High FR4-Tg will have better mechanical and chemical resistance to heat and moisture than standard FR4. The higher the Tg value, the better the temperature resistance of the material, so high Tg is more and more popular. High Tg materials have the following properties: Resistance to high temperatures Long delamination durability (aging of materials to consider for safety reasons) Low thermal expansion (Lower Z-axis CTE) Excellent PTH reliability Good mechanical properties High-temperature durability High thermal shock resistance Excellent thermal stress resistance