Nickel-iron electrolytes
Nickel - iron electrolytes were previously used in electroplating to save nickel. Today they are used as electrolytes in microsystem technology , see also LIGA (manufacturing process) .
Compared to nickel layers deposited from conventional nickel sulfamate electrolytes, galvanically deposited nickel- iron layers have increased abrasion resistance.
composition
Nickel-iron electrolytes largely correspond to the Watts nickel electrolyte type.
It consists of:
| material | Molecular formula | concentration |
|---|---|---|
| Nickel (II) sulfate | NiSO 4 • 6H 2 O | 240-310 g / l |
| Nickel sulfamate | Ni (SO 3 NH 2 ) 2 · 4H 2 O | 120-128 g / l |
| Iron (II) sulfate | FeSO 4 • 7H 2 O | 20-50 g / l |
| Boric acid | H 3 BO 3 | 20-40 g / l |
| Saccharin , N-methyl saccharin | C 7 H 5 NO 3 S | 0.1 - 1 g / l |
| Sodium lauryl sulfate , fluorosurfactant | C 12 H 25 NaO 4 S | 0.5 g / l |
| Ascorbic acid | C 6 H 8 O 6 |
Nickel (II) sulphate is the main metal supplier. The boric acid serves as a buffer substance , which means that it keeps the pH value within a certain range. The pH value is kept at 2-3.1 by adding half-concentrated sulfuric acid . The deposition takes place at 50–55 ° C with current densities of 0.5–3.0 A / dm². S-depolarized nickel is used as the anode. Iron must be replenished in divalent form, so constant iron control of the electrolyte is necessary. Since divalent iron compounds are sensitive to oxidation, the electrolyte must be stored under protective gas. The iron content of the layers can be regulated by the current density and the iron (II) content of the electrolyte. It has proven to be beneficial to use perfluorinated compounds as surfactants , since normal surfactants are broken down more quickly by electrolysis. Ascorbic acid reduces any iron (III) present. Saccharin (sodium salt) acts as a tension regulator.
swell
Nickel alloys with iron, cobalt and phosphorus:
- B. Loechel, S. Jung, H. Zimer, H.-M. Heuck, J. Chlebek: Electrodeposited Alloys of Ni, Fe, Co, and P for High Aspect Ratio Microstructures. In: Michael Matlosz: Fundamental Aspects of Electrochemical Deposition and Dissolution (= Electrochemical Society. Electrodeposition Division. Proceedings. 99, 33). Electrochemical Society, Pennington NJ 2000, ISBN 1-56677-256-7 , pp. 307-316.
Nickel-iron alloys for mold inserts
- A. Fath, W. Leskopf, K. Bade, W. Bacher: Development of mold inserts made of nickel-iron alloys for the molding of microstructures made of high-performance plastics . In: Electroplating . tape 91 , no. 6 , 2000, ISSN 0016-4232 , p. 1690-1697 .
Residual stresses in nickel-iron alloys