Laser Etching PCB: A Comprehensive Guide for Beginners

Introduction

Laser etching PCB
Laser etching PCB

 

Laser etching is widely used in the advanced world of technology manufacturing.  It is widely used in the production of printed circuit boards (PCBs) that serve as the brain for the majority of consumer electronic devices. Laser etching facilitates the efficient interconnection of various electronic components. Technological progress has simplified key facets of PCB production; it holds a crucial position in the overall PCB manufacturing process.

Making Laser Etching Circuit Boards in Electronics

Laser technology has the ability to swiftly etch codes within seconds while protecting the surrounding material against distortion. Moreover, laser etching plays a critical role in transmitting information during the production of integrated circuits. This process is preferred and used due to its accurate results.  It is important to note that using lasers for etching printed circuit boards should follow the exact method used for this process.

Steps of PCB etching

Gather the things you will need for your project

  • A 10W laser printer: A 10W laser is used to draw the circuit design on a standard copper-clad printed circuit board by using a printer.
  • A copper PCB: The copper PCB has copper on one or both sides, enabling electrical conductivity, while the phenolic material inside it does not conduct electricity. By selectively removing sections of the copper coating, pathways can be created to connect components and form the printed circuit board.
  • A black-colored plastic paint: To coat the printed circuit board thoroughly, a dense layer of paint is required, and a paintbrush proves to be a useful tool for this purpose.
  • Ferric chloride: Ferric chloride, available in a salt form, needs to be mixed with water before application. This solution can potentially harm the copper by detaching it from its phenolic base.
  • A mask: Wearing a mask, only the exposed areas of the plate not covered by the mask will be affected by the solution.
  • Sandpaper: Finally, any remaining traces of the mask on the board should be removed, and this can be accomplished easily using sandpaper.
  • Gloves: Using gloves can help in preventing the exposure of skin to hazardous chemicals that are used in the etching process.

Prepping the PCB

The copper surface of the PCB is scrubbed to remove copper residue
The copper surface of the PCB is scrubbed to remove copper residue.

 

This step is very important because it is helpful in removing any residue left on the copper surface. if any copper residue is left on the surface by chance, it could disturb the proper attachment of the photoresist film, causing the circuit traces to detach.

Cut your PCB into the required size:

Cut your PCB to the required size. It can be achieved by cutting it with a sharp blade and then breaking it by using a hacksaw.

Use a steel wool to scrub the copper surface:

Usually, steel wool is used to thoroughly scrub the copper surface, ensuring the removal of all oxidation from the surface of copper. After the steel wool treatment, you should have a gleaming copper board.

Use acetone or alcohol to clean the circuit board with a cloth:

Now, utilize acetone or alcohol and a clean cloth to wipe the entire board. Do not touch any part with uncovered hands.

Cut a photo-resist film slightly larger than your PCB:

Trim a part of a photoresist film. It should be bigger than your printed circuit board. Try to do this in a dark room. It helps in preventing unnecessary chemical reactions that can happen due to exposure to light.

Place a photoresist film on your PCB:

Remove the protective plastic backing and then affix it to the printed circuit board. Heat the board to ensure the film sticks properly. When the board is heated enough, take a soft cloth and gently press the film on the board. Make sure to eliminate any air bubbles.

PCB Designing & Mask Creating Process

Craft your PCB design with any CAD software

PCB being designed by the CAD Software
PCB being designed by the CAD Software.

 

After crafting your printed circuit board design with your preferred CAD software, you can save it as an SVG file for import into graphic design software. Various layers can be exported, including bottom view, top view, silk, mask, and more. You can also select between normal and mirrored formats for each layer. To execute the described process, the application of a mask to the printed circuit board is essential.

Apply a mask of plastic spray paint on the PCB

Apply a mask of black paint on the PCB before exposing it to the laser beam
Apply a mask of black paint on the PCB before exposing it to the laser beam.

 

The regions of the board covered by the mask will remain free from oxidation and remain preserved on the final circuit board. If the copper surface is not covered by the mask, it will be exposed to ferric chloride leading to corrosion and their removal from the circuit board after etching. Apply the paint coating to the board and employ a laser engraver to remove specific portions of the PCB.

Apply a thin layer of spray paint:

The first step to start the PCB fabrication involves the paint coating on the board. A black, water-based PVA paint is the preferred choice; it is susceptible to quick laser burning. The selection of dark paint is preferred because white paint reflects the laser and reduces its effectiveness. The water-based paint is preferred for use because it is easily removed from the copper board once the etching process is complete.

Evenly apply a single layer of paint:

To start the PCB production procedure, it is important to evenly apply a single layer of paint on the surface of the PCB. Avoid any gaps or imperfections that could potentially harm the traces or result in unwanted contact points. The use of dark water-based paint is important due to its easy removal from the board after the copper has been etched. It is mandatory to dry the paint before going to the next step.

Invert the mask colors using two separate software programs

The mask colors are generated and inverted by using two separate software programs for essentially switching black and white pixels. This can be done by these two programs:

  • Inkscape: This software is used to convert SVG to PNG. It can also be used to transform the design into a black-and-white image if it was initially exported from the CAD software in colored format.
  • Gimp: This software is used to change the mask’s color by converting white pixels to black pixels. The image is imported into the laser cutter software for printing on the plate’s surface.

Modify your laser printer

A laser printer
A laser printer.

