be upper and lower surfaces 100 a and 100 b respectively here the lower surface 100 b represents a surface facing the surface of the circuit board 301 and the upper surface 100 a represents the surface opposite to the lower surface 100 b referring to fig3 and 4 which are top and bottom plan views of the package module according to the invention respectively the upper surface 100 a of the substrate 100 has a die region 101 a and the lower surface 100 b of the substrate 100 has a die region 101 b and thermal channel regions 101 c typically the die regions 101 a and 101 b are substantially at the center of the substrate 100 unlike the conventional package substrate the lower surface 100 b of the substrate 100 has thermal channel regions 101 c outwardly extending to the edges or corners of the substrate 100 from the die region 101 b for example the thermal channel regions 101 c outwardly extend to two opposing edges of the substrate 100 respectively from two opposing edges of the rectangular die region 101 b as shown in fig4 in another embodiment the thermal channel regions 101 c may outwardly extend to four corners of the substrate 100 respectively from four corners of the rectangular die region 101 b as shown in fig5 it will be apparent to those skilled in the art that the substrate.