JP2022134310A - Pressure measuring device - Google Patents

Abstract

To provide a pressure measuring device in which capillaries for pressure guide are soldered to a ceramic sensor case and welded to washers on a body side with good sealing properties.SOLUTION: A sensor case 42 is formed of ceramic material and has first and second openings. A body 12 is provided with first and second stainless steel washers 27, 28 attached to opening ends of first and second pressure guide paths 25, 26, and first and second capillaries 31, 32 that are joined to these washers at one ends and communicating at the other ends with a pressure sensor chip 33 through the first and second openings in the sensor case. Portions through which the first and second capillaries penetrate the sensor case are plated for soldering and soldered to the metallized first and second openings. One ends of the first and second capillaries are not plated for soldering and welded to the first and second washers.SELECTED DRAWING: Figure 2

Description

TECHNICAL FIELD The present invention relates to a pressure measuring device provided with a thin tube for pressure guidance, one end of which is soldered to a sensor case and the other end of which is welded to a member on the body side.

As a conventional pressure measuring device, there is one described in Patent Document 1, for example. The pressure measuring device disclosed in Patent Literature 1 has a sensor chip housed in an internal space on one end side of a body, and includes a narrow tube that guides pressure from a pressure guide path on the other end side of the body to the sensor chip. The other end of the body is provided with a barrier diaphragm that is in contact with the fluid to be measured and a pressure transmission chamber whose wall is part of the barrier diaphragm. The pressure guide path described above communicates the pressure transmission chamber and the thin tube.

The connection between the thin tube and the body can be performed via a metal washer through which the thin tube penetrates, as described in Patent Document 2, for example. The tubule is welded to the washer while being inserted into the through hole of the washer. The washer is welded to the body by resistance welding.
Bonding between the capillary tube and the sensor chip can be performed using an adhesive, for example. When an epoxy-based adhesive is used as the adhesive, it is desirable to cover the sensor chip with a sensor case in order to prevent the adhesive from deteriorating due to moisture absorption. The sensor case is preferably made of ceramics so that the signal extraction structure can be easily formed.

By the way, some recent pressure measuring devices have an overpressure protection mechanism mounted on the sensor chip. In a pressure measuring device having an overpressure protection mechanism mounted on a sensor chip, the pressure transmission path from the pressure receiving portion (barrier diaphragm) to the pressure sensing portion (sensor chip) is also required to withstand high pressure. Therefore, the components (body, washer, thin tube) of the pressure transmission path must be made of high-strength metal such as stainless steel for the purpose of maintaining strength.

If a sensor case made of ceramics covering the sensor chip is provided, the gap where the thin tube penetrates the sensor case is sealed by soldering. For soldering, the sensor case has a conductor formed around the opening through which the thin tube passes, and is metallized with Au using Ni as a base. Similarly, thin tubes are also metallized for soldering. In general, stainless steel is a metal that is difficult to solder, and in order to solder stainless steel, it is necessary to remove the oxide film on the surface. In order to remove the oxide film, it is necessary to use resinous solder or flux, but after soldering, cleaning is required to remove the flux (corrosive component). At the time of cleaning, there is a risk that foreign matter may enter the pressure guide path or may cause a problem such as characteristic deterioration due to foreign matter adhering to the sensor chip. Therefore, in order to avoid the occurrence of such problems, instead of using flux-cored solder or flux, the thin stainless steel tube is Au-plated with Ni as the base, and this Au layer is applied to the metallized portion of the sensor case. Solder to seal the narrow tube penetration.

Japanese Patent No. 5089018 Japanese Patent No. 6559584

However, there is a risk that the thin tube that is Au-plated on a Ni base so that it can be soldered has poor sealing performance at the welded portion with the washer. The reason for this is that P (phosphorus), S (sulfur), etc. contained in the underlying Ni plating components cause weld cracks. This weld crack occurs as shown in FIG. FIG. 9 shows the welded portion where the tip of the thin tube 1 is welded to the opening edge of the through hole of the washer 2 . Cracks caused by weld cracking are formed in this welded portion, as indicated by a rectangular frame in FIG. The crack extends along the boundary between the capillary tube 1 and the washer 2 .

