Physical Quantity Sensor
20170018471 ยท 2017-01-19
Inventors
- Takanori AONO (Tokyo, JP)
- Tomonori Sekiguchi (Tokyo, JP)
- Takashi SHIOTA (Tokyo, JP)
- Yuudai KAMADA (Tokyo, JP)
- Atsushi ISOBE (Tokyo, JP)
Cpc classification
H01L23/49861
ELECTRICITY
G01L9/12
PHYSICS
H01L2224/16225
ELECTRICITY
B81B7/0048
PERFORMING OPERATIONS; TRANSPORTING
G01C19/5783
PHYSICS
G01L9/02
PHYSICS
International classification
H01L23/053
ELECTRICITY
G01L9/02
PHYSICS
H01L23/498
ELECTRICITY
Abstract
To provide a physical quantity sensor in which the influence of deformation of a package substrate on the measuring accuracy of a sensor element can be suppressed. A physical quantity sensor includes a sensor element that detects a predetermined physical quantity and outputs an electrical signal, a plurality of lead portions that are connected to the sensor element, and a package substrate that accommodates the sensor element and the plurality of lead portions. The plurality of lead portions are connected at proximal end sides thereof to the package substrate side, and connected at distal end sides thereof to the sensor element side, and the plurality of lead portions support the sensor element in such a manner that the sensor element does not contact the package substrate and that the transmission of deformation of the package substrate side to the sensor element is suppressed.
Claims
1. A physical quantity sensor that measures a physical quantity, comprising: a sensor element, that detects a predetermined physical quantity and outputs an electrical signal; a plurality of lead portions that are connected to the sensor element; and a package substrate that accommodates the sensor element and the plurality of lead portions, wherein the plurality of lead portions are connected at proximal end sides thereof to the package substrate side, and connected at distal end sides thereof to the sensor element side, and the plurality of lead portions support the sensor element in such a manner that the sensor element does not contact the package substrate and that the transmission of deformation of the package substrate side to the sensor element is suppressed.
2. The physical quantity sensor according to claim 1, wherein the package substrate has a hermetic structure, and a gas damper is formed in a gap between the sensor element and the package substrate due to a gas enclosed in the package substrate.
3. The physical quantity sensor according to claim 2, wherein the plurality of lead portions symmetrically support the sensor element.
4. The physical quantity sensor according to claim 3, wherein the sensor element, has a symmetrical shape, the plurality of lead portions are disposed at predetermined intervals on a peripheral edge side of the sensor element, and the plurality of lead portions uniformly support the sensor element.
5. The physical quantity sensor according to claim 4, wherein the plurality of lead portions are provided on a lead substrate, the sensor element is mounted on the lead substrate, and the plurality of lead portions support the sensor element via the lead substrate.
6. The physical quantity sensor according to claim 5, wherein a difference between a linear expansion coefficient of the lead substrate and a linear expansion coefficient of the sensor element is set to be small, or a predetermined board having a linear expansion coefficient similar to that of the sensor element is provided on one surface of both surfaces of the lead substrate, which is on the side opposite to the other surface on which the sensor element is mounted.
7. The physical quantity sensor according to claim 6, wherein the predetermined board is a board that processes an output signal from the sensor element.
8. The physical quantity sensor according to claim 7, wherein the plurality of lead portions are formed as a lead frame having a rigidity higher than that of a bonding wire.
9. The physical quantity sensor according to claim 8, wherein the plurality of lead portions include a plurality of first lead portions electrically and mechanically connected to the sensor element and a plurality of second lead portions mechanically connected to the sensor element.
10. The physical quantity sensor according to claim 9, wherein a distal end side of each of the first lead portions is provided in a predetermined region where a stress when a force is applied to the lead substrate is small in the lead substrate.
11. The physical quantity sensor according to claim 5, wherein the lead substrate is formed into a rectangular shape in a plan view, and the plurality of lead portions are disposed at predetermined intervals on four sides of the lead substrate.
