JP2016217793A - Pressure sensor - Google Patents

Abstract

A pressure sensor capable of reducing a force acting on a control unit enclosed in a package (support) of a mold resin is provided. A pressure sensor chip 2 provided on one surface side of a pedestal portion 4a of a lead frame 4 and a control unit 3 provided on the other surface side of the pedestal portion 4a of the lead frame 4 are provided. A pressure sensor is provided. The control unit 3 is surrounded by a stress relaxation layer 17 made of a resin M1 having a low Young's modulus, and the support (package) 5 is molded thereon, thereby enclosing the control unit 3 inside the support 5. A gap 18 is formed between the stress relaxation layer 17 c that covers the outer surface 3 a of the control unit 3 and the support 5. [Selection] Figure 1

Description

  The present invention relates to a pressure sensor.

Conventionally, small pressure sensors using MEMS (Micro Electro-Mechanical Systems) technology have been used for portable devices and the like (see, for example, Patent Documents 1 to 3).
Examples of the pressure sensor include a pressure sensor chip and a control unit (control IC) that receives a sensor signal from the pressure sensor chip and outputs a pressure detection signal. Generally, the control unit is enclosed in a mold resin package (support) together with a lead frame.

Japanese Patent No. 3620185 JP 2000-329632 A Japanese Patent No. 5351943

However, in the pressure sensor, when the mold resin swells due to moisture absorption, the generated stress may adversely affect the control unit and an output error may occur.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a pressure sensor that can reduce the force acting on a control unit enclosed in a mold resin package and prevent an output error. And

The present invention provides a base portion having a lead frame and a resin support for supporting the lead frame, a pressure sensor chip provided on one surface side of the lead frame, and provided on the other surface side of the lead frame. A control unit that receives a sensor signal from the pressure sensor chip and outputs a pressure detection signal, and the control unit is a stress relaxation layer made of a resin having a Young's modulus lower than that of the resin constituting the support. In such a state that at least the bottom surface on the lead frame side and the outer surface opposite to the lead frame are covered, the support body is molded on top of the support body, and the stress is sealed inside the support body. Provided is a pressure sensor in which a gap is formed between the stress relaxation layer on the outer surface side that covers the outer surface of the control unit and the support among the relaxation layer.
In the pressure sensor according to the present invention, the thermal expansion coefficient of the resin constituting the stress relaxation layer is larger than the thermal expansion coefficient of the resin constituting the support, and thus after the annealing treatment performed after molding of the support. It is preferable that the gap is formed by a difference in shrinkage between the resin constituting the stress relaxation layer and the resin constituting the support during cooling.
The control unit preferably includes a temperature sensor.
The control unit is electrically connected to the lead frame by a bonding wire, and at least a part of the bonding wire passes through the stress relaxation layer from the control unit, passes through the gap, and passes through the support. It is preferable that the lead frame is reached.
It is preferable that a gas vent hole communicating with the gap is formed in the support.

According to the present invention, since a gap is formed between the support molded from the mold resin and the stress relaxation layer on the outer surface side of the control unit, the control unit is affected by swelling due to moisture absorption of the mold resin. Can be suppressed. Therefore, it is possible to increase the thickness of the stress relaxation layer on the bottom surface side (lead frame side) of the control unit without increasing the overall thickness of the stress relaxation layer.
Therefore, not only the force that acts on the control unit from the support side but also the force that acts on the control unit from the lead frame side can be suppressed, and an output error can be prevented.

(A) It is a sectional side view of the pressure sensor which concerns on one Embodiment of this invention. (B) It is an enlarged view of the pressure sensor shown to (A). It is a photograph which shows the example of the pressure sensor in which the clearance gap was formed between the stress relaxation layer and the support body. It is a characteristic view which shows the difference of the stress which acts on a control part when there is a clearance gap between a stress relaxation layer and a support body with respect to the thickness of the stress relaxation layer of the bottom face side of a control part. It is a sectional side view of an example of a pressure sensor. It is a sectional side view of the other example of a pressure sensor. It is a sectional side view which shows the modification of the pressure sensor of embodiment.

