Copper Plating rates in acid

[jlacy]

We have a research plating problem in which we need to plate a .004" thick layer of Copper on gold. Because the part is involved in a livetime process we must do this as rapidly as possible, preferably in 10 to 20 minutes. Is this possible and compatible with a highly adherent coating?? I understand the rule of thumb coating rate for acid copper is .001" per hour but the acid bath Caswell coating kit talks of coating .125" in several hours. This is nearly .001" per minute. Is this a pipe dream, typo or what This is a very important issue for us.

[mcaswell]

This is a research project. Unfortunately not something we would be intersted in conducting. Suggest you do some simple trials with small kits.

Post the question on the forum and see if you could get volunteers.

[eprigge]

The highest current density I've read of being used for plating acid copper (not necessarily caswell's kit) is around 200A per square foot. This would give you 3/8 of a mil per minute.

[topspinner]

This is an important question because Caswell claims 1/8 in. within a few hours and some people (myself included) may consider this important when purchasing the copper kit. Maybe the page should be updated to clarify this?

[dadkar2]

Any time you attempt to plate heavy copper you will run into problems with surface roughness. My experiments in the past have limited plating time to about an hour before roughness occurs (plating at about 0.1 amp per sq inch). At higher currents (eg current densities of 5x the 0.1 amp recommended), this roughness problem occurs much earlier, even within 20 minutes or so.

The solution is multiple plating sessions with surface sanding in between. This may not be practical in your experiment but it is common and very practical in surface finishing applications.

I've never attempted to plate up 1/8 inch. Usually a few mils is more than sufficient for surface finishing applications, which the Caswell products are designed to address. I never interpreted the 1/8 inch in a few hours as a product specification, but as an illustration that acid copper can plate at a higher rate than most other formulations, which is indeed true.

Ken

[eprigge]

I wish I could edit my previous post, it should read 3/16 of a mil per minute at 200A/sqft. Not 3/8.

Anyway this equates to around 1.1 mils per hour at 20A/sqft. which is more realistic for what you can probably get from Caswell's kit. So, being that 1/8 inch is 125 mils, that's going to be more like a few days than a few hours...