Wednesday, 23 April 2014

More boards for hand-soldering

The PHP development is still taking up a large slice of time, especially now we're integrating it with some jQuery frameworks - it's so easy to put a dot in the wrong place or forget one of those silly $-signs, and knacker the whole thing up!

But we've managed to free up a few hours this week to do some more board etching.
As we've got some working hardware for our space-shooty game we're also getting a bit of interest about a more generic system, which could be re-purposed for many different game types.

At the end of our space-game-update, we showed one of these generic board game sections - a 6x8 grid which can be connected to other, similar pieces, to make more regular shaped playing surfaces. So a football pitch, for example, could be created by arranging six of these board sections in a 3x2 arrangement, giving a massive 12 x 24 square playing area.

But before we started to get too excited, we needed to make a few more of these boards. As ever, this meant a trip to BuildBrighton and another late night!

The board layout was loaded into the newly-refurbished (i.e. properly-working) laser cutter....

....and etching began. It takes about 15 minutes to etch the mask for each 200mm x 150mm board

Once the paint mask has been etched off, the board is given a wipe over with some white spirit (not acetone - don't ever use acetone to do this!)

This takes only a few seconds, but is a really important step. Looking at the sponge, there's of black residue taken off the board. Without wiping it down with white sprits, this residue stays on the copper, and inhibits the ferric chloride during etching

During etching, you can sometimes see "streaks" on the copper as it is etched away. These are where some of the residue may remain, even after wiping with white spirit. We found that boards this big benefit from being removed from the ferric, and a sponge applied to wipe the copper tracks during etching. Often this lifts yet more residue that has collected on the board, and ensures a speedy and accurate etch.

After etching, all traces of exposed copper are removed. Using the paper-based copper panels from JPR Electronics, it's quite easy to see when etching is complete (and where it needs a little more time to finish off any little bridges between traces). Some copper clad board is a funny orange colour, which can make it difficult to see when etching is properly complete. These JPR boards are a brilliant which when etched, making it much easier to see when you're done!

With the board etched and cleaned, it's time to get that paint-mask off:

This is where acetone is really handy. You can scrub with a brillo pad (we usually do this for small-sized boards) but we found that acetone and a pan scouring sponge got rid of the paint really quickly. One thing to note is that synthetic sponges don't like acetone very much and disintegrate at an alarming rate!

With the copper boards etched and cut down to size (we make all our boards over-sized because we can't always line them up perfectly in the laser cutter) we then laser-cut some mdf to sit over the top. The holes in the mdf line up with where we have soldered our SMT hall sensors (and 1206 resistors) in place.

The last part of production is to place a plastic-coated card on the top.
Unlike the space-shooty game, we've not designed any artwork for these board sections. The idea is that - because they use a contactless method of sensing where the playing pieces are - they can be dis-assembled and re-used for other games, by simply placing a different playing surface graphic over the top. It should even be possible to use modelling equipment such as flocking and fine grit to glue on top of an assembled set of boards, for a more permanent, realistic-looking playing surface.

We now have six of these boards etched and lids cut and prepared for them. The next few evenings are likely to be spent hand-soldering a load of SMT hall sensors: six boards, with 48 sensors on each is nearly three hundred components! Maybe it's time to try to convince Steve that a cnc pick-n-place is a good idea now!

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