1. Resin system formula
Cross link density: High cross link density resins (such as pure phenolic epoxy resins) are brittle and prone to edge breakage during processing, making them suitable for low-speed precision milling; Low crosslink density resins (such as modified epoxy with added flexible segments) have good toughness, but they are prone to softening during high-temperature processing, and the cutting temperature needs to be controlled below 120 ℃.
Packing type:
Glass fiber (accounting for more than 60%): enhances hardness but wears down tools during grinding, requiring diamond coated tools (with a lifespan 5-8 times longer than hard alloys).
Alumina filler: improves thermal conductivity (thermal conductivity increases from 0.2W/(m · K) to 1.5W/(m · K)), but it is prone to abrasive wear during processing and requires an increase in coolant flow rate.
Hollow glass microspheres: reduce density (up to 1.2g/cm ³), but drilling can easily cause interlayer separation and require support with upper and lower pads.
2. Curing degree of the board
Undercured plate (gel time>20% of theoretical value): it is easy to stick the knife during processing, the surface roughness Ra increases from 1.6 μ m to 6.3 μ m, and it may continue to cure during storage to generate internal stress.
Overcured board (glass transition temperature Tg>theoretical value 10 ℃): brittleness significantly increases, and the edge breakage rate during milling increases by 30% -50%. It is necessary to reduce the feed rate to 50% -70% of the conventional value.
