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Nitrogen Generation's Critical Role in Soldering
South-Tek Systems N2-GEN® nitrogen gas generators.
 

A controlled atmosphere is absolutely necessary for electronic manufacturing, as it requires very particular temperatures, timing, structures, and environments. For this reason, nitrogen gas has been used successfully to create and maintain clean, dry, inert atmospheres. Nitrogen is used in PCB manufacturing in selective soldering, reflow soldering and ovens. While bulk nitrogen is often bought for this purpose, a nitrogen generator offers a safer, more cost-effective way of obtaining nitrogen gas.

There are many ways to obtain the nitrogen necessary for reflow soldering, ovens, and selective soldering. Some of these methods include buying bulk liquid nitrogen, using liquid dewars, and using high-pressure cylinders. Another method is generating nitrogen from air. This process is convenient, safe, and cost-effective, especially when compared with the previous methods.

A nitrogen generator produces high-purity N2 gas at the point of process safely, reliably and efficiently. From portable and compact systems to large, high-output systems, nitrogen generators allow businesses, property owners and government operations to produce their own N2 gas on demand.

Membrane and PSA Technology
There are two ways of generating nitrogen: membrane and pressure swing adsorption (PSA) technology. Nitrogen generators separate N2 molecules directly from the air we breathe. Air contains 79 percent nitrogen and these generators use simple, green technology to filter out the other gases, concentrating the nitrogen gas into a storage tank for process usage.

Nitrogen generators with membrane technology use compressed air forced through a polymeric hollow fiber to selectively permeate oxygen, water vapor and other impurities out of its side walls, while allowing nitrogen to flow through its center and emerge as high purity N2 gas.

PSA technology uses a carbon molecular sieve (CMS) to adsorb oxygen and water vapor molecules under high pressure, while allowing nitrogen to pass through. A sieve bed pressure vessel is filled with the CMS, which is then pressurized with air. O2, CO2, CO, and other molecules are captured and held inside the CMS while N2 molecules are drawn off into a receiving tank. O2, CO2, CO, and other molecules are then flushed from the CMS by depressurizing the sieve bed. Finally, the CMS is flushed and cleansed, ready for new air.

Nitrogen Gas in Electronics
Nitrogen gas is used for electronics manufacturing in situations where it is critical to reduce oxygen and maintain a clean, dry atmosphere. There are several examples of this, although nitrogen gas is used most often for PCB manufacturing processes that include reflow soldering and selective soldering to attach surface mount components to the board.
Diagram of nitrogen generator installation.
 


Nitrogen is vital for reflow soldering and reflow oven applications. With the increased use of SMT replacing through-hole technology, reflow soldering of surface mount components onto printed circuit boards is widespread. Reflow ovens provide a time- and temperature-controlled environment for the effective soldering of surface mount components.

For reflow soldering, components are placed on top of a PCB on solder pads with solder paste applied. These boards are then conveyed into the reflow oven, which melts the solder particles in the solder paste, bonding the components to the pads on the circuit boards.

There are different styles of reflow soldering, but convection soldering generally uses nitrogen gas applied to base metals. The N2 gas minimizes oxidation of the surfaces to be soldered. The chemical reactions necessary for soldering require high temperatures, but metal oxidizes at a faster rate with heat applied, weakening the solder.

Selective soldering, another application that uses nitrogen, is often employed when the heat of the reflow oven may be too great for some SMT components on the board.

Selective soldering may follow the reflow oven process in the production line for soldering other SMT components that are able to withstand the level of heat. In these cases, great care must be taken in the selective soldering of additional components to avoid damaging the reflow-soldered components. Nitrogen gas may also be used in selective soldering to eliminate the possibility of oxidation that would weaken the solder.

Benefits of Nitrogen Generation
Nitrogen generators are smart for business. A nitrogen generator is an investment that, once paid off, can potentially save thousands of dollars each month, based on what a company currently pays in monthly gas charges, tank leasing and contracts with a gas supplier.

South-Tek Systems offers free ROI analyses, which explain how much and within what time period a nitrogen generator will positively impact a customer's bottom line. Nitrogen generators can save businesses up to 90 percent in costs over time, especially when compared with sourcing nitrogen from gas companies.

Costs aside, nitrogen generators are also reliable. They eliminate the risk of running out of gas at an inopportune time. A nitrogen generator is always equipped to create high-purity N2 gas simply from the air surrounding it. Generators are safe alternatives to handling high-pressure cylinders and use simple mechanics. Therefore, maintenance is easy and only requires a yearly filter change. If properly maintained, a nitrogen generator can last more than 20 years. Finally, nitrogen generators are flexible — a company's output requirements may dictate the size and style of nitrogen generator needed, but the equipment is flexible, efficient and produces gas as needed.

Electronics manufacturing is only one example of the usefulness of nitrogen generators. Using nitrogen in electronics manufacturing will improve the process of selective soldering, reflow soldering, and reflow ovens. Using a nitrogen generator to source the needed nitrogen will further cut costs, while producing high-purity gas safely and reliably.

 

Contact: South-Tek Systems, LLC, 2940 Orville Wright Way, Wilmington, NC 28405 910-332-4173 fax: 910-332-4178 E-mail: info@southteksystems.com Web:
http://www.southteksystems.com

 
 
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