Today I bought a new presensitized PCB and transparencies made by MG chemicals to use with my black and white brother lazer printer for creating PCBs.

I decided to print using the thick paper option. The printer took some time to print and here I thought the toner will apply nicely, but to my dismay, there were still some faint black spots even though I chose in eagle to print straight black. I also have toner saving mode turned to off and the resolution set to 1200dpi.

I then tried again with thin paper option since that makes the printer print faster and maybe then less heat will go on the transparency.

In both tests, I am sad to see that the image shrank a bit. I tried lining up a 40-pin DIP IC to where the 40-pin DIP goes in circuit and only the first few holes were acceptable. the rest were about 1 to 2mm off.

I also read somewhere that transparencies shrink in lazer printers because of the heat but since I bought premium ones from MG chemicals which are supposed to be heat-stabilized, I don't understand why I continue to get slightly shrinked images on transparency.

In software I ensured a 1:1 scale print and I don't want to fudge with the scaling as that wastes paper.

Now it seems my only two options are to go to a print shop to get it done or throw the "new" printer in the garbage and order an "old" one with a transparency setting in software.

But are there any other answers before I resort to going to a print shop because I spent a few hundred for nothing now it seems.

 

I prefer to laser print and then iron on to the copper. I find the smooth surfaced photo quality paper is quite good enough and irons onto the copper easily.

 

What is the format of the file containing your PCB layout? PDF? JPG? Or something else!

 

eagle brd. then again I wonder if specifying small margins is the problem

 

So you are using Ragle to print the board layout. A .brd file is not an image; it is a data file used by the Eagle program

It is interesting that you mentioned small margins. All printers have a minimum margin, because they physically cannot print to the edge. Depending on what format or tool is used to print, how they handle this limitation may be different.

One way that programs deal with this is to shrink the output to make the specified margins fit between the constrained margins. Which may be what's happening to you.

So try increasing the margins.

 

When I used to print or pen-plot artwork, I would always put a long line in each of the X and Y directions with a known length. Print it then measure the lines with precision calipers then adjust the printer calibration to print the exact sizes. Even a reported '1:1' scale can be off quite a bit for PCB use until it's calibrated. You can also use the lines to check the printed artwork before transfer to the sensitized board.

If you don't have room for the lines outside the board, place a few components such that you can measure accurately e.g. pin 1 of U1 is exactly 8.000" from pin 7 of U5 and in the same line.. that sort of thing.

 

I print from Eagle on to transparencies and print borders have no affect on image scaling.

I have printed on inkjet and laser transparencies with a laser printer and have never had an issue with them shrinking while printing or being used to transfer toner.

I use inkjet transparencies for toner transfer because I can monitor the transfer process, can apply heat only where needed, and the coating allows them to release toner better than paper. Not all types/brands of transparencies will work.

 

I print from Eagle on to transparencies and print borders have no affect on image scaling.

I have printed on inkjet and laser transparencies with a laser printer and have never had an issue with them shrinking while printing or being used to transfer toner.

I use inkjet transparencies for toner transfer because I can monitor the transfer process, can apply heat only where needed, and the coating allows them to release toner better than paper. Not all types/brands of transparencies will work.

Ok, thanks for your input.

I am thinking from the OS level perspective and HAVE had problems with image scale being dependent on borders.

So, I suggested the experiment to confirm the effect.

 

1) Make sure shrink to fit is turned off. Make sure the paper size is correct (A4 v Letter).
2) confirm it's right on paper and adjust magnification accordingly
3) make sure the toner side is against the board.
4) Loose the transparency film and switch to a translucent polyester paper.

 

I dont have a shrink to fit option. I'm gonna use a store to do the printing then I'll order a used printer on ebay without the new options