Context: There are quite a few different dielectrics that can be chosen to provide different insulating values depending on the requirements of the circuit. Some of these dielectrics are polytetrafluoroethylene (Teflon), FR-4, FR-1, CEM-1 or CEM-3. Well known pre-preg materials used in the PCB industry are FR-2 (phenolic cotton paper), FR-3 (cotton paper and epoxy), FR-4 (woven glass and epoxy), FR-5 (woven glass and epoxy), FR-6 (matte glass and polyester), G-10 (woven glass and epoxy), CEM-1 (cotton paper and epoxy), CEM-2 (cotton paper and epoxy), CEM-3 (non-woven glass and epoxy), CEM-4 (woven glass and epoxy), CEM-5 (woven glass and polyester). Thermal expansion is an important consideration especially with ball grid array (BGA) and naked die technologies, and glass fiber offers the best dimensional stability.

Question: What's the common name of polytetrafluoroethylene?
Answer: Teflon

Question: What pre-preg material is designated by "FR-2"?
Answer: phenolic cotton paper

Question: To what type of packaging is thermal expansion particularly critical?
Answer: ball grid array

Question: What material delivers optimum dimensional stability?
Answer: glass fiber

Question: What dielectric is matte glass and polyester?
Answer: FR-6

Question: Thermal closure is an important what?
Answer: Unanswerable

Question: There is only one dielectric that can be chosen to do what?
Answer: Unanswerable

Question: FR-A is one of the what?
Answer: Unanswerable

Question: The ball gasket array (BGA) is an important what?
Answer: Unanswerable