Description
BRIEF DESCRIPTION OF DRAWINGS
[0020]
[0021]
[0022]
[0023]
[0024]
[0025]
[0026]
[0027]
DESCRIPTION OF EMBODIMENTS
[0028] Hereinafter, an embodiment of the invention will be described based on the drawings. In the embodiment, as will be described in detail below, the influence of a physical quantity (temperature, humidity, unwanted vibration) other than a measurement target on a physical quantity sensor chip 10 is suppressed. To this end, in the embodiment, the physical quantity sensor chip 10 as a sensor element is placed on a lead substrate 20 having a rectangular shape. Hereinafter, the physical quantity sensor chip 10 is sometimes abbreviated as the sensor chip 10.
[0029] Leads 22 as lead portions are disposed at predetermined intervals on each of four sides of the lead substrate 20. The lead substrate 20 is suspended in a package substrate 30 by means of the leads 33 extending from the four sides. The surface of the sensor chip 10 and the rear surface of the lead substrate 20 are slightly separated respectively from the inner surfaces of the package substrate 30, so that predetermined gaps are formed.
[0030] The sensor chip 10 and the lead substrate 20 are supported in a suspended state in the hollow package substrate 30, and are not in contact with the package substrate 30. For this reason, the influence of an impact or deformation applied to the package substrate 30 on the sensor chip 10 can be suppressed.
[0031] Further, the gap formed between the surface of the sensor chip 10 and the inner surface of the package substrate 30 and the gap formed between the rear surface of the lead substrate 20 and the inner surface of the package substrate 30 are used as so-called gas dampers, so that vibration transmitting from the package substrate 30 to the sensor chip 10 or the lead substrate 20 can be attenuated.
[0032] Further, the plurality of leads 22 are disposed at predetermined intervals on the four sides of the lead substrate 20 formed into a rectangular shape, which is a symmetrical shape, and therefore symmetrically support the lead substrate 20 and the sensor chip 10 from four directions. For this reason, in the embodiment, the transmission of twist or tilt caused in the package substrate 30 to the sensor chip 10 can be suppressed. In other words, in the embodiment, since vibration, twist, or tilt caused in the package substrate 30 can be absorbed by the plurality of leads 22, the influence of a physical quantity other than a measurement target is reduced, and S/N can be increased.
[0033] Further, a difference between the linear expansion coefficient of the sensor chip 10 and the linear expansion coefficient of the lead substrate 20 is set to be small, or a predetermined board 50 having a linear expansion coefficient similar to that of the sensor chip 10 may be provided on a surface of both surfaces of the lead substrate 20, which is on the side opposite to the surface on which the sensor chip 10 is mounted. The predetermined board 50 is, for example, an amplifier circuit board that amplifies a detection signal of the sensor chip 10. Due to this, the deformation of the lead substrate 20 due to thermal expansion can be suppressed. When the linear expansion coefficients of the sensor chip 10 and the lead substrate 20 are approximately equal to each other, the deformation of the lead substrate 20 can be suppressed even when temperature changes. When the linear expansion coefficients of the sensor chip 10 and the lead substrate 20 are different from each other, the predetermined board having a linear expansion coefficient similar to that of the sensor chip 10 is provided on the surface of both surfaces of the lead substrate 20, which is opposite to the mounting surface of the sensor chip 10. Due to this, even when a temperature change occurs, the thermal expansion of the sensor chip 10 caused on one surface of the lead substrate 20 and the thermal expansion of the predetermined board 50 caused on the other surface of the lead substrate 20 can be eventually cancelled out, and thus the deformation of the lead substrate 20 and the sensor chip 10 can be suppressed.
[0034] Further in the embodiment, since the leads 22 are formed as a lead frame having a rigidity higher than that of a bonding wire, the lead substrate 20 on which the sensor chip 10 is placed can be supported uniformly and firmly. Hereinafter, the embodiment will be described in detail.
EXAMPLE 1
[0035] A first example will be described using
[0036] The physical quantity sensor 1 is, for example, a device that detects a predetermined physical quantity (physical quantity as a measurement target) such as acceleration or angular velocity, and outputs a signal. The physical quantity sensor 1 is configured to include, for example, the sensor chip 10, the lead substrate 20, and the package substrate 30.
