Effect of radiation and temperature on resonance properties of polyurethane-coated wire bonds.

Thin polyurethane (PU) coatings for aluminumwedge wire bonds are proposed to protect the ATLAS Inner Tracker upgrade from oscillations from periodic Lorentz forces and condensation-induced corrosion. Coating robustness after exposure to lifetime doses expected by parts of a tracking detector at the High Luminosity-Large Hadron Collider has been evaluated. Mechanical properties of irradiated samples were tested at room temperature and at -20 degrees C. Irradiated samples were thermal-cycled to test for radiation-induced intolerance to thermal expansion. Mechanical vibrations of PU-coated wire bonds (99% aluminum, 1% silicon, 25 mu m diameter) were excited with 50% duty-cycle square wave currents in a 1.0 T field. The most vulnerable endcap disk geometry (magnetic field perpendicular to the wire bond and parallel to the normal of its PC board) was used. Resonance characteristics have been measured up to anticipated lifetime doses.