DE2135455A1 - Piezoresistorubträgerer and in front of devices with semiconductor layers and their manufacturing processes - Google Patents

Description

Piezoresistor B over-pullers and devices with semiconductor layers and their manufacturing processes

The present invention relates to piezoresistive transmitters and devices for the electrical measurement of mechanical changes in shape, as well as methods for their production.

Devices are known for measuring mechanical changes in shape by means of transmitters due to changes in the electrical resistance of wires and semiconductors. The main disadvantage of wire devices and transmitters is that their proportionality factor of the strain gauge G »dB / R S, where E is the electrical resistance of the transfer and / the uniaxial change in shape, has the maximum value of about 2.5. Although this disadvantage does not apply to monocrystalline

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linear semiconductor devices see the said factor at them is about 100, but with them there is the difficulty that the transmission elements of small dimensions, which are suitable for such uses are difficult to manufacture, especially cut to size. Also show these devices suffer from a high degree of fragility and a limited range of nominal values for E, as well as the disadvantage of a heat coefficient of the proportionality factor of the strain gauge or the electrical resistance, which is about two orders of magnitude higher than that of the metallic fixtures.

There are transmitters with semiconductor layers on a laboratory scale are produced with non-oriented or preferably surface-oriented crystallites, their IMS proportionality factor to I / 3 or 1/2 of the corresponding value in the case of monocrystalline devices, which, however, have a heat coefficient of the factor and electrical resistance of around an order of magnitude lower than that of the monocrystalline. Such transformers have less satisfactory adhesion to glass or mica substrates. Further disadvantages are the streaky manufacturing process for the electrodes and the stability of the electrodes that is not guaranteed Clamps after only mediating their attachment to the electrodes Colloidal silver paste is made.

The inventive method eliminates the disadvantages of

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Piezoresistive transmitters and devices by applying

in the

supply of vacuum of polycrystalline germanium strips between metal electrodes on various non-conductive or conductive substrates, such as. B. mica, kapton, steel foils, etc.

According to the present method, the metal electrodes are placed on the base applied, either from a conductive colloidal silver paste or from Ag, Pt, Al, Au, Ni, etc. layers exist; the application of the germanium layers is carried out under vacuum, preferably under the best possible pressure P * C5> 10 ^ Torr, at a temperature of the substrate between 3OO and 700 ° C, the rate of increase in germanium layer thickness less than 2000 Å / minute and the attachment the clamps to the base either by spot welding or by means of conductive colloid paste and the mechanical stability by soldering the terminals to the electrodes by means of a polymer, for example an epoxy polymer, and the uniform operation is ensured by means of a heat-resistant protective varnish is.

The base can consist of any suitable insulating material, for example mica or Kapton (this is the trade name of a plastic based on Teflon or Mylar, which is used as a non-conductive base, for example is used in microelectronics), or from a

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conductive material, such as carbon steel or stainless steel Steel to which a non-conductive layer of heat-resistant enail is applied using a process known per se.

In the following, @ BÄ @ a will @ a three - non-limiting - exemplary embodiments for the production of transformers according to the invention and of devices provided with such transmitters on non-conductive or metallic substrates with reference on drawings that show:

SIg. 1 Grandmas of a device with a transfer device attached9 by gluing on a non-conductive surface ^ ,

ELgo 2 longitudinal section PP ¹ in elevation according to Hg. 1 of the device

3 Longitudinal section in elevation of a device with on metal lisch © underlay with an insulating intermediate layer applied to the transformer.

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3 first © llöB.g © ia © 2? Device with on non-conductive surface applied transformer It. Pig. 1 and 2:

Two conductive electrodes 2 made of colloidal silver paste are placed on a mica base 1, between 10 and 1000 microns thick, previously purified using detergents, absolute alcohol, water and water, between 10 and 1000 microns thick, along the outlines of a stencil placed under the mica base.