[0037] When a physical quantity as a measurement target is applied, a three-dimensional structure in the interior of the sensor chip 10 is deformed, and the sensor chip 10 outputs an electrical signal. The sensor chip 10 uses a change in capacitance or a change in resistance in response to the deformation of the three-dimensional structure to convert the deformation into an electrical signal. The sensor chip 10 is formed into a symmetrical shape. Examples of the symmetrical shape include, in a plan view, an oblong, a square, an isosceles triangle, a regular triangle, a circle, and an ellipse. A square or a circle is one of preferable shapes for the sensor chip 10. However, the sensor chip 10 is not limited to a square or a circle.
[0038] The lead substrate 20 is a substrate for electrically connecting the sensor chip 10 with the package substrate 30 to connect the sensor chip 10 to an external system outside the figure. The lead substrate 20 includes, for example, an electrode substrate 21, the leads 22, and connecting elements 23.
[0039] The electrode substrate 21 is formed into a symmetrical shape from a material having a linear expansion coefficient similar to that of the sensor chip 10. Examples of the symmetrical shape include, in the plan view, for example an oblong, a square, an isosceles triangle, a regular triangle, a circle, and an ellipse. A square or a circle is one of preferable shapes for the electrode substrate 21 of the lead substrate 20. However, the shape of the electrode substrate 21 is not limited to a square or a circle.
[0040] In the example, the sensor chip 10 and the electrode substrate 21 of the lead substrate 20 are both formed into the same symmetrical shape (a square herein). Then, equal numbers of the plurality of leads 22 are disposed at predetermined intervals on respective four sides constituting the peripheral edge of the electrode substrate 21. The leads 22 are formed as a lead frame having a rigidity higher than that of a bonding wire.
[0041] A proximal end side of each of the leads 22 is electrically connected to an electrode 33 of the package substrate 30 with solder or the like. A distal end side of each of the leads 22 is electrically connected via a wiring pattern (not shown) of the electrode substrate 21 to the sensor chip 10 with solder or the like. Note that the leads 22 are fixed to the electrode substrate 21 with solder or the like and thereby mechanically connected to the sensor chip 10. The leads 22 uniformly support the sensor chip 10 in a suspended manner in the package substrate 30, via the electrode substrate 21 of the lead substrate 20, from the four sides of the electrode substrate 21.
[0042] The connecting elements 23 for electrically connecting with an electric circuit in the sensor chip 10 are disposed at predetermined positions on the surface (upper surface in
[0043] The package substrate 30 has a hollow sealed structure to accommodate the sensor chip 10 and the lead substrate 20. The package substrate 30 is formed into a square (in the plan view) as a symmetrical shape, similarly to the sensor chip 10 and the lead substrate 20.
[0044] The package substrate 30 includes, for example, a lid portion 31 and a substrate portion 32. The electrodes 33 are disposed on the surface of the substrate portion 32 of the package substrate 30. The electrodes 33 are electrically connected to the external system outside the figure via other electrodes 34 shown in
[0045] An example of the manufacturing process of the physical quantity sensor 1 will be briefly described. Firstly, the sensor chip 10, the lead substrate 20, and the package substrate 30 are manufactured and prepared. Secondly, the sensor chip 10 is mounted on the lead substrate 20, and the sensor chip 10 and the lead substrate 20 are electrically and mechanically connected. Thirdly, the lead substrate 20 on which the sensor chip 10 is mounted is electrically and mechanically connected to the substrate portion 32 of the package substrate 30. Fourthly, the lid portion 31 is hermetically attached to the substrate portion 32 so as to cover the substrate portion 32. The package substrate 30 is hermetically sealed in a state where an inert gas or dry air is enclosed in the interior thereof.
[0046] Reference is made to
[0047] The lead substrate 20 on which the sensor chip 10 is mounted is supported in a suspended state in the package substrate 30 by the leads 22 extending from the four sides. Other portions except the proximal end sides of the leads 22 connected to the substrate portion 32 of the package substrate 30, that is, the sensor chip 10 and the electrode substrate 21, are supported by the leads 22 in such a state as to float in the air without contacting the package substrate 30.
