PCB / Enclosure Design and Etching

[Ambugaton]

Hello Everyone,

After doing a couple veroboards I am moving into etching my own PCBs and also hope to do some custom enclosure etching as well. I have searched around the web and found a few guides... and tons of options for materials and technique to choose from. I enjoy experimenting and comparing so I might as well try a couple different methods to see what works best and why. I know this has probably been done many times but it really helps me to learn by going through the process.

I am starting this from the absolute start and hope to document my progress from beginning to end... then I will modify this first post and format it more into a guide (hopefully). Only way I think I can give back to a forum like this at this stage in my experience.

Any suggestions or tips are welcome as I start weeding through good and unfortunately, the bad information as well.

[Ambugaton]

This will probably be the first attempt:

http://www.instructables.com/id/Etching-PCBs-with-PressnPeel/

Seems pretty straight forward.

[KarenColumbo]

Hey,

I went this way and landed safely in UV haven. Before I got decent results with laser printing on thin catalogue paper and ironing that on the copper side. Specialized Press'n'Peel material was deemed too expensive - wasn't available here in Austria so delivery costs surpassed the actual price. An definite No No.

You can get good results - but i wanted to explore the next base.

It's a bit hefty investment at first. A halfway decent exposure box is somewhere in the 250 - 300 Euro region (280 - 340 USD). But you get the fine bits done with it. You don't really have to go all the way and buy an etching cuvette (as they are called sometimes) - it's another 300, and, if I'm honest, it just saves time. You can get very good etching in an acid resistent bowl with Sodium persulfate solution. And it's less waste.

All in all I don't look back, but I could have bought 2.000 TL072ies for the dough

[swever]

Very inexpensive yellow transfer paper is avalable from chinese ebay sellers. Works like a charm in my experience. The only thing is that they usually send it it rolled up and packed in an envelope. Which means it needs to straightened out under something flat and heavy for a couple of weeks before it can go into printer safely.

As for etching solution, I really like citric acid + hydrogen peroxide + sodium chloride. It's cheap, fast, clean, non-toxic (until you put copper in it of course) and looks beautiful. I start with 100ml of 3% hydrogen peroxide and add 30g of citric and 5g of salt. The exact ratio is not critical. That is usually enough to etch 2-3 mid-sized boards. I did try to heat it in hot tap water bath once. Definitely gave more bubbles but I am not so sure how much faster it was. I usually just leave it under a table lamp and flip the board with a chopstick every couple of minutes. Takes some 10-20 minutes to finish.

[Fancy Lime]

There is another method for etching copper: Using copper chloride solution. The neat thing is, you can start with a simple cheep mixture of chloride, acid and peroxide, like in Alexanders method. On the first use this takes up the copper. You can the recycle it for more etches. On these subsequent etches you are effectively using cupric chloride solution. It works like this: the Cu²⁺ in the solution reacts with the metallic Cu on the PCB to form two Cu¹⁺, which then are both in solution. The Cu¹⁺ reacts with atmospheric oxygen to Cu²⁺ again, which regenerates the solution for further use. You ca re-use this indefinitely but as more copper is dissolved, you may need to add more chloride in form of sodium chloride or hydrochloric acid. Using hydrochloric acid makes the solution more acidic (well, duh!), which speeds up the etching. If faster etching is a good or bad thing is mostly a matter of preference.

Here is an article explaining the technique in some more detail:
http://www.instructables.com/id/Stop-using-Ferric-Chloride-etchant!--A-better-etc/

For enclosures you can probably use the copper chloride solution as well, but I've never tried. I use ferric chloride + hydrochloric acid for aluminium and it works quite nicely.

Andy

[Ambugaton]

Thanks for the input! I will start with the hydrochloric acid/peroxide method. Seems the easiest, cheapest, and safest way. Usually those descriptors don't always agree with each other.

I'm going to do a lot of research into what method has the ideal cheap vs. effective balance. The first question is... with all the premade PCBs available... is it worth the endeavor to make your own? Besides the obvious "feels better to do it on your own" aspect.

[swever]

Home etched boards are times cheaper than fabricated ones. No other advantages that I can think of tbh.

[brianq]

At one point, i think we should all be etching our own stuff, especially if we're in it for the long haul?


