Project: Photographic methods of making PCBs

You might be able to spin coat your photo-resist. That's what I did because we had it in the photo-lithography lab. Not designed to do PCB's, but I did them anyway. We also made trinkets by evaporating gold on glass and then doing the photo-lithography process. You do need an accurate way of measuring the light source and timing it for exposure. All of that part of the process was done for me.

It was something like spin coat, bake, expose and etch. So, I used a mask-aligner which is used to make IC's to make a PCB.
 

DPHigley

Joined Dec 21, 2016
4
David, please have a look at this post, I'm not sure if it will help you, but it's an alternative to what's being discussed here.
Thank you, but it looks to me as though the printer would be a substantial investment, and I don't think the volume I do would be worth it. It's pretty quick and easy to do the intermediate litho step. For the initial image, I'm using an inexpensive inkjet printer and "waterproof silk screen positive film", which works beautifully and requires only one layer for contact printing on the litho film.
 

DPHigley

Joined Dec 21, 2016
4
I've recently switched from chemical etching with ferric chloride to electroetching. Do people ever use this for PCBs? Awfully easy to set up, with a battery or two, a piece of copper on the other side of the tank that was pictured for sodium persulfate etching, and an electrolyte (solution of Root Kill) that will last indefinitely.
 
Lestraveled, I would like to say thank you for your very clear, and in depth, walk through of using the lithographic film to make a contact negative of your positive artwork. I have read articles before, of people doing it, but none of them gave the specifics on every step the way you did, and your presentation answered many of my questions, and have provided the boost in confidence to continue on a project I've in the works for years, but had slacked off on.
It would be taking your photographic process a step or two farther, by eliminating the printed positive, that you make the negative from, by using a large format camera to take a photo of the artwork, as it is displayed on a 32" 1920 x 1080 LCD monitor, with the camera setup for the proper reduction needed, to give the proper finished size negative. Or, for more resolution, use our 46" led TV, (with wife's permission), to display the artwork . I realize I will need to work out the display intensity required, vs the exposure duration, and the camera distance from the monitor and the reduction level will be different for the displayed size on the chosen monitor, but either display's size would enable a 4x to even 8x reduction, with an equal increase in resolution in the finished negative. I would be interested in input, from people with camera, or film experience, of the problems this process might present.
 
I thought I could give my two cents to the discussion, mailnly about the bed of tubes and the off contact problem. Bed of UV tubes is convenient, as it takes less space and time than using a 12 inch tall lamp with an unprotected 3w UV LED, so for the off contact issue I worked out my own personal solution, carried from the way similar professional devices work.

One of the main problems (especially with little PCBs) is that using a rigid PMMA sheet to flat down the PCB master may lead to an imperfect adhesion to the PCB surface. To fix this issue, I assembled a wooden frame and glued to it a cut of plastic sheet (the kind used to protect the floor when when painting rooms), then I used a small foam rubber rug under it and connected the whole structure to a pipe, tied to a vacuum cleaner. When exposing the PCB, I simply turn on the cleaner and the vacuum created under the plastic sheet holds the master in position no matter what the size is.

It looks more complicated than actually is:

20171006_111806.jpg

Bye

Paul
 

Janis59

Joined Aug 21, 2017
1,057
RE:""OK, enough about how I make PCBs. Now, lets hear how you do it.""
I use a three methods.
1) The iron method if there is only discrete transistors and no IC. The 1 mm and even 1/2 mm paths are well elaborated but DIP size is the smallest what is still stable. Technically is possible to produce even SOIC but the quality is rather poor.
2) if the count of similar pcb~s are at least 100 I apply the polyvinylspiritus with chromium red, to mix the negative photoresist. Quality is rather high, but anyway the soic is most best what is possible to squeeze out. However each pcb cost is very small, because that chemical I have collected for next 100 lifes.
3) Most often technique, however not very cheap - positiv-20 aerosol, blow, dry into 50 C hot-chamber, expose under 5x8 led matrix (400 nm) about 10 seconds and voila. Etch in the vertical quartz tank with air bubbler and pre-heating 50 C. Printing with COLOUR printer means that black is formed by three colours and contrast is far better than black-and-white printer, of course install that paint must be most bold, and correct the tone to about 120-130%. The quality of film of course is the base of all further, thus use a good printer. As the result - technically 50 micron wire on pcb will be reproduced quite well, but the question is how good is etching. But philosophycally, who is working with so thin wires?
 

spinnaker

Joined Oct 29, 2009
7,837
I have a couple of tips I would like to add.

I use a hybrid process of drilling with a cheap CNC machine then using the toner transfer method to create the runs.

If your process requires a lot of steps like mine then document your process. It is easy to forget what to do when if you take a break from the hobby for a while. I wasted a day on getting everything right. Now I have everything documented.

I may have mentioned it before but I use wax paper in the toner transfer method. Works great and essential to the hybrid process.

I usually use a lamminator to transfer the image, but I found that for really small boards the good old fashioned iron is better.

Why I do not mill my boards:

Simply I do not like the results. I think my issue is not enough RPM on my cheap machine. Plus it makes a mess. A lot of people mention the say that they mill because it is better environmentally. I just don't get it. Unless you have a really good vacuum system, you are creating a lot of fiber glass dust. A bit of muratic acid or ferric chloride is far less hazardous in my opinion.
 

spinnaker

Joined Oct 29, 2009
7,837
I just hit on a new material to print on for laser transfer. Parchment paper. The type from the grocery store. It pealed right off with no residue left behind. I have only tried it for the component side of the board for component placement. I will post back when I try it for traces but it looks very promising.

