What is Laser Soldering?

What is Laser Soldering?

  Laser soldering is a precision welding technology that utilizes laser as a heat source. It involves heating solder materials with a laser to melt them and connect electronic components or materials. This technology is widely applied in fields requiring high precision and reliability, such as microelectronics manufacturing, automotive electronics, aerospace, medical devices, and other industries.

Process Flow Diagram: Laser Wire Soldering vs. Laser Solder Paste Soldering

Compared to traditional soldering techniques, laser soldering offers several unique advantages:

High Precision: The laser can be focused onto a welding area at the micron level, making it suitable for tiny and complex components.

Non-Contact Process: Since laser soldering does not require direct contact with the material surface, it avoids mechanical stress, making it ideal for temperature-sensitive or fragile components.

Rapid Heating & Cooling: The highly concentrated heat input enables fast heating and cooling, minimizing thermal impact on surrounding components.

Strong Controllability: Soldering temperature and energy output can be precisely regulated through a closed-loop system, ensuring process stability and consistency.

Laser soldering is widely used in electronic device assembly, semiconductor packaging, PCB soldering, and other applications requiring high-precision soldering.

Difference Between Laser Soldering and Soldering Iron Soldering

Comparative Diagram: Laser Soldering vs. Soldering Iron Soldering

Differences in Soldering Methods

  Soldering iron soldering typically employs a contact-based approach, which can easily scratch the product surface. During the soldering process, the soldering iron tip exerts pressure on the workpiece, potentially creating sharp solder joints and conduction risks. In contrast, laser soldering utilizes a non-contact method, effectively avoiding these issues—it neither causes mechanical damage nor applies pressure to the components.

Differences in Soldering Adaptability

  When soldering workpieces with complex surfaces, soldering iron welding faces limitations due to the large space occupied by the iron tip and wire feeder, making it prone to interference from surrounding components. Laser soldering, however, features a compact wire feeder and is less susceptible to interference. Additionally, the laser spot size can be adjusted to accommodate different solder joint dimensions, meeting diverse product requirements. Traditional soldering iron methods, on the other hand, often require replacing or redesigning the iron tip, making laser soldering significantly more adaptable.

Differences in Impact on Components

  Soldering iron welding relies on conductive heat transfer, which can adversely affect heat-sensitive components. In laser soldering, the laser only heats the area exposed to the beam, enabling rapid localized temperature rise and minimizing thermal impact on surrounding parts.

Differences in Energy and Material Consumption

  In terms of material conservation, soldering iron welding primarily relies on the iron tip to deliver thermal energy. However, tip degradation and wear often lead to insufficient heating temperatures. The contact-based process also accelerates tip deterioration, requiring frequent maintenance and replacement that significantly increases operational costs.

Regarding energy efficiency, conventional soldering irons employ conductive heat transfer, resulting in substantial thermal dissipation. This inefficient heating mechanism leads to unnecessary power consumption and higher energy waste.

Differences in Welding Precision

  Conventional soldering iron processes are limited by their inherent technical constraints and control methods, resulting in restricted wire feeding accuracy and welding precision. In contrast, laser welding technology features rapid heating and cooling characteristics, producing more uniform and finer metallic compounds during soldering, which enhances the mechanical properties of solder joints. The localized heating capability is particularly advantageous for densely packed components and heat-sensitive elements on PCBs, while effectively reducing post-welding bridging between solder points.

Differences in Safety and Controllability

  The non-contact nature of laser soldering minimizes flux and solder residue risks, reduces harmful fume emissions and waste generation, and enables real-time precise temperature control at solder points to prevent thermal damage. This approach significantly simplifies process optimization while substantially lowering occupational hazards for operators.

Why Choose Semiconductor Lasers as Light Sources for Laser Soldering Systems?

Songsheng Optoelectronics 3U/BOX 976/980nm Constant-Temperature Semiconductor Laser Diagram

  With advancements in IC chip design and packaging technology, SMT (Surface Mount Technology) is evolving towards miniaturization with higher stability and integration density, where traditional soldering iron techniques can no longer meet production requirements. The number of pins on individual components continues to increase, while the pin spacing of QFP (Quad Flat Package) integrated circuits keeps shrinking, progressing toward even finer precision.

