The MicroSlice V2 Aurum | a Gold Mini Laser Cutter & Engraver.

The MicroSlice story began back in 2013 with an entry into the Instructables 2013 RadioShack Microcontroller Contest. The MicroSlice V1 won the Grand Prize and set the foundations for a successful Kickstarter Campaign a few months later.

It has been an exciting past year and the MicroSlice has evolved from a small 50mm x 50mm workspace into a machine with four times the space at 100mm x 100mm. The simple screw-drives have been replaced with precision stepper motors which use belts & pulleys and the Gantry now moves smoothly on linear bearings.

To mark the occasion I have built a one-off special edition of the MicroSlice V2 where the Upped-Deck has been gilded in 24ct gold and I have customised just about every aspect of the machine. I have called it the MicroSlice Aurum.

I'll be using this Instructable to share some of the new skills I have learnt over the past year and I'll hopefully inspire some of you to push yourselves with your own creations and ideas :)

Steps

1 | Parts & Tools - A comprehensive list of everything you'll need.

2 | Laser Cutting - Cutting the parts from sheet plywood.

3 | Prepping The Plywood - Removing any scorch marks and smoothing the surfaces.

4 | Dyeing The Plywood - Adding some colour to the wood.

5 | Assembly - Putting the parts together.

6 - 8 | Gilding - Applying gold leaf to the Upper-Deck & Cutting Table.

9 | Wiring - Installing the electronics, wires and connectors.

10 | Belts & Pulleys - Finalizing the mechanics.

11 | Lasers - Prepping the Cutting-Head.

12 | Setting Up The Software - Using custom firmware and a little help from another Instructable (

CNC Laser for Printing Images and Engraving - Shapeoko 2 based).

13 | Calibration - Setting up the Cutting-Head.

14 | Engraving Images - Etch photographs on to wood.

15 | Making PCBs - Produce detailed PCBs using a positive UV Photoresist.

Please vote for the MicroSlice at the top of the page :)

Step 1: Parts & Tools.

MicroSlice | Download the attached MicroSlice_v2.5.zip file.

Sanding| 120 Grit Sandpaper - Rigid Sanding Block.

Dyeing | 25g of spirit based powder dye - 500ml Methylated Spirits - Suitable basin for dyeing in - Somewhere to dry the dyed parts - Cleaning Cloth.

Assembly | PVA Glue - Mini Clamps - Weights - The MicroSlice Build Manual - A suitable work space.

Gilding |25 Sheet Book of 24ct Superior Transfer Gold Leaf - Handover 1-2 Hr. Oil-based Size - Liberon Fontenay Base, Red, 30ml - Humbrol Matt Black Enamel Paint - 5ml Syringe - 0.4mm Needle - Brushes - White Spirit - 600 Grit Sandpaper.

Electronics & Wiring | The MicroSlice Complete Kit comes with all the cables, wires, electronics and connectors you'll need to build a MicroSlice. However for this one-off special edition I have replaced all the screws, cables and spacers with black versions and replaced all the black heat-shrink with their yellow equivalent.

For a complete list of all the required components please download the Plans & Parts List from The LittleBox Company website.

To wire the MicroSlice you'll need | A Soldering Iron & Solder - A Multimeter - Needle Nose Pliers - Wire Cutters - A Sharpe Knife - Screw Drivers - The MicroSlice Build Manual - A suitable work space.

You'll also need a USB A to B cable and a 12v PSU capable of at least 3 Amps.

PCB Prototyping | Ferric Chloride Etching Solution - UV Photo-resist coated copper PCBs - Photo-Resist Developer - Tin Plating Crystals - ISO Cleaner.

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Step 2: Laser Cut the Plywood Parts.

The MicroSlice is Open Hardware and you can download a complete set of plans from thelittlebox.co. The download also includes a comprehensive build manual, and a parts list.

Don't worry if you don't have your own Laser Cutter, you can purchase a set of Laser-Cut Parts, or a complete MicroSlice Kit including all the electronics from thelittlebo.co webshop.

The Laser Cutter used is an HPC Laser LS6090 Pro fitted with an 80 watt Long-Life CO² Laser Tube, I upgraded from the Chinese eBay bought 50watt machine. The process takes a little over 1 hour to run. The MicroSlice is cut from 3mm Laser-Grade Birch Plywood. The MicroSlice is available in a wide range of coloured Acrylic, but for this version we'll need to use plywood.

