Dispersion electrolyte for graphite-containing layers

Abstract

The invention relates to a dispersion electrolyte for the electrodeposition of graphite-containing tin, nickel or tin-nickel layers, to a method for the electrodeposition of such a graphite-containing layer, to a metal substrate coated with such a graphite-containing layer, and to the use of the dispersion electrolyte. The dispersion electrolyte comprises Sn2+ ions and/or Ni2+ ions, graphite particles, at least one anionic dispersant, a complexing agent for Sn2+ and Ni2+ ions, a conducting salt and water, and has a pH of 4 to 7.

1 . A dispersion electrolyte for the electrodeposition of graphite-containing tin layers, graphite-containing nickel layers or graphite-containing tin-nickel layers, comprising:
 Sn 2+  ions at a concentration of 2 to 50 g/L and/or Ni 2+  ions at a concentration of 0.2 to 70 g/L;   graphite particles at a concentration of 5 to 200 g/L;   at least one anionic dispersant at a concentration of 1 to 25 g/L;   a complexing agent for Sn 2+  and Ni 2+  ions;   a conducting salt; and   water,   
       wherein the electrolyte has a pH of 4 to 7. 
     
     
         2 . The dispersion electrolyte according to  claim 1 , wherein:
 (i) the electrolyte contains Sn 2+  ions at a concentration of 5 to 45 g/L, and/or Ni 2+  ions at a concentration of 10 to 65 g/L; or   (ii) the electrolyte contains graphite particles at a concentration of 20 to 150 g/L.   
     
     
         3 . (canceled) 
     
     
         4 . The dispersion electrolyte according to  claim 1 , wherein the Ni:graphite weight ratio in the electrolyte is 1:0.5 to 1:2, or the Sn:graphite weight ratio in the electrolyte is 1:0.5 to 1:5. 
     
     
         5 . The dispersion electrolyte according to  claim 1 , wherein the graphite particles have a median (d50) particle size of 20 nm to 20 μm. 
     
     
         6 . The dispersion electrolyte according to  claim 1 , wherein the dispersant is at least one selected from sulfate compounds having an alkyl group, an aralkyl group or an aromatic group in each case having 6 to 24 carbon atoms; sulfonate compounds having an alkyl group, an aralkyl group or an aromatic group in each case having 6 to 24 carbon atoms; and polymers containing carboxy or carboxylate groups. 
     
     
         7 . The dispersion electrolyte according to  claim 6 , wherein the sulfate compounds having an alkyl group having 6 to 24 carbon atoms are selected from fatty alcohol sulfates, fatty alcohol polyether sulfates and combinations thereof, and/or the sulfonate compounds are polymers having aromatic sulfonate groups, wherein the underlying aromatic groups each have 6 to 14 carbon atoms. 
     
     
         8 . The dispersion electrolyte according to  claim 1 , wherein the dispersant is present in the electrolyte at a concentration of 2 to 20 g/L. 
     
     
         9 . The dispersion electrolyte according to  claim 1 , wherein:
 (i) the complexing agent is an organic compound having at least three functional groups selected from amino groups, carboxy groups and carboxylate groups;   (ii) the complexing agent is an organic compound having at least two of the functional groups are amino groups selected from primary, secondary and tertiary amino groups;   (iii) the complexing agent is at least one selected from EDTA, DETA, DOTA and DOTATOC; or   (iv) the complexing agent is present in the electrolyte at a concentration of 5 to 70 g/L.   
     
     
         10 . (canceled) 
     
     
         11 . The dispersion electrolyte according to any of claims  1  to  10 , wherein:
 (i) the conducting salt is at least one selected from sodium chloride, potassium chloride, ammonium chloride, sodium acetate, potassium acetate, ammonium acetate, ammonium fluoride, ammonium bifluoride, sodium fluoride and potassium fluoride, and, for the electrodeposition of graphite-containing tin-nickel layers, 
 (ii)) the conducting salt comprises a fluoride-containing conducting salt; or 
 (iii) the conducting salt is present in the electrolyte at a concentration of 5 to 70 g/L. 
 
     
     
         12 . (canceled) 
     
     
         13 . A method for the electrodeposition of a graphite-containing tin layer, a graphite-containing nickel layer or a graphite-containing tin-nickel layer, comprising the electrodeposition of the graphite-containing layer on a metal substrate, using the dispersion electrolyte according to  claim 1  at a temperature of 50 to 85° C. 
     
     
         14 . The method according to  claim 13 , wherein deposition is carried out at a current density of 0.1 to 10 A/dm 2 . 
     
     
         15 . The method according to  claim 13 , wherein the graphite-containing layer is deposited with a layer thickness of 4 to 30 μm. 
     
     
         16 . A coated metal substrate, wherein the metal substrate is coated with a graphite-containing tin layer, a graphite-containing nickel layer or a graphite-containing tin-nickel layer, wherein the graphite-containing layer contains 0.1 to 8 wt % graphite relative to the total weight of the graphite-containing layer. 
     
     
         17 . The coated metal substrate according to  claim 16 , wherein;
 (i) the graphite-containing layer contains 0.5 to 3 wt % graphite relative to the total weight of the graphite-containing layer; or   (ii) the graphite-containing layer is a graphite-containing nickel layer which has a mean coefficient of friction of 0.4 or less, and a Vickers hardness of at least HV 300   
     
     
         18 . (canceled) 
     
     
         19 . The coated metal substrate according to  claim 16 , wherein the graphite-containing layer is a graphite-containing tin-nickel layer and has a nickel content of 10 to 40 wt % relative to the metals tin and nickel. 
     
     
         20 . The coated metal substrate according to  claim 19 , wherein;
 (i) the graphite-containing tin-nickel layer has a nickel content of 32 to 37 wt % relative to the metals tin and nickel, and also has a Vickers hardness of at least HV 200;   (ii) the graphite-containing tin-nickel layer has a mean coefficient of friction of 0.4 or less.   
     
     
         21 . (canceled) 
     
     
         22 . The coated metal substrate according to  claim 19 , wherein the contact resistance of the graphite-containing tin-nickel layer in relation to a gold contact at 25° C. is 50 mΩ (mOhm) or less. 
     
     
         23 . A method of the dispersion electrolyte according to  claim 1 , comprising producing an electronic component having a graphite-containing tin layer, a graphite-containing nickel layer or a graphite-containing tin-nickel layer. 
     
     
         24 . The method according to  claim 23 , wherein the electrolyte is used to produce a graphite-containing tin-nickel layer as a protective layer on a contact or an electrode. 
     
     
         25 . The dispersion electrolyte according to  claim 2 , wherein:
 (i) the electrolyte contains Sn 2+  ions at a concentration of 20 to 30 g/L, and/or Ni 2+  ions at a concentration of 50 to 65 g/L; or   (ii) the electrolyte contains graphite particles at a concentration of 40 to 100 g/L.