DE102014101532A1 - Method for plastically deforming a plate-shaped glass body and for producing counter-bodies for the production of pressure-measuring cells - Google Patents

Abstract

A method for plastically deforming a plate-shaped glass body comprises: positioning the glass body on a support which does not support the glass body in at least one area, and heating the glass body so as to plastically deform the at least one unsupported area by thermally sinking the unsupported area wherein the thermal sinking takes place under vacuum or a protective gas atmosphere wherein the carrier has at least one graphite body on which rests the glass body, wherein a surface of the at least one graphite body on which the glass body rests, at least one recess, above which the glass body not is supported, wherein the recess is not more than 1 mm, in particular not more than 500 microns and preferably not more than 400 microns.

Description

The present invention relates to a method for plastically deforming a plate-shaped glass body and for producing counter-bodies for the production of pressure-measuring cells.

Pressure measuring cells usually comprise at least one counter-body and a measuring membrane, which is pressure-tightly joined to the counter-body, wherein the measuring membrane separates a volume into two sub-volumes, the measuring diaphragm being deflectable in dependence on the difference between the pressures prevailing in the two sub-volumes Pressure measuring cell further comprises a transducer to generate a dependent of the deformation of the measuring diaphragm signal.

Depending on the type of pressures involved, a distinction is made between absolute, relative and differential pressure measuring cells, especially in industrial process measuring technology. In the case of absolute and relative pressure measuring cells, in each case a media pressure is measured against vacuum or atmospheric pressure, while differential pressure measuring cells are used to determine the difference between a first and a second media pressure.

In particular with differential pressure measuring cells - but not only with these - there is a risk that the difference between the pressures involved can become so great that the measuring membrane is deflected too much and thus damaged. There are therefore efforts, on the one hand to limit the pressure difference between the sub-volumes, for example by hydraulic metering with overload membranes, and on the other hand to support the diaphragm by a suitable contour on the counter body to prevent further deflection.

The present invention relates to the latter alternative. A suitable contour should in particular approximate the bending line of the measuring diaphragm. Generic methods for preparing such contours in counter-bodies made of glass are in the published patent applications DE 10 2009 046 229 A1 and DE 10 2011 084 457 A1 disclosed. In essence, the contours are prepared by thermal sinking, wherein a glass body, from which the counter-bodies are to be manufactured, is heated on a support to a temperature above the glass transition temperature to let unsupported areas of the glass body sink. The counterparts thus prepared are in fact suitable for supporting a measuring membrane, for example made of silicon, well.

Due to the usually high process temperatures, which is well above the glass transition temperature of the material, which the glass body has, it can lead to cohesive connections between the glass body and the carrier, if this has a metallic material, ceramic or quartz glass, which ultimately leads to a deteriorated yield leads.

Furthermore, investigations of the inventors have shown that a control of the thermal conditions is advantageous in order to achieve a desired contour shape.

It is therefore the object of the present invention to remedy this situation.

The object is achieved by the method according to the independent claim. 1

The method according to the invention for plastically deforming a plate-shaped glass body comprises:
Positioning the glass body on a support which does not support the glass body in at least one area,
and heating the glass body to plastically deform the at least one unsupported area by thermally sinking the unsupported area,
wherein the thermal sinking takes place under vacuum or a protective gas atmosphere;
wherein the support has at least one graphite body on which the glass body rests, wherein a surface of the at least one graphite body on which the glass body rests has at least one recess over which the glass body is not supported, wherein the recess is not more than 1 mm, in particular not more than 500 microns and preferably not more than 400 microns.

In one embodiment of the invention, the graphite body is plate-shaped and has a depth which is not more than 10%, in particular not more than 5%, preferably not more than 4% of the thickness of the plate-shaped graphite body.

The plate-shaped graphite body, according to a development of the invention, for example, a thickness of not less than 5 mm, in particular not less than 8 mm and preferably about 10 mm.

In one development of the invention, the glass body is heated by the graphite body, for which purpose a heat source is arranged in particular below the graphite body, and / or wherein the graphite body is operated as a resistance heating element, that is heated by applying electrical current.

The surface of the graphite body is practically not wetted by the softened glass material of the glass body, so that there is no cohesive connection between the glass body and the graphite body.