 

Control the laser by modulating it with a PWM (Pulse Width Modulation) signal. Most online guides suggest using the part cooling fan output for this purpose. It requires a logic converter to step down the 12/24V voltage to the 5V as needed by the laser module. The laser demands minimal power for PCB exposure, the 12V power source from the cooling tower fan is usually utilized.

Engravings of Laser

When the mask has completely dried, use a laser cutter to eliminate the unnecessary sections of the mask. The laser engraving procedure can be time-consuming for larger boards. The quick option is to engrave only the essential areas by using a CAD software tool that fills in the copper areas that don’t require removal. This practice minimizes the quantity of paint to be burned off by the laser, as valuable time can be wasted on removing the paint from unnecessary areas that are not part of the circuit.

Submit the board into a PCB etchant

A PCB inserted in the etchant solution
A PCB inserted in the etchant solution
  • Take an etchant solution and place it in a plastic bowl.
  • Dip the PCB carefully in the etching solution with the copper requiring etching entirely covered and facing upward.
  • Swiftly, slide the mixture back and forth.
  • Leave the PCB in the solution until all the exposed copper is dissolved leaving only the copper under the resist layer.

Wash the etched PCB

Wash and clean the PCB with water or acetone
Wash and clean the PCB with water or acetone

 

Remove the leftover mask after the rust is finished. Use a brush & running water to wash the etched PCB. For a smoother finish, use sandpaper to clean the PCB. Sandpaper is a quick option and it makes the surface look shiny and smooth.

Drill holes for the components

Drill holes in the PCB
Drill holes in the PCB

 

Drill the required holes on the newly etched PCB and start the assembly process. Laser drilling is a quick option with full accuracy. Another option for drilling holes in the PCB is the usage of a drilling gun having different sizes of drilling bits. After drilling, components are assembled and soldered on the surface of the PCB.

Types Of Lasers PCB Etching Machines?

  • Fiber Laser
  • Ultra Violet Laser
  • CO2 Laser

 

Benefits of laser etching over the wet etching process

Laser etching has several advantages over the traditional wet etching process. It is preferred in industries related to electronics and their manufacturing. The key benefits of laser etching are given below:

  • Precision and Accuracy: Laser etching provides highly accurate results. It allows the creation of neat, measured, and exact details. We can not achieve this highest precision level by wet etching.
  • Minimal Material Waste: Laser etching does not require any contact with chemicals. In wet etching, chemicals are used to remove copper, leading to material waste and environmental concerns.
  • Environment friendly: Laser etching does not need any chemicals or solvents. It reduces the environmental impact. It also eliminates the need for hazardous waste disposal.
  • Versatility: We can use laser etching for different materials. Wet etching is limited to some materials and the choice of chemical etchants.
  • Speed and Efficiency: Laser etching is a faster process for intricate or complex patterns.
  • Reduced Operator Exposure: Laser etching reduces the risk of exposure to hazardous chemicals and fumes that are associated with wet etching. Laser etching promotes workplace safety.
  • Less Tool Wear: Wet etching can lead to the corrosion of etching tools due to the use of chemicals. Laser etching equipment typically undergoes less wear and tear.
  • No Mask Requirement:  Laser etching does not require the usage of masks.
  • Less Maintenance: Laser etching requires less maintenance as compared to wet etching equipment.
  • Digital Control: Laser etching is highly flexible and can be controlled digitally. It is easy to use due to minor adjustments and ease of automation.
  • Prototyping and Small Runs: Laser etching is particularly useful for rapid prototyping and small production. It does not require expensive molds or tools.
  • Intricate Features: Laser etching can create unique features with high aspect ratios and complex geometries that can be very challenging with wet etching.

 

Safety precautions during the laser etching process

Things worn for safety during the process of PCB etching
Things worn for safety during the process of PCB etching.

 

Safety precautions are essential during the laser etching process. Some key safety measures are discussed below:

Eye Protection: Always wear laser safety glasses or goggles that are designed for the specific wavelength of the laser being used.

Protective Clothing: Wear proper clothing to cover exposed skin.

Ventilation: Perform laser etching in a well-ventilated area to remove any potentially harmful fumes created during the process.

Fire Precautions: Keep all firefighting equipment. Ensure that the etching area is free from flammable materials. Be prepared for potential fire risks because laser etching can produce heat.

Laser Beam: Do not place reflective objects in the path of the laser. The reason is that they can scatter the beam and pose a risk of unintended laser exposure.

Maintenance: Regularly maintain and inspect laser equipment to ensure its safe operation.

Personal Protective Equipment (PPE): Use appropriate PPE like gloves in addition to laser safety glasses while handling the materials or equipment during the etching process.

Laser Output Control: Ensure that laser power and settings are properly controlled and used as needed for the specific etching task.

Limit Direct Viewing: Avoid the direct viewing of the laser beam. Use remote viewing methods like, cameras, or computer screens to monitor the process.

Conclusion

The PCB etching utilizes laser technology and leads to the creation of the best-functioning PCBs. The laser marking technology plays an important role in ensuring flawless quality of the PCB. The expanding PCB market offers great opportunities for growth in the laser etching machine industry.

FAQs

How durable is laser etching?

Etching is a long-lasting and budget-friendly method for preparing PCBs. This process maintains their durability for approximately 5 to 10 years.

How accurate is laser etching?

Nowadays, very precise results are achieved with laser etching. The cut width can be exceptionally narrow at 0.0001 inch. The dimensional accuracy is 0.0005 inches.

How much material does laser etching remove?

It removes a minimum amount of material up to 0.001 inch.

How long does laser etching take?

It takes a few seconds to some minutes.

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