JP2001059792A - Semiconductor pressure sensor unit and its assembling method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To adopt a one-chip integration type semiconductor pressure sensor and to reduce manufacturing cost by ingeniously absorbing assembly errors even in simple assembly. SOLUTION: In an oilless system pressure sensor unit in which a semiconductor pressure sensor chip 3 mounted to a stem 2 is combined with a metal diaphragm 1, a protrusion 1c for transferring pressure formed in a diaphragm part 1b of the metal diaphragm 1 and a silicon diaphragm 3a are united together by a thermosetting resin adhesive or a fixing agent 6 such as low-fusing-point glass, solder. As a method for assembling the unit, the fixing agent 6 is previously applied between the silicon diaphragm 3a and the tip of the protrusion 1c of the metal diaphragm 1, and a metal housing and the stem 2 are joined together by welding, then heated, cooled, and hardened to join the silicon diaphragm 3a and the tip of the protrusion 1c of the metal diaphragm 1. By this constitution, size and assembly errors which occur in the direction of assembly of each component in the assembled sate of the unit are absorbed by the fixing agent 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor pressure sensor unit formed by combining a silicon diaphragm type semiconductor pressure sensor with a metal diaphragm, and a method of assembling the same.

[0002]

2. Description of the Related Art As is well known, a silicon diaphragm type semiconductor pressure sensor is an element for converting pressure into an electric signal by utilizing the piezoresistive effect of silicon, and is used in various industrial fields mainly for mounting on a vehicle. The pressure sensor for measuring the combustion pressure of an automobile engine has recently been developed.

Since the pressure sensor used for measuring the combustion pressure of the engine is exposed to a corrosive gas of high temperature and high pressure (several MPa to several tens MPa), the silicon diaphragm of the semiconductor pressure sensor chip and the gas to be measured are not exposed. Are separated by a metal diaphragm made of highly corrosion-resistant stainless steel or the like, and the pressure received by the metal diaphragm is transmitted to the silicon diaphragm of the semiconductor pressure sensor chip and measured.

Further, as a method of transmitting the pressure received by the metal diaphragm to the semiconductor pressure sensor chip, an oil sealing method of sealing the oil by sealing oil in the sensor unit and a method of transmitting the pressure by the metal diaphragm and the silicon of the semiconductor pressure sensor chip are described. There is known an oilless system in which a pressure transmitting rod is interposed between a diaphragm and a diaphragm and the diaphragm is mechanically connected.

[0005] Here, the oil-filled type uses a one-chip integrated pressure sensor (a sensing part of a strain gauge resistor, an operational amplifier part, In addition to this, a structure in which all the functions of the adjustment circuit are integrated on a single chip) cannot be used, and the sealing structure of the sealed oil becomes complicated, resulting in high cost of the product.

[0006] In this respect, the oil-less system in which pressure is transmitted via a rod instead of oil can absorb most of the pressure to the metal diaphragm even when the measured pressure is high, and the structure and the sealing surface can be used for oil. It is simpler than the enclosing method.

[0007]

The oil-less pressure sensor unit described above has an advantage that its structure is simple, but has a problem that its assembly requires extremely high assembly accuracy.

That is, in order to correctly transmit the pressure received by the metal diaphragm to the silicon diaphragm of the semiconductor pressure sensor chip via the rod, an error on the order of micron in the direction of the pressure load is not allowed. If there is a slight clearance between the tip of the rod, which is a member, and the silicon diaphragm, pressure measurement cannot be performed. Conversely, if the silicon diaphragm is pushed too much, the sensor output will be excessive, resulting in excessive measurement accuracy and sensitivity. Have a big impact.

As a countermeasure for this, a paper "Development of a combustion pressure sensor for lean-burn engines" (Preprint of the academic lecture of the Society of Automotive Engineers of Japan 924127 (Oct. 1992)
As described in), a metal diaphragm and a stem on which a semiconductor sensor chip is mounted are combined in a slidable manner so as to be slidable in the axial direction, and then a laser welding is performed from a side surface between the metal diaphragm and the stem. An assembly method is disclosed in which welding is performed by applying a preload (initial load in the axial direction) that does not cause the above-mentioned clearance in the operating temperature range to the silicon diaphragm during welding. I have.

