Investigation on the mechanism responsible for degradation on Cu/Kapton foils

Andy Wu

The degraded Foil

SEM Images of Spot A

SEM Image of Part of Spot B

EDX Observations at 25kV (A)

Typical Spectrum for Spots A and B

Typical EDX Spectrum at 25kV (open window)

Typical Open Window Spectrum for Spots A&B

Typical EDX Spectrum at 10 KV (surface)

Typical Open Window Spectrum at 10 kV for Spots A&B

Conclusion

• The surfaces of the degraded spots are covered by a thin layer of copper oxides. The thickness of the layer is much below 1 μm.

Composition of Granite

SiO 72.04%, Al2O3 14.42%, K2O 4.12%, Na2O 3.69%, CaO 1.82%, FeO 1.68%, Fe2O3 1.22%, MgO 0.71%, TiO2 0.30%, P2O5 0.12%, MnO 0.05%

Possible degradation mechanism

• Evaporation of the DI water used to mediate the contact between Cu/Kapton foil and granite leads to several highly localized small area where active oxygen can reach certain level to be reactive to Cu. The active oxygen can come either from granite or possible residues from the manufacturer as one can see that the surface of the as received foil has discolored spots.

Recommended Remedy

• Seal the granite table to prevent the formation of some localized water spots.

• Ask the manufacturer to do a better job on cleaning the Cu/Kapton foils