Abstract: An aluminum coil assembly includes: a steel housing; an aluminum electromagnetic coil electrically connected to the steel housing and having an aluminum lead coil and a copper ground coil connected to the aluminum lead coil by means of soldering or a terminal; and a brass ground ring adapted to be press-fitted to a ring hole formed on the steel housing and having a ground hole formed on the center thereof in such a manner as to insert the copper ground coil connected to the aluminum lead coil thereinto, a cylindrical portion having a cut line adapted to be reduced when coupled to the ring hole of the steel housing to support the copper ground coil inserted into the ground hole, and an inclined portion formed on the underside of the cylindrical portion to allow easy press-fitting to the ring hole formed on the steel housing.