Hereinafter, based on a preferred embodiment, the present invention will be described with reference to the drawings.
FIG. 1A is a side sectional view of a pressure sensor according to an embodiment of the present invention. FIG. 1B is an enlarged view of the pressure sensor of the embodiment.
In the following description, “upper” and “lower” correspond to the upper and lower in FIG. 1, respectively.

  As shown in FIG. 1, the pressure sensor includes a base unit 1, a pressure sensor chip 2 (pressure sensor element) provided on the base unit 1, a control unit 3 (control element) built in the base unit 1, It has.

The base portion 1 includes a lead frame 4 made of a conductor such as metal, and a resin support 5 (resin package) that supports the lead frame 4. The support 5 is formed integrally with the lead frame 4 by, for example, molding using an epoxy resin or the like.
The support 5 has a base part (main body part) 7 provided with a placement part 6 on which the pressure sensor chip 2 is placed, and a cylindrical annular wall part 8 projecting thereon.

  The annular wall portion 8 has, for example, a cylindrical shape or a polygonal cylindrical shape, and a space inside the annular wall portion 8 is a housing portion 10 that houses the pressure sensor chip 2 and the protective agent 9.

  The upper end of the annular wall portion 8 is preferably located at a position higher than the upper surface 2a of the pressure sensor chip 2 mounted and fixed on the mounting portion 6. Thereby, sufficient depth can be given to the accommodating part 10, the whole pressure sensor chip 2 can be covered with the protective agent 9, and it can prevent that external force reaches the pressure sensor chip 2. FIG.

  The lead frame 4 includes a pedestal portion 4a embedded under the mounting portion 6 of the molded support body 5 and lead portions 4b and 4c disposed around the pedestal portion 4a. The lead portion 4b and the pressure sensor chip 2 are electrically connected via a bonding wire 13. A part of the lead portion 4 c is an external terminal portion 4 d exposed to the outside of the support body 5.

A stress relaxation layer 17 made of a resin M1 different from the mold resin M2 constituting the support 5 is provided on the lower surface of the pedestal portion 4a, and the control unit 3 is arranged in the stress relaxation layer 17. .
The stress relaxation layer 17 includes a bottom surface side stress relaxation layer 17 a between the lower surface of the pedestal portion 4 a of the lead frame 4 and the bottom surface 3 b of the control unit 3 (upper surface in FIG. 1), and a side surface that covers the side surface of the control unit 3. And a stress relaxation layer 17c on the outer surface side that covers the outer surface 3a (the lower surface in FIG. 1; the surface opposite to the bottom surface 3b) of the control unit 3. The entire surface of the control unit 3 is covered with the resin M1 by the stress relaxation layer 17.

  For example, the support 5 made of the mold resin M2 is molded by using a mold after the stress relaxation layer 17 and the control unit 3 are disposed below the pedestal 4a of the lead frame 4. It is formed. Thereby, the control part 3 is enclosed in the base 7 of the support body 5 in the state surrounded by the stress relaxation layer 17. Thus, since all the outer surfaces of the control part 3 are covered, external air and a water | moisture content can be interrupted | blocked and the control part 3 can be protected.

A small gap 18 is formed between the outer surface of the stress relaxation layer 17 that covers the control unit 3 and the base 7 of the support 5 in the stress relaxation layer 17. The gap 18 (the gap C1 in FIG. 1B) is, for example, 1 μm to 30 μm. By setting the gap C1 within this range, the stress acting on the control unit 3 can be reduced without increasing the overall thickness of the stress relaxation layer 17.
As will be described later, the gap 18 is formed by a difference in contraction rate between the resin M1 constituting the stress relaxation layer 17 and the resin M2 constituting the support 5 during cooling after the annealing treatment performed after molding of the support 5. Is done.

As the resin M1 constituting the stress relaxation layer 17, a material having a Young's modulus lower than the Young's modulus of the resin M2 constituting the support 5 and the lead frame 4 (low Young's modulus material) is selected. As the low Young's modulus material, a thermosetting resin, an ultraviolet curable resin, or the like can be used.
Specifically, for example, a silicone resin, an epoxy resin, a urethane resin, a polyimide resin, or the like can be used. One of these may be used as the low Young's modulus material, or two or more may be used in combination. In particular, a silicone resin is preferable because it is difficult to absorb moisture, and the physical properties hardly change even in a high temperature and high humidity environment.

