Thermal effects in thin copper foil

The anneal response and high-temperature ductility for four commercial-grade 35-mum rolled (R: GR5) and electrodeposited (ED: GR1, GR3, and TCAM) copper foils, used for rigid and flexible printed circuits, are investigated. Using tensile and microhardness monitors, the anneal response is examined to 900degreesC for up to 300 min, and the high-temperature ductility is characterized to a 200degreesC test temperature. For comparison, the ED "control" foils, using deposition parameters identical to those for the commercial foils but without the additives usually introduced in the electrolyte, are also examined. The ED control foils thermally soften readily; the temperature range of softening decreases with the electrodeposition overvoltage (eta). For the commercial-grade foils, the proprietary additives help tailor thermal softening but cause severe disruption of anneal kinetics (TCAM) and embrittlement at (TCAM) and above (GR1, GR3) 23degreesC.