Hydraulic Bulge Test of Electrodeposited Copper Foil

SUMMARY

The 18 pm to 72 μ thick commercial electrodeposited copper foils GR I and GR 3, the experimentalfoil TCAM and the commercial rolled foil GR 8 are tested in bulge and in tension at temperatures up to 300°C. Utilizing the bulge data, pressure and deflection at rupture, the through-thickness fracture stress (σ,) and fracture strain (€) are calculated and compared to the corresponding average tensile values σ_av and €_av. The effects of foil thickness, orifice size and test temperature on σ¹ and €₁ are characterized. In many instances approximately one-to-one correspondence exists between σ₁, €_ε and σ_av; €_avthere are, however, significant exceptions due to texture hardening, thermal embrittlement and grain pancaking. The extent of embrittlement is greatest for the GR 1 foil, increasing with the foil thickness: it is virtually- non-existent for the (rolled) GR 8 foil. Thermal annealing overshadows the embrittlement effects for the GR 3 foil. The TCAM foil embrittles modestly but displays poor resistance to thinning at room temperature; however, the resistance improves markedly with increasing test temperature.

Keywords:

• Copper Foil
• Electrodeposit
• Bulge Test
• Embrittlement
• Thinning Resistance