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material strip. Cathode screens or masks may be applied between the two to
focus the electrical field onto closely defined spots on the cathode strip.
Special high performance electrolytes are used in selective electroplating to
reach short plating times and allow a high flow rate of the electrolyte for a fast
electrolyte exchange in the actual coating area.
For a closely targeted electroplating of limited precious metal coating of contact
springs so-called brush-electroplating cells are employed ''(Fig. 7.1)''. The “brush”
or “tampon” consists of a roof shaped titanium metal part covered with a special
felt-like material. The metal body has holes in defined spots through which the
electrolyte reaches the felt. In the same spots is also the anode consisting of a
fine platinum net. The pre-stamped and in the contact area pre-formed contact
spring part is guided under a defined pressure over the electrolyte soaked felt
material and gets wetted with the electrolyte. This allows the metal
electroplating in highly selective spots.
Fig. 7.1:
Brush (or “Tampon”) plating cell;
1 Strip; 2 Anode; 3 Electrolyte feed;
4 Felt covered cell
For special applications, such as for example electronic component substrates,
a dot shaped precious metal coating is required. This is achieved with two belt
masks running synchronous to the carrier material. One of these two masks has
windows which are open to the spot areas targeted for precious metal plating
coverage.
===Summary of the processes for selective electroplating===
*'''Immersion electroplating'''
Overall or selective electroplating of both sides of solid strips or pre-stamped
parts in strip form
*'''Stripe electroplating'''
Stripe electroplating on solid strips through wheel cells or using masking
techniques
*'''Selective electroplating'''
One-sided selective coating of solid, pre-stamped, or metallically belt-linked
strips by brush plating
*'''Spot electroplating'''
Electroplating in spots of solid strips with guide holes or pre-stamped parts in
strip form
===Typical examples of electroplated semi-finished materials=== (overall or selectively)
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