JPS6365900B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for vacuum sealing a capacitive pressure capsule.

The integration of a pressure sensor into a vehicle's electronic control system places some stringent requirements on the operation of the pressure sensor. These requirements become even more stringent when the pressure sensor is used to measure the engine's manifold pressure (MP) or manifold absolute pressure (MAP).

Pressure sensors are used in variable and harsh environments that include characteristics such as varying maximum and minimum temperatures, excessive shock and vibration, high levels of electromagnetic waves that cause electromagnetic interference, and corrosive gases and liquids. must operate within. The pressure close to the pressure inside the intake manifold changes suddenly, and the magnitude of the change is large (1 to 4 atmospheres). These pressure changes occur in supercharged or turbocharged vehicles during boost operation of the supercharger or as a result of explosive backfire. Even without the above, when the present invention is used in an automobile, the pressure sensor is (1)
It must be inexpensive, (2) repeatable, and (3) capable of mass production. To this end, new, low-cost manufacturing techniques are needed, rather than the sputter etching techniques disclosed in U.S. Pat. It shows the necessity of using it.

The present invention is a method of manufacturing a double diaphragm quartz volumetric pressure capsule. This pressure capsule comprises a pair of flat flexible fused silica plates separated by a ring of dielectric material (such as glass frit) to form an internal chamber in which a determinable pressure (vacuum) reference level is maintained. ing. A plurality of electrodes are arranged in the inner chamber of the pressure capsule, forming the plates of the reference capacitor Cr and the pressure sensing capacitor Cp. In particular, one quartz plate, the upper quartz plate, includes a ground electrode, and the other quartz plate, the lower quartz plate, includes Cp and Cr electrodes. The lower quartz plate may include an electrical shield on the surface facing the internal chamber. The pressure capsule also includes a plurality of electrical contacts, each contact associated with a respective electrode. The contacts are located outside the inner chamber, near the edge of each quartz plate.

The object of the invention is to obtain a pressure capsule with an internal pressure (vacuum) reference and a vacuum chip.
To eliminate the need for turn-off, the pressure capsule is sealed in a temperature-controlled pressure (vacuum) environment.

Another object of the invention is to eliminate the need for large hold-down weights and large thermal masses used during the sealing process.

To this end, a method for vacuum-sealing a capacitive pressure capsule having a pair of plates separated by a dielectric including a glass frit, the pressure in the vicinity of the capsule is reduced from atmospheric pressure to a first pressure level lower than atmospheric pressure. and increasing the temperature surrounding the capsule from room temperature to a second temperature level at which the contained gas can be released, and increasing the local pressure to a second pressure level higher than the first pressure level. raising the local temperature to a third temperature level that brings the dielectric to a molten glass state; and increasing the local pressure to a third pressure level after the dielectric has reached the molten glass state. The present invention provides a method for vacuum sealing a capacitive pressure capsule comprising the steps of: varying the dielectric thickness and fixing the plates to each other by raising the dielectric to a height of 100.degree.

An advantage of the invention is that different spacings and therefore different capacities can be obtained. This can be seen from the following. That is, while vacuum sealing the capsule, the dielectric is brought into a molten and viscous state, and a clamping force is applied to both quartz plates by increasing the local pressure. It will be seen that the spacing between both quartz plates changes with the maximum pressure (force) applied and the time it is applied.

The following description is about the method of manufacturing the capsule 100. This manufacturing method mainly consists of the following four main steps. (1) Surface treatment to smooth the surfaces of the quartz plates 102 and 104 to the required degree, (2) Silk screen printing and curing of the electrodes, contacts and ground shields, (3) Silk screening of the frit glass and frit glass. Preglazing to drive out organic binders contained in the material, (4)
Vacuum sealing of pressure capsules.