SUMMARY OF THE INVENTION It is an object of the present invention to provide a pressure measuring device in which a thin tube for pressure guidance is soldered to a ceramic sensor case and welded to a washer on the body side with good sealing performance.

In order to achieve this object, the pressure measuring device according to the present invention includes a pressure receiving diaphragm that receives the pressure of the process fluid to be measured, and receives the pressure of a pressure transmission medium filled between the pressure receiving diaphragm and the pressure receiving diaphragm. A pressure measuring device having a body in which a pressure sensor chip for detecting pressure by means of pressure sensor and a sensor case for accommodating the pressure sensor chip are installed in an internal space, wherein the sensor case is made of a ceramic material. and an opening for introducing the pressure of the pressure transmission medium to the pressure sensor chip, and the body is formed with the pressure-receiving diaphragm as a part of a wall to accommodate a part of the pressure transmission medium. A through hole is provided in the internal space of the body, and the opening end of the pressure guiding path communicates with the internal space of the body. a washer made of stainless steel having a A thin tube made of stainless steel filled with the pressure transmission medium is provided in the thin tube, and the portion of the thin tube that penetrates the opening of the sensor case is plated for soldering and metallized A portion of the thin tube that is soldered to the opening and inserted into the through hole of the washer is welded to the washer without being plated for soldering.

In the pressure measuring device according to the present invention, the surface of the thin tube may be plated for soldering except for a joint portion between the washer and the inner peripheral surface of the through hole.

In the pressure measuring device according to the present invention, the thin tube may be joined to the washer and the sensor case while being plated for soldering.

In the present invention, since the portion of the thin tube that penetrates the sensor case is plated with Au, the through portion of the sensor case through which the thin tube penetrates is sealed by soldering. Also, since the portion of the thin tube to be welded to the washer is not plated, the welded portion between the thin tube and the washer will not crack.
Therefore, it is possible to provide a pressure measuring device in which the thin tube for pressure guidance is soldered to the ceramic sensor case and welded to the washer on the body side with good sealing performance.

FIG. 1 is a cross-sectional view of a pressure measuring device according to the invention. FIG. 2 is a perspective cross-sectional view of the pressure measuring device. FIG. 3 is an exploded perspective view showing the body and resin case of the pressure measuring device in a cutaway manner. FIG. 4 is a perspective cross-sectional view of the pressure sensor assembly. FIG. 5 is an enlarged cross-sectional view showing the junction between the sensor case, the pressure sensor chip, and the thin tube. FIG. 6 is a cross-sectional view showing an enlarged joint between the washer and the thin tube. FIG. 7 is a cross-sectional view for explaining the plating range of the thin tube. FIG. 8 is a perspective cross-sectional view for explaining the procedure for welding the washer to the body. FIG. 9 is a microphotograph showing an enlarged welded portion between a washer and a thin tube.

An embodiment of a pressure measuring device according to the present invention will be described in detail below with reference to FIGS. 1 to 8. FIG.
A pressure measuring device 11 shown in FIG. 1 is constructed by assembling a plurality of functional parts, which will be described later, to a body 12 depicted in the center of FIG. The body 12 has a pressure receiving portion 13 drawn on the lower side in FIG. 1 and a detection portion 14 drawn on the upper side. The body 12 according to this embodiment is made of stainless steel. The body 12 according to this embodiment is made of SUS316 stainless steel from the viewpoint of corrosion resistance.

The pressure-receiving portion 13 is formed in a plate shape whose thickness direction is the left-right direction in FIG. A second pipe 16 is connected. The inside of the first pipe 15 is filled with a first process fluid 17 to be measured. The interior of the second pipe 16 is filled with a second process fluid 18 to be measured.
A first pressure-receiving diaphragm 21 for receiving the pressure of the first process fluid 17 is provided at one end of the pressure-receiving portion 13 connected to the first pipe 15, and the first pressure-receiving diaphragm 21 is A first pressure transmission chamber 22 is formed as part of the wall.
A second pressure receiving diaphragm 23 for receiving the pressure of the second process fluid 18 is provided at the other end of the pressure receiving portion 13 connected to the second pipe 16, and the second pressure receiving diaphragm 23 A second pressure transmission chamber 24 is formed in which is a part of the wall.

