JP3099584B2 - Manufacturing method of surface pressure type semiconductor pressure sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a surface pressure type semiconductor pressure sensor applied to an atmospheric pressure sensor and the like.

[0002]

2. Description of the Related Art As a surface pressure type semiconductor pressure sensor, a pressure-sensitive diaphragm chip manufactured by diffusing a strain gauge resistance in a diaphragm portion of a silicon wafer is mounted on a printed circuit board also serving as a stem, and a surface electrode of the chip is provided. A configuration is known in which a chip is surrounded by a case after being connected to a printed circuit board by wire and assembled.

When such a surface pressure type pressure sensor is used as an atmospheric pressure sensor, a high environmental resistance is required to protect the pressure-sensitive diaphragm chip from corrosion due to moisture or the like. The surface of the pressure diaphragm chip is sealed by applying a silicone gel having high moisture resistance and corrosion resistance. FIG. 6 shows an assembly structure of the surface pressure type semiconductor pressure sensor and a conventional silicone gel coating method.
Pressure-sensitive diaphragm chip 1 fixed to glass pedestal 2
Is mounted on the thick-film printed board 3 serving also as a stem via a metal base 4 supporting the pressure-sensitive diaphragm chip 1.
And the printed circuit board 3 are connected by an aluminum wire 5 (bonding wire). Further, the printed circuit board 3 is surrounded by the pressure-sensitive diaphragm chip 1 and the aluminum wire 5.
The case 6 is assembled on the upper surface of. This case 6
Although not shown in the figure, a protective cap with a pressure guiding hole is attached.

As a method for applying a silicone gel 8 for protecting the surface of the pressure-sensitive diaphragm chip 1 to the surface-pressure-type semiconductor pressure sensor having such a configuration, a conventional method uses a pressure-sensitive diaphragm from above the case 6 through a nozzle 7. In general, a method in which an appropriate amount of silicone gel 8 is applied dropwise onto the chip 1 is applied.

[0005]

According to the method described above,
The conventional coating method in which the silicone gel is dropped onto the pressure-sensitive diaphragm chip from above has the following problems. That is, when the silicone gel is dropped on the pressure-sensitive diaphragm chip as shown in FIG. 6, the silicone gel rises in a convex shape on the surface of the pressure-sensitive diaphragm chip.
That is, the thickness of the silicone gel is thicker at the center of the pressure-sensitive diaphragm chip and thinner at the periphery. For this reason, the stress generated by the temperature change does not become uniform distribution,
This adversely affects the sensitivity of pressure detection.

Further, since the aluminum wire connected between the pressure-sensitive diaphragm chip and the printed board by the wire bonding method is wired in a loop above the pressure-sensitive diaphragm chip, the aluminum wire is not used in the above-described dropping method. The silicone gel is not applied to the entire surface, and an uncoated portion is generated, which causes disconnection due to corrosion. In addition, it is conceivable that the pressure-sensitive diaphragm tip and the entire aluminum wire are buried in the silicone gel by increasing the drop amount of the silicone gel. The external pressure is greatly attenuated in the process of propagating in the silicone gel layer, and the influence on the sensitivity reduction of the pressure sensor is increased.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to minimize the thickness of the silicone gel applied in the silicone gel application step so as to cover the entire surface of the pressure-sensitive diaphragm chip and wire. It is another object of the present invention to provide a method for manufacturing a surface pressure type semiconductor pressure sensor which enables uniform application of a silicone gel in a short time.

[0008]

According to the present invention, an object of the present invention is to mount a pressure-sensitive diaphragm chip on a printed board,
The surface electrode of the pressure-sensitive diaphragm chip is connected to the printed board with a wire, and the pressure-sensitive diaphragm chip is mounted in a state where the case is assembled on the printed board surrounding the pressure-sensitive diaphragm chip and the wire. And by injecting the silicone gel to a level where the wire is buried in the silicone gel layer, and then sucking the silicone gel out of the case to apply the silicone gel to the entire surface of the pressure-sensitive diaphragm chip and wire.

In this configuration, a gel discharge collet having an air hole on a wall surface is connected to the opening of the case, and the silicone gel is sucked out of the case by a vacuuming method with the opening of the case facing downward. Means that the silicone gel is sucked out so that the coating thickness of the silicone gel attached to the surface of the pressure-sensitive diaphragm chip and the wire becomes 30 to 80 μm.

