| 摘要 |
Conductive or solder bumps are stacked between a mounted component such as a BGA device and a printed wiring substrate in a multileveled printed circuit board unit. An interposer or relay substrate is interposed between the adjacent stacked conductive bumps. The interposer substrate is made of a porous material. When any difference in the expansion is caused between the printed wiring substrate and the mounted component, one side of the interposer substrate receives a relatively smaller displacement force while the other side of the interposer substrate receives a relatively larger displacement force. A shearing stress is induced in the interposer substrate. Deformation of the porous material serves to absorb the shearing stress in the interposer substrate. The conductive bumps bonded on one side of the interposer substrate as well as the conductive bumps bonded on the other side of the interposer substrate may be relieved from a shearing stress. Accordingly, the durability of the conductive bumps can be improved. The conductive bumps are allowed to keep a stronger bonding in a longer duration. |