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brought. The surface and spacing of the electrodes are selected depending on the desired electrical resistance of the device, which may be between 1.10 and 1.10. The thickness of the polycrystalline germanium layer must be between 0.05 and 2 microns. The base prepared for this catfish is glued on the electrode-free side using the same colloidal silver paste on the surface of a copper furnace, whereby care must be taken that the gluing only takes place on the active zone of the elements. A large number of documents can be glued onto the same oven. Then the inactive surface of each element as well as the outer halftone of the electrodes are covered with a 20 micron thick aluminum foil strip small pieces of polycrystalline germanium can be attached by pressing in. The substrates are degassed at 500 to 600.degree. C. for ^{10 to 40 minutes under vacuum at ρ <5.10 y Torr.}

Then the previously degassed germanium is evaporated to a temperature between 4-70 and 500 ° C held documents deposited, with a vapor deposition rate below 2000 Å / minute, whereby the polycrystalline Layer 3 is obtained.

After separating the elements thus obtained from the Open the furnace by means of a transparent rubber band 4 · the silver wire clips 5 to the pad in the non-active area in such a way

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attached that the electrical contact between electrodes and terminals is made by gluing using colloidal silver paste 6 will. The whole surface of the G-limmer pad becomes Covered with a protective lacquer 7 on the side on which the piezo resistor element is applied. Then that gets to this Veise manufactured element according to the outlines of the mica layer cut out «. Thereupon the sorting will include oaks of the obtained piezoresistive devices.

If Kapton pads are used, the operations are almost identical to that of the Embers, the difference consists only in the surface temperature of the polycrystalline Germanium. During the application, the substrate is kept at an iron temperature of 300 to 375 ° C.

Example 2

Production of a device with a transmitter applied to a metal base It. Fig. 3 ',

A heat-resistant 0.4 mm thick layer is poured through onto a metal base made of carbon steel with a _{thickness of at least 0 5} 1 mm, which has been degreased and pickled using detergent or sulfur or hydrochloric acid and then neutralized and dried using sodium carbonate, borax and sodium nitrate simple atomization or in an electrostatic field, or again applied by electrophoresis. After air drying at 120 ° G, the substrate is placed in an oven preheated to 800 to 8 ^ 0 ° C for 3 to 4 minutes in the furnace.

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zone introduced. On the opposite side to that on which the transmitter is applied, which can come into contact with a corrosive medium, the surface can be protected either with a stainless steel layer 10 or a layer of heat- and acid- or alkali-resistant enamels. The base prepared in this way is glued with the opposite side to that on which the transformer is deposited on a copper furnace using the conductive colloidal silver paste. After the paste has dried out, the electrodes 11 made of colloidal silver paste or gold plating solution are painted on using a template. Then the inactive surface of the element and the outer halves of the electrodes are uncovered by means of 20 micron thin aluminum foil strips. On each pad more transducers 12 can be applied, where ^v egg that painting the ^ electrodes and masking each NaCN the conditioned by the geometry of the transformer needs to be performed so as necessary. A filament of 0.2 to 0.5 mm diameter tungsten wire is now braided and small pieces of polycrystalline German are pressed into the mesh. The documents will be at 470 ° to 550 ° C * ⁵ lorr degassed for 30 to 40 minutes under vacuum at a Bestdruck of P <5 "10". Then, the previously degassed Uarmanium ⁷ is applied underlay by vacuum evaporation on the email covered metal, wherein the ! The temperature of the substrate «* during vapor deposition is between 470 and 530 ° C and the

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The evaporation rate is less than 2000 bpm.

To. Taking out the pad with the applied transformer are fixed the terminals 13 ^a US silver wire of 0.1 mm diameter on the uncovered side of the electrodes with silver paste, after which the whole übertragereHement is covered with a heat-resistant paint fourteenth

Example 5

Manufacture of a device with the transformer on a solid metal base:

As in Example 2, an enamel layer with a maximum thickness of 0.1 mm is applied to the surfaces of a steel parallelepiped Dimensions, for example 10 χ 10 χ 15 mm applied « Using a suitable template, Au electrodes made from a gold plating solution are applied to the enamel Paint and ice treatment stopped at 700 ° C for 5 minutes. The sample produced in this way is covered accordingly, for example by means of aluminum foil, and in a corresponding manner sized tantalum boat placed with which the sample under vacuum up to a temperature of 350 to 400 ° C and is heated at an Eestdruck ρ <5 »10 ^ Torr. On the so prepared base, the layer of polycrystalline germanium is applied as in Example 2. Afterwards the Contacts applied and the device covered with heat-resistant paint, again as in Example 2.

The device obtained in this way can be used for measuring voltages, for signaling limit voltages as well can be used for other tensometric measurements.

