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Using Arduino => General Electronics => Topic started by: aster94 on May 16, 2017, 03:26 am

Title: Homemade pcb with Photoresist method
Post by: aster94 on May 16, 2017, 03:26 am
Hello,

Since in this forum we are almost all hobbyist i thought to write  here

I get bored of paper transfer method and time lost so i wanted to switch to the photoresist.
About the spray a lot of people use the positiv-20, it s 15 euros in europe, someone knows any alternative?
And for the transparent paper which one do you use? I don t want to buy the cheapest and then trough it

Any link or suggestion would be very appreciared  :)
Title: Re: Homemade pcb with Photoresist method
Post by: larryd on May 16, 2017, 03:34 am
Search the forums here for previous discussions.
Example:
http://forum.arduino.cc/index.php?topic=177629.msg1317368#msg1317368  (http://forum.arduino.cc/index.php?topic=177629.msg1317368#msg1317368)

I follow this:
(http://forum.arduino.cc/index.php?action=dlattach;topic=357920.0;attach=143012)


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Title: Re: Homemade pcb with Photoresist method
Post by: CrossRoads on May 16, 2017, 06:02 am
Salt, vinegar, hyrdogen peroxide seems viable also
https://www.google.com/?gws_rd=ssl#q=hydrogen+peroxide+vinegar+salt+pcb (https://www.google.com/?gws_rd=ssl#q=hydrogen+peroxide+vinegar+salt+pcb)

I send out for all my boards,  I won't give up plated thru holes, stenciling, solder mask.  And not having to not drill holes.
Title: Re: Homemade pcb with Photoresist method
Post by: Wawa on May 16, 2017, 06:47 am
Once you have used a board house, you never go back to making your own.
Leo..
Title: Re: Homemade pcb with Photoresist method
Post by: aster94 on May 16, 2017, 09:50 am
Really i asked a suggestion about which photoresist spray and  transparent paper I should use... I never mentioned the etchant solution or how to do it

Wawa i agree, but what do you do when you need only 1 board?
Title: Re: Homemade pcb with Photoresist method
Post by: Wawa on May 16, 2017, 09:59 am
Wawa i agree, but what do you do when you need only 1 board?
I use my $3,000 CNC machine for that.
Leo..
Title: Re: Homemade pcb with Photoresist method
Post by: GypsumFantastic on May 16, 2017, 10:09 am
I use tracing paper in a laser printer. I think it takes the toner a bit better than the acetate sheets some people use. I've had some really crisp results.

I buy pre-sensitised boards though, so I'm afraid I can't offer any advice with the spray stuff.

I like doing it myself. I enjoy the process.
Title: Re: Homemade pcb with Photoresist method
Post by: aster94 on May 16, 2017, 10:31 am
I use my $3,000 CNC machine for that.
Leo..
You like to play the easy games ahahah one day i will have a cnc but this is not the day

I use tracing paper in a laser printer. I think it takes the toner a bit better than the acetate sheets some people use. I've had some really crisp results.

I buy pre-sensitised boards though, so I'm afraid I can't offer any advice with the spray stuff.

I like doing it myself. I enjoy the process.
Could you give me a link or only the brand of this tracing paper?
Title: Re: Homemade pcb with Photoresist method
Post by: MarkDerbyshire on May 16, 2017, 11:05 am
To make the mask I use JetStar for Inkjets.  


Inkjet/laser pcb film (http://uk.rs-online.com/web/c/pcb-prototyping/pcb-etching-developing/inkjet-artwork-film/)

They also do one for laser printers.  It is easier and better results to by the pre sensitized boards and I expose in a UV box from ebay.
Title: Re: Homemade pcb with Photoresist method
Post by: ElCaron on May 16, 2017, 01:04 pm
Wawa i agree, but what do you do when you need only 1 board?
Throw away the other 9 boards? Seeed just reduced their price to 5$ for 10 10x10cm^2 boards.
The only reason not to do that is the three weeks shipping time.
Title: Re: Homemade pcb with Photoresist method
Post by: Wawa on May 16, 2017, 01:32 pm
Some board houses have 5 boards for the same price as 10.
But this could reduce freight cost (which is the biggest killer).
Shop around.
Leo..
Title: Re: Homemade pcb with Photoresist method
Post by: aster94 on May 16, 2017, 03:08 pm
Throw away the other 9 boards? Seeed just reduced their price to 5$ for 10 10x10cm^2 boards.
The only reason not to do that is the three weeks shipping time.
yep plus the 13€ for shipping, maybe in your country it is cheaper
Title: Re: Homemade pcb with Photoresist method
Post by: GypsumFantastic on May 16, 2017, 03:54 pm
Could you give me a link or only the brand of this tracing paper?
It's Gateway brand but I don't think there's anything special about it. It was the first one I found in the stationery catalogue we use at work.

