ADVICE ON SELF ETCH / PCB FABRICATION.

[JAYJAYBEE]

Hi

Ive recently gotten into self etching my own pcb's ( toner transfer method ), with good results.

I needed a switch for a gssl and instead of buying the set, decided to etch one from gyrafs overlay file.

The switch works fine and im very pleased, although i did modify the file a little to leave bigger gaps between tracks.

Now ive got the bug im gonna etch a few projects..first the g9 mic pre ( as ive got a few of the parts knocking around already.

i have a couple of concerns with this, first, i use FR4 1 oz copper...ive seen a few using up to 3 oz copper, for high voltages, will 1 oz copper suffice for the g9 project, or is the 3 oz stuff just overkill ( extravagance ).

Also i would like to mask the copper side of my board for this project to prevent shorts, arching...anyone got any methods for this...im thinking maybe some sort of non conductive laminate spray / paint.

cheers

[12volts]

Using 3oz copper would only be used for high current applications, not higher voltage. It's a bugger to etch too.

Frank B

[Timothytitus88]

Hi,

I have been doing some etching myself. Some G9 sets, Mnats 1176revH, amongst others.

Nothing better than cracking open a beer and watching the tracks appear. Hence the projects I tend to do are ones where the PCB artwork is available. And MASSIVE CHEERS to the guys who put their designs out there to make it possible. True DIY!

I use kinsten products: http://kinsten.com.au/ And I get excellent results. I have tried the iron on printer toner transfer stuff in the past but the results have not been as good as printing onto the polyester artwork base (much darker print than a standard overhead projector sheet) and using the pre sensitized PCB's. I made a light box lined with aluminum foil with a glass top and 2 UV compact fluorescent lamps in it. 14mins exposure is perfect. You don't need a bubble etching tank.... But if you get a styrene box with a lid (like what broccoli is delivered to the supermarket in) and a plastic tub that fits inside. Fill the put a couple of kettles full of hot water into the styrene box, then do the etching in the plastic tub that sits in the hot water. Keep the lid on the styrene box (open to give the tub a shake from time to time and check progress) and the temperature in the box stays nice and warm to help the etching.

Ferric chloride is awful - Messy and I cant see through it. I use the clear stuff. Plus there is neutralizing stuff that make it less toxic for disposal.

1oz copper is fine and there is no need to modify the artwork. Even those three tiny thin traces on the Mnats 1108 PCB turn out fine.

Plus the photosensitive resist that stays on the tracks protects them from corrosion. You don't even need to clean them off.... just solder straight through. But Altronics sell a PCB lacquer which you can solder through if you wanted to scrub the resist off and give them a spray.

Anyway... I didn't really answer the initial question but i have been planning on sharing my adventures in etching for a while. Ill try and take some photos.

Cheers!

Tim

(P.S I have no affiliation with Kinsten in case It seems like I am promoting them)

[Timothytitus88]

Oh, and this place seems to sell similar gear in the UK....

http://www.megauk.com/pcb_laminates.php

The "laserstar" artwork base seems to be the same stuff to print onto.

Cheers,

Tim

[Vetsen]

I have built a g9 and three g7s on 1 oz copper. I have been happy with the results. +1 for 3oz copper being overkill and hard to etch.

As for solder mask you could try using the toner reactive foil from pulsar.  Or you could conformal coat the PCB after it's built if that's what you are going for.

Vetsen

[JAYJAYBEE]

Hey cheers tim.

personally i apply ferric chloride with a sponge. obviously while wearing gloves. I use the pellets so i can add warm water and only use very little at a time. This works well, but im always looking to improve.

i think i may check out the photo method, ive heard its the best way.

ive always been paranoid about the close tracks on some of the projects, especially the G9, theres an area on there where theres loads of parralell tracks very close together. It took me hours to clean them up and rearrange them in illustrator.

what self etch files do you have ? maybe we can share..im always looking for neve or api...not 51x format but rack mount options, the etch files are like gold dust although i have found a 1081 but this looks too complex for me. Rack mount api 312 would be great, or a 1290.

and cheers vetsen, that conformil stuff sounds like what im looking for, a laquer that a can coat the underside with once the project is working, just for protection.

