Laser Safety 101: Understanding and Mitigating Risks

Lasers are an essential tool in the manufacturing of printed circuit boards (PCBs), allowing for precise and efficient processing. However, lasers also pose a significant safety risk to individuals working in and around the laser environment. Accidental exposure to laser beams can cause severe eye injuries, burns, and other health hazards. It is, therefore, crucial that individuals working with and around lasers understand the potential risks and follow proper safety procedures to prevent accidents. This article provides a comprehensive overview of laser safety, including different types of lasers, potential injuries, and safety measures to prevent accidents. By following these guidelines, individuals can ensure a safer working environment and reduce the risk of injury when working with lasers.

In the surface mount technology (SMT) industry, lasers are commonly used in a variety of machines including:

  • Laser marking machines: used to apply permanent marks or codes on PCBs or components.
  • Laser drilling machines: used to drill precise holes in PCBs for vias and through-holes.
  • Laser cutting machines: used to cut PCBs or components to a specific shape or size.
  • Laser soldering machines: used for selective soldering of components onto a PCB.
  • Laser-based inspection systems: used to measure the height and coplanarity of components on a PCB, as well as to detect defects such as cracks, voids, and soldering problems.

Introduction to Laser Safety

What is a laser?

A laser is a device that emits a beam of light that is highly focused and coherent. The term “laser” stands for “Light Amplification by Stimulated Emission of Radiation.”

Lasers have many uses in different industries, including medicine, manufacturing, and research. In the manufacturing of PCBs, for example, lasers are used to drill holes, remove material, and mark the surface of the board.

Hazards and risks associated with lasers

Lasers pose several hazards and risks to workers. One of the most significant hazards is the potential for eye injuries, as the eye is highly sensitive to laser radiation. Lasers can also cause skin burns, and in some cases, fires and explosions.

Types of injuries

There are several types of injuries that can occur as a result of exposure to lasers. These include:

  • Thermal burns: These occur when the laser’s energy is absorbed by the skin and causes a burn.
  • Photochemical injuries: These occur when the laser’s energy triggers a chemical reaction in the skin that can lead to cell damage.
  • Photoablative injuries: These occur when the laser’s energy removes tissue from the skin’s surface.
  • Mechanical injuries: These occur when the laser’s energy causes physical damage to the skin, such as cuts or punctures.

Laser Classification and Warning Labels

Laser classification system:

Lasers are classified into different categories based on their potential hazards to humans and animals. The classification system is defined by the International Electrotechnical Commission (IEC) and the American National Standards Institute (ANSI).

  • Class 1: This class of lasers is safe under normal conditions of use, and does not pose a hazard to the eye or skin.
  • Class 2: This class of lasers emits visible light that can be harmful to the eye if directly viewed for an extended period of time. However, the eye’s natural aversion reflex will protect it from accidental exposure.
  • Class 3R: This class of lasers is considered a low to moderate hazard to the eye and skin, and should be handled with caution.
  • Class 3B: This class of lasers is a moderate to high hazard to the eye and skin, and should be handled with care. Direct or specular reflections are also hazardous.
  • Class 4: This class of lasers is the highest hazard class and can cause severe damage to the eye and skin. They can also be a fire hazard, and precautions must be taken to prevent ignition of flammable materials.

Warning labels:

All lasers must have warning labels that indicate the laser’s classification and potential hazards. The label should also provide information on the maximum power output, wavelength, and pulse duration of the laser.

Sample warning labels for different laser classifications:

  • Class 1: “No warning label required”
  • Class 2: “CAUTION: Laser radiation – do not stare into beam”
  • Class 3R: “DANGER: Laser radiation – avoid eye or skin exposure to direct or scattered radiation”
  • Class 3B: “DANGER: Laser radiation – avoid eye or skin exposure to direct or scattered radiation”
  • Class 4: “DANGER: Laser radiation – avoid eye or skin exposure to direct or scattered radiation. Laser radiation hazard to skin and materials. Risk of fire.”

It’s important to understand the laser classification system and warning labels to ensure that proper safety measures are taken when working with lasers.

Nominal Hazard Zone and Eye Structure

Nominal Hazard Zone (NHZ)

The Nominal Hazard Zone (NHZ) is the space around a laser where the level of laser radiation exceeds the Maximum Permissible Exposure (MPE) limit. It is important to know the NHZ to ensure that safety measures are taken to prevent accidental exposure to laser radiation.

Structure of the Eye

The eye is a complex and delicate organ that is vulnerable to injury from laser radiation. The main structures of the eye include the cornea, lens, iris, and retina.

