Quick Etching Idea

[Cotowar]

Okay, so I was reading about how to etch PCB's, and most of the tutorials said to drop your board into a tank full of etching solution. Then they said to mix it around or rock the tank or what have you to keep it reacting.

I then found a method where they suggest using a 3-M scotchbrite pad and rubbing the etching solution on the board.

Here is my improvement to that idea. Go to your local dollar general (not family dollar) and head to the cleaning supply section. They have in there a device made of plastic, with the same exact scour pad on the end. The neat thing is, the device handle is made to hold dish soap, but you could possibly load it with etching solution. It has a small hole at the back side of the scouring pad, so as you push, the solution comes out. It keeps your hands out of the chemicals, and lets you put a little more elbow into the motion. it also has handy little measuring lines, so you can fill it precisely. Oh, and it costs like $2 last I checked (last Thursday).

I think it would be worth looking in to, but I don't have any boards to etch, so someone try it and let me know how it goes.

Hope that speeds things up at least a little bit for you guys. I'll be on the look out for more tricks and improvements as I lurk around the forums more.

 

[CCD]

Good idea! keeps hands clean!
probably i'll try it out for my next two layer PCB.

Thanks!

------------
Design with Microcontrollers

 

[philba]

mechanical scrubbing isn't such a good idea as you might loosen or scrape off your resist. I use a vertical tank with an aquarium bubbler. works great.

 

[Rolf]

mechanical scrubbing isn't such a good idea as you might loosen or scrape off your resist. I use a vertical tank with an aquarium bubbler. works great.

I agree, but a simple solution for a simple tray etching speedup is to use a turkey baster. By sucking up and discharging the etching solution on the PCB, the whole process is greatly shortened.

 

[3v0]

The PulsarProFx website has a method where they wipe the copper off the board with an etchant soaked sponge. A SS 1 oz board takes about 1 maybe 2 minutes.

Prior to etching the toner is coated with their foil to prevent the tone from rubbing off during etching. I have used it and it works. If you do it with ferric chloride I strongly recommend a fume hood. I have not tried it with other etchants.

3v0

 

[jpanhalt]

I put the board on a plastic trivet in the etchant and run a magnetic stir bar under it to get a nice swirling motion of the fluid. It is very neat with no splashing.

John

 

[philba]

The problem with horizontal etching is that the waste concentrates on the top side and slows progress. There are all manner of ways to solve this. One guy places his tray on a subwoofer and plays rock and roll. I'm not sure that's really a good way to go. A gentle rocking seems to work well. I dislike anything that causes me to have to remove etchant but if you are careful most methods can work.

By the way, I use Ammonium Persulfate. It costs more but has a number of advantages. It's clear so you can see progress. In addition, if you spill it the stains are pretty minimal. FeCl is way nasty that way. I love it in my vertical etch tank as I can shine a light on the other side and see very clearly when my PCB is done with out having to lift it out. Also, copper sulfate (or what ever it is) is less soluble than AP and precipitates out when cold. So you can stretch your etchant a bit farther.

 

[Boncuk]

The fastest etching I've ever seen was at the Kiel (northern Germany) university. They used a stainless steel tank and a stirring device (like a propeller) mounted to an AC driven 250W motor. The PCBs were lowered into the tank by a carrier frame and the tank lid closed. Then the motor started working with the etchant (iron tricloride)

After 30 seconds the PCB was finished.

I guess this method doesn't even require an etchant prove motor bearing system if the shaft is long enough.

Boncuk

 

[Pommie]

If your careful you can float your boards face down on the etchant. I normally put a loop of masking tape on the back as a handle.

Mike.

 

[rahulan999]

PCB etching ok.
How to apply a silver coating and finally, a green layer finishing for the board? Is it possible for home based projects? Can u tell me abt the tools if required, and materials needed for that?

 

[Boncuk]

PCB etching ok.
How to apply a silver coating and finally, a green layer finishing for the board? Is it possible for home based projects? Can u tell me abt the tools if required, and materials needed for that?

There is chemical tin and silver coating stuff on the market. For a green finish I suppose you mean a solder stop mask. This requires a printing machine.

Boncuk

 

[geko]

PCB etching ok.
How to apply a silver coating and finally, a green layer finishing for the board? Is it possible for home based projects? Can u tell me abt the tools if required, and materials needed for that?

