Patent Application
20170284886
This application claims benefit of Japanese Patent Application No. 2016-068863 filed on Mar. 30, 2016, which is hereby incorporated by reference.
The present invention relates to a waterproof pressure sensor and a manufacturing method for the waterproof pressure sensor, and particularly to a waterproof pressure sensor in which a pressure detection element is covered with a gel agent and a manufacturing method for the waterproof pressure sensor.
In order to cause a pressure sensor to have a waterproof function, a pressure detection element is required to be covered with a soft resin such as gel. The resin climbs up a wall surface during curing, and there is a problem in that the resin protrudes to the outside and entrapment of air bubbles occurs at the time of coating.
Japanese Unexamined Patent Application Publication No. 2006-220456 discloses a relative pressure type pressure sensor in which a back side of a sensor chip is sealed with a gel member. In the pressure sensor, a pressure introducing hole is provided with a chip back side gel member for sealing the back side of the sensor chip. The chip back side gel member has a two-layer structure in which a hard gel covers a soft gel.
However, in the pressure sensor disclosed in Japanese Unexamined Patent Application Publication No. 2006-220456, when the gel with the two-layer structure is formed, two kinds of liquid agents are repeatedly coated before curing, and thus it is hard to form a stable upper gel. The two kinds of liquid agents are used, and this increases the number of manufacturing steps or cost. The hard gel is less likely to climb up a wall surface than the soft gel, but climbs up when the liquid agent is cured, and thus is not suitable for miniaturization, especially, reduction in height. A liquid agent is likely to contain air bubbles when the liquid agent is injected so as to be gelled, and, if the air bubbles remain in a gel agent, this reduces the pressure detection accuracy due to the influence of expansion and contraction of air in the air bubbles.
The present invention provides a waterproof pressure sensor capable of simplifying manufacturing steps and having a structure in which air bubbles hardly remain in a gel agent, and a manufacturing method for the waterproof pressure sensor.
According to an aspect of the present invention, there is provided a waterproof pressure sensor including a pressure detection element; a cavity package configured to be provided with a recess in which the pressure detection element is mounted and an edge provided around the recess; a cover member attached to the edge of the cavity package and to be provided with a pressure introducing hole having a diameter smaller than a diameter of an opening of the recess in a plan view at a position overlapping the recess; and a gel agent configured to be provided in the recess, in which an exhaust portion is provided at the cover member at least on the recess side, the exhaust portion being capable of discharging air in the recess to the outside when the gel agent is injected from the pressure introducing hole into the recess, and the exhaust portion is filled with the gel agent.
According to the configuration, even if air is entrapped by a liquid agent when the liquid agent serving as the gel agent is injected from the pressure introducing hole into the recess, the air is discharged to the outside through the exhaust portion. Therefore, it is possible to prevent air bubbles from remaining in the gel agent.
In the waterproof pressure sensor according to the aspect of the present invention, the exhaust portion may be provided to communicate with the pressure introducing hole. Consequently, air entrapped by the liquid agent proceeds to the pressure introducing hole along the exhaust portion, and is discharged to the outside through the pressure introducing hole.
In the waterproof pressure sensor according to the aspect of the present invention, the exhaust portion may include a diameter increasing portion whose diameter increases from the outside of the cover member toward the recess side. Consequently, air entrapped by the liquid agent when injecting a liquid agent serving as the gel agent is gradually pushed toward the pressure introducing hole along the diameter increasing portion and is then discharged to the outside.
In the waterproof pressure sensor according to the aspect of the present invention, a shape of the diameter increasing portion in a plan view may be a polygonal shape or a circular shape. Consequently, when a liquid agent serving as the gel agent is injected from the pressure introducing hole, the liquid agent radially spreads from an injection position in the recess, and thus entrapment of air can be prevented.
In the waterproof pressure sensor according to the aspect of the present invention, an outer shape of the diameter increasing portion in a plan view may be located outside a vertex of a loop of a bonding wire connected to a component mounted in the recess. Consequently, it is possible to prevent interference between the loop of the bonding wire and the cover member and thus to realize a reduction in height.
