How to Select the Wavelength of Semiconductor Lasers for Laser Soldering?

How to Select the Wavelength of Semiconductor Lasers for Laser Soldering?

日期：2025-01-23    

In laser soldering, different wavelengths are suitable for different soldering materials. In practical production applications, how should the wavelength of semiconductor lasers be selected? Songsheng Optoelectronics provides a detailed introduction and sharing. The selection of the semiconductor laser's wavelength is crucial and requires comprehensive consideration of factors such as the workpiece material, solder characteristics, and solde.

Consider the Absorption Characteristics of Workpiece Materials 

Different materials exhibit significant differences in their absorption capabilities for different laser wavelengths. Generally, metallic materials have better absorption of shorter laser wavelengths. For example, copper demonstrates relatively high absorption in the near-infrared range (800–1100 nm), while its absorption is lower in the visible light spectrum. Therefore, when soldering copper or copper-plated pads, it is advisable to choose a semiconductor laser with a wavelength in the 800–1100 nm range. This ensures efficient absorption of laser energy by the workpiece, thereby improving soldering efficiency and quality.

Songsheng Optoelectronics Constant-Temperature Laser Soldering System Module Diagram

For non-metallic materials or composite materials, their absorption characteristics differ significantly from those of metallic materials. Certain plastic materials can melt or decompose under laser irradiation at specific wavelengths, enabling welding. For example, some plastics containing additives like carbon black exhibit strong absorption of near-infrared laser wavelengths. When welding such plastic materials, it is recommended to use a semiconductor laser with a wavelength around 900–1000 nm to match the material's absorption requirements and achieve optimal welding results. 

There is a wide variety of soldering materials, each exhibiting distinct laser absorption characteristics. Common tin-based solders—such as tin-lead alloys and lead-free solders (e.g., tin-silver-copper alloys)—demonstrate strong absorption in the near-infrared spectrum. Typically, lasers with wavelengths around 808 nm, 940 nm, or 980 nm are efficiently absorbed by tin-based solders, enabling rapid heating and melting for optimal soldering results. Therefore, when performing laser soldering with tin-based solders, semiconductor lasers at these wavelengths should be prioritized.

Beyond tin-based solders, specialized solders like aluminum-based or gold-based alloys exhibit different absorption properties. For instance, aluminum-based solders absorb 1060 nm wavelength lasers more effectively. When soldering aluminum components or using aluminum-based solders, selecting a 1060 nm semiconductor laser ensures superior energy absorption and reliable joint formation.

Wavelength Selection Based on Soldering Process Requirements 

For high-precision soldering applications, such as micro-component assembly in electronics manufacturing, selecting a semiconductor laser wavelength with precise energy control and excellent beam focusing capabilities is critical. Shorter wavelengths—such as 808 nm or 940 nm—typically offer superior beam quality and focusing performance, enabling highly concentrated energy delivery to microscopic solder joints.

Additionally, semiconductor lasers at these wavelengths allow fine-tuned power adjustment through precise drive current modulation. This ensures optimal energy input during soldering, preventing thermal damage to adjacent sensitive components while maintaining consistent and reliable weld quality.

For welding processes requiring rapid thermal cycling, such as high-speed soldering in mass production lines, semiconductor laser wavelengths capable of delivering instantaneous high energy density with fast thermal response should be selected.

In the near-infrared spectrum, wavelengths like 980nm demonstrate superior power conversion efficiency and rapid thermal response characteristics. These lasers can generate high-power output within milliseconds, enabling instantaneous solder melting for ultrafast heating. When laser irradiation ceases, the solder rapidly solidifies due to minimal heat accumulation. This rapid heating-cooling cycle significantly enhances production throughput while meeting the demands of high-volume manufacturing.

Furthermore, the abbreviated thermal cycle effectively minimizes the heat-affected zone (HAZ), reducing thermal impact on adjacent components and ensuring consistent product quality with improved reliability.

Songshang Optoelectronics 976nm Water/Air-Cooled Constant-Temperature Semiconductor Laser System Diagram

Songsheng Optoelectronics' Self-Developed 976nm Constant-Temperature Semiconductor Laser for Precision Soldering Applications

Songsheng Optoelectronics has independently developed a 976nm constant-temperature semiconductor laser specifically designed for laser soldering and plastic welding applications. Featuring an ultra-fast PID algorithm (15μs response time), this laser system effectively prevents solder joint burnout. The integrated closed-loop temperature control system utilizes infrared sensors to monitor and precisely regulate the heating zone temperature in real-time, maintaining a stable preset temperature throughout the welding process.

Available in both air-cooled and water-cooled configurations to meet diverse customer requirements, the laser offers multiple power options including 10W, 100W, 200W, 300W, and 500W.

Special Environmental Considerations for Laser Selection

Certain challenging operating environments - including high temperatures, high humidity, or strong electromagnetic interference - may adversely affect laser performance and welding quality. When selecting optimal laser wavelengths for such conditions, these special factors must be carefully considered:

1. High-Temperature Environments:
        Some laser wavelengths may experience power attenuation or beam quality      degradation under elevated temperatures. In these scenarios, it's critical      to select lasers with superior thermal management capabilities and      temperature stability, or implement additional cooling solutions to ensure      consistent performance.

2. High-Humidity Conditions:
        Moisture-resistant laser systems with proper sealing should be      prioritized, along with appropriate environmental controls.

3. EMI-Intensive Applications:
        For environments with strong electromagnetic interference, wavelength      selection should account for EMI resistance, complemented by necessary      shielding measures.

In all cases, implementing appropriate protective measures and technical safeguards ensures reliable laser performance and consistent welding quality under challenging operating conditions.