As environmental and health issues have become the focus of global attention, electronic packaging materials and processes are facing a transition to “greenâ€, in which environmental protection and non-toxicity of epoxy resin printed circuit board copper-coated substrate flame retardants are continuously achieving results. Green flame retardant Has become the mainstream of epoxy circuit boards.
At present, most flame retardants for epoxy resin printed boards are tetrabromobiphenyl A (TBBPA) or Sb2O3. In the mid-1980s, it was found that under certain combustion conditions it produced highly toxic bromine oxides and furans. In 1995, German researchers discovered the harmful tetrabromodibenzo-p-dioxin (TCDD) from the bromide material combustion. The European Union (EC) draft proposes to ban the use of such halogen-containing flame retardants from January 2004. Since then, developed and other countries have increasingly increased their activities in reducing, replacing, and banning. Among them, countries in the Nordic countries have the most ban on bromine-containing materials. positive. My country started late in this regard.
The development of halogen-free/Sb-based green type substrate materials is underway in foreign countries. Its technical characteristics can be summarized as follows: Firstly, the flame retardant properties are improved from the resin formulation (especially paper-based copper clad laminates). Second, phosphorus and nitrogen are used. Resins, inorganic metal fillers, etc., as the main flame-retardant materials; fire-retardant methods are hydration cooling, carbonization, increase the substrate decomposition temperature, inhibition of volatile components, etc., in addition to a copper foil coating resin. According to experts from the China Epoxy Resin Industry Association, the focus of the green paper-based CCL in the study of resin formulations is to reduce or completely eliminate the use of dry oil-modified phenolic resins (such as tung oil-modified phenolic resins). Use other flame-retardant resins such as epoxy resin and phosphorus, nitride, and other inorganic flame retardants to add, use in combination to achieve the flame-retardant effect.
For the green epoxy circuit board products such as CEM3, FR4, there are currently three kinds of flame-retardant technology approaches:
1, the reaction, let nitrogen, phosphorus and epoxy resin reaction modification, so that the main chain of epoxy resin has a molecular structure of phosphorus and nitrogen. This method is still dominated by the main flame-retardant resin;
2. Add flame retardants with chemical structures such as phosphorus and nitrogen in epoxy resin;
3. Compounding, using a high nitrogen-containing chemical structure or a resin or compound containing a triazine ring backbone as a curing agent for epoxy resins, and with other halogen-free flame retardant additives.
It is reported that currently alternatives to bromide flame retardants are limited to red phosphorus and use high levels of inorganic fillers, but red phosphorus itself has problems with thermal stability and toxicity. Phosphorus-based flame retardants reduce the glass transition temperature and other properties of the board, and a suitable content is 2 to 2.5%. The weight of ATH (Al trihydrate) or inorganic filler such as Mg(OH)2 should reach 50%. In turn, it will affect the performance of the board. In particular, rigidity and hardness are increased, brittleness is increased, impact and tensile strength are reduced, and they also cause moisture problems in the board. Therefore, the board baking time using such flame retardants is longer. Recently, Japanese companies have developed copper-clad circuit boards using ZHS (zinc hydroxide stannate) or ZS (zinc stannate) with inorganic fillers as flame retardants. This kind of board has good flame retardant, heat resistance, harmful smoke and other features. These green substrate materials include glass-based CCL and composite-based CCL in addition to epoxy glass-based CCL.