Inert Gas Soldering Systems, Which Use A Controlled Nitrogen Blanket Atmosphere And An Entry Vacuum Oxygen/nitrogen Exchange Chamber, Offer Several Key Benefits:

Inert gas soldering systems, which use a controlled nitrogen blanket atmosphere and an entry vacuum oxygen/nitrogen exchange chamber, offer several key benefits:

· Reduced Oxide Formation: Nitrogen minimizes the formation of oxides during soldering.

· Flux Selection Flexibility: It allows greater flexibility in choosing fluxes.

· Elimination of Post-Cleaning: Post-soldering cleaning requirements are eliminated.

Soldering in a nitrogen atmosphere enhances solder joint quality and manufacturing yields. This process is particularly beneficial for lead-free products assembled at high temperatures, as it prevents oxidation and contamination of printed-circuit boards (PCBs). However, the cost of installing a nitrogen-based environment must be considered against the potential improvement in solder joint quality and the cost savings from reduced repair work on manufactured circuits.

· Reflow Soldering with Nitrogen (N2):

1. Purpose: Adding nitrogen to the SMT reflow oven reduces oxidation on the welding surface and improves wettability. Nitrogen, being inert, does not form compounds with metals and isolates oxygen and metals in the air, preventing oxidation.

2. Principle: In a nitrogen environment, the surface tension of solder is lower than in the atmosphere, improving solder fluidity and wettability. Nitrogen also reduces oxygen and contaminants, significantly decreasing oxidation during high-temperature soldering, particularly for the second side reflow.

3. Limitations: Nitrogen cannot reverse severe oxidation on parts or circuit boards; it only has a remedial effect on slight oxidation.

4. Advantages: Reduces oxidation Improves welding ability Enhances solderability Reduces voiding rate due to improved solder fluidity

5. Disadvantages: High cost Increased chance of tombstone formation Enhanced capillary (wicking) effect

Suitable Applications: OSP surface treatment dual-sided reflow boards, parts, or circuit boards with poor tin wettability, such as QFN, large packages, and high-density BGA.

· Selective Soldering with Nitrogen (N2):

1. Purpose: Nitrogen is used in selective soldering machines to prevent excess oxide formation on the solder surfaces of the Selective Wave and Multi Wave, and minimize dross formation during nozzle flushing.

2. Function: The nitrogen flow around the Select Wave nozzle prevents oxide layer formation on the wave surface, aiding flux activity. The required nitrogen purity depends on the process needs, with higher purity providing better assistance and lower consumption. However, nitrogen purity at the soldering position is never the same as the supply due to mixing with surrounding air.

Process Quality: The quality of the solder process dictates the necessary nitrogen purity based on production demands.

· Wave Soldering with Nitrogen (N2):

1. Application: Inert gas atmospheres can be applied to wave soldering processes either partially or fully. Partial treatment involves only the solder wave area under the inert gas environment, while a more effective but costly tunnel system can operate with adjustable rest oxygen levels between 20 ppm and 500 ppm in the soldering area, creating an inert atmosphere in the preheat and cooling areas.

2. Oxidation and Dross: Oxidation is more visible in wave soldering processes, and dross removal is necessary. Typically, oxidation speed doubles with every 10 K rise in temperature. Tunnel systems and partial inert atmosphere systems can reduce dross, with tunnel systems offering more significant improvements.

3. Dross Reduction: For electronic production processes where dross reduction is critical, rest oxygen levels of about 1000 ppm with a partial inert gas atmosphere are adequate. To maximize the benefits of nitrogen wave soldering, rest oxygen levels below 500 ppm are required, necessitating a tunnel wave soldering system.

4. Defect Reduction: Considering parameters such as layout, temperature profile, or solderability of materials, defect rates can be significantly reduced in a nitrogen atmosphere. This environment improves wetting characteristics and surface tension of liquid solder, minimizing defects like incomplete through-hole penetration, insufficient wetting, bridging, and solder balls, resulting in higher product quality and reduced repair work.

5. In this working environment of reflow soldering and wave soldering production, workers need to take esd protection measures when assembling circuit boards or soldering. Generally, they should wear ESD Clothes, ESD Gloves and ESD Wrist Strap etc., to prevent static electricity from occurring.

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