Abstract: 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.

Abstract: 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).

Abstract: A convolutionally-encoded quadrature frequency-modulation (CQFM) system of the present invention is a digital modulation system in which binary source data is encoded by a convolutional encoder with an encoding rate of r=1/2, quaternarized, and is then fed into a duobinary converter and a mod.4 mapper for subsequent quadrature frequency-modulation with a modulation index of h=1. The system has a soft-decision Viterbi decoder. This decoder has not only a symbol-metric calculator, a state-metric memory, a path-history memory, and ACS circuit, all used in an ordinary Viterbi decoding system, but also a signal location pointer, which is a memory indicating any one of the nominal signal points in a two-dimensional signal space and being updated in response to the selection of higher-likelihood by the ACS circuit.