JPH03162676A - Liquid-sealed semiconductor device - Google Patents

Abstract

PURPOSE:To eliminate restrictions on the fitting direction of a package and to obtain high airtightness in severe use environment by providing a deformable part in an airtightly sealed package and filling the package with liquid. CONSTITUTION:A detecting element 5 is mounted on a cantilever 4 which has weld zones 21a and 22a at its outer peripheral part and the package consists of a base 21 where lead terminals 7 are led out and a cap 22 provided with the deformable part 22b. Then the package is filled with the damping liquid 10 and the weld zones 21a and 22a are welded airtightly. Then the expansion and contraction of the damping liquid 10 due to variation in the ambient temperature are conducted by the deformation of the deformable part 22b to reduce an increase and a decrease in pressure due to the expansion and contraction. Therefore, the restrictions on the fitting direction can be eliminated by the device which is joined airtightly and filled with the damping liquid 10 to simplify the manufacture process and reduce the cost.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a semiconductor device, such as a semiconductor acceleration sensor, in which a semiconductor element part is mounted in a package, filled with liquid, and sealed.
The present invention relates to liquid-sealed semiconductor devices.

[Conventional technology]

A semiconductor acceleration sensor will be described as a semiconductor device that is mounted in a package, filled with liquid, and sealed.

Conventionally, semiconductor acceleration sensors have a sensing section with a cantilever structure, and damping fluid is used as a mechanical high-cut filter to prevent damage due to resonance of the cantilever and response to unnecessary frequency input. ing.

A cap was screwed to the base of a package equipped with the sensing section of a semiconductor acceleration sensor, and damping liquid was sealed inside.

However, when detecting the acceleration of automobiles, etc. using a semiconductor acceleration sensor, the ambient temperature ranges from -40' to +120°C, and due to the expansion and contraction of the damping fluid in that dryness range, the gap between the base and the cap may leak. Damping fluid leaks. Therefore, it is necessary to provide a highly airtight package that will not allow the damping liquid to leak even under severe usage conditions.

To address this problem, there is a conventional semiconductor acceleration sensor disclosed in, for example, Japanese Patent Application Laid-Open No. 63-88408.

14 and 15 are a perspective view of a conventional semiconductor acceleration sensor before the package is hermetically sealed, and a sectional view of the package after the package is hermetically sealed. In the figure, {1} is a base made of metal etc. and has a welded part (]a) formed on the outer periphery; (2) is a cap made of metal etc. and has a welded part (2a) formed on its outer periphery; Base {1) constitutes a package. The cap (2) has injection JL (2b
) and air holes (2C) are provided, and a partition wall (2d) is provided inside.
is formed. (3) is a pedestal fixed on the base (11), and (4) is a cantilever beam whose one end is joined to the pedestal 13 and the other end is a free end, and forms a sensing section. (4a
) is a stopper that is joined to the base (1) and limits the vibration excursion of the free end of the cantilever beam (4),
), a semiconductor strain gauge is formed by thermal diffusion or ion implantation, and is electrically connected by wiring formed by aluminum evaporation, etc.
Configure a full bridge circuit. (6) is a cantilever beam (
4) a weight formed by a solder layer on the free end, (7)
is the base] 1) The lead terminal passed through the base and exposed to the outside, (
8) is the hard glass filled between the outer periphery of the lead terminal and the through hole, and (9) is the lead terminal {7) and the detection element {5
) is wire-bonded to a wire made of gold wire or aluminum wire, αω is a damping liquid made of silicone oil etc. sealed in the package, and (11) is about 20 to 30% of the package volume remaining in the package.
(The position of the air layer (11) is shown when the package is placed with the A side facing upward).

In this way, the semiconductor acceleration sensor is housed and sealed by the package as follows. First, the pedestal (3)
The welded part (2a) of the cap (2) is attached to the welded part (1 m) of the base +11, which is joined and the cantilever beam (4) is attached.
are electrically resistance welded and hermetically sealed. After this, fill the injection hole (2
b) Damping liquid from approximately 70~ of the package internal volume
Inject 80%. At that time, the air inside the package is released to the outside through the air hole (2c), and the air layer (approximately 20 to 30%) is
l1) remains in the package.

