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Old 22nd Apr 2017, 12:31 pm   #9
David G4EBT
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Join Date: Feb 2003
Location: Cottingham, East Yorkshire, UK.
Posts: 5,737
Default Re: Anyone recommend one-off PCB layout service?

Not quite sure what it is that you wish to do Al, and I can't answer your specific question, but the following (wordy) notes might help a little:

Is it that you want an acetate mask from a hand-drawn sketch so that you can use a UV light box to expose a pre-sensitised board? If so, pre-sensitised boards (and UV lacquer), are invariably positive resist so it's a positive image that you need - not a negative. You can however get dry-print negative UV film which I've tried recently, which you bond to a plain piece of PCB by passing it through a laminator a couple of times. For that, your artwork needs to be negative. When exposed, all of the white (clear) part of the design will remain on the board, and all of the black areas will be washed off with the developer.

It's not clear to me whether your problem is preparing the artwork for the mask, or getting a one-off circuit board professionally manufactured to your design. If you just want to convert your 1:1 hand drawn sketch into a neat layout suitable for use as a PCB mask, you don't need to use PCB software for that. You can scan in your sketched design and save it in 'my pictures' or wherever, then you can use MS 'PAINT' (which is bundled with Windows) to clean up the layout. I usually do a 1:1 sketch and scan it to get the dimensions correct, then import it into PAINT and using the various drawing tools - lines, circles, rounded oblongs, bucket, paintbrush, eraser etc - to draw over the sketched lines. You can enlarge the design to get better clarity on the screen if you wish. In photo editing software such as Photoshop, you can re-size the image if it doesn't print out to the correct dimensions. (I usually used say an IC socket placed on the artwork to check that the size is correct).

In MS PAINT, if you want to reverse the image, in 'View' you select 'Rotate' then on the drop-down menu, left click on 'flip horizontal' then save the flipped image with a suitable name - 'reversed image' or whatever. The 'iron on' technique has gained popularity among those who have a laser printer but no UV light box. It requires that the design is 'flipped' or when etched, the PCB will be back to front! The technique - which I haven't tried - involves printing the design onto glossy paper torn from magazines then ironing the artwork onto the PCB, then soaking off the paper in warm water, leaving the toner on the PCB to act as a resist. It matters not that the paper has printers' ink on it - only the toner artwork will adhere to the PCB.

If you wish to convert a positive image to a negative one (to use with the UV dry film technique say), you first use the 'Select' tab, and using the cursor, pull the dotted lined box to encompass the whole image, then right click your mouse, go down the drop-down menu and select 'invert colour'. Everything that is black will now be white (clear when printed onto acetate), and everything that was white will become black, and hence, opaque when printed onto acetate.

I've attached three pics of a PCB I designed using MS 'PAINT' to make a little 555 IC tester as I had lots of 555s which I wanted to test. The first pic is a positive image, the second pic is the image reversed as described above ('flip image horizontal'), the third pic is the same image converted to a negative by using the 'invert colour' tab.

To draw the image I just use the 'draw a line' facility, then for circular pads used the 'circle' tab, and to draw IC pads, used the 'rounded oblong' tab. If at any time you make a mistake, you can use the undo button. There are several line widths you can select, and if you have a large area to fill in, you can use the 'paint bucket' and fill in that area. If for example, you have a solid circle, an IC pad or whatever, and wish to put a hole in the centre, you just select white as a colour instead of black, select the paintbrush and width of the hole, then apply the paintbrush to the centre of the pad. If you haven't quit centred the 'hole' correctly, just cluck the 'undo' arrow and re-do the hole.

As to making a decent mask that will stand up to UV, home printers vary in their ability to print onto acetate. Some have a 'transparency setting but in the days of Powerpoint for presentations rather than OHPs, many printers no longer have that setting and produce poor acetates using normal OHP film.

Similarly in my experience, laser home printers and laser prints from copy shops produce poor acetates for use as PCB masks. Sure, people often say that you can use two or even three taped together and in pre-computer days I sometimes got away with that, but the best results I've obtained are by using 'micro-porous film' (not OHP acetates) from Crafty Computer Paper', but I've had to fool my Epson printer settings into producing dense lines up to the standard called for. Others claim that printing onto tracing paper (sometimes called vegetal paper' in other countries) produces an acceptable mask and that spraying it with WD40 will act as a 'transparentizer'.

I use PAINT in preference to software packages because those packages seem to have small pads and thing tracks, more suited to commercial PCB production than for DIY.
If I see artwork created with such packages which I wish to use, I import the image into PAINT and beef up the tracks and pads to my liking.

Under the 'View' tab, you can add or remove gridlines or a ruler for scaling.

All of this rigmarole might sound like quite a faff, but I find it much easier to use PAINT than using and of the PCB programs I've tried, but each to his own. I also find PAINT useful for creating front panels. The last two pics are of a PCB for a 'coil coverage test unit' that I designed, along with the front panel. Both the PCB and front panel were created using PAINT - the more complex CAD programs are just not in my skills portfolio and are way above my pay grade!

Hope that helps a bit Al, and has at least some relevance to your needs.

It will make more sense if read alongside PAINT on the screen, (for which there are countless tutorials on youtube).
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