Application of Flat-Top Laser Beams in the Field of Laser Soldering Processing What is a Flat-Top Laser Beam

What is a Flat-Top Laser Beam

Comparison of Gaussian Beams and Flat-top Beams

A flat-top laser beam refers to a beam with a uniform intensity profile within a specific beam shape, dropping sharply at the edges. Unlike the Gaussian beam profile of most laser beams, where the width of the Gaussian spot (above the process threshold) is proportional to energy, the flat-top laser beam profile is characterized by almost no dependence between energy and the spot size above the threshold. This makes the flat-top beam profile highly desirable in many industrial laser applications.

Applications of Flat-Top Beam Profiles

Flat-top beam profiles are widely used in many laser applications to enhance performance and achieve sharp edges on processed materials. These applications include:

Laser Lift-Off and Debonding – A laser process used in the flat-panel industry to separate wafers from thicker carrier wafers. This process typically employs high-intensity ultraviolet lasers, which require extremely high uniformity and sharply defined edges. Both linear and square/rectangular flat-top beam shapers can be used in this process, depending on the system configuration.

Metal Interconnection Scribing – Commonly applied in the solar cell industry, flat-top laser beam profiles are used to create sharp edges during scribing, ensuring consistent performance of interconnects or electrodes.

Wafer Inspection – Flat-top beam profiles are critical in wafer inspection applications, where uniform brightness enables reliable defect detection. Linear flat-top beams are often employed in such scenarios.

Precision Laser Welding – When welding photosensitive materials such as polymers or when sealing battery cells using laser welding, flat-top laser beams are utilized to improve weld strength and achieve better contact angles.

Advantages of Using Flat-top Laser Beams

For a given process threshold energy, the flat-top spot maintains nearly the same size even as the pulse energy increases. This provides greater processing flexibility when working with different materials or thicknesses using the same laser machine.

Laser energy is utilized optimally—less energy is wasted below the process threshold.  

The heat-affected zone (HAZ) is reduced, as less energy is required to achieve the same processing result. This leads to the formation of sharp and clean edge in the treated area.

Songsheng Opto-Electric Coaxial Temperature Measurement Vision Square/Linear Spot-Welding Head and Beam Profile

The Songsheng Opto-Electric coaxial temperature measurement vision square/linear spot laser welding head utilizes advanced optical shaping technology to generate a flat-top beam at the focus. It incorporates a compound lens structure that effectively eliminates focusing issues such as halos and rings caused by single-lens laser focusing. Options include D80 and SMA-905 interfaces, making it suitable for fiber-coupled semiconductor and YAG laser welding systems. An optional temperature measurement module is available. The energy distribution within the spot is highly uniform, making it ideal for welding irregularly shaped pads.

It should be noted that the specific application methods and effectiveness of flat-top beams in laser soldering are influenced by factors such as the particular laser welding system and the materials being processed. Therefore, practical applications require optimization and adjustment based on actual conditions. In summary, flat-top beams offer higher power density, superior beam quality, increased welding speed, better adaptability, and a reduced heat-affected zone in laser welding, making them better suited to meet production demands.