The fact that the wells are not formed as through holes in the graphite body, but with a defined depth, the glass body is exposed to a much more homogeneous heating power from the side of the graphite body, as through holes account for a particularly different types of heat sources or heat sinks.

This leads to an unwanted contour shape.

In one development of the invention, the at least one depression is essentially rotationally symmetrical about an axis which forms a surface normal to the surface.

In a further development of the invention, the at least one depression has a depth of not more than 20%, in particular not more than 10% of the diameter of the depression, relative to the region of the surface surrounding the depression.

A typical depth of the blind holes according to the invention is for example 400 microns to 500 microns with a diameter of the recess between 3 mm and 6 mm, in particular between 4 mm and 5 mm.

In a further development of the invention, a penetration depth z ₀ of the contours is achieved by the thermal sinking, not less than 0.2% and not more than 10% of the material thickness, particularly not less than 0.5% and not more than 5% of the Material thickness of the glass body is.

According to one embodiment of the invention, the thickness of a plate-shaped glass body is not less than 500 microns, in particular not less than 700 microns and in a presently preferred embodiment about 800 microns.

For example, the sinking depth is not less than about 2 μm, in particular not less than 4 μm, and not more than 80 μm, in particular not more than 50 μm, preferably not more than 40 μm.

From the above it follows that the bottom of the recesses does not serve to support the sinking glass body, but merely causes a more homogeneous temperature distribution.

In one embodiment of the invention, the thermal sinking takes place at a temperature or temperatures which is not less than 200 ° C, in particular not less than 250 ° C and preferably not less than 280 ° C above the glass transition temperature of a glass, from which the vitreous body is formed. The glass transition temperature T _g is according to ISO 7884-8 Are defined. It is also called transformation point, or transformation temperature. The thermal expansion changes strongly around the glass transition temperature. The value of the glass transition temperature can be determined, for example, dilatometrically. For example, for the borosilicate borofloate, the glass transition temperature is T _g = 525 ° C.

For example, a borosilicate glass body may be heated to a temperature of 760 ° C and held at that temperature for a few hours to allow thermal sinking.

In one development of the invention, the thermal sinking takes place at a pressure of not more than 10 ^-4 mbar, in particular not more than 10 ^-5 mbar. The pressure values described ensure that the residual gas present, the glass body is not contaminated, and the graphite body is not oxidized. Mechanically, such a low pressure is practically negligible and does not contribute to the deformation of the glass body.

In a development of the invention, the glass body is removed from the carrier body after the thermal sinking by means of at least one suction lifter or by tilting or turning the carrier body about a horizontal axis. Of course, after the thermal sinking, the glass body can first cool down to such an extent that it achieves such a dimensional stability that it retains its shape after removal from the carrier body.

When tilting the carrier body of the glass body can slide from the carrier body, in which case the contours formed by the sinking barely oppose the sliding of the glass body resistance.

Due to the thermal sinking, a protruding contour can arise on the lower side of the plate-shaped glass body facing the carrier body for each sunken contour, the method comprising aftertreatment of the plate-shaped glass body, in which the rear side of the plate-shaped glass body is removed by removing at least the material from the protruding contour Contours are leveled.

In a further development of the invention, the method is used for producing a plurality of counter-bodies for use in the production of pressure measuring cells, which pressure measuring cells each have a flat in the equilibrium measurement membrane, and at least one counter-body, wherein the measuring membrane is pressure-tightly joined with at least one such counter-body along an encircling joint in an operational pressure measuring cell,
the method comprising deforming a plate-shaped glass body according to the method of any one of the preceding claims,
wherein the counter body comprises glass, in particular a borosilicate glass, wherein the counter body comprises a glass surface with a planar edge region to be fitted with a measuring membrane, wherein the edge region surrounds a recessed contour to support the measuring diaphragm in the event of overload, wherein the Glass surface has a surface roughness R _a <200 nm, preferably <100 nm,
wherein from the plate-shaped glass body, the plurality of counter-bodies is to prepare, and wherein the support is to be positioned on the glass body, a plurality of recesses or depressions, above each of which an unsupported portion of the glass body is arranged, the plastic deformation by thermal sinking takes place to form each of the recessed contour of a counter body.

