Make your own PCBs form A to Z
using Eagle Layout Editor + Photoshop
author: Hlias Hliadis
(page 3/3)

Exposure

If everything is printer out correctly on the test page print it out to a transparency using a Laser printer to the maximum resolution, cut the PCBs from transparency and keep then in a good condition until development. Your hands must be clear and you must don't tough it on top of traces.

 

You will need:

• Exposure chamber with UV light 300W

• 2 pieces of glass 30x30cm , thickness 0.5mm

• Peridrol (from local pharmacy shop)

• sparse Hydrochloric acid (form Super Market, used in baths)

• Toboflo (from Super Market)

• Plastic gloves

• UV Light sensitive boards

• Protective Laquer spray

• Drill with drill bits form 0,5mm to 3mm

• 2 plastic basins

The exposure chamber isn't difficult to construct, it consists of a box (preferred from wood), with useful height 60cm width and depth 40cm and a door that apply the best way to the box. In a hole to the roof you attach the lamp. The lamp fitting must be from porcelain to prevent melting of it. You can also attach rubber bottom to the box to eliminate vibes that affect lamp's life.

UV lamps emit ultraviolet radiation and are more expensive than regular ones, among this they need a warm up time of approximately 5 minutes to have best performance, so before put the PCB inside let it warm up. ATTENTION: Never look directly to the lamp, it is VERY hazardous for the eyes.

The 2 pieces of glass needed to support the PCB and transparency contact in the exposure chamber, use one piece as base and put the photosensitive PCB on top of it with the copper side up, then put the transparency with the printed side face the copper side of the PCB  and then put the second piece of glass on top of all. Use adhesive tape to seal them all together.

All this must be done in a room with no bright lights and make fast movements, because photosensitive boards from the time we remove the protective layer are exposed to any light and you may experience problems if let it to much time exposed.

After lamp warm up, put the two pieces of glass along with PCB and transparency, without looking or touching the lamp, close the door and let it exposed 15 minutes, exploit this time frame to find a cartoon box (p.e form shoes) to put the PCB in after exposure and heat (DON'T BOIL) 1 litter of water.

When 15 minutes passes  turn off the lamp and take off the pieces of glasses. Take the exposed PCB and put it inside the cartoon box until the time to etch bath comes.

As you see above I don't use the "classic" enchants (sodium hydroxide  – trichoride ) because they are dangerous for environment and human and they are also difficult to deposit them later .You are not allowed to depose them in environment or to the WC but give them to a chemical laboratory. The chemicals I propose can be deposed to drainage   (NOT depose them to environment either), apart from that housewives use them for house cleaning.

The etching procedure must take place to a well ventilated place or to open space with the use of plastic gloves and the best attention you can have (have in mind that Hydrochloric acid is an ACID) as you have to manage chemicals!

To one of the two basins put the heated water and 3 spoons of Tuboflo, (you must not use this spool again for food!) mix the solution well until Tuboflo is dissolved.

To the second basin all the Hydrochloric acid bottle (450ml) solution and a little Peridrol (around 2 caps of a common water bottle). Mix them well.

Now put the board to the first basin with the water and Tuboflo and move it until the traces show up (in around 1-3 minutes). When the traces can be seen clearly remove the board and wash it out with pure water into the bath.

After that  place the board to the second basin with  Hydrochloric acid and Peridrol and move it around until the copper is removed from the exposed areas of the board, (around 15-20 minutes), if the copper removal isn't finished in the time add up 1-2 doses of Peridrol. When etching finished you must have the PCB almost ready with the copped traces only left. You must check the board to see if there are undesirably areas with copper , if you notice that put the board to the solution again until they are completely removed, then wash the board with water and wipe it with toilet paper.

Deposit chemicals to the toilet and wash them also with warm water and soap.

When PCB becomes dry, spay it with the lacquer spray following the manufactures instructions.

When lacquer dries it's time to drill the holes, you will need an electric drill to open the components holes.

If you want a more professional look to your pcb you can do silk screening of components placement, but this is made only to special laboratories and there is an additional cost for it.

At this point the guide has come to it's finish, I hope it helped you a bit to make your own PCBs. Remember, don't be disappointed if the first try fail, patience and persistence  are the "tools" to achieve your goals. Good luck.

 
Hliadis Hlias - vilias@yahoo.com
Electrician - Electronics Engineer
Technician - Industrial Installations
 

The names Elektor, Adobe, Photoshop CS, Acrobat, and Eagle are registered trademarks.

•  www.elektor.gr elektor magazine in Greece

• www.elektor-electronics.co.uk  elektor magazine in UK

• www.adobe.com  Adobe site for Photoshop and Acrobat

• www.cadsoft.de Eagle site

 This article is dedicated to my parents and all loving persons and friends.

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