JPS6153875B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor pressure transducer,
In particular, the present invention relates to a semiconductor pressure transducer with improved adhesive fixation between a pressure receiving base and a metal frame of a silicon diaphragm type pressure transducer that acts as a diaphragm.

In general, semiconductor pressure transducers that use the piezoresistance effect of semiconductors to convert pressure into electrical quantities are well known, and one type of such transducers is the so-called silicon diaphragm pressure transducer. It is being This silicon diaphragm type pressure transducer has a structure in which a pressure-sensitive silicon diaphragm is placed on a pressure receiving stand and bonded to the frame. It is required that the layer has sufficient rigidity, that it does not deform due to pressure or temperature (below 150°C), and that residual strain after bonding is small.

However, in the pressure receiving part of the silicon diaphragm type pressure transducer proposed in the past, the silicon diaphragm is bonded to a pressure receiving base made of crystallized glass using low-melting glass, and the pressure receiving part is attached to a metal frame that can be easily heat-processed. Since it is used in a manner in which it is adhesively fixed with an organic adhesive, the organic adhesive is exposed to chemical gas during use, and therefore it is difficult to obtain stable and highly reliable pressure conversion characteristics. It was hot. Furthermore, conventional bonding methods using organic adhesives require careful attention and thoroughness in bonding operations such as surface treatment of the frame, bonding pressure, and aging, and if there are deficiencies in the work management, the bonding However, there were disadvantages such as incomplete conversion, lower manufacturing yield, and drift in conversion characteristics.

In addition, recently, pressure transducers have been known that have improved airtightness and chemical resistance by bonding the pressure receiving base to the frame with low melting point glass. This installation is done at a high temperature of around 500 degrees in order to melt and bond once. Therefore, when the temperature is returned to normal room temperature, residual strain remains between the pressure receiving base and the frame, and this effect is noticeable in the pressure measurement value of the pressure transducer even when the temperature changes during use. There is.

In order to eliminate the drawbacks of the conventional example described above, the present invention has provided that a pressure receiving table on which a strain sensing element is mounted at the center of a flat protrusion protruding from the upper surface of the frame is bonded to the frame with solder. The purpose of this is that since the melting temperature of the solder is around 200°, almost no residual strain remains even when the solder is returned to room temperature after bonding, and it is not exposed to chemical gases, etc., and is airtight. The present invention provides a semiconductor pressure transducer that can maintain its properties. The structure of the present invention includes a pressure-sensitive element formed with a strain-sensitive element in the center of its surface, an electrode around it, and a transmission part connecting the strain-sensitive element and the electrode; a pressure receiving base having a predetermined through hole at a position facing the pressure element; a low melting glass layer adhesively fixing the pressure sensitive element and the pressure receiving base; It has a metal film layer formed to surround the through hole, and a pressure inlet facing the through hole of the pressure receiving table and communicating with the outside air, and the periphery of the pressure inlet protrudes and the upper surface thereof is flat. A frame body provided with a protruding part whose area is about 15 to 60% of the area of the pressure receiving table, and a solder layer that adhesively fixes between the metal film layer of the pressure receiving table and the protruding part of the frame body. It is. Hereinafter, embodiments will be described in detail with reference to the drawings.