The present invention offers the following advantages:

- Achieving a proportionality factor of the strain gauge G- ⁴ Z 30, a linear change from dB / R to -J, as well as a heat coefficient of said factor and the electrical resistance between -1.10 ~ * and -6.10 " ^μ grd, or between -1.10 "^ and -5> 10 ~ ⁴ deg ~ ¹ i

- Achievement of a good time stability for both H and for the factor G; the resistance of R is better than

- 0.2 % in 24 hours at 20 ° 0; and that of G better than ± 0.05 % in 24 hours at 20 ° Ο;

- The polycrystalline layer adheres more firmly to the base, which enables measurements to be carried out even with large mechanical deformations, the maximum permissible deformation being 1.10 ""*; the deviation from linearity for uniaxial deformations,] between 6.10 ~ ⁵ and 10.1ο "" ⁴ is less than 0.2 % \

- the raw material used is polycrystalline germanium, which is much cheaper than the monocrystalline j

- Achieving well-fastened terminals, which ensures perfect electrical contact and strength j

- Good protection of the device against external influences

- the more secure attachment of the transformer to the piece, the deformation of which is to be measured, is guaranteed in this way.

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- 10 -

ensures that both practically form a single whole;

- Achievement of a carbon steel, stainless steel base Steel or a layer adhering to steel-clad substrates, which is free of pinholes and heat-resistant, which means the deposition of the active element and the electrodes on the same is enabled;

- The device can be used in corrosive media by using a corrosion-resistant enamel or stainless steel Steel is protected;

- The correctness of the measurements is guaranteed by not gluing the transformer, but directly on the metal base is deposited by means of the enamel layer;

- Obtaining a diverse series of shapes and geometries Dimensions and electrical resistances.

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Claims (6)

- 11 claims 1.) Process for the production of devices with piezoresistive transmitters with semiconductor layers made of polycrystalline germanium, characterized in that on non-conductive or metallic substrates coated with a heat-resistant enamel, metallic electrodes made of conductive Colloidal silver or metallic layers are applied over and between which a polycrystalline germanium layer is applied under vacuum and metal wire clips are soldered, after which the device obtained in this way by means of a heat-resistant lacquer is sealed. 2. The method according to claim 1, characterized in that the non-conductive layer is heat-resistant, optionally also acid- or alkali-resistant enamels on a metallic one Carbon steel or stainless steel base in the oven at 800 to 900 ° C for 3 to 4 minutes is baked in the burning zone and is 0.4 mm thick owns. 3. The method according to claims 1 and 2, characterized in that that the metal electrodes are at temperatures between 330 and 600 ° C by evaporation under vacuum at a Residual pressure ρ -c 5j10 ~ ^ Torr can be applied over that the polycrystalline germanium layer on the 10 9 8 8 4/1 3ü 1 Temperatures of 35O to 600 ° C held documents are applied, the evaporation rate of the polycrystalline layer not exceeding 2000 S / minute. 4. The method according to claims 1 and 2, characterized in that the metal electrodes are made of colloidal silver paste at room temperature be applied. "5. Devices with piezoresistive transmitters, characterized in that that on a non-conductive surface, for example made of mica or Kapton, there are two metal electrodes which are made either of conductive colloidal silver paste or of layers of Ag, Pt, Al, Au, Ni, Mo etc. exist, over and between which the polycrystalline germanium layer is deposited, wherein the clamps either by spot welding or by means of Colloidal silver paste is attached to the electrodes by gluing with a polymer, preferably an epoxy resin are, whereupon the whole thing is sealed with a heat-resistant lacquer. 6. Device with piezoresistive transmitter, characterized in that that on a metal base, for example made of carbon steel or stainless steel a heat-resistant layer is located, over which two metal electrodes either made of conductive Ag-, Au-, Pt-KoI-loidpaste or from layers of Ag, Pt, Al, Au, Ni, MoAxsv. 10988 A / 136 1 QaKIiN INSPECTED are applied, above and between which there is a polycrystalline Germanium layer is located, the terminals being attached to dfcto electrodes either by spot welding or by means of silver paste, and by gluing to the base by means of a polymer, preferably an epoxy resin are attached and the whole thing is sealed by means of a heat-resistant lacquer. 10988A / 1361 eerseite