[0048] A minute gap 1 is formed between the surface (upper surface in
[0049] According to the example configured as described above, even when the package substrate 30 is deformed due to a change in temperature or humidity, the leads 22 absorb the deformation through a slight deflection or the like. Therefore, the influence of deformation of the package substrate 30 on the sensor chip 10 can be suppressed. As a result of this, the physical quantity sensor of the example can improve measuring accuracy and reliability even when the physical quantity sensor is downsized or thinned.
[0050] According to the example, the lead substrate 20 on which the sensor chip 10 is mounted is supported in a suspended state in such a manner that the lead substrate 20 except the proximal end sides of the leads 22 is not contact with the package substrate 30, in the package substrate 30 with a hollow structure. Then, the gap 1 is formed between the sensor chip 10 and the lid portion 31 of the package substrate 30, and the gap 2 is formed between the lead substrate 20 and the substrate portion 32 of the package substrate 30. That is, in the example, the minute gaps 1 and 2 are formed respectively above and below a structure of the sensor chip 10 and the lead substrate 20, and the gaps 1 and 2 function as gas dampers. Therefore, in the example, when unwanted vibration is applied to the physical quantity sensor 1, the unwanted vibration can be reduced by damping effects of gases caused in the gaps 1 and 2. For this reason, the intensity of a signal for the sensor chip 10 to detect the unwanted vibration is made smaller than the intensity of a signal of a physical quantity as a measurement target, so that S/N can be increased.
[0051] In the example, even when a resonant frequency is applied to a three-dimensional structure in which the sensor chip 10 and the lead substrate 20 are weights and the leads 22 are springs, the transmission of vibration due to the resonant frequency to the sensor chip 10 can be suppressed by the gas damper effects of the gaps 1 and 2.
[0052] In the example, since the leads 22 extracted from the electrode substrate 21 of the lead substrate 20 are disposed in the directions of the four sides of the electrode substrate 21, the deformation of the lead substrate 20 when unwanted vibration is applied to the package substrate 30 can also be suppressed. Since the lead substrate 20 on which the sensor chip 10 is mounted is uniformly supported at the four sides by the leads 22 having a high rigidity, the rotation of the sensor chip 10 and the lead substrate 20 about the Z-axis in
EXAMPLE 2
[0053] A second example will be described with reference to
[0054] The physical quantity sensor 1A is configured to include the sensor chip 10, the lead substrate 20, a package substrate 30, and the amplifier circuit board 50. The amplifier circuit board 50, which is an example of the predetermined board that processes a signal from the sensor chip 10, amplifies a signal of the sensor chip 10 and outputs the signal. Hereinafter, the amplifier circuit board 50 is sometimes abbreviated as the circuit board 50.
[0055] The circuit board 50 is formed into a square or an oblong as a symmetrical shape. The circuit board 50 is accommodated in a circuit board accommodating portion 35 formed at the center of a substrate portion 32A of the package substrate 30A, and is electrically connected with electrodes 36 provided on the substrate portion 32A. The sensor chip 10 is connected from, for example, the leads 22 via the electrodes 33 of the package substrate 30 to a wiring pattern (not shown) in the substrate portion 32, and is connected from the wiring pattern via the electrodes 36 to the circuit board 50.
[0056] An example of the manufacturing process of the physical quantity sensor 1A will be described. Firstly, the sensor chip 10, the lead substrate 20, and the package substrate 30 are manufactured and prepared. Secondly, the sensor chip 10 is mounted on the lead substrate 20, and the sensor chip 10 and the lead substrate 20 are electrically and mechanically connected. Thirdly, the circuit board 50 is mounted on the accommodating portion 35 of the package substrate 30, and electrically connected with the electrodes 36. Fourthly, the lead substrate 20 on which the sensor chip 10 is mounted is electrically and mechanically connected to the substrate portion 32 of the package substrate 30. Fifthly, the lid portion 31 is hermetically attached to the substrate portion 32 so as to cover the substrate portion 32. The package substrate 30 is hermetically sealed in a state where an inert gas or dry air is enclosed in the interior thereof.
