JP2009294152A - Capacity sensor package - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a capacity sensor package capable of detecting accurately a physical quantity, even if subjected to packaging by resin. <P>SOLUTION: This capacity sensor package is equipped with a wiring board 11, having a pair of main surfaces and an air hole 11a; a capacity sensor 12, mounted on one main surface of the wiring board 11 and having a diaphragm 12a and a fixed electrode, for detecting a physical quantity from a change of a capacitance between the diaphragm 12a and the fixed electrode; and a sealing member 17 for sealing the capacity sensor 12 without blocking the air hole 11a on one main surface 11b of the wiring board 11. The capacity sensor 12 is mounted at a position where the diaphragm 12a can be moved by the outside air which has been introduced via the air hole 11a. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a package of a capacitance sensor that detects a physical quantity such as pressure by using a capacitance.

  As a sensor for detecting a physical quantity such as pressure, there is a capacity sensor, for example. This capacitance sensor is composed of a fixed electrode and a movable electrode such as a diaphragm, and a physical quantity can be obtained by detecting a change in capacitance between the fixed electrode and the movable electrode.

Such a capacitive sensor has come to be mounted on an electronic device such as a mobile phone or a PDA (Personal Digital Assistance), and is packaged as an electronic element. An example of a packaged capacitive sensor is disclosed in Patent Document 1. As shown in FIG. 6, the capacitive sensor package includes a capacitive sensor 62 mounted on a substrate 61, and a region other than the diaphragm 62 a that is a movable electrode of the capacitive sensor 62 is molded with a resin 63. .
Registered Utility Model No. 3128158

  However, in the capacitive sensor package shown in FIG. 6, the resin 63 is coated in a region other than the diaphragm 62a of the capacitive sensor 62. However, if alignment misalignment or the like occurs during resin sealing, the resin 63 is applied to the diaphragm 62a. As a result, the diaphragm 62a cannot move normally, and the physical quantity cannot be detected accurately. Further, in the configuration shown in FIG. 6, the diaphragm 62a is very thin, so that there is a problem that the mechanical strength cannot be obtained.

  The present invention has been made in view of this point, and an object of the present invention is to provide a capacitive sensor package capable of accurately detecting a physical quantity even when packaging is performed with a resin.

  The capacitive sensor package of the present invention is mounted on a wiring board having a pair of main surfaces and vent holes, and on one main surface of the wiring board, and has a movable electrode and a fixed electrode. A capacitance sensor that detects a physical quantity from a change in capacitance with the fixed electrode; and a sealing member that seals the capacitance sensor without closing the vent hole on the one main surface of the wiring board; The capacitance sensor is mounted at a position where the movable electrode is movable by outside air introduced through the vent hole.

  According to this configuration, since the capacitive sensor is mounted on the wiring board having the vent holes with the movable electrode facing down and the fixed electrode facing up, even if the capacitive sensor is covered with the sealing member, The sealing resin constituting the sealing member contacts the third silicon layer but does not contact the movable electrode region. For this reason, there is no influence of the sealing resin on the movable electrode, and when the capacitive sensor is sealed with the sealing resin as in the prior art, the sealing resin flows out to the movable electrode, and therefore it is accurate. Therefore, the physical quantity cannot be detected in a short time, and the physical quantity can be accurately detected.

  In the capacitive sensor package of the present invention, the capacitive sensor includes a first silicon layer constituting the movable electrode, a second silicon layer mounted on one main surface of the wiring board, and the first silicon layer. And an insulating layer having a constant thickness interposed between the second silicon layers.

  According to this configuration, since the insulating layer functions as an etching stopper for the second silicon layer, the first silicon layer is not etched when the second silicon layer is etched, and the thickness of the first silicon layer is reduced. It can be ensured accurately over the entire movable electrode region. This makes it possible to accurately detect the physical quantity.

  In the capacitive sensor package of the present invention, it is preferable that the second silicon layer has a thickness sufficient to absorb expansion / contraction due to a temperature change of the wiring board.

  In the capacitive sensor package of the present invention, the capacitive sensor includes a third silicon layer constituting the fixed electrode, a first silicon layer constituting the movable electrode, the first silicon layer, the third silicon layer, And a cavity region surrounded by a thermal oxide film having a thickness corresponding to the gap between the movable electrode and the fixed electrode.

