Silicate based product comes as a liquid concentrate. This stuff has huge advantages over sodium hydroxide, most importantly is very hard to over-develop. You can leave the board in for several times the normal developing time without noticeable degredation. This also means it's not temperature critical, no risk of stripping at warmer temperatures. Made-up solution also has a very long shelf-life, and lasts until it's used up, the concentrate lasts for at least a couple of years.
The lack of over-developing problems allows you to make the solution up really strong for very fast developing. The recommended mix is 1 part developer to 9 parts water, but you can make it stronger to develop in few seconds without the risk of over-development damage.
You can check for correct development by dipping the board in the ferric chloride very briefly, the exposed copper should turn dull pink almost instantly. If any shiny copper coloured areas remain, rinse and develop for a few more seconds. If the board was under-exposed, you can get a thin layer of resist which isn't removed by the developer. You can often remove this by gently wiping with dry paper towel, which is just abrasive enough to remove the film without damaging the pattern.
You can either use a photographic developing tray or a vertical tank for developing, a tray makes it easier to see the progress of the development. You don't need a heated tray or tank unless the solution is really cold (<15°C).
All I know is what I read on that page.Thank you
But this is not liquid. It is 25kg of sort of crystals
I assume I have to add water and it should be ready, shouldn't it?
Thanks to Robin Moorshead for the following procedure to make silicate developer solution:
Take 200cc of "water glass", add 800cc of distilled water and stir. To this add 400g of sodium hydroxide (caustic soda).
Important safety precautions: The sodium hydroxide solid must NEVER be handled, use disposable gloves. When the sodium hydroxide dissolves in water it produces a great deal of heat so it must be added a little at a time and each portion allowed to dissolve before more is added. If the solution becomes very hot leave it to cool before adding more sodium hydroxide.
The solution is VERY caustic and it is particularly damaging to the eyes, use eye protection when making and handling it.
It also ruins clothing. Water glass is also known as "sodium silicate solution" and "egg preserver", It used in fire proofing fabrics, for waterproofing walls and making "chemical gardens". Caustic soda is used for clearing drains and available from any chemist. The solution cannot be made by dissolving solid sodium silicate.
This solution will be the same strength as the concentrate, and so will need diluting - about 1 part concentrate to 4 to 8 parts water, depending on the photoresist used and temperature.
by Jake Hertz
by Aaron Carman
by Jake Hertz