1. In the soldering process of the PCB board electronics industry, more and more manufacturers are shifting their focus to selective soldering.
2. Selective soldering can complete all solder joints simultaneously, thus reducing production costs and mitigating temperature differentials encountered in reflow soldering.
3. Moreover, it minimizes the impact on sensitive components and is compatible with future lead-free soldering requirements, rendering it increasingly prevalent in usage.
Process characteristics of selective soldering
The process characteristics of selective soldering can be best understood through comparison with wave soldering. A key distinction lies in how the solder interacts with the PCB: in wave soldering, the entire lower section of the PCB is submerged in liquid solder, whereas selective soldering targets specific areas. Due to the PCB’s poor thermal conductivity, adjacent components and areas are shielded from heating and solder melting during the process. Furthermore, flux must be applied prior to soldering, but unlike wave soldering, it is selectively applied only to the intended soldering areas rather than the entire PCB. Selective soldering is primarily suited for through-hole components, representing a novel approach that necessitates a comprehensive understanding of its processes and equipment for successful implementation.
Typical selective soldering processes include flux spraying, PCB preheating, dip soldering, and drag soldering.
Flux coating process
In selective soldering, the flux coating process plays a crucial role. At the soldering stage, the flux must remain active to prevent bridging and oxidation of the PCB. Flux spraying involves using an x/y manipulator to guide a flux nozzle over the PCB, precisely applying flux to the soldering positions. Flux can be applied via single-nozzle, micro-hole spray, or synchronized multi-point/pattern spray methods. Accuracy is paramount post-reflow, ensuring flux application is confined solely to solder joints. Micro-spray patterns typically maintain a diameter greater than 2mm, with a positional accuracy of ±0.5mm to consistently cover solder joints. Suppliers specify flux amounts, often recommending a 100% safety tolerance.
Preheating process
In selective soldering, preheating serves primarily to evaporate flux solvents, optimizing viscosity before encountering the solder wave. It minimizes thermal stress rather than influencing soldering quality. Preheating temperatures are determined by PCB thickness, device packaging, and flux type. There are differing theoretical approaches to preheating: some advocate preheating before flux application, while others proceed directly to soldering. Process flows can be adjusted based on specific needs.
Soldering process
Selective soldering employs two main techniques: drag soldering and dip soldering. Drag soldering utilizes a small tip solder wave, ideal for tight spaces like individual pins or rows on a PCB. Quality is maintained by adjusting PCB speed and angle relative to the solder wave. Tip diameters typically remain below 6mm to accommodate varied soldering needs. Manipulators allow approach angles from 0° to 12°, with a recommended 10° tilt for most devices. Compared to dip soldering, drag soldering offers superior heat transfer efficiency due to PCB movement and solder wave interaction. Specific parameters such as solder temperature (275°C to 300°C) and drag speed (10mm/s to 25mm/s) enhance process stability and reduce bridging risks. Nitrogen is introduced to prevent wave oxidation, ensuring reliable solder joints.
Machine features
Selective soldering machines boast high precision and flexibility. Modular designs allow customization for unique production requirements, ensuring adaptability for future needs. Manipulators offer precise positioning (±0.05mm), ensuring consistency across production batches. Their 5-dimensional movement allows optimal PCB contact with the tin surface at any angle, crucial for quality welding outcomes. Titanium alloy stylus tips on manipulator splint devices enable controlled tin wave height adjustments via programmable controls, ensuring process stability.
Despite its advantages, single-nozzle drag soldering processes suffer from longer cycle times due to sequential flux spraying, preheating, and soldering stages. Efficiency limitations become pronounced with increased solder joint quantities, contrasting with the throughput of traditional wave soldering. However, innovations such as dual-nozzle designs can enhance throughput significantly, demonstrating ongoing advancements in selective soldering technology.
2. Selective soldering can complete all solder joints simultaneously, thus reducing production costs and mitigating temperature differentials encountered in reflow soldering.
3. Moreover, it minimizes the impact on sensitive components and is compatible with future lead-free soldering requirements, rendering it increasingly prevalent in usage.
Process characteristics of selective soldering
The process characteristics of selective soldering can be best understood through comparison with wave soldering. A key distinction lies in how the solder interacts with the PCB: in wave soldering, the entire lower section of the PCB is submerged in liquid solder, whereas selective soldering targets specific areas. Due to the PCB’s poor thermal conductivity, adjacent components and areas are shielded from heating and solder melting during the process. Furthermore, flux must be applied prior to soldering, but unlike wave soldering, it is selectively applied only to the intended soldering areas rather than the entire PCB. Selective soldering is primarily suited for through-hole components, representing a novel approach that necessitates a comprehensive understanding of its processes and equipment for successful implementation.
Typical selective soldering processes include flux spraying, PCB preheating, dip soldering, and drag soldering.
Flux coating process
In selective soldering, the flux coating process plays a crucial role. At the soldering stage, the flux must remain active to prevent bridging and oxidation of the PCB. Flux spraying involves using an x/y manipulator to guide a flux nozzle over the PCB, precisely applying flux to the soldering positions. Flux can be applied via single-nozzle, micro-hole spray, or synchronized multi-point/pattern spray methods. Accuracy is paramount post-reflow, ensuring flux application is confined solely to solder joints. Micro-spray patterns typically maintain a diameter greater than 2mm, with a positional accuracy of ±0.5mm to consistently cover solder joints. Suppliers specify flux amounts, often recommending a 100% safety tolerance.
Preheating process
In selective soldering, preheating serves primarily to evaporate flux solvents, optimizing viscosity before encountering the solder wave. It minimizes thermal stress rather than influencing soldering quality. Preheating temperatures are determined by PCB thickness, device packaging, and flux type. There are differing theoretical approaches to preheating: some advocate preheating before flux application, while others proceed directly to soldering. Process flows can be adjusted based on specific needs.
Soldering process
Selective soldering employs two main techniques: drag soldering and dip soldering. Drag soldering utilizes a small tip solder wave, ideal for tight spaces like individual pins or rows on a PCB. Quality is maintained by adjusting PCB speed and angle relative to the solder wave. Tip diameters typically remain below 6mm to accommodate varied soldering needs. Manipulators allow approach angles from 0° to 12°, with a recommended 10° tilt for most devices. Compared to dip soldering, drag soldering offers superior heat transfer efficiency due to PCB movement and solder wave interaction. Specific parameters such as solder temperature (275°C to 300°C) and drag speed (10mm/s to 25mm/s) enhance process stability and reduce bridging risks. Nitrogen is introduced to prevent wave oxidation, ensuring reliable solder joints.
Machine features
Selective soldering machines boast high precision and flexibility. Modular designs allow customization for unique production requirements, ensuring adaptability for future needs. Manipulators offer precise positioning (±0.05mm), ensuring consistency across production batches. Their 5-dimensional movement allows optimal PCB contact with the tin surface at any angle, crucial for quality welding outcomes. Titanium alloy stylus tips on manipulator splint devices enable controlled tin wave height adjustments via programmable controls, ensuring process stability.
Despite its advantages, single-nozzle drag soldering processes suffer from longer cycle times due to sequential flux spraying, preheating, and soldering stages. Efficiency limitations become pronounced with increased solder joint quantities, contrasting with the throughput of traditional wave soldering. However, innovations such as dual-nozzle designs can enhance throughput significantly, demonstrating ongoing advancements in selective soldering technology.
