[SARATOGA] User Manual

Once you have built it, you are ready to make PCBs! For blank PCBs, I recommend ones with a presensitised positive photoresist (you can find them on eBay). You will also need some universal developer (again found on eBay), some ferric chloride (can be found on Amazon), some latex disposable gloves (can be found on Machine Mart), eye protection goggles (can be found on Machine Mart), two plastic trays (you can find etching trays on Amazon), some acetone (Amazon) and a Stanley knife, cutting mat, black pen and set square (on Amazon again).

PCB Artwork

Once you have your PCB artwork prepared in a Computer-Aided Design (CAD) package such as gEDA pcb, export it as black and white (traces are black, empty board is white). Print it, using 1:1 size (not resized or scaled). A laser printer with printer transparency film is what I use (be sure not to turn on any toner save functions). Then you can trim the transparency film to a size that fits the lightbox using those slidey cutter things (I can't remember the name for them).

Preparing the PCB

If your blank PCB that you ordered is too big for your artwork, you can cut it with a guillotine (being very careful of your fingers/hands!), or with this method that I use: mark the line to be scored with a black pen and set square. Then (using the drawn line and set square as a guide) score the line with a Stanley knife and cutting mat (about 50 cuts per line per side seems to do the trick). I recommend a headroom of about 2mm when marking, as the scoring and snapping is relatively inaccurate. Then use the edge of a table as the middle of the snapping pivoting point, apply force to both ends and it should snap quite cleanly! (Be sure not to remove the UV blocking adhesive yet).

Preparing The Developer

I like to prepare the developer before I expose the PCB (gives it time to cool down to room temperature). Put on some latex gloves and mix one satchet (about 25g) with 500ml of hot water (about 70 degrees C, you can use a water-proof thermometer, like the ones used for aquariums, or just guess, the water will be too hot to touch for long). If the manufacturer's recommended amounts are different, then I recommend you follow their instructions. Pour the hot water in a plastic tray, and add the universal developer and stir (I use an old plastic chopstick for this) until it has all dissolved. It's best to do this at a sink. If you are using very hot water (such as from a kettle or water boiler), it's best to pour the water in a spare mug (like the ones used for tea or coffee) first, letting it cool down to 70 degrees C, and then pouring it into the plastic tray. Very hot water (about 100 degrees C) can melt plastic!

Exposure

Peel off the UV blocking tape and align the PCB to the artwork and LEDs of the lightbox (be sure to handle the PCB by its edges so you don't leave fingerprints and oil on the copper). In a dark room, switch on the lightbox and let it expose the PCB to UV light (about 18 to 20 seconds is OK, you might need more or less). Don't look directly at the LEDs, or better yet, wear some UV blocking glasses!

Developing

Place the blank exposed PCB in the plastic tray that has your cooled developer solution in. Let it develop for about half a minute. Then rinse the PCB in cold water.

Etching

Being sure that you are wearing disposable gloves and not wearing your Sunday best, pour some ferric chloride in a separate plastic tray, enough to cover the PCB. Then submerge the PCB in this liquid and then rock the tray gently back and forth (or side to side). Be careful not to get the ferric chloride on your skin or in your eyes. If contact occurs, rinse with clean water. Check now and again to see if the exposed copper has all disappeared. When all that is left is the copper traces, rinse the PCB in cold water. Again, it's best to do this at a sink. Once you have finished with the ferric chloride, you can use a funnel to pour it into a plastic bottle for later usage. Throwing away ferric chloride after only using it once is very wasteful! Obviously, keep such chemicals away from children.

Stripping The Photoresist

Using the soft, non-abrasive side of a sponge/scourer, use the acetone to strip the developed photoresist. You will know when it is stripped because what will be left is a shiny copper trace underneath the dull photoresist. When it is all stripped, rinse the PCB in cold water.

What Next?

The PCB may be processed enough as it is, but there is more you can do to it, such as tin plating, plated through holes and solder masking (you can find tutorials on the Internet about these methods, I don't do it so I can't comment). You can use a Dremel and Dremel Workstation (converts your Dremel to a pillar drill) to drill the holes in the PCB, then you can solder in the components! I use a Dremel 3000 with a compatible multi-tool chuck for 1mm and 1.5mm drill bits for example, and a compatible Dremel Workstation to act as a pillar drill conversion for drilling the holes (remember to wear eye protection goggles when drilling, and glasses are not eye protection!) If you have long hair, remember to tie it back. Also, be sure not to pour the ferric chloride down the sink, it will wreck metal sink pipes! Be sure to dispose of all chemicals responsibly.