It's 90gsm which is just a bit thicker than standard copy/laser paper - I think that makes it a bit easier to handle.

This is the stuff. (http://www.viking-direct.co.uk/a/pb/Tracing-Paper-90gsm-297-cm-x-21-cm-x-210-mm-Clear-50/id=RG1059/)

I made my own exposure box using a UV CFL tube from a pond steriliser. It takes a long time to expose (about 15 minutes) but as I said, the results have been good.
Title: Re: Homemade pcb with Photoresist method
Post by: allanhurst on May 16, 2017, 04:57 pm
Quote
I use my $3,000 CNC machine for that.
Leo..
Well, it's ok for some, but I bet you can' t do 4 thou track and spacing and 10 thou vias....
And how do you register top and bottom layers?

And as for mutilayers - that's tricky.

I've etched my own in the past, but professionally made boards are so good and cheap I woudn't bother these days.

And maybe the slow boat is partially a good thing - it makes you check thoroughly before ordering..

Allan
Title: Re: Homemade pcb with Photoresist method
Post by: Boardburner2 on May 16, 2017, 05:07 pm
I would second the use of pre sensitised boards.

The spray on stuff i found to be finnicy, and have not used it for 30 years or so.
Title: Re: Homemade pcb with Photoresist method
Post by: ElCaron on May 16, 2017, 05:22 pm
yep plus the 13€ for shipping, maybe in your country it is cheaper
At seeed, I just paid 11US$ and 13US$ for shipping to Germany, for 20 boards each. So one board for 10US$=9€, if you throw away 9 from each design. Still worth it for me.
Title: Re: Homemade pcb with Photoresist method
Post by: tinman13kup on May 16, 2017, 11:18 pm
I actually found the solution for plated through holes at a house remodel I did. The previous owners left behind some old electronics parts, I'm guessing from the 60's/70's. In there I found a vial of what looked like rivets. On closer inspection, there were 2 sizes, in which one fit perfectly into the other.. The hole through the center just happens to be the right size for through hole parts.  I would really like to locate more of these, as I only have about 30 left.

As for the boards, I just use the pre-sensitized boards, standard transparency sheets, and an Ott-light to expose them. 8 minutes does the trick, and I'm using downwards of .012 traces. I find temperature is key for the whole thing.
Title: Re: Homemade pcb with Photoresist method
Post by: Wawa on May 16, 2017, 11:19 pm
Well, it's ok for some, but I bet you can' t do 4 thou track and spacing and 10 thou vias....
And how do you register top and bottom layers?
And as for mutilayers - that's tricky.
The CNC is only used for crude single layer things. The power stuff you do on strip board.

I started with rolls of 0.5-1mm wide etch resistant tape and an etch resistant drawing pen.
Then etch resistant rub-on transfers (pads and tracks).
Then moved to spray-on photoresist. Messy, smelly (has to be baked on), oneven, dust in it, etc.
Then the pre-fab photo sensitive boards. Then the iron-on transfer sheets (bad).

I think I produced the best boards with etch resistant transfers. I think it was "Letraset".
Not sure if you still can get that (I'm talking 30+ years ago).
...professionally made boards are so good and cheap I woudn't bother these days.
And maybe the slow boat is partially a good thing - it makes you check thoroughly before ordering..
When your design skill improve, it's indeed the only way.
Leo..
Title: Re: Homemade pcb with Photoresist method
Post by: allanhurst on May 16, 2017, 11:32 pm
In mobile phone design , using 6 or 8 layer boards 1.2mm thick, full of layout critical RF stuff and BGAs  with microvias etc, where every 'spin' costs an awful lot, I always insisted ( however loudly the management yelled about delays ) on a full day of team review before finally releasing the design.

  Found a lot of silly errors.

Allan.
Title: Re: Homemade pcb with Photoresist method
Post by: Boardburner2 on May 17, 2017, 03:16 am
. In there I found a vial of what looked like rivets. On closer inspection, there were 2 sizes, in which one fit perfectly into the other.. The hole through the center just happens to thing.
Sounds like through hole rivets , Farnell used to do them.

Csn be found on ebay.
Title: Re: Homemade pcb with Photoresist method
Post by: tinman13kup on May 17, 2017, 03:27 am
Sounds like through hole rivets , Farnell used to do them.