  In this configuration, the thickness of the thermal oxide film on the silicon substrate corresponds to the gap between the movable electrode and the fixed electrode. The gap between the movable electrode and the fixed electrode greatly affects the sensor sensitivity. Since the thickness of the thermal oxide film of the silicon substrate can be controlled in units of 1 nm, by adopting such a configuration, the accuracy of the gap between the movable electrode and the fixed electrode can be improved. As a result, the detection accuracy of the sensor can be increased.

  The capacitive sensor package of the present invention is mounted on a wiring board having a pair of main surfaces and vent holes, and on one main surface of the wiring board, and has a movable electrode and a fixed electrode. A capacitance sensor that detects a physical quantity from a change in capacitance with the fixed electrode; and a sealing member that seals the capacitance sensor without closing the vent hole on the one main surface of the wiring board; The capacitive sensor is mounted at a position where the movable electrode is movable by the outside air introduced through the vent hole, so that the physical quantity can be accurately detected even if packaging is performed with resin. Can do.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
1A and 1B are diagrams showing a capacitive sensor package according to an embodiment of the present invention. FIG. 1A is a cross-sectional view, and FIG. 1B is a plan view. The capacitive sensor package shown in FIG. 1 has a wiring board 11. Examples of the wiring board 11 include a printed wiring board made of glass epoxy or ceramics. The wiring board 11 is provided with a vent hole 11a for allowing outside air to pass therethrough. The size of the vent hole 11a is not particularly limited as long as it depends on the size of the capacitance sensor, but the size of the capacitance sensor, which will be described later, can pass a sufficient amount of outside air to detect the physical quantity. On one main surface 11b of the pair of main surfaces of the wiring board 11, a conductive land 13 is provided for electrical connection with the electrode of the capacitance sensor.

  A capacitance sensor 12 that has a movable electrode and a fixed electrode on one main surface 11 b of the wiring substrate 11 and detects a physical quantity from a change in capacitance between the movable electrode and the fixed electrode is formed by a die bond material 14. It is die-bonded (mounted).

  The capacitance sensor 12 includes a first silicon layer 12b that constitutes a diaphragm 12a that is a movable electrode, a second silicon layer 12c that is mounted on one main surface of the wiring substrate 11, and a first silicon layer 12b and a second silicon layer. An SOI (Silicon On Insulator) substrate composed of an insulating layer 12d having a certain thickness interposed between the first and second silicon layers 12c, a third silicon layer 12e constituting a fixed electrode, and the first silicon layer 12b and the third silicon layer 12e; The thermal oxide film 12f is provided on the third silicon layer 12e so as to be positioned between the thermal oxide film 12f and has a thickness corresponding to the gap between the diaphragm 12a and the fixed electrode (third silicon layer 12e). And a silicon substrate.

  In the capacitance sensor 12, one surface of the second silicon layer 12c of the SOI substrate is mounted on the wiring substrate 11 via the die bonding material 14, and has an opening in a region corresponding to the diaphragm 12a. The outside air from the 11 ventilation holes 11a is allowed to pass through the opening. The second silicon layer 12c preferably has a thickness sufficient to absorb expansion / contraction due to a temperature change of the wiring substrate 11. For example, when the wiring board 11 is made of glass epoxy, the second silicon layer 12c preferably has a thickness of 200 μm to 500 μm.

  In the capacitance sensor 12, a first silicon layer 12b is provided on the other surface of the second silicon layer 12c via an insulating layer 12d. The peripheral portion of the first silicon layer 12b is provided on the second silicon layer 12c via the insulating layer 12d, and the central portion is not supported at all and is movable. This movable region functions as the diaphragm 12a. Therefore, the diaphragm 12a is in a state in which the outside air is in direct contact via the vent hole 11a of the wiring substrate 11 and the opening of the second silicon layer 12c, and can be displaced by the outside air. The thickness of the first silicon layer 12b is preferably 10 μm to 50 μm, and the thickness of the insulating layer 12d is preferably 1.0 μm to 2.0 μm.

  Since the diaphragm 12a is formed by processing an SOI substrate, that is, the insulating layer 12d functions as an etching stopper for the second silicon layer 12c, the first silicon layer 12b is etched when the second silicon layer 12c is etched. Is not etched, and the thickness of the first silicon layer 12b can be accurately ensured over the entire area of the diaphragm 12a. This makes it possible to accurately detect the physical quantity.