I do a component overlay by printing the mirrored overlay onto normal paper with a Laser printer, then ironing it onto the PCB.

http://picprojects.org.uk/projects/f1lights/c3.jpg
http://picprojects.org.uk/projects/Traffic Lights/images/p9231251.jpg

 

[3v0]

**broken link removed**

 

[ericgibbs]

PCB etching ok.
How to apply a silver coating and finally, a green layer finishing for the board? Is it possible for home based projects? Can u tell me abt the tools if required, and materials needed for that?

hi,
By 'silver coating' do you mean a 'tin coating'.?

If Yes, you can get tinning crystals, but the type I used were very 'unfriendly' and hazardous.

If you clean your bare etched copper pcb and you require a 'varnish' finish, you can buy aerosols of clear PCB lacquer [cheaper] or the more heavy duty 'red none conformal' [expensive].
Both types are solder thru if you need to repair the pcb later on.

One of the problems with aerosols is if you have sockets or connectors on the pcb, you MUST mask them off with tape, before spraying.

You can get the varnish in liquid form in tins, this is the way I prefer, use the small paint brush to apply the varnish.

Use a hair drier on low setting to dry the varnish.

 

[rahulan999]

hi,

If you clean your bare etched copper pcb and you require a 'varnish' finish,

exactly!
Your varnish idea I liked in place of green protective layer. How abt normal wood varnish, is that solderable thru?

aerosols of clear PCB lacquer

I didn't understand this. Can u name that chemical or whatever type is.

 

[ericgibbs]

exactly!
Your varnish idea I liked in place of green protective layer. How abt normal wood varnish, is that solderable thru?

I didn't understand this. Can u name that chemical or whatever type is.

Hi,
This link shows some options.

Browse for Products | Farnell UK

 

[3v0]

I spray my PCBs with a thin coat of clear acrylic varnish after etching. This seals the copper, the board stays bright indefinitely.

The acrylic vaporizes as soon as you touch it with a soldering iron so you can solder through. No need for tin or silver plating.

When I finish soldering the board I give it another coat if I want further protection. Use transparent green here if you want to fake a professional board.

Read the info at the link in my last post. Even if you do not use his products or all his methods there is a lot of good info on the pulsarProFx site.

3v0

If Yes, you can get tinning crystals, but the type I used were very 'unfriendly' and hazardous.
.

I agree. I used it once or twice and do not care for it at all.

I had some hope for the coolamp silver-plate product but I read where it yellows with age. Why bother.

 

[rahulan999]

Yea, I went through that link. Thanks a lot for the info.
My eyes are on the green professional looking eventhough It requires spray tools for better finish.
Varnish coating is a fresh info for me and it is more applicable I think.

 

[3v0]

Yea, I went through that link. Thanks a lot for the info.
My eyes are on the green professional looking eventhough It requires spray tools for better finish.
Varnish coating is a fresh info for me and it is more applicable I think.

The semi transparent green acrylic comes in a spray can. It provides a nice smooth finish. I guess you would say it is self leveling.

There are several different coatings that are called varnishes because the are used in place of the original oil based varnish. I could be wrong but as far as I can tell the word varnish is synonymous with the word coating these days.

What I use is acrylic spray. Another heavier version is sold as a non weatherproof conformal coating. For pre solder coating I use the lighter clear spray acrylic.

3v0

 

[jpanhalt]

Good morning 3V0.

When you originally wrote "varnish", I assumed you meant lacquer. As a woodworker and chemist, I would make the distinction that a varnish has a drying agent ("drying oil") and resin; whereas, lacquer sets up just by solvent evaporation. Thus, varnishes are more like enamels than lacquers.

Fresh coats of lacquer on lacquer dissolve the underlying coats to some extent. Fresh coats of varnish on varnish do not.

Both types of finishes could be made solderable in theory. However, I have usually heard the term acrylic applied to lacquer. Polyurethane is usually applied to varnishes or enamels.

To give more information than you really want...you can buy additives that convert most enamels to "modified" polyurethanes. They might actually work with some varnishes too, but would need to be tested. Calling a coating "polyurethane" seems to give a marketing advantage.

John