PCB Photoresist Developer

[cactustrain]

I have bought some PCB Photoresist Developer from Maplins (AP01B). It’s made by Chiltern Connections Ltd.

 

 

The product consists of very light granules that look exactly like expanded polystyrene. You mix the product with water to make a solution – first problem – it doesn’t seem to dissolve in water!

 

 

Once the solution was made up (ish), I dipped my board in, but nothing happened. How long does it take?

 

 

The instructions say not to use it near any metal – will it etch any metal away?

 

 

Has anyone had any experience of using Photoresist and in particular this product? Where am I going wrong?

 

 

[David Rickard]

The datasheet on the website says it melts at 72 degrees, which makes me think it possibly needs dissolving in hot water. However, double check the instructions - there's a risk dumping it into hot water will just produce a ton of noxious fumes, so check first. Nothing useful on the website tho. If in doubt, I'd say get in touch with them.

[Kenton]

I can't say anything about this particular product but the usual etch solution used to be ferric chloride.

I used to do this quite a bit in student days - about 40 years ago

 

You had to dissolve the crystals in hot water - too hot to stick your finger in - so 70'C sounds right

 

You require a saturated solution and you use it when tepid - not hot.

 

Keep all metal away from the solution or it will go off - definitely do not use a metal tray / spoon / stirrer or store it in a bottle with a foil cap.

 

Speed of etch depends on the thickness of the copper, the heat of the solution and the concentration of Ferric Chloride - if my memory serves me well something like 2 minutes is enough - but you should be able to watch the process. You must agitate the solution (a gentle rocking motion is enough) - it literally disappears before your eyes.

 

Too long in the solution and the etching will undermine your etch resist tracks.

 

To me it sounds as if your solution is too weak.