Manufacturing a pressure capsule begins with preparing the quartz material. In the embodiment described herein, the quartz material is a disk-like structure approximately 2.54 cm (inch) in diameter with flat areas polished on both sides or ends. The parallel planes 120, 122, 124, 126 of the disks are also ground to obtain a determinable flatness. It has been found that the deviation from flatness of these surfaces should be less than 500 Angstroms over the entire surface. After polishing, the quartz plate is cleaned and heated to 900℃ in air. After this heating is completed, the electrical elements (electrodes, contacts, ground shields) of each quartz plate are silk screened onto the surface of the quartz plate, and then the electrical elements are cured. The materials used for the electrodes and ground shield were manufactured by Ingelhart, a company located in New York City, New York, USA.
The metal organic ink A-1830 is manufactured by the company A-1830. This metal organic ink is a combination of platinum and gold suspended in an organic binder. The main components of this metal organic ink are Au15.0%,
Pt2.0%, Rh0.066%.

By this first silk screen printing, the ground shield 1 is placed on the surface 126 of the quartz plate 104.
16 can be formed. The ground shield 116 is air dried in a suitable oven (not shown). This air drying can be carried out at a temperature of 100-150°C. A drying time of 15 minutes has been found to be suitable. This drying oven has a simple box shape, and the internal temperature can be changed, and the amount of oxygen in the oven can be increased by injecting oxygen (O ₂ ) into the oven. Alternatively, the furnace may have multiple temperature zones, an increased amount of oxygen may be present, and an automated belt system may have conveyor mechanisms or belts that transport the parts to be processed in and out of the temperature zones within the furnace. It can be a furnace.

After air drying, the ground shield 116 may be first cured, or the quartz plate may be returned to the silk screen printer to print Cp-Cr electrodes 112, 114 on the flat surface 124 before curing. , air dry this combination. The quartz plate 104 is returned to the furnace to cure the electrode. This regimen is
The first step is to drive out the organic binder contained in the ink that constitutes the electrodes and other electrical elements, and the second step is to fix (i.e., fuse) the remaining material to the quartz plate. It consists of two steps. During this curing process, the remaining electrode material thickness is reduced to an average of 18 KA thin film. The curing process can be carried out according to several different steps, as shown in FIG. 12, or in a single step, longer than that shown in FIG. 13, as shown in FIG. You can also do it. Which one to use depends mainly on the type of furnace used.

First, the curing process shown in FIG. 12 will be explained. The process is intended to be carried out in a box furnace and the desired electrode temperature is shown as a function of time. This curing step includes a first step (solid line) which is low temperature firing. Following low temperature firing, high temperature firing (dashed line) is performed. A quartz plate with designated electrodes attached is placed in a furnace heated to a first temperature, such as 300°C. The quartz plate (and electrode) then quickly reaches this first temperature.

Next, when the temperature in the furnace is increased, the electrode temperature gradually reaches this high temperature (point B). During this temperature increase, most of the hydrocarbons contained in the electrode material are burned off. Incidentally, care should be taken to properly vent the furnace to remove the smoke produced by the combustion of the hydrocarbons. The temperature of the furnace is then increased to even higher temperatures, such as 600°C. Then the temperature of the electrode will be 600℃ (point C)
approach again. During this temperature rise, remaining organic matter contained in the electrode material is removed. Once heated to this high temperature, the electrode is gradually cooled as shown in FIG. As will be explained later, it is also possible to eliminate the cooling step and proceed directly to the high temperature firing step.

After cooling, the quartz plate is placed in a furnace preheated to approximately 900°C (more specifically, 884°C).
This temperature corresponds to the electrode fusion temperature. Depending on the temperature contained in the furnace, it will also be necessary to increase the amount of oxygen therein. The high temperature firing shown in FIG. 12 was carried out in an environment enriched with oxygen by 1 to 5 torr. After the electrode (i.e., the quartz plate) reaches this temperature (point D), the quartz plate is cooled as shown in FIG. 12 by lowering the temperature of the furnace.

