Halogen free printed circuit board is called Halogen Free PCB. Halogen free PCB is made of halogen-free copper clad laminate. Halogen elements are extremely life-threatening chlorine, bromine, fluorine, iodine and very. For PCB to be considered “halogen-free”, the content of chlorine or bromine must be less than 900 ppm, and the total amount of halogen materials must be less than 1500 ppm.
In PCB manufacturing, the relevant halogen elements (such as chlorine and bromine) do have some benefits, but these benefits do not exceed the negative effects they may cause in our daily life.
Chlorine is used as a flame retardant to protect components and as an element in PVC coating of wires.
Bromine is used as a sterilant. It can also be used as a flame retardant in electronic components.
Despite their advantages, they cannot avoid their negative effects. Exposure to chlorine or bromine can cause coughing, nausea, blurred vision, skin irritation, dyspnea and eye burns. Chlorine compounds can also combine with hydrocarbons to form dioxins, a deadly carcinogen.
It is best to avoid large amounts of chlorine or bromine in PCB. As technology advances, manufacturers are developing effective PCBs that do not use these harmful chemicals.
Halogen in polychlorinated biphenyls
Halogen has many uses in PCB.
Chlorine is used as flame retardant or protective coating for PVC wires. It is also used as a solvent for semiconductor development or cleaning computer chips.
Bromine can be used as a flame retardant to protect electrical components or to sterilize components.
What level is considered halogen-free?
By limiting the use of halogen, the international Electrochemical Commission (IEC) set the total halogen content at 1500 ppm. The limit of chlorine and bromine is 900 ppm.
If you comply with the hazardous substances restriction (RoHS), the PPM limit is the same.
Please note that there are various halogen standards on the market. Since halogen free production is not a legal requirement, the allowable levels set by independent entities (e.g. manufacturers) may vary.
What is the substitute for Halogen Free PCB?
At present, most halogen free PCB mainly use phosphorus and phosphorus nitrogen instead.
When the phosphorus containing resin is burned, it is decomposed by thermal decomposition to form polyphosphate, which is highly dehydrated and forms a carbonized film on the surface of the polymer resin. The insulating surface of insulating resin contacts with air to extinguish flame and achieve flame retardant effect. Non combustible gases are produced in the combustion process of polymer resins containing phosphorus nitrogen compounds to help the resin system flame retardant.
Advantages of Halogen Free PCB
These PCBs do not contain health problems because they do not contain more than 1500 ppm chlorine or bromine. When the PCB is disposed of, it will not affect the environment, which is different from the traditional PCB, which produces dioxin (a toxic chemical substance) when producing electronic waste.
Performance of Halogen Free PCB
- Insulation: due to the substitution of halogen by P or N, the polarity of epoxy resin molecular bond is reduced, thus increasing the insulation resistance and breakdown voltage.
- Water absorption: due to the relatively low electrons of N and P in nitrogen phosphorus reducing oxygen resin, the possibility of hydrogen atom bonding in water is lower than that of halogen. The water absorption of halogen free PCB is lower than that of conventional PCB, which affects the reliability to a certain extent.
- Thermal stability: the content of nitrogen and phosphorus in Halogen free PCB is higher than that in common PCB, so the monomer molecular weight and TG value increase.
Under heating, the molecular mobility of halogen free PCB is lower than that of conventional epoxy resin board, so halogen free PCB has relatively low coefficient of thermal expansion (CTE).
Application of Halogen Free PCB
Since they are halogen-free, they can be used in any industry using PCB. The most important applications in industry are mobile and automotive, because we used to keep in touch with mobile phones, cars and other vehicles. If the PCB is halogen-free, we can be sure that it has less impact on our health.