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[davent]

I gave up on any sort of toner transfer and went with photosensitive boards. For exposure i've always used regular fluorescent tubes with the boards positioned within an inch/25mm of the light.

dave

[Ambugaton]

First attempt:

Used Inkscape to do a quick design.
Used blue PnP for the transfer (not super impressed)
Used a sharper for some touch ups which didn't really work that well. I will try nail polish or maybe several layers of sharpie next time.
Etched in muriatic acid (the "greener" 90% less fumes kind) and 3% peroxide at about a 1:1 ratio.
Etched for almost an hour.
My enclosure was a taiwanese box from petal parts plus (I don't know if it's a low quality aluminium but as it etched, it broke down into chips. Don't know if that is normal)

I have two other enclosures I am going to etch and might use some magazine paper and some high gloss photo paper.

[Ambugaton]

You know what's funny...I just realized I forgot to add the labels for my knobs! At least it's just a two knob reverb. Damn.

[stringsthings]

That's a pretty good first attempt.  My first attempt at etching and enclosure was embarrassing.
And that's putting it mildly.

[bloxstompboxes]

You know what's funny...I just realized I forgot to add the labels for my knobs! At least it's just a two knob reverb. Damn.

The more frustrating part is when you forget to swap them due to the orientation of the PCB in the enclosure and you do label the box, but you mix up the labels between controls.

[duck_arse]

You know what's funny...I just realized I forgot to add the labels for my knobs! At least it's just a two knob reverb. Damn.

The more frustrating part is when you forget to swap them due to the orientation of the PCB in the enclosure and you do label the box, but you mix up the labels between controls.

who, blox, would ever, EVER think to do something like this? who?

[Ambugaton]

Well its not perfect but I'm happy with the way it came out. Just threw those knobs on there cause I had them but need to swap them out for something a little more fitting to bring it together. Its a box of hall from tagboards with the short btdr-2h. Sounds great for a subtle reverb to replace the blues jr spring (don't care for it)

[deadastronaut]

looks great for a first etch man...

[Ambugaton]

Spent the weekend trying get better tone transfers on another enclosure.....failure after failure but I found something that worked quite well:

1. Sanded the box with sanding block up to 400.
2. Used HP presentation paper 120gm/32lb for laser.
3. Printed at 600 dpi.
4. Used 2 paper towels in between iron and enclosure.
5. Used high setting (linen)
6. Clamped the iron down to the enclosure with a pretty good amount of force. (5 minutes)
7. Went over the box with the iron for another 5 minutes.
8. Coped, soaked and peeled off paper very slowly. As soon as I felt a decent amount of pressure rubbing it with my fingers I stopped and let it soak for another 5-10 minutes.

That have me a pretty good transfer and etch. Not perfect but the errors on the box were preventable I just didn't catch them. Hope it helps someone. I used a HP m277c6 if that matters.

[Ambugaton]

Question: can you fill pits in with solder and sand them smooth?

[bloxstompboxes]

Thanks for the input! I will start with the hydrochloric acid/peroxide method. Seems the easiest, cheapest, and safest way. Usually those descriptors don't always agree with each other.

I'm going to do a lot of research into what method has the ideal cheap vs. effective balance. The first question is... with all the premade PCBs available... is it worth the endeavor to make your own? Besides the obvious "feels better to do it on your own" aspect.

Make sure if you store any of the mixture or used solution that you do so outside with some sort of ventilated or loose cap. There is a thread on here somewhere where I talk about coming home to a laundry room with an exploded plastic coke bottle that was full of used solution that sprayed everywhere. I still have rusted hinges on the cabinet and some discoloration on just about everything else in that room, including the was new washer and dryer. Nobody shook the bottle or anything. There was no one home to do so. It was still reacting, I suppose, and finally the pressure was too much. It does work well though!

It is worth it to make your own. I can have a PCB ready in less than an hour or wait for someone to ship me one and have it arrive a week or two later. Which do you think happens most often?

[EBK]

Question: can you fill pits in with solder and sand them smooth?

Haven't tried this personally, but you could possibly file some aluminum off of your lid's inside flange and use the filings as an inlay powder, held in place by some thin super glue (CA glue).  Should be able to sand that smooth. 

Might not be as good as redoing the etch, but I thought I'd at least mention it.

(I'm in the midst of an experiment with filling an etch with brass inlay powder.  Hopefully, I'll have good results to share soon.  )