Next, the injection hole (2b) and the air hole (2c) are sealed with solder, and the damping liquid (GO) is placed inside the package.
and the remaining air space (11) will be enclosed.

The semiconductor acceleration sensor configured in this manner is installed in an automobile or the like with the A side facing upward and the air layer (1l) positioned above. When acceleration is applied to the free end of the cantilever beam (4), the resistance value of the semiconductor strain gauge changes, an unbalanced voltage is generated in the full bridge circuit, and the detected acceleration is detected according to the voltage value.

Furthermore, in semiconductor acceleration sensors installed in automobiles, etc., the ambient temperature changes over a wide range of -40°C to +120°C, but since an air layer (11) remains inside the package, the ambient temperature changes with the temperature change. Even if the damping liquid expands or contracts, it will be absorbed by the air layer (1l), and the increase or decrease in pressure inside the package will be alleviated, and the welded part (lm) will be absorbed.
There was no leakage of damping fluid 0ω from , (2b), etc., and the package was highly airtight. Furthermore, the partition wall (2d) inside the package is provided to prevent the ripples and bubbles of the damping liquid αα caused by the remaining air layer (11) from affecting the cantilever beam (4), which may cause noise. It prevents

[Problem to be solved by the invention]

In the conventional semiconductor acceleration sensor as described above, as shown in Fig. 7, it must be installed with the A side of the package facing upward, the sensing part at the bottom, and the air layer (11) facing upward. The problem was that it was limited.

Furthermore, there is a process of forming an air layer (1l) inside the package, and a capping process (2) of partition walls (2d) for noise reduction.
There were problems in that the manufacturing process was complicated and the price of the product increased.

This invention was made to solve these problems, and provides an inexpensive liquid-sealed semiconductor device that has no restrictions on the direction in which the package can be attached, has a package that is highly airtight even under harsh usage environments. The purpose is to

[Means to solve the problem]

A liquid-sealed semiconductor device according to the present invention is hermetically sealed with a package consisting of a base on which a semiconductor element part is attached and lead terminals are exposed to the outside, and a cap that is bonded to the base and covers the semiconductor element part. The package is filled with liquid and has a deformable part.

[Effect]

In this invention, when the environmental temperature changes and the liquid filled in the package expands or contracts, it is released by deforming the deformable part of the package, and the increase or decrease in pressure due to the expansion or contraction of the liquid in the package is alleviated. Ru.

〔Example〕

1 and 2 are a perspective view of a liquid-sealed semiconductor device according to an embodiment of the present invention before the cap is bonded, and a sectional view of the liquid-sealed semiconductor device after completion. Indicate the case.

In the figure, (21) is copal, 42 alloy, SPC
The base (22) has a welded part (21) on the outer periphery, and has a plate thickness of approximately 0.1 to 0. The cap is made of a diaphragm made of 5 am Kovar, 42 alloy or stainless steel, and has a welded part (220) on the outer periphery and a deformable part (22b), which is connected to the base (21). The package is configured such that the deformable portion (22b) of the cap (22) deforms in response to changes in the pressure of the damping liquid α0) filled in the package.

On the base (1) is a pedestal (3) made of silicon etc.
However, they are joined using epoxy or silicone adhesives, brazing, etc.

The pedestal {3} has a cantilever beam (4) made of silicon etc.
One end is joined by anodic bonding or low melting point glass, and the other end is free. The cantilever beam (4) has
In order to increase the acceleration detection sensitivity near the fixed terminal, an etched thin wall portion (40) is formed.
A detection element (5) is formed in 40. In this detection element (5), a semiconductor strain cage is formed in a semiconductor processing process using impurity diffusion of semiconductor planar technology or ion implantation method, and is electrically connected by a p1 high concentration region, wiring made of aluminum vapor deposition, etc. It constitutes a full bridge circuit. (6) Solder, Kovar, 42
A weight made of alloy, Au, etc., and bonded on the free end of the cantilever (4).

