Context: At the glass transition temperature the resin in the composite softens and significantly increases thermal expansion; exceeding Tg then exerts mechanical overload on the board components - e.g. the joints and the vias. Below Tg the thermal expansion of the resin roughly matches copper and glass, above it gets significantly higher. As the reinforcement and copper confine the board along the plane, virtually all volume expansion projects to the thickness and stresses the plated-through holes. Repeated soldering or other exposition to higher temperatures can cause failure of the plating, especially with thicker boards; thick boards therefore require high Tg matrix.

Question: What's the temperature at which resin softens and expands called?
Answer: glass transition temperature

Question: Along with vias, what makes up the components of a board?
Answer: joints

Question: What will happen to the components when the temperature of resin goes above that of glass transition?
Answer: mechanical overload

Question: When resin stays below Tg, its thermal expansion is similar to that of copper and what other material?
Answer: glass

Question: What do thick boards require to resist plating failure?
Answer: high Tg matrix

Question: The resin in the composite hardens when?
Answer: Unanswerable

Question: Virtually no volume expansion projects to where?
Answer: Unanswerable

Question: Thin boards require high what?
Answer: Unanswerable

Question: Exposition to lower temperatures can cause failure of what?
Answer: Unanswerable