Next, refer to FIG. This figure shows an alternative curing process for a multi-zone belt furnace. This furnace (not shown) has at least five temperature zones, and inside the furnace there is a movable belt for transporting the quartz plates to be treated to the various temperature zones. The temperatures in these temperature ranges and the speed at which the belt is moved are the result of the segmented curing process described above, i.e., allowing sufficient time to heat the electrodes to a temperature sufficient to burn off the organic matter. It is selected to achieve fusing of the electrode material to the quartz by heating and then controlling the rate of temperature rise to a temperature of approximately 900°C. Since the organic matter combustion temperature, fusion temperature, and heating temperature in the steps shown in FIGS. 12 and 13 are interrelated, these steps are not limited to the actual temperature one-hour contours shown. You will find that there is no. As in the illustrated example, the combustion temperature of the organic binder can be between 500 and 700°C, depending on the combustion time. Similarly, the fusion temperature can be adjusted depending on the heating time.
The temperature can be 800-1000℃. The temperature and heating time are also affected by the varying thermal mass provided by the quartz plate being treated, the member holding the quartz plate (if necessary), and the dimensions of the furnace.

The curing process shown in FIG. 13 was carried out by setting the belt moving speed to approximately 7.62 to 12.7 cm (3 to 5 inches) per minute and determining the temperatures in each temperature range as follows. Temperature range 1 and 2: 250-625℃,
Temperature range 3: 650~800℃, Temperature range 4: 950~
1000℃, temperature range 5: 925-950℃. The following area temperatures and belt moving speeds appear to be adequate to obtain a quality cured electrode. Temperature range 1 and 2: 350°C, Temperature range 3: 650°C, Temperature range 4: 950°C, Temperature range 5: 925°C, Belt movement speed: Approximately 8.89 cm (3.5 inches) per minute. The furnace used to obtain the temperature profile shown in FIG. 13 is a continuous belt furnace having five temperature zones, each approximately 30 inches long. The furnace was manufactured by Bruce Industrial Controls in North Billerica, Massachusetts.
Controls, Inc.). This furnace is large enough that supplemental oxygen is not required. This furnace has five temperature zones and a fifth temperature zone.
It also has a water-cooled heat exchanger after it. The quartz plate is cooled while being moved into this heat exchange section.

Another step towards achieving a fully automated mass production curing process is to handle the quartz plates after the printing process, or at least after the air drying process and the process of placing the quartz plates into the curing oven. It is to eliminate. The conveyor belt is then extended into an air drying oven. In this way, after the electrode material is printed on a quartz plate, the quartz plate is placed on a conveyor and moved through a drying oven for the required drying time. While the quartz plate is being moved across the base between the two furnaces, the quartz plate is cooled somewhat. After this, the quartz plate is moved into a curing furnace and cured as described above.

At least one of the quartz plates 104 and 102 is then returned to the silk screen printer to print a fritted glass ring around the electrodes 112, 114 with a diameter slightly larger than the diameter of the circular portion of the ground electrode 110. The example described here is
A slurry frit (P-1015) manufactured by Vitta Corporation, Danbury, Conn., USA, is used. This frit material was chosen because the coefficient of thermal expansion of this frit material and quartz are almost the same.
The viscosity of this frit material is approximately 200 centistokes, which allows the frit to be silk screened around the Cp-Cr electrode. Air dry the printed frit at a temperature of 120°C for approximately 15 minutes. The thickness of the frit can be determined by adjusting the dimensions of the silk mesh used or by adjusting the thickness of the frit to be printed.
Control is achieved using standard silk screening techniques, such as adjusting the amount of glass material. Following drying of the quartz plate on which the fritted glass ring 106 is printed, the quartz plate 104 is placed face up on a carrier and placed in a furnace with an oxygen-enriched atmosphere. The internal temperature of this furnace is heated from room temperature to approximately 900°C, particularly 884°C.
The temperature of the quartz plate 104 is 6 to 7 from room temperature to 900℃.
Control the furnace temperature so that it rises in minutes. This treatment removes the organic binder contained in the frit material and returns the frit to its glass phase.
If at some point during the sealing process the quartz plates are placed face-to-face sealed without a pre-brazing step, the organic binder remaining in the frit will create a foam structure. Since this foam structure is non-uniform and differs from pressure capsule to pressure capsule, it is almost impossible to mass-produce pressure capsules with reproducibility. However, preglazing the frit glass material prior to sealing the capsule 100 increases the amount of organic binder released from the frit glass and increases the amount of organic binder contained within the frit. The reduction reduces the resulting cell structure, thereby improving the uniformity between capsules. By minimizing the cellular structure, a means of making the pressure capsule 100 temperature stable can be obtained. Another preglazing alternative to the preglazing described above is to subject the frit to a time-temperature profile as shown in FIG.