  Also, a thermal oxide film 12f on the surface of the third silicon layer (silicon substrate) 12e is bonded onto the first silicon layer 12b (surface opposite to the insulating layer 12d) of the SOI substrate. The third silicon layer 12e constitutes a fixed electrode. A cavity region 18 is a region surrounded by the first silicon layer 12b, the third silicon layer 12e, and the thermal oxide film 12f having a thickness corresponding to the gap between the movable electrode and the fixed electrode. In addition, an electrode 15a on the movable electrode side is formed on the first silicon layer 12b. The electrode 15a and the land 13 are electrically connected by wire bonding using a wire 16. Furthermore, an electrode 15b on the fixed electrode side is formed on the third silicon layer 12e (surface opposite to the thermal oxide film 12f). The electrode 15 b and the land 13 are electrically connected by wire bonding using the wire 16. In addition, as a material of the electrodes 15a and 15b, normal electrode materials, such as aluminum and gold | metal | money, can be used.

  The thickness of the thermal oxide film 12f on the silicon substrate corresponds to the gap between the diaphragm 12a as the movable electrode and the third silicon layer 12e as the fixed electrode. The gap between the movable electrode and the fixed electrode greatly affects the sensor sensitivity. Since the thickness of the thermal oxide film 12f on the silicon substrate can be controlled in units of 1 nm, by adopting such a configuration, the accuracy of the gap between the movable electrode and the fixed electrode can be improved. As a result, the detection accuracy of the sensor can be increased. Note that the thickness of the third silicon layer 12e is preferably 150 μm to 500 μm, and the thickness of the thermal oxide film 12f is preferably 0.5 μm to 1.5 μm.

  On one main surface 11 a of the wiring substrate 11, the capacitance sensor 12 is sealed with a sealing member 17 so as not to close the vent hole 11 a. As a material of the sealing member 17, an epoxy resin, which is a normal sealing material, can be used.

  In the capacitive sensor package having such a configuration, when a physical quantity, for example, pressure is detected, when pressure is applied to the capacitive sensor package, outside air presses the diaphragm 12a through the vent hole 11a of the wiring board 11. When the diaphragm 12a is pressed, the diaphragm 12a is displaced to change the distance from the third silicon layer 12e, and a change in capacitance due to the change in the distance can be detected as a capacitance difference. The pressure can be measured by change.

  In the capacitive sensor package having the configuration shown in FIG. 1, the capacitive sensor 12 is mounted at a position where the diaphragm 12 a which is a movable electrode is movable by outside air introduced through the vent hole 11 a of the wiring board 11. That is, since the capacitance sensor is mounted on the wiring substrate 11 having the vent hole 11a with the diaphragm 12a (movable electrode) facing down and the third silicon layer 12e (fixed electrode) facing up, the capacitance sensor 12 Even if it covers with the sealing member 17, the sealing resin which comprises the sealing member 17 contacts the 3rd silicon layer 12e, but does not contact the diaphragm 12a area | region. For this reason, there is no influence of the sealing resin on the diaphragm 12a, and when the capacitive sensor is sealed with the sealing resin as in the prior art, the sealing resin flows out to the diaphragm 12a, and therefore the accuracy is increased. Therefore, the physical quantity cannot be detected in a short time, and the physical quantity can be accurately detected. Moreover, according to this structure, since resin sealing can be used, packaging can be achieved at low cost.

  Next, an example of a manufacturing method of the capacitive sensor package having the above configuration will be described. 2 (a)-(c), FIGS. 3 (a), 3 (b), 4 (a), 4 (b) and 5 (a)-(c) show the manufacture of a capacitive sensor package according to the present invention. It is a figure for demonstrating a method.

  As shown in FIG. 2A, the movable electrode 15a is formed on the first silicon layer 12b of the SOI substrate having the first silicon layer 12b on the second silicon layer 12c via the insulating layer 12d. That is, an electrode material is deposited on the second silicon layer 12c by sputtering, and the electrode 15a is formed by photolithography and etching.

  Next, as shown in FIG. 2B, the second silicon layer 12 c is anisotropically etched to form an opening 21 that communicates with the vent hole 11 a of the wiring substrate 11. At this time, since the insulating layer 12d serves as an etching stopper for the second silicon layer 12c, the first silicon layer 12b is not etched. Next, as shown in FIG. 2C, the insulating layer 12d is isotropically etched to remove the insulating layer 12d in the opening 21 to form a diaphragm 12a.

