The RoHS standard restricts the use of harmful substances in electronic and electrical equipment, and the requirements for SMT include changes in solder, selection of PCB materials, process adjustments, and increased environmental requirements. PCBA processing plants need to strengthen technology, supply chain management, employee training, and establish a quality system to address challenges. The RoHS directive was approved by the European Union on January 27, 2003, aimed at restricting the use of certain hazardous substances in electronic and electrical equipment, including lead (Pb), mercury (Hg), cadmium (Cd), hexavalent chromium (Cr ^ 6+), polybrominated biphenyls (PBB), and polybrominated diphenyl ethers (PBDE). The use of these substances in electronic products is strictly limited, for example, the content of lead in electronic products should not exceed 0.1% (1000ppm), and the content of cadmium should not exceed 0.01% (100ppm). These restrictions ensure the environmental friendliness of electronic products and reduce potential harm to the environment and human health.
1. Changes in solder properties
The RoHS standard requires the use of lead-free solder instead of traditional lead containing solder. There are significant differences between lead-free solder and lead based solder in terms of flow diffusion performance, melting point temperature, and other aspects. The flow and diffusion performance of lead-free solder is poor, which requires corresponding adjustments in printing accuracy, mounting accuracy, and furnace temperature settings for SMT surface mount processing to ensure the soldering effect.
2. Selection of PCB materials
The RoHS standard has also had an impact on the selection of PCB materials. Traditional FR4 materials may be damaged at high temperatures, so SMT processing plants need to evaluate and select PCB materials that can withstand the high-temperature impact of lead-free soldering. This change not only increases material costs, but also puts higher demands on the design and manufacturing of PCBs.
3. Adjustment of process flow
The RoHS standard prompts adjustments in the process flow of SMT surface mount processing. For example, in the lead-free reflow soldering process, it is necessary to optimize the temperature curve to ensure the soldering quality. Meanwhile, due to the poor fluidity and wettability of lead-free solder, it is prone to problems such as tin slag and dull and rough appearance of solder joints. Therefore, regular maintenance and cleaning of welding equipment are required.
4. Increase in environmental protection requirements
The RoHS standard not only focuses on the restriction of the use of hazardous substances, but also promotes the environmental protection process of the entire electronic manufacturing industry. SMT processing plants need to strictly comply with relevant environmental regulations to ensure effective disposal of waste and pollutants during the production process. In addition, RoHS certification also requires manufacturers to provide detailed technical documentation and compliance statements to demonstrate that their products comply with environmental standards.
