In a message dated 11/8/01 12:40:03 PM Central Standard Time, [log in to unmask] writes: Graham, It's not for the operating temperatures but for the assembly temperatures. Larry Tawyea > Hello Technet > A question for bare board gurus. Is there a difference in reliability > between high Tg and regular Tg FR-4 ( IPC-4101/24 vs IPC-4101/21) in a > vehicle type application? > The end use application is less than Tg of /21 material, so not in the > glass transition range for either material. > > Typically - is the CTE different between these two? (I expect that depends > on the manufacturer to some degree). If there isn't a high temperature > operating requirement, why select the high temp FR-4? > > Thanks! > > > > regards, > > Graham Collins >