Circuit boards are treated by heating a stack of themunder

Chapter 5, Problem 5.46

(choose chapter or problem)

Circuit boards are treated by heating a stack of themunder high pressure, as illustrated in 5.45. Theplatens at the top and bottom of the stack are main-tained at a uniform temperature by a circulating fluid.The purpose of the pressingheating operation is tocure the epoxy, which bonds the fiberglass sheets, andimpart stiffness to the boards. The cure condition isachieved when the epoxy has been maintained at orabove 170C for at least 5 min. The effective thermo-physical properties of the stack or book(boardsand metal pressing plates) are k?0.613 W/m?K and?cp?2.73106J/m3?K.(a) If the book is initially at 15C and, following appli-cation of pressure, the platens are suddenly brought to a uniform temperature of 190C, calculate theelapsed time terequired for the midplane of thebook to reach the cure temperature of 170C.(b) If, at this instant of time, t?te, the platen tempera-ture were reduced suddenly to 15C, how muchenergy would have to be removed from the book bythe coolant circulating in the platen, in order toreturn the stack to its initial uniform temperature?