1 to 3 show one embodiment of the present invention, in which 1 is a silicon pressure-sensitive element that converts pressure into a pressure signal, 2 is a silicon pressure-sensitive element that has a through hole 2', and has a thermal expansion coefficient of silicon. This is a pressure receiving stand made of crystallized glass similar to the above, and the pressure sensitive element 1 is adhesively fixed with a 3 to 15 micron low melting point glass layer. A nickel plating film 3 of 2 to 5 microns is formed partially or entirely around the through hole 2' on the back surface of the pressure receiving table 2. 4 are fixing holes 4a to 4 through which the leads 5a to 5f are fixed.
4f, and leads 5a to 5f are inserted into the fixing holes 4a to 4f, respectively, and fixed by insulating ceramics 6.
a to 5f are connected to the aluminum electrodes of the pressure sensitive element 1 by bonding wires 7, respectively. In addition, a pipe 10 is inserted into the through hole 9 provided in the center of the metal frame 4.
is fixed and pressure is introduced. Also, the metal frame 4
A protrusion 11 is provided around the through hole 9 on the upper surface, and a solder layer 12 of 100 to 250 microns is formed on the flat upper surface of the protrusion 11 to bond and fix the pressure receiving table 2 and the metal frame 4. To do this, press the pressure receiving base 2.
The plating film 3 is placed on top of the solder layer 12, and approximately
By heating at a temperature of 200 to 250° C., the plating layer 3 of the pressure receiving table 2 and the protruding portion 11 of the metal frame 4 are firmly bonded.

By the way, the adhesive area of the solder layer 12 depends on the force generated by the pressure acting on the diaphragm portion of the silicon pressure-sensitive element 1, so it depends on the measurement pressure range of this pressure transducer, the area of the diaphragm, and The bonding ratio of the minimum bonding area is inevitably determined by the bonding strength of the solder. Therefore, since the inner diameter of the protrusion is determined by the diameter of the through hole provided in the metal frame, the outer diameter of the protrusion can be calculated based on the above-mentioned minimum joint area. On the other hand, the bonding ratio for the maximum bonding area is the bonding ratio when everything except the through hole on the back side of the pressure receiving part is bonded to the top surface of the metal frame. Therefore, the bonding ratio of the protrusion was determined to be 15 to 60% of the bonding ratio of the maximum bonding area.

The semiconductor pressure transducer of this embodiment configured in this way changes the electrical resistance of the diffusion resistor provided in the diaphragm of the silicon pressure-sensitive element in accordance with the pressure applied to the silicon pressure-sensitive element. Bonding wire 7, leads 5a to 5f to measure resistance changes
By detecting the voltage via the pressure sensitive element, an amount of electricity corresponding to the pressure applied to the pressure sensitive element can be obtained. In addition, a protrusion 11 with a flat upper surface that protrudes concentrically with the through hole 9 formed in the center of the metal frame 4 is formed on a part or the entire surface of the back surface of the pressure receiving table 2 around the through hole 2'. Since it is adhesively fixed to the plated film 3 via the solder layer 12, this adhesive area can be made small, so that the occurrence of residual strain after adhesively fixing and thermal strain due to changes in ambient temperature can be made to a level that does not pose a practical problem. can.

A specific example will be explained in order to confirm the effects of the present invention. First, a nickel plating film 3 was applied to all surfaces of the pressure receiving table 2 except for the through holes on the back side using an electroless plating method.
was formed to a thickness of 5 microns. On the other hand, on the upper surface of the metal frame 4, there is a metal protrusion 11 having the same inner diameter as the through hole 9 into which the pressure introduction pipe 10 is inserted, and having various outer diameters smaller than the area of the plating layer 3 of the pressure receiving table 2. The frame 4 was formed using various mechanical methods. Thereafter, a solder layer 12 was formed on the protrusion 11 to a thickness of 200 microns. The aforementioned pressure receiving base 2 having the plating layer 3 is placed on the solder layer 12, heated to 250°C, the pressure receiving base 2 and the metal frame 4 are adhesively fixed with this solder layer 12, and the silicon pressure sensitive element 1 is further fixed. A pressure transducer was completed by connecting the aluminum electrode and the lead 5 with a bonding wire 7.

