the heat producing component 117 and a surface of the second heat sink component 32 opposite to the electronic component 11 furthermore the distance between the first conducting portions 318 and the first heat transferring portion 312 is larger than the distance of the concave portion 3121 and the first heat transferring portion 312 the second heat sink component 32 is arranged between the bottom plate 130 and the electronic component 11 a second connecting portion 321 and a plurality of spaced second conducting portions 323 are formed on the second heat sink component 32 the second connecting portion 321 corresponds to the first connecting portion 316 for engaging with the first connecting portion 316 to fix the first heat sink component 31 with the second heat sink component 32 each second conducting portion 323 defines a second through hole 324 the shape of the second conducting portions 323 corresponds to and engages with the first conducting portions 318 respectively in the embodiment the area of the second conduction component 32 is larger than the area of the second heat transferring portion 314 referring to fig4 in assembly the second heat sink component 32 is mounted on the bottom plate 130 with the second fixing portion 321 and the second conducting portions 323 toward the top plate 120 the electronic component 11 is mounted on the second heat sink component 32 with the heat producing component 117 opposite to.