  • Cornea: The cornea is the outermost layer of the eye and acts as a protective barrier against foreign objects. It is also the primary structure that refracts light entering the eye.
  • Lens: The lens is located behind the iris and is responsible for further focusing the light that enters the eye.
    Iris: The iris is the colored part of the eye and controls the amount of light that enters the eye by changing the size of the pupil.
  • Retina: The retina is the innermost layer of the eye and contains photoreceptor cells that convert light into electrical signals that are sent to the brain.

Potential for Accidental Exposure and Injury

Accidental exposure to laser radiation can cause damage to the eye, ranging from mild irritation to permanent vision loss. The severity of the injury depends on the power and duration of the laser radiation, the wavelength of the laser, and the location of the exposure on the eye. The cornea and the lens are the most vulnerable structures to laser radiation. If exposed to laser radiation, they can absorb the energy and cause damage to the retina. Damage to the retina can result in permanent vision loss.

Maximum Permissible Exposure and Safety Procedures

Maximum Permissible Exposure (MPE)

The MPE is the maximum amount of laser radiation that a person can be exposed to without experiencing any adverse effects. The MPE is determined by the laser’s wavelength, pulse duration, and other factors. The MPE is set by the American National Standards Institute (ANSI) and the International Electrotechnical Commission (IEC) and is expressed in units of power per unit area (W/cm²).

It is essential to follow MPE guidelines to avoid overexposure to laser radiation. Overexposure can cause permanent eye damage, skin burns, and other injuries.

Laser Safety Eyewear and Clothing

Laser safety eyewear and clothing are essential components of laser safety. The correct selection and use of laser safety eyewear and clothing are critical for protecting against laser radiation.

a. Optical Density

The optical density (OD) is the measure of a material’s ability to absorb laser radiation. Laser safety eyewear is rated by its OD, which is specific to the laser’s wavelength. The higher the OD, the more effective the eyewear is in blocking laser radiation.

b. Wavelength Dependencies

Laser safety eyewear is designed to block specific laser wavelengths. It is essential to choose eyewear that is appropriate for the laser being used.

c. Selection and Handling of Laser Safety Eyewear

When selecting laser safety eyewear, it is important to consider the laser’s wavelength and power output. Eyewear should fit properly and be comfortable to wear. It is essential to inspect eyewear regularly for scratches, cracks, and other damage that may reduce its effectiveness.

d. Laser Safety Clothing

Laser safety clothing, such as lab coats, gloves, and aprons, are designed to protect the skin from laser radiation. The clothing material should be appropriate for the laser’s wavelength and power output. Clothing should fit properly and be comfortable to wear.

Safety Procedures

a. Safety Procedures for Laser Safety Eyewear

When using laser safety eyewear, it is important to ensure that:

  • The eyewear is appropriate for the laser being used.
  • The eyewear is undamaged.
  • The eyewear is worn properly and fits snugly.
  • The eyewear is kept clean.

b. Safety Procedures for Laser Safety Clothing

When using laser safety clothing, it is important to ensure that:

  • The clothing is appropriate for the laser being used.
  • The clothing is undamaged.
  • The clothing is worn properly and fits snugly.
  • The clothing is kept clean.

In addition to laser safety eyewear and clothing, other safety procedures are essential to ensure safe laser use. These procedures include proper placement, lockout and tagout, barriers and traps, and handling of hazardous materials.

Correct Procedures for Placement and Hazardous Materials

Proper placement and handling of lasers are critical to ensuring the safety of individuals working in the laser environment.

Placement of Lasers

Lasers should be placed in areas where access is restricted to authorized personnel only. They should be positioned in a way that minimizes exposure to any potential hazards. Some of the factors to consider when placing lasers include:

  • Clearance distances: Laser workstations should have clearances around them to prevent accidental contact with the laser beam.
  • Reflective surfaces: Reflective surfaces, such as mirrors or metal surfaces, should be avoided in the laser work area as they can reflect the laser beam and cause unintended exposure.
  • Adequate ventilation: Adequate ventilation should be provided to prevent the buildup of hazardous fumes and particles.

Lockout and Tagout Procedures

Lockout and tagout procedures are important safety measures that should be followed when working with lasers. These procedures involve shutting down the laser, disconnecting it from its power source, and placing a lock and tag on the power source to prevent accidental startup. This ensures that the laser cannot be turned on without the knowledge of authorized personnel.

Barriers and Traps

Barriers and traps can be used to prevent accidental exposure to the laser beam. Barriers can be physical barriers or walls that block the laser beam from the surrounding area. Traps can be used to capture the laser beam and prevent it from escaping the laser work area.