EP0000866A1 - Process for manufacturing an analysing system for a multipole-mass filter - Google Patents

Abstract

Method for producing a high-precision and dimensionally stable analyzer system for a multipole mass filter, in which a tube (7) made of electrically poorly conductive, thermally softenable material is pulled over a dimensionally precise mold core (1) with a higher expansion coefficient and parallel grooves (3), whereupon the Pipe material clings to the grooves (3) of the mandrel (1) by heating and then, after solidifying cooling, is pulled off from the mandrel (1) with the embossed tube indentations (9). Before the tube (7) is heated, layers (5) made of electrically highly conductive metallic components which are easily connectable to the softenable tube material are introduced between the mandrel (1) and tube (7) in the region of the grooves (3). The layer material is connected to the pipe material when the pipe (7) softens and nestles against the grooves (3). When the tube (7) shaped in this way is pulled off, the layers (5) connected to the embossed tube indentations (9) are also removed from the mandrel (1). An analyzer system produced by the method according to the invention is shown in FIGS. 2 to 4.

Description

The invention relates to a method for producing a high-precision and dimensionally stable analyzer system for a multipole mass filter, in which a tube made of electrically poorly conductive, thermally softenable material is drawn over a dimensionally precise mold core with a higher expansion coefficient and parallel grooves, whereupon the tube material is heated Grooves of the mandrel nestles and then after solidifying cooling with the embossed tube indentations is pulled off the mandrel. as well as an analyzer system with high precision and dimensional stability for a multipole mass filter, with a tube made of electrically poorly conductive, thermally softenable material with tube indentations impressed by softening over a dimensionally precise mandrel with a higher expansion coefficient and parallel grooves.

The principle of operation of a high-precision and dimensionally stable analyzer system for a multipole mass filter, which is known to the person skilled in the art as a multipole mass filter according to Paul, is described in DE-PS 944 900.

A multipole usually consists of the number of poles corresponding to electrically conductive round or hyperbole rods; In particular, a quadrupole consists of four parallel, electrically conductive round or hyperbole rods. The rods are held parallel to one another by one or more electrically insulating mounting parts that surround them on the outside in the form of rings or cages, the rod centers being arranged square in section. The requirements for parallelism, freedom from torsion, the equality of the spacing of diagonally opposed rods and the perpendicularity of these diagonals are particularly for those mass filters that are in higher mass ranges with masses larger than 500 atomic mass units: (m> 500 u ), should be used, extremely high.

von der Amplitude V und der Kreisfrequenz w der angelegten Hochfrequenzspannung sowie vom Scheitelabstand der jeweiligen Stäbe 2 r₀ ab. Damit bei einer eingestellten Durchlaßmasse m = 1.000 u an zwei beliebigen Stellen im Quadrupolfilter die Differenz der durchgelassenen Masse nicht größer als 0,1 u ist, darf die relative Abweichung des Scheitelabstands

höchstens 1/20.000 betragen. Dies ergibt bei einem diagonalen Scheitelabstand 2r_o von üblicherweise 8 mm eine Genauigkeitsforderung von 0,4 pm.The ion mass m let through by the quadrupole filter depends on the equation

on the amplitude V and the angular frequency w of the applied high-frequency voltage and on the vertex distance of the respective rods 2 r ₀ . So with a set transmission mass m = 1,000 u at any two points in the quadrupole filter, the difference between allowed mass is not greater than 0.1 u, the relative deviation of the vertex distance

not exceed 1 / 20,000. With a diagonal apex distance 2r _o of typically 8 mm, this results in an accuracy requirement of 0.4 pm.

For cylindrical rods with a two-point support, this value is already exceeded by the natural deflection under the influence of gravity. Such an arrangement of a multipole filter with pole rods and separate insulating holders can therefore only meet the required accuracy conditions with difficulty.

Therefore, a filter was described in GB-PS 1 367 638, which consists of a tubular, torsion-free and low-deflection insulator with conductive surface coverings, this filter being produced from an extruded ceramic tube with subsequent firing and partial covering of the inner surfaces with a conductive layer . However, the firing causes the pipe to shrink by about 10% and therefore does not allow the dimensional accuracy requirements described above; therefore, the use of such quadrupole filters as a residual gas analyzer is only in the lower mass range.