Step 3: Sanding the Surfaces.

The Laser Cutter can leave scorch marks on the wood. To remove these marks and to brighten up the plywood we'll need to sand the faces smooth.

I have attached some 120 grit sandpaper using double-sided tape to a sheet of tempered glass. The glass was reclaimed from an old flatbed scanner.

I also have a sanding block. Try to use a block which is made from rigid plastic and not one made from rubber or cork. Using a flexible sanding block can cause the edges to round over.

With the sanding complete I sorted the parts by size in preparation for the next step, dyeing.

Step 4: Dyeing the Parts.

The dyed parts will need to be hung out to dry. The first thing I did was to get a selection of paperclips, open the clips out and use them to hook the smaller pieces. The parts which couldn't be hooked on I stuck to pins. I put up some rails in the Laser Cutter where I could leave the parts up to air.

The dye is a spirit based powder dye. If we were to use a water based dye it would effect the plywood and loosen the glue used to bond it together.

I have chosen to use White Spirits as the solvent for the dye, however the manufacturers recommend Methylated Spirits.

I'll be using a cheap washing up basin bought from the pound shop to do the dyeing in. Check the parts fit in the bowl before you do anything else.

Then begin by emptying the powder into a suitable bowl.

Next add in the spirits, I had a 25g bag of dye which is suitable for around 500ml of spirit. Give it a good stir.

I started with the big bits first. Agitate the spirits over the part (tip the basin up and down a bit). I soaked each part for about 5 minutes constantly moving the basin during that time.

While dyeing the larger parts it became apparent that the smaller parts were going to be an issue and would be hard to retrieve from the dye. My solution was to use some wire mesh. I have a roll of the stuff which I rescued from the bin knowing it would be of use someday. The smaller parts were enclosed in the wire mesh and dyed together.

The parts were left to dry for an hour and the dyeing process was repeated to give a strong yellow colour. They were then left to dry over the weekend.

I notice that after returning after the weekend that the parts still had some dried dye powder on them. To remove the residue each part was wiped down with a dry cloth.

Next we can begin putting it together.

Step 5: Assembly.

I'm using reclaimed tempered glass sheet for the building surface. They are very strong, perfectly flat and the glue won't stick to them.

The parts are held flat using 250g lead ingots, and some reclaimed stepper motors. I'm using Mini Clamps to hold it all together while the glue drys.

The glue I've used is white PVA.

It is important to keep the assembly flat while building. If the parts warp it could effect the movement of the Gantry when it comes time to complete the build. I have been extra careful to wipe off any excess glue before it has the chance to dry.

Take your time, check each part fits together before applying glue and allow the glue to dry for an hour or two before moving to the next stage.

Step 6: Gilding the Cutting Table.

There are two types of Gold Leaf; Loose leaf and Transfer.

Loose Leaf is exactly as it sounds, loose inside the book. You'll need a Gilder's cushion and a Gilder's Knife to cut it. To apply the gold will require a Gilder's Tip made from Squirrel hair.

Transfer Leaf is attached to a sheet of tissue paper. It can be cut with scissors, and is applied directly to the surface to be gilded. It works very well with flat surfaces but isn't so good with curved or carved areas.

The Laser-Cut parts are all flat faced. I chose a book with 25 sheets of 24ct gold leaf. I also bought a 7 sheet book of loose leaf just in case, but it turned out I didn't need to use it.

This is my first try at gilding and I wanted to do some testing before I committed myself to gilding some of the rare dyed parts. I have cut two extra brackets and I will use those to experiment with.

I planned to coat only one of the two brackets with the Fontenay Base, apply the Gold Size and see if, and how well, the gold would stick. It would also give me the opportunity to figure out how best to apply the gold.

The base is applied and allowed to dry for 2 - 3 hours. It is then sanded smooth with 600 grit sandpaper and then the Gold Size is used. The size is left for a further hour before gilding can take place.

The wood is porous and on the bracket without the base the Gold Size was absorbed which meant that the gold wouldn't stick. The bracket with the base worked perfectly.

The gold leaf was cut to size using normal kitchen scissors. Make sure the blades are clean or they can ruin the gold leaf.

The Cutting Table is made from two layers of 3mm plwyood glued together. The Aurum text is cut-out from the top layer and I wanted to see some gold through the gaps.

The lower layer was marked where the gold would need to be applied.

The space was painted with red base, sanded, sized and then gilded. The two layers were then glued together with PVA and left to dry between two sheet of tempered glass. It was weighted down to keep it flat while the glue set.

Next the honeycomb cutting area was covered with red base and left to dry before being sanded smooth.

Because of the large area needed to be gilded I set a 1 hour timer when I began to paint the size on. I painted from the top down to the bottom. When it came time to apply the gold leaf I followed this same route so the size would be at the right tackiness for applying the leaf.

The timer kept track of how long the size had been drying at the start point. It took a little under an hour to properly apply size all over the cutting area which meant I had to begin applying leaf almost immediately after I finished applying the size. Luckily it took about an hour to gild the cutting area so the size was perfect all the way through the process.

I found that it was easier to use smaller sections of leaf rather that using larger bits. The gold leaf would crack and leave small gaps if the piece was too large. This wasn't such a problem if when applying the leaf to larger areas, but with the small honeycomb lattice it was.

I used my finger to press the gold down onto the size. Make sure your finger doesn't touch the leaf and keep a sheet of transfer tissue paper between your finger and the gold. If you do get gaps or miss a small section it is possible to go back over it with more gold. Always try and use a piece of gold which is larger than the area you need to cover up, this will help avoid any gaps.

After the cutting area was fully gilded I used a soft brush to wipe off the excess gold.

Step 7: Gilding the Cutting-Head & the Upper-Deck.

I've stripped the Cutting-Head, applied base, sanded, sized and gilded the parts.

For the Upper-Deck I started on the four internal sides. Red base was painted to all four sides and allowed to dry. They were all sanded smooth. I decided to gild one side at a time applying size to one side before gilding and then repeating the process until all four were done. I did the same for the four external edges.

Step 8: Gilding the Upper Deck, Continued.

For the top of the Upper-Deck I wanted to do something a little different. I applied the red base as usual and left it to dry for two days.

Next I took a pot of Matt Black Enamel modeler's paint, sucked up 1ml into a plastic syringe and squirted it into a small mixing pot. To that I added 1ml of White Spirits. The mixture was stirred for a few minutes to thin the paint enough so it could be sucked back into the syringe.

Using a 0.4mm needle the paint was gently injected into the engraved areas on the top of the Upper-Deck. Any spillage is easily mopped up with a cotton bud. Try not to wipe the bud onto the base as it will remove it from the deck, just dab it into the spillage where it will soak it up. It doesn't matter if the red is stained a little black, the gold should cover it all up.

For the larger engraved areas I injected the paint twice allowing the paint to dry a little between coats. The idea for painting the engraved areas was borrowed from another MicroSlice Build.

I left the paint to dry for 24 hours before sanding and completing the gilding.

Step 9: Wiring.

No doubt you can see from the wiring schematic that this can be a complex cabling job, it is then further complicated by my decision to use all black ribbon cable!

The black ribbon cable I have chosen is 3M High Flex 16-Way, at £8.94 + V.A.T. it's not the cheapest cable around and I'll need 2 metres of the stuff. Anyway, I'm not looking to compromise.

The undersides of the Arduino & the PWM Laser Control Module both have soldered through-hole components poking out so the PCBs sit on nylon spacers. For this build I have bought and used some black ones.

The kit-supplied white nylon screws securing the 2 x EasyDrivers, the Arduino and the PWM Laser Control Module have also been swapped out for black ones.

I'm using some very attractive yellow Heat-Shrink to beautify the wiring.

While wiring the Upper-Deck I put down a clean white towel on the worktop to prevent any damage to the gilding.

Step 10: Belts & Pulleys.

The Stepper Motors drive 3mm GT2 belt via 15-tooth aluminium pulleys. At the end of each axis is a ball-raced 15-Tooth return pulley.

The belt is clamped to the movable parts so they'll move with the rotation of the Stepper Motors.

Step 11: The Laser Diode Module.

The Laser Diode Module has a 16mm anodised black case with integrated heat-sink, a screw-in clamp-nut and a 9mm 405nm coated 3-Element Glass Lens.

The PWM Laser Control Module comes with an NTC Thermistor and we'll be fitting that inside the case with the laser diode.

The diode I have chosen is a Blue Ray diode extracted from a BDR-S06J Sled. The diode is rated at 400mw - 600mw. This is the highest rated diode you can safely use with the MicroSlice.

