Electroless Copper Plating,Electroless Copper Plating,Electroless Copper Plating,Electroless Copper Plating
ELECTROLESS, OR AUTOCATALYTIC, METAL PLATING is a nonelectrolytic method of deposition from solution.
The minimum necessary components of an electroless plating solution are a metal salt and an appropriate reducing agent.
An additional requirement is that the solution, although thermodynamically unstable, is stable in practice until a suitable
catalyzed surface is introduced. Plating is then initiated on the catalyzed surface, and the plating reaction is sustained by
the catalytic nature of the plated metal surface itself. This definition of electroless plating thus eliminates both those
solutions that spontaneously plate on all surfaces (homogeneous chemical reduction), such as silver mirroring solutions,
and immersion plating solutions, which deposit by displacement a very thin film of a relatively noble metal onto the
surface of a sacrificial, less noble metal.
The history of electroless plating began with the serendipitous discovery, by Brenner and Riddell, of electroless nickelphosphorus,
during a series of nickel electroplating experiments in 1946 (Ref 1). Electroless copper chemistry was first
reported in the following year by Narcus (Ref 2). The first commercial applicability of electroless copper was reported in
the mid-1950s with the development of plating solutions for plated-through-hole (PTH) printed wiring boards. Electroless
copper solutions resembling today's technology were first reported in 1957 by Cahill (Ref 3) with the report of alkaline
copper tartrate baths using formaldehyde as reducing agent. Copper baths of the 1950s were difficult to control and very
susceptible to spontaneous decomposition. Over the years, continual advances in control and capabilities have taken place
and continue to be recorded in a variety of reviews (Ref 4, 5). At present, not only are formulations extremely stable and
predictable in behavior over long periods and under a wide variety of operating conditions, but they also provide copper
deposits having excellent physical and metallurgical properties comparable with those of electrolytic deposits.
Electroless copper plates much more slowly, and is a much more expensive process, than electrolytic copper plating.
However, electroless copper plating offers advantages over electrolytic plating that make it the method of choice in
certain cases. Electroless copper plates uniformly over all surfaces, regardless of size and shape, demonstrating 100%
throwing power; and it may be plated onto nonconductors, or onto conductive surfaces that do not share electrical
continuity. The ability to plate large racks of substrates simultaneously is also an advantage in certain instances. These
advantages have contributed to the choice of electroless copper in the applications to be discussed herein.

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