SMT PCB assembly process

What Are the Requirements for SMT Processing?

With the continuous development of electronic products toward miniaturization, the size of components is getting smaller and smaller. This advancement places higher demands not only on the components themselves but also on the environment in which they are processed. As a result, Surface Mount Technology (SMT) processing faces increasingly stringent requirements.

For an SMT factory to maintain efficient operations and high-quality control, it must go beyond strict process management and ensure that the SMT workshop environment is carefully regulated. Additionally, understanding some key precautions is essential for smooth and successful production.

In this article, we’ll explore the main requirements for SMT processing, covering environmental standards and critical operational tips.

1. Environmental Requirements of the SMT PCB Assembly Workshop

SMT production equipment is highly precise, combining sophisticated mechanical and electronic technologies. To ensure optimal operation, minimize environmental damage to components, and improve overall product quality, the SMT workshop must meet specific environmental conditions.

1.1 Power Supply

• Voltage:Typically requires single-phase AC220V (220V ±10%, 50/60Hz) or three-phase AC380V (380V ±10%, 50/60Hz).

• Capacity:The power supply capacity should be at least double the actual power consumption of the equipment to ensure stable operation.

1.2 Exhaust System

• Reflow ovens and wave soldering machines need proper exhaust ventilation.

• For fully hot blast furnaces, ensure the exhaust duct maintains a minimum flow rate of500 cubic feet per minute (14.15 m³/min).

1.3 Temperature and Humidity Control

• Ideal Ambient Temperature:23°C ± 3°C (general acceptable range: 17°C–28°C).

• Relative Humidity:45%–70% RH.

• Install temperature and humidity monitoring devices in the workshop and ensure facilities are in place for climate regulation.

1.4 Air Supply

• Use clean, dry, and purified compressed air.

• Factory air sources or dedicated oil-free air compressors are suitable.

• General pressure requirement:greater than 7 kg/cm².

• Ensure compressed air undergoes de-oiling, dust removal, and water removal processes.

• Use stainless steel or pressure-resistant plastic pipes for air lines.

1.5 Anti-Static Measures

• Personnel must wear anti-static clothing, shoes, and wristbands.

• Equip the workshop with anti-static flooring, seat pads, packaging bags, turnover boxes, PCB racks, and other ESD protection measures.

• Establish a designated anti-static work area to prevent damage to sensitive components.

2. SMT PCB Assembly Processing Tips

Beyond maintaining the right environment, attention to operational details plays a crucial role in the quality and efficiency of SMT PCB assembly.

2.1 Solder Paste Refrigeration

• Store unused solder paste in refrigeration units.

• Recommended Storage Temperature:5°C–10°C (never below 0°C).

• Proper handling and stirring of solder paste before use are essential but will not be detailed here, as plenty of resources are available online.

2.2 Timely Replacement of Consumable Parts

• Placement machine parts such as nozzles and feeders wear out over time.

• Regularly inspect and replace worn or damaged parts to prevent placement errors, reduce material wastage, and maintain high production efficiency.

• Check for nozzle blockages and ensure feeders function properly.

2.3 Furnace Temperature Measurement

• Reflow soldering quality is closely linked to precise temperature settings.

• Conductat least one furnace temperature test per day, preferably two, to maintain an optimal temperature profile.

• Regular adjustments to the temperature curve help ensure reliable soldering results.

• Never skip this step to save time or costs—it is crucial for quality assurance.

Conclusion

Maintaining the right workshop environment and following proper operational procedures are vital for successful SMT processing. By paying close attention to power supply, ventilation, temperature control, air quality, and anti-static measures, you can significantly improve the efficiency and quality of PCB assembly. Additionally, diligent equipment maintenance and process monitoring will ensure a smooth production flow.

If you have any PCB assembly projects, please feel free to reach out to us atsales7@hitechpcb.com— we’re here to help!