It happens that you find interesting pieces at local fairies. In this case I bought some LCD displays for 1€ each.
Since I wanted to connect them to a breadboard to make prototypes or test some features or codes, I needed to solder many wires to the tiny LCD contacts, or making a PCB to connect those contacts to larger pins. I went for the second way and I managed to be very accurate to avoid short circuits between the thin pads, I'll show you the entire process.
Step 1: References
With a fast research I discovered that the LCDs are very common 16 characters 2 lines MC1602X serie display. They are also compatible with the Hitachi HD44780 driver, so I can easily control them with Arduino libraries.
The 15 pins have a spacing of 1/20 inch, half the distance between common through-hole components and breadboards holes. To know the pins labels I've found this datasheet by Everbouchet/Wayton in internet, which is more likely referring this exact display module.
Step 2: Pcb Layout
In Diptrace I created two custom pad arrays and I connected them with regular tracks. I tried to keep the bigger the pads I could, because I noticed that sometimes very little pads detached from the board during solder process or due to a mechanical stress of the component. For the same reason I drew the pads with an elliptical shape. Free space between little pads is very thin, to be exact is about 0.2 mm, and it will probably be unsuitable for higher current, but it works good in this projects where LCD needs very low currents.
I attach the pdf file with PCB layout and also the file for Diptrace, so you can modify it if needed.
Step 3: Copper Board
Print the layout on a glossy paper with a laser printer (turn off toner saving option).
It's crucial find the right paper type, make more prints and check that edges are very sharp.
Set up the copper board cutting it with right size, then clean it very hard with a metal sponge and soap. This will make a good base to attach the toner with heat.
You can find more about ironing technique here.
Step 4: Transferring Traces
Use now the iron to transfer the traces on the copper board. Set the iron at 90-100% power, put the printed sheet in contact with the board, then push the head of the hot iron over the back of the sheet, only a bit to make it adhere with the copper side. Then insert the board with sheet on the upper side into a dish cloth, so to avoid ruin the iron, and pass more and more times especially on the board edges.
When you're satisfied dip it into water, wait a few minutes, and begin to scratch away the paper. To do that don't pull the edges, but scratch the center of the sheet, trying to not cut the toner traces. Use a soft toothbrush to remove entirely the paper from the board.
Step 5: Check
Now you have to check carefully each trace. If you're not satisfied take a metal sponge and scratch away the paper, clean the board with soap, and transfer with iron another layout, or cut another copper board to engrave both of them, as I did.
I had a problem with the transfer of the vector layout in a graphic software, it resulted into a pixelated image. Try always to print the original vector image.
Step 6: Etching
This is the second board, with toner traces already transferred, this time with a better print (the one I attached on this instructable of course). As you notice, the trace are very good, and no pixelation is visible.
Dip the pcb in acid (usually ferric chloride) and shake a bit the liquid to speed up the process. After about half an hour the pcb will be ready. The pcb comes out yellow, because the acid left this colour on everything it touch. It's easily removed with water, but beware to not dirty your clothes because acid consumes fabric.
Read more about etching technique here.
Step 7: Clean From Toner
PCB is etched now. Clean it from toner with the metal sponge, and check minutely the copper layout with the help of a magnifying glass.
Step 8: Drill
Time to drill the holes. Unfortunately my narrow bit is only 0.8mm and in this case a smaller bit would be better. I suggest to try with a 0.6 mm. However I was able to not cut the pads in half.
Step 9: Check Again
If the pads touch one each other, you can scratch the space between them with a cutter, so to remove the copper in excess. Test all the traces with a multimeter, you should obtain than no trace is connected with the other ones.
Step 10: Solder One..
You can now solder the pins row in the bigger holes. To do that raise the plastic holder and reveal a bigger space to solder. When pins are soldered you can lower the holder to hide the tin.
Step 11: Attach
Apply some double tape on the rear of the display board to attach the pcb. When this is in position you can solder the thin pins on it.
Step 12: ...solder Two
Pins are soldered now. You can refine the pin heads with a file, so to check again there are no connections between traces.
Step 13: Ready for the Prototype!
You can now insert your new LCD display into a breadboard to connect it on Arduino for your custom watch or any other project!