Csn be found on ebay.
Hot diggity, Farnell has them....but what's a pound???

As for Ebay..... I've not bought anything from there for a long long time. Too much junk being peddled there
Title: Re: Homemade pcb with Photoresist method
Post by: larryd on May 17, 2017, 03:39 am
I have a million of these.
When it comes to a home made PCBs, I would walk over a bed of hot coals to avoid it.

(http://forum.arduino.cc/index.php?action=dlattach;topic=477598.0;attach=212191)



Good old dayshttps://www.google.ca/search?q=pcb+rivets&espv=2&biw=1360&bih=643&tbm=isch&tbo=u&source=univ&sa=X&ved=0CCcQsARqFQoTCOLsx7O06MgCFZGliAodvyQGkg (https://www.google.ca/search?q=pcb+rivets&espv=2&biw=1360&bih=643&tbm=isch&tbo=u&source=univ&sa=X&ved=0CCcQsARqFQoTCOLsx7O06MgCFZGliAodvyQGkg)


Edit:

FYI
http://www.electricstuff.co.uk/pcbs.html (http://www.electricstuff.co.uk/pcbs.html)


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Title: Re: Homemade pcb with Photoresist method
Post by: Wawa on May 17, 2017, 03:45 am
Good for giving a heavy item like a small transformer/inductor some extra support on a single side board.
I also still have bags of them in the bottom of the drawer.
leo..
Title: Re: Homemade pcb with Photoresist method
Post by: larryd on May 17, 2017, 03:56 am
FYI
http://www.circuitmedic.com/products/201-3140G.shtml (http://www.circuitmedic.com/products/201-3140G.shtml)

(http://www.circuitmedic.com/web2/1/eyelet_set_tool_flare_160120_1.jpg)

(http://www.circuitmedic.com/web2/1/eyelet_set_tool_flatten_160120_1.jpg)


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Title: Re: Homemade pcb with Photoresist method
Post by: Wawa on May 17, 2017, 04:11 am
I just put a phillips head screwdriver on the thin end of the rivet, and hit it with a hammer.
Leo..
Title: Re: Homemade pcb with Photoresist method
Post by: aster94 on May 17, 2017, 05:11 pm
I will try a cheap transparent/tracing paper and see if it works with my laser printer

About the spray i will use the positiv 20, everyone suggest it and looks like no one had tried any alternatives

When i would need more than 2 boards i will go for sure for seed, pcbway or similar but for now i d rather to waste some time and as someone have smartly said i will double check my design doing manually the boards
Title: Re: Homemade pcb with Photoresist method
Post by: larryd on May 17, 2017, 06:53 pm
I use the negative pre sensitized board, less ink from the ink jet printer.


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Title: Re: Homemade pcb with Photoresist method
Post by: MarkDerbyshire on May 17, 2017, 07:46 pm
I use the negative pre sensitized board, less ink from the ink jet printer.


.
Depends on your circuit design on the amount of ink that is used
Title: Re: Homemade pcb with Photoresist method
Post by: larryd on May 17, 2017, 07:49 pm
With a ground plain.

(http://forum.arduino.cc/index.php?action=dlattach;topic=177629.0;attach=48710)

(http://forum.arduino.cc/index.php?action=dlattach;topic=177629.0;attach=48712)



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Title: Re: Homemade pcb with Photoresist method
Post by: Boardburner2 on May 17, 2017, 10:26 pm
Using the negative method i find that most printers cannot do large areas of dense black weather they are inkjet or laser.
Title: Re: Homemade pcb with Photoresist method
Post by: allanhurst on May 17, 2017, 11:25 pm
I had that problem years ago with a laser printer on acetate, giving 'whiskering' which had to be cleaned up.

My through hole plating was a bit of 22swg tcw.

I generally used pre-coated boards from eg Farnell.

double sided by drilling marker holes through  the acetate and board to align. Ferric chloride etch in an agitated bath.

Long time ago.

And no good for fancy stuff. But quick. Well, quicker than the slow boat or the local specialist. And cheaper . Back in the 90's I paid about £200 for a batch of 10 smallish double sided plated-thru  boards with a 7-day turnaround.

Allan
Title: Re: Homemade pcb with Photoresist method
Post by: aster94 on May 18, 2017, 12:32 am
Using the negative method i find that most printers cannot do large areas of dense black weather they are inkjet or laser.
i agree, i tried to do it on a simple paper and my printer wasn't able to do it all black
Title: Re: Homemade pcb with Photoresist method
Post by: larryd on May 18, 2017, 12:57 am
The link I made in post #1 mentions my method using an 8600 ink jet printer with clear overhead material.


