One aspect is a method of coupling a feedthrough assembly to a surrounding case of an implantable medical device. An insulator having a plurality of conducting elements extending therethrough is provided. The insulator is placed with conducting elements within an opening of a case, thereby defining a narrow space between the insulator and the case. A braze preform is placed adjacent the insulator and case in the narrow space. The insulator is heated with a laser until raising the temperature of the adjacent preform above its melting point such that it fills the space between the insulator and the case.