DE-PS 1 297 360 describes the production of high-precision glass tubes on a mandrel with subsequent metallization of the indented inner surfaces for use as a quadrupole system.

und mit der Amplitude V liegt. Bei üblichen Daten von C = 50 pF, V=2 MHz und V = 5kV fließen Spitzenströme von i = V ω C = 3A. Ströme in dieser Größenordnung fließen über die leitfähige Schicht und verursachen über sie hinweg einen Spannungsabfall zwischen den verschiedenen Stellen der Oberfläche im Quadrupol. Für die Spannung V ist ähnlich wie gemäß der obigen Gleichung für den Scheitelabstand 2r_o eine hohe Präzision zu fordern, nach der die Spannung an verschiedenen Stellen unter den.Bedingungen des obigen Zahlenbespiels nur maximal um 1/10.000 von ihrem Sollwert abweichen darf, so daß der Widerstand einer der vier leitenden Schichten über seine Länge hin nicht mehr als 0,1 Ω betragen darf. Bei einem Metall mit einem spezifischen Widerstand von 10^-5 Ω cm als leitendem Schichtmetall, wobei die Länge der Schicht etwa 20 cm und die Breite der Schicht etwa 1 cm beträgt ist eine Mindestschichtdicke von 20 um zu fordern, wobei nach den obigen Darlegungen die Präzision der Dicke der Schicht sich im Bereich von 0,4 µm halten muß. Eine solche Genauigkeit ist nach dem gegenwärtigen Stand der Technik weder elektrolytisch noch mittels Aufdampfen oder Auftragen erreichbar.The main disadvantage here is that the subsequent application of the conductive layer destroys the dimensional accuracy of the analyzer tube. _D as .Quadrupolsystem provides namely electrically seen a capacitor of capacitance C is, in which a _H with the frequency ochfrequenzspannung

and lies with the amplitude V. With usual data of C = 50 pF, V = 2 MHz and V = 5kV, peak currents of i = V ω C = 3A flow. Currents of this magnitude flow across the conductive layer and cause a voltage drop across it between the various locations on the surface in the quadrupole. For the voltage V, similar to the equation for the vertex distance 2r _o, a high degree of precision is required, according to which the voltage at various points under the conditions of the above example can only deviate from its nominal value by a maximum of 1 / 10,000, so that the resistance of one of the four conductive layers over its length must not be more than 0.1 Ω. In the case of a metal with a specific resistance of 10 ^-5 Ω cm as the conductive layer metal, the length of the layer being approximately 20 cm and the width of the layer being approximately 1 cm, a minimum layer thickness of 20 μm is required, the precision being as stated above the thickness of the layer must be in the range of 0.4 µm. According to the current state of the art, such an accuracy cannot be achieved either electrolytically or by means of vapor deposition or application.

The invention is therefore based on the object of improving the known method of the type described in the introduction while avoiding its disadvantages and, in particular, of creating a warp and bend-free, highly precise and dimensionally stable analyzer system for a multipole mass filter, the adhesion of the layers or layers being electrical conductive material on the softenable pipe material to be improved should, so that highly precise and dimensionally stable electrodes can be created overall in analyzer systems for multipole mass filters by using also different types of metallic components for the layers to be connected to the tube material.

According to the invention this object is achieved in a method of the type mentioned in that before heating the tube between the mandrel and the tube, layers of electrically conductive, easily connectable to the softenable tube material are introduced in the region of the grooves; that the layer material is connected to the pipe material when the pipe is softened and nestled against the grooves; and that when the tube thus formed is removed, the layers connected to the embossed tube indentations are removed with the mold core, a particularly preferred embodiment providing that metal foils are used as layers, which are inserted into the grooves of the core before the tube is softened.

The analyzer according to the invention is preferably characterized in that connected to the tube in the interior to the Rohreinbuchtungen films of good electrical conductivity fähi ^g em metal.

According to a preferred embodiment of the present invention, it is provided that the tube is evacuated before it is softened as a whole. This makes it easier for the softened pipe to nestle against the grooves of the mandrel.

Further embodiments of the invention are characterized in that foil material with a largely identical coefficient of thermal expansion as the tube material is used or that foils made of a very ductile metal are used so that the covering material always takes the form of the tube material when it cools down. Gold and platinum are particularly suitable as film material.

Another preferred embodiment of the present invention is characterized in that the film surface is provided with a meltable coating before insertion into the grooves of the mandrel to facilitate melting. This facilitates the melting of the foils with the pipe material.

Another preferred embodiment is that the tube is a glass tube.

In the method according to the invention it can further be provided that the metal foils are provided with protrusions extending from the foil surface facing away from the mold core; and that the protrusions are essentially melted in the softenable material, the corresponding analyzer system in a preferred development of the invention then being characterized in that the metal foils are connected to the tube material essentially by means of protrusions extending from the foil surface into the tube material.

As an alternative to this, it can also be provided that a coating of a glossy metal paste is applied to the inner surfaces of the tube as the metallic component; and that the paste is converted into metal by means of higher temperatures.

Alternatively, it is also proposed that as a metallic Component a coating of a conductive metal composition is applied to the inner surface of the tube; and that the lead metal composition is subsequently converted to metal.

