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v1.3

Minor Versionm

by Daniel H Soong

Introduction

This guide will teach you how to use the ProMask and ProLegend kit to add the green solder mask layer silkscreen graphics to your PCB.

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

    • You should use scaling of 1:1.0021 or 1.0025 instead of 1:1 for a better result

  2. 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. Make sure that the scaling is letter size paper, and 1 to 1 scaling.  You can change the margins to 150mm vertical to save ink for silkscreen
    • 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.

    • Make sure that the scaling is letter size paper, and 1 to 1 scaling. You can change the margins to 150mm vertical to save ink for silkscreen

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

    • You should use scaling of 1:1.0021 or 1.0025 instead of 1:1 for a better result

    • 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.

  3. 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
    • 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

    • The main method of solder mas is using the green/white goo/paste in tubs iin the closet.

    • This tub is the Green goo, or the actual solder mask. It has a very pungent smell so try to not inhale too much fumes. It is highly viscous so be careful when measuring. 8 grams of the green goo is required for one side of a PCB

    • This tub is the white goo. It is the activator that solidifies and chemically cures the green goo and turns it into solder mask. It is very paste like and a semi-solid. 2 grams are required to activate the 8 grams of green goo

    • The general ratio is 8 grams green goo to 2 grams white goo to get a nice solder mask. This is about a 4:1 ratio.

  4. 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).
    • 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.

    • IF using the two jars of activator and mask, it should be 8 grams of the green goo to 2 grams of the white goo.

    • Use the curing oven and run the ProMask-PD profile

  5. 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 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

  6. 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.
    • 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.

  7. 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
    • 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

  8. Rinse the board off with water
  9. Neutralize the developer solution with LPKF Conditioner before pouring it down the drain.
    • 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.

Finish Line

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Jimmy Nolan

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