| 摘要 |
Lifespan of LEDs can be lengthened, and the workability of the printed circuit board