A second quartz plate 102 having a circular ground electrode 110 and contact pad 128 is similarly printed, air dried, fired in air, and cured.

Vacuum sealing of the pressure capsule 100 is performed as follows. A quartz plate 104 including a Cp-Cr electrode,
The 9th to 11th quartz plates 102 including the ground electrode 110
Place in the alignment fixture 175 shown. With this positioning fixture, two quartz plates 102,
104 can be placed facing each other so that they can be rotated by a certain determinable angle (90 degrees in this example) relative to each other. Positioning fixture 17
5 surrounds the pressure capsule with endothermic material during the sealing process to create a uniform radiation pattern for heating and sealing the pressure capsule 100. One alignment fixture 175 or multiple fixtures 1
75 and a pressure capsule 10 attached to it
0 and a quartz boat or movable tray (not shown)
A thermocouple is attached to it, and then placed in a diffusion chamber (not shown).

Next, refer to FIG. 14. This figure shows the temperature-pressure profile used to vacuum seal each pressure capsule 100 and create a predetermined vacuum within the capsule. Figure 14 shows the designed pressure profile and two temperature profiles. Both produced acceptable results. The first profile (straight lines A, B) requires that the temperature rise monotonically for a predetermined period of time and then cool down. The second contour (straight lines C, B) shows a discrete temperature contour followed by a cooling period.

Appropriate number of unsealed pressure capsules 1
placing the fitting 175 to which 00 is attached into a first room temperature region of the diffusion furnace, and then sealing the furnace;
Evacuate the inside of the furnace to a predetermined degree of vacuum. This first
The vacuum level is low enough to facilitate degassing of any organic matter remaining in the electrode or frit glass. By removing these gases and possible bubbles, the temperature coefficient of the capsule is stabilized. The first vacuum should be as low as possible, but 0.05 torr seems appropriate. After the interior of the furnace has stabilized to the first degree of vacuum, the interior of the unsealed pressure capsule 100, that is, the interior of the interior chamber 148 (the space between the quartz plates 102, 104 and the fritted disk 106) is also Similarly, this first
The degree of vacuum will be . Pressure capsule 100 and alignment fixture 178 are then exposed to one of the temperature profiles shown in FIG.

The following description is for the discontinuous temperature method. The description of this method assumes that the sealing is carried out inside a diffusion furnace of the type having at least three temperature zones. The temperature within each temperature range is related to the properties of the metal-organic ink and fritted glass material. the first temperature region is kept at room temperature;
A second temperature zone is maintained at a temperature selected to remove any gas remaining in the frit material and the metal-organic ink, and a third temperature zone is maintained at a temperature selected to remove any gas remaining in the frit material and the metal-organic ink, and a third temperature zone is maintained at a temperature selected to allow the frit material to become viscous for a predetermined period of time. The temperature at which it changes to the glassy state, approximately 900°C in the example described here.
kept at ℃. At this temperature, Vitta
The frit material reaches a molten state quickly.

The alignment fixture is then quickly moved to the second temperature region. In the second temperature range, the temperature of the unsealed pressure capsule 100 is at the second temperature range.
temperature level. The pressure capsule 100 is held in the second temperature region for a time T ₁ in order to allow the trapped gas to escape. Degassing time 12
~20 minutes (this time varies depending on the thermal mass or heat load) has been found to be suitable. After degassing, move the alignment fixture to the third temperature range and hold there for ₃ hours.
Meanwhile, the pressure in the furnace is increased by 1 to 8 torr with oxygen. This pressure increase reduces the oxides within the frit material, reducing the likelihood that the frit material will become conductive. This vacuum also determines the final pressure inside the capsule (measured at room temperature) after it has been sealed and cooled.

