Femtosecond Laser Direct Joining of Copper with Polyethylene Terephthalate

Abstract

We succeeded in directly joining Cu with polyethylene terephthalate (PET) using femtosecond laser pulses, which were focused through PET onto the Cu surface which was thermally adhered to PET prior to the laser irradiation. A maximum tensile strength of 5.5 MPa was obtained. X-ray photoelectron spectroscopic spectra of the fractured surface suggested the chemical bonding of Cu with PET. TEM images of the sample showed no voids or no cracks. They also showed the mechanical mixture of Cu with PET around the interface of the joint. We suggest that the ultrashort pulse width of the laser enables the direct joining of these dissimilar materials, thereby avoiding graphitization of the polymeric material.