Laser Soldering has Become a Crucial Part of Automated Production in the 3C Electronics Industry ​

Laser soldering is a type of precision laser welding process. Due t the low melting point of tin, which typically liquefies at around 230°C, it exhibits high plasticity at high temperatures. Upon cooling and solidifying, it thoroughly penetrates and tightly bonds, making it suitable as a connecting medium and filler material between different materials.

Particularly in modern 3C electronics manufacturing, both chip-level packaging and board-level assembly frequently rely on tin-based alloy fillers for soldering. Hence, the saying: "Tin connects everything."

Two Methods of Laser Soldering

Laser soldering encompasses various techniques, with the most common being laser solder paste welding and laser solder wire welding, each suited for different soldering scenarios.

Laser Solder Paste Welding

Image: Square spot welding & finished flexible PCB solder paste joint

Laser solder paste welding involves first preparing a solder paste composed of tin, flux, and flow agents. The paste is applied to the soldering area, and a laser beam is used to heat and melt it, bonding with the materials to be joined before solidifying into a solder joint. However, if the heating is uneven, the solder paste may form tiny particles called solder balls, which can splatter and adhere to the interior of electronic devices, posing safety risks. Therefore, it is essential to use solder paste with an optimized composition while also requiring precise control over the semiconductor laser’s power and the industrial control system.

Due to these considerations, laser solder paste welding is typically applied in contexts not involving complex circuits. Examples include terminal connections, antenna base soldering, shield can soldering, and SMT component soldering.

Laser Soldering Wire Welding

Image: Finished soldering joint of circuit component pins with wire feeding

Unlike laser solder paste welding, laser solder wire welding involves a wire feeding process. Before soldering begins, the product’s solder pads are preheated. An automatic wire feeding system then delivers solder wire (made of tin alloy or pure tin) to the solder pad area. A laser beam irradiates and melts the wire, bonding it to the materials being joined.

The solder wire process is streamlined and can be completed in a single step or adapted to fit seam shapes through programmed paths. It is commonly used for applications such as mobile accessory cable assemblies, PCB circuit board soldering, and engine component welding.

Advantages of Laser Soldering

Whether using solder wire, solder paste, or other forms of tin-based materials as soldering media, laser soldering offers several advantages over traditional soldering iron techniques:

1. Non-Contact Process & High Electrode Quality
   As a type of laser welding, laser soldering is a non-contact method that does not require physical interaction with the substrate or electronic components during circuit soldering. In contact-based soldering, contamination of electrodes by solder residues can compromise overall performance. In contrast, non-contact laser soldering minimizes electrode damage, reduces tool wear, and avoids issues such as mechanical stress or soldering tip degradation associated with traditional methods.

2. Precise Temperature Control
   Tin-based materials are highly sensitive to heat. Laser soldering, when integrated with high-frequency temperature feedback systems, ensures uniform and consistent heating, reducing deformation and thermal damage. It also mitigates uncertainties caused by tin melting. The precision of laser welding allows localized heating exclusively at the connection points, eliminating any thermal impact on the components themselves.

3. High Precision and Microscopic Processing
   The entire laser soldering process is highly precise and controllable. For fine soldering seams, traditional methods often struggle with insufficient depth-to-width ratios or re-melting issues, potentially leading to false soldering  (defective joints). Laser soldering, however, enables extremely accurate control with spot sizes as small as micrometers. It easily achieves deep, narrow seams with depth-to-width ratios up to 1:10, making it ideal for batch processing environments with micro-scale solder points.

Songsheng Opto-Electronics Laser Constant-Temperature Soldering System

The Songsheng Opto-Electronics Laser Soldering System consists of a multi-axis servo module, real-time temperature feedback system, CCD coaxial positioning system, and semiconductor laser. Through years of process refinement, Songsheng has independently developed intelligent soft soldering software compatible with multiple file formats. Its innovative PID online temperature regulation feedback system ensures precise constant-temperature soldering, guaranteeing high yield and accuracy. The system is widely applicable for both integrated production lines and standalone processing. Key features include:

1. Non-contact soldering eliminates mechanical stress damage and minimizes thermal effects.

2. Multi-axis intelligent work platform (optional) adapts to complex and precision soldering processes.

3. Coaxial CCD imaging positioning and monitoring clearly displays solder joints and enables real-time alignment correction, ensuring processing accuracy and automated production.

4. Proprietary temperature feedback system directly controls solder joint temperature and displays real-time soldering temperature curves to ensure high yield.

5. Four-point coaxial integration of laser, CCD, temperature measurement, and indicator light solves multi-optical path alignment challenges in the industry and avoids complex debugging.

6. Achieves a 99% yield rate with solder joint diameters as small as 0.2mm and shorter soldering times per joint.

7. X, Y,  Z-axis flexibility supports soldering for a wider range of components and broader applications.