FIG. 4 shows the correlation between the bonding ratio of the area of the protrusion 11 of the metal frame 4 to the area of the back surface of the pressure receiving table 2 excluding the through hole and the amount of residual strain of the silicon diaphragm in this specific example. , the residual strain can be ignored in a range where the bonding ratio of the area of the protrusion 11 is within 60% of the bonding ratio of the maximum bonding area, but at a bonding ratio of a larger area, the residual strain increases as the residual strain increases. As shown in Figure 5, a decrease in the output of the pressure transducer was observed, and the effect of rapid changes in ambient temperature on the performance of the transducer was observed. In addition, in FIG. 5, the output change rate is set to 100% as the output before soldering.

In the above embodiment, the protrusion 11 was formed on the metal frame 4, but on the contrary, a plating layer was selectively formed around the through hole 2' on the back surface of the pressure receiving table 2, and a solder layer was used to form the protrusion 11 on the metal frame 4. It may be fixed to the metal frame 4 by adhesive. Further, the pressure receiving table on which the silicon pressure-sensitive element is mounted may be made of insulating ceramics other than crystallized glass as long as it has a coefficient of thermal expansion approximately equal to that of the silicon pressure-sensitive element. In addition, the plating layer on the bottom surface of the pressure receiving table is not limited to nickel, but may also be made of materials that are compatible with solder, such as Au, Ag, or Cu, by means such as vapor deposition.
It is also possible to mask the adhesive surface other than the required adhesive surface so that it is not formed. Kovar is used for the metal frame because it is easy to process, but other frames such as cordierite may also be used; in this case, a thin film layer that is compatible with solder is required on the adhesive surface of the frame. Become. In addition, in the above example, the thickness of the solder layer is 200 microns, but if it is thin, the adhesiveness and airtightness will be poor, and if it is too thick, the solder will be affected.
Approximately 50 to 500 microns is appropriate.

As explained above, according to the present invention, the silicon pressure-sensitive element is bonded and fixed to crystallized glass with low melting point glass, thereby maintaining airtightness and stability between the pressure-receiving base and the silicon pressure-sensitive element, and also maintaining pressure-receiving stability. To fix the table to the metal frame, use a solder with a low melting temperature and good wetting properties to maintain the airtightness between the pressure plate and the metal frame and the adhesive strength necessary to fix the pressure plate. By obtaining this, it is possible to provide a semiconductor pressure transducer that has chemical resistance, high performance, and excellent stability.

[Brief explanation of the drawing]

FIG. 1 is a top view of one embodiment of the semiconductor pressure transducer of the present invention, FIG. 2 is a sectional view of FIG. 1, FIG. 3 is a partially enlarged view of FIG. 2, and FIG. , a graph showing the correlation between the solder bonding ratio of the metal frame to the pressure receiving base of a pressure transducer and residual strain, and Figure 5 shows the correlation between the bonding ratio of the metal frame to the pressure receiving base of the pressure transducer and output change. This is a graph showing. 1... Silicon pressure sensitive element, 2... Pressure receiving stand, 2'
...Through hole, 3...Plated layer, 4...Metal frame, 4
a to 4f...fixing hole, 5a to 5f...lead, 6
... Adhesive, 7 ... Bonding wire, 9 ... Through hole, 10 ... Pipe, 11 ... Protrusion, 12 ...
...Solder layer.

Claims (1)

[Claims] 1. A pressure-sensitive element having a strain-sensing element in the center of its surface, an electrode around it, and a transmission part connecting the strain-sensing element and the electrode, and a strain-sensing element of the pressure-sensitive element. a pressure receiving base having a predetermined through hole at a position facing the pressure sensing element; a low melting glass layer adhesively fixing the pressure sensing element and the pressure receiving base; It has a metal film layer formed to surround the through hole, and a pressure inlet facing the through hole of the pressure receiving table and communicating with the outside air, and the periphery of the pressure inlet protrudes and the upper surface thereof is flat. Consisting of a frame body provided with a protrusion whose area is about 15 to 60% of the area of the pressure receiving table, and a solder layer that adhesively fixes between the metal film layer of the pressure receiving table and the protruding part of the frame body. A semiconductor pressure transducer featuring: