ProMask/ProLegend

Solder mask is what makes circuit boards green and is used to protect the board and make soldering easier.

Silkscreen is used to embed white text on the surface of the circuit board.

Both of these layers must be applied to the surface of the PCB and selectively cured using a printed transparency sheet under a UV lamp.

Solder mask and silkscreen are added after the vias are drilled/plated and the top/bottom traces on the PCB are milled.

Open your project in CircuitPro and in the CAM view make only the top and bottom solder mask layers of your design visible and drag them apart.

Select File->Print and make sure the paper comes from Manual.

You can choose Print preview to make sure the print will turn out correctly.

Click Print and insert a transparency sheet into the front of the printer located next to the computer.

Repeat the procedure for the silkscreen layers but check Invert before printing.

The solder mask/silkscreen kits are kept in a brown LPKF box in one of the tall white cabinets.

One part contains a roller, a paintbrush, handles for holding the board, and popsicle sticks

The other contains tips for the roller, gloves, a beaker, and a bottle

Retrieve one packet each of ProMask components A/B, ProLegend components A/B, LPKF Developer, and LPKF Conditioner.

They are located in the fridge outside the AFL

Place a plastic glove over the roller bin and mix ProMask compounds A and B with a popsicle stick (ProLegend A and B if you're doing silkscreen).

It may take several minutes until they are fully mixed

Use the roller to apply the solution on both the front and the back of the PCB.

Once a thick layer of solder mask/silkscreen is present on both sides of the PCB it's time to cure it.

Place the PCB in the reflow oven and choose the ProMask-PD profile

Follow the guide for the reflow oven here.

Once it is finished and cooled, line up and tape the appropriate cut out solder mask /silkscreen transparency sheet

Be sure not to mix up the top and bottom layer transparencies

Open the UV lamp

Place the PCB under the glass and latch it shut

Close the lid, set exposure to 60 seconds for solder mask and 120 seconds for silkscreen, and push start.

Remember to cure both sides.

Add the developer power to 1000mL of water at 40-50°C

The water does not need to be this warm for the silkscreen so you can reuse the same developer solution for both processes.

Pour the solution into the bin provided with the kit and scrub off the uncured solder mask/silkscreen with the paintbrush

Rinse the board off with water

Place the board in the reflow oven and choose ProMask-PC

Follow the guide for the reflow oven here.

Repeat the procedure starting from step 3 for the silkscreen if necessary.

Neutralize the developer solution with LPKF Conditioner before pouring it down the drain.

Throw away the used plastic gloves, popsicle sticks, rollers, and transparency sheets.

Pack up the kits and store the box away in the cabinet.