  Next, one main surface of the silicon substrate (third silicon layer 12e) is thermally oxidized to form a thermal oxide film 12f, and as shown in FIG. 3A, on the other main surface of the third silicon layer 12e. An electrode 15b for a fixed electrode is formed on the substrate. That is, an electrode material is deposited on the other main surface of the third silicon layer 12e by sputtering, and the electrode 15b is formed by photolithography and etching. Next, as shown in FIG. 3B, the thermal oxide film 12f is isotropically etched to remove the thermal oxide film 12f so that the thermal oxide film 12f remains in a region other than the region corresponding to the diaphragm 12a.

  Next, as shown in FIG. 4A, the SOI substrate and the silicon substrate are bonded so that the thermal oxide film 12f is in contact with the first silicon layer 12b. As a bonding method, a normal substrate bonding method such as a plasma activation method or a room temperature method can be used. Note that the SOI substrate and the silicon substrate are preferably bonded on a wafer scale. Next, as shown in FIG. 4B, the third silicon layer 12e is removed by anisotropic etching so that the electrode 15a for the movable electrode is exposed. In this way, a capacitive sensor is produced.

  Next, as shown in FIG. 5 (a), the capacitive sensor 12 is placed on the wiring board 11 provided with the vent holes 11a in advance at a position where the diaphragm 12a can be moved by the outside air introduced through the vent holes 11a. The electrodes 15a and 15b and the land 13 are wire-bonded by the wire 16 to electrically connect the wiring board 11 and the capacitance sensor 12. Next, as shown in FIG. 5B, the capacitance sensor 12 is sealed on the wiring board 11 with the sealing member 17 without closing the vent hole 11 a. At this time, the sealing resin constituting the sealing member 17 contacts the third silicon layer 12e, but does not contact the diaphragm 12a region. Finally, as shown in FIG. 5C, the wiring board 11 is diced into chips. In the state of FIG. 5B, another electronic element such as RFID may be mounted in the region between the sealing members 17.

  The present invention is not limited to the above embodiment, and can be implemented with various modifications. In the above-described embodiment, the thickness and material of the electrode and each layer in the sensor can be set as appropriate without departing from the effects of the present invention. Further, the process described in the above embodiment is not limited to this, and the process may be performed by changing the order as appropriate. Other modifications may be made as appropriate without departing from the scope of the object of the present invention.

It is a figure which shows the capacitive sensor package which concerns on embodiment of this invention, (a) is sectional drawing, (b) is a top view. (A)-(c) is a figure for demonstrating the manufacturing method of the capacitive sensor package which concerns on this invention. (A), (b) is a figure for demonstrating the manufacturing method of the capacitive sensor package based on this invention. (A), (b) is a figure for demonstrating the manufacturing method of the capacitive sensor package based on this invention. (A)-(c) is a figure for demonstrating the manufacturing method of the capacitive sensor package which concerns on this invention. It is a figure which shows the conventional capacitive sensor package.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Wiring board 11a Vent hole 11b Main surface 12 Capacitance sensor 12a Diaphragm 12b 1st silicon layer 12c 2nd silicon layer 12d Insulating layer 12e 3rd silicon layer 12f Thermal oxide film 13 Land 14 Die-bonding material 15a, 15b Electrode 16 Wire 17 Sealing Member 18 Cavity region 21 Opening

Claims (4)

  A wiring board having a pair of main surfaces and vent holes, and mounted on one main surface of the wiring board, having a movable electrode and a fixed electrode, and an electrostatic capacitance between the movable electrode and the fixed electrode A capacitance sensor that detects a physical quantity from a change in capacitance; and a sealing member that seals the capacitance sensor without closing the vent hole on the one main surface of the wiring board. Is mounted at a position where the movable electrode is movable by outside air introduced through the vent hole.   The capacitance sensor includes a first silicon layer constituting the movable electrode, a second silicon layer mounted on one main surface of the wiring board, and the first silicon layer and the second silicon layer. 2. The capacitive sensor package according to claim 1, further comprising an insulating layer having a constant thickness interposed therebetween.   3. The capacitive sensor package according to claim 2, wherein the second silicon layer has a thickness sufficient to absorb expansion and contraction due to temperature change of the wiring board.   The capacitance sensor includes a third silicon layer that constitutes the fixed electrode, a first silicon layer that constitutes the movable electrode, the first silicon layer, the third silicon layer, and the movable electrode and the fixed electrode. 4. The capacitive sensor package according to claim 1, further comprising: a cavity region surrounded by a thermal oxide film having a thickness corresponding to a gap between the two.

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