Edit I might also add that it transferred every bit of the toner.
 
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Janis59

Joined Aug 21, 2017
1,057
RE: Spinnaker
You speak about the ironing transfer method??
It have principal limit when work with ICs with distance between feet less than 0,3 mm. Simply path sides are too inaccurate. When work is with over mm wide path paper is OK and just every type of paper may be used at slightly elevated temperature, including general use of printer paper. However old type of advertisement chalk paper is best, and it is not disturbing if it previously had been printed in printery. Printery color stays with it and not being transferred.
So, when DIP tech, use an ironing and paper, when use a SMD, then only Positiv+ aerosol gives a accuracy good enough without of spiner. Spiner I use if I work with polyvinylalcohol - as it is cheaper than positivus but gives the same sub-micrometer resolution, I use if I have larger stok of pcb to work on. But for just one or few it has too much time to loss, with Positivus it is faster, cleaner, simpler, and more warranted result.
 

KL7AJ

Joined Nov 4, 2008
2,225
Happy New Year, Les....long time no see!
I have been experimenting with a number of semi-modern PCB fixin' methods. For one off applications, I still like plain old etching...mainly because the alchemist in my loves playing with vile roiling potions. It takes a lot less setup...(read "thought")... to throw together a hand-etched board than some other methods. Anyway, it's a skill the young whippersnappers need to know about anyway.

73!
Eric


First, I would like to pay homage to Wendy Marsden and her contribution of her thread on making PCBs with the toner transfer method. It is a lot of work to put together a thread like that. In that thread, she said she would like to see someone start a thread on the photographic method of making PCBs and thus, I was motivated to create this tread. Thank you Wendy.

This thread is about making PCBs using photographic processes beginning with transparencies (artwork) produced from a laser or inkjet printer. There is a lot of flexibility when you choose the photographic path. So, this thread is not about one way of making PCBs photographically, it is about all the ways to make PCBs photographically. Based on your set of conditions and preferences, there are a variety of tools and options that you can use to optimize your PCB fabrication. Each process has its benefits and its costs.

Many of us in this community have a lot of experience making our own PCBs and we have our own ways of how to do it. I think it would be truly interesting and beneficial to hear about how the other guy makes their boards and especially, why they do it that way. I know that I have wrestled with making PCBs for a long time, and some of those times, the PCB has won.

So, I will start by presenting how I make PCBs and why I do it that way. Afterwards, I will take each function and expand on it, so that you can, if you want to, use it in your PCB fabrication.
x
 

cmartinez

Joined Jan 17, 2007
6,750
Happy New Year, Les....long time no see!
I have been experimenting with a number of semi-modern PCB fixin' methods. For one off applications, I still like plain old etching...mainly because the alchemist in my loves playing with vile roiling potions. It takes a lot less setup...(read "thought")... to throw together a hand-etched board than some other methods. Anyway, it's a skill the young whippersnappers need to know about anyway.

73!
Eric



x
KL, unfortunately, Les hasn't logged in for than 6 months already.
 

ROB2019

Joined Apr 5, 2019
1
Hi,

I enjoyed your article on the Photographic methods of making PCBs. You made your own UV LED exposure light. I am trying to do the same and would like to know how you secured your high power UV LED to the alumina heatsink? Did you use heatsink adhesive only or screws as well?

Any info you can share would be greatly appreciated.

Again, great article.

Regards,

Rob
 

Janis59

Joined Aug 21, 2017
1,057
RE: Rob1019 ""You made your own UV LED exposure light. I am trying to do the same and would like to know how you secured your high power UV LED to the alumina heatsink? ""

Those 3W diodes are glued to 6-angular aluminium platelets about 15x15 mm, what are mounted in stripes. Both ends of stripes have an M3 nitting in holes, thus I brought some aluminium face-plate from older decommissioned apparatus 7mm thick, cut the A4 sized piece with not too big holes, and screwed the stripes in both ends. In one stripe I used 5 LEDs, and number of stripes is about 11. In corners of face-plate I drilled holes where four feets of 20cm long are positioning light source on table. All LEDs are switched in series and goes to the 220V mains via corresponding 20W large sized resistor. Firstly I tried the ballast inductor from Hg long-lamps, but after third burned LED I throw this out and substituted to purely resistive ballast. From that time I had no trouble about burned-out LED.
 

beanpole

Joined Aug 17, 2017
1
My first thought was, "What a cool dude to spend the time to write this up". I've made a dozen or so boards in the past but the active components were in TO-92 packages. My first board's active components had 12 volt filaments! I'm now retired and have designed a circuit that uses a bunch of SMD semiconductors. I'm going to take advantage of your hard earned experience and if I'm successful maybe I'll do a write-up too. THANK YOU!!!
 

cmartinez

Joined Jan 17, 2007
6,750
My first thought was, "What a cool dude to spend the time to write this up". I've made a dozen or so boards in the past but the active components were in TO-92 packages. My first board's active components had 12 volt filaments! I'm now retired and have designed a circuit that uses a bunch of SMD semiconductors. I'm going to take advantage of your hard earned experience and if I'm successful maybe I'll do a write-up too. THANK YOU!!!
Yes... it'd be nice if you were to come back to this thread and share your findings with us. :)
 
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