PCB etching problems in cold weather

[Thunderchild]

Well obviously I etch in my shed to avoid damaging my house carpet. but with subzero temperatures (naturally just at the weekends) I've found it impossible to etch, it just does not happen. now I did forget my presensitized board in the shed so will this have harmed it ? I developed the exposed board in fairly cold caustic soda, will this have been an issue ? I did have my etching chemical heated with a heater and after a few days the entire board was etched but I could not get it to etch there and then and it started to eat everything including the copper i needed to keep. the board was well exposed.

 

[Hero999]

I don't see why freezing should damage the pre-sensitised board, it's similar to photography film which I know can be stored in the fridge to prolong its life but I can't say for sure.

I think it might be the developer was too cold to develop the board..

 

[Thunderchild]

yea my thoughts too it's just getting real boring with everything going wrong

 

[jbeng]

Chemical reactions slow down when the temperature of the reactants is lowered. Developing and etching are both chemical processes.

If the board was exposed properly and all the unwanted etch resist was removed during developing, then the problem was obviously in the etch process.

I have found that heating the etchant is pretty much required for the board to etch in a timely manner. I preheat my FeCl3 etchant (in it's storage container) in a water bath to about 130F and the etch goes rather quickly.

Actual etch time depends on several factors: temperature of the etch bath, size of board and amount of copper to be removed, etchant saturation (age of the etchant), etc.

 

[Thunderchild]

well I warmed the etching chemical so it is probably a problem with developing

 

[Hero999]

What was the temperature of the exposure?

That's a chemical process to and a reduction in the temperature will probably slow it down.

 

[Thunderchild]

well i did that in the house so I suppose 15-20 degrees

 

[Sceadwian]

Heat is called the universal catalyst for a reason. ALL chemical operations should be done at room temperature or slightly elevated for speed, cold solution such as caustic can cause crystallization and it most definitely slows down reaction time. You could have bad chemicals as well, how old are they?

 

[Thunderchild]

I'm using the pellets you get from maplins they make a dark brown mixture as far as I'm aware it does not go off and I've been told that it won't be harmed by the cold providing its at the right temp when etching begins

 

[Mickster]

I'm using the pellets you get from maplins they make a dark brown mixture as far as I'm aware it does not go off and I've been told that it won't be harmed by the cold providing its at the right temp when etching begins

Aren't they the Ferric Chloride crystals? If they are, the resulting FeCl3 solution can be stored for ages. For better results when etching, a warmed solution is preferrable.

 

[jbeng]

What was the temperature of the exposure? That's a chemical process to...

Good point... I was going to mention that as well, but I just expected the exposure would be done indoors...

... the resulting FeCl3 solution can be stored for ages ...

No doubt. I have 3/4 of a large plastic jug of it which I have had it since about 1995.