JP4269487B2 - Manufacturing method of pressure sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
In the present invention, a sensor chip for pressure detection is mounted on a resin case in which a conductor member is insert-molded, and the sensor chip and the conductor member are covered and protected with a thermosetting protective member having electrical insulation. In particular, the present invention relates to a method for arranging a protective member.
[0002]
[Prior art]
Conventionally, as this kind of pressure sensor, a sensor described in JP-A-11-304619 has been proposed. In this device, the protective member has a two-layer structure having different elastic moduli (Young's modulus). The first protection member having a relatively high elasticity covers at least the conductor member and its peripheral portion with the sensing portion of the sensor chip exposed, and the second protection member having a relatively low elasticity covers the sensor chip. The sensing unit and the first protective member are covered.
[0003]
And according to the said prior art gazette, the conductor member and its peripheral part are covered with the 1st protection member which is comparatively highly elastic. For this reason, it can be said that air that is present in the gap between the insert-molded conductor member and the resin case can be prevented from being generated as bubbles in the protective member when negative pressure is detected.
[0004]
[Problems to be solved by the invention]
However, according to the study by the present inventors, it has been found that the following problems occur in the conventional pressure sensor. In general, since the above-described protective member uses a thermosetting rubber material or gel material, the protective member is formed by arranging a protective member at a desired portion of the resin case, and then performing a heat treatment and curing. The
[0005]
At this time, a problem as shown in FIG. 4 occurs. As shown in FIG. 4A, when the protective member 50 is filled in the resin case 10, the gap between the insert-molded conductor member 30 and the resin case 10 is not completely filled with the protective member 50, and the air layer K1 may remain.
[0006]
When the protection member 50 is heat-treated in this state, the air layer K1 expands during the curing of the protection member, and bubbles K2 are generated in the protection member 50 as shown in FIG. At this time, the bubble K2 may be cured while remaining in the vicinity of the sensor chip 20. Then, the bubble K2 expands and contracts in the vicinity of the sensor chip 20 due to a pressure change at the time of detecting the pressure, which affects the sensor characteristics or causes the wire 40 to be broken.
[0007]
In view of the above problems, the present invention is a pressure in which a sensor chip for pressure detection is mounted on a resin case in which a conductor member is insert-molded, and the sensor chip and the conductor member are covered and protected with a thermosetting protective member. An object of the method for manufacturing a sensor is to suppress the generation of bubbles in the protective member when the protective member is cured.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, in the first aspect of the present invention, after covering the conductor member (30) and the sensor chip (20) with the protective member (50), the protective member (50) is pressurized from the outside. The protective member (50) is provided with a second protective member (52) that is less elastic than the first protective member on the outside of the first protective member (51). In the covering with the protective member, the first protective member covers at least the conductor member and its peripheral portion with the sensing portion of the sensor chip (20) exposed. In the heat curing of the protection member, the first protection member and the second protection member are thermally cured at the same time .
[0009]
According to it, in order to heat-protect the protective member (50) while applying pressure from the outside, even if an air layer remains in the gap between the insert-molded conductor member (30) and the resin case (10), This air layer can be restrained from expanding into the protective member (50). Therefore, according to this invention, when hardening a protection member, it can suppress that a bubble generate | occur | produces in a protection member. Here, it is preferable to pressurize the protective member at a pressure of 44 kPa or more (invention of claim 2).
[0011]
Here, a rubber-based material can be used as the first protective member (51), and a gel-like substance can be used as the second protective member (52) (the invention of claim 3 ).
[0012]
In addition, the code | symbol in the parenthesis of each said means is an example which shows a corresponding relationship with the specific means as described in embodiment mentioned later.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments shown in the drawings will be described below. FIG. 1 is a schematic cross-sectional view of a pressure sensor 100 according to this embodiment. The pressure sensor 100 can be applied to, for example, an intake pressure sensor that is attached to an intake manifold of an automobile and detects intake pressure (negative pressure).
[0014]
The resin case 10 is formed by molding a resin material such as PPS (polyphenylene sulfide), PBT (polybutylene terephthalate), or an epoxy resin. On the upper surface of the resin case 10, an open recess 11 for mounting a sensor chip 20 to be described later is formed.
[0015]
The resin case 10 is integrally provided with a plurality of pins (conductor member in the present invention) 30 made of a conductive material such as copper by insert molding. One ends 31 of these pins 30 are arranged so as to be exposed at the bottom surface of the recess 11. And this exposed part is comprised so that it may function as a bonding pad by giving gold plating. The other end 32 of the pin 30 can be connected to an external device (external wiring member or the like).