However, in the pressure sensor assembly structure and method described above, it is necessary to perform laser welding while adjusting the preload, so that inexpensive resistance welding cannot be used, which increases the assembly cost. The pressure sensor uses a dedicated semiconductor sensor chip which does not use a diaphragm as a pressure detecting element. A general semiconductor piezoresistive pressure sensor (for example, wafer crystal orientation ｛1
00 °, the stress in the direction parallel to the diaphragm surface caused by the deflection of the silicon diaphragm is detected by a diffusion gauge resistance). In this case, the preload is adjusted within a range where the minute and thin silicon diaphragm can bend. In practice, welding work is extremely difficult.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to solve the above-mentioned problems, so that a one-chip integrated semiconductor piezoresistive pressure sensor can be used as a pressure detecting element, and a simple assembling process can be adopted. Accordingly, it is an object of the present invention to provide a semiconductor pressure sensor unit improved so as to effectively absorb dimensions and assembly errors and to reduce manufacturing costs.

[0012]

According to the present invention, in order to achieve the above object, a semiconductor pressure sensor unit is provided with a metal diaphragm integrally formed with a flat diaphragm having a pressure transmitting projection at the center of a cylindrical housing. An assembly consisting of a stem welded and joined to the lower surface of the housing of the metal diaphragm, and a silicon diaphragm type semiconductor pressure sensor mounted on the stem via a pedestal facing the tip of the projection of the diaphragm portion, and processed. As an assembling error absorbing means, a structure is employed in which the tip of the metal diaphragm and the silicon diaphragm are connected to each other with a thermosetting resin adhesive hardened in a unit assembled state or a low-melting glass or solder fixing material. (Claim 1) The method of assembling the metal diaphragm housing to the stem At the stage of the assembling process, a thermosetting resin adhesive or a low-melting glass or solder fixing material is added between the silicon diaphragm and the tip of the metal diaphragm projection, and the metal housing and the stem are welded. After joining, the fixing material is solidified through a heating and cooling process to connect and connect the silicon diaphragm and the tip of the projection of the metal diaphragm (claim 2).
Shall be.

In the process of assembling the pressure sensor unit as described above, when the stem is butted and welded to the metal diaphragm, a thermosetting resin adhesive (uncured) is previously placed between the silicon diaphragm and the tip of the projection of the metal diaphragm. State) or adding a low-melting glass and solder, and in the assembly stage where the metal housing and the stem are welded together, if a thermosetting adhesive is used, it is heated to the curing temperature of the adhesive, In the case of low-melting glass or solder, the thermosetting resin adhesive or the low-melting glass or solder is heated to the melting point and then melted and then cooled to solidify the fixing material. Absorbing assembly errors, the two are properly connected and connected without any clearance between the silicon diaphragm and the projection of the metal diaphragm. The pressure received by the metal diaphragm in condition is to be transmitted correctly silicon diaphragm.

Therefore, as in the above-mentioned conventional pressure sensor unit, a predetermined preload is applied to the pressure sensor chip after adopting a non-slidable soldering connection structure at the connection portion between the housing of the metal diaphragm and the stem. In addition, the resistance welding can be performed by adopting a simple butt-joining structure without requiring a complicated assembly structure and procedure for laser welding, thereby simplifying the structure and the assembly process and reducing the manufacturing cost.

Further, according to the present invention, there is the following specific embodiment. (1) A bonding material (adhesive,
A counterbore serving as a filling pool of low melting point glass and solder is formed so that a high bonding strength can be secured by the anchoring effect of the fixing material.

(2) A thick portion which bulges toward the pedestal is formed at the center portion of the silicon diaphragm, and the stress due to the curing contraction and thermal expansion of the fixing material such as an adhesive is transmitted to the strain gauge portion of the semiconductor sensor chip. Not to be. (Claim 4).