An essential part of the idea of the invention lies in the fact that during the final molding process of the tube made of softenable material, the metal electrodes are formed at the same time - in particular by resting the grooves of the mandrel - and are pressed there by the surrounding tube material in order to provide a highly precise and extremely smooth surface of the metal layer to reach. In the known method according to DE-PS 1 297 316, in contrast, the metallization is carried out only after the analyzer tube has been formed on the mandrel, and, as explained, insufficient accuracy is not guaranteed.

Further embodiments of the invention are characterized in that the projections of the films are bent flanges, that the projections are notches in the films, that the projections on the films are soldered or welded ribs, or that the projections are wires or soldered or welded to the films .

Other preferred embodiments of the present invention are characterized in that bright gold or bright silver is used as the metallic component.

According to an extremely preferred embodiment of the invention when applying conductive metal compositions gene is provided that a conductive varnish is applied and that the conductive varnish is dried. The conductive varnish can be spread on, sprayed on or applied by dipping.

Another preferred embodiment of the present invention provides that the conductive layer is applied by means of reduction metallization and in particular that an end metal layer is electroplated. In particular gold, silver or copper, but also tin as tin oxide in a preferred embodiment can be applied as the lead metals in the dipping process.

• Fig. 1 ein herkömmliches Quadrupolsystem aus vier zylindrischen Stäben, die durch isolierende Ringe gehalten sind;
• Fig. 2 einen Querschnitt durch den Formkern mit eingeschliffenen Nuten, eingelegten Folien und übergezogenem Isolierrohr;
• Fig. 3 den Querschnitt durch den Formkern mit angeschmiegtem Isolierrohr und mit ihm verschmolzenen Folien;
• Fig. 4 einen Querschnitt durch das abgezogene Quadrupolrohr mit aufgeschmolzenen Folien;
• Fig. 5 in ähnlicher Darstellung wie bei dem in den Fig. 2 bis 4 gezeigten Ausführungsbeispiel einen Querschnitt durch den Formkern mit eingeformten Nuten bei einem zweiten Ausführungsbeispiel, mit eingelegten Folien und übergezogenem Isolierrohr;
• Fig. 6 den Querschnitt durch den Formkern von Fig. 5 mit angeschmiegtem Isolierrohr und mit ihm verschmolzenen Folien; und
• Fig. 7 einen Querschnitt durch das abgezogene Quadrupolrohr bei dem Ausführungsbeispiel der Fig. 5 und 6 mit angeschmolzenen Folien.

Further features and advantages of the invention result from the claims and from the following description, in which exemplary embodiments are explained in detail with reference to the drawing. It shows:

• Figure 1 shows a conventional quadrupole system from four cylindrical rods which are held by insulating rings.
• Figure 2 shows a cross section through the mandrel with ground grooves, inserted foils and coated insulating tube.
• Figure 3 shows the cross section through the mandrel with molded insulating tube and fused with it.
• 4 shows a cross section through the removed quadrupole tube with melted foils;
• Fig. 5 in a similar representation as in the embodiment shown in Figures 2 to 4, a cross section through the mandrel with molded grooves in a second embodiment, with inserted films and coated insulating tube.
• FIG. 6 shows the cross section through the mandrel of FIG. 5 with the insulating tube and the foils fused to it; and
• Fig. 7 shows a cross section through the removed quadrupole tube in the embodiment of FIGS. 5 and 6 with fused foils.

In the conventional quadrupole system shown in FIG. 1, four cylindrical conductive rods, in particular made of metal, are held by two or more insulating rings. At best, an accuracy of about 3 to 4 ^μm can be obtained by mechanical adjustment. Due to natural gravity, vibrations and when the system heats up, there is a risk that the rods will bend. The system can also twist.

According to the invention, a pre-machined mandrel 1, which in the illustrated embodiment consists of ground special steel, with semicircular grooves 3 being ground in the mandrel 1, is provided with metal foils 5, in particular gold foils, by inserting the metal foils 5 into the semicircular grooves 3 become. A glass tube 7 is then pulled over the mold core 1 provided with metal foils 5 and, if necessary, closed and evacuated.

Then the glass tube 7 filled with the mandrel 1 is e.g. heated in an oven to a temperature point slightly above the transformation point of the glass, the glass tube 7 laying on the metal foils 5 in the grooves 3 and fusing with them (FIG. 3). When cooling, the mandrel 1 contracts more than the shaped glass tube 7, so that the mandrel 1 can be easily pulled out of the shaped glass tube 7.

4 shows the completely manufactured analyzer system for a quadrupole mass filter as a glass tube 7 provided with tube indentations 9, the metal foils 5 being melted onto the tube indentations 9 in the interior of the glass tube 7.

In the second exemplary embodiment shown in FIGS. 5 to 7, a preprocessed mandrel 1, in the exemplary embodiment shown consisting of ground special steel, with semicircular grooves 3 being ground in the mandrel 1, is provided with metal foils 5 by inserting them into the semicircular grooves 2 are inserted.

