Some time ago, halogen-containing PCBs were a thing because of their benefit as flame retardants for electronic components.
But these days, most designers are using the halogen-free PCB. And it’s because the variant is a more eco-friendly option.
So, what’s more about halogen-free PCBs? Keep reading to find out more on this topic.
Halogen-free PCBs: What it Means
A periodic table of the Halogen group
As the name suggests, you can produce a type of PCB from a copper-clad halogen-free lamination. And the halogen-free PCB refers to a board that lacks halogen elements.
And these elements are iodine, Bromine, Astatine, Fluorine, and Chlorine. So, if you want this PCB, it’s vital to ensure that the halogen materials are less than 1500 ppm. Alternatively, your board can have lesser than 900 ppm of Br (bromine) or Cl (chlorine).
Also, according to the Japan Circuit Association (JPCA)-ES-01-2003 standard, your copper-clad halogen-free lamination should have a bromine chlorine quantity of less than 0.09% weight to ratio. In addition, chlorine and bromine should be less than 0.15%.
So, what are halogen-free PCB substrates? It refers to FR4 materials that lack halogens. Instead, they contain nitrogen and phosphorus. And the PCB’s solder mask ink is halogen-free as well.
The Benefits of Halogen-Free PCBs
The advantages of halogen-free PCBs include the following:
- If you compare halogen epoxy resin to Phosphorus and Nitrogen compound epoxy resins, you’ll notice that the latter hardly creates H-bonds with H-atoms in water. Therefore, it means that normal halogen flame retardant PCBs absorb more moisture compared to halogen-free circuit boards.
- You can work with halogen-free PCBs at a higher temperature. Hence, you can use these PCBs for high-power applications. And it’s all thanks to their high TG or glass melting point.
- These PCBs have impressive electrical insulation. So, halogen-free laminates can resist high electric shock. And it’s because the polarities of P & N are minute compared to halogens. In other words, bromine-containing materials have a higher polarity compared to halogen-free materials.
- Halogen-free PCBs have increased mechanical properties or strength, allowing you to drill holes in the board conveniently.
- You can use the PCB for high-frequency applications because of its high-frequency performance.
- Typically, you’d have a higher PCB molecular bond/ weight if you switch halogens for P and N. As a result, the molecule movement will be lesser than the standard epoxy resin. So, it’s best to use halogen-free boards with reduced thermal expansion and increased thermal stability compared to regular PCBs with halogens.
In short, you’ll get increased performance, reliability, and stability with the halogen-free PCBs over the standard PCBs with halogen flame retardant.
Why Can’t You Use Halogens in PCBs?
An engineer inspecting a PCB
In truth, halogen elements have various benefits relating to flame retardancy. For instance, you’ll use more chlorine compounds or bromine as flame retardants in the electronic industries for electronic products.
Further, people used PCBs with halogenated flame retardants like CEM3 and FR4.
Then, over time different scientists conducted extensive research on equipment with halogen-containing flame retardant or halogen PCB.
And they found that the equipment released toxic chemicals and harmful gases that could be a health risk or cause deadly carcinogenic to humans. An excellent example is exposing a person to bromine, which could result in skin irritation, burning eyes, blurred vision, breathing difficulties, etc.
China and the European Union currently restrict PBDE (polybrominated diphenyl ethers) and PBB (polybrominated biphenyls) to create sustainable development. Furthermore, on July 1, 2006, RoHS passed a law that banned the use of PBDE and PBB.
Two years after, HBCD (hexabromocyclododecane) and TBBPA (tetrabromobisphenol A) joined the list. And at the time, PBDE, PBB, and TBBPA were essential PCB flame retardants.
Is Halogen-free PCBs Fire-resistant?
The answer is yes! And it’s all thanks to the flame retardant that halogen-free PCBs use.
So, if you use a PCB with phosphorus flame retardant, it contains resin. Hence, when you burn this substrate, it changes to a polyphosphoric acid.
And this acid has powerful dehydration properties. As a result, the acid will create a carbonated film on the resin’s surface. Then, the film insulates the resin and air, which ceases the burning.
What if the halogen-free PCB has nitrogen and phosphorous flame retardant? With these compounds and resin, you can burn the substrate. And it will produce a non-flammable gas that will stop the burning.
Halogen-free PCBs are great additions if you want a green-compliant device that can be widely applied in every market.
Also, it’s a fantastic choice if you want a reliable board with excellent mechanical properties and impressive insulation you can use for flame-retardant panels and other PCB products.
What do you think about this type of board?
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