The rate of temperature rise of capsule 100 is monitored to ensure that the third temperature level is reached in 6-7 minutes. After the frit is in a melted state (No. 14)
point D in the figure), the pressure inside the diffusion furnace is set to a third point close to atmospheric pressure.
pressure level. However, the pressure inside the furnace does not need to be atmospheric pressure; around 700 torr is sufficient. At this pressure level, the increased pressure will be approximately 4.5 Kg on each flat surface of the pressure capsule 100.
Apply a clamping force of (10 pounds) to the frit 1.
06 to its final height. but,
By setting the pressure inside the furnace above atmospheric pressure, a large clamping force can be applied. Utilizing a pressure profile such as that shown in Figure 14 to apply clamping force to the pressure capsule eliminates the need for large thermal masses such as large clamping weights inside the furnace, thereby reducing processing time. Mass production of shortened pressure capsules can be carried out rapidly. However, by adding a small pressing weight of approximately 270 g to the top surface of the topmost alignment fixture, the pressure capsule 10
It is desirable to further secure the alignment fixture to 0 and compress the fritted glass first. The pressure in the furnace is increased to a third pressure level, and then the pressure is rapidly decreased to an intermediate fourth pressure level, such as 40 Torr. It is desired that this fourth pressure level be higher than the pressure level inside the capsule 100. The alignment fixture 175 is then moved to a first temperature region before the capsule is allowed to cool. It is sufficient to cool the pressure capsule to a temperature below 470 degrees. At this temperature, the pressure inside the furnace is increased to atmospheric pressure and the sealed pressure capsule is removed from the furnace.

It should be noted that when the pressure within the furnace is increased to the third pressure level, the pressure outside the pressure capsule is significantly higher than the pressure inside the inner chamber 148. During this time, the viscous frit material prevents significant amounts of oxygen from entering the interior chamber 148. As mentioned above, after applying the clamp pressure, the pressure within the furnace is immediately reduced to a lower fourth pressure level, further reducing the possibility of oxygen entering the pressure capsule. It is apparent that at the third pressure level the clamping force deforms the capsule 100 from the desired parallel configuration. When the capsule is deformed, the thickness of the portion of the molten frit glass may become non-uniform, since the frit glass was previously affixed to the quartz plates 102, 104. If the capsule 100 is allowed to cool in this deformed state, the measurement characteristics of the capsule will be affected. Therefore, the fourth pressure level is
is chosen so that it can be returned to a parallel orientation.

Referring again to FIGS. 9, 10, and 11. These figures illustrate the characteristics of the alignment fixture 175 and how the alignment fixtures can be stacked on top of each other to enable vacuum sealing of multiple pressure capsules 100 in large quantities. The alignment fixture 175 is made of rolled alloy 330
It has a plurality of thin metal plates 176 made from steel such as (RA330). This metal plate has an upper surface 180 and a lower surface 182 that are parallel to each other. Each side has a pressure capsule receiving cavity 184, 186, respectively. The dimensions of these cavities are quartz plates 102, 104.
The size is such that the quartz plate 102,1 is closely received.
Matches the shape of 04. Also, the depth d of each cavity is determined such that when the quartz plate on which the electrodes or frits are printed is placed into the pressure capsule receiving cavity, a portion of the quartz plate emerges from the cavity. Pressure capsule receiving cavities 184 and 186 provided on the upper surface 180 and lower surface 182 of each quartz plate, respectively, are
The flat ends 132, 150 (ie, the cutouts) are aligned with each other so that the electrical contacts 120, 140, 146 can be aligned. In the embodiment described herein, the pressure capsule receiving cavities 180, 182 are arranged relative to each other so that the electrical contacts can be moved vertically as desired.
Can only be rotated 90 degrees.

Each pressure capsule 10 into the alignment fixture
0 is installed as follows. Quartz plate 1
A cured and preglazed quartz plate like 04 is placed on one side of the alignment mounting plate, e.g.
176a, into the capsule receiving cavity 182.
The first cured quartz plate 102 is also placed into the lower pressure capsule receiving cavity 186 of the second alignment mounting plate 176b. Mounting plates 176a, 176 to which quartz plates 102, 104 are attached, respectively, so that the surfaces of the electrodes protrude
b are placed on top of each other, and the electrodes 110,1
12 and 114 so that they are mounted at 90 degrees to each other. By repeating this stacking operation, a plurality of pressure capsules 100 can be stacked and mounted in the alignment fixture 175.

