Method for producing a temperature-dependent resistor, and an electric temperature sensor

Abstract

A method for producing a platinum-containing resistor, configured as a temperature sensor, includes applying a resistive coat to a ceramic support having a surface of electrically insulating material, covering an outer surface of the resistive coat with at least one layer of an electrically insulating material, which is preferably applied as a diffusion barrier in the form of an intermediate layer, and forming an electrode on the side of the resistive coat facing away from the substrate surface and spaced therefrom, using a thick-film technique. This electrode, comprising a layer of platinum, is covered by a glass passivation layer and is therefore surrounded by the electrically insulating material of the diffusion barrier and the glass passivation layer. The electrode is negatively electrically biased in relation to at least one connection of the resistive layer or the measuring resistor. An advantage is that platinum toxicants (Si- and metal ions), which are present in the form of positive ions in extreme ambient conditions, are attracted to the negative platinum layer.

We claim:  
     
         1 . A method for producing a platinum-containing, temperature-dependant resistor, configured as a temperature sensor, comprising applying a resistance layer ( 1 ) as a thick-film on a substrate having a surface made of electrically insulating material, covering an outer surface of the resistance layer ( 1 ) with at least one layer made of an electrically insulating material, which functions as a passivation layer ( 3 ) and/or as a diffusion barrier ( 10 ), and applying, an electrode ( 4 ) on a side of the resistance layer ( 1 ) facing away from the substrate surface and spaced from the resistance layer ( 1 ), the electrode ( 4 ) being electrically insulated from the resistance layer by the at least one layer of electrically insulating material.  
     
     
         2 . The method according to  claim 1 , wherein the electrode ( 4 ) is applied by a thick-film process.  
     
     
         3 . The method according to  claim 2 , wherein the electrode ( 4 ) is applied by a screen-printing process.  
     
     
         4 . The method according to  claim 2 , wherein the electrode ( 4 ) is applied by a stencil-printing process.  
     
     
         5 . The method according to  claim 1 , wherein the electrode ( 4 ) is applied by a thin-film process.  
     
     
         6 . The method according to  claim 1 , wherein the at least one layer of an electrically insulating material is applied as a diffusion barrier ( 10 ) in a form of an intermediate layer.  
     
     
         7 . The method according to  claim 1 , wherein the resistance layer ( 1 ) is applied to a ceramic mass, and is then covered with the at least one layer of electrically insulating material.  
     
     
         8 . The method according to  claim 1 , wherein the resistance layer ( 1 ) is applied to an already fired ceramic substrate as a carrier ( 2 ).  
     
     
         9 . The method according to  claim 1 , wherein the resistance layer ( 1 ) is applied on a “green” ceramic as a carrier ( 2 ), the at least one layer of electrically insulating material is applied as a ceramic mass, and the at least one layer of electrically insulating material is sintered together with the carrier.  
     
     
         10 . The method according to  claim 1 , wherein the at least one layer of electrically insulating material is applied as a laminated-on “green” ceramic and is then bonded to the carrier ( 2 ) and resistance layer ( 1 ) using a sintering process.  
     
     
         11 . The method according to  claim 1 , wherein in order to form the passivation layer ( 3 ) and/or diffusion barrier ( 10 ), the at least one layer of electrically insulating material is applied as a ceramic powder onto the resistance layer ( 1 ) using a thick-film process and is then sintered.  
     
     
         12 . The method according to  claim 1 , wherein in order to form the passivation layer ( 3 ) and/or diffusion barrier ( 10 ), the at least one layer of electrically insulating material is applied as a ceramic powder onto the resistance layer ( 1 ) using a plasma spray process.  
     
     
         13 . The method according to  claim 1 , wherein in order to form the passivation layer ( 3 ) and/or diffusion barrier ( 10 ), a plate ( 9 ) of electrically insulating material is glazed onto the resistance layer ( 1 ) or is adhered using ceramic adhesive.  
     
     
         14 . The method according to  claim 13 , wherein the plate ( 9 ) comprises ceramic.  
     
     
         15 . The method according to  claim 1 , wherein the at least one layer of electrically insulating material is applied as a passivation layer ( 3 ) and/or diffusion barrier ( 10 ) onto the resistance layer ( 1 ) in a form of a thin layer of ceramic.  
     
