Why nitrogen is essential for PCB assembly

Whether you're using reflow, wave, or selective soldering for printed circuit board (PCB) manufacturing, you'll need readily available nitrogen (N₂). This is because of its low oxide properties, which helps solder flow. It also generates low heat and produces minimal dross. These benefits for PCB assembly, among others, are covered below.

Before getting into N₂ for PCB assembly, it's also worth discussing why PCBs are so important. They're an essential part of the electronic manufacturing services (EMS) market. EMS companies produce PCBs and total products containing PCBs on behalf of original equipment manufacturers (OEMs). You can learn more about this in our related article on the EMS market.

Read on to learn more about why N₂ is essential for PCB assembly, starting with a brief introduction on the soldering process. We also cover on-site nitrogen generation.

A person operates a machine to cut a circuit board

Soldering processes

The right soldering process will depend on whether through-hole technology (THT) or surface mount technology (SMT) is used. As you might imagine, THT involves holes to secure components, while SMT uses a specific type of adhesive known as SMT glue (or red glue), especially during wave soldering or double-sided reflow soldering. This type of adhesive helps to hold components in place before the soldering process, preventing them from moving or falling off.

Wave and selective soldering are used for THT, while reflow is implemented on PCBs with SMT. This is because wave and selective soldering pass over the solder. On the other hand, reflow soldering involves a paste that is later hardened in an oven around 250 C.

It's also worth pointing out that wave is more commonly used due to its economical approach. Regardless of the type used, you'll want readily available N₂ for soldering. This is explained in the following section.

N₂ benefits for PCB assembly

The reason N₂ is used in PCB manufacturing is due to its inert properties. If compressed air would be used, the solder would react to the oxygen in it, causing an oxide layer to form. This would create short circuits and quality problems and can lead to corrosion.

With that, it's important to have the right flow. You'll want to size your N₂ generator according to specifications, based on the soldering type. For example, reflow requires a higher flow than selective.

In addition to what's already been said, there are other benefits to N₂:

Lower oxide formation vs oxygen

Oxide found in oxygen can dry out solder. Since N₂ is low in oxides, it's preferred for soldering. That said, surface oxides must be removed with fluxes before soldering. A flux is a clear liquid that is applied to areas ready to be soldered. As said above, the flux is used to break up the oxide layer. Also, when flux evaporates, residues are left. It's best to use as little flux as possible. N₂ helps avoid any resulting contact issues.

Better solder flow

Low surface tension is important for controlling solder flow. This allows the solder to go exactly where it's needed. N₂ enables better solder flow than compressed air and is particularly useful for dense PCBs with components close together. It also avoids rework as much as possible.

Less dross

Dross is oxidized tin and is considered waste in the PCB assembly process. Therefore, the less dross made during manufacturing, the better. This is due to reduced maintenance needs. N₂ is important for mitigating such issues.

Generate your own N₂ supply for high quality PCB assembly

It's common for EMS companies to receive N₂ through delivery services. That said, it's more cost-effective to use on-site nitrogen generation. This is because generating your own supply avoids the need for delivery logistics and associated costs. Additionally, you’ll reduce transport emissions. It also allows you to maintain quality consistency.

Producing nitrogen typically requires an air compressor, nitrogen generator, air treatment equipment like dryers and filters, as well as air and N₂ storage. When it comes to dryers and filters, the ones needed depend on the application.

For small to medium sized PCB assembly companies, it’s possible to use an oil-injected air compressor with the right air treatment equipment. In addition, using an on-site generator with Pressure Swing Adsorption (PSA) technology will produce the high-purity N₂ that soldering requires.

Learn more about on-site nitrogen generation

Do you want to learn more about nitrogen generation?

Read more about nitrogen generation on our eBook:

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Discover our nitrogen generators

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Maximizing the robustness and simplicity of membrane technology, the NGM⁺ is a compact, quiet and dependable nitrogen generator. Thanks to its exceptionally low air and energy consumption, it also offers the lowest cost of ownership on the market today.

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NGPs 2-9. Our smallest PSA generator ensures a cost-efficient, flexible and reliable nitrogen supply with a purity of up to 99.999%. - Nm³/h: 20°C – 1 bar(a) – 0% RH - Scfm: 68°F – 14.5 psi(a) – 0% RH

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