The first pressure transmission chamber 22 and the second pressure transmission chamber 24 are, as shown in FIG. It communicates with the pressure chamber 34 (see FIG. 5) of the pressure sensor chip 33 via the first and second washers 27 and 28 and the first and second capillaries 31 and 32 of the detection section 14 . A pressure transmission system from the first and second pressure transmission chambers 22, 24 to the pressure chamber 34 is filled with a pressure transmission medium 35 (see FIGS. 1 and 5). The pressure sensor chip 33 receives the pressure of the pressure transmission medium 35 filled between the first and second pressure receiving diaphragms 21 and 23 and detects the pressure.

The detecting portion 14 of the body 12 is formed in a cylindrical shape and opens in the direction opposite to the pressure receiving portion 13 . An internal space 36 of the body 12 is formed within the detection section 14 . A cover 37 (see FIG. 1) is attached to the opening of the detector 14 and closed by the cover 37 .
As shown in FIG. 3, first and second pressure guide paths 25 and 26 are opened at the inner bottom of the detector 14, respectively. The first and second pressure guide paths 25 and 26 are formed inside the body 12 so as to communicate with the internal space 36 of the body 12 from the first and second pressure transmission chambers 22 and 24 .

A first washer 27 is attached to the open end of the first pressure guide path 25 that communicates with the internal space 36, as shown in FIG. A second washer 28 is attached to the open end of the second pressure guide path 26 that communicates with the internal space 36 . The first and second washers 27 and 28 are made of stainless steel and are disc-shaped and welded to the body 12 . The washers 27 and 28 according to this embodiment are made of SUS316, SUS304, etc., which can be welded to SUS316, which is the material of the body 12 .

As shown in FIG. 6, convex portions 27a and 28a facing the inside of the first and second pressure guide paths 25 and 26 are provided at the central portions of the first and second washers 27 and 28, respectively. , through holes 38 and 39 are formed. As shown in FIG. 4, one end of a first thin tube 31, which will be described later, is inserted into and joined to the through hole 38 of the first washer 27. As shown in FIG. One end of a second thin tube 32 to be described later is inserted and joined to the through hole 39 of the second washer 28 .

The first thin tube 31 and the second thin tube 32 are each made of stainless steel and bent into a predetermined shape. The material of the first and second thin tubes 31, 32 is SUS304, which has good weldability with the material (SUS316, SUS304) of the first and second washers 27, 28. The first and second tubules 31 and 32 are joined to the first and second washers 27 and 28 by connecting the outer circumferences of the tip ends of the tubules 31 and 32 to the opening edges of the through holes 38 and 39 that open to the projections 27a and 28a. It is done by welding the parts. As shown in FIG. 6, this welding is performed so that the weld 40 provides a liquid-tight seal between the first and second washers 27, 28 and the first and second tubules 31, 32. there is
A first capillary tube 31 welded to the first washer 27 and a second capillary tube 32 welded to the second washer 28 form part of the pressure sensor assembly indicated at 41 in FIG. It is.

The pressure sensor assembly 41, as shown in FIG. , 32 and a sensor case 42 and a pressure sensor chip 33 . The first and second thin tubes 31, 32 extend from the first and second washers 27, 28 in the direction opposite to the pressure receiving portion 13 of the body 12, and connect the first and second washers 27, 28 and the sensor. The narrow tubes 31 and 32 are bent so that the distance between them and the case 42 is narrowed. The interval between the first and second capillaries 31 and 32 is widened at one end welded to the first and second washers 27 and 28 and narrowed at the other end joined to the sensor case 42 .

The sensor case 42 is composed of a case body 43 made of a ceramic material and a lid body 44 made of a ceramic material or a metal material. The pressure sensor chip 33 is formed in a cubic shape by stacking a plurality of plate-like members made of silicon in the thickness direction, and is accommodated in the sensor case 42 .
A case main body 43 of the sensor case 42 is formed in a bottomed square tube shape that opens toward the upper side in FIG. The lid body 44 is formed in a plate shape and is fixed to the case body 43 by brazing or seam welding in a state of closing the opening of the case body 43 . The operation of joining the lid 44 to the case main body 43 is performed so that the inside of the case main body 43 is airtightly sealed while being filled with vacuum or N ₂ .

