Homebrew_PCBs

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 pdfs. 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 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.

Thanks you, I am new here and in the UK, I have much to learn!

Chris,

The pdfs look fine on the screen, but this is not the issue. We had a discussion here some months ago about the density of laser printed artwork. It turns out that the laser printed output is a series of small particles that are fused to the surface and each other. Although they are fused, the result is not a continuous line, but a porous one that allows light to leak through. I have seen two work arounds. The first is to make two transparencies and stack them, banking on the fact that the pores will mostly not line up. The other is to use a spray that increases the density of the print by chemically melting and fusing the particles.

There are a number of commercially available sprays. Do a Google search on "laser toner darkener." The discussion here also mentioned spraying with clear paint, such as Krylon. I tried it with either Krylon or Rustoleum clear spray. The transparencies became much more dense. I didn't try making any boards, I just was experimenting to see if the artwork showed improved density. I did note one problem with this approach. It was difficult to get the right amount of spray on the artwork without puddling and causing the traces to distort. I suppose that with practice my technique would improve.

Harvey

 

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 pdfs. 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 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.

Thanks you, I am new here and in the UK, I have much to learn!

I don't claim to be a professional and have the correct solution here

BUT I DO HAVE A SOLUTION that works for me.

STEP 1:
ANY time I have a PDF file as a circuit board source I open that PDF file with GIMP image editor.
If its more than one page then I only open the page I want to work on.
The file OPEN options asks you if you want to open multiple pages as layers or images.
I JUST OPEN ONE PAGE as an IMAGE.

STEP 2:
I use the rectangle image selection tool and then use the IMAGE drop down menu and
CROP TO SELECTION

STEP 3:
I go to the COLOR drop down and use the THRESHOLD option
and this IS THE CURE FOR PDF GRAYSCALE images because just opening this THRESHOLD option
SLAMS THE IMAGE TO BE DENSE BLACK LINES on white background.
I hit the OK button and then

STEP 4:
from the FILE menu
EXPORT AS
and select new-file-name.jpg

which saves it as a jpg.


STEP 5:
I use my folder browsing to display the saved JPG
then I select PRINT
and examine my component spacing.
NOTING THIS IS NOT DONE IN GIMP

I always check what printing  from file folder browsing will produce because
GIMP may not be on ALL PCs I send this JPG to.

IF the final paper does not have the precise match to components then I use
STEP 6:
back in GIMP and use the IMAGE drop down menu to select SCALE IMAGE
and then make it bigger or smaller by PIXELS or PERCENTAGE or millimeters.
Here is an example of accuracy just by the above method:
http://www.learnmorsecode.com/laminator/pic/PIC16F628PROTO8d.jpg

Here is one of YOUR PDF circuits... before and after THRESHOLD adjustment:
http://www.learnmorsecode.com/tracetest/tracetest.html

Have fun with GIMP.

 

Chris,

The pdfs look fine on the screen, but this is not the issue. We had a discussion here some months ago about the density of laser printed artwork. It turns out that the laser printed output is a series of small particles that are fused to the surface and each other. Although they are fused, the result is not a continuous line, but a porous one that allows light to leak through. I have seen two work arounds. The first is to make two transparencies and stack them, banking on the fact that the pores will mostly not line up. The other is to use a spray that increases the density of the print by chemically melting and fusing the particles.

There are a number of commercially available sprays. Do a Google search on "laser toner darkener." The discussion here also mentioned spraying with clear paint, such as Krylon. I tried it with either Krylon or Rustoleum clear spray. The transparencies became much more dense. I didn't try making any boards, I just was experimenting to see if the artwork showed improved density. I did note one problem with this approach. It was difficult to get the right amount of spray on the artwork without puddling and causing the traces to distort. I suppose that with practice my technique would improve.

Harvey

On 9/17/2017 1:09 AM, chris@... [Homebrew_PCBs] wrote:

 

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 pdfs. 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 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.

Thanks you, I am new here and in the UK, I have much to learn!

In my opinion the best way to obtain a truly black image using a laser printed image is to run your laser printed transparency through a laminator with a piece of "toner reactive foil". This is the same stuff that some people use when making toner transfer PCBs to cover the transferred toner to get better results when etching the board.

This material is not entirely opaque when held up to a bright light but when combined with the toner makes for a really opaque negative. I have used the black pigment type with good results. Although it appears to be the same as the foil used for "hot foil stamping" in the printing industry, I have seen some claims that the composition is slightly different. I have not seen the various metallic colored "toner reactive foils" but based on what I saw years ago with the gold and silver "hot foil stamping" material I would suggest using pigment colors as the gold and silver colors were not quite as opaque. 

Black is probably the best choice however, red should work as well and could possibly even work better given that the red should block the ultraviolet light, possibly to a greater extent than the more neutral black.

I'm pretty sure any cheap laminator will work adequately. You probably do not need a high-end laminator as you would for doing toner transfer to a PCB.

You can find this material on Amazon or eBay as well as from Pulsar - the people that sell the green foil for use with PCB toner transfer and white foil for labeling PCBs. The section of their website that sells materials for making decals sells other colors including black. (https://colorfoils.com/buy-now.html)

You may still end up with a few random pinholes (from dust in your printer etc.) which can be touched up with a Sharpie or, better yet, a red or black "opaque pen" made for touching up film negatives in the printing / graphic arts industry such as : http://www.gwjcompany.com/index.php?main_page=product_info&products_id=6 or http://www.gwjcompany.com/index.php?main_page=product_info&products_id=4

Craig