How to make perfect PCB's if transparency printing is non-existant

Thread Starter

mike_canada

Joined Feb 21, 2020
239
Until recently, I have been able to make PCB's from presensitized boards at close to 100% success rate because I ordered my designs on transparencies produced by a printing shop.

Today, the print shop I relied on no longer prints on transparencies. I searched for other places, and the only two local ones I come across that could possibly do it but at high prices are "Crush Media" and Staples copy and print (both have their pitfalls) but with the way supply shortages are going, who knows how much longer they can support transparency printing.

So let's assume transparency printing is no longer an option.

I do have a printer at home but it's not capable of printing sharp black images. It can do greyscale but the images sometimes have dots or the printer sometimes prints bleed marks, both which are NOT good for PCB development.

What someone suggested (I think it was from Mike's PCB website which is no longer accessible) is that vellum paper may work. I had limited success with that but I had to print 2 copies of the image and tape them together and if the alignment is not perfect, then my circuit will be messed up.

So what am I to do? I still have pieces of positive presensitized PCB and I want to eventually make nice circuits out of them.
 

Ian0

Joined Aug 7, 2020
6,293
Presensitised board is getting expensive, especially if it doesn't work first time. I just send mine off to China. I get plated through holes and solder resist - something I can't make myself.
 

Thread Starter

mike_canada

Joined Feb 21, 2020
239
I don't think that method (toner transfer) will go well with me especially with ironing because you'd have to get the image on secure enough or any toner that doesn't stick to the board, the surface underneath will be etched away. I already own a professional UV light box which is why I have been doing the photo-transfer method with transparencies for many months. Presensitized PCB's aren't too bad in price (unless I order from a local supplier) considering that prices are rising in many categories.
 

DickCappels

Joined Aug 21, 2008
9,317
Yes, toner transfer requires a lot of care. There are many small details required to get good quality boards.

Way back in the 1970's I had pretty good success with pre-sensitized boards. I used black tape on clear Mylar to lay out the circuits and then used sunlight to expose the boards. It was beautiful but too much work for regular production. I then moved to professional photography companies who could make the necessary negatives for my home-spun process.

After pre-sensitzed board became unavailable I went on to the painful process of using toner transfer. I think those who use low cost Chinese PCB manufacturers are probably the best choice if you are confident about your design.

Another approach is to use a Demmel or equivalent with a router bit for simple circuits.

1660092486950.png
 

boostbuck

Joined Oct 5, 2017
239
I have for a long time now (and still do for quick one-offs) used two layers of transparency film printed on a laser printer. I've done dense boards up to 5" x 5", although beyond that a laser registration is a bit poor.

It's possible to purchase special inks for ink-jets that are designed for photo exposure, and although I haven't tried it a friend uses it and I was very impressed - better density than a laser, so doesn't require two layers.
 

MrSalts

Joined Apr 2, 2020
2,354
I don't think that method (toner transfer) will go well with me especially with ironing because you'd have to get the image on secure enough or any toner that doesn't stick to the board, the surface underneath will be etched away. I already own a professional UV light box which is why I have been doing the photo-transfer method with transparencies for many months. Presensitized PCB's aren't too bad in price (unless I order from a local supplier) considering that prices are rising in many categories.
Toner transfer doesn't work and isn't desirable with presensitized Copper boards.I think there was a confusion in some posters not reading the original post.
 

DickCappels

Joined Aug 21, 2008
9,317
A few years ago I made a PCB for a 5kw temperature control for my on-demand water heater. I needed very wide traces to carry the current without burning the board so I used fingernail polish, just like my first PCB more than 50 years ago.
 

BobTPH

Joined Jun 5, 2013
5,759
Which brand/model printer and which brand of cartridges are you using?
Laser jet M15W

Previously

Laser jet p1102 I think

Both with genuine HO toner.

I print with highest density setting.

And I get good results at 10 mil traces, spotty at 8 mil.
 

ScottWang

Joined Aug 23, 2012
7,295
I use a laser printer to print transparencies with great results.
I used that way before.

About 6 years ago, when I was still in Taipei and helped a friend in his own company to design the PCB (control board) with the 32Fxxxx series IC, then I used the PCB design software to design the double sides PCB on a computer, and then as you did use the laser printer to print the layout on the transparencies, but there was one thing that I should do was before printing on the standard transparencies, I have to print the layout on a paper and transparency to do the test first because the transparencies have malleability when it meets the heat(from the laser printer) will expanding the size a little bigger, when it cools down will back to the original size and the printing percentage is about 99.1~100%, it depends on the different material of transparencies or made by a different company.

