How to Electroplate onto Polymers

A. Probably the most common approach is to electroless plate the material. The plastic is etched (usually in a very concentrated acid) to give the surface some bite, then immersed in palladium chloride and/or tin chloride to 'seed' the deposition process, then electroless nickel or electroless copper plated before electrolytic copper plating; additional plating can follow.

Invariably this is done with proprietary baths. Any of the suppliers can offer you a process. When done on polypropylene or ABS the adhesion can be astounding. In fact, most exterior brightwork on automobiles, such as grills, bezels and emblems, is plastic which has been plated in this fashion.

Years ago, interior items on automobiles (such as armrest brackets) were vacuum metallized by PVD processes. The quality and durability was about equivalent to the quality of the rings found in Cracker Jax boxes and gum ball machines, which were processed similarly. Later, a more durable vacuum metallizing process called "sputtering" was employed on exterior brightwork, and on plumbing fixtures.

A problem with electroplating onto plastic is that it is very waste intensive, and the wastes are toxic; if adequate adhesion onto the polymer in question can be achieved through PVD processes and thickness is sufficient without electroless plating, it is the way to go. Certainly, in general, there has been movement away from electroplating and towards PVD processes. A literature search will produce dozens of articles on the topic. Best of luck.

A. Any nonconductive body can be sensitized (tin chloride), activated (palladium chloride) and then immersed in a concentrated electroless nickel plating bath.

A. Thanks for the kind words, Oliver. Yes, any nonconductive material could theoretically be plated once it has been coated with a conductive material. In terms of physically achieving plating onto the substrate, two issues come to mind: does the ink have sufficient current-carrying capacity for the next step in the process, and, does the ink impart sufficient chemical resistance that the part can be safely exposed to the plating chemistry.

In terms of functionality, something to remember is that proven electroless plating technologies can deliver phenomenal adhesion; sometimes it's very important for the plating to 'stick' despite severe thermal cycling and mechanical abuse like on exterior brightwork on automobiles. Also, there are many instances where the electrolessly plated coating is the final finish and there is no electroplated topcoat. A coating of electroless nickel can be robust in ways that a conductive ink probably can't be.

This is not at all meant to imply that conductive inks are not useful -- just that they cannot replace electroless plating in all applications.

A. Masking technology has been part and parcel of the printed circuit board industry for years, Richard. You probably won't mask to prevent the electroless deposition though. Rather, you would probably electrolessly plate the whole thing, mask the areas you want to keep plated, etch away the non-masked area, remove the masking material, and finish the plating. See if you can find Coombs' Printed Circuits Handbook ⇦[this on on Amazonaffil links] and you may have the info, including the alternate approaches, that you need for your project. Good luck.

A. Hi Klaus. Perhaps it possible to mold a conductive and a non-conductive plastic together and approach it from a different direction? But when we speak of traditional electroless plating, there is no "reaction" between the plastic and the plating solutions that distinguish what gets plated and what doesn't. Wherever the sensitizing and activating solutions are absorbed, those areas will plate. It may be possible to 2k mold ABS with another plastic that is fully resistant to the chromic-sulfuric acid that is used to etch the ABS so the sensitizing and activating won't "stick", but I'm not familiar with that. Sorry.

Regards,

"Electroplating and Electroless plating of Copper and Its Alloys"
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A. Hi Chaminda. Electroplating would probably be the most practical approach.

At the one extreme elementary school students can learn to do copper electroplating per our FAQ, "How Electroplating Works" in two minutes, while at the other extreme there are whole textbooks written just on copper plating .

A good compromise might be the Metal Finishing Guidebook which will explain the many different solutions for copper plating and their advantages & disadvantages, while also introducing you to the equipment considerations and the pretreatment & post-treatment steps. Good luck.

Regards,

A. Hi Yusuf. What, if anything, did you successfully plate your electroless nickel onto to prove that the EN plating solution itself works? :-)

Regards,

Q. Yes Ted, I have managed to coat another polymer sample before. If you want I can share bath composition :)

A. Hi again Yusef. I was just trying to understand the possible areas where the problem could lie. As long as you are totally sure that your electroless nickel solution will work properly if the substrate is properly activated, then I guess it's appropriate to focus on what is wrong in the etching, sensitization or activation steps.

I am no plating on plastics expert, but I understand that Polypropylene is reputedly not impossible to metallize and electroplate but very difficult. How are you etching it or surface activating it (if you are).

Regards,