Scanning an existing PCB ?

[Jolly 7]

I have never made my own PCBs and normally use copper stripboard or perforated board to complete my projects. However, I have an old predesigned PCB that I want to use for an upcoming project and once I use that I'll have no more of the same. Should I wish to recreate a copy of the same board in the future, are there are any recommended file formats that can be used to store the image ? I have both a flatbed scanner and a digital camera. Can anyone please advise ?

Anything lossless (GIF, BMP etc.) will do. I would go for BMP, seems to be a standard that just keeps on going it does use a lot of memory but that is very cheap these days.

[Terry_VK5TM]

Or PDF, plus might I add, keep a note of the dimensions of the original pcb, scanning/photographing can cause aberrations that can distort the size of the pcb if not done properly.

[Jolly 7]

Great. Thanks for the advice. Although not a perfect rectangle owing to a speaker in a cabinet, the PCB's small enough to trace around with a pencil.

[David G4EBT]

Do you mean an actual PCB which you wish to scan so you have an image - however poor it might be, from which you can create the artwork to use to make another PCB? If the PCB is already populated with components soldered in, I don't think you'd have much success in getting a decent copy using a flatbed scanner, but if you can take a photo on a digital camera with the camera square on, you could use that as a basis to create a mask, using whatever program you're competent with.

I save my designs as PNGs.

I guess that really answers your query, but some comments on PCB production might be of help and interest. If not, just file the rest of this post under 'Burn before reading'!

I'm not sure what method you'd use to make your PCB. The simplest is of course to get it made commercially, which requires a 'Gerber file' to be sent to a PCB company. I'm told that the prices aren't exorbitant, but have no personal experience.

As to DIY PCBs, depending on the method used to make the PCB, you'll need either a positive or negative of the design. It's simple to convert a positive to a negative - I do that using MS PAINT. Simple 'select' the design, right click on it, then use the drop down menu to click on 'invert colour'. Everything that's black will become white, and vice versa. Then save the design as a negative.

For most DIY PCBs, it comes down to three options:

Firstly, to place the design over the laminate and drill all of the holes as reference points, then 'join the dots' using resist of some sort - 'Dalo' type pens, which I've never had success with, or rub-down transfers, which are now next to impossible to find, and are quite a challenge to use on all but the simplest PCBs.

Secondly, the 'laser printer-iron on' technique known as 'toner transfer' whereby you print off the positive artwork (in reverse) on glossy paper, iron it onto the PCB laminate, then soak off the paper in warm water, leaving the toner on the PCB. I've not tried it, but many claim success an there are lots of youtube videos to show how its done. This method has the merit that if you only need the occasional PCB, no special equipment beyond a laser printer is required, and you don't need an acetate mask.

Thirdly, UV exposure: There are two methods - one requires a positive mask, the other, a negative mask. Both require a UV exposure box, and however basic that may be, it's a complete turn off and quite a faff for anyone just wanting the occasional PCB, but it might be worth a re-run of how it's done on a DIY basis:

Positive mask: The norm until maybe two years ago was to use either pre-sensitised positive UV laminate or to use a UV positive lacquer spray. I abandoned pre-sensitised laminate as it was quite expensive, and I ended up with useless offcuts. Also, the lacquer was thin, the exposure time was fairly critical, as was the strength of the developer. The board was either over or under exposed, or the developer a little too strong so I ended up with a plain piece of board. I resorted to self-spray positive UV lacquer with a good level of success and if things went wrong, I could at least remove the lacquer with meths or acetone, re-spray and start again.

Negative UV 'dry film': This last two years ago the use of this film have become the norm. It has the merit of being cheap - for example, a roll of film 30cms wide x 1 Metre long, or 15cms wide x 2 Metre long is typically no more than £3.00 post free. The UV film has a protective clear film on either side. One side is peeled off using Sellotape then the film is placed onto the laminate, eliminating all bubbles, then the laminate with film attached is passed through a laminator to seal the film to the board. It's then placed in the UV light box along with the negative mask and exposed for 60 - 75 seconds. (All black areas of the mask will be washed off by the developer, all clear areas will remain on the PCB, hence, the design has to be a negative).

The second protective film is peeled off and board is then place in developer - just a level teaspoon of soda ash dissolved in 100ml warm water. Soda ash is cheap, plentiful and innocuous.

The PCB is then etched, after which the UV resist is removed by immersing the PCB in acetone for a minute or so. (Then you need to drill it).

The creation of a UV mask can pose problems, particularly with modern printers. There was a time when you could print off dense OHP acetates in ink jet printers, but with the abandonment of OHP projectors in favour of Power Point presentations, few home printers have an acetate setting. No Epsons for example. Laser printers have never been good at printing dense acetates, but some users get away with taping two or even three designs over each other.

The only satisfactory film I've found for creating masks is 'micro-porous' acetate such as this, which prints solid black and makes excellent masks:

https://www.homecrafts.co.uk/acetate-film

It's nuts of course, but it keeps me occupied and stops my kids from putting me in a home!

[Terry_VK5TM]

Originally Posted by David G4EBT

...Laser printers have never been good at printing dense acetates, but some users get away with taping two or even three designs over each other.