(3) A flange portion for inserting the pressure sensor unit into the outer case and joining by welding is formed at an end of the housing opening of the metal diaphragm remote from the diaphragm portion. The transmission of the stress due to the difference in thermal expansion with the diaphragm to the diaphragm portion is suppressed to prevent the output of the sensor from fluctuating.

(4) A one-chip integrated type in which a sensor unit, a pressure detection circuit unit, and an adjustment circuit unit are integrated on a single chip as a semiconductor pressure sensor is employed to reduce the size and weight of the sensor unit. (Claim 6).

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on illustrated embodiments. The illustrated embodiment is a pressure sensor unit for measuring a gauge pressure. FIG. 1 is a sectional perspective view showing an internal structure of the pressure sensor unit, FIG. 2 is an enlarged view of a main part, FIG. 3 is an external view, and FIG. FIG. 5 is an exploded perspective view, and FIG. 5 is a diagram illustrating a state of attachment to an outer case.

That is, the pressure sensor unit is roughly composed of an assembly of a metal diaphragm 1, a stem 2 welded to the metal diaphragm 2, a semiconductor pressure sensor chip 3 mounted on the stem 2, and a glass pedestal 4 thereof. Have been.

Here, the metal diaphragm 1 is made of a highly corrosion-resistant stainless steel or the like, and has a cylindrical housing 1a and a pressure transmitting portion protruding downward from a center portion of the flat plate diaphragm portion 1b crossing substantially the center of the housing 1a. The projection 1c and the flange 1d projecting in a flange shape from the periphery of the opening end of the housing 1a are integrated, and the measurement pressure is applied to the diaphragm 1b through the opening on the upper surface side. The stem 2 is a dish-shaped body having a hermetic terminal pin 2a insulated with glass or the like on the periphery of the bottom surface. A flange portion 2b protruding from the periphery of the stem 2 is abutted against the housing bottom surface of the metal diaphragm 1 for welding. Projection welding).

On the other hand, the semiconductor pressure sensor chip 3 is a piezoresistive type one in which a sensing unit for strain gauge resistance, an operational amplifier unit, and an adjustment circuit unit (not shown) are integrated on a silicon substrate having a silicon diaphragm 3a formed in the center. This is a chip integrated pressure sensor, which is electrostatically bonded on the glass pedestal 4. In the illustrated example, as shown in FIG. 2, a thick portion 3b bulging to the lower surface side is formed at the center of the silicon diaphragm 3a. The glass pedestal 4 is soldered or bonded to the bottom surface of the stem 2, and the thick portion 3 of the silicon diaphragm 3a is provided on the upper surface thereof.
a counterbore part 4a for escape in a circular shape facing b, and
A counterbore portion 4b is formed as an air supply passage extending in all directions from the counterbore portion 4a.
Atmospheric pressure taken into the stem through a pressure inlet (not shown) opened at the bottom is guided to the lower surface side of the silicon diaphragm 3a. Reference numeral 5 denotes a bonding wire that connects between the semiconductor pressure sensor chip 3 and the terminal pin 2a.

When the pressure sensor unit is assembled, the flange 2b of the stem 2 is overlapped and welded to the lower surface of the metal diaphragm 1, and the tip of the pressure transmitting projection 1c of the metal diaphragm 1 is connected to the semiconductor pressure. The gap between the sensor chip 3 and the silicon diaphragm 3a is
They are connected and fixed by a fixing material 6 such as a thermosetting resin adhesive or low-melting glass or solder.

The pressure sensor unit is fitted into the open end of the cylindrical outer case 7 as shown in FIGS. 5 (a) and 5 (b), and then the flange portion 1d of the metal diaphragm 1 is inserted.
The outer case 7 is sealed by seam welding between the outer case 7 and the opening edge of the outer case 7, and the outer case 7 is attached to a device to be subjected to pressure measurement, for example, an automobile engine, and its combustion gas pressure is measured.
Reference numeral 8 denotes a signal extraction connector of the pressure sensor connected behind the outer case 7.

