Residual stress analysis in actively brazed joints of aluminium nitride and copper using neutron and X-ray diffraction

Thin plates of AIN were joined with Cu sheets by active brazing, and the re sidual stresses generated by the brazing process were investigated by neutr on and X-ray diffraction. Residual stresses with values between 100 MPa and - 150 MPa were found in the ceramic layers. The residual stresses in the C u layers had to be inferred from the balance of forces, because coarse grai n effects and a strong variation of the stress-free lattice constant across the thickness due to interdiffusion of the brazing metal and the Cu layer did not allow to obtain reliable residual stress values by diffraction meth ods. The results are discussed with regard to failure of the joints due to cracking.