[0010]

As described above, first, an excessive amount of silicone gel is injected into the case so that the entire pressure-sensitive diaphragm chip and wire are buried in the silicone gel layer, and then the silicone gel is removed from the case by a vacuuming method. , Excess silicone gel is removed from the case, leaving the amount attached to the surface of the pressure-sensitive diaphragm tip and wire. Here, a gel discharging collet having an air hole on the wall surface was connected to the opening of the case, and the silicone gel was sucked out of the case by vacuuming with the opening of the case facing downward. The gel flows below the opening of the case, and the outside air is drawn in from the air holes, so that the silicone gel can be sucked out of the case in a short time.

If the evacuation is performed by setting the evacuation pressure appropriately, the coating thickness is about 30 to 80 μm (preferably 50 μm) over the entire surface of the pressure-sensitive diaphragm chip and wire.
m), the silicone gel is uniformly applied.
This coating thickness (30 to 80 μm) is the minimum thickness determined by the viscosity and surface tension of the silicone gel material itself,
It is also confirmed from the result of the characteristic test of the surface pressure type semiconductor pressure sensor described later that the influence of the pressure-sensitive diaphragm chip characteristic on the zero slope and the output fluctuation error is minimized.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. The same members as those in FIG. 6 are denoted by the same reference numerals. The present invention is not limited to the surface pressure type semiconductor pressure sensor, but includes a semiconductor chip mounted on a printed circuit board and a semiconductor element formed by connecting a surface electrode of the chip and the printed circuit board with a wire. It is also effective when a coating agent is applied uniformly over the entire surface for surface protection. [First Embodiment] First, after assembling a pressure sensor by the same assembling method as described with reference to FIG. 6, when applying a silicone gel 8 to the surface of the pressure-sensitive diaphragm chip 1 and the aluminum wire 5, as shown in FIG. Excessive silicone gel 8 is injected into case 6 to such a level that pressure-sensitive diaphragm chip 1 and aluminum wire 5 are buried in the gel layer. In this embodiment, aluminum is used for the wire, but any wire that is commercially available as a bonding wire may be used. As the silicone gel 8, it is preferable to use a silicone gel having a penetration of about 80 to 120 after curing.

Next, a gel discharge collet 9 having an air hole 10 on the wall surface is connected to the opening 6a of the case 6 using the silicone gel suction device having the structure shown in FIG.
The silicone gel 8 is sucked out of the case 6 by the evacuation method with the opening 6a facing downward. It is sufficient that the diameter of the air hole 10 is as small as about 1 mm. As a result, as shown in FIG. 3, all the excess silicone gel is discharged out of the case except for the portion remaining on the surfaces of the pressure-sensitive diaphragm chip 1 and the aluminum wire 5, and finally the pressure-sensitive diaphragm chip 1 and the aluminum wire A silicone gel 8 having a uniform thickness is applied to the entire surface of the wire 5.
When the application operation of the silicone gel is completed, the gel discharging collet 9 is removed from the case 6, and a protective cap having a pressure guide hole is attached to the case 6 in the next assembling step to manufacture a surface pressure type semiconductor pressure sensor.

Here, the silicone gel suction device having the structure shown in FIG. 2 will be described. In this apparatus, a plurality of piping systems having a gel discharge collet 9, a vacuum pressure gauge 14 and a three-way valve 15 and a piping system having a vacuum pump 11 and a valve 12 are connected via a trap 13 for storing the sucked silicone gel 8. It is a thing. When sucking the silicone gel 8, the valve 12 is opened and the vacuum pump 11 is opened.
Activate Since the three-way valve 15 has a function of switching the gel discharging collet 9 to vacuum or atmospheric pressure, the individual gel discharging collet 9 can be easily switched to vacuum or atmospheric pressure by opening and closing the three-way valve 15. Since it is possible, it has a feature that it can be operated continuously at random and at the same time can suck out silicone gels 8 of semi-finished products of different types. [Embodiment 2] In this embodiment, a characteristic test of a surface pressure type semiconductor pressure sensor manufactured based on Embodiment 1 is performed.

