric signal. In recent years, the load cell is also provided with a substrate on which an electrical function necessary for the load cell is mounted. Since the substrate provided in the load cell is mounted on the strain generating body of the load cell, there is a possibility that an electric circuit portion such as solder or electronic parts on the substrate may be damaged due to the strain of the strain generating body. was there. As a method for solving the above-described problem of the conventional load cell, there are Patent Document 2 and Patent Document 3. However, in a mechanical quantity measuring device in which a substrate on which electronic components are mounted with solder is bonded to a strain generating body via an adhesive, the entire strain generating body is uniformly distorted and a substrate harder than FPC is used. Therefore, the problems described in Patent Document 2 and Patent Document 3 cannot be solved. For this reason, there is still room for improvement with respect to the influence of strain on the electronic component and the solder during measurement of the mechanical quantity.
An object of the present invention is to reduce the amount of strain applied to a substrate or an electronic component and ensure reliability.

  The present application includes a plurality of means for solving the above-described problems, and an example thereof is as follows. A semiconductor chip comprising a plurality of semiconductor piezoresistors and a plurality of electrodes electrically connected to the plurality of semiconductor piezoresistors; an electrode portion comprising a plurality of wires electrically connected to the plurality of electrodes; A chip mounting surface on which a semiconductor chip is mounted; a mounting surface located on the opposite side of the chip mounting surface and fixed to the object to be measured; and the semiconductor so that the back surface of the semiconductor chip faces the chip mounting surface. A plate member on which a chip is fixed via a bonding material, a resin substrate fixed in the same direction on a surface parallel to the chip mounting surface of the plate member via an adhesive material, the electrode portion, and an electrode portion of the resin substrate And the plate member includes a first region facing the back surface of the semiconductor chip, and a second region facing the back surface of the resin substrate, and the second member of the plate member. The thickness of the area is It was larger configuration than the thickness of the first region of the serial plate.

  ADVANTAGE OF THE INVENTION According to this invention, the distortion amount concerning the board | substrate adhere | attached on the strain body of the mechanical quantity measuring apparatus can be reduced, and the reliability of the electronic component and solder on a resin substrate can be improved.

1 is an enlarged plan view of a mechanical quantity measuring device including a strain generating body to which a resin substrate is bonded according to an embodiment of the present invention. It is an expanded sectional view along the AA line of FIG. It is a graph of the distortion amount of the upper surface 3a of the resin substrate 3 with respect to the thickness of the board | plate material side surface 1e. It is a graph of the thickness reduction of the board | plate material side surface 1e, and the distortion amount reduction rate of the upper surface 3a of the resin substrate 3 with respect to the mounting surface 1a of the board | plate material 1. It is an enlarged plan view of a mechanical quantity measuring device when electrodes of electronic components to be mounted are arranged in a strain direction to be measured. It is an enlarged plan view of the mechanical quantity measuring device when the electrodes of the electronic components to be mounted are arranged perpendicular to the strain direction to be measured. It is the top view which showed the electrode arrangement pattern of an electronic component

  In the following embodiments, the same or similar parts are denoted by the same or similar reference numerals or reference numerals, and the description of the same or similar parts will not be repeated in principle unless particularly necessary. Further, in the following embodiment, when it is necessary for the sake of convenience, the description will be divided into a plurality of sections or embodiments, but they are not irrelevant to each other unless otherwise specified. The other part or all of the modifications, details, supplementary explanations, and the like are related. Also, in the following embodiments, when referring to the number of elements (including the number, numerical value, quantity, range, etc.), particularly when clearly indicated and when clearly limited to a specific number in principle, etc. Except, it is not limited to the specific number, and it may be more or less than the specific number. In the following embodiments, it is needless to say that the constituent elements are not necessarily indispensable except for the case where they are clearly indicated and the case where they are clearly considered to be indispensable in principle. Further, in the following embodiments, regarding constituent elements and the like, when “consisting of A”, “consisting of A”, “having A”, and “including A” are specifically indicated that only those elements are included. It goes without saying that other elements are not excluded except in the case of such cases. Similarly, in the following embodiments, when referring to the shapes, positional relationships, etc. of the components, etc., the shapes are substantially the same unless otherwise specified, or otherwise apparent in principle. And the like are included. The same applies to the above numerical values and ranges.

  In the accompanying drawings, hatching or the like may be omitted even in a cross section when it becomes complicated or when the distinction from the gap is clear. In relation to this, when it is clear from the description etc., the contour line of the background may be omitted even if the hole is planarly closed. Furthermore, even if it is not a cross section, it may be hatched to clearly indicate that it is not a void.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments, and the repetitive description thereof will be omitted.