  As an innovative soldering process that addresses the limitations of conventional methods, non-contact laser soldering is increasingly replacing traditional iron soldering—driven by its superior precision, efficiency, and reliability. This transition has become an irreversible industry trend.

  The laser source used in laser soldering processes is primarily a semiconductor laser source, available in near-infrared or blue light wavelengths, offering excellent thermal effects. The uniformity of the laser beam and the continuity of laser energy significantly impact the even heating and rapid heating of solder pads, resulting in high welding efficiency.

  The working principle of semiconductor lasers involves an excitation mechanism where electrons in semiconductor materials transition between energy bands to emit light. By using the cleavage planes of semiconductor crystals to form two parallel mirror surfaces as reflectors, a resonant cavity is created. This cavity allows light to oscillate, feedback, and amplify, thereby generating and outputting laser radiation.

The fundamental structure of semiconductor lasers is based on a PN junction, but laser diodes feature a "double heterostructure," where the light-emitting layer (active layer) is sandwiched between semiconductor material layers with different bandgaps. Additionally, in laser diodes, the crystal's cleavage planes serve as reflective mirrors (resonators). The materials used include gallium (Ga), arsenic (As), indium (In), and phosphorus (P). For multi-quantum well structures, elements such as aluminum (Al) are also employed.

Advantages of Laser Diodes
  Laser diodes offer high efficiency, compact size, lightweight design, and cost-effectiveness. Notably, multi-quantum well structures achieve an efficiency of 20-40%, with high energy efficiency being their most prominent feature. Additionally, their continuous output wavelength range spans from infrared to visible light, and pulsed output can reach up to 50W (with 100ns pulse width), making them an ideal choice for laser soldering applications.

Role of Temperature Closed-Loop Control in Laser Soldering Systems

Songsheng Opto-Electronic Temperature Closed-Loop Feedback System Diagram

Real-time Monitoring and Feedback
  The temperature closed-loop control system utilizes high-speed infrared sensors to monitor solder joint temperatures in real time. Temperature data is transmitted to the laser controller, enabling real-time process supervision.

Precise Temperature Control
  With real-time data feedback, the laser controller precisely adjusts output energy to maintain solder joint temperatures within set parameters, ensuring consistent welding quality.

Overheat Protection
   The system responds instantaneously to rapid temperature rises by reducing laser power or cutting output, preventing thermal damage to component leads or solder joints.

Enhanced Welding Quality
  Through precise thermal management, the system minimizes defects like scorching, cold joints, or insufficient soldering, guaranteeing joint strength and reliability.

Automation and Intelligence
  Integrated with CCD imaging, the system automatically records and analyzes process data, providing actionable insights for quality control and production optimization to boost efficiency and product quality.

Adaptability and Adjustability
  The system flexibly adjusts laser parameters for diverse materials and soldering requirements, accommodating complex application scenarios.

  The Songsheng Optoelectronic Laser Soldering System consists of a multi-axis servo module, real-time temperature feedback system, CCD coaxial alignment system, and semiconductor laser. Through years of welding process refinement, Songsheng  has independently developed intelligent soft soldering software that supports importing multiple file formats. The innovative PID online temperature regulation and feedback system ensures precise constant-temperature soldering, guaranteeing high yield rates and accuracy. This product is widely applicable for both inline production and standalone processing, offering the following key advantages:

1. Non-Contact Soldering: No      mechanical stress damage and minimal thermal impact.

2. Multi-Axis Intelligent Work Platform (Optional): Adaptable to complex and precision soldering processes.

3. Coaxial CCD Imaging & Monitoring System: Provides clear visualization of solder joints and real-time alignment correction, ensuring precision and automated production.

4. Proprietary Temperature Feedback System: Directly controls solder joint temperature and displays real-time temperature curves, ensuring soldering consistency.

5. Four-in-One Coaxial Design (Laser, CCD, Temperature      Measurement, Guide Light): Solves industry challenges of multi-optical path alignment and eliminates complex calibration.

6. High Precision & Speed:      Achieves a 99% yield rate with solder joints as small as 0.2mm in diameter and ultra-fast soldering per joint.

7. Multi-Axis Flexibility (X/Y/Z):      Accommodates diverse component soldering for broader applications.