Soldering is a crucial electronic equipment manufacturing process requiring specific requirements and specifications. Nitrogen usage is a critical aspect that significantly influences the outcome of selective soldering. This discussion provides an in-depth analysis of the role and benefits of nitrogen in selective soldering, including the amount of nitrogen used and its impact on the quality and efficiency of the process. In addition, we will examine the various factors that determine the appropriate nitrogen concentration for selective soldering and suggest suitable alternatives to nitrogen.
How much nitrogen does selective soldering use?
Depending on the manufacturer, selective soldering systems require a higher nitrogen purity level compared to other equipment, ranging from 99.99% to 99.9995%. Using nitrogen in selective soldering can reduce dross, the amount of rework needed, solder costs, and the number of defective units returned. In actual applications, nitrogen purity requirements may vary depending on welding materials, environmental requirements, and other factors.
Benefits of using nitrogen in selective soldering
The use of nitrogen in selective soldering offers several benefits:
- Prevents Oxidation: Nitrogen is used in soldering to ensure the process is free from oxygen due to its inert properties. Oxygen would react with the solder, creating an oxide layer that can lead to quality problems or short circuits.
- Improves Solder Quality: Using nitrogen results in better wetting and clean, shiny joints with less flux and a lower temperature. This leads to a more efficient process with less residue and potentially less need for post-soldering cleaning.
- Reduces Dross Formation: High-purity nitrogen can prevent dross formation, a common issue in soldering processes. Dross is a waste product that can build up around the work area and interfere with the soldering process.
- Extends Nozzle Lifetime: High-purity nitrogen can also extend the lifetime of the nozzles used in the soldering process, which can result in cost savings.
- Allows for Process Customization: Different factors determine the effectiveness of the selective soldering process, including the machine’s configuration, the attributes of the flux, and the nozzle choice. Nitrogen purity is essential and can be adjusted to meet specific process requirements.
- Cost and Supply Control: A nitrogen generator can lower operating costs and ensure a steady nitrogen supply, reducing dependence on third-party suppliers. This is particularly important as nitrogen is critical to soldering activities.
- Reduces Surface Tension: Using inert nitrogen gas in selective soldering reduces surface tension, which allows the solder to break away from the solder site cleanly.
- Improves Solder Spreading Behavior: Selecting the required gas purity is critical in ensuring appropriate solder spreading behavior at low temperatures.
The process of introducing nitrogen in selective soldering
The process of introducing nitrogen in selective soldering involves creating a nitrogen-rich environment around the soldering area, and this is typically achieved using a nitrogen generator to supply high-purity nitrogen.
The nitrogen flow displaces the air (oxygen) from the solder bath. When the printed circuit board (PCB) approaches the solder bath, the waves are flushed, and the covers are opened so the PCB can come to the nozzles and be soldered. After the PCB has been lifted from the nozzles after soldering, the covers are closed again.
Consideration for choosing the proper nitrogen purity in selective soldering
Welding materials: Different materials require different amounts of welding gas. For example, less argon and nitrogen are needed for copper products, but more nitrogen is required for stainless steel.
Welding current and time: Generally, the higher the welding current and the longer the time, the more nitrogen will be used.
Temperature during welding: High temperatures will be generated during the welding process, and an appropriate amount of nitrogen can help reduce the temperature around the weld and prevent welding problems such as pores.
Part size and shape: Larger welds require more nitrogen to protect the weld from air contamination, while round or curved parts require more nitrogen to fill voids to ensure complete coverage of the entire weld.
Alternatives to using nitrogen in selective soldering
While nitrogen is commonly used in selective soldering due to its inert properties that prevent oxidation and improve solder quality, there are alternatives to using nitrogen. However, these alternatives may not provide the same level of quality and efficiency as nitrogen in the soldering process.
- On-site Nitrogen Generation: Instead of relying on nitrogen deliveries, which can be costly, some companies opt for on-site nitrogen generation using a compressor and a nitrogen generator. This method can lower operating costs and ensure a steady supply of nitrogen.
- Laser Soldering: This method uses a laser to heat the solder joint, which can provide precise control over the soldering process. Laser soldering can be used for selective soldering of through-hole components.
- Mini-flame Soldering: This method uses a small flame to heat the solder joint. Like laser soldering, it can provide precise control over the soldering process and be used for selective soldering through-hole components.
- Robotic Solder Systems: These systems use a robot-controlled soldering iron and solder wire. They can be used for selective soldering of through-hole components. Robotic soldering systems can be more cost-effective than particular soldering processes that use nitrogen, especially when considering the cost and accessibility of nitrogen.
- Wave Soldering with Pallets: This is an alternative to a selective soldering dip process. In this method, all SMD components are covered by the pallet. However, this process requires dedicated tooling for each assembly.
In conclusion
In summary, the use of nitrogen in selective soldering machine is essential. Nitrogen has several benefits, including preventing oxidation, improving solder quality, and extending nozzle life. The purity of nitrogen is also crucial for the soldering process and can be customized to meet specific process needs. Although other options are available, such as on-site nitrogen generation or laser soldering, the effectiveness of using nitrogen in the soldering process is unmatched. However, it is also essential to consider the alternatives’ convenience and cost-effectiveness based on the specific needs of each manufacturing unit.