  The Young's modulus of the stress relaxation layer 17 is preferably, for example, 1 MPa or more and 500 MPa or less (preferably 1 MPa or more and 100 MPa or less). The Young's modulus of the stress relaxation layer 17 is preferably 1/10 or less (preferably 1/100 or less) with respect to the Young's modulus of the constituent material of the support 5. The Young's modulus can be measured by a method based on JIS K 7161 or JIS K 7244.

As the resin M1 constituting the stress relaxation layer 17, one having a thermal expansion coefficient larger than that of the mold resin M2 constituting the support 5 is used. Specifically, a silicone resin having a low Young's modulus, etc., having a thermal expansion coefficient of 200 ppm / ° C. or higher is preferable.
As the mold resin M2 constituting the support 5, it is desirable to use an epoxy resin or the like filled with a glass filler and having a thermal expansion coefficient of 100 ppm / ° C. or less. In addition, a thermal expansion coefficient can be calculated | required by the method of JISK6911: thermosetting plastic general test method description.

Due to the difference in thermal expansion coefficient between the resin M1 constituting the stress relaxation layer 17 and the mold resin M2 constituting the support 5, the gap 18 is formed for the following reason.
When an annealing process (temperature condition is, for example, 180 ° C.) for curing the mold resin M2, the thermal expansion coefficient of the mold resin M2 is fixed. Thereafter, the resin M1 and the mold resin M2 are cooled to room temperature. At this time, due to the difference in thermal expansion coefficient between the resin M1 and the mold resin M2, the volume deformation amount when the resin M1 contracts becomes larger than the volume deformation amount when the mold resin M2 contracts. Thereby, a gap 18 is formed between the stress relaxation layer 17 and the support 5.

  The thickness of the stress relaxation layer 17a on the bottom surface side of the control unit 3 can be, for example, 5 μm or more and 100 μm or less (preferably 10 μm or more and 50 μm or less). By setting the thickness to 5 μm or more, a high stress relaxation effect can be obtained. Moreover, the whole thickness dimension can be suppressed by making this thickness into 100 micrometers or less.

  The thickness (average thickness) of the stress relaxation layer 17c on the outer surface side of the control unit 3 is preferably, for example, 5 μm or more and 400 μm or less (preferably 100 μm or more and 400 μm or less). By setting the thickness to 5 μm or more, a high stress relaxation effect can be obtained. Moreover, the whole thickness dimension can be suppressed because this thickness shall be 400 micrometers or less.

  The outer surface of the stress relaxation layer 17c on the outer surface side of the control unit 3 (the boundary surface with the base 7 of the support 5) is preferably a curved convex surface. The entire outer surface of the stress relaxation layer 17c may be a curved convex surface, or only a part may be a curved convex surface. Further, the cross-sectional shape of the curved convex surface may be, for example, an arc shape, or may be an elliptical arc shape, a parabolic shape, a hyperbolic shape such as a hyperbolic shape (for example, a quadratic curve shape).

  When the outer surface of the stress relaxation layer 17c on the outer surface side of the control unit 3 is a curved convex surface, the stress relaxation layer 17c is thickest at the central portion and thinner as it is closer to the periphery. When the outer surface is a curved convex surface, stress concentration is less likely to occur. Therefore, the effect of suppressing the influence of deformation of the base 7 and the like on the control unit 3 is enhanced, and errors in the output of the temperature sensor are less likely to occur. Can do. In addition, by making the outer surface a curved convex surface, the resin flow in the mold becomes smooth when the mold 7 is filled with resin and the base 7 of the support 5 is molded.

As the pressure sensor chip 2, for example, a diaphragm portion, a sealed space as a reference pressure chamber, and a plurality of strains for measuring a change in strain resistance of the diaphragm portion due to pressure are formed on one surface side of a semiconductor substrate made of silicon or the like. Those equipped with gauges can be used.
In the pressure sensor chip 2 of this example, when the diaphragm portion is bent under pressure, a stress corresponding to the strain amount of the diaphragm portion is generated in each strain gauge, and the resistance value of the strain gauge changes according to this stress, A sensor signal corresponding to the change in resistance value is output.
The pressure sensor chip 2 is a pressure sensor element using, for example, MEMS (MicroElectro-Mechanical Systems) technology. As the pressure sensor chip, a piezoresistive pressure sensor using a piezoresistive effect or a capacitive pressure sensor may be used.
The pressure sensor chip 2 can be provided on the upper surface of the placement unit 6 in the housing unit 10. The pressure sensor chip 2 is embedded in the protective agent 9 filled in the housing part 10.