On the bottom surface of the sensor case 42, that is, on the outside surface of the bottom wall 43a of the case main body 43, there are a plurality of solderings (not shown) that are electrically connected to the plurality of terminals of the pressure sensor chip 33 individually. land is formed. These soldering lands are soldered over soldering lands 46 formed on a substrate 45 (see FIG. 3). The sensor case 42 is mounted on the substrate 45 by performing this soldering.

The substrate 45 is formed in a disc shape, as shown in FIG. The substrate 45 is formed with two circular through-holes 47, 47 through which the first and second washers 27, 28 can pass, and a slit 48 connecting the through-holes 47 to each other. The work of stacking the sensor case 42 on the substrate 45 is performed by passing the first and second washers 27 and 28 through the through holes 47 and 47 and passing the first and second capillaries 31 and 32 through the slits 48 .

A substrate 45 according to this embodiment is supported by a resin case 51 (see FIG. 3) and supported by the body 12 via the resin case 51 . The resin case 51 is formed in a bottomed cylindrical shape that can be accommodated in the internal space 36 of the body 12 . The resin case 51 has a mounting surface 52 on which the substrate 45 is mounted, claw pieces 53 for mounting and locking the substrate 45 on the mounting surface 52, and first and second washers 27 and 28. Two through holes 54, 54 are formed for passage. Around the through hole 54 are two circular projections 55 projecting from the bottom wall 51a of the resin case 51 downward in FIG. Two cylinders 56, 56 protrude from 51a in the direction opposite to the pressure receiving portion 13 are provided. The circular protrusion 55 fits into a circular recess 57 formed in the body 12 so as to surround the first and second pressure guide paths 25 and 26 . A concave portion 58 for passing the first and second thin tubes 31 and 32 is formed in the cylindrical body 56 .

As shown in FIG. 5, the bottom wall 43a of the case main body 43 is formed with mounting seats 61 (see FIG. 5) for supporting both sides of the pressure sensor chip 33, and the pressure of the pressure transmission medium 35 is transferred to the pressure sensor. First and second openings 62 and 63 (see FIG. 4) are formed for introducing into the sensor chip 33 .
As shown in FIG. 4, the pressure sensor chip 33 has a first hole 64 into which the other end of the first thin tube 31 is inserted and a second hole 65 into which the other end of the second thin tube 32 is inserted. is formed and fixed to the mounting seat 61 of the case body 43 by, for example, brazing. The pressure sensor chip 33 is configured to detect the differential pressure between the pressure of the pressure transmission medium 35 transmitted to the first hole 64 and the pressure of the pressure transmission medium 35 transmitted to the second hole 65. there is

The first and second openings 62, 63 of the case main body 43 are formed to be through holes penetrating the bottom wall 43a. The hole diameters of the first and second openings 62, 63 are such that the other ends of the first and second capillaries 31, 32 can pass through. The other end of the first thin tube 31 passes through the first opening 62 and is inserted into the first hole 64 of the pressure sensor chip 33 to communicate with the pressure sensor chip 33 . The other end of the second thin tube 32 passes through the second opening 63 and is inserted into the second hole 65 of the pressure sensor chip 33 to communicate with the pressure sensor chip 33 .

The first and second capillaries 31 and 32 are adhered to the pressure sensor chip 33 with an adhesive 66, as shown in FIG. As this adhesive 66, an epoxy-based adhesive can be used. The inside of the sensor case 42 is in a state where the epoxy-based adhesive does not absorb moisture. This state is a vacuum state or a state filled with an inert gas such as N ₂ gas. In order to keep the inside of the sensor case 42 in such an inert state, the portions of the first and second narrow tubes 31 and 32 that penetrate through the first and second openings 62 and 63 of the sensor case 42 are soldered. sealed by the adhesive. Soldering is performed so that the solder 67 wets and spreads over the entire area around the first and second openings 62 and 63 .

The first and second openings 62, 63 of the case main body 43 are metallized so as to enable this soldering. Also, the first and second thin tubes 31 and 32 are plated for soldering. This plating for soldering is Au plating with Ni as the base.
Plating for soldering is performed by a so-called partial plating method. Portions of the first and second thin tubes 31 and 32 that require plating for soldering are portions that are inserted into the first and second openings 62 and 63 and soldered, and are shown in region B in FIG. This is the part shown as .
A portion shown as area A in FIG. 7 is a portion to be adhered to the pressure sensor chip 33 . Region A may or may not be plated for soldering.
A portion shown as region C in FIG. 7 is a portion between the soldering portion and the first and second washers 27,28. Region C may or may not be plated for soldering.

