| abstract |
Designating the maximum length of the heat sink as L, and the amount of warp of the heat sink as Z, the amount of warp Z arising from deformation of the metal layer to produce a concave shape of the joining surface of the heat sink being a positive value, and the amount of warp Z arising from deformation to produce a convex shape of the joining surface being a negative value, the ratio Z/L of the maximum length L and the amount of warp Z measured at 25°C is within the range -0.005 to 0.005, inclusive, and the ratio Z/L stays within the range -0.005 to 0.005, inclusive even when heated to 280°C, and when cooled down to 25°C subsequent to this heating. |