The protective agent 9 can prevent water and outside air from entering, and can prevent adverse effects on the pressure sensor chip 2.
As the protective agent 9, for example, a silicone resin, a fluorine resin, or the like can be used. For example, the protective agent 9 can be liquid or gel. The protective agent 9 preferably has a high viscosity. As the protective agent 9, for example, it is desirable to use a soft gel having a hardness of about 0 (Shore A hardness, conforming to JIS K 6253).

  The protective agent 9 can transmit the pressure applied from the measurement target to the pressure sensor chip 2 as it is. For this reason, the accuracy of pressure detection by the pressure sensor chip 2 is not lowered. The protective agent 9 desirably has low light transmittance. As a result, visible light and ultraviolet light can be blocked, which is advantageous for preventing the pressure sensor chip 2 from deteriorating. The protective agent 9 can reduce light transmittance by containing a pigment or the like.

The control unit 3 has a function of receiving a sensor signal from the pressure sensor chip 2 and outputting a pressure detection signal.
As the control part 3, what incorporates a temperature sensor can be used. The control unit 3 has functions such as ON / OFF control of the pressure sensor chip 2, correction of a detection value by a built-in temperature sensor, A / D conversion of detection data, correction of linearity, and shaping of a signal waveform. The control unit 3 incorporating the temperature sensor can correct the pressure detection signal according to the temperature in the system. For this reason, highly accurate pressure measurement becomes possible. As the temperature sensor, a resistance type (bridge resistance type), a diode type, a thermocouple type, an infrared type, or the like can be used.

  The control unit 3 is electrically connected to the lower surface of the lead portion 4b through the bonding wire 14. The control unit 3 is electrically connected to the lower surface of the lead portion 4 c through the bonding wire 15.

One end of each of the bonding wires 14 and 15 is connected to a circuit on the outer surface 3 a (the lower surface in FIG. 1) of the control unit 3. The bonding wires 14 and 15 pass from the control unit 3 through the stress relaxation layer 17, pass through the gap 18, pass through the base 7 of the support 5, and reach the lead frame 4 (lead portions 4 b and 4 c). The bonding wires 14 and 15 are protected from external force by being embedded in the stress relaxation layer 17 and the base 7.
One end of the bonding wire 13 is connected to the circuit on the upper surface 2 a of the pressure sensor chip 2. The bonding wire 13 passes through the protective agent 9 and reaches the lead frame 4 (lead portion 4b). The bonding wire 13 is protected from external force by being embedded in the protective agent 9.
The bonding wires 13, 14, and 15 are made of metal such as gold, copper, and aluminum.

  The pressure sensor chip 2 installed on the upper surface side of the pedestal portion 4a of the lead frame 4 has a circuit formed on the upper surface 2a, and the control unit 3 installed on the lower surface side of the pedestal portion 4a of the lead frame 4 A circuit is formed on 3a (the lower surface in FIG. 1). For this reason, the wiring length can be shortened and the influence of external noise can be reduced.

Next, an example of a method for manufacturing a pressure sensor will be described.
First, a lead frame 4 is formed by punching (pressing) a metal substrate (for example, a copper substrate). A necessary part of the lead frame 4 may be subjected to Ag plating.

Next, an uncured (liquid) low Young's modulus material is supplied to the control unit 3 or the pedestal unit 4a (lead frame 4) with a dispenser or the like, and cured by heating or the like to form the stress relaxation layer 17. The control unit 3 is connected to the lead portions 4b and 4c through the bonding wires 14 and 15.
The stress relaxation layer 17a can also be formed by a method of attaching a sheet body made of a low Young's modulus material to the control unit 3 or the pedestal unit 4a.