[Timothytitus88]

Here are a couple of pics of my etching the other day......

[Timothytitus88]

As you can see there is no problem with the standard tracks on the G9....

I have a lot of soldering to do!

[spase]

you have done this with toner transfer or with photo method?

[Timothytitus88]

Photo, as described in the 3rd post. Results are great. If you look on the first pic, even those microscopic traces between the 5mm spaced pads on the 1108 board are fine. And they are tiny.

I have great respect for the guys who design awesome projects (all the 51x stuff..etc) for double sided boards that need to be made by the professionals, But I just love the etching process and watching my board appear before my eyes.

Tim

[JAYJAYBEE]

As you can see there is no problem with the standard tracks on the G9....

I have a lot of soldering to do!

ok ...im converted.

theres some good tutorials on photo etching on youtoob.

its simplar than i thought.

even a normal light bulb will do, but ive just bought a uv from ebay.

firstly im gonna try using a lamination sheet as ive got loads.

do you use just a single print layer, as some print 2 and double them up.

that website you linked to in uk looks good for info, but £ 30 minimum spend plus VAT plus shipping !! Im into DIY because im a cheap skate, hahahah.

[Timothytitus88]

If you use the polyester artwork base you only need 1 layer, because the print comes out nice and dark.
If you are using clear plastic (overhead transparencies) you probably need 2 layers, which can be a bit of a pain to line up.

Here is the light box I made.... the artwork and PCB go face down onto the glass, and then a piece of wood goes on top to hold it all flat. This is all done in a darkened room, then the box gets turned on for 14 minutes.

The globes (with their 45 degree base) screw into the box from the bottom, and the whole thing is lined with foil which helps diffuse the light to get even exposure over large boards (G9)

If you are only doing 3 or 4 boards over the next year, it might be better to just buy them pre made, because it will cost more than £30 to get setup (well enough to get consistent results) and a small stock of everything you need. . You will also probably waste some of your supplies getting your process worked out (use a timer and write your process down).

a globe in a desk lamp shining down onto a board will not work consistently for large boards - you might end up wasting board and chemicals. my light box makes the process repeatable, so now I have no waste.

Cheers,

Tim

[JAYJAYBEE]

As you can see there is no problem with the standard tracks on the G9....

I have a lot of soldering to do!

and a lot of drilling.

do you tin your boards ?

or use a solder mask.

im researching up on solder masking it really makes your boards look profesional and gives them good protection

check this out

http://www.youtube.com/watch?v=4l1mXpL5lDQ&feature=related

looks awesome

[Timothytitus88]

i though you were trying to save some $$$!

that process would be very expensive.

I like the idea of tinning, but the only place i can find in oz that sells the stuff is RS and it is expensive.

So I just give the tracks a scrub with some stainless steel wool to shine them up and then spray with this........

http://www.altronics.com.au/index.asp?area=item&id=T3086.

You can solder through it.

Boards will last no problems.

And yes, time for drilling!

Cheers,

[JAYJAYBEE]

i though you were trying to save some $$$!

that process would be very expensive.

I like the idea of tinning, but the only place i can find in oz that sells the stuff is RS and it is expensive.

So I just give the tracks a scrub with some stainless steel wool to shine them up and then spray with this........

http://www.altronics.com.au/index.asp?area=item&id=T3086.

You can solder through it.

Boards will last no problems.

And yes, time for drilling!

Cheers,

not really that expensive

solder mask paint
http://www.ebay.co.uk/itm/330561466628?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

tinning
http://www.ebay.co.uk/itm/320858035296?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

its just, the ones ive seen that have been done on youtube look like professional boards you would get from a factory...feeling jealous.

anyways i think im spending too much time on pcb making and not enough on building units.haha

[Timothytitus88]

Hey,

That "tinning stuff" will not tin your boards, it is just flux, which will make the solder stick a little better to the copper (they put the word "tinning" there because when you "tin" the end of a wire, for example, you dip the wire into the "tinning flux" which makes the solder already on your iron stick to the wire better).  It is the same stuff that plumbers put on their copper pipes before they solder them together.