A lead terminal (7) passes through the base (21) and is brought out to the outside, and hard glass (8) is filled between the periphery of the lead terminal (7) and the through hole of the base (21) to fix it. It is also electrically insulated. The lead terminal (7) and the electrode of the detection element (5) are wire-bonded with a wire (9) made of aluminum wire, gold wire, or the like.

The package is filled with a damping liquid made of silicone oil and sealed.

Next, the process of filling and sealing the damping liquid OIlm into the package will be explained in order with reference to FIGS. 3(a) to 3(e). First, as shown in Figure 3(a), the cap (
22) with its opening facing upward and filled with damping liquid Ql using a syringe (23).

Next, as shown in Fig. 3(b), the base (21), which has the cantilever beam (4) joined to the pedestal (3), is inserted into the cap (22) filled with damping liquid to prevent air bubbles from entering. Insert it like this. At this time, the damping liquid αω in the cap (22) overflows in an amount equal to the volume of the components mounted on the base (21) and is discharged to the outside, and the package is filled with damping liquid without containing any air bubbles. be done.

Therefore, as shown in Fig. 3(e), the welded part (21a) of the base (21) and the welded part (22a) of the cap (22) are airtightly welded using a spot welder, a parallel seam sealer welder, etc. Then the assembly is completed.

The inventors found that when the cap (22), which deforms in response to changes in the internal pressure of the package, is made of Kovar, 42 alloy, or stainless steel, the thickness is approximately 0.1 to 0.2 mm.
The experimental results showed that this is suitable. In other words, if the thickness is less than about 0.1 mm, electrical welding with the base (21) will be very difficult, and the welded part (22a) will melt during welding, causing liquid leakage from the welded parts (21m) and (22m). There is a risk. Furthermore, if the thickness is 0.3+mm or more, the package will not easily deform due to expansion and contraction of the liquid, and the welded parts (21m) and (22a) will be strained and deteriorated, eventually causing liquid leakage.

In the semiconductor acceleration sensor of the embodiment configured as described above, the cantilever 1. When acceleration is applied to the free end of J-Li (4), the resistance value of the semiconductor strain i-gauge changes, an i-balanced voltage is generated in the full bridge circuit, and the detection acceleration is detected according to the voltage value.

Moreover, the semiconductor acceleration sensor of the above embodiment has +! Since there is no air layer (eye) in the package like in conventional devices, there is no restriction on the mounting direction C to a car, etc., and the same structure can detect accelerations in the front and back, 1f1 right, and up and down directions. Furthermore, the ambient environment temperature is -40℃ to +12℃.
Even under strict usage regulations of 0°C, damping due to temperature changes (101 9) Pressure changes inside the package due to expansion and contraction will cause the Yip (22) to deform due to pressure changes. , the increase and decrease in the pressure inside the package is alleviated, and even though the package is filled with damping liquid (101), the welded part (lm) , (
2b) is not a burden and airtightness can be maintained.

In this way, the process of forming the air layer (11) and partition wall (2d) provided in the conventional device is omitted, and the manufacturing process is simplified.

FIG. 4 is a sectional view showing another embodiment of the invention. In the figure, (24) is a cap, and a thin deformable part (25) is formed on the upper part. This deformable part (2
5) is formed by pressing a part of the upper part of the cap (24), or by providing a window part in the upper part of the cap (24) and airtight welding a thin plate material to the window part B. do.

In the embodiment shown in FIG. 1 above, the welded portion (
22&) is thinner than about 0.1 mm, the bey. (21
) melted during welding with the welded part (2 1 m), and a highly airtight package could not be obtained. However, this fourth
In the illustrated embodiment, the weld part (24a) of the cap (-20)
The thickness of the package can be increased and a highly airtight package can be obtained.