A portion shown as region D in FIG. 7 is a portion inserted into the first and second washers 27 and 28 . Region D should be free of plating for soldering.
The first and second capillaries 31 and 32 according to this embodiment are plated for soldering in the regions A, B, and C described above. That is, the surfaces of the first and second tubules 31, 32 are plated for soldering except for the joints with the inner peripheral surfaces of the through holes 38, 39 of the first and second washers 27, 28. It is
The first and second narrow tubes 31 and 32 are joined to the first and second washers 27 and 28 and the sensor case 42 while being plated for soldering.

Next, a procedure for assembling the pressure measuring device 11 configured as described above will be described. When assembling the pressure measuring device 11, first, the first and second capillaries 31 and 32 are plated for soldering. This plating is applied to areas A to C in FIG. Incidentally, metallization is applied in advance to the portions where the first and second openings 62 and 63 of the case main body 43 and the cover 44 are joined.

Then, the first and second washers 27 and 28 are welded to the first and second thin tubes 31 and 32, respectively. After that, the first and second thin tubes 31 and 32 are passed through the first and second openings 62 and 63 of the case body 43 , and the first and second thin tubes 31 and 32 are adhered to the pressure sensor chip 33 . Then, the pressure sensor chip 33 is joined to the case main body 43, and the pressure sensor chip 33 and the conductive portion of the case main body 43 are connected by, for example, bonding wires (not shown).

After the pressure sensor chip 33 is attached to the sensor case 42 in this way, the first and second thin tubes 31, 32 are soldered to the first and second openings 62, 63 of the case body 43, and the thin tubes penetrate through. Seal the part. Then, the case main body 43 and the first and second thin tubes 31 and 32 are loaded into a joining device (not shown), the inside of the case main body 43 is made inactive, and the cover 44 is brazed or seam-welded to the case main body 43. Install by The pressure sensor assembly 41 is completed by joining the cover 44 to the case body 43 .

Next, pressure sensor assembly 41 is attached to substrate 45 . In this mounting operation, the first and second washers 27 and 28 are passed through the through holes 47 of the substrate 45, the first and second thin tubes 31 and 32 are passed through the slits 48, and the sensor case 42 is soldered to the substrate 45. and do. Thereafter, the board 45 is engaged with the resin case 51 and the resin case 51 is inserted into the internal space 36 of the body 12 . At this time, the circular projection 55 of the resin case 51 is fitted into the circular recess 57 of the body 12, and the projections 27a, 28a of the first and second washers 27, 28 are connected to the first and second pressure guide paths 25, 28. 26.

Then the first and second washers 27 and 28 are welded to the body 12 . As shown in FIG. 8, this welding is performed by placing the body 12 on the lower electrode 71 and pressing the upper electrode 72 against the first and second washers 27 and 28 by resistance welding. The upper electrode 72 is rod-shaped, passes through the through hole 54 of the resin case 51 and the circular hole 47 of the substrate 45 and overlaps the first and second washers 27 and 28 . A slit 73 is formed at the tip of the upper electrode 72 for passing the first and second thin tubes 31 and 32 .
After the first and second washers 27 and 28 are welded to the body 12, the pressure transmission medium 35 is filled in the pressure transmission path from the first and second pressure transmission chambers 22 and 24 to the pressure sensor chip 33. . This filling is performed using a filling hole (not shown) extending out of the body 12 from the first and second pressure transmission chambers 22,24.

In the pressure measuring device 11 configured as described above, the portions of the first and second capillaries 31 and 32 penetrating the sensor case 42 are plated for soldering (Au plating with Ni as a base). Therefore, the first and second openings 62, 63 through which the first and second thin tubes 31, 32 of the sensor case 42 pass are sealed by soldering. Also, since the portions of the first and second tubules 31, 32 to be welded to the first and second washers 27, 28 are not plated for soldering, P ( (Phosphorus) and S (sulfur) do not cause cracks in welds. Therefore, weld cracks do not occur in the welded portions between the first and second thin tubes 31 and 32 and the first and second washers 27 and 28 .
Therefore, according to this embodiment, it is possible to provide a pressure measuring device in which the thin tube for pressure guidance is soldered to the ceramic sensor case and welded to the washer on the body side with good sealing performance.