  A basic configuration of the mechanical quantity measuring apparatus according to the present embodiment will be described with reference to the drawings. In FIG. 1, in order to show the internal structure of the sealing body 8, the outline of the sealing body 8 is indicated by a two-dot chain line, and the internal structure that has passed through the sealing body 8 is illustrated.

  As shown in FIGS. 1 and 2, the mechanical quantity measuring device 12 according to the present embodiment is bonded to the structure 19 via the adhesive 18 on the mounting surface 1 a of the strain generating body 1, and the strain of the structure 19 is The amount is to be measured. The mechanical quantity measuring device 12 includes a semiconductor chip 2 which is a semiconductor strain sensor having a semiconductor piezoresistor inside, a plate material 1 on which the semiconductor chip 2 is mounted via a bonding material 14, and a seal for sealing the semiconductor chip 2. The body 8 is electrically connected to the plate member 1 via the adhesive 7 and is electrically connected via the semiconductor chip 2 and the wiring connection part 10 and the wire (conductive member) 11 mounted on the semiconductor chip 2. And a substrate 13 having a circuit portion. In the present embodiment, the bonding material for bonding the semiconductor chip 2 and the plate material 1 is a metal material. However, the present invention is not limited to the metal material, and there is no problem with a resin material or the like. Further, the substrate 13 is soldered to the resin substrate 3 bonded to the upper surface 1c of the plate member 1 via the adhesive 7, the printed line 15 printed on the resin substrate 3, and the plurality of electrodes 17 on the resin substrate 3. The electronic component 4 is connected to the electrical connection portion 16 via the connector. The plate material 1 is stainless steel having a Young's modulus of 197 GPa, and the resin substrate 3 is composed of a glass epoxy substrate having a Young's modulus of 20 GPa. The respective Young's moduli are not limited to the numerical values depending on the composition of each material except that the Young's modulus of the glass epoxy substrate is smaller than that of stainless steel.

  In the example shown in FIG. 2, the plate 1 includes a region 31 where the semiconductor chip 2 is mounted and a region 32 where the substrate 13 is mounted, and the upper surface 1 c of the region 32 is the upper surface of the region 32 where the semiconductor chip is mounted. It arrange | positions in the position away from the structure 19 rather than 1b. That is, the thickness of the side surface 1e of the plate 1 in the region 32 is larger than the thickness of the side 1d of the plate 1 in the region 31. On the other hand, the mounting surface 1 a of the plate 1 is flattened in both the regions 31 and 32 in order to maintain the adhesive strength with the structure 19. Thus, the effect obtained by making the area | region 32 thicker than the area | region 31 in the board | plate material 1 is mentioned later.

  As shown in FIGS. 1 and 2, a plurality of electrodes 9 to which a plurality of wires 11 electrically connected to a plurality of electrodes 10 of the semiconductor chip 2 are connected are arranged on the upper surface 3 a of the resin substrate 3 of the substrate 13. Is done. The wiring is performed using a wire bonding technique. In the wiring on the resin substrate 3, the electrode 9 on the resin substrate 3 is electrically connected to the electrode 17 and the solder 6 through the plurality of printed wirings 15, and is electrically connected to the electrode 16 of the electronic component 4. To do. The electronic component 4 is, for example, a connector that transmits data of the measured strain amount, a resistor, a capacitor, or the like, but is not particularly limited except that it is an electronic component having an electrical function that can be joined by solder. The wire 11 is, for example, a gold wire (Au wire) having a wire diameter of about 10 μm to 200 μm, and is sealed by the sealing body 8. By covering the wire 11 with the sealing body 8, a short circuit between the adjacent wires 11 can be prevented. The wiring on the substrate 13 and the electronic components only need to be able to convert electrical signals exchanged with the semiconductor chip 2 and transmit input / output current between the semiconductor chip 2 and an external device (not shown). It is not limited to the aspect shown in FIG.

  Next, the function of the mechanical quantity measuring device 12 will be described. The mechanical quantity measuring device 12 detects the strain of the structure 19 by bonding the mounting surface 1a to the plane of the structure 19 via the adhesive 18, and the strain is transmitted to the plate 1 via the adhesive 18. The strain is transmitted to the semiconductor chip 2 through the joint surface 1b and the joint material 14, and the strain transmitted to the semiconductor chip 2 is measured using the semiconductor piezoresistor in the semiconductor chip 2. For example, when a strain (tensile strain) is applied to the plate material in the direction of the arrow ST as shown in FIG. 1, the strain in the same direction is also generated on the bonding surface 1 b, the bonding material 14, and the semiconductor chip 2. Sensing strain in the same direction. At this time, the amount of strain transmitted to the semiconductor chip 2 through the plate material 1 and the bonding material 14 is alleviated by a certain amount. In addition, the amount of strain transmitted to the semiconductor chip 2 can be changed by changing the thickness of the plate 1, in FIG. 2, the size of the side surface 1 d, and thereby the dynamic range of the strain amount of the structure 19 to be measured. Can be changed.

