With the full implementation and continuous deepening of the EU RoHS environmental directive, the lead-free substitution process in the global SMT Solder industry has entered a stage of comprehensive acceleration. Traditional tin-lead solder has long occupied the mainstream position in the electronic manufacturing welding market due to its advantages of low melting point, good wettability and low cost. However, this type of solder has a high lead content, which can easily cause heavy metal pollution during product waste disassembly and smelting treatment, and long-term contact will also cause irreversible harm to human health. Under the general trend of global green manufacturing and compliant production, the civil and commercial application scenarios of tin-lead solder are continuously shrinking. At present, only a small amount of use is retained in special rigid-demand fields such as military industry and aerospace, and the rest of the general electronic manufacturing scenarios have basically completed lead-free substitution. Lead-free solder with the Sn-Ag-Cu system as the core has officially become the mainstream welding material in the industry.
The lead-free upgrade of the industry is by no means a simple solder alloy replacement, but a systematic process reconstruction covering the entire SMT production line, which has brought all-round changes to the production equipment, material adaptation, process parameters and quality control of terminal manufacturing. The core process difference is reflected in the substantial increase of the welding temperature system. The melting point of lead-free solder is about 30°C higher than that of traditional tin-lead solder, which directly drives the peak temperature of Reflow Soldering to increase to more than 240°C. The substantial increase of the temperature threshold puts forward new stringent requirements for the supporting materials and equipment accuracy of the entire production line.
From the perspective of production practice, the high-temperature welding working condition forces the heat resistance upgrade of PCB boards and electronic components. Ordinary boards cannot withstand continuous high-temperature reflow, and are prone to defects such as board delamination, warpage deformation, and substrate carbonization. Components are also prone to failures such as package cracking, parameter drift, and heat resistance failure. At the same time, the temperature control accuracy, heat zone balance, and heating rate stability of the reflow oven have also become the core focus of process control. Old equipment can no longer meet the mass production demand of lead-free welding due to insufficient temperature control accuracy and uneven heat field, which promotes the terminal production line to complete equipment iteration and upgrade.
Flux technology adapted to lead-free high-temperature welding has become the core tackling direction of industry iteration and upgrade, and is also the key core to ensuring the yield of lead-free welding. Traditional lead-containing supporting flux has poor thermal stability, and is prone to premature decomposition and carbonization failure in the lead-free high-temperature reflow environment, which not only loses the ability of activation and deoxidation, but also produces a large number of process defects such as residue, virtual welding, and poor wetting. To this end, the industry continues to research, develop and iterate high-temperature resistant special flux systems. By optimizing the activator formula, modified resin system, and blending high-temperature resistant solvent components, the high-temperature thermal stability and continuous activation ability of the flux are greatly improved, which perfectly adapts to the lead-free high-temperature welding working condition.
Under the superimposed constraints of RoHS and REACH dual international environmental regulations, the halogen-free iteration of flux is also accelerated synchronously. Although the traditional halogen-containing flux has excellent activation effect, halogen residue can easily cause reliability hazards such as electrochemical corrosion on the PCBA board surface and decreased insulation performance, and cannot adapt to harsh scenarios such as high-end electronics, outdoor equipment, and vehicle industrial control. Therefore, low-halogen and zero-halogen environmentally friendly flux has become a rigid demand in the industry, gradually replacing traditional halogen-containing flux and realizing the green and compliant upgrade of the welding process.
After years of technical tackling and mass production iteration, Domestic Solder enterprises have completely broken the technical monopoly of overseas brands, and realized all-round independent control in the core field of lead-free solder. At present, domestic manufacturers have mastered a full set of core technologies such as lead-free alloy ratio debugging, high-temperature resistant halogen-free flux research and development, precision printing process adaptation, and mass production quality control, and have complete independent research and development and large-scale production capabilities. The core performance indicators of domestic lead-free Solder Paste, such as wettability, high-temperature reliability, batch consistency, and printing adaptability, have been continuously optimized. At present, they have gradually caught up with and partially benchmarked the international advanced level, fully supporting the lead-free, high-end, and green transformation of the domestic electronic manufacturing industry.