[0057] Also in the example, the minute gap 1 is formed between the upper surface of the sensor chip 10 and the lid portion 31 of the package substrate 30. Further, the minute gap 2 is also formed between the lower surface of the electrode substrate 21 of the lead substrate 20 and the substrate portion 32 of the package substrate 30. More specifically, in the example, since the circuit board 50 is accommodated in the accommodating portion 35 at the central portion of the substrate portion 32, the gap 2 is defined as a gap between the upper surface of the circuit board 50 or the upper surface of the substrate portion 32, whichever is a higher surface, and the lower surface of the electrode substrate 21 of the lead substrate 20. That is, the sensor chip 10 and the lead substrate 20 are also not in contact with the circuit board 50.
[0058] The example configured as described above also provides operational effects similar to those of the first example. Further, since the physical quantity sensor 1A of the example incorporates the circuit board 50 therein, a signal of the sensor chip 10 can be amplified and output to the external system, and thus convenience is improved. The circuit board 50 may include a circuit that exerts a function other than that of an amplifier circuit. For example, a waveform shaping circuit, a noise filtering circuit or the like may be included in the circuit board 50, or an analog/digital conversion circuit or the like may be included in the circuit board 50.
EXAMPLE 3
[0059] A third example will be described using
[0060] The physical quantity sensor 1B is configured to include the sensor chip 10, the lead substrate 20B, the package substrate 30, and the circuit board 50B. The leads 22B are bent obliquely downward and extracted, as shown in
[0061] When the electrode plate 21 is assumed as a reference horizontal plane, the lead 22B extends obliquely downward by an angle from the horizontal plane. A distal end side of the lead 22B is a flat portion connected to the electrode plate 21, and a proximal end side of the lead 22B is a flat portion connected to the electrode 33 of the package substrate 30.
[0062] The lead substrate 20B on which the sensor chip 10 is mounted is supported, by the leads 22B obliquely bent by the angle from the horizontal direction, in a suspended state in the package substrate 30 with a hollow structure. A gap 2B between the electrode substrate 21 of the lead substrate 20 and the substrate portion 32 of the package substrate 30 is larger than the gap 2 in the examples described above (2B>2) by an amount corresponding to the inclination of the leads 22B. The circuit board 50B is mounted at the central portion of the lower surface of the electrode plate 21 while being located in this expanded gap 2B.
[0063] The circuit board 50B, which is another example of the predetermined board, is formed into a square or an oblong as asymmetrical shape. The circuit board 50B may be an amplifier circuit board that amplifies a signal from the sensor chip 10, or may be a circuit board that realizes a function other than amplification. On the circuit board 50B, a plurality of electrodes 51 for electrically connecting with the lead substrate 20B are formed.
[0064] The circuit board 50B is located at substantially the central portion of the electrode plate 21 of the lead substrate 20, and fixed to the lower surface by soldering or the like. The circuit board 50B is formed so as to have a linear expansion coefficient approximately the same as that of the sensor chip 10. Due to this, even when a temperature change occurs in the physical quantity sensor 1B, a displacement due to the thermal expansion of the sensor chip 10 and a displacement due to the thermal expansion of the circuit board 50B are cancelled out by each other as viewed from the lead substrate 20. Therefore, the displacement amount of the lead substrate 20 can be reduced, and an influence due to a difference between the linear expansion coefficients on the sensor chip 10 can be suppressed. Note that if not only are the respective linear expansion coefficients of the sensor chip 10 and the circuit board 50B set approximately equal to each other, but also the linear expansion coefficient of the electrode substrate 21 of the lead substrate 20 is made approximately equal to the linear expansion coefficients, the influence due to thermal expansion can be still further reduced.