When doing the wiring I added two extra cores for the NTC thermistor.

To help with the cooling the back of the case is filled with thermal compound.

Step 12: Software & Setup.

The MicroSlice uses GRBL for Motion Control.

GRBL is written specifically for use with the Arduino UNO R3.

The MicroSlice uses a modified version of GRBL. In this instance to be able to use the MicroSlice for engraving images we need to use a version of GRBL which is able to provide a PWM output for the Laser Control Module. I did plan on using the latest release GRBL 0.9g which supports PWM output via a variable spindle speed.

However during testing I found out that the movement planning function of GRBL does not allow for changes in spindle speeds while the machine is at the working feed rate and the cutting head is slowed while the operation is carried out. This meant that it was incredibly difficult to get a gradient in the engraving. In short the beam was either at full power, or off. Apparently this is a G-Code safety feature.

Things were not looking good for the new image engraving capabilities I had planned for the MicroSlice.....

....But, I was in an email conversation with the chaps over at PicEngrave.com, they had explained to me the problem with the PWM spindle function, they knew of someone who had enabled PWM on the Z-Axis (The Z-Axis is part of the movement planning and the feed rate is unaltered) and on top of that the person in question had written a First Prize Winning Instructable about it all | CNC Laser for Printing Images and Engraving - Shapeoko 2 based.

Perfect!

Using the modified GRBL with Laser Mode the MicroSlice is able to do both vector engraving and raster engraving.

So how can we make GRBL Laser Mode work with the MicroSlice?

Some weeks ago I had altered the MicroSlice designs to be able to fit a small SPDT slide-switch to the Lower-Deck. With this new version of GRBL it will be possible to swap between Vector & Raster modes with the flick of a switch.

We'll need to remove the Z-Axis from the homing cycle as the MicroSlice doesn't have a Z-Axis. We can do this by downloading the source code and editing a few lines in the config.h file.

You can learn how to edit the config.h file and remove the Z-Axis from the Software & Setup of the MicroSlice V1.

I have attached a pre-compiled version of the GRBL Laser Mode .HEX with the Z-Axis removed from the homing cycle. Do not download the pre-compiled .HEX from the V1 as it does not have Laser Mode.

Now we need to flash the HEX to the Arduino. I use XLoader as it is very simple to use.

With the Arduino flashed we can setup GRBL. You may need to install the Arduino IDE as it contains the USB drivers required by the UNO.

There are many G-Code senders and I prefer to use ZapMaker's GRBL Controller. It is cross-platform and so works on most OSes.

After downloading and installing the application open GRBL Controller, select the relevant COM port from the drop-down list, set the Baud Rate to 115200 and click Open. GRBL Controller will attempt to connect with GRBL.

If Grbl Controller can establish a connection to GRBL you will be presented with some text in the messages box; on the screen should be Grbl0.8laser. Then there will be a load of $ values. These values are the defaults for GRBL.

I have edited the source code and compiled GRBL with the default setting for the MicroSlice, it should all be ready to go, but we'll need to a do few checks first.

Firstly | Unlock GRBL with $X, or open the Advanced tab and click the Unlock Grbl button, go back to the Axis Control tab when finished.

2 | Check that the Step Size drop-down is at 10, then click one of the direction arrows. The MicroSlice should move in the direction of the arrow. If this doesn't happen and it goes the other way you will need to turn around the plug from the relevant motor where it connects to the EadyDriver.

3 | Click the arrow again to make sure it moves in the right direction.

4 | Repeat with the other Axis.

5 | To execute the homing sequence and check that the end-stops work correctly type $H into the command box. The cutting-head should move towards the lower left corner and come to a stop. There is a video of the homing sequence here | YouTube. If this doesn't work you will need to trouble shoot the fault.

6 | Finally we can check that Laser Mode enables correctly. Type $L1 into the command box and press enter. If it works a message will show in the window telling you so. To disable it again type $L0.

Step 13: Calibrating the Laser.

You will need a Multimeter for this step.

The Laser Control Module (LCM) is capable of managing all wavelengths from UV to IR with a current up to 1000mw. Before we can use the MicroSlice the LCM must be setup for the diode you wish to use. The BDR-S06J is rated for 400mw to 600mw at 4.8v.

Check that the MicroSlice is unplugged from both the USB & PSU cables.

1 | Using a small-tipped screwdriver turn both potentiometers counterclockwise until you hear a click, this can be anywhere up to 14 full rotations.

