Optimal Wavelength Determination for Laser Soldering: 915nm versus 976nm

Optimal Wavelength Determination for Laser Soldering: 915nm versus 976nm

In laser soldering, different wavelengths are suitable for various soldering materials and application scenarios. The specific choice between 915nm or 976nm wavelengths requires comprehensive consideration of material absorption rates, process requirements, and equipment performance. Songsheng Optoelectronics will summarize key analyses and recommendations. 

From the Perspective of Material Absorption Characteristics:

915nm: Some studies suggest that this wavelength exhibits favorable absorption rates with tin, enabling effective energy transfer for melting and achieving high-quality soldering results.

976nm: Tin-based solders also demonstrate strong absorption capabilities in the near-infrared spectrum around 976nm, allowing efficient laser energy absorption for rapid heating and melting.

                                                                                                   Songsheng Optoelectronics  Water-Cooled/Air-Cooled Thermostatic Semiconductor Laser

From the Perspective of Laser Performance:

System Diagram

 915nm

High Stability: The absorption peak of ytterbium-doped fiber at 915nm is relatively broad, making the laser less sensitive to wavelength drift in pump diodes. This results in greater system stability and easier control in fiber laser design.

Mature Technology: The 915nm pumping scheme has been widely adopted in the fiber laser market, making related technologies and equipment more mature, with a well-established supply chain.

 976nm

Higher Electrical-to-Optical Conversion Efficiency: The absorption at 976nm is approximately three times that of 915nm, meaning less pump power is required to generate the same laser output. This leads to higher energy efficiency, with 976nm achieving over 42% electrical-to-optical conversion efficiency, compared to around 30% for 915nm.

Higher Optical-to-Optical Conversion Efficiency: When using 976nm pump light to emit 1070nm laser radiation, the quantum defect (energy loss during electron transition) is only ~8.8%, whereas 915nm has a quantum defect of ~14.5%. This gives 976nm a significant advantage in optical-to-optical conversion efficiency.

                                                                        Songsheng Optoelectronics Thermostatic Laser Soldering System DiagramFrom the Perspective of Soldering Process Requirements

915nm

Precise Energy Control:
In applications requiring high-precision energy control and excellent beam focusing, the 915nm wavelength—when paired with optimized laser systems—enables precise energy concentration on microscopic solder joints. This makes it ideal for microelectronics, complex circuit boards (PCBs), and miniature structural components demanding ultra-fine soldering.

Superior Beam Homogeneity:
The 915nm laser exhibits outstanding beam uniformity and stable energy output, ensuring consistent heating of solder pads and enabling rapid temperature rise for efficient soldering.

                                                                                                                                                Laser Wire-Feeding Soldering Process Animation

976nm

Ideal for high-speed soldering in mass production lines, the 976nm wavelength offers higher power conversion efficiency and rapid thermal response. It delivers high-energy laser output in short bursts, enabling instant solder melting and ultra-fast heating. Additionally, the solder cools and solidifies quickly after laser irradiation ceases, ensuring efficient cycle times.

Summary

In conclusion, the optimal choice between 915nm and 976nm depends on practical process validation (we offer complimentary sample testing).

Songsheng Optoelectronics has been pioneering integrated laser soldering solutions since 2016. Initially providing optical components, we now design thermostatically controlled semiconductor laser systems. Our proprietary fully sealed multi-beam (laser, imaging, temperature sensing, red light) coaxial soldering head enables:

• Real-time temperature monitoring at the processing point

• Closed-loop internal control with PID algorithms between the laser power supply and temperature control unit

• Full closed-loop temperature regulation across 100–400°C

• 20μs response time for adjustments, eliminating control instability caused by manual PID tuning