FIG. 4 is a characteristic diagram showing the relationship between the zero-point inclination of the pressure-sensitive diaphragm chip and the thickness of the silicone gel applied to the chip surface. FIG. 5 is a high-temperature and high-humidity test (85 ° C., 85% humidity) of the pressure sensor. RH) FIG. 4 is a characteristic diagram showing the relationship between the output fluctuation error obtained from the result and the gel thickness. As can be seen from FIGS. By applying silicone gel to the surface of the pressure diaphragm chip,
The zero-point tilt of the pressure-sensitive diaphragm chip is very small (Fig. 4
), And the output fluctuation error is also minimum (see FIG. 5), thereby obtaining high measurement accuracy.

From this, it was confirmed that the vacuum pressure should be set so that the coating thickness of the silicone gel 8 is 30 to 80 μm, preferably 50 μm. [Comparative Example 1] A comparative experiment was performed on the case 6 with the opening 6a facing downward and on the case 6 with the opening 6a facing upward. It was a time that could withstand mass production, but it was not suitable for mass production when it was directed upward.

Further, when a plurality of openings 6a of the case 6 were set outward and rotated to separate the silicone gel using centrifugal force, a liquid pool was formed at the place corresponding to the bag, and it was necessary to rework.

[0018]

According to the present invention, the problem caused by the conventional gel dropping method can be solved, and the silicone gel can be uniformly applied to the entire surface of the pressure-sensitive diaphragm chip and the wire with an appropriate thickness. As a result, it is possible to provide a surface pressure type semiconductor pressure sensor having high environmental resistance against humidity, corrosion, etc., while ensuring high measurement accuracy.

[Brief description of the drawings]

FIG. 1 is a sectional view showing the configuration of a surface pressure type semiconductor pressure sensor showing a state in the middle of a silicone gel coating process according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a silicone gel suction device according to an embodiment of the present invention.

FIG. 3 is a diagram showing a coating state after the silicone gel has been sucked out from the state of FIG. 1;

FIG. 4 is a characteristic diagram showing a relationship between a zero-point inclination of a pressure-sensitive diaphragm chip and a thickness of a silicone gel applied to the chip.

FIG. 5 is a characteristic diagram showing a relationship between an output fluctuation error of a pressure sensor and a thickness of a silicone gel applied to a chip.

FIG. 6 is a cross-sectional view of a configuration of a surface pressure type semiconductor pressure sensor showing a conventional silicone gel coating method.

[Explanation of symbols]

 Reference Signs List 1 pressure-sensitive diaphragm chip 2 glass pedestal 3 printed board 4 metal spacer 5 aluminum wire 6 case 6a opening 7 nozzle 8 silicone gel 9 gel discharging collet 10 air hole 11 vacuum pump 12 valve 13 trap 14 vacuum pressure gauge 15 three-way valve

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-1-260337 (JP, A) JP-A-57-82731 (JP, A) JP-A-5-291590 (JP, A) JP-A-5-291590 126662 (JP, A) Japanese Utility Model Showa 61-22369 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01L 9/04 101 H01L 29/84

Claims (3)

(57) [Claims] A pressure-sensitive diaphragm chip is mounted on a printed board, a surface electrode of the pressure-sensitive diaphragm chip is connected to the printed board with a wire, and the pressure-sensitive diaphragm chip and the wire are surrounded on the printed board. Into the assembled state of the case, the silicone gel is injected until the pressure-sensitive diaphragm chip and the wire are buried in the silicone gel layer in the case, and then the silicone gel is sucked out of the case to remove the surface of the pressure-sensitive diaphragm chip and the wire. A method of manufacturing a surface pressure type semiconductor pressure sensor, characterized by applying a silicone gel to the entire surface. 2. The manufacturing method according to claim 1, wherein a gel discharging collet having an air hole on a wall surface is connected to the opening of the case, and the opening of the case is directed downward from the case by a vacuuming method. A method for manufacturing a surface pressure type semiconductor pressure sensor, wherein a silicone gel is sucked out. 3. The method according to claim 1, wherein the silicone gel is sucked out so that the coating thickness of the silicone gel attached to the surface of the pressure-sensitive diaphragm chip and the wire is 30 to 80 μm. Of manufacturing surface pressure type semiconductor pressure sensor.