In a further development of the invention, the depressions or recesses essentially have a circular cross-section with a diameter which is at least four times, in particular at least six times, the material thickness of the plate-shaped glass body.

In a development of the invention, the recessed contours in each case approximate the bending line of the measuring diaphragm to be joined to the counterbody.

The invention will now be explained in more detail with reference to the embodiment shown in the drawings.

Show it:

1a to 1e a sequence of process steps for deforming glass bodies and producing pressure sensors with counter-bodies comprising such glass bodies in the wafer assembly;

2 : a longitudinal section through an embodiment of differential pressure sensors in the wafer assembly with inventively prepared abutments, prior to their separation; and

3 FIG. 2: an illustration of the surface of a deformed glass body with recessed contours for counter-bodies of pressure sensors, before their separation,

First, the principle of deforming glass bodies for preparing counter bodies for pressure sensors by the step sequence in 1a to 1e briefly explained.

The illustrated sequence of manufacturing steps begins in step (a) with a graphite body 10 with a thickness of about 10 mm, in which in a first step depressions 11 to be prepared. The wells 11 can be prepared for example by micromechanical CNC milling with a depth of for example about 500 microns. On the one hand, the depressions must be so deep that a sinking glass contour does not touch the bottom of the depression; On the other hand, the depressions should not be too deep, because it affects the homogeneity in the temperature distribution. In the current estimation, the depth should in particular be less than 1.5 mm, preferably less than 1 mm.

After milling the recesses, the surface of the graphite carrier body is smoothed by means of grinding and lapping in order to be able to provide a defined support surface for the glass body.

The wells 11 , For example, are circular and have a diameter of about 4.5 mm.

In a second step (b) becomes a glass body 20 with a strength of 800 μm on the graphite body 10 positioned, with the glass body under clean room conditions loose on those with the wells 11 prepared surface of the graphite body is applied. The glass body has a borosilicate glass, for example borofloate 33 ,

In a third step (c), the stack with the graphite body 10 and the vitreous 20 over a period of about 1.5 h from room temperature in a vacuum oven at a pressure of not more than 10 ^-4 mbar especially not more than 10 ^-5 mbar heated to 750 ° C and then held at this temperature for about 5 h. During this time, on the one hand, the unsupported region of the vitreous body drops sufficiently deep, with one contour 21 produced with a depth of about 25 microns to about 30 microns, which is suitable as a membrane bed for supporting a diaphragm in case of overload. Then the stack can cool down for several hours.

The contours thus prepared were measured interferometrically, with an image of the determined contours in 3 is shown. The contours essentially satisfy a bending line course of the form (1 - (r / r ₀ ) ² ) ² , as for the edge clamped, circular-plate-shaped membranes is true.

In a fourth step (d), the glass body of the graphite body 10 taken, and the bottom of the vitreous body 20 is ground flat to the contours 21 Leveling complementary bulges. In addition, channels, for example by means of ultrasonic drilling or lasers 23 through the vitreous 20 prepared, which in particular by the vertex of the contours 21 run and serve, with the finished sensor, a pressure through the glass body 20 respectively.

In a fifth step (e) becomes a measuring membrane wafer 30 , which in particular comprises silicon, by means of anodic bonding with the glass body 20 connected in the Waferverband. Subsequently, the relative pressure sensors shown here can be separated by sawing along the illustrated vertical lines.

2 shows a longitudinal section through prepared with inventively prepared counterparts differential pressure sensors before their separation. For the production of differential pressure sensors is a membrane wafer 130 , which has silicon, between two glass bodies 120 . 140 attached in the wafer dressing by means of anodic bonding. The vitreous body 120 . 140 are previously each in the wafer association according to the preparation steps a to d 1 manufactured. Individual differential pressure sensors are finally obtained by singulation along the vertical dashed lines.