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Title: Re: Homemade pcb with Photoresist method
Post by: aster94 on May 18, 2017, 03:36 pm
Another important question:

Which do you consider to be safe values for the width of the traces and the isolation? Obviously talking about homemade pcb

I use 16mil for the traces and 24mil of isolation,, you?
Title: Re: Homemade pcb with Photoresist method
Post by: larryd on May 18, 2017, 06:09 pm
I like 25mil traces 50 and 75 for power and grounds.
15 mil in tight places.
Use ground/power plains.
Thermal relief vias as needed.

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Title: Re: Homemade pcb with Photoresist method
Post by: CrossRoads on May 18, 2017, 06:36 pm
Ground vias also to connect the top & bottom ground planes.

More ground plane area also equals less copper to be removed for faster etching.

A trace width to current carrying capability calculator will show that 10 mil wide trace of 1 oz thick copper can carry 1A current with minimal temperature rise over the length of the trace.
http://www.pcbco.com.au/tracecalc.html (http://www.pcbco.com.au/tracecalc.html)
For example, I entered 1A, 10C rise 1 oz copper, 20C ambient, 20mm trace length (2cm, getting close to an inch).
A 10 mil trace is all that is needed.
So 10 mil for mA or uA signals is all you need, and nearly 2A supply current can be met with a 25mil wide trace.

Use ground planes, don't snake ground traces all over the place.

I'm pretty sure there are other calculators which use the latest IPC model where you can enter width, length, thickness, etc. and get a current capacity out of it, but I'm having trouble finding one. Most seem to go other way, start with current etc and get the needed trace width.
Title: Re: Homemade pcb with Photoresist method
Post by: larryd on May 18, 2017, 06:46 pm
Old eyes and shaky hands like 80 mil pads for PTH components.
Title: Re: Homemade pcb with Photoresist method
Post by: aster94 on May 18, 2017, 08:47 pm
@cross I used the same calculator once. i needed to make a bench power supply, and since i doesn t have any idea about these formulas i found it very helpful. Anyway i use 16mil instead of the 10 because i am scared to "lost" a trace with the homemade process

@larryd you use very big traces! Is it due to the current of your pcb or for the method you use to make them?
Title: Re: Homemade pcb with Photoresist method
Post by: CrossRoads on May 18, 2017, 08:54 pm
'Old eyes and shaky hands' is why MrsCrossRoads puts parts on the boards we build.
I can handle solder paste with a stencil, and sometimes have to do a board a couple of times when the stencil alignment is a little off, or I was a little uneven with squeegee pressure, or the paste got too thin over some pads while I squeegied, lots of ways to mess that up.
Title: Re: Homemade pcb with Photoresist method
Post by: larryd on May 18, 2017, 09:27 pm
IMO larger width traces have very little drawback.
Larger traces gives: more surface contact to the substrate, less resistance which can help in less noisy signals and more heat tolerance.

I am not a fan of widths 10mils or less, especially if there is room for say 25mils.

Narrow widths have their place especially with high density designs.
However, it doesn't seem reasonable to have a 60-80mil pad and then an exiting 10mil trace especially if a wider trace can be accommodated.

Do not forget to incorporate good path way layout and proper power supply decoupling.


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Title: Re: Homemade pcb with Photoresist method
Post by: larryd on May 18, 2017, 09:28 pm
"is why MrsCrossRoads puts parts on the boards we build."
Make sure you revisit her salary now and then.   ;)


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Title: Re: Homemade pcb with Photoresist method
Post by: CrossRoads on May 18, 2017, 09:34 pm
Well, she is driving a new 2L Turbo Convertible Beetle these days ;)

Actually it's a 2015, someone had traded it with just 1450 miles, on it, so we got a great deal on in it in December.  Baby blue, just like the '67 Beetle I had in college, that I taught her how to drive a standard in, only this one's got way less rust and the heat works and it has AC and it'll go more than 70mph on the highway without shaking 8)
Title: Re: Homemade pcb with Photoresist method
Post by: allanhurst on May 18, 2017, 09:41 pm
I take it , like Bob Pease, you're fond of old beetles. My brother had one, and I thought it was awful....

Allan
Title: Re: Homemade pcb with Photoresist method
Post by: CrossRoads on May 18, 2017, 09:56 pm
Not me, was just a car I could afford as a poor college student. It was gone when I went off to senior year, tired of dropping the engine to fix oil leak that made the clutch slip and ongoing electrical problems ...