  Next, the lead frame 4 or the like is set in the mold, and the support body 5 is molded by injecting the mold resin M2 into the mold in that state. Thereby, the control unit 3, the stress relaxation layer 17, and the bonding wires 14 and 15 can be embedded in the support 5.

When the formation of the support 5 is completed, an annealing process (for example, 180 ° C.) is performed. When the temperature is returned to normal temperature, the difference between the shrinkage amount of the resin M2 constituting the support 5 and the resin M1 constituting the stress relaxation layer 17 causes a difference between the base 7 of the support 5 and the stress relaxation layer 17. A gap 18 is formed in the gap.
FIG. 2 is a photograph showing an example of a pressure sensor in which a gap 18 is formed between the base 7 and the stress relaxation layer 17.

  Next, the pressure sensor chip 2 is installed on the mounting portion 6 of the support 5, and the pressure sensor chip 2 is connected to the lead portion 4 b through the bonding wire 13. Subsequently, the inside of the accommodating part 10 is filled with the protective agent 9 to cover the pressure sensor chip 2. Thereby, the pressure sensor shown in FIG. 1 is obtained.

  In this pressure sensor, since the control unit 3 is covered with the stress relaxation layer 17, the stress generated in the components around the control unit 3 (the mounting unit 6 and the pedestal 4 a of the lead frame 4) is applied to the control unit 3. It is possible to prevent the output error of the control unit 3 from increasing. This will be described in detail below.

  The support 5 made of the mold resin M2 is in a state where a stress generated when the resin is cured, a thermal stress generated due to a temperature difference between the curing temperature and room temperature, and the like are applied. In this state, when temperature stress or humidity stress is applied by the external environment, the support 5 is easily deformed. Further, the lead frame 4 may be deformed as the support 5 is deformed. In particular, since the support 5 easily absorbs moisture under a high temperature and high humidity environment, such deformation easily occurs.

In this pressure sensor, since the control unit 3 is surrounded by the stress relaxation layer 17 made of a low Young's modulus material, it is possible to suppress the pressure from reaching the control unit 3 due to deformation of the support 5, the lead frame 4, and the like. For this reason, even when temperature stress or humidity stress is applied to the support 5 due to changes in the external environment, the measurement function of the temperature sensor of the control unit 3 is maintained normally, and an error occurs in the output of the temperature sensor. Can be suppressed.
Since the stress relaxation layer 17 has a curved convex surface, stress concentration is unlikely to occur. Therefore, the effect of suppressing the influence of deformation of the support 5 on the control unit 3 is enhanced, and the output of the temperature sensor is increased. It is possible to prevent errors from occurring.

Next, how the gap 18 is formed between the base 7 of the support 5 and the stress relaxation layer 17 and the effect of forming the gap 18 will be described.
Since the control unit 3 is sealed inside the support body 5 made of a mold resin, it is susceptible to swelling due to moisture absorption of the mold resin M2, and there is a concern about malfunction, but the influence from the support body 5 is This can be avoided by providing the stress relaxation layer 17 of the resin M1 having a low Young's modulus between the support 5 and the control unit 3.

For example, when using the control unit 3 in which a semiconductor resistance type temperature sensor is incorporated, it was confirmed that the following difference appears between the sample without the stress relaxation layer 17 and the sample with the stress relaxation layer 17. . Here, the results of measurement after being left for 100 hours under high-temperature and high-humidity conditions (60 ° C., 90% RH) and for 2 hours under normal-temperature / normal humidity conditions (25 ° C., 50% RH) are given.
In the case of the sample without the stress relaxation layer 17, the temperature sensor output was 28.1 ° C., and an output error of + 3.1 ° C. occurred. On the other hand, in the case of the sample having the stress relaxation layer 17, the temperature sensor output was 25.1 ° C. and the output error was + 0.1 ° C. From this result, the effect of the stress relaxation layer 17 was confirmed.

  However, when considering further reducing the output error, it is necessary to reduce not only the pressure from the base 7 side of the support 5 to the control unit 3 but also the pressure from the base 4a side of the lead frame 4. There is.