A thus prepared differential pressure sensor, for example, with a silicon measuring membrane in a thickness of 30 microns, a measuring range of 10 mbar with overload resistance against unilateral overloads of more than 100 bar, in particular more than 150 bar, since the measuring diaphragm on the contour of a counter body to Plant comes and is supported. With regard to the converter, the statements on the exemplary embodiment apply 1 Accordingly, in particular, the contours on both sides of the measuring membrane may have a measuring electrode whose capacitance C ₁ , C _{2 is} to be measured against a membrane electrode. A measure of the pressure may then be a function of the difference in capacities divided by the sum of the capacities, that is, p = p ((C ₁ -C ₂ ) / (C ₁ + C ₂ )).

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102009046229 A1 [0005]
• DE 102011084457 A1 [0005]

Cited non-patent literature

• ISO 7884-8 [0024]

Claims (13)

A method of plastically deforming a plate-shaped glass body, comprising: Positioning the glass body on a support which does not support the glass body in at least one area, and heating the glass body to plastically deform the at least one unsupported area by thermally sinking the unsupported area, wherein the thermal sinking takes place under vacuum or a protective gas atmosphere wherein the support has at least one graphite body on which the glass body rests, wherein a surface of the at least one graphite body on which the glass body rests has at least one recess over which the glass body is not supported, wherein the recess is not more than 1 mm, in particular not more than 500 microns and preferably not more than 400 microns. The method of claim 1, wherein the graphite body is plate-shaped and the depth of the recess is not more than 10%, in particular not more than 5%, preferably not more than 4% of the thickness of the plate-shaped graphite body. Method according to one of the preceding claims, wherein the glass body is heated by the graphite body, wherein the graphite body itself is acted upon from its underside with a heat source and / or operated as a resistance heating element. Method according to one of claims 2 or 3, wherein the at least one recess is substantially rotationally symmetrical about an axis which forms a surface normal to the surface. Method according to one of claims 2 to 4, wherein the at least one depression has a depth of not more than 20%, in particular not more than 10%, of the diameter of the depression with respect to the region of the surface surrounding the depression. Method according to one of the preceding claims, wherein the thermal sinking takes place at a temperature or temperatures which is not less than 200 ° C, in particular not less than 250 ° C and preferably not less than 280 ° C above the glass transition temperature of a glass from which the glass body is formed. Method according to one of the preceding claims, wherein the thermal sinking takes place at a pressure of not more than 10 ^-4 mbar, in particular not more than 10 ^-5 mbar. Method according to one of the preceding claims, wherein due to the thermal sinking on the underside facing the carrier body of the plate-shaped glass body for each sunken contour, a projecting contour, wherein the method comprises a post-treatment of the plate-shaped glass body, wherein the back of the plate-shaped glass body by removing at least of the material is leveled by the protruding contour or contours. A method for producing counter-bodies for use in the production of pressure measuring cells, which pressure measuring cells each have a flat in the equilibrium position measuring membrane, and at least one counter-body, wherein the measuring membrane is pressure-tightly joined with at least one such counter-body along a peripheral joint in an operational pressure measuring cell, wherein the method comprises deforming a plate-shaped glass body according to the method of any one of the preceding claims, wherein the counter body comprises glass, in particular a borosilicate glass, wherein the counter body comprises a glass surface with a planar edge region to be fitted with a measuring membrane, wherein the edge region is a surrounds recessed contour to support the measuring diaphragm in case of overload, wherein the glass surface has a surface roughness R _a <200 nm, preferably <100 nm, wherein from the plate-shaped glass body To prepare a plurality of counter-bodies, and wherein the support on which the glass body is to be positioned, a plurality of recesses or recesses, over each of which an unsupported portion of the glass body is arranged, the plastic deformation takes place by thermal sinking, respectively to form the recessed contour of a counterbody. The method of claim 9, wherein the recesses or recesses substantially have a circular cross section with a diameter which is at least four times, in particular at least six times the material thickness of the plate-shaped glass body. The method of claim 9 or 10, wherein the thermal sinking a sinking depth z _{0 of} the contours is achieved, the not less than 0.2% and not more than 10% of the material thickness, in particular not less than 0.5% and not more than 5% of the material thickness of the plate-shaped glass body, is. Method according to one of claims 9 to 11, wherein the recessed contours each have the bending line approximate the membrane to be mated with the counterbody. Method according to one of the preceding claims, wherein the glass body is removed after the thermal sinking by means of at least one siphon or by tilting or turning the support body about a horizontal axis of the support body.

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