In the waterproof pressure sensor according to the aspect of the present invention, an extension direction of the bonding wire in a plan view may be a direction which is not orthogonal to a radial direction from the center of the pressure introducing hole. Consequently, when a liquid agent serving as the gel agent is injected from the pressure introducing hole, the liquid agent easily flows along the bonding wire, and thus it is possible to prevent entrapment of air.
The waterproof pressure sensor according to the aspect of the present invention may further include a circuit element configured to be connected to the pressure detection element, and the pressure detection element may overlap the circuit element. Consequently, it is possible to miniaturize the waterproof pressure sensor.
According to another aspect of the present invention, there is provided a manufacturing method for the waterproof pressure sensor, the method including a step of mounting the pressure detection element in the recess of the cavity package; a step of attaching the cover member to the edge of the cavity package so that the recess overlaps the pressure introducing hole; and a step of injecting a liquid agent into the recess from the pressure introducing hole so as to gel the liquid agent, in which, when the liquid agent is injected, the liquid agent fills the recess and then fills the exhaust portion so that air bubbles in the liquid agent is discharged to the outside of the cover member.
According to the configuration, even if air is entrapped by a liquid agent when the liquid agent serving as the gel agent is injected from the pressure introducing hole into the recess, the air is discharged to the outside through the exhaust portion. Therefore, it is possible to prevent air bubbles from remaining in the gel agent.
In the manufacturing method for the waterproof pressure sensor according to the aspect of the present invention, when the liquid agent is injected from the pressure introducing hole, the liquid agent may be injected from the center of the recess to the outside of the center in a plan view. Consequently, when a liquid agent serving as the gel agent is injected from the pressure introducing hole, the liquid agent radially spreads from an injection position in the recess, and thus entrapment of air can be prevented.
According to the present invention, it is possible to provide a waterproof pressure sensor capable of simplifying manufacturing steps and having a structure in which air bubbles hardly remain in a gel agent, and a manufacturing method for the waterproof pressure sensor.
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same members are given the same reference numerals, and members described once will not be described as appropriate.
A waterproof pressure sensor 1 according to the present embodiment is a sensor detecting applied sensor with a pressure detection element 10, and has a waterproof function by covering a periphery of the pressure detection element 10 with a gel agent 50.
The waterproof pressure sensor 1 includes the pressure detection element 10, a cavity package 20, the cover member 30, and the gel agent 50. The pressure detection element 10 is, for example, a chip component in which a diaphragm is formed in a semiconductor such as silicon through etching.
The cavity package 20 includes a recess 21 on which the pressure detection element 10 is mounted, and an edge 22 provided around the recess 21. The cavity package 20 is made of, for example, ceramics such as alumina. Metallized patterns P are formed on a step difference portion 21a or the like of the recess 21. In the present embodiment, in addition to the pressure detection element 10, a circuit element 15 is also mounted in the recess 21. Bonding wires BW are connected to the pressure detection element 10 and the circuit element 15, and thus the elements are connected to each other or connected to the metallized patterns P.
The cover member 30 is attached onto the edge 22 of the cavity package 20 via an adhesive. A ceramic is used for the cover member 30 in the same manner as for the cavity package 20. A pressure introducing hole 31 is provided at the substantially center of the cover member 30. A diameter of the pressure introducing hole 31 is smaller than a diameter of an opening of the recess 21 in a plan view. The pressure introducing hole 31 is disposed at a position overlapping the recess 21 in a state in which the cover member 30 is attached onto the cavity package 20.
The gel agent 50 is provided in the recess 21. In other words, the gel agent 50 fills the recess 21 so as to cover the pressure detection element 10 and the circuit element 15 mounted in the recess 21 and the bonding wires BW. For example, a fluorine gel or silicone gel is used for the gel agent 50.
In the waterproof pressure sensor 1 having the configuration, a tapered portion 32 as an exhaust portion is provided on at least the recess 21 side of the cover member 30. The tapered portion 32 is a diameter increasing portion whose diameter increases from the outside of the cover member 30 toward the recess 21 side. The gel agent 50 fills the recess 21 and also fills the tapered portion 32.