  FIG. 4 shows an example in which the layer thickness t1 of the stress relaxation layer 17a on the bottom surface 3b side of the control unit 3 is thin and the layer thickness t2 of the stress relaxation layer 17c on the outer surface 3a side of the control unit 3 is thick. In the case of this configuration, the pressure FA from the base 7 side of the support 5 can be effectively relieved because the layer thickness t2 of the stress relaxation layer 17c on the outer surface 3a side of the control unit 3 is thick. However, since the thickness t1 of the stress relaxation layer 17a on the bottom surface 3b side of the control unit 3 is thin, the relaxation effect is small against the pressure FB from the pedestal 4a side of the lead frame 4.

In order to suppress the influence of the pressure FB from the pedestal 4a side of the lead frame 4, as shown in FIG. 5, the layer thickness t1 of the stress relaxation layer 17a on the bottom surface 3b side of the control unit 3 is increased. It is valid.
However, when the thickness t1 of the stress relaxation layer 17a on the bottom surface 3b side of the control unit 3 is increased, the base 7 side of the support body 5, that is, the outer surface of the control unit 3 is provided when the total thickness of the stress relaxation layer 17 falls within a certain range. The layer thickness t2 of the stress relaxation layer 17c on the 3a side is reduced. Therefore, it becomes easy to receive the influence of the pressure from the base 7 side of the support body 5. FIG.

  In order to solve this, by increasing the overall thickness of the stress relaxation layer 17 as indicated by a two-dot chain line indicated by reference numeral 17x in FIG. 5, the stress relaxation layer 17a on the outer surface 3a side of the control unit 3 is increased. It is conceivable to increase the layer thickness t3. However, if it does so, the thickness tx of the base 7 by mold resin M2 will become thin by the part which the thickness of the whole stress relaxation layer 17 became thick. Therefore, there is a concern that the protective effect of the base 7 is lowered.

In order to solve this problem, as shown in FIG. 1, in the pressure sensor of the present embodiment, a gap 18 is secured between the stress relaxation layer 17 and the base 7 of the support 5.
By securing the gap 18, the pressure hardly reaches the control unit 3 even when the support 5 is swollen. Therefore, the thickness (layer thickness t1) of the stress relaxation layer 17a on the bottom surface 3b side of the control unit 3 can be increased. Thereby, the influence of the pressure to the control part 3 from the base part 4a side of the lead frame 4 can be reduced.

That is, in the pressure sensor according to the present embodiment, the force can be absorbed by the gap 18 from the base 7 side of the support body 5 due to swelling due to moisture absorption of the mold resin M2, etc. It can be made less susceptible to the effects of power. Therefore, the layer thickness t2 of the stress relaxation layer 17c on the outer surface 3a side of the control unit 3 is reduced, and the layer thickness t1 of the stress relaxation layer 17a on the bottom surface 3b side (lead frame 4 side) of the control unit 3 is increased accordingly. be able to.
Therefore, not only the force acting on the control unit 3 from the base 7 side of the support 5 but also the influence of the force acting on the control unit 3 from the pedestal 4a side of the lead frame 4 can be suppressed. It is possible to prevent the performance from being adversely affected.

  FIG. 3 shows the stress acting on the control unit 3 when there is a gap 18 between the stress relaxation layer 17 and the base 7 of the support 5 (Example 1) and when there is no gap 18 (Comparative Example 1). 6 is a characteristic diagram showing the difference in relation to the thickness (layer thickness) of the stress relaxation layer 17a on the bottom surface 3b side of the control unit 3. The vertical axis in this figure indicates the stress in the vicinity of the temperature sensor (center of the outer surface) of the control unit 3.

As shown in FIG. 3, when there is no gap 18 (Comparative Example 1), when the thickness of the stress relaxation layer 17 a on the bottom surface 3 b side of the control unit 3 is increased, the stress of the control unit 3 is increased.
On the other hand, when there is a gap 18 (Example 1), the stress of the control unit 3 decreases as the thickness of the stress relaxation layer 17a on the bottom surface 3b side of the control unit 3 increases.
Thus, in Example 1, since the clearance 18 was ensured, not only the pressure acting on the control unit 3 from the base 7 side of the support 5 but also the control unit 3 from the pedestal 4a side of the lead frame 4 was achieved. The influence of the acting pressure can also be suppressed. Therefore, the measurement error of the temperature sensor incorporated in the control unit 3 can be further reduced.

