Kabushiki Kaisha Toshiba

Ken Iwasaki

Morihiko Ikemizu

Nobuaki Oie

The electronic device has a structure that a semiconductor package is mounted on a mother board. To relieve stress caused by cyclic thermal load and applied to solder bumps that are electrically and mechanically connect the semiconductor package and the mother board, a shape-holding plate (stiffener) adhered to a wiring film is composed of a metal with a thermal expansion coefficient of 13.times.10.sup.-6 to 17.times.10.sup.-6 almost close to that of a glass-epoxy wiring substrate as the mother board. Examples of the metal are 25Cr-20Ni stainless steel or copper alloy containing 0.01 to 0.03% by weight of Zr.

Electronic device and semiconductor package

The electronic device has a structure that a semiconductor package (10) is mounted on a motherboard (21), and a buffer layer (41) for relieving a stress, which is produced due to a difference of physical properties between the semiconductor package (10) and the motherboard (21), is mounted on the electrical and mechanical interface between the semiconductor package (10) and the motherboard (21). For example, the buffer layer (41) having a thermal expansion coefficient close to that of the motherboard (21) is formed on a face of the semiconductor package 10 having an external connecting terminals (12b) mounted. A stress caused due to a difference between a thermal expansion coefficient of a wiring substrate (12) of the semiconductor package and that of the motherboard (21) can be relieved by the buffer layer (41). Therefore, a cyclic stress applied to the connection between the semiconductor package and the motherboard in the actual application environment can be relieved, and reliability of connection can be improved. Thus, a semiconductor package mountable with a high degree of reliability and an electronic device having a high degree of reliability is provided.

Growing community of inventors

Yokohama, Japan

Ken Iwasaki