Tonight's episode: Amateur Hour in the PCB Factory!
Earlier today the tinning chemicals showed up. Since I happened (coincidence, honest) to be out of work early, I popped down to the workshop to have a play, as one does. I've bought enough tinning powder to make 500mls of solution, but since it only lasts 6 months when made up, I chose to only make 50ml. Weighed exactly 9g of powder into 50ml of near-boiling water, per the instructions; let it cool somewhat, then dunk the board in & watch some YouTube videos while I waited. After about 20 mins I took it out; it was tinned, but quite dull in colour.
It did polish up a little bit with some cloths, but I had to take it too far, didn't I? I very VERY lightly ran it across a sanding sponge I have, which promptly removed most of the tin... So, back in the bath for another couple of Marty's Matchbox Restoration videos (recommended if you like watching ancient tiny metal cars being resurrected from near-destruction back to better-than-factory), I removed it again and gave it the obligatory cold & hot shower, per the instructions. This time, I just buffed it as best I could with paper towels - it looks OK. Not as shiny as I'd like, I might give it a touch of a polish with some polishing compound, I think I got some with my dremel. I'll do that later.
Next job - carefully measure the X/Y offsets of the first pad from the edge of the board. Stick board to bed. Mount 0.6mm drill (so I get to keep more of the pad this time). Using the milled slot, carefully set the drill height so it doesn't drill any more holes in the plastic baseboard.... (duuuh). Then, one careless Y-move and
SNAP! Bye-bye 0.6mm drill.
Undeterred, I used the 0.5mm drill anyway, results as per photo. I do have another 0.6mm drill somewhere, I think it's at home. If I can't find it, I think I'll re-drill the holes at 0.7mm, as the 0.5 looks a bit thin to take any component legs. Also, I'm not 100% sure I've drilled all the way through, and I don't want to move the board until I've made absolutely sure.
In the pic, I've stuck the board to a piece of scrap (a previous failed effort), using my aluminium fences to align it. It's not too bad, although the holes at the top of the board are slightly off-centre, probably because the board's not exactly square cut. Mea culpa, but that's what you get for having to cut all four sides by hand... I've had good results using a paper guillotine (the lever type) to cut circuit board, except it likes to move as you start the cut. In future, I'll probably stick the board to the cutter using double-sided tape, that way I should get a really good and dead-square cut. Not sure if it'll tear off the photoresist protective layer, though... some experimentation is required...
That's it for this week, I'll pick this up again on Saturday, which will hopefully involve finishing the re-drilling to the correct size, soldering the board up, and giving it a test run.
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