Sorry David, but I have to disagree with you there.

For many, many years, all I ever used was a laser printer to produce my negatives using only a single sheet of film, even when doing pcb's commercially.

I have a Canon LBP3000 laser which has no problems producing the required artwork.

It comes down to using the correct film to do the job.

In my case, Novasharp Diamond Laser Printer Film.

[David G4EBT]

Thanks for reading my post Terry and for your comments - no need to apologise for disagreeing.

It's good to know that the right printer with the right film in the right hands works very successfully.

I had an inkjet HP Photosmart printer which produced excellent masks using normal OHP film, but it stopped working in 2010 and I replaced it with an Epson SX535 inkjet printer. I tried various settings and types of acetate but the results were dire. I got in touch with Epson who were no help at all and said that none of their domestic printers would print onto acetate.

In desperation, I got several friends to try printing onto acetate in their laser printers, none of which produced any better results than a commercial photocopier machine. If the acetate was held up to the light, what was supposed to be solid black was just 'grainy' and not opaque. I also got two friends who worked in offices with commercial laser printers to give it a try, and the results were no better than on domestic printers, hence my earlier remarks.

For a short while, I used my ink jet printer, resorting to taping two or three copies together, which took me back to the days in the 1980s when we didn't have home printers, or come to that, even computers. Back then, like most PCB DIYers all I could do was to get artwork - often magazine pages - printed onto acetates at copy shops and tape one over another. All very hit & miss.

Then Joe - 'Pillenwerfer' - tipped me off about a youtube video by 'Big Clive' which showed how to fool Epson printers into printing properly onto acetate. I created a PCB setting in the printer options based on Clive's advice, and that's what I use now, but by using 'micro-porous film' I get much better results than using standard OHP acetate sheets.

I've tried all the other options for creating masks such as using both normal paper and tracing paper (known as 'vegetal paper' in many countries outside the UK), sprayed with 'transparentizer' or WD40, with no success.

As I said earlier, I think for most people who just wish to make the occasional PCB and have access to a laser printer, on the face of things, the ‘toner transfer’ method seems to have much to commend it. A google search for 'Toner Transfer PCB process’ brought back 2 million hits. Here are a couple of videos as examples:

https://www.youtube.com/watch?v=gm9gw3OwdLA

https://www.youtube.com/watch?v=haqP8xhsYas

Another toner transfer method video using no heat:

https://www.youtube.com/watch?v=cVhSCEPINpM

[Jolly 7]

Hi David. The PCB is mostly unpopulated and I only need to desolder one or two components before taking a picture. I have been using Photoshop Elements for many years and although I haven't used the png format before, this shouldn't be an issue. However I still need to know how to completely remove the background of my photo i.e. I need only the circuit tracings in the picture file that will be used to create the duplicate. Otherwise the background will form an unwanted part of it. Any expert tips on how to remove this please ?

I like the heatless toner transfer method. Thanks for sharing this.

I have seen adverts for a Chinese company offering free PCBs with a first order. This might be useful for anyone trying to create a one-off PCB, but I think you need to send them a gerber file.

[Terry_VK5TM]

Not sure about how to do it in Photoshop Elements (only because I don't have a copy), but the PNG format can have a 'transparent' background.

It does mean that the background colour will have to be very uniform for it to work.

The other option of course is to scan it as a black and white image and touch up the tracks and erase any oddities on the background.

Another option (if you don't mind a small wait), is to send me a scan in BMP format with all the relevant details about size etc and I can convert it as I did with the Mini Mod pcb in the other thread.

That will give you both gerber files if you wanted them and I can convert to pdf or clean BMP to send back to you.

[David G4EBT]

Originally Posted by Jolly 7

Hi David. The PCB is mostly unpopulated and I only need to desolder one or two components before taking a picture. I have been using Photoshop Elements for many years and although I haven't used the png format before, this shouldn't be an issue. However I still need to know how to completely remove the background of my photo i.e. I need only the circuit tracings in the picture file that will be used to create the duplicate. Otherwise the background will form an unwanted part of it. Any expert tips on how to remove this please ?

There is the 'Paint bucket' tool in Elements which - when you've selected the background/foreground colour enables you to pour the desired colour over the background. So in theory at least, if you select the colour (white for the background - black for the tracks), you should be able to tidy up the image. However, whist that's fine for say drawings with areas bounded by solid lines, I've not found it very good on pictures, but it could be worth a try. I've used that facility to for example clean up untidy background or faded areas of a circuit diagram. You've also got the eraser tool.

Depending on how complicated the picture is, I sometimes use MS 'Paint' to remove areas of background leaving the areas white. By selecting a wide line and making the line white, you can draw along the edges of PCB tracks to neaten them up. If the tracks themselves ae untidy, you can use the solid back line tool or 'brush' tool to neaten them. It's do-able on a small PCB - say up to 7.5cms square, but much more than that and it becomes laborious.

Terry has made a very kind offer, so maybe that would be the best route to follow and you'd then have the benefit of a Gerber file too.

A picture of the PCB would be interesting when you're able to take one.

