For circuit boards exposed to high thermal loads, the necessary long-term operating temperature must be determined early on, in order to select an appropriate material. 
Typical application areas
■Multilayer boards with many layers
■Industrial electronics
■Automobile electronics
■Fineline trace structures
■High temperature electronics
Tg ValueThe glass transition temperature (Tg) is an important normative dimension for the base material that determines the temperature at which the resin matrix converts from a glassy, brittle condition into a soft, elastic one.
The Tg value of the base material sets here an upper boundary, at which the resin matrix decomposes and a subsequent delamination occurs. The Tg is thus not the value of the maximum operational temperature, but rather that which the material can endure for only a very short time. A guideline for a continuous thermal load is an operating temperature approximately 25°C below the Tg.
When the glass transition temperature (Tg) is over 170°C, it is referred to as a high Tg material.
High Tg materials have the following properties:
■high glass flow temperature value (Tg)
■high temperature durability
■long delamination durability
■Low Z axis expansion (CTE)
T260 / T288 value
The decomposition temperature Td of a resin system depends on the binding energies within the polymers, and not on the glass transition temperature Tg. A good indicator for this characteristic is the T260 or T288 value, which specifies the time until delamination at 260°C or 288°C, respectively.
Technical options for high Tg circuit boards
*Conductive Anodic Filament, undesirable conducting filament in the substrate of a circuit board