Each mounting plate 176 and thus each quartz plate is aligned with the opposing quartz plate by mounting plate 176.
6 has a set of alignment holes 19 for receiving alignment pins 192.
0 is set. Alignment pin 192 and mounting plate 1
76 is made using the same metal. To facilitate uniform heating of pressure capsule 100 by alignment fitting 175, fitting 175 (i.e.
Preferably, the alignment fixture 175 is heat treated to create an oxide layer over the entire mounting plate.

Next, No. 15 shows another embodiment of the pressure capsule.
See diagram. These figures show a circular pressure capsule 154 having an upper disk 156 and a lower disk 158.
It is shown. Electrodes 10 in these discs
The arrangement of electrodes 0, 112, and 114 is the same as the arrangement of the electrodes in the previous embodiment. However, electrical contact 14
0 and 146 are not provided facing each other, but are arranged obliquely to each other. Circular ground electrode 110
are connected to a single electrical contact 128 that is uniformly located between contacts 140 and 146. Additionally, the upper disk 156 has one cutout 160a.
The lower disc 158 includes a plurality of cutouts in each disc and electrical contacts 128, 140 disposed facing each other on opposite discs.
or expose 146.

[Brief explanation of drawings]

Fig. 1 is an exploded view of the pressure sensor, Fig. 2 is a sectional view of the pressure sensor, and Fig. 3 is a sectional view taken along line 3-3 in Fig. 2, showing the pressure sensor shown in Fig. 2 with a part removed. , FIG. 4 shows 4 in FIG. 2 without the housing.
5 is a partial sectional view along line 5-5 of FIG. 4, FIG. 6 is a sectional view of the pressure capsule, and FIG. 7 is a sectional view along line 7-7 of FIG. 6. The bottom view of the upper quartz plate of the pressure capsule, Figure 8 is 8- in Figure 6.
Top view of the lower quartz plate of the pressure capsule along line 8,
Fig. 9 is a sectional view of the alignment fixture, Fig. 10 is a sectional view taken along line 10-10 in Fig. 9, Fig. 11 is a sectional view taken along line 11-11 in Fig. 9, and Fig. 12 is a sectional view taken along line 11-11 in Fig. 9. FIG. 13 is a graph showing an electrode curing process; FIG. 14 is a graph showing a temperature-pressure sealing method; FIG. 15 is a plan view showing another embodiment of the pressure capsule; FIG. 16 is a sectional view taken along line 16-16 in FIG. 15. 102,104...Quartz plate, 180,182...Surface of quartz plate, 184,186...Quartz plate receiving cavity,
190... Alignment hole, 192... Alignment pin.

Claims (1)

[Scope of Claims] 1. A method for vacuum-sealing a capacitive pressure capsule having a pair of plates separated by a dielectric material containing a glass frit, the method comprising: reducing the pressure in a region near the capsule from atmospheric pressure to a lower pressure; increasing the temperature surrounding the capsule from room temperature to a second temperature level capable of releasing the contained gas; and increasing the local pressure above the first pressure level. increasing the local temperature to a second pressure level; increasing the local temperature to a third temperature level that causes the dielectric to be in the molten glass state; and fixing the plates together by varying the thickness of the dielectric by increasing the pressure to a third pressure level. 2. A method for vacuum sealing a capacitive pressure capsule having a pair of plates separated by a dielectric including a glass frit, the pressure being reduced near the capsule from atmospheric pressure to a first pressure level lower than atmospheric pressure. increasing the temperature surrounding the capsule from room temperature to a second temperature level capable of releasing the contained gas; and increasing the local pressure to a second pressure level higher than the first pressure level. raising the local temperature to a third temperature level that causes the dielectric to be in a molten glass state; and increasing the local pressure to a third pressure level after the dielectric is in the molten glass state. fixing the plates to each other by changing the thickness of the dielectric by increasing the thickness of the dielectric to
cooling the capsule to a fourth pressure level intermediate the pressure level of the capsule, cooling the capsule, and increasing the local pressure to atmospheric pressure after cooling the capsule. How to vacuum seal a mold pressure capsule.