     
         16 . An electric temperature sensor comprising a platinum-containing resistance layer ( 1 ) made by thick-film technology, the resistance layer ( 1 ) being arranged as a measuring resistor provided with electrical contacts on an electrically insulating surface of a carrier ( 2 ) constructed as ceramic substrate, the resistance layer ( 1 ) being covered with at least one layer of an electrically insulating material for protection against contamination or damage, the at least one layer of electrically insulating material being constructed as a passivation layer ( 3 ) and/or as a diffusion barrier ( 10 ), and an electrode ( 4 ) applied on a side of the resistance layer ( 1 ) facing away from the carrier surface and spaced from the resistance layer ( 1 ), wherein at least one part of the layer of electrically insulating material is located between the electrode ( 4 ) and the resistance layer ( 1 ).  
     
     
         17 . The electric temperature sensor according to  claim 16 , wherein the diffusion barrier ( 10 ) has a form of an intermediate layer.  
     
     
         18 . The electric temperature sensor according to  claim 17 , wherein a thickness of the intermediate layer lies in a range of about 0.2 μm to 50 μm.  
     
     
         19 . The electric temperature sensor according to  claim 16 , wherein the electrode ( 4 ) is arranged between the passivation layer ( 3 ) as a covering layer and the intermediate layer as the diffusion barrier ( 10 ).  
     
     
         20 . The electric temperature sensor according to  claim 16 , wherein the electrode ( 4 ) is covered by the passivation layer ( 3 ).  
     
     
         21 . The electric temperature sensor according to  claim 16 , wherein the electrode ( 4 ) is arranged on a side of the passivation layer ( 3 ) facing away from the resistance layer ( 1 ).  
     
     
         22 . The electric temperature sensor according to  claim 16 , wherein the electrode ( 4 ) is provided with an external electric connection.  
     
     
         23 . The electric temperature sensor according to  claim 16 , wherein the electrode ( 4 ) is electrically negatively biased and/or has an electrically negative potential relative the resistance layer ( 1 ).  
     
     
         24 . The electric temperature sensor according to  claim 16 , wherein the electrode ( 4 ) has a form of a layer.  
     
     
         25 . The electric temperature sensor according to  claim 16 , wherein the electrode ( 4 ) comprises a platinum-containing layer.  
     
     
         26 . The electric temperature sensor according to  claim 16 , wherein the electrode ( 4 ) comprises platinum.  
     
     
         27 . The electric temperature sensor according to  claim 16 , wherein the carrier ( 2 ) comprises Al 2 O 3 .  
     
     
         28 . The electric temperature sensor according to  claim 17 , wherein the diffusion barrier ( 10 ) comprises Al 2 O 3 .  
     
     
         29 . The electric temperature sensor according to  claim 17 , wherein the diffusion barrier ( 10 ) comprises MgO.  
     
     
         30 . The electric temperature sensor according to  claim 17 , wherein the diffusion barrier ( 10 ) comprises tantalum oxide.  
     
     
         31 . The electric temperature sensor according to  claim 17 , wherein the diffusion barrier ( 10 ) comprises a mixture of Al 2 O 3  and MgO having a weight percentage of Al 2 O 3  in a range of about 20% to 70%.  
     
     
         32 . The electric temperature sensor according to  claim 17 , wherein the diffusion barrier ( 10 ) comprises a layer system having a layer sequence of at least two layers, respectively comprising at least one oxide selected from the group consisting of Al 2 O 3 , MgO, and Ta 2 O 5 .  
     
     
         33 . The electric temperature sensor according to  claim 32 , wherein at least one layer of the layer system comprises two oxides.  
     
     
         34 . The electric temperature sensor according to  claim 17 , wherein the diffusion barrier ( 10 ) is made by a magnetron sputtering process selected from the group consisting of PVD (Physical Vapor Deposition), IAD (Ion Assisted Deposition), IBAD (Ion Beam Assisted Deposition), PIAD (Plasma Ion Assisted Deposition), and CVD (Chemical Vapor Deposition).  
     
     
         35 . The electric temperature sensor according to  claim 16 , wherein the passivation layer ( 3 ) comprises a mixture of SiO 2 , BaO and Al 2 O 3  having a weight percentage of SiO 2  lying in a range of about 20% to 50%.