JP4264156B2 - Pirani vacuum gauge - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a Pirani gauge used for vacuum measurement.
[0002]
[Prior art]
The Pirani gauge is known as a heat conduction type gauge utilizing the fact that the electrical resistance of a heated filament such as platinum changes with temperature. For example, a single filament g as shown in FIG. One end of an envelope a such as a metal cylinder that shuts off the vacuum and the atmosphere containing air from an outer peripheral metal cylinder b welded to the envelope a and an electrical insulating member c such as ceramics or glass inside. The terminal d is closed, and the electrical insulating member c is inserted and three electrical connection pins e are embedded by brazing, and the two electrical connection pins e and e extend into the envelope a. The thing of the structure which welded the metal rod f of this is known. The filament g is stretched by welding both ends thereof to one of the pins e and the U-shaped metal rod f. h is a flange hermetically welded to the envelope a, which is attached to a vacuum device (not shown), and two pins e connected to the filament g are connected to the controller of the Pirani vacuum gauge by a connector (not shown). The pressure of the vacuum device is measured.
[0003]
Further, Pirani gauges having the configurations shown in FIGS. 2 to 5 are also known, and in these drawings, the description of the envelope and the flange is omitted. 2 and 3, four electrical connection pins e are airtightly brazed, two of which are welded with a U-shaped metal rod f, and the other two pins e, A filament g composed of two filament members g ′ and g ′ is stretched between e and the metal rod f, and the filament g is welded and fixed at four points.
[0004]
4 and 5, the three electrical connection pins e are brazed, and a metal disk i is welded to the tip of one of the pins, and the other two pins e. And the disk i, a filament g composed of two filament members g ′ and g ′ is stretched, and in this case, the filament is fixed at four points.
[0005]
The structure shown in FIGS. 2 to 5 has the filament g reciprocated once, and the length of the vacuum gauge can be shortened by reciprocating, which is effective in reducing the size of the vacuum gauge. More than two reciprocations can reduce the size, but the effect of the miniaturization is slight, and two or more reciprocations are carried out because it becomes difficult to suppress the variation between solids of the entire length of the filament. Not.
[0006]
As shown in FIGS. 6 and 7, the filament g is generally welded to the metal bar f or pin e by spot welding, and the metal bar f or the like is placed on the lower electrode j, and further The filament g is placed thereon, the upper electrode k is lowered, the metal bar f and the filament g are sandwiched, and energized to weld the metal bar f and the filament g. Alternatively, electrodes j and k having shapes as shown in FIGS. 8 and 9 are used. In the case of spot welding, in order to facilitate welding, a platinum thin film or the like may be sandwiched between the metal rod f or the like and the filament g.
[0007]
The Pirani gauge is a gauge that uses heat transfer between a gas molecule in a vacuum and a heated filament g, and the filament g is usually heated to a temperature of 100 ° C. or more from room temperature. The heat lost by the filament g is as follows: (1) heat taken away by collision of gas molecules in vacuum, (2) heat taken away by the envelope by thermal radiation of the filament, (3) filament support electrode by heat conduction from the end of the filament There are three types of heat deprived. If the temperature of the filament is controlled to be constant even if the pressure changes and the amount of heat transfer between the gas molecule and the heated filament changes, the heat radiation and heat transfer of (2) and (3) above can be achieved. The amount becomes constant. However, if the filament temperature is controlled to be constant when the pressure changes and the amount of heat transfer between the gas molecules and the heated filament g changes, the power (or voltage) applied to the filament g changes. become. For example, when the pressure increases, the amount of heat transfer between the gas molecules and the heated filament increases, and the power (or voltage) applied to the filament g increases. Conversely, when the pressure is lowered, the amount of heat transfer between the gas molecules and the heated filament is reduced, and the power (or voltage) applied to the filament is reduced. The pressure can be measured by converting the increasing or decreasing power (or voltage) into pressure.
[0008]
[Problems to be solved by the invention]
The response characteristics of the rise and fall of the conventional Pirani gauge are as shown by the curves A and B in FIGS. 23 and 24, and the response characteristics of the diaphragm gauge are shown together with the curves C and D. These responsivenesses were examined in the range of 1.3 × 10 ^{−3 to} 26.7 Pa using an ambient temperature of 25 ° C. and nitrogen as a test gas, and a butterfly valve was used to open and close the gas for introduction and exhaust. The pressure in the space where the vacuum gauge was installed was changed abruptly, and the output signal response of the vacuum gauge was examined. If the elapsed time when the output changes to 95% is taken as the response time, the response of the vacuum gauge is about 0.6 seconds at the rise time and about 2.5 seconds at the fall time.
