RO4350B has a published Tg above 280°C and a typical decomposition temperature of 390°C in the cited data sheet. Tg and Td describe different material tests. Neither number is a permissible continuous operating temperature or a recommended soldering temperature.
What to decide before release
For assembly, obtain a process window that accounts for component ratings, moisture, board mass and the complete laminate system. For service life, evaluate thermal aging and the actual environment. A high Tg does not remove the need for reliability testing.
Checks to put in your design brief
- Name the thermal test method
- Use the assembly supplier’s qualified profile
- Review the whole hybrid stackup
Important distinction
Do not label >280°C as decomposition temperature. That confuses two distinct properties and can lead to incorrect process assumptions.
Sources & basis
Material facts follow the cited source. Design checks are preliminary guidance, not supplier process instructions.