# PCB Etching



## spynic (Jul 13, 2007)

hey can some1 pls give a detailed process of PCB etching.
i hav no clue on how its done... but it makes circuits less complicated..


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## iMav (Jul 13, 2007)

well as far as i remmber is u outline ur connections with oil paint on the board and then leave the rest as it is and submerge the board in a solution after some time the un painted part is no more conductive and u then remove the oil paint and then u have ur ckt etched ...

 il have to dig up my pc for a write up i had ....


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## pimpom (Jul 14, 2007)

A detailed tutorial would be quite long. Here's a condensed version -

First you need a blank copper-clad board. This has a thin sheet of copper bonded onto a plastic board. The plastic is either phenolic or epoxy strengthened with glass fibre.

Unwanted parts of the copper are dissolved (etched) with a chemical (called the "etchant" - usually Ferric Chloride) while the tracks needed for interconnecting parts are protected by a mask.

The tracks are drawn or printed on the bare copper. For professional or mass-production work, the track design is transfered with either silk screen printing or with a photo-sensitive process. For quick prototyping, I use a waterproof marker pen.

The idea is that the masking medium should not be affected by water or the etchant chemical.

After the tracks are drawn or printed, the board is immersed in the etchant solution. The etchant eats away unprotected parts of the copper, while the masked areas remain intact.

That's the basic idea. There are tricks and pitfalls. If you need more details, just ask. Or you can search on the net. There must be tons of info about making PCBs on the internet.

It just so happens that I'm experimenting with a fairly simple process that can be done at home to produce goog-looking PCBs. The resulting finish may not be quite as refined as, say, a computer card, but it will certainly be better than a crude hand-drawn design.


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## spynic (Jul 15, 2007)

how much does d whole kit cost (approx)?
n how long does it take to make it (excluding the time for designin circuit)??


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## janitha (Jul 15, 2007)

spynic said:
			
		

> how much does d whole kit cost (approx)?
> n how long does it take to make it (excluding the time for designin circuit)??



As far as I remember, the actual etching process takes less than 30 minutes, depending on the concentration of the Ferric chloride and temperature. It is the drawing/masking which takes time.
(used to do it several years back)

It will not cost much. Copper clad sheets can be obtained from any electronic component shop and ferric chloride will be available from any lab supply shop.


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## aditya.shevade (Jul 15, 2007)

pimpom said:
			
		

> For quick prototyping, I use a waterproof marker pen.



Hi there, can you tell me which make do you use?

I have tried Faber Castle's OHP+ marker, but it partially dissolves. The best so far has been oil-paint.

Aditya


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## pimpom (Jul 16, 2007)

spynic said:
			
		

> how much does d whole kit cost (approx)?


I live in a remote place where things are not easy to come by, so when I visit a metro, I usually buy enough copper-clad board and Ferric Chloride to last me several years. IOW, I buy them once every 5-10 years.

It's been quite some time since I last bought them, so I'm not sure how much I paid. As an indicative figure, I'd say something like Rs.50-60 for a one-foot-square phenolic board. Glass-epoxy will be around 100-150/-.

I'm even less sure about Ferric Chloride because my current stock was brought by a friend for whom I'd solved some technical problems, and he wouldn't tell me the price. As a rough guess, I'd say around a hundred bucks for a 500-gram pack. 



> n how long does it take to make it (excluding the time for designin circuit)??


Generally 5-15 minutes. It depends on certain factors -

1. Temperature. Cold weather slows it down.
2. Strength of the solution. A weak or partly used solution works more slowly
3. Agitation. If you simply immerse the board in the solution, it may take more than 30 minutes. Rocking it side to side will dramatically reduce the etching time.

I prepare the solution as 350gm of FeCl3 to one litre of water. It's also available as a solution. I think the standard strength of a ready-made solution is 22%, though I'm not sure.

Caution :
1. FeCl3 can stain skin and clothes.
2. It dissolves metal, so use only glass or plastic containers.
3. When solid FeCl3 is first dissolved in water, it can get very hot - enough to melt and/or deform some plastics. So using a thin plastic container such as an empty Coke bottle is not a good idea. I use a large-neck glass bottle (e.g. an empty Horlicks or Viva bottle). I first place the bottle in a plastic bowl, just in case the glass breaks. After the solution has cooled down, it can be stored in any non-metallic container.



			
				aditya.shevade said:
			
		

> Hi there, can you tell me which make do you use?
> 
> I have tried Faber Castle's OHP+ marker, but it partially dissolves.


I'm not very particular about the brand of pen. I use anything I find in the market, including Faber-Castle. At the moment, I'm using Luxor. I use one with a fine tip (those that look like ordinary pens) for drawing narrow tracks, and a thicker one for filling in larger areas.

The important thing is to select a pen that has a good flow of ink and apply it as thickly as possible. The solvent of marker pens evaporate easily and even a newly bought pen may have partially dried out while in stock.

Cap the pen immediately any time you stop drawing for more than a couple of seconds. This is inconvenient, but it's the only way to ensure a good flow when you draw the design.

When you buy a marker pen, test it in the shop by writing on glass or polythene, not paper.

The solvent can be replenished if it has partially dried up (instead of the ink being used up). Methylated spirit can be used, but automotive paint thinner is better. I use Duco or Garlac thinner. Open the marker,  take out the fibre rod holding the ink, and apply several drops of thinner to it. I soak a small ball of cotton-wool with thinner and squeeze it on to one end of the fibre tube. It can get messy if you're not careful.

A small bottle of marker refill ink is also easily available.



> The best so far has been oil-paint.


Oil paint is OK. In fact, almost any non-metallic, non-water-based medium will protect the copper against FeCl3, provided it sticks firmly. The trick is to find a way to draw the intricate patterns on the copper.