Furthermore, when the deformable part (25) is formed by press working, the thickness can be made thinner than 0.1 mm,
Deformation due to pressure changes becomes easier.

Note that the shape of the deformable portion (25) may be a waveform as shown in FIG.

FIG. 6 is a sectional view showing still another embodiment of the present invention. The cap (27) has a thin deformable portion (27
A cap (2
Overlap the welded part (27a) of 7) and place the auxiliary ring (
28) and weld IIs through the auxiliary ring (28).
(27m) and the welded part (26a) are welded. Even if the thickness of the cap (27) made of Nyorico Pearl, 42 alloy, and stainless steel is made thinner than about 0.1+am, welding can be performed.

FIG. 7 and FIG. 8 are a perspective view of a state before the cap is joined and a sectional view of the cap after completion, showing still another embodiment of the present invention, in which the deformable part is an elastic body with gas sealed inside. It shows a case.

In the figure, (12) is a rubber elastic body (rubber balloon) that contains an air layer (11) inside and is installed inside a cap (22), and is made of highly oil-resistant rubber to prevent swelling caused by the internal liquid. It is attached within the cap (22) with an elastic adhesive (13) or the like. Rubber elastic body (l2
) is preferably a Si-based material or a fluorine-based material that does not lose its elasticity over a wide temperature range.

Next, the process of hermetically sealing the package will be explained in order based on FIGS. 9(&) to (e). First, as shown in FIG. 9(0), the opening of the cap (22) is turned upward, and the damping liquid (101) is filled into the cap (22) by injection M (23).Next, as shown in FIG. As shown in b), a base (21) on which a cantilever {4}, a pedestal (3), etc. are formed is attached to a cap (2) to which an elastic body (12) is attached and which is filled with damping fluid. Insert into.

At this time, defoaming is performed as necessary. Next, Figure 9(e)
As shown in , the package is completed by welding the welded parts (21a) and (22a) of the base (21) and cap (22) using a spot welder, a parallel seam sealer welder, or the like.

The acceleration detection operation of the semiconductor acceleration sensor configured in this way is similar to the conventional example and the embodiment shown in FIG. As shown in the inside of the package, an elastic body (12) containing an air layer (11) is installed inside the package, so there is no freely movable air layer left as in the conventional example, and damping fluid Since the position of the air layer (11), which can be deformed according to the expansion and contraction of 001, can be restricted and fixed, there is no restriction on the direction in which it can be installed in a car;
Horizontal and vertical acceleration can be detected using the same structure, and there is no rippling or bubbles in the damping fluid that can cause noise. Furthermore, under severe usage conditions where the ambient temperature ranges from -40°C to +120°C, pressure changes inside the package due to expansion and contraction of the damping liquid due to temperature changes can be prevented by an elastic body (12) with an air layer (1 liter). changes due to pressure changes, the increase and decrease in pressure inside the package is alleviated or eliminated, and even though the package is filled with liquid GO+, the welded part (21m) (2
2m), there is little or no burden, and the package can be held with high airtightness.

In addition, an air layer (11) to be secured inside the cap (22)
is desirably determined with reference to the operating temperature range and the volumetric expansion coefficient of the liquid QOI to be sealed.

FIGS. 11 to 13 each show still other embodiments of the present invention, which differ from the embodiment shown in FIG. 7 in that the form of the elastic body installed in the package has been changed. .

Figure 11 shows an example in which a highly foamed sponge such as silicone rubber, fluororubber, or natural rubber is used as the elastic body (12).
It has independent air bubbles (l1) and is effective in alleviating and eliminating internal pressure. Fig. 12 shows a structure in which 14 membranes (l2) of rubber elastic body are attached to the inside of the cap (22) by baking or gluing, and Fig. 13 shows a structure in which 14 membranes (12) of rubber elastic body are pasted inside the cap (22) by a method such as baking or gluing. With air layer (11)) and cap (2
2) It is joined inside.