Do you have a such heat issue when you use the laser printer to print the layout on the transparencies?
 

dl324

Joined Mar 30, 2015
15,112
Do you have a such heat issue when you use the laser printer to print the layout on the transparencies?
Transparencies intended for laser printers won't have issues. FWIW, I use HP inkjet transparencies in my laser printer for toner transfer. I've tried other brands of inkjet transparencies in my laser printer. Didn't have problems with any of them melting, but none of them worked very well for toner transfer.
 

BobTPH

Joined Jun 5, 2013
5,759
I used that way before.

About 6 years ago, when I was still in Taipei and helped a friend in his own company to design the PCB (control board) with the 32Fxxxx series IC, then I used the PCB design software to design the double sides PCB on a computer, and then as you did use the laser printer to print the layout on the transparencies, but there was one thing that I should do was before printing on the standard transparencies, I have to print the layout on a paper and transparency to do the test first because the transparencies have malleability when it meets the heat(from the laser printer) will expanding the size a little bigger, when it cools down will back to the original size and the printing percentage is about 99.1~100%, it depends on the different material of transparencies or made by a different company.

Do you have a such heat issue when you use the laser printer to print the layout on the transparencies?
I have not noticed any discrepancy in size, but the biggest PCBs I’ve made ar about 3 inches.
 

sparky 1

Joined Nov 3, 2018
731
The photosensitive method is still being used and it has improved.
The transparency went to milky transparent with enhanced microporosity on one side for better opaque and no smudge.
The 36W UV light source that is used for curing nails (hand size) set at 30 seconds and the pre-sensitized film is very cheap.

The reason for going with dry film photo resist during prototype stage is not having to wait 2 weeks or more for turn around.
Experimenting objectively for procedures and calibration can lead to nice quality.
There are times when the pcb cad and gerber file method will get it done, depending on your experience and the complexity of the circuit.

For me there is an ugly stage, that is where I modified a section or two with plug in strip board and when that prototype is working you stop messing with it. You do a revision on the art work, photo etch a couple new boards, The awful and ugly board is only used for design reference it shows how and why the revision was made. Usually there is a pile of resistors. capacitors and various transistors that were tried and are put in a small zip bag taped to the ugly board. The time is usually spent looking for improvement. desoldering parts, checking results on the oscilloscope. I usually don't rush through revision on the new photoetched board and the revised parts need to be added to the schematic.

A DIY video that shows some of the later methods, there is not much complexity but as a simple example done in about 2 hours.
Some of my sharpy hand drawn boards look awful but get done, etched and populated in a half day sometimes ready for cad.
 
Last edited:

techman-001

Joined Jan 13, 2021
7
Until recently, I have been able to make PCB's from presensitized boards at close to 100% success rate because I ordered my designs on transparencies produced by a printing shop.

Today, the print shop I relied on no longer prints on transparencies. I searched for other places, and the only two local ones I come across that could possibly do it but at high prices are "Crush Media" and Staples copy and print (both have their pitfalls) but with the way supply shortages are going, who knows how much longer they can support transparency printing.

So let's assume transparency printing is no longer an option.

I do have a printer at home but it's not capable of printing sharp black images. It can do greyscale but the images sometimes have dots or the printer sometimes prints bleed marks, both which are NOT good for PCB development.

What someone suggested (I think it was from Mike's PCB website which is no longer accessible) is that vellum paper may work. I had limited success with that but I had to print 2 copies of the image and tape them together and if the alignment is not perfect, then my circuit will be messed up.

So what am I to do? I still have pieces of positive presensitized PCB and I want to eventually make nice circuits out of them.
I've used the laser printer on 'drafting film' transparancy method since the 90's with good results. As you say the prints will have random pinholes so I align two prints and tape them. This reduces the pinholes dramatically.

Drafting Film is is almost invariably made of transparent biaxially oriented polyethylene terephthalate (says wikipedia) and it looks ground, so it's opaque. I buy mine from a drafting/painter supply shop in a A4 book of sheets.

I've used at least 3 different laser printers for this job, the best ones were older secondhand HP office machines, but they all worked and the method is fast and accurate.

Below is a link to a pic of a pcb I hand-made in 1999 using this method, it was in my leather wallet (like a credit card for 15 years) and was very tarnished, a quick rub with wet and dry paper under running water and the pic was taken.

https://mecrisp-stellaris-folkdoc.sourceforge.io/pcb.html

Cheers,
Terry
 

Thread Starter

mike_canada

Joined Feb 21, 2020
239
ok so right now, I am trying deep black print method on vellum.
When I put the vellum in the exposure unit, the lights frosted the paper. This time I try exposing for 4.5 minutes (without taping 2 pieces of the image together) as opposed to the 3 mins on transparency. Currently in the etching stage instead of the areas without traces being clear, they are dots of copper.

I'm praying this will work because I'm using alot of board. then again I had the board for almost a year.
 
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