METHOD FOR PRODUCING A LAYER STRUCTURE USING A PASTE ON THE BASIS OFA RESISTIVE ALLOY

Abstract

The present invention concerns a layer structure comprising: a substrate having a glass or ceramic surface, a layer A at least partially covering the glass or ceramic surface of the substrate, wherein layer A comprises a glass in which at least two mutually different elements are contained as oxides, and a layer B at least partially covering the layer A. Layer B comprises: a resistance alloy having a temperature coefficient of electrical resistance less than 150 ppm/K, and optionally a glass containing at least two mutually different elements as oxides. Layer B contains not more than 20 weight percent of glass based on the total weight of layer B.

Claims

1. Method for producing a layer structure comprising the successive steps: a. Providing a substrate having a glass or ceramic surface, b. Applying a paste A to at least a portion of the glass or ceramic surface of the substrate to obtain a layer of paste A, wherein paste A contains the following constituents: I. a glass frit containing at least two mutually different elements as oxides and having a transformation temperature Tg in the range of 600 to 750° C., and II. an organic medium, c. Drying and, if necessary, burning of the layer of paste A d. Applying a paste B to at least part of the layer from step c. to obtain a layer of paste B, wherein paste B contains the following constituents: I. A resistance alloy powder having an electrical resistance temperature coefficient of less than 150 ppm/K II. an organic medium, III. 0-15% by weight glass frit, based on the total weight of paste B, and e. Burning and optional drying of the layers of paste B before burning.

2. Method according to claim 1, characterized in that paste B contains a glass frit which contains at least two mutually different elements as oxides.

3. Method according to any of claim 1 or 2, characterized in that paste B contains not more than 12 weight percent and preferably 5-12 weight percent glass frit based on the total weight of paste B.

4. Method according to any one of claims 1-3, wherein the resistance alloy of the paste B has a temperature coefficient of electrical resistance of less than 50 ppm/K.

5. Method according to any of claims 1-4, wherein the resistance alloy of the paste B is selected from the group consisting of: Alloy I. a. 53.0-57.0 weight percent copper, b. 42.0-46.0 weight percent nickel, c. 0.5-1.2 weight percent manganese and d. Not more than 10000 ppm by weight of other elements. Alloy II. a. 83.0-89.0 weight percent of copper, b. 10.0-14.0 weight percent manganese, c. 1-3 weight percent nickel and d. Not more than 10000 ppm by weight of other elements. Alloy III. a. 88.0-93.0 weight percent of copper, b. 5.0-9.0 weight percent manganese, c. 2-3 weight percent of tin and d. Not more than 10000 ppm by weight of other elements. Alloy IV. a. 61.0-69.0 weight percent of copper, b. 23.0-27.0 weight percent manganese, c. 8-12 weight percent nickel; and d. Not more than 10000 ppm by weight of other elements. and Alloy V. a. 70.0-78.0 weight percent nickel, b. 18.0-22.0 weight percent chromium, c. 3-4 weight percent aluminium, d. 0.5-1.5 weight percent silicon, e. 0.2-0.8 weight percent manganese, f. 0.2-0.8 weight percent iron, g. Not more than 10000 ppm by weight of other elements.

6. Method according to any of claims 1-5, characterized in that paste A contains 50-90% by weight glass frit and 10-50% by weight organic medium based on the total weight of glass frit and organic medium.

7. Method according to any of claims 1-6, characterized in that the glass frits of paste A and/or paste B each contain silicon, boron, aluminum and an alkaline earth metal as oxide.

8. Method according to any of claims 1-7, characterized in that the glass frit of paste B contains at least two elements as oxides which are contained in the glass frit of paste A.

9. Method according to any of claims 1-8, characterized in that paste B comprises 60-95 weight percent of the resistance alloy, 3-15 weight percent of glass frit and 2-37 weight percent of organic medium, based on the total weight of paste B.

10. Layer structure comprising: a. a substrate having a glass or ceramic surface, b. a layer A at least partially covering the glass or ceramic surface of the substrate, wherein layer A comprises a glass in which at least two mutually different elements are contained as oxides and which has a transformation temperature Tg in the range of 600 to 750° C., c. a layer B which at least partially covers layer A, wherein layer B comprises the following constituents: I. a resistance alloy having a temperature coefficient of electrical resistance less than 150 ppm/K, and II. optionally a glass containing at least two different elements as oxides, wherein layer B contains not more than 20 weight percent of glass based on the total weight of layer B.

11. Paste comprising a. a powder of a resistance alloy having a temperature coefficient of electrical resistance of less than 150 ppm/K b. a glass frit comprising silicon, boron, aluminum and an alkaline earth metal each as oxide, c. an organic medium.

12. Paste according to claim 11, characterized in that the alkaline earth metal is calcium.

13. Paste according to one of claim 11 or 12, characterized in that the glass frit is prepared from a. 25-55 weight percent silicon oxide, b. 20-45 weight percent calcium carbonate, c. 10-30 weight percent of aluminium oxide; and d. 1-10 weight percent boron oxide.

14. Use of the layer structure according to claim 10 for the production of precision resistors.

Description

EXAMPLES

[0055] General Production of Paste A

[0056] Pastes A were prepared by mixing 22% by weight organic medium (85% by weight texanol, 15% by weight ethyl cellulose (75% N7, 25% N50)) and 78% by weight glass frit according to Table 1. The pastes were homogenized using a three-roll chair.

