what is the ratio of water and ferrite chloride !

[yusuf]

friends I am new in this electronic field ..
and i am going to make my first pcb..

I have ferrite chloride in powder form I dont have in liquid form...
and I have 6*4" inch copper clad..

but I dont know what is the ratio or how much teaspoon of ferrite chloride i should use...
Or how much water i should use for etching...

friends help please !

 

[jpanhalt]

The MSDS for ferric chloride etchant from MG Chemicals says 40% (https://www.electro-tech-online.com/custompdfs/2012/01/415-liquid.pdf), which means 40 grams of ferric chloride per 100 mL of solution. NB: That does not mean 100 mL of water and it is based on anhydrous ferric chloride. If you have the hexahydrate, the numbers need to be adjusted to account for the water contained in the solid.

40% is the common industrial concentration used for shipping solutions and in water treatment plants.

If you give more details of the form of ferric chloride you have, I can help with the calculations.

John

 

[yusuf]

I have anhydrous ferric chloride.(IN POWDER FORM) and how much time it will take for complete etching.

 

[3v0]

Etching time is variable with these factors

• Temperature
• How strong the etchant is, the more you use it the weaker it gets
• Mechanical action or lack of it, spray, bubble, slosh, or sponge
• Thickness of the copper, 1/2oz, 1oz, 2oz etc

 

[jpanhalt]

The anhydrous form releases significant heat when you dissolve it is water. Be cautious.

As for etching time, that depends on the temperature, degree of mixing/agitation, and thickness of copper on the PCB. Remember, the etching process actually involves oxidation of the copper, so more agitation and exposure to air helps. At about 55° to 60° C, 1 oz. copper takes 15' or less in my set up with gentle agitation and copper side up. Spray etching is faster. If you etch with the copper layer down, it is also faster. Some people apply the etchant with just a sponge. Citric acid can be added to reduce precipitate formation and speed etching. Look up Edinburgh etchant (https://www.electro-tech-online.com/custompdfs/2012/01/Edinburgh20Etch.pdf). I have tried it, but keep coming back to regular ferric chloride or its cousin, cupric chloride.

BTW, 40% by weight ferric chloride is almost saturated. I prepared my solution from a large jug of caked ferric chloride by adding water and letting it sit with occasional stirring for a week so so. I then diluted the saturated solution slightly.

John

 

[yusuf]

Ok.. But what will be the ratio of water and ferrite chloride..

 

[ericgibbs]

Ok.. But what will be the ratio of water and ferrite chloride..

Post #2, gives you the concentration.

Some advice, do NOT use metallic containers trays or spoons for handling the ferric chloride liquid.

 

[jpanhalt]

Ok.. But what will be the ratio of water and ferrite chloride..

That is not the usual way to make solutions, but the ratio can be calculated if you know specific gravity of the 40% solution, which is 1.415 at 20°C (https://www.handymath.com/cgi-bin/ferrictble.cgi?submit=Entry)

For 100 mL of 40% solution:
1) 100 mL will contain 40 g of ferric chloride in 141.5 g of solution (i.e., weight = vol. x specific gravity)
2) Therefore, 141.5 g of solution = 40g ferric choride + 101.5 g of water

In brief, dissolve 40 g of ferric chloride (anhydrous) in 101.5 mL of water (at 20°C).

Now, you may ask why it takes more than 100 mL of water, and why the volume of ferric chloride seems to disappear? The volume contracts significantly due to solvation and formation of hydrates that take up less volume than the combined volumes of the two, individual compounds, ferric chloride and water.

John

 

[alec_t]

Note: you can re-use the solution many times, but etching time gets longer with greater use.

....another word or two of warning.
Do not get this on clothing. (It stains badly.)
Do not empty it into a stainless steel kitchen sink. (It attacks stainless steel).