SMTA International Conference Proceedings


HIGHER THERMAL STABILITY WITH BROMINE-FREE SUBSTRATES

Author: Robert Demaree
Company: Cookson Electronics PWB
Date Published: 9/22/2002   Conference: SMTA International


Abstract: Bromine-free laminate materials are entering the marketplace in greater numbers. Bromine-free materials have historically had lower performance than their brominated cousins, but over time have achieved near equal performance in many areas.

Thermal stability is an increasingly critical performance area for electrical laminates. The thermal stability of a bromine-free laminate must be at least as good as that for a similar brominated laminate. Bromine-free laminates expected to see use in lead-free applications may have even higher thermal requirements.

Two bromine-free products from Polyclad Laminates are evaluated alongside two brominated materials, which represent the best practice in the industry. Thermal stability is evaluated in circuit boards by using high temperature exposure for short periods of time.

The laminate’s thermal performance is evaluated in long-term oven aging tests. The falloff in properties over the age time is tracked with temperature and an approximate useful life can be estimated from the data. The test results on circuit boards and laminates show that bromine-free materials can have advantages over comparable brominated materials.

Material B represents a developmental bromine-free epoxy system known as PCL-HF-571. Material "B" is a higher Tg, higher performance bromine-free system that uses a combination of reactive flame retardants and flame retardant fillers.

For comparison, data for a typical FR-4 product, material "C", is presented alongside. Polyclad’s TURBO 370 high performance epoxy (Material "D") is included to compare these results with the thermal stability of the newer generation of high performance brominated epoxy systems.



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