The tapered portion 32 is provided to communicate with the pressure introducing hole 31. Since the tapered portion 32 is provided at the cover member 30, even if air is entrapped by a liquid agent when the liquid agent serving as the gel agent 50 is injected from the pressure introducing hole 31 into the recess 21, air bubbles caused by the air are discharged to the outside from the tapered portion 32 via the pressure introducing hole 31. Therefore, it is possible to prevent air bubbles from remaining in the gel agent 50.
In the waterproof pressure sensor 2 according to the reference example illustrated in
On the other hand, in the waterproof pressure sensor 1 according to the present embodiment, even if air is entrapped when a liquid agent serving as the gel agent 50 is injected from the pressure introducing hole 31 into the recess 21, air bubbles can be pushed up along the tapered portion 32 as a result of the liquid agent being injected, and thus the air bubbles escape to the outside through the pressure introducing hole 31. Therefore, it is possible to prevent air bubbles from remaining the gel agent 50.
Next, the bonding wires BW are wired. The bonding wires BW are wired between the circuit element 15 and the metallized patterns P (refer to
Next, as illustrated in
If extension directions of the bonding wires BW in a plan view are set to directions which are not orthogonal to a radial direction from the center of the recess 21 when the bonding wires BW are wired, the liquid agent 55 easily flows along the bonding wires BW when the liquid agent 55 is injected. Consequently, it is possible to prevent air from being entrapped by the liquid agent 55.
As illustrated in
According to the manufacturing method, even if air is entrapped by the liquid agent 55 and thus the air bubbles B are generated when the liquid agent 55 is injected from the pressure introducing hole 31 into the recess 21, the air bubbles B can be discharged to the outside along the tapered portion 32. Therefore, it is possible to prevent air bubbles from remaining in the gel agent 50.
In a waterproof pressure sensor 1B according to the present embodiment, a counterbore portion 33 which is approximately at right angles is provided as an exhaust portion at the cover member 30 on the recess 21 side. Since the counterbore portion 33 is provided, when the liquid agent 55 is injected from the pressure introducing hole 31 into the recess 21, it takes time for the surface of the liquid agent 55 to reach the rear surface of the cover member 30. Therefore, there is a high probability that the air bubbles B generated in the liquid agent 55 may float upward as a result of injection of the liquid agent 55. Consequently, the air bubbles B are easily discharged to the outside through the pressure introducing hole 31.
In a waterproof pressure sensor 1C according to the present embodiment, the pressure detection element 10 overlaps the circuit element 15 in the recess 21 of the cavity package 20. If the pressure detection element 10 overlaps the circuit element 15, it is possible to miniaturize the waterproof pressure sensor 1C in a plan view. In the present embodiment, the pressure detection element 10 is disposed inside the tapered portion 32 of the cover member 30, and thus it is possible to realize a reduction in height even if the pressure detection element 10 overlaps the circuit element 15.
As described above, according to the embodiments, it is possible to provide the waterproof pressure sensors 1, 1B and 1C in which manufacturing steps are simplified and air bubbles B do not remain in the gel agent 50, and the manufacturing method for the waterproof pressure sensor.
The present embodiments have been described above, but the present invention is not limited to such embodiments. For example, the tapered portion 32 and the counterbore portion 33 have been described as examples of exhaust portions, but a hole which penetrates to the recess 21 may be provided in the cover member 30 as an exhaust portion, and the air bubbles B generated when the liquid agent 55 is injected may be discharged to the outside through the hole. Embodiments obtained by a person skilled in the art adding or deleting constituent elements to or from the above-described embodiments, or modifying design of the above-described embodiments, or embodiments obtained by combining the features of the configuration examples of the respective embodiments with each other as appropriate are all included in the scope of the present invention without departing from the spirit of the present invention.
It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims of the equivalents thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2016-068863 | Mar 2016 | JP | national |
