What do I do when my PCB turns pink?

Hello guys,

I keep having this problem where my PCB turns pink while I'm etching. Is this normal?

Do I just have to leave it for longer or is it ruined?

Hope you can help.

Fouad.

When etching, you are removing any surplus copper which is not covered by your masking method.
Metals, left open to atmospheric conditions, develop a layer of oxidisation which can change the appearance of colour.
It is normal, don't worry about it. Continue etching until all of the pink is gone and you are left only with the copper beneath your mask.

Mickster, he said the board turns pink WHILE etching, so there is no atmospheric contact. It's probably just the copper redepositing onto the PCB material, this isn't an adherant deposit and should wipe off with even a mild solvent or soapy water wash.

What etching chemicals are you using and are you heating the tank?

All of the etchants we use work by oxidation of the copper. Assuming you are working in room air, they are also saturated with oxygen. The "pink" you are seeing is what I would call salmon pink. If you dip a clean PCB bland in ferric chloride and rinse it off, you will see that color. It is a surface phenomenon on the copper and is completely normal. I have heard that some people do that to clean the board prior to doing toner transfer.

It would be abnormal not to see it, and it's absence is one indication when using the photosensitized boards that the resist is not entirely removed from the exposed areas.

John

Perhaps I wasn't entirely clear in the previous post, or even technically correct.
What I was trying to get across, was that in normal atmospheric conditions, the copper surface takes on a different colour than that when it is being stripped away by etching. Even simple cleaning in an ultrasonic bath with only water leads to a more pinkish colouring.
Whether or not my post was technically correct is not in dispute, I simply aimed to reassure the OP that the colour of copper subject to normal atmospheric conditions will be different to that when etching and 'pink' is normal as far as I have observed on many boards.
Sorry to have bumped your gums.

Alright, I am currently using the following kit: **broken link removed**

The etchant is: FeCl etching fluid 250ml

I am constantly re-using it when trying to make my PCB's (is that okay?). How long do I have to leave the board in the etchant? do I have to keep stirring it or can I leave it for a few minutes and then stir?

Now, I left mine for a long time (15-20) and stirred occasionally...but I still got my board looking pink and when I wash it, it'll stay pink... what should it look like when I take it out of the etchant and wash it?

Thanks for all your help!

Right Mickster, which is why I got confused, because the original poster said the board turned pink while he was etching, meaning in the tank... Not when exposed to air.

I'm guessing the Salmon Pink color so far described is due to Chalcopyrite from a bath that has iron in it.

foudalor, your can not keep reusing the etchant, it will become saturated with copper, which as I think is the case it may be depositing on the PCB particulate copper simply because the solution can't hold anymore. Ferric chloride requires constant agitation most application I've seen use bubblers, like from a fish tank and are heated.

I would very much like to see pictures of what's going on. Once the solution is saturated with copper regardless of what else is going on the copper will want to get out of there and you may be getting a very thin flash layer on the raw PCB material itself, which is BAD.

I've seen this happen at a plating shop I worked at when cleaning brass parts some of the material becomes part of the solution and once the copper hits saturation, ANY object with even slight conductivity will precipitate the copper out of the solution, this subsequently screws up the following plating operations.

I would like to point out several important things that aid in my diagnosis. One, the poster is reusing old etchant (saturation) two, the PCB itself is what's changing color, and it's in the etchant at the time. I would love to know what's truly going on, but that's my best guess so far.

Sceadwian said:

Right Mickster, which is why I got confused, because the original poster said the board turned pink while he was etching, meaning in the tank... Not when exposed to air.

I'm guessing the Salmon Pink color so far described is due to Chalcopyrite from a bath that has iron in it.

Click to expand...

Well I don't know...I cant exactly see what colour the board is when inside (its a pretty murky etchant), but when I do take it out, its pink. Now that I have left it for a while it looks like the attached picture.

ah..I think Sceadwian is correct. It was working fine when I first bought the solution and thats why I was so confused... I guess if I buy a new one and try it again it may work.

Wow, yeah, that's definitely immersion plating from the copper saturation. It was probably time to dump that etchant 1/2 the number of times you used it ago.
Any board you've etched that looks like that that you still haven't removed the toner resist from is still recoverable. A quick etch will get rid of that immersion deposit. I have no idea of any kinda what effect that kind of deposit will have over short or long periods of times with boards that were etched with it.

Please dispose of the used etchant responsibly.

One quick note, if you have any desire to copper plate something for metalizing, now is the time =) Even many plastics will deposit enough copper on them in these type's of solutions to subsequently be plateable in other baths, such as a true copper plating bather or nickle etc.. You've accidentally discovered the method that is used to metalize many types of plastics for Chrome plating =)

I use my etchant 100 times or more with no real problems except it gets slower to etch and needs to be heated more.
On average i have 1/2 to 1 litre of etchant (ferric chloride) in my etch tank.

I only give boards a jiggle in the tank now and then, as constant string only mixes all the sludge on the bottom up and slows the etch time anyway.

It looks to me the board might be of a pink style glass to start with or you are over heating the etchant and staining the board.

Some ferric chloride i bought was like a thick liquid and more like a thin tar, this worked much faster when diluted with water by 25-50%. Do a small test before diluiting the full batch.

Considering the small number of boards you have made thus far i doubt the etchant is staturated and needs to be thrown out.

Pete.

Are you heating your etchant ? If you are using it cold then that could well be your problem.

I heat mine to 48 degrees C when making PCBs. I've made many of them out of the 5 litres in my tank and its still going strong (4 years later !)

Sceadwian said:

Wow, yeah, that's definitely immersion plating from the copper saturation.

Click to expand...

Can you provide a link for the chemistry involved or other examples?

As for etchants "being loaded with copper," if one switches to cupric chloride (copper(II) chloride) etching (See: **broken link removed**), the baths last forever. Just bubble air to re-oxidize the cuprous (copper(I)) ion back to cupric and keep the specific gravity adjusted by adding HCl.

The bath gives almost as fine detail as ferric chloride does. In my experience the main difference is that it is a little more sensitive at the endpoint to over etching. I have been using cupric chloride for about 4 years.

John

Not really jpanhalt sorry, I know little to nothing about chemistry from anything other than a practical standpoint from having worked a metal finishing shop for 10 years. You might possible be able to regenerate a ferric chloride etchant by electroplating the copper out of the bath, not sure what you would use for PH adjusting.

Thanks for all the help guys! I bought a new etchant and it worked fine. Although I think if I had left the other circuit long enough it would have etched the board (I left it outside and so the temperature was low..)