[Colin G8TMV]

Originally Posted by Jolly 7

However I still need to know how to completely remove the background of my photo i.e. I need only the circuit tracings in the picture file that will be used to create the duplicate. Otherwise the background will form an unwanted part of it.

Convert the image to black and white and then increase the contrast a lot. Assuming the background is lighter than the tracks the background should drop out to white. If it turns out as a negative then I'm sure there is a tool to invert it.

Colin

[dr_nick]

I don't know whether you've managed to try out different ways of capturing the image yet; but if possible I'd suggest using a vector format if you can of the board alongside a reference rule. Vector images re-scale in proportion and can usually be converted easily to raster formats. And most vector formats (such as PDF and EPS) are printer ready.

Some scanning software can be selected to give black and white imaging directly in high resolution (as against monochrome).

Hope those thoughts are of some use.

Nick.

[Maarten]

Originally Posted by Terry_VK5TM

Or PDF, plus might I add, keep a note of the dimensions of the original pcb, scanning/photographing can cause aberrations that can distort the size of the pcb if not done properly.

Please note that the PDF format internally uses either a lossy or a lossless compression format, so you have to know what your particular software does. I think PNG and JPG are the most popular formats but of course it does natively support vector formats as well (but a scanner cannot output those, so not relevant in this case).

That said, a flatbed scanner set to a lossless format (png, gif, tiff, bmp in order of preference) would be the best way to digitize the board layout or at least to create the raw file used in making a pdf.

[Jolly 7]

Originally Posted by David G4EBT

There is the 'Paint bucket' tool in Elements which - when you've selected the background/foreground colour enables you to pour the desired colour over the background. So in theory at least, if you select the colour (white for the background - black for the tracks), you should be able to tidy up the image. However, whist that's fine for say drawings with areas bounded by solid lines, I've not found it very good on pictures, but it could be worth a try. I've used that facility to for example clean up untidy background or faded areas of a circuit diagram. You've also got the eraser tool.

Depending on how complicated the picture is, I sometimes use MS 'Paint' to remove areas of background leaving the areas white. By selecting a wide line and making the line white, you can draw along the edges of PCB tracks to neaten them up. If the tracks themselves ae untidy, you can use the solid back line tool or 'brush' tool to neaten them. It's do-able on a small PCB - say up to 7.5cms square, but much more than that and it becomes laborious.

Terry has made a very kind offer, so maybe that would be the best route to follow and you'd then have the benefit of a Gerber file too.

A picture of the PCB would be interesting when you're able to take one.

@David
Apologies for the delay. The PCB went into hiding for a while but I managed to find it. It belongs to a DIY pocket radio but came without components or markings on the board. It's around 30 years old and was purchased abroad. It has been used for some small experiments but never fully populated to work as a radio.
Hope this might be of interest, so am attaching some pictures.

[David G4EBT]

I think the PCB would clean up nicely with care, even though the substrate is horrid SRBP of yesteryear, to which the copper had poor adherence. As to using the scan as a pattern to enable you to replicate the PCB, I think that would be problematical on a DIY basis due to the lack of contrast of the image between the copper and the SRBP substrate.

Due to forum limitations, the pic is of course a low definition thumbnail, but I've given it a go in Elements to see if the 'Paintbucket' tool will pour white into the substrate and black into the copper pads, and no - not for me it won't. The only thing I could see that could be done (on a DIY basis with limited software and skills), would be to laboriously draw in all the pads and tracks in black, and draw the background in white. (reversing the B&W for a negative mask). I've done that on a small portion of the LH side of the PCB, as depicted in the attached pic, but it would be very laborious to do the whole board, remembering of course that creating a mask is just the first stage.

Terry, VK5TM, is much higher up the food chain than I am, and might have something more elegant to suggest.

Hope that's of interest.

[Jolly 7]

Thanks David. I might give it a go over Christmas. To help me with editing in Photoshop Elements I am looking to get a proper graphics tablet for my Windows 8.1 machine. Trying to do anything fruitful with an ordinary keyboard and mouse takes forever. I do have a Medion PCB Graphics tablet, but is not compatible with Windows 8.1.
Terry has been most helpful with another of my PCBs, so will no doubt be contacting him again in the near future.

[Radio1950]

Jolly,

thanks for starting an excellent discussion.

[kevinaston1]

As Dr Nick says, vector drawing is far superior.

Attached is a bit of the Thorn 3500 circuit (moderators, please remove this if there is a violation). The page is 18 inches by 12 and the file size is 127kb. Resolution? magnify it up to the limit of Acrobat which is 6400% - still crystal clear.

Regards

Kevin

[Jolly 7]

Originally Posted by Radio1950

Jolly,

thanks for starting an excellent discussion.
.

My pleasure. Happy to know this thread has generated some interest.

[Terry_VK5TM]

Just to give you and idea of what can be done, here is the other pcb Jolly referred to.

Note that the pic of the original has been mirrored so it appears as if looking through the pcb.

As Kevin mentioned, a vector format (SVG) will be much better if you are going to have a go.

Inkscape is a free program that will do it (once you work out how to drive it).