2 | Check the Laser Module is plugged in correctly and if possible put something under the laser to stop any stray beams.

3 | Connect the PSU and USB cable.

4 | Load GRBL Controller and connect to the MicroSlice.

5 | Put on your Safety Glasses.

6 | Put GRBL in Laser Mode with $L1.

7 | Into the command box type Z254. This will set the laser output PWM to the maximum 5v setting the LCM at full power.

8 | Using your Multimeter measure the voltage differential between the positive and negative wires going to the Laser Module. The first time I measured it was at 0.90v

9 | Using a smalled-tipped screwdriver slowly rotate the gain/bias potentiometer about 1/4 of a turn clockwise.

10 | Measure the voltage again, if the voltage has not increased repeat the previous step.

11 | Continue to turn the potentiometer until the Multimeter gives a reading of 4.8v (check the specification for your diode).

12 | Into the command box in GRBL Controller input $L0. This will turn off the Laser Module.

13 | Disconnect the Laser Module.

You will need to make an adapter as the next step requires the use of the Mutlimeter's current metering function. The Multimeter will need to be inline with the power to the Laser Module to be able to read the current.

14 | With the Multimeter correctly wired into the circuit input $L1 into the GRBL Command box.

15 | Set the PWM to maximum by typing in Z254.

I'm going to set the current at 280mA, which according to the datasheet is a little over 400mw.

16 | Turn the gain potentiometer clockwise until the Multimeter gives a reading of 0.28A.

17 | When the current is set at the correct level reduce the PWM to 0v with Z0.

18 | Disable Laser Mode, $L0.

Step 14: Engraving Images.

To generate G-Code for the MicroSlice I will be using PicLaser Lite from picengrave.com They have a full-function demo version for download, it generates water-marks in your images which can be removed by registering the product.

PicLaser Lite works with 8 - 24bit Bitmap image files (BMP). 1700px X 1700px will make a 80mm x 80mm wide image for use with the MicroSlice.

To begin | Start PicLaser Lite.

1 | Click the Select File icon in the top left to load an image.

2 | We'll need to change the settings to generate a correctly formatted file. Click the Change Settings Icon at the top.

3 | Click on Feed Rate and enter 200 - Set the Pixel Resolution to 0.0500mm - The Max.Laser Value to 254 - The Min. Laser Value to 0 - The Laser Off Command is Z0 - The Laser Control Command is Z - Uncheck Engrave Outline - Leave the No. Passes at 1 - Make sure GRBL is selected - Choose either a Horizontal, Vertical or Left-45° tool path, I prefer the Left-45° setting - Set the File Extension to nc - Choose your File Directory and then click Save Settings.

4 | To read the file into PLL click the Load File icon at the top. Depending on the file size this can take a minute or two.

5 | Click Make G-Code, this too can take a few minutes to run.

6 | Click Save G-Code, a box will appear.

7 | Name the file and click OK. There is no need to enter a file extension.

8 | Wait a few minutes while the file is written to disk.

9 | Once the save has finished click the End Program icon to exit.

Next | Start GRBL Controller.

1 | Ensure your MicroSlice is powered on and that it is connected to your PC.

2 | Check the Baud Rate is set to 115200.

3 | Click Open to connect to your MicroSlice.

4 | If your MicroSlice is in an Alarm Lock mode open the Advanced tab and click Unlock or perform a homing sequence with the $H command.

5 | Put GRBL into Laser Mode with $L1.

I have a 100mm X 100mm Plywood blank to engrave the image onto. I have sanded the surface to prepare it before use. We know the image to engrave is 80mm x 63mm and I'd like the image centred on the blank.

6 | Put on your Safety Glasses.

7 | Guesstimate where the starting point will be on the plywood blank.

8 | Enter Z254 into the command box, enter Z0 in a second or two later. This will turn the laser on and off and leave a small dot on the plywood blank.

9 | Using a ruler measure the location of the dot and adjust the position of the blank so the image will be centred. Repeat until you have it in the right position.

10 | Click Choose File. Browse to the .nc file previously created with PicLaser Lite and load it into GRBL Controller. It will take a minute or two depending on the file size.

11 | Click Begin.

It took around 3 hours to engrave the full image. All the settings can be changed an toyed around with to increase the speed and power of the engraving. You can also increase the resolution of the photo with the aim of producing a higher quality engraving.