The metal foils 5 are provided with longitudinally extending flanges 6, which are perpendicular to the metal foil surface, on the side of the metal foil 5 which is applied to the mandrel 1. A glass tube 7 is pulled over the mold core 1 provided with the metal foils 5 and optionally closed and evacuated.

Then the glass tube 7 filled with the mandrel 1 is e.g. in an oven, heated to a temperature slightly above the transformation point of the glass, the glass tube 7 laying on the metal foils in the grooves 3. The flanges 6 dig into the soft material of the glass tube (FIG. 2).

When cooling, the mandrel 1 contracts more than the shaped glass tube 7, so that the mandrel 1 can be easily pulled out of the shaped glass tube 7.

The metal foils 5 remain firmly connected to the tube indentations 9 of the glass tube 7 formed over the grooves 3 of the mandrel 1, the hold being reinforced in particular by the flanges 6 of the metal foils 5 melted into the glass tube 7.

3 shows the completely manufactured analyzer system for a quadrupole mass filter as a glass tube provided with the tube indentations 9, the metal foils 5 being applied to the tube indentations 9 in the interior of the glass tube 7 and, in particular, being fused to the tube material by means of their flanges 6.

The same process steps are carried out if, instead of the metal foils, prior to introducing the mandrel into the raw glass tube at the locations of the tube indentations to be formed, gloss metal paste, conductive lacquer or a conductive layer is applied in a known manner and then metallized in a known manner, optionally with a conductive layer an additional metal layer is electroplated in a conventional manner.

The mandrel 1 is then introduced into the tube 7 provided with the metal coatings in such a way that the metal coatings are located above the grooves 3 of the mandrel and rest on the tube indentations 9 formed in the interior of the glass tube 7 according to the method steps described above.

The features of the invention disclosed in the above description, in the drawing and in the following claims can be essential both individually and in any combination for realizing the invention in its various embodiments.

Claims (10)

1. A method for producing a high-precision and dimensionally stable analyzer system for a multipole mass filter, in which a tube made of electrically poorly conductive, thermally softenable material is drawn over a dimensionally accurate mold core with a higher expansion coefficient and parallel grooves, whereupon the tube material is heated by the grooves of the Mold core hugs and then after solidifying cooling with the embossed tube indentations is withdrawn from the mold core, characterized in that before heating the tube between the mold core and tube in the area of the grooves layers of electrically conductive, easily connectable with the softening tube material metallic components are introduced; that the layer material is connected to the pipe material when the pipe is softened and nestled against the grooves; and that when pulling off the tube thus shaped, the layers connected to the embossed tube indentations are also removed from the mandrel. 2. The method according to claim 1, characterized in that are used as layers of metal foils, in particular made of easily fusing metal with the softenable tube material, which are inserted into the grooves of the mandrel before the tube is softened. 3. The method according to claim 1 or 2, characterized in that the tube is evacuated before softening. 4. The method according to claim 2 or 3, characterized in that glass is used as an electrically poorly conductive tube material and a metal with a largely identical coefficient of thermal expansion as the tube material, in particular a highly ductile metal, is used as foil material. 5. The method according to any one of claims 2 to 4, characterized in that the film surface is provided with a meltable coating, in particular made of glass, before insertion into the grooves of the mandrel to facilitate melting. 6. The method according to any one of claims 2 to 4, characterized in that the metal foils prior to insertion with projections extending from the film surface facing away from the mandrel, in particular in the form of bent flanges, notches, ribs soldered or welded onto the foils or to the Foils soldered wires, are provided; and that the projections are essentially melted into the softenable material. 7. The method according to claim 1 or claim 3 or 4 and 1, characterized in that a coating made of a metal-containing paste, such as shiny gold or shiny silver, is applied as a metallic component to the inner surface of the tube, which is converted into metal when the tube is heated. 8. The method according to claim 1 or according to claim 3 or 4 and claim 1, characterized in that as a metallic component, a coating of a conductive metal composition, such as conductive lacquer, gold, silver, copper or tin applied as tin oxide in the dipping process, on the inner surface the pipe is applied; and that the lead metal composition is subsequently converted to metal. 9. Analyzer system with high precision and dimensional stability for a multipole mass filter, with a tube made of electrically poorly conductive, thermally softenable material with tube indentations impressed by softening over a dimensionally precise mold core with a higher expansion coefficient and parallel grooves, in particular produced according to the method according to one of the preceding Claims, characterized in that with the tube (7), preferably a glass tube, in the interior of the tube recesses (9), foils (5) made of electrically highly conductive metal are connected. 10. An analyzer system according to claim 9, characterized in that the metal foils (5) are connected to the tube material essentially by means of projections (6) extending from the foil surface into the tube material (7).

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