With this configuration, when measuring the pressure, the measured gas pressure acts on the diaphragm portion 1b through the housing opening surface of the metal diaphragm 1, and the deflection of the diaphragm portion 1b in proportion to the pressure is performed via the pressure transmitting projection 1c. Silicon diaphragm 3 of semiconductor pressure sensor chip 2
Press a to measure the gauge pressure.

Next, a method of assembling the pressure sensor unit will be described. First, a wafer on which a semiconductor pressure sensor chip is fabricated and a wafer for a glass pedestal are electrostatically bonded, and then diced into chips, mounted on the stem 2 and bonded by wires 5. Next, after applying a thermosetting resin adhesive as a fixing material 6 to the tip of the projection 1c projecting from the diaphragm portion 1a of the metal diaphragm 1, the flange portion 2b of the stem 2 is attached to the lower surface of the housing 1a of the metal diaphragm 1. In this state, the two are overlapped and welded to each other by resistance welding. When applying the adhesive to the projection 1c of the metal diaphragm 1,
As shown in FIG. 2, a recessed counterbore 1c-1 serving as a fixing material reservoir is preferably formed at the tip of the projection 1c in advance. Instead of applying the adhesive to the projections 1c of the metal diaphragm 1, it is also possible to apply the adhesive to the upper surface of the silicon diaphragm 3a of the semiconductor pressure sensor chip 2 by a screen printing method or the like. Then, after welding the stem 2 to the metal diaphragm 1, the unit assembly is heated to the curing temperature of the adhesive, and the diaphragm 1 b of the metal diaphragm 1 and the semiconductor pressure sensor chip 2 are joined with the adhesive. Both are mechanically connected.

According to this assembling method, the metal diaphragm 1
The dimensions and assembly errors accumulated in the assembling direction of the parts in the assembled state where the stem 2 is butted and welded to the metal diaphragm 1 are absorbed by the uncured adhesive, and the metal diaphragm 1 after the adhesive is heated and cured. Thus, the clearance between the two can be properly connected without leaving a clearance between the tip of the projection 1c and the silicon diaphragm 3a, or on the contrary, the projection 1c excessively pushing the silicon diaphragm 3a. Also, the connection between the metal diaphragm 1 and the stem 2 can be welded and joined by a simple flange butt and resistance welding method.

Further, in the pressure sensor unit of the illustrated embodiment, the flange portion 1d of the metal diaphragm 1 is provided at the open end of the housing 1a farthest from the diaphragm portion 1b, and as shown in FIG. Is welded between the exterior case 7 and the flange portion 1d. Thus, it is possible to prevent the residual stress at the time of welding and the stress due to the difference in thermal expansion from the outer case 7 from directly acting on the joint between the projection 1c of the metal diaphragm 1 and the silicon diaphragm 3a of the semiconductor pressure sensor chip 3. Therefore, the output fluctuation of the sensor due to this can be suppressed low.

As the fixing material 6 for bonding between the diaphragm portion 1a of the metal diaphragm 1 and the silicon diaphragm 3a of the semiconductor pressure sensor chip 2, low-melting glass, instead of the above-mentioned thermosetting resin adhesive, is used. Alternatively, it can be carried out using solder. In this case, the glass and solder are heated to the melting point to absorb the above-described assembly error, and then cooled to solidify the glass and solder to connect the metal diaphragm 1 and the silicon diaphragm 3a.