The yellowing of the plywood comes from the smoke generated by the engraving. I'll have to experiment to see is using a slow air-speed fan will stop or reduce the staining.

Attached is the G-Code I used to engrave the photo of the Stratos. It will expand to 12mb when uncompressed.

Step 15: Making PCBs.

The 405nm Blue diodes that the MicroSlice uses are able to active the UV Photo-resist on coated blank PCBs, this means that you can make detailed PCBs with the MicroSlice.

I've made a simple Instructables themed circuit to demonstrate the basic principles of PCB prototyping with the MicroSlice.

There are two variations of UV Photo-resist; Positive & Negative. We'll be using a Positive UV Resist for this demonstration. For an in depth explanation of UV Photo-resists check the Wikipedia page at http://en.wikipedia.org/wiki/Photoresist

The Positive photo-resist reacts to the UV light, the developer solution will dissolve the exposed coating and reveal the copper underneath. The exposed copper is then etched away with Ferric Chloride.

We'll need to make an image of the circuit we want which can then be imported into Piclaser lite to generate the G-Code for GRBL. Because we are using a positive resist we'll need to make a negative image of the circuit we want to create. To do this I drew the circuit as you would normally using black areas for the tracks and pads.

I did have to play with the image size to get it where I wanted it. With a pixel resolution of 0.05mm in PicLaser lite an image of 1000 x 1000 pixels equates to 50mm x 50mm. You'll need to take that into consideration when drawing your circuit.

Once the circuit is completed the image is simply inverted to swap the black for white and the white for black. The image needs to be saved as a BMP file and imported into PicLaser Lite.

With the image imported into PicLaser Lite we'll need to alter the settings for creating a circuit. I'm using the lower powered 200mw blue diode, we don't want to burn the UV coating off. I have the speed set at 500mm/min, powered is restricted to 100 and the resolution is at 0.05.

The UV Photo-resist on the PCBs is protected by a black film. The film needs to be removed before being exposed to the laser. You will also need to create a darkroom for the MicroSlice to work in otherwise the resist will be exposed to the ambient UV light and render the PCB useless. I used a cardboard box and cut out a viewing hole at the top and covered it with a flap.

I am using PicSender to control the MicroSlice as ZapMaker's Grbl Controller and other Java based programs are unable to handle the larger file sizes.

It is important to disable Position Feedback otherwise the MicroSlice will not run smoothly, this will effect the quality of the PCB.

While the MicroSlice is running the G-Code for the circuit we can prepare the chemicals used to complete the circuit.

The Chemicals used to develop and process the PCB are dangerous and can cause serious harm if they are not handled correctly. Please read and follow the safety instructions provided with the chemicals.

The developer comes as crystals which need to be dissolved in water. I have measured ~6.3g to make 250ml of solution.

The Ferric Chloride is also available as crystals, however I bought a bottle of liquid etching solution.

The Tin plating solution is a two-part mix which needs to be prepared an hour or so before you want to use it. Tin plating the PCB is not necessary but to give your PCB a corrosion resistant coating and a professional look I highly recommend it.

I have each of the prepared chemicals in numbered and labelled plastic containers ready for use.

When the MicroSlice has finished its work you should be able to see a slightly darker pattern of the circuit on the PCB. The first thing we need to do is develop the UV coating, to do this leave the PCB in the developer solution for a minute or so. You'll notice the circuit starts to appear as the developer reacts with the solution. Once it has finished developing immediately rinse it off with plenty of water.

Next is the Ferric Chloride to remove the exposed copper. I have pre-filled a sink with 2-3cm (1") of warm water and put the container with the etching solution into the sink. The heat will help quicken the etching process. The time it takes to work depends on many things including the temperature, thickness of the copper and the strength of the solution. In this instance I had to wait for a little over 15 minutes before I was happy the copper had all been dissolved. Remember to rinse off the PCB.

The remaining photo-resist on the circuit which was not activated by the laser is removed with Isopropyl alcohol. I sprayed some onto a cloth and gently wiped the PCB clean.

Finally we are going to tin-plate the copper. Place the PCB into the Tin Plating solution and wait. I left it for around 5 minutes to get a nice thick layer. Rinse off the board when you're done and dry with a suitable cloth.

The PCB is now ready for it's components; a CR2023 battery holder, a switch and an LED.

The final photo is a close-up shot of the etched and plated copper.