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## deepakg (Jul 16, 2007)

Use this techniq to do professional quality PCB design...

In this process you need not to use oil paints or marker pen..

Design your circuit on computer using Adobe Photoshop..
you can even do it in MS-Word..using LineArt.

with a good quality Laser Printer take a printout of final design on transparent OHP paper..

Now place this OHP paper over blank PCB.. and just roll over your hot iron to transfer design to PCB..

Now you have professional quality designed PCB..

Now do rest of the process as written above..

I use this techniq from last 10 years..


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## pimpom (Jul 16, 2007)

The idea of using printer toner as the etch resist has been around for over 20 years. Before laser printers became widely available, Xerox copiers were used. There are numerous websites describing the process.

The toner is plastic based and works well as an etch resist. The problem is in transferring the printed design efficiently. It's two-fold :

First, judging the right amount of heat and pressure; and spreading them evenly over the whole surface. Too little heat and/or pressure, and the toner does not stick properly. Too much heat can warp the board or even damage the bonding between the copper and the plastic backing. Uneven heat causes uneven transfer. Too much pressure can squash the pattern.

Secondly, the paper. After ironing, the toner sticks to the copper *and* the paper. Ordinary paper is porous, absorbs too much toner and causes uneven patterns on the copper. Glossy paper allows the toner to stick more evenly on to the copper, but removing the paper can be a big pain.

I'm experimenting with teflon-coated stationery and the results are promising. I'm trying to find the best type and brand.


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## praka123 (Jul 16, 2007)

hmm..now also ppl tries hobby circuits?its a pain with ferric chloride and copper clads,ya did 12 yrs before.subscribed efy,elektor etc for circuits.better a bread board,right?


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## spynic (Jul 16, 2007)

deepakg said:
			
		

> Now place this OHP paper over blank PCB.. and just roll over your hot iron to transfer design to PCB..


wudnt the OHP stick to the iron?



			
				praka123 said:
			
		

> hmm..now also ppl tries hobby circuits?its a pain with ferric chloride and copper clads,ya did 12 yrs before.subscribed efy,elektor etc for circuits.better a bread board,right?


nah.. not hobby... using the circuit for long term practical purpose, thts y i wanna make a pcb


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## deepakg (Jul 17, 2007)

No.. it will not..
If you maintain proper heat of iron..you will get best result..
First try it on a blank scrap board..then go for final design..
It's all about trying and trying.. Remember you are designing PCB at home.. not at the Factory..


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## shaunak (Jul 17, 2007)

I suggest you use a bread board to test your circuit first. 

Tried and tested technique.

1. Toner-transfer/marker
Print you circuit board using a *laser printer on *a transparency. Get a really hot iron [best go to the laundry fellow] and iron with the printed side touching your copper. The toner will become undone from the plastic and stick to the copper real good.
Note if your arent using a printed board then draw your circuit with a marker instead in this step.
I personaly prefer using a marker to printing the board coz a marker is easier to remove later.
I use a "F" point faber-castel marker.

2. Drill your holes
This may come as a surprise but drilling your holes first yeild better results simply because a> if you mess up you can correct yourself with a marker b> copper wont etch from the inner rim.

3. Touch up
Touch up any damaged connections [due to drill skidding] with a marker.

4. Etch
Take two plastic trays [the ones that photographers use]
Fill both about half way with lukewarm water.
Set one aside for the moment.
In the other one drop about 70gms Iron(iii)Chloride [add  1~2 drops conc HCL for faster etching].
Drop your board in, face up , and keep moving it with a plastic spoon [or with your hands if you have rubber gloves on]
in 20mins the board should be up and ready.
Drop the board in the other [clean water] tray.

5. Cleanup
If you used a marker to draw the circuit then simply pour some medical alcohol/ colonge/ or spray some deo directly on your board, wash and wipe dry. [Easy!]
If you used the toner-transfer method then get ready for a long session of scrubbing. use a scrubbing pad and soap to scrub away the toner. I suggest you scrub out ony those areas where you intend to solder on. The rest can stay as a silk screen.

Additional: you can use ltspice to simulate the circuit and then eagle pcb to create your board. Both are free tools


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## spynic (Jul 17, 2007)

shaunak said:
			
		

> I suggest you use a bread board to test your circuit first.


done wid bread board.. n on circuit board,, all work fine..
this is how my circuit looks!
*img413.imageshack.us/img413/3082/dsc01098smallmc6.jpg

thts y im goin in for a pcb.


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## zyberboy (Jul 17, 2007)

use protel or orcad to design the circuit,so u can easily adjust track width and layout.


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## shaunak (Jul 17, 2007)

Forgot to mention:

 Some OHp somtimes dissolves away.

Get faber-casle/luxor dye permanent markers only.
Fabers one is called "multimark"

A thumb-rule is that on ohp paper it should apear fully opaque.


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## sashijoseph (Jul 17, 2007)

I'm too lazy for the permanent marker method(esp for big layouts) so I offload  the transfer process to the local screen printing fella(those shaadi and visiting card guys),who charges Rs30 for any no. of pieces from 1 to 20.Nice and neat.You only need to etch after that and no worries about tracks dissolving or etchant getting underneath the drawn lines etc.


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## pimpom (Jul 17, 2007)

Yeah, that's one way to get the job done, and I sometimes use it myself. But the OP wanted to know how it's done. And for many people, doing it yourself is more important than simply getting the finished product.


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## mika00969 (Mar 5, 2009)

Here is a excellent and cheep pcb manufacturing service suitable for small DIY projects. Realy good results, and really cheep.
*sites.google.com/site/procad69/


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## Deleted member 26636 (Mar 5, 2009)

why are you bumping a two year old thread?? check the date before posting.


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