Problem with etching PCB

[mohsen 2012]

Hello , How do I know that the ferric chloride has expired?
I plug my pcb at the tank who contains a 1 litre of ferric chloride but the copper layer does not remove at all after 2 hours !!!!
look at the photo :





I work fine with my etch tank from 5 months ago , contain 1 litre of solution .

please help me and thanks

 

[ysba]

Hi,

- Do you put the PCB in the tank and keep it still?

I get best results if I move the PCB through the fluid. Looks like it forms a small layer of corroded copper that stays over the board. When you move it through the fluid, this layer goes away allowing to a new layer to be corroded.

- What is your room temperature?

The ferric chloride works better if it is a little warm. Here where I live I got like 10°C of room temperature. What I do is use a small amout of corrodent in a small plastic bowl. So I put this small pot in a bigger one filled with boiling water. The water heatens up the corrodent and the proccess goes a lot faster.

Yesterday I made a PCB like yours in size, and it took only 10 minutes.

Hope this helps.

 

[c_mitra]

Ferric chloride has no expiry date- it lives for ever. However, the capacity goes down with use and it works best when warm and stirred.

You also need to add a little HCl, till the cloudiness disappears.

You will get best results if you spray the ferric chloride solution on the board- you will also be able to see the etching process. If you have been using used ferric chloride solution, it is time to make a fresh one.

 

[KamW]

I am not sure from your photo if there is sediment in your tank.
Similar etch problems could be when your solutions cease to be acidic. If you have sediment there is insouble Fe(OH)3.
The result solution stop etch.
to solve problem add HCl and H2O2

 

[mohsen 2012]

thanks for your replies , how much the amount of HCL to be added

 

[c_mitra]

You keep on adding till the solution becomes clear; there should not be any turbidity. Depending on the health of the current solution, it may need a little or a lot.