1. Raw Panels1 GLASS TRANSITION TEMPERATURE n At temperatures < T g u board is stronger u board is stiffer

2. Raw Panels2 COEFFICIENT OF THERMAL EXPANSION L  HEAT Coefficient of thermal expansion  T = T 2 - T 1

3. Raw Panels3 Example Find the free expansion of a 10 inch copper bar heated from 25 to 45 o C. CTE copper = 170 x 10 -6 in/in/ o C  T = 45 - 25 = 20 C o  = (L)(CTE)(  T ) = (10 in)(170 x 10 -6 in/in/ o C)(20 C o ) = 3.4 x 10 -3 in = 3.4 mil

4. Raw Panels4 COEFFICIENT OF THERMAL EXPANSION n If temperature < Tg, CTE is higher, thus deformation  increases

5. Raw Panels5 COEFFICIENT OF THERMAL EXPANSION n Laminates (e.g. glass-epoxy) cause CTE to be lowered in direction of fibres but not perpendicular to them Metal barrel or (via) tries to expand and cracks