[0009]
For example, in the semiconductor process, the pressure of the vacuum gauge is monitored and process control such as a process gas introduction valve is performed, but it does not deteriorate over time compared to the diaphragm vacuum gauge and can withstand high temperatures of 100 ° C or higher. One of the reasons why the Pirani gauge, which has the advantage of wide range, is difficult to use, is its slow response. For example, when exhausting while introducing gas into a semiconductor device, if the response of the vacuum gauge output is delayed so as to keep the pressure in the device constant, the control of the valve opening / closing degree is delayed, and the pressure in the device is kept constant. This is not preferable because it cannot be maintained and fluctuations occur.
[0010]
Since the diameter of the filament g is usually about several tens of microns, it is easy to cut and difficult to handle. Further, when the filament g is composed of a plurality of filament members g ′, the measurement of each Pirani vacuum gauge varies if individual differences in the total length (total length) are not eliminated. Since the pin e is fixed in a ceramic or glass insulator constituting the terminal, an error is likely to occur in the mounting position, and the manufacturing accuracy of the pin e is not good, so the mounting accuracy of the metal rod cannot be expected. Accurate assembly without variation in the entire length of the filament g is difficult. Filament welding is performed by holding the terminal d by hand or fixing it to the machine and setting it between the electrodes of the spot welder, but it involves complicated operations of moving and swiveling the terminal d in three dimensions. Work becomes difficult, and becomes more difficult as the number of filament members increases. Because spot welding work is difficult, welding tends to be uncertain, the metal rod f is thin and easy to vibrate, and when the Pirani vacuum gauge is vibrated, excessive force is applied to the filament and it is easy to break. is there.
[0011]
An object of the present invention is to provide a Pirani vacuum gauge that has a quick response, and to provide a Pirani vacuum gauge that is easy to manufacture, has good filament durability, and has little individual difference.
[0012]
[Means for Solving the Problems]
[0013]
An object of the present invention is that a filament provided in an envelope of a Pirani vacuum gauge is composed of a plurality of filament members, and a terminal for closing one end of the envelope is connected to two electrical connection pins and one metal. A shaft is embedded, a mounting plate extending into the envelope is provided on the metal shaft, and a conductive terminal plate is provided on the plate surface of the mounting plate, and each filament member is electrically connected between both electrical connection pins. This can also be achieved by welding each end of each filament member to each conductive terminal plate so that they are connected in series. The mounting plate is formed of a metal plate, and the conductive terminal plate is attached to the conductive terminal plate via an electrical insulating material. It may be fixed to a plate and each filament member may be arranged on substantially the same plane.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
A technique related to the present invention will be described with reference to the drawings. In FIGS. 10 to 12, reference numeral 1 denotes a metal cylindrical envelope of a Pirani gauge, 2 denotes a terminal for closing one end of the envelope 1, The terminal 2 is composed of a metal cylinder 3 on the outer periphery, an electrical insulating member 4 made of ceramics, and five electrical connecting pins 5 embedded in the insulating member 4 and airtightly brazed. Two of the pins 5 are welded with L-shaped metal rods 6 to form long electrical connection pins, and four pins are provided between the metal rod 6 and the remaining three short pins 5. A filament 8 composed of a platinum filament member 7 is stretched.
[0015]
Each filament member 7 has a length of 25 mm and is welded to the pin 5 and the metal rod 6 so as to be electrically connected in series, so that a total filament 100 having a total length of 100 mm is formed. . The filament 8 in this case is welded and fixed at eight locations, but the number of the long and short pins 5 is adjusted to make the filament member 7 three, and may be welded at six locations, or five or more at ten locations. May be.
[0016]
This is because the temperature gradient in the length direction of the filament is increased by constructing three or more series connections and increasing the number of welding fixing points, rather than constructing a filament having a total length of Lmm with one or two filament members. Since the heat transfer between the filament member 7 and the pin 5 or the metal rod 6 becomes rapid, the transient time until the filament temperature reaches a steady state when the pressure is suddenly changed is shortened. 10 to 12, the response characteristics as shown by the curves E and F in FIGS. 25 and 26 are obtained. This responsiveness is significantly improved over the conventional example of FIGS. 23 and 24 under the same measurement conditions. In this case, assuming that the elapsed time when the output changes to 95% is the response time, the rise time is about 0.3 seconds and the fall time is about 0.5. Curves C and D are response characteristics of the diaphragm gauge.
[0017]
The filament member 7 is a metal thin wire of about several tens of microns, although easily broken at failure and vibration welding, the embodiment is shown in FIGS. 16 to 22, with a screw terminal 2 in addition to the electrical connection pins 5 The metal shaft 9 is embedded, and an L-shaped mounting plate 10 is fastened to the metal shaft 9 with a nut 11 so as to extend into the envelope, and electrically insulated conductive terminals provided on the plate surface of the mounting plate 10 The end of the filament member 7 was welded to the plate 12 to prevent the disconnection. Since the conductive terminal plate 12 is along the plate surface of the mounting plate 10, it is easy to accurately determine the distance between the conductive terminal plates 12, thereby reducing individual differences in the total length of the filament and eliminating individual differences in the sensitivity of the Pirani gauge. Make it. The metal shaft 9 is 3 mm in diameter, and the mounting plate 10 is a 2.5 mm thick metal plate or electrical insulating plate.
