In reflow soldering, solder paste is first applied to the PCB using a stencil, coating only the contact pads. Surface-mount components are then placed using a pick-and-place machine. The assembled board is passed through a reflow oven, where it goes through four key stages:

• Pre-heat: The temperature gradually rises to safely evaporate solvents in the solder paste and avoid thermal shock to components.
• Soak: The board is held at a steady temperature to activate the flux and ensure even heat distribution across the PCB.
• Reflow: Heat peaks to melt the solder, allowing it to bond the components to the board through a process known as wetting.
• Cooling: The board is cooled in a controlled manner to solidify the solder joints without introducing stress or cracks.

Reflow soldering isn’t just widely adopted—it’s preferred for a reason. Its versatility and efficiency make it the go-to method for modern electronics manufacturing. Here are some of the key benefits it brings to the table:

• Precision and repeatability: Reflow soldering supports mass production by delivering consistent results across high volumes of complex PCBs.
• Strong electrical connections: The process forms reliable joints that ensure stable electrical performance.
• Compatibility with fine-pitch components: Reflow soldering enables the use of compact, high-density component layouts, including BGAs and microchips.
• Automation-ready: It integrates seamlessly with automated assembly lines, improving throughput and reducing manual errors.

Introducing nitrogen into the reflow oven creates an inert atmosphere that significantly improves soldering results. In an oxygen-rich environment, solder can oxidise during heating, weakening the joints. Nitrogen displaces oxygen and helps:

• Minimise oxidation on solder and component leads
• Improve wetting, resulting in cleaner, shinier solder joints
• Reduce soldering defects like voids, bridging, or tombstoning
• Enable lower peak temperatures, protecting heat-sensitive components

This not only enhances solder joint quality but also extends the lifespan of components and the PCB itself.