  On the other hand, the strain applied to the plate 1 is simultaneously transmitted to the printed wiring 15 and the solder 6 via the upper surface 1 c, the adhesive 7, and the resin substrate 3. In particular, the solder 6 may be damaged by the strain applied to the solder 6. In order to solve this, the length of the side surface 1e of the plate material 1 is increased, and the region 32 portion of the plate material 1 is thickened. As a result, the strain transmitted from the structure 19 is relaxed inside the plate member 1, and the strain amount can be greatly reduced in the region 32 than in the region 31, that is, the strain applied to the upper surface 3 a of the resin substrate 3 can be reduced. At this time, the larger the thickness of the plate material 1, that is, the size of the side surface 1e, the larger the volume of the plate material 1 and the larger the amount of strain that is relieved inside, so the amount of reduction in strain applied to the upper surface 3a of the resin substrate 3 is large. Become. However, since the strain applied to the semiconductor chip 2 is set by the dynamic range of the measurement, the thickness of the plate 1 in the region 31, that is, the thickness of the side surface 1d cannot be easily changed. Therefore, it is necessary to prevent breakage of the solder 6 while maintaining the dynamic range of the strain amount applied to the semiconductor chip 2. Therefore, in the plate material 1, the side surface 1 e of the region 32 to which the substrate 13 is bonded is made thicker than the side surface 1 d of the region 31 to which the semiconductor chip 2 is bonded, so that the amount of strain transmitted to the semiconductor chip 2 is not changed. This amount of strain can be reduced.

  In FIG. 3, the material of the plate material 1 is stainless steel (Young's modulus 197 GPa), the resin substrate 3 is a glass epoxy substrate (Young's modulus 20 GPa), the side surface 1d is 0.5 mm, and the side surface 1e is 1.0 mm to 2.0 mm. The strain amount applied to the upper surface 3a of the resin substrate 3 at the same time when a strain of 2900 με occurs in the arrow ST direction on the mounting surface 1a of the plate material on which the substrate is mounted is shown by finite element analysis. FIG. 4 shows the strain amount reduction rate of the upper surface 3a with respect to the strain amount of the mounting surface 1a of the plate 1 at that time. As shown in FIG. 4, when a tensile strain is applied to the mounting surface 1a in the direction indicated by the arrow ST, it can be seen that the strain amount of the upper surface 3a with respect to the strain amount of the mounting surface 1a is reduced by 25%. Further, when the material is the same, and the side surface 1d is 0.5 mm and the side surface 1e is 2.0 mm, the strain amount of the upper surface 3a with respect to the strain amount of the mounting surface 1a is reduced by 53%. As described above, the amount of strain applied to the upper surface 3a, the solder 6 connected to the upper surface 3a, and the electronic component 4 can be reduced, and the reliability of the substrate 13 can be ensured.

  On the other hand, the thickness of the plate 1, that is, the side surface 1 e is not increased, but the side surface 3 b of the resin substrate 3 is also increased to reduce the strain applied to the upper surface 3 a, the solder 6 connected to the upper surface 3 a and the electronic component 4. It can be considered as one of the methods of reducing. In this case as well, when a finite element method analysis is performed on the amount of strain applied to the upper surface 3a of the resin substrate 3 when a strain of 2900 με is generated in the direction of the arrow ST on the mounting surface 1a of the plate material 1 as described above, When 1e is 1.0 mm and the side surface 3b of the resin substrate 3 is 0.1 mm, the maximum is 2160 με (reduction rate 25%), the side surface 1e is 0.5 mm, and the side surface 3b of the resin substrate 3 is 0.6 mm. In this case, the maximum is 2720 με (reduction rate 6%). For this reason, when the side surface of one of the members is thickened without changing the length of the side surface 3b and the side surface 1e, the side surface 1e of the plate 1 is thicker than the side surface 3b of the resin substrate 3 is thickened. It can be seen that the strain reduction effect is high.