But you will have no trouble soldering to the fresh copper anyway. Give the board a light rub with wet and dry or stainless steel wool and the solder will flow right on.

The crystals that actually tin the bare copper are fairly expensive and I believe toxic to use and the only place I have been able to find them in oz is RS (=$$$) but I just saw that they have brought the price down and since I am in the middle of a board making spree perhaps ill give it a go.

Oh, Look here...... you are lucky. in the UK you can buy a small container of it for £16.25 (immersion tin plating). If you do it I would love to see photos of how it goes.

http://www.megauk.com/pcb_chemicals.php

But the green paint..... I would leave it. It wont make your tunes sound any better of your builds come together faster. Solder mask was really developed for mass production of boards - minimizing the chance of solder bridging tracks ("solder mask"). You do not just paint it on the board - if you do you wont be able to solder to it. It needs to be either silk screened on - (not applying to the pads that need to be soldered to) or another whole photo process needs to happen (like the initial resist developer process) so that is leaves the solder pads free. And there is no point painting it onto a finished board, over the soldered pads (I would think that that would make it very difficult to mod / repair the board in future) Just use the spray lacquer. Or if you do the tinning you don't even need to do that.

Cheers,

Tim

[zayance]

Some infos here too:

http://www.groupdiy.com/index.php?topic=42907.0

At the end you see that immersion tin, it's ok and makes a nice finish, but i would add varnish on top as well if you're going to
touch it often, it's very thin and will oxydise as well...

EDIT: as for 3oz copper, it's not hard to etch, but longer that's all, as 12Volts said, if you have high currents it's maybe better,
here is a circuit calculator just to give you an idea:
http://circuitcalculator.com/wordpress/2006/01/31/pcb-trace-width-calculator/

[Andy Peters]

i have a couple of concerns with this, first, i use FR4 1 oz copper...ive seen a few using up to 3 oz copper, for high voltages, will 1 oz copper suffice for the g9 project, or is the 3 oz stuff just overkill ( extravagance ).

The copper "weight" one needs to use isn't a function of voltage, it's a function of current in the trace.  1 oz copper suffices for anything you're going to build.

You really don't want to try soldering to a plane built with 3 oz copper.

-a

[zayance]

i have a couple of concerns with this, first, i use FR4 1 oz copper...ive seen a few using up to 3 oz copper, for high voltages, will 1 oz copper suffice for the g9 project, or is the 3 oz stuff just overkill ( extravagance ).

The copper "weight" one needs to use isn't a function of voltage, it's a function of current in the trace.  1 oz copper suffices for anything you're going to build.

You really don't want to try soldering to a plane built with 3 oz copper.

-a

oh yes of course 3oz = 105um, my brain was stuck thinking 70um copper (2oz)
Yes than forget it, etching will take an hour, maybe a little less 
2oz is still ok, and would do for most Tube based circuit i think, would take maybe 20mn to 1/2hour to etch,
depending on the solution age etc...

[Andy Peters]

i have a couple of concerns with this, first, i use FR4 1 oz copper...ive seen a few using up to 3 oz copper, for high voltages, will 1 oz copper suffice for the g9 project, or is the 3 oz stuff just overkill ( extravagance ).

The copper "weight" one needs to use isn't a function of voltage, it's a function of current in the trace.  1 oz copper suffices for anything you're going to build.

You really don't want to try soldering to a plane built with 3 oz copper.

-a

oh yes of course 3oz = 105um, my brain was stuck thinking 70um copper (2oz)
Yes than forget it, etching will take an hour, maybe a little less 
2oz is still ok, and would do for most Tube based circuit i think, would take maybe 20mn to 1/2hour to etch,
depending on the solution age etc...

I don't see why you think you need more than 1 oz copper. Again, it's the current in the traces.

-a