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 PDF images for photoresist PCB board making 
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Post PDF images for photoresist PCB board making
I had a kind guy in Germany offer to convert photos of three existing mint, populated PCB boards that are the same as three others in an obsolete power supply that have suffered damage over the years from repairs and lifted tracks. The pdf's looked great and were, when printed "actual size" absolutely spot on. But the images from the pdf whether on semi opaque "tracing" type paper or clear acetate sheet are not fully opaque, unlike some commercial ones that I found in my secondhand UV box when I bought it. I used an oldish HP B&W laser printer here at home, then sent the pdf files to a commercial printer who used some sort of plotter to print to acetate, but still the tracks are only semi opaque, and when I expose photoresist board the pads and some tracks seem to have had patches exposed to some UV so they develop at different times to other regions. this the affects etching....

Could someone kindly look at the pdf's and say if it's an issue with the density of the black in them, as they sort of appear a bit greyish... I have etched boards in the past with photo resist and had no great issues, but these are being a pain! It may be nothing to do with the density of the tracks, it may be my techniques, but I thought i should start at the beginning as I am not sure just what magic he used to go from photos of the tracks on a populated board to pdf's. I can drill the finished boards on a mill with a DRO, all the components are leaded, save 2 small IC's that I will socket. I can use the DRO to get perfect, accurate hole spacing for them. But first I need usable boards! The images in pdf form are at http://www.gatesgarth.com/traces.pdf I am working with Page 4 the traces only, mirrored ones.

Thanks


Sun Sep 17, 2017 8:20 am
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 PDF images for photoresist PCB board making 
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Post Re: PDF images for photoresist PCB board making
I've never liked PDF's for anything like this, because usually they are just images pasted on a PDF document. I have just tried my old trick of going to PDFescape and deleting the pages I don't want and saving the page I want to work on, then importing it into LibreOffice Draw and converting it to a Bitmap file, use Bitmap rather than JPG because you will lose resolution in the JPG.

The you can then fiddle with the brightness, contrast and whatever else till you can the image you need. Worth a try?

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Sun Sep 17, 2017 8:46 am
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 PDF images for photoresist PCB board making 
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Post Re: PDF images for photoresist PCB board making
No, for get that, I'm losing too much resolution.

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Sun Sep 17, 2017 8:58 am
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 PDF images for photoresist PCB board making 
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Post Re: PDF images for photoresist PCB board making
What photoresist are you using?

You may need to flash it first.

My laser printer does not give a completely opaque positive, but with correct exposure and developing, I don't have a problem.

If it is really bad, flashing will help.

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Sun Sep 17, 2017 9:17 am
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 PDF images for photoresist PCB board making 
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Post Re: PDF images for photoresist PCB board making
Thanks for trying Paul, much appreciated, so it could be that the pdf images themselves are the cause? Shame because the sizing and resolution are excellent, but I did wonder if somehow the printing of them comes out less opaque for whatever reason. Any work arounds welcome if people think this is my problem :)


Sun Sep 17, 2017 9:20 am
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 PDF images for photoresist PCB board making 
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Post Re: PDF images for photoresist PCB board making
Sangoma wrote:
What photoresist are you using?

You may need to flash it first.

My laser printer does not give a completely opaque positive, but with correct exposure and developing, I don't have a problem.

If it is really bad, flashing will help.



It's from Rapid, and I have to admit the board was over a year old, but kept in a thick paper folder in a dark drawer. I have some new board, and the recommended developer just come, from rapid again. maybe I should run another board? Perhaps a test board pulling a card cover slide to try different exposure times on the same PCB? The cover exposes different slices of the board surface for shorter and shorter times...?

Thanks.


Sun Sep 17, 2017 9:23 am
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 PDF images for photoresist PCB board making 
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Post Re: PDF images for photoresist PCB board making
Basil wrote:
Sangoma wrote:
What photoresist are you using?

You may need to flash it first.

My laser printer does not give a completely opaque positive, but with correct exposure and developing, I don't have a problem.

If it is really bad, flashing will help.



It's from Rapid, and I have to admit the board was over a year old, but kept in a thick paper folder in a dark drawer. I have some new board, and the recommended developer just come, from rapid again. maybe I should run another board? Perhaps a test board pulling a card cover slide to try different exposure times on the same PCB? The cover exposes different slices of the board surface for shorter and shorter times...?

Thanks.


Yes, that would help, maybe with a positive with some fine tracks and solids.

The strength and temperature of the developer should be so that it takes about the recommended time to develop, as just leaving it in too long will result in lost fine tracks and broken solids.

Over exposing will do the same.

The transparency should be made so that is is toner side against the board when exposing.

Too short exposure or under development is slightly preferable to the other way round, as you can scrape off excess copper, but you can't add missing copper back.

I usually use Positiv 20, and it works very well.

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Sun Sep 17, 2017 9:40 am
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 PDF images for photoresist PCB board making 
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Post Re: PDF images for photoresist PCB board making
I gave up on photo based PCB making some time ago. I'm getting much better results with toner transfer/TRF foil.

Do a bit of reading up on it and see if it's for you or not.

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Sun Sep 17, 2017 9:49 am
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 PDF images for photoresist PCB board making 
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Thanks for the further replies. Having bought fresh photoresist board and chemicals I will persevere for now with this method, but for sure will give the toner transfer and TRF foil methods a go at a later stage. May I ask G0SLV what machine, if any, he uses to heat / compress the foil to the PCB? The ones I see as known to work are in the USA and 110V AC. Thanks again. 2E0ILY


Tue Sep 19, 2017 10:34 am
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 PDF images for photoresist PCB board making 
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Post Re: PDF images for photoresist PCB board making
Basil wrote:
Thanks for the further replies. Having bought fresh photoresist board and chemicals I will persevere for now with this method, but for sure will give the toner transfer and TRF foil methods a go at a later stage. May I ask G0SLV what machine, if any, he uses to heat / compress the foil to the PCB? The ones I see as known to work are in the USA and 110V AC. Thanks again. 2E0ILY


I use a cheap laminator called "Creative A4" model PET 5278 that I modified to run hotter. Many people have good success with Peak PP260 with the heat turned up full, but it may take several passes. It tales some experimentation to get it right, so if you need an out of the box solution, it may not be for you. However, there's a wealth of information on the internet, and once you have it right, it's extremely good.


This guy uses the Peak laminator for Graphix FX Pro... which is essentially the same thing, but transferring the toner & foil to mylar carriers to make decals.



https://www.youtube.com/watch?v=0gzKMgtGBOY&t=4s

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Tue Sep 19, 2017 7:58 pm
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 PDF images for photoresist PCB board making 
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Post Re: PDF images for photoresist PCB board making
Some great info, thanks to all for advice and links! 2E0ILY


Thu Sep 21, 2017 9:18 am
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