Laser Micro Drilling and Micro Perforation: Techniques and Applications

One of the most industrialized applications in the field of laser technology is microperforation or Microdrilling. It's not something that is noticeable, but many of the objects we routinely use are micro-perforated to make our life a little easier.

Applications of laser microperforation are growing every day and, with the constant improvement of equipment and techniques, this trend is expected to continue in the coming years.

Let's see in more detail what it is, what laser microperforation techniques exist, their applications and their advantages.

What is Laser Microperforation?

Laser microperforation consists of making very small through holes in various sheets, films or plates, using the energy provided by a laser source as a method of perforation.

These holes can be up to a few microns in diameter, but industrial applications usually use holes over 50 microns in diameter, equivalent to the average thickness of a human hair.

Laser technology is based on the accumulation of focused energy in a very small point.

This accumulation is so powerful that it can vaporize materials such as polymers, metals and even ceramics, and at the same time it is so controllable, that it allows micro-perforations of excellent dimensional quality without negatively affecting the surrounding material.

Types of Laser Microdrilling

Not all laser micro-perforations are the same. The technique used will vary according to the diameter of the hole, the thickness of the layer to be drilled, the material and the geometry of the hole we want to obtain.

The most common types of microperforations are the following:

• Single-pulse microperforation: when the thickness of the layer to be perforated is small, a laser of the appropriate power and spot diameter can be used to pass through the material in a single laser pulse. In this way a perforation with the desired characteristics is obtained, obtaining high productivity and perforation speed.
• Percussion microperforation: when the thickness of the layer is high, the material absorbs little energy or the laser does not have enough power to perforate the layer in a single pulse, percussion is used. This method consists of firing multiple pulses at the same point to gradually remove the material from the surface until it is completely pierced.
• Clambering: this method is suitable for large micro-perforations, which are larger than the diameter of the laser spot. This is also referred to as conventional drilling or trepanning. In these cases, the diameter of the hole is enlarged by moving the laser beam to achieve perforation. It would be like trying to cut out a circle by making lots of holes. This is the technique also used for conventional laser cutting.

Impacts on materials

It must be said that all these techniques affect the way in which the micro-perforation is made, but they do not affect the internal geometry of the holes, which in themselves are conical.

This is because the laser focuses on a point in space, but as it moves away from that point, the beam increases in diameter. Due to this phenomenon, the front face on which the laser engraves usually creates a hole with a slightly larger diameter than the back face.

For most applications this difference is not relevant, but for applications where this is an important factor, special optical equipment can be used which lengthens the focal point to obtain cylindrical rather than conical holes.

How to configure a project

First we need to define the diameter and spacing of the micro-perforations we need for our application.

Depending on this diameter and the substrate material, the required laser type, power and optics will be selected.

Once selected, it is necessary to perform an optimization of the laser parameters (power, pulse, frequency, separation, etc.).

A tip is to perform a scanning electron microscopy (SEM) inspection of the result to check the quality of the microperforations.

Applications of Laser Microdrilling

The applications of this type of technique are very varied and cover almost all sectors, from the typically more industrial ones such as automotive or aeronautics, to the medical and food sectors, passing through consumer goods, defense and fashion sector.

Let's see below some specific examples of applications that are used depending on the type of material:

• Polymers: the use of laser microperforation in plastic films is widespread in the packaging sector to create openings that favor the preservation of products, while in the food sector it is used to extend the life of perishable products such as fruit and vegetables, generating controlled atmospheres . One of the less common applications, however, is the micro-perforation of rigid plastic, which can be used to create invisible points of light that become visible when light passes through them.
• Metal: the main applications in the most industrial sectors are the construction of injectors for turbines or automobiles, and in the healthcare sector the construction of medical equipment, where high precision and very small dimensions are required. However, the applications are many, such as the replacement of conventional processes with presses.

Advantages

Laser microperforation has multiple advantages, here we summarize some of them:

• Minimum hole size, obtainable only with this technique, given the different optical configurations available.
• It does not require additional materials and is environmentally friendly, as it does not generate waste.
• Ability to punch any material if the right laser is chosen.
• Possibility of making holes very close to each other, with great precision and without sagging of the surrounding material.
• High drilling speed, easy application for sequential processes without the need to stop the pieces.

Check at the following link applications and machines for Laser Micromachining