When there is no gap 18, if a positional shift occurs between the support 5 (mold resin M <b> 2) and the stress relaxation layer 17 (resin M <b> 1) due to temperature fluctuation, the support 5 and the stress relaxation layer 17 are not aligned. There is a possibility that an unnecessary shearing force acts on the bonding wires 14 and 15 at the boundary.
In the pressure sensor of this embodiment, since the bonding wires 14 and 15 can be slightly deformed due to the gap 18, the force applied to the bonding wires 14 and 15 can be relaxed and the breakage thereof can be prevented.

  As shown in FIG. 1B, the bonding wires 14 and 15 are covered with a coating of the resin M <b> 1 constituting the stress relaxation layer 17 in the gap 18. This is because the resin M1 remains attached around the bonding wires 14 and 15 even if the resin M1 is thermally contracted and the gap 18 is formed. It is preferable that the bonding wires 14 and 15 are covered with the resin M1 in the gap 18 because the bonding wires 14 and 15 are protected by the resin M1. The bonding wires 14 and 15 may be exposed in the gap 18.

  As shown in FIG. 6, when there is a concern that a gas such as water vapor is accumulated in the gap 18 and condensation occurs, a gas vent hole 19 communicating with the gap 18 can be formed in the base 7 of the support 5. . The gas vent hole 19 allows the gas in the gap 18 to be discharged to the outside, and adverse effects due to gas accumulation can be eliminated.

Although the pressure sensor of the present invention has been described above, the present invention is not limited to the above-described example, and can be appropriately changed without departing from the spirit of the invention. For example, in the pressure sensor shown in FIG. 1, the gap 18 is formed in the entire outer surface of the stress relaxation layer 17 (17b, 17c), but the gap is formed in at least a part of the outer surface of the stress relaxation layer. Just do it.
In addition, as shown in FIG. 1A and the like, when there are a plurality of bonding wires connecting the control unit and the lead frame, all of the plurality of bonding wires pass through the stress relaxation layer from the control unit and have gaps. However, only a part of the plurality of bonding wires may be wired by such a route.

  The pressure sensor of the present invention can be applied to portable equipment such as a diver's wristwatch equipped with a depth gauge.

  DESCRIPTION OF SYMBOLS 1 ... Base | substrate part, 2 ... Pressure sensor chip, 3 ... Control part, 3a ... Outer surface, 3b ... Bottom surface, 4 ... Lead frame, 4a ... Base part, 5. .. Support, 14, 15 ... Bonding wire, 17 ... Stress relaxation layer, 17a ... Stress relaxation layer on the bottom side of the control unit, 17c ... Stress relaxation layer on the outer surface side of the control unit, 18 ... gap, 19 ... gas vent, M1 ... resin constituting the stress relaxation layer, M2 ... resin (mold resin) constituting the support.

Claims (5)

A base portion having a lead frame and a resin support for supporting the lead frame;
A pressure sensor chip provided on one surface side of the lead frame;
A control unit provided on the other surface side of the lead frame and receiving a sensor signal from the pressure sensor chip and outputting a pressure detection signal;
The control unit has a stress relaxation layer made of a resin having a Young's modulus lower than that of the resin constituting the support, and at least a bottom surface on the lead frame side and an outer surface that is the opposite surface thereof are covered thereon. The support is encapsulated inside the support by being molded,
The pressure sensor according to claim 1, wherein a gap is formed between the stress relaxation layer on the outer surface side that covers the outer surface of the control unit and the support.   Since the thermal expansion coefficient of the resin constituting the stress relaxation layer is larger than the thermal expansion coefficient of the resin constituting the support, the stress relaxation layer is cooled during annealing after the molding of the support. 2. The pressure sensor according to claim 1, wherein the gap is formed by a difference in shrinkage between the resin constituting the resin and the resin constituting the support.   The pressure sensor according to claim 1, wherein a temperature sensor is incorporated in the control unit. The control unit is electrically connected to the lead frame by a bonding wire,
The at least part of the bonding wire passes through the stress relaxation layer from the control unit, passes through the gap, and reaches the lead frame through the support. The pressure sensor according to any one of claims.   The pressure sensor according to claim 1, wherein a gas vent hole communicating with the gap is formed in the support.