TABLE-US-00006 TABLE 1 Glasses used Glas frit Glas frit Glas frit Glas frit Glas frit Glas frit Glas frit 1 2 3 4 5 6 7 Weight % Weight % Weight % Weight % Weight % Weight % Weight % SiO2 43.0  50.0  48.0  16.8  43.0  57.0  42.0  Al2O3 9.0 10.0  10.0  9.0 12.0  18.0  MgO 3.0 2.0 3.0 CaO 6.0 10.0  8.0 6.0 9.0 35.0  SrO 5.0 22.0  5.0 BaO 30.0  9.0 5.0 47.8  30.0  Na2O 1.0 K2O 2.0 4.0 2.0 2.0 5.0 B2O3 2.0 15.0  4.0 35.5  2.0 17.0  5.0 Sum 100.0  100   100.0  100.0  100   100   100.0 

[0057] General Production Pastes B

[0058] A powder of the resistance alloy isotane (mean particle diameter d50: 8 μm, produced by gas atomization of a melt under N2 atmosphere), an organic medium (65 wt. % texanol and 35 wt. % acrylate binder) and, if necessary, a glass frit were added in the specified quantities and homogenized by means of a three-roll chair. The produced pastes have a viscosity of about 30-90 Pas at 20-25° C.

TABLE-US-00007 TABLE 2 weight % Glas frit 7 Isotan powder Organic medium Paste B1 6 84 10

[0059] Production of the Layer Structure

[0060] The glass pastes A, containing the glass frits from Table 1, were applied by screen printing to Al.sub.2O.sub.3 substrates with a size of 101.6×101.6 mm and a thickness of 0.63 mm (Rubalit 708 S, CeramTec). A screen from Koenen GmbH, Germany was used with an EKRA Microtronic II printer (type M2H). The emulsion thickness was about 50 μm (sieve parameters: 80 mesh and 65 μm wire diameter (stainless steel)). Printing parameters: 63 N doctor blade pressure, doctor blade speed 100 mm/s and a jump of 1.0 mm. The layer thickness after printing (wet) was about 90 μm. 10 minutes after printing, the samples were dried in an infrared belt dryer (BTU international, type HHG-2) for 20 min at 150° C. The drying time was about 10 minutes. The layer thickness after drying was about 60 μm. The printed glass layers were burned under nitrogen atmosphere (N2 5.0) in a furnace (ATV Technologie GmbH, type PEO 603). The temperature was increased from 25° C. to 850° C., kept at 850° C. for 10 and then cooled down to 25° C. within 20 min. The layer thickness after burning was about 50 μm. The resistance alloy paste B was applied to the previously produced layer by screen printing. A screen from Koenen GmbH, Germany was used with an EKRA Microtronic II printer (type M2H). The emulsion thickness was about 50 μm, sieve parameters: 80 mesh and 65 μm wire diameter (stainless steel).

[0061] The printed resistance alloy pastes (including the precursor) were burned in a nitrogen atmosphere (N2 5.0) in a furnace (ATV Technologie GmbH, type PEO 603). The temperature was increased from 25° C. to 900° C., kept at 900° C. for 10 min and cooled down to 25° C. within 20 min (total cycle time 82 min). The layer thickness after burning was about 50 μm.

Example 1

[0062]

TABLE-US-00008 TABLE 3 Adhesion tests with glass pastes (Paste A) with different glass frits Adhesion Isotan on Substrate + = good; Layer Glas frit Isotan- ∘ = moderate; structure Substrate (Paste A) Paste − = bad 1 Al.sub.2O.sub.3 1 Paste B1 + 2 2 (6% Glas 7) + 3 3 + 4 4 + 5 5 + 6 6 + 7 7 + 8 no Glas −

Example 2

[0063] Adhesion Layer Structure as a Function of the Amount of Glass in Paste B

TABLE-US-00009 TABLE 4 Resistance alloy pastes (paste B) with different glass frit content Isotan Organic [weight %] Glas frit 7 powder medium Paste B2 0 90 10 Paste B3 3 87 10 Paste B4 6 84 10 Paste B5 9 81 10

TABLE-US-00010 TABLE 5 Adhesion layer structure as a function of the amount of glass in paste B before and after T-Shock Positioning Adhesion Detachment before T- after Layer Glas layer Alloy layer Shock T-Shock structure Substrate (layer A) (layer B) storage storage  9 Al.sub.2O.sub.3 Paste A Paste B2 good  20 Cycles 10 from glas 7 Paste B3 good  100 Cycles 11 Paste B4 good >500 Cycles 12 Paste B5 good >500 Cycles

[0064] T-Shock Storage:

[0065] The manufactured layer structures were each stored for 15 min in a chamber with a temperature of −40° C. or +150° C. The temperature of the storage chamber was −40° C. or +150° C. respectively. The transition from one chamber to the other was automated and took approx. 4 s. One cycle includes one storage at −40° C. and one at +150° C. The other cycle was automated. The adhesion was checked after different numbers of cycles with an adhesive tape as described above.

[0066] For layer structure 9 and layer structure 12, the TCR values were measured in the temperature range 20-60° C. according to the standard DIN EN 60115-1:2016-03 (drying method I):

TABLE-US-00011 TABLE 6 Layer structure Amount glas frit in paste B TCR  9 0 weight % −25 bis −14 ppm/K 12 9 weight % −37 bis −21 ppm/K

[0067] For comparison The TCR bulk value for isotane (as wire) is in the range of −80 to +40 ppm/K.