[0018]
In Example shown in FIGS. 16 to 20, made mounting plate 10 is metallic, the hermetic seal 16 consisting of an outer peripheral genus metallic ring 13 and the inside of the glass 14 with an insulating metal pillar 15. shown in FIG. 18 Three conductive terminals 12 were attached to each pillar 15 and the two pillars were connected to the pins 5 by lead wires 17. 21 and FIG. 22, the insulating plate 18 made of ceramics or the like is fixed to the mounting plate 10 by brazing or the like, and the conductive terminal plate 12 is attached thereto by brazing or the like. When an insulating material such as ceramic is used as the mounting plate 10, the conductive terminal plate 12 may be directly brazed.
[0019]
FIG. 13 to FIG. 15 are explanatory views of the welding method of the embodiment of FIG. 21. On the copper spot welding jig 19 placed on the XYZ table and connected to the spot welding electrode cable 20, the conductive terminal plate is shown. 12 and the mounting plate 10 are placed, the filament member 7 is sandwiched between the conductive terminal plate 12 and the upper electrode 21, the filament member 7 and the conductive terminal plate 12 are melted and welded by energization, and the movement of the XYZ table 8 Spot weld the points. Since the spot welded spot is on the same plane along the mounting plate 10, the welding operation is facilitated and accurate and reliable welding can be performed.
[0020]
By providing such an attachment plate 10 and attaching the filament member 7 thereto, it is difficult to apply force to the filament member 7 even when the attachment plate 10 vibrates due to impact when the Pirani vacuum gauge is used. Disconnection is prevented.
[0021]
【The invention's effect】
As described above, in the present invention, since the filament of the Pirani vacuum gauge is composed of a plurality of filament members, the response characteristic to a sudden pressure change is improved, the response characteristic close to the diaphragm vacuum gauge is obtained, and one end of the envelope is obtained. A metal shaft is embedded in the terminal to be closed, a conductive terminal plate is provided on the plate surface of the mounting plate attached to the metal shaft, and each filament member is electrically connected in series between both electrical connection pins. Since both ends of each filament member are welded to each conductive terminal board, a Pirani vacuum gauge with good response characteristics, easy manufacture and resistance to filament breakage due to vibration can be obtained, and it can be conveniently applied to vacuum process control, etc. There is an effect.
[Brief description of the drawings]
FIG. 1 is a cutaway side view of a conventional Pirani vacuum gauge. FIG. 2 is a cutaway side view of another conventional Pirani vacuum gauge. FIG. 3 is a sectional view taken along line 3-3 in FIG. FIG. 5 is a cross-sectional view taken along line 5-5 of FIG. 4. FIG. 6 is a front view of a conventional filament welded state. FIG. 7 is a plan view of FIG. FIG. 9 is a plan view of FIG. 8. FIG. 10 is a front sectional view of a technique related to the present invention. FIG. 11 is a sectional view taken along line 11-11 of FIG. FIG. 13 is an explanatory view of a welding state in the embodiment of the present invention. FIG. 14 is a plan view of FIG. 13. FIG. 15 is a side view of FIG. 17 is a sectional view taken along line 17-17 in FIG. 16. FIG. 18 is an enlarged sectional view of a hermetic seal. FIG. 19 is a front view of still another embodiment of the present invention. 20 is a sectional view taken along line 20-20 in FIG. 19. FIG. 21 is a front view of still another embodiment of the present invention. FIG. 22 is a sectional view taken along line 22-22 in FIG. FIG. 24 is a diagram of the response characteristics of the fall of the conventional Pirani vacuum gauge. FIG. 25 is a chart of the response characteristics of the rise of the Pirani vacuum gauge of the embodiment shown in FIG. 10 relating to the present invention. 26 is a diagram of the falling response characteristic of the Pirani gauge of the embodiment shown in FIG. 10 relating to the present invention.
1 Envelope, 2 Terminal, 5 Electrical connection pin, 6 Metal rod, 7 Filament member, 8 Filament, 9 Metal shaft, 10 Mounting plate, 12 Conductive terminal plate,

Claims (3)

The filament provided in the envelope of the Pirani gauge is composed of a plurality of filament members, and two electrical connection pins and one metal shaft are embedded in a terminal that closes one end of the envelope, A mounting plate extending to the inside of the envelope is provided on the metal shaft, and a conductive terminal plate that is electrically insulated is provided on the plate surface of the mounting plate, so that each filament member is electrically connected in series between both electrical connection pins. A Pirani gauge, wherein both ends of each filament member are welded to each conductive terminal plate.   The Pirani vacuum gauge according to claim 1, wherein the mounting plate is formed of a metal plate, and the conductive terminal plate is fixed to the mounting plate via an electric insulating material.   The Pirani vacuum gauge according to claim 1, wherein the filament members are arranged on the same plane.

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