The surfaces of the first and second capillaries 31 and 32 according to this embodiment are plated for soldering except for the joints with the inner peripheral surfaces of the through holes 38 of the first and second washers 27 and 28. It has been subjected. Therefore, the portions not to be plated are only portions on the one end side of the first and second thin tubes 31 and 32, so that partial plating can be easily performed.

The first and second capillaries 31 and 32 according to this embodiment are joined to the first and second washers 27 and 28 and the sensor case 42 while being plated for soldering. Therefore, compared to the case where plating is applied after welding the first and second washers 27, 28 to the first and second thin tubes 31, 32, the reliability of the pressure guiding performance is improved. When welding the first and second capillaries 31 and 32 to the first and second washers 27 and 28, there is a risk that the molten metal will solidify in such a way as to narrow the holes of the capillaries, forming thick-walled portions. There is In other words, when plating is performed after welding, there is a risk that the inside of the narrow tube will be clogged with the plating solution due to the thick portion produced during welding. If the clogged portion made of the plating solution exists in such a state as to clog the pressure guide path in the narrow tube, the pressure cannot be correctly transmitted to the pressure sensor chip 33 . Therefore, by plating before welding, the reliability of the pressure guiding performance can be improved.

In the embodiment described above, an example of performing Au plating with Ni as a base is shown as plating for soldering. However, plating that is easily alloyed with stainless steel and solder includes Sn plating in addition to Au plating on a Ni base.
Also, the first and second thin tubes 31 and 32 must be small pipes having an outer diameter of 30G or less. The reason for this is that if the outer diameters of the first and second thin tubes 31 and 32 are large, repeated application of heat and high pressure will cause the soldered portions and the plated portions of the first and second thin tubes 31 and 32 and the sensor case 42 to be damaged. This is because a stress will be applied to them and they will be destroyed.

REFERENCE SIGNS LIST 11 pressure measuring device 12 body 17, 18 process fluid 21 first pressure receiving diaphragm 22 first pressure transmitting chamber 23 second pressure receiving diaphragm 24 second pressure transmitting chamber , 25... First pressure guide path 26... Second pressure guide path 27... First washer 28... Second washer 31... First thin tube 32... Second thin tube 33... Pressure Sensor chip 35 Pressure transmission medium 36 Internal space 38 Through hole 42 Sensor case 62 First opening 63 Second opening 67 Solder.

Claims (3)

Equipped with a pressure-receiving diaphragm that receives the pressure of the process fluid to be measured,
a pressure sensor chip that receives the pressure of the pressure transmission medium filled between the pressure receiving diaphragm and detects the pressure;
A pressure measuring device having a body in which a sensor case containing the pressure sensor chip is installed in an internal space,
The sensor case is made of a ceramic material and has an opening for introducing the pressure of the pressure transmission medium to the pressure sensor chip,
the body has a pressure transmission chamber formed with the pressure receiving diaphragm as a part of a wall and containing a part of the pressure transmission medium, and a pressure transmission path leading to the internal space of the body;
The internal space of the body includes:
a stainless steel washer having a through-hole attached to an open end of the pressure guide path communicating with the internal space of the body;
One end of the washer is inserted into and joined to the through hole of the washer, and the other end of the washer passes through the opening of the sensor case to communicate with the pressure sensor chip, and the interior is filled with the pressure transmission medium. a stainless steel tubule is provided;
A portion of the thin tube that penetrates the opening of the sensor case is plated for soldering and is soldered to the metallized opening,
A pressure measuring device according to claim 1, wherein a portion of the thin tube inserted into the through hole of the washer is welded to the washer without being plated for soldering. The pressure measurement device according to claim 1,
A surface of the thin tube is plated for soldering except for a joint portion of the washer with an inner peripheral surface of the through hole. In the pressure measuring device according to claim 2,
The pressure measuring device, wherein the thin tube is joined to the washer and the sensor case while being plated for soldering.

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