  In this embodiment, a method for mounting the electronic component shown in FIGS. 5 and 6 will be described. In Example 1, as a method of reducing the amount of strain applied to the substrate 13, the amount of strain was reduced by increasing the thickness of the plate 1, that is, the size of the side surface 1e of the plate 1 in FIG. However, in FIGS. 5 and 6, the amount of strain applied to the electronic component itself varies depending on the mounting direction of the electronic component 4 and the electronic component 22.

  The reason why the amount of strain changes will be described with reference to FIG. In the electronic component 51, the electronic component 54, and the electronic component 57 as shown in FIG. 7, the electrode 53, the electrode 56, and the electrode 59 that are connected to the electronic component main body 52, the electronic component main body 55, and the electronic component main body 58 are indicated by an arrow X. They are lined up in the same direction. When mounting electronic components similar to these in such a manner that the arrow Y in FIG. 7 and the arrow ST in FIG. 5 are in the same direction, the arrow X in FIG. 7 and the arrow ST in FIG. Compared to the case where the electronic components are arranged so as to be in the same direction, there is a difference in whether the electrodes are aligned in the direction of strain in one electronic component and the electronic component main body is between the electrodes. 5 and 6, when the strain in the ST direction is sufficiently large in the plate material 1 and the influence of the rigidity of the electronic component or solder on the strain is sufficiently small, in one electronic component, the electrode and the electrode with respect to the strain direction When there is an electronic component body between the electrodes, that is, when the electronic component is arranged so that the arrow X in FIG. 7 and the arrow ST in FIG. 5 are in the same direction, the electronic component body is between the electrodes of one electronic component. In other words, as compared with the case where the electronic components are arranged so that the arrow Y in FIG. 7 and the arrow ST in FIG. 5 are in the same direction, distortion is also generated in the electronic components between the respective electrodes. The amount of strain applied to the electronic component body increases. On the other hand, when the electrodes are not arranged in only one direction as in the electronic component 60, the electronic component 63, and the electronic component 66 shown in FIG. Such strain is less dependent on direction. Accordingly, the electronic component 51 in FIG. 7 (corresponding to the electronic component 4 in FIG. 5 and the electronic component 22 in FIG. 6), the electronic component 54, and the electronic component 57 are arranged in one direction. When mounting the electronic component, the influence of the strain on the electronic component can be reduced by mounting the electronic component with the direction in which the electrodes are arranged perpendicular to the arrow ST in FIG. Therefore, the electronic component 4 in FIG. 5 is less affected by the amount of strain on the electronic component with respect to the strain in the ST direction than the electronic component 22 in FIG. 6, and the reliability is improved. The above description is not limited to optimizing the arrangement direction of the electronic component according to the direction of strain to be measured, not limited to one direction.

  Finally, the combination of Examples 1 and 2 will be described. In the first and second embodiments, the optimum shape can be selected by combining the features of the respective embodiments according to the external environment, required strength, and the like. How to select the feature is optimally matched according to required reliability, material characteristics, and the like.

DESCRIPTION OF SYMBOLS 1 Board | plate material 2 Semiconductor chip 3 Resin board | substrates 9 and 10 Electrode 11 Wire 15 Printed wiring 31 and 32 area | region

Claims (4)

A semiconductor chip comprising a plurality of semiconductor piezoresistors and a plurality of electrodes electrically connected to the plurality of semiconductor piezoresistors;
An electrode portion comprising a plurality of wires electrically connected to the plurality of electrodes;
A chip mounting surface on which the semiconductor chip is mounted;
A mounting surface located on the opposite side of the chip mounting surface and fixed to the object to be measured;
A plate material on which the semiconductor chip is fixed via a bonding material such that the back surface of the semiconductor chip faces the chip mounting surface;
A resin substrate fixed to the surface of the plate material parallel to the chip mounting surface in the same direction via an adhesive;
A wiring portion connecting the electrode portion and the electrode portion of the resin substrate,
The plate member includes a first region facing the back surface of the semiconductor chip, and a second region facing the back surface of the resin substrate,
The mechanical quantity measuring apparatus according to claim 1, wherein a thickness of the second region of the plate material is larger than a thickness of the first region of the plate material. The mechanical quantity measuring device according to claim 1,
The plate material is made of a metal material. The mechanical quantity measuring device according to claim 2,
The mechanical quantity measuring device measures strain applied along the mounting surface of the plate material. The mechanical quantity measuring device according to claim 1, wherein the resin substrate is mounted with an electronic component,
The electronic component has a plurality of electrodes arranged in one direction, and is arranged so that a direction in which the plurality of electrodes are arranged and a strain direction to be measured are perpendicular to each other.