What is Glass Transition Temperature (Tg)

By Bester PCBA

Last Updated: 2024-01-02

What is Glass Transition Temperature (Tg)

Glass Transition Temperature (Tg) is a parameter that refers to the temperature at which a plastic material undergoes a transition from a glassy, rigid state to a rubbery, flexible state. It is a characteristic of plastic and epoxy resin materials used in the manufacturing of printed circuit boards.

When the temperature is below the Tg, the material is in a glassy state, exhibiting properties similar to that of glass – rigid and brittle. However, when the temperature exceeds the Tg, the material enters a rubbery state, becoming soft and flexible.

The Tg value of a PCB material is of utmost importance as it determines several key properties and performance characteristics. It directly influences the material’s heat resistance, moisture resistance, chemical resistance, and overall stability during PCB production and operation.

A higher Tg value indicates that the PCB material can withstand higher temperatures, making it particularly valuable in lead-free manufacturing processes that involve high Tg materials. This becomes crucial in meeting the demands of high-density mounting technologies like Surface Mount Technology (SMT) and Chip Mount Technology (CMT), where PCBs require substrates with exceptional heat resistance to accommodate small apertures, fine lines, and thinning.

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