. In order to ensure this softness, elastomer is usually introduced into the epoxy resin. However, doing so will have a more serious consequence, that is, the flame retardancy will become worse. Therefore, to solve this problem, researchers usually take the following measures.
- Phosphorous flame retardant is adopted. For example, the use of phosphate ester flame retardant, in the combustion of it can promote dehydration carbonization reaction, so that the surface of the material formed a layer of carbonization film, cut off the contact with oxygen, so that it is difficult to burn.
- Adopt nitrogen-containing flame retardant. Nitrogen atoms are introduced into the molecular structure of the resin to generate an inert gas to oxygen during combustion.
- Adopt inorganic flame retardant. For example, the addition of magnesium hydroxide, aluminum hydroxide and other inorganic filler, they release crystal water in the combustion, reduce the combustion temperature, thereby inhibiting the combustion.
- Resin with special structure is used. For example, epoxy resin containing phenyl alkyl is used in the resin combination.
The disadvantages of halogen material
As we mentioned above, Halogen means fluorine (F), chlorine (CL), bromine (Br), iodine (I), Atastatium (At). Additionally, it gets famous as all the halogen elements have numerous advantages for the flame retardant period. Particularly chlorine (CL) and bromine (Br) are frequently utilized in flame retardant for electronics matters.
So many often used printed circuit boards like FR4 PCB, and CEM3 PCB comprise halogen-containing flame retardants. Some institutions researched and have shown us regarding this matter that halogen-containing flame retardant equipment are very harmful to us as it emits a huge quantity of highly destructive and toxic gas with the terrible smell during it gets burning, that has the capacity of affecting our beloved environment furthermore carcinogenic to human beings.
Pay attention to the performance of halogen-free material
Insulation
Since P or N replaces halogen, the polarity of the molecular bond of the epoxy resin gets decreased a bit; as a result, it enhances the insulation resistance and the break-down voltage.
Thermal durability
The elements of nitrogen and phosphorus that occur in the halogen-free PCB are much greater than the traditional board; thereby, the grade of monomer molecular weight along with Tg are boosted. The halogen-free PCB has a relatively low coefficient of thermal expansion (CTE) since in the time of heating, the molecular mobility of a halogen-free PCB will exist less than the traditional epoxy resin board.
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