[0065] An example of the manufacturing process of the physical quantity sensor 1B will be described. Firstly, the sensor chip 10, the lead substrate 20B, and the package substrate 30 are manufactured and prepared. Secondly, the sensor chip 10 is mounted on the lead substrate 20B, and the sensor chip 10 and the lead substrate 20B are electrically and mechanically connected. Thirdly, the circuit board 50B is mounted on the lead substrate 20B, and the circuit board 50B and the lead substrate 20B and the sensor chip 10 are electrically connected via the electrodes 51. Fourthly, the lead substrate 20B on which the sensor chip 10 and the circuit board 50B are mounted is electrically and mechanically connected to the substrate portion 32 of the package substrate 30. Fifthly, the lid portion 31 is hermetically attached to the substrate portion 32 so as to cover the substrate portion 32. The package substrate 30 is hermetically sealed in a state where an inert gas or dry air is enclosed in the interior thereof.
[0066] The example configured as described above also provides operational effects similar to those of the first and second examples. Further in the example, since the circuit board 50B is mounted on the lead substrate 20B while being located on the side opposite to the sensor chip 10, a wiring pattern length between the circuit board 50B and the sensor chip 10 can be shortened. Therefore, the superimposition of noise on the signal of the sensor chip 10 can be suppressed, so that reliability and usability can be still further improved.
EXAMPLE 4
[0067] A fourth example will be described using
[0068] The leads 22 electrically connect the sensor chip 10 with the package substrate 30 as described above, and also mechanically connect the sensor chip 10 to the package substrate 30 via the electrode substrate 21.
[0069] In contrast to this, the dummy leads 22C only mechanically connect the sensor chip 10 to the package substrate 30 via the electrode substrate 21, so that the dummy leads 22C are not electrically connected to the sensor chip 10. That is, the dummy leads 22C function only as beams for support, and do not constitute an electric circuit.
[0070] Since an electrical signal flows through the normal lead 22, a distal end of the lead 22 is provided on the electrode plate 21 while being located in a predetermined region to which a stress due to a temperature change is hardly applied. The predetermined region is, for example, the central portion of each of the four sides of the electrode substrate 21. Since the displacement amount due to thermal expansion is less at the central portion of the electrode plate 21, a stress applied to the lead 22 can be made small. As a result of this, the superimposition of noise on the signal flowing through the lead 22 can be suppressed.
[0071] The example configured as described above also provides operational effects similar to those of the first example. The example can also be combined with any of the second and third examples. According to the example, the normal leads 22 are disposed in the region to which the stress is relatively hardly applied, while the dummy leads 22C through which a signal does not flow are disposed in a region to which the stress is relatively applied; and therefore, reliability can be still further improved.
EXAMPLE 5
[0072] A fifth example will be described using
[0073] A plurality of electrodes 11 are provided on the lower surface of the sensor chip 10D. The leads 37 corresponding to the electrodes 11 are bent obliquely upward and extracted from the substrate portion 32 of the package substrate 30D. A signal detected by the sensor chip 10D is sent to the external system via the electrodes 11, the leads 37, the electrodes 33, and the electrodes 34.
[0074] The gap 1 is formed between the upper surface of the sensor chip 10D and the lid portion 31 of the package substrate 30D. Also, a gap 1D is formed between the lower surface of the sensor chip 10D and the substrate portion 32 of the package substrate 30D.
[0075] The example configured as described above also provides operational effects similar to those of the first example. The example can be combined with any of the second, third, and fourth examples. In the example, since the lead substrate 20 is removed, the configuration of the physical quantity sensor 1D can be simplified, and thus the manufacturing cost can be reduced.
[0076] Note that the invention is not limited to the embodiment described above. Those skilled in the art can make various additions, modifications or the like within the scope of the invention. The features described in each of the examples can be used in appropriate combination with the configurations of the other examples. For example, the sensor chip and the lead substrate may be integrally formed.
REFERENCE SIGN LIST
[0077] 1, 1A, 1B, 1C, 1D: physical quantity sensor [0078] 10, 10D: sensor chip [0079] 20, 20B, 20C: lead substrate [0080] 22, 22B, 22C: lead [0081] 30, 30A, 30D: package substrate [0082] 37: lead [0083] 50, 50B: circuit board