[0030]

As described above, according to the present invention, an oilless type pressure sensor unit in which a semiconductor pressure sensor is combined with a metal diaphragm is intended for use with a pressure transmitting projection formed on the metal diaphragm and a silicon. The gap between the diaphragms is connected and connected with a thermosetting resin adhesive or a low-melting glass or solder fixing material that is cured in a unit assembled state. As a method for assembling, the tip of the projection of the silicon diaphragm and the metal diaphragm is used. After the welding is performed between the metal housing and the stem, the bonding material is solidified through a heating and cooling process to form a gap between the silicon diaphragm and the tip end of the projection of the metal diaphragm. By connecting and connecting, the dimensions and assembly errors generated in the assembly direction of each part in the assembly state of the unit can be reduced. It can be absorbed by the adherend, so that the pressure received by the metal diaphragm is transmitted to properly silicon diaphragm during pressure measurement.

Therefore, as in the conventional structure, a solderless connection structure is used in which the housing of the metal diaphragm and the stem having the semiconductor pressure sensor are not slidable, and a predetermined preload is applied to the pressure sensor chip. Without the need for complicated assembly procedures of laser welding, a simple butt-joint structure can be used for resistance welding, which makes it possible to reduce the pressure sensor unit with a simple assembly process and high measurement accuracy. Can be provided at cost.

[Brief description of the drawings]

FIG. 1 is a sectional perspective view showing an assembly structure of a pressure sensor unit according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a main part in FIG.

FIG. 3 is an external view of the pressure sensor unit of FIG. 1;

FIG. 4 is an exploded perspective view of the pressure sensor unit of FIG. 1;

5A and 5B are diagrams showing a state in which the pressure sensor unit of FIG. 1 is mounted on an outer case, wherein FIG. 5A is a side view, and FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal diaphragm 1a Housing 1b Diaphragm part 1c Protrusion for pressure transmission 1c-1 Counterbore part for accumulating adhesive material 1d Flange part 2 Stem 3 Semiconductor pressure sensor chip 3a Silicon diaphragm 3b Thick part 4 Glass pedestal 6 Adhesive material 7 Exterior Case

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F055 AA23 BB20 CC02 DD05 EE14 FF43 FF49 GG01 GG12 GG25 HH05 HH08 4M112 AA01 BA01 CA12 CA15 CA16 DA18 EA02 EA14 FA09 GA01

Claims (6)

[Claims] 1. A metal diaphragm in which a plate diaphragm having a pressure transmitting projection is integrally formed at the center of a cylindrical housing, a stem which is welded and joined to the lower surface of the housing of the metal diaphragm, and a projection end of the diaphragm portion. It is an assembly of a silicon diaphragm type semiconductor pressure sensor mounted on the stem via a pedestal, and as a means for absorbing size and assembly errors, a unit assembly state is provided between the tip of the metal diaphragm projection and the silicon diaphragm. A semiconductor pressure sensor unit, which is connected and connected with a thermosetting resin adhesive cured with a low-melting glass or a solder fixing agent. 2. A method for assembling a pressure sensor unit according to claim 1, wherein a thermosetting material is provided between the silicon diaphragm and the tip of the projection of the metal diaphragm at the stage of assembling the stem against the housing of the metal diaphragm. A resin adhesive or a low-melting glass or solder fixing material is added, and after welding and joining between the metal housing and the stem, the fixing material is solidified through a heating and cooling process to form a silicon diaphragm and a metal diaphragm. A method for assembling a semiconductor pressure sensor unit, wherein the semiconductor pressure sensor unit is connected to a tip of a projection. 3. The semiconductor pressure sensor unit according to claim 1, wherein a counterbore serving as an accumulation of fixing material is formed at the tip of the projection of the metal diaphragm. 4. A semiconductor pressure sensor unit according to claim 1, wherein a thick portion bulging toward the pedestal is formed at a center portion of the silicon diaphragm. 5. A semiconductor device according to claim 1, wherein a flange portion for fitting said pressure sensor unit into an outer case and joining it by welding is formed at an end of a housing opening of said metal diaphragm. Pressure sensor unit. 6. The pressure sensor unit according to claim 1, wherein the semiconductor pressure sensor is a one-chip integrated type in which a sensor unit, a pressure detection circuit unit, and an adjustment circuit unit are integrated on a single chip. Semiconductor pressure sensor unit.