In addition, in order to prevent the airtightness of the welded parts of the package from worsening due to an increase in internal pressure due to thermal expansion of the damping liquid 00), the temperature of the damping liquid should be raised to the upper limit of the operating temperature range beforehand during assembly. In this state, the cap and the package may be hermetically welded at the welding portion.

In the above embodiment, the opening of the cap is directed upward, filled with damping liquid, and the base is fitted and welded from above, but the cap is not limited to this, and the following method may be used. For example, similar to the conventional device, an injection hole and an air hole are provided in the cap, and the damping liquid
), let the remaining air escape from the air hole, inject damping liquid QOI until it overflows from the air hole, fill the package with damping PFloo+, and seal the injection hole and air hole with solder, etc. Good too.

Further, the deformable parts of the package and the cap are not limited to metal, and may be made of, for example, soft heat-resistant plastic, rubber, etc., and any materials suitable for their respective functions can be used.

Furthermore, in the above embodiment, a semiconductor acceleration sensor was described as a semiconductor device, but semiconductor elements such as a signal detection element and an electric signal processing element made of semiconductor are housed in a package, and in addition to damping liquid, insulating oil (electrical It can also be applied to devices in which a pressure transmission medium liquid, etc. is sealed in the package. The frequency range of the pressure that can be transmitted can be set by selecting the constant) and the viscosity coefficient.

〔Effect of the invention〕

As described above, according to the present invention, a package is constructed by airtightly fitting a cap to a base on which a semiconductor element is mounted, and the package is filled with liquid, and the package responds to changes in the pressure of the liquid. Since the deformable portion is provided, the airtightness of the package can be maintained even under harsh usage environments, and the manufacturing process can be simplified and reduced in cost. Furthermore, the mounting direction on the device to be used is not restricted.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a semiconductor acceleration sensor showing an embodiment of the liquid-sealed semiconductor device according to the present invention before the cap is bonded;
Figure 2 is a cross-sectional view taken along the line ■--■ in Figure 1, showing a state in which the cap is joined to the base in Figure 1 and the inside is filled and sealed, and Figure 3 is a cross-sectional view taken in the direction of the line (a) to (e). Cross-sectional views showing the semiconductor acceleration sensor in FIG. 1 in the order of manufacturing steps, FIGS. 4 to 6,
8 and 11 to 13 are sectional views showing other embodiments of the present invention, FIG. 7 is a perspective view of the embodiment shown in FIG. 8 before the cap is joined, and FIGS. 9(a) to 13 are (e) is a cross-sectional view showing the semiconductor acceleration sensor of FIG. 8 in the order of manufacturing steps, and FIGS. 14 is a perspective view of a conventional semiconductor acceleration sensor before the cap is bonded, and FIG. 15 is a perspective view of a conventional semiconductor acceleration sensor before the cap is bonded.
FIG. 3 is a cross-sectional view taken along the line v-xv. (4) Semiconductor element part (cantilever), (51-detection element, (7) Lead terminal, 00 Liquid (damping liquid), <11) Air layer, (12) Elastic body , (21
) Heath, (21a)... Welded part, (22)... Cap, (22a)... Welded part, (22b) Deformable part, (
24) Cap, (24m) Welded part, (25
)・Deformable part, (26)・Base, (26a) Welded part, (27)・Cap, (270 Welded part, (27b)
Deformable part. Note that the same symbols in the figures indicate the same or equivalent parts.

Claims (2)

[Claims] (1) A package consisting of a semiconductor element part, a base on which the semiconductor element part is mounted and a plurality of lead terminals extended to the outside, and a cap that covers the semiconductor element part and is hermetically sealed to the base; 1. A liquid-sealed semiconductor device comprising a liquid filled with the liquid, the package further comprising a deformable portion that deforms in response to changes in the pressure of the liquid and alleviates increases and decreases in pressure. (2) The liquid-sealed semiconductor device according to claim 1, wherein the deformable portion is an elastic body disposed within the package and having a gas sealed inside.