[0016]
A sensor chip 20 mounted in the recess 11 of the resin case 10 holds a semiconductor substrate (silicon substrate or the like) 21 that detects pressure and generates an electric signal at a level corresponding to the detected value, and the semiconductor substrate 21. And a glass pedestal 22. The semiconductor substrate 21 has a known configuration using a piezoresistance effect, and has a configuration in which a diaphragm 21a as a sensing unit and a diffusion resistor (not shown) are provided on the upper surface thereof.
[0017]
The semiconductor substrate 21 is die-bonded to the bottom surface of the recess 11 with an adhesive such as silicone rubber through a glass pedestal 22. Each input / output terminal (not shown) of the semiconductor substrate 21 is electrically connected to one end 31 of the pin 30 via a wire 40 such as gold or aluminum. Thus, the sensor chip 20 is electrically connected to the pin 30 while being mounted in the recess 11 of the resin case 10.
[0018]
The recess 11 is filled with a protective member 50 made of an electrically insulating material having chemical resistance so as to fill the sensor chip 20 and the wire 40. The protective member 50 covers the sensor chip 20, the pin 30, the wire 40, the connecting portion between the semiconductor substrate 21 and the wire 40, and the connecting portion between the pin 30 and the wire 40. Ensuring insulation and anticorrosion are achieved.
[0019]
Here, the protection member 50 has a two-layer structure in which a second protection member 52 that is less elastic than the first protection member 51 is laminated on the first protection member 51. For this two-layer structure, basically the same structure as the two-layer structure disclosed in Japanese Patent Application Laid-Open No. 11-304619 described in the section “Prior Art” can be applied.
[0020]
That is, the first protective member 51 in the lower layer has the sensing portion of the semiconductor substrate 21 and the upper portion of the wire 40 exposed, the sensor chip 20, the connection portion between the wire 40 and the pin 30, the pin 30 and the peripheral portion thereof. It is provided so as to cover. The upper second protective member 52 covers the sensing portion of the sensor chip 20 and the wire 40 exposed from the first protective member 51.
[0021]
For example, both of these protective members 51 and 52 are made by thermally curing a fluorine-based material. The first protective member 51 is a fluorine-based rubber material having a high elastic modulus and chemical resistance in order to suppress the generation of bubbles from the gap between the pin 30 and the resin case 10. On the other hand, the second protective member 52 is a fluorine-based gel material that has a low elastic modulus and does not apply stress to the sensor chip 20 and the wire 40 and has chemical resistance.
[0022]
Such a pressure sensor 100 is manufactured as follows. First, the sensor chip 20 is mounted on the resin case 10, and the semiconductor substrate 21 and the pin 30 are connected by wire bonding. Subsequently, after the one in this state is placed in the sealed container, the first protective member 51 and the second protective member 52 before curing are sequentially filled into the recess 11 in a vacuum.
[0023]
Next, as shown in FIG. 2, a gas such as compressed air or inert gas is introduced into the sealed container, and the inside of the sealed container is brought into a pressurized state (for example, 44 kPa). Thereby, as shown by the arrow in FIG. 3, the entire periphery of the pressure sensor 100 is pressurized. While maintaining this pressurized state, the temperature in the sealed container is set to a curing temperature (for example, 150 ° C.) at which both the protective members 51 and 52 can be cured. In this way, both the protective members 51 and 52 are thermally cured, and the pressure sensor 100 is completed.
[0024]
When applied to the above-described intake pressure sensor, the pressure sensor 100 is disposed in a state where the concave portion 11 communicates with an engine intake passage in an automobile. As a result, an electrical signal corresponding to the applied pressure is output from the sensor chip 20 via the wire 40 and the pin 30, and the intake pressure (negative pressure) is detected.
[0025]
By the way, in the manufacturing method of this embodiment, after covering the pin (conductor member) 30 and the sensor chip 20 with the protective member 50 (51 and 52), the protective member 50 is thermally cured while being pressurized from the outside. It is a feature. As a result, an air layer (existing in the gap between the pin 30 and the resin case 10 in FIG. 2) K1 is formed in the gap between the pin 30 and the resin case 10 or the gap at the bonding interface between the sensor chip 20 and the bottom surface of the recess 11. Even if it remains, the air layer K1 is compressed during curing. Therefore, even if heat is applied to the air layer K1, the protection member 50 is cured without increasing the volume of the air layer K1 to the outside of the gap.
[0026]
Thus, since the air layer K1 can be restrained from expanding into the first protective member 51 during the curing, the air layer K1 remains in its original position after the protective member 50 is cured, and the first The protective member 51 does not go up. Therefore, according to this manufacturing method, when the protection member 50 is cured, it is possible to suppress the generation of bubbles in the protection member 50. Since bubbles can be prevented from being present in the vicinity of the sensor chip 20, it is possible to stabilize sensor characteristics, prevent disconnection of the wire 40, and the like.
[0027]
Here, it is preferable to pressurize the protective member in the above manufacturing method at a pressure of 44 kPa or more. In this embodiment, the curing temperature of the protective member 50 is about 150 ° C., and when the curing temperature is 150 ° C., the pressure of the air layer K1 is 44 kPa (100 × (423 [K] -293 [K]). ) ÷ 293 [K] [kPa], K indicates absolute temperature) Therefore, if it pressurizes with the pressure of 44 kPa or more, expansion of air layer K1 can be controlled suitably.
[0028]
In addition, if the viscosity of the protective member 50 when filling the resin case 10 is sufficiently high and the protective member 50 does not leak from the gap between the pin 30 and the resin case 10 to the other end 32 side of the pin 30 due to pressurization. For example, as shown in FIG. 3, only the upper part of the recess 11 that is the sensor chip installation portion may be pressurized. In this case, for example, by placing a jig capable of introducing pressure above the recess 11 and applying compressed air or the like from the jig, it is possible to pressurize only the upper part of the recess 11.
[0029]
Moreover, although it changes with kinds of protection member 50, the upper limit of the pressurization of the protection member in the said manufacturing method protects from the clearance gap between the pin 30 and the resin case 10 to the other end 32 side of the pin 30 in the case of pressurization. It is preferable that the member 50 (the first protective member 51) does not leak.
[0030]
In the present embodiment, the protective member 50 has a two-layer structure in which a second protective member 52 having low elasticity is laminated on a first protective member 51 having high elasticity. This is because bubbles or the like generated from the resin case 10 side are prevented by the first protective member 51 made of a hard rubber material, and the sensing part of the sensor chip 20 is made of a soft gel-like substance with little stress influence. The purpose is to cover with the second protective member 52.
[0031]
Since the second protective member 52 that is soft is used as the upper layer, if bubbles are generated in the protective member 50, when detecting a negative pressure, the bubbles are soft in the second protective member 52. May cause the protective member 50 to split or the wire 40 to break. However, in this embodiment, since the effect by the said manufacturing method is exhibited, there is no such a problem. That is, it can be said that the method of thermosetting while applying pressure is particularly suitable for the two-layer structure as in this embodiment.
[0032]
(Other embodiments)
When the pressure sensor of the present invention is applied to one that detects a relatively low negative pressure or one that detects a positive pressure, the two-layer structure as described above using a hard rubber-based material as a protective member. For example, a single layer structure using only a gel material may be used.
[0033]
In addition, the pressure sensor of the present invention is not limited to the semiconductor diaphragm type sensor chip as in the above embodiment, and can be applied to, for example, a capacitance type sensor chip.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a pressure sensor according to an embodiment of the present invention.
2 is a schematic cross-sectional view showing a state of pressurization in the manufacturing method of the pressure sensor of FIG. 1;
FIG. 3 is a schematic cross-sectional view showing another pressurizing method in the manufacturing method of the pressure sensor of the embodiment.
FIG. 4 is a schematic cross-sectional view showing how bubbles are generated in a protective member in a conventional pressure sensor.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Resin case, 20 ... Sensor chip, 30 ... Pin, 50 ... Protection member,
51 ... 1st protection member, 52 ... 2nd protection member.

Claims (3)

After mounting the sensor chip (20) that generates an electric signal based on the applied pressure on the resin case (10) in which the conductor member (30) is insert-molded, in a state of being electrically connected to the conductor member, In the method of manufacturing a pressure sensor, the conductor member and the sensor chip are covered and protected with a thermosetting protection member (50) having electrical insulation,
After covering the conductor member and the sensor chip with the protective member, the protective member is thermoset while being pressurized from the outside ,
The protective member (50) has a two-layer structure in which a second protective member (52) having lower elasticity than the first protective member is laminated on the outside of the first protective member (51). And
In the covering by the protective member, the first protective member is provided so as to cover at least the conductor member and its peripheral portion with the sensing portion of the sensor chip (20) exposed.
In the thermosetting of the protective member, the first protective member and the second protective member are thermoset simultaneously, and the pressure sensor manufacturing method is characterized in that:   The pressure sensor manufacturing method according to claim 1, wherein the protective member is pressurized at a pressure of 44 kPa or more. The method for manufacturing a pressure sensor according to claim 1 or 2 , wherein a rubber-based material is used as the first protective member (51), and a gel-like substance is used as the second protective member (52) .

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