Does anyone know where I can find published figures for the precision of laser-jet printers? It's not something that normally gets mentioned in reviews.
I make my own boards, and often have difficulty aligning the two sheets of acetate before exposing the board to UV. I've discovered the reason is that my printer (a Samsung ML-2525W) very slightly distorts each image it prints, making it very hard to simultaneously align all four corners of a arduino mega sized board.
I discovered this by printing out sheets of A4 graph paper, and despite being perfect to the naked eye, I measured the grid with a micrometer and found errors of up to .4mm over a distance of 100mm. Not a big error, but enough to make it hard to achieve perfect alignment. It wouldn't be so bad if the printer made exactly the same percentage error on each print, but the amount of error seems to vary from sheet to sheet.
I know I could work around this just be reducing the precision of my circuits designs (currently I use 1mm vias with a 0.5mm drill) but I'd prefer just to find a better printer, any suggestions?
I would recommend researching if your printer can perform a reverse line feed. It is likely more accurate to tell the printer to move in reverse to align before the second printing than putting the paper in again.
Are these consumer grade or business grade printers? Generally (but not always) - you get what you pay for. Alternatively, older business grade machines (like the old HP LaserJets) might (?) be more accurate due to better quality construction.
While you may have already tried this - have you played with the settings to see how that varied things? Perhaps a higher or lower DPI or other factors might make a difference (though whether such changes would affect the ability to use the printer for toner transfer is another issue).
Ultimately - toner transfer was never meant to allow a hobbyist to go down below a certain level; you may be simply asking for something that you can't get without spending money on a printer specifically designed for accurate toner transfer (whether such printers exist is another matter, though - I believe there are direct-print-on-pcb printers - both laser and ink-jet).
You may just need to alter your process - perhaps you could print things larger (or however you wish to reduce the error) - and then optically reduce the image size? Or maybe your PCB material could be covered in some kind of dark etch-resist, which can then be ablated away using a laser engraver machine?
While I usually make my own PCB's using the toner transfer method... at some point I admit that what I'm working on warrants using a service either due to complexity, size or the end result quality I'm aiming for. A service like OSHpark, for example.
X-direction will likely be very precise, Y-direction not precise as this relies on friction
drive to the paper from rubber rollers that wear. Print a test-graticule and measure with
digital calipers?
One possible source of variability could be the temperature reached in the printer which could be different between one print and the next. I don't know what the thermal stability is like but I would guess that a few tens of degrees difference could be noticeable.
I use an HP inkjet printer in the photo setting to get a solid black printing on Xerox acetate sheets with a slight roughness on the printing side. I've just measured an acetate I produced about two months ago and a 114 mm radius measures 0.1 mm over in both X and Y directions. It was done using Draftsight software with no adjustment to the printing scale.
Are these consumer grade or business grade printers?
I've done the tests with several different laser-jets, from my own cheap home-office model to an expensive multi-featured office one. similar results with all of them
It seems most reviews of printer look at artistic abilities, rather than engineering precision!
Print a test-graticule and measure with digital calipers?
That's basically what I've done, as per my original post.
The basic problem is that with a 1mm via and a 0.5mm drill, a mismatch between layers of about 1/2 mm means that a hole drilled accurately on one side of the board will come out through the edge of the via on the other side.
How do you know the problem is with the printer hardware and not with the printer driver software interpreting your drawing and making some assumptions about where to make a dot on paper?
In other words, have you tried an equivalent printer from another manufacturer? Can you take the file to a different computer with a HP printer, perhaps?
Fulliautomatix:
yes - with similar results (see last post)
I guess that doesn't surprise me.
Sorry, was just handed a Christmas card from Digikey and had to play the CD of classical music.
I recall people trying to use the original Xerox machines to make copies of drawings. The optics were good enough for text copying, but not scale drawings. Several years ago I replaced the burner pot in my pellet stove and the new pot had different mounting screw placements. There was a page in the documentation with a pattern to be cut out and used to spot the new mounting holes. I dutifully cut it out, marked and drilled the new holes. Couldn't get the new pot to mount. The drawing was quite a few % smaller than the pot rim. They had either copied the original drawing or had printed a bunch of copies and didn't actually verify the result.
I have seen many construction articles for printed circuit boards using a printer to make a mask to make a printed circuit board, but I don't think I have ever seen a project done that way for a double sided board.
The suggestion to use a real board manufacturer should be followed.
One would use a laserjet on magazine cover or on plastic sheet so that the plastic laserjet toner can be transferred to the board as a resist material for etching.
Inkjet ink doesn't transfer like that.
CrossRoads:
One would use a laserjet on magazine cover or on plastic sheet so that the plastic laserjet toner can be transferred to the board as a resist material for etching.
Inkjet ink doesn't transfer like that.
Agreed, but for precision I had assumed that he was using a photo resist process although he didn't say.
Inkjet also has the advantage of dense black in large areas such as ground plane where laser printers can be troublesome.
Just to clarify, I print onto acetate to make a UV photomask. I've tried the toner transfer method but have never had much success with it (most of my designs are pretty detailed and fiddly)
I guess the real problem is just that I'm trying to push the component density too high for DIY pcbs. I could probably solve most of my problems just by using thicker tracks, greater clearances and bigger vias.
I have tried a inkjet printer many years ago, but switched to laserjets on the understanding that they were better for this sort of thing.
I've toyed with the idea of sending out my pcbs for professional manufacture, but they tend to not be cheap unless you order a dozen, and I've never built more than one version of a board before I've moved onto the Mrk II version.
They way I currently work I can have a bright idea in the morning, design the board in the morning, build it over lunch and be playing with the prototype in the afternoon. I can't do that if I've got to send the board out.
Fulliautomatix:
I have tried a inkjet printer many years ago, but switched to laserjets on the understanding that they were better for this sort of thing.
They have improved, especially if you stick to the photo setting. I recently etched a brass clock dial with 0.25 mm lines quite successfully using an £50 HP Deskjet to make the photo masks. When etched the lines came out a little over 0.3 mm due to the depth of etching required for wax filling.
Some people have had luck printing inkjet pigment inks from Epson printers directly onto copper boards, baking, and then etching. Either Epson pigmented OEM inks, or aftermarket.
My Yahoogroup about it:
One of the list members made sort of a crude collection of hints and tips culled from the group:
You don't even need to modify your printer, if it takes a CD tray. You can either make a CD sized adapter, or buy an ID printing tray and cut your boards to that size, or modify the tray to fit a larger PCB.