Barrel Plating, using conductive media / ballast / shot

A. How critical are your thickness parameters? I have experience with an automatic barrel plating line with tin. Are you plating long runs of the same size parts? My first suggestion would be to use weight as a gauge of load size. Make a few trial runs to decide the deposition rate for that size load at a certain amperage. If you run consistent size loads, you could determine an optimum setting from the ratio of the amperage and time to the thickness achieved. A good system of process control will also help to get maximum production. Although I have not seen any good guidelines for barrel plating, there may be some out there. Hope this helps.

A. I have been working with plating process setups for over ten years, for both barrel and rack. My current job entails managing a shop where we plate about 100,000 parts a week in 2x4 and 4x4 barrels. We also do copper electroforming. Here's the recipe:

1) Get the surface area of the part
2) Get an accurate count
3) Figure the total area from 1) and 2). Don't forget to add the area of ballast (shot) and danglers.
4) Determine the plating spec (what layers and how thick each is).
5) Calculate the amps for each layer based upon 3) and 4)
6) Calculate the plating time for each layer based upon 4) and your bath ratings
7) See if your calculations are correct by doing the plating.
8) Inspect the parts immediately to make sure they are what you wanted.
9) Keep good records of everything you just did.

The best way to make this easy is to let your PC do it. If you don't have a PC and the right program, buy them.

A. In plating parts of this size in the barrel for nickel, tin and electroless nickel, I used to calculate the surface area of each load using simple formulas like cylinders, spheres, cones, etc. to approximate the shape, and to weigh a small sample. 1 ampere/square foot for plating is a good first cut, if you want very good plating distribution between and within parts. Include the surface area of the plating media. Fill the barrels to one/third to one/half full

A. Hi Misri. One alternative may be vibratory barrels (rather than tumbling in a horizontal barrel, vibration makes the parts skitter around on a perforated plate).

Regards,

A. Nesting of parts can be dealt with many ways, but there are limits. I don't think the "Vibrobot" is a viable option as its design is not a nesting issue. I assume you are barrel plating in some type of horizontal barrel. Breakers are the most common solution, either full width, or blocks installed. Are you using round barrels? Nesting is sometimes more of a problem with these than hex barrels. A lesser load with a large internal breaker can "flip" the entire load. RPMs can also help sometimes, depending on the part / load size / etc.

Sometimes just redistributing the load can make a huge difference [i.e., different size equipment]

Contact your equipment vendor / distributor with sample parts -- they should be able to provide a viable solution.

A. I'm not sure that I understand your question, Saar, but one occasion to include metallic balls or other conductive media in the mix is when the parts you are trying to plate don't have enough plateable area on them to reliably conduct electricity from piece to piece. As a parallel: In the children's game of "tag" there is usually a "home base" where the players are safe, and sometimes the kids join hands to make a chain extending from home base, claiming to be safe via "electricity" (one child gripping hands with another, gripping hands with another. Barrel plating of fully conductive parts works the same way: one part touches another which touches another which touches another which touches the danglers or cathodic contacts.

But when only part of the components are conductive, for example, if you are trying to barrel plate the ends of surface mount components, and only the ends have been made conductive with metallic paint, you may find that filling the plating barrel with such components will not allow a conductive path from piece to piece to piece because the conductive area of one part is only touching the non-conductive area of another. But if you mix in an appropriate quantity of conductive balls, you may have a plateable mix.

A. I have found vendors who are capable of electroless barrel plating on plastic. I'm sure they would be willing to talk with you.

A. Haslina,
I'm not sure what you mean when you mention that the parts are "floating on a dummy". You may have to "load up" on the barrel media. There is lightweight conductive media available for Barrel Plating that will not bend or scratch the packages. This type of media comes in all weights, shapes and sizes and maintains good conductivity within the barrel. It takes a little experimentation to get the correct mix of parts and media to get the desired plating thickness and to be sure there is no damage to the packages. There is another alternative to conventional barrel plating which is Vibratory Barrel Plating. This technique is often used when delicate parts are not suitable for Barrel Plating. Instead of a tumbling motion, the parts are moved by vibration around the surface of the barrel. Your parts and media may be too lightweight for this process however. Hope this helps!

A. Use stainless steel balls that have been run in a nickel chloride strike, then after use, put them in a stainless basket and use for anodes in your silver plating tank, the nickel will not hurt the silver. Be sure to silver strike first to minimize the co-deposition of the copper (which eventually is going to find its way into the silver solution.)

A. Uh, what, Robert? You're describing something quite interesting to me, but either you or I misread Al's question.

My take was that he is barrel plating some copper components but feels that the parts can't be successfully barrel plated without conductive media/ballast/shot added to the barrel. You seem to be talking about a way to increase the anode area without a big investment in more silver?

Regards,

A. Ted, what I am trying to say. Use the stainless steel balls in the electroplating barrel, then after he is through with the balls or they are built up too much (chipping and flaking) then put them in stainless basket back in the plating solution and recover the silver.

A. Hello Michael,
If you go to www.pfonline.com > suppliers, click on Mass Finishing Media, you will find a list of companies who supply barrel plating media.

A. Hi Wangsa. Your question is a bit vague, but I think you are saying that stainless steel balls you are using as conductive media in barrel tin plating of semiconductor components are plating up and sticking together? I think you must reduce their quantity, or increase the speed of rotation so they are knocked apart before the plating builds up that much, or change their shape or size or finish.

Regards,

A. Hi again. All I can offer is wild guesses because you are not offering a co-ordinated and detailed description of what your whole situation actually is, but have you switched from bright acid tin (stannous sulfate), alkaline stannate, or MSA bath to one of the other two perhaps?

If you have no idea you'll probably have to retain a plating consultant. Good luck.

Regards,