pin 212 b connected to the base extension 212 a the thickness of the base extension 212 a is thinner than the thickness of the first base 111 and thus the base extension 212 a is encapsulated inside the plastic packaging body 160 only the bottom surface of the external pin 212 b is exposed from the bottom surface of the plastic packaging body 160 as shown in fig6 a the length of the fourth base 214 is shorter than the length of the third base 113 and the external pin 212 b is arranged on the same side as the fourth base 214 particularly the external pin 212 b and a plurality of pins 214 u2032 in the fourth base 214 are arranged on the same straight line the base extension 212 a extends under the primary packaging structure 130 until the solder bump 132 a 1 on the front surface of the primary packaging structure 130 superimposed on the base extension 212 a as such the conducting material 120 a is deposited for attaching the solder bumps 132 a 1 on the top surface of the base extension 212 a as shown in fig6 b 6c the top surface of the base extension 212 a and the top surface of the first base 111 are arranged on the same plane substantially so that the primary packaging structure 130 is easily mounted on the first base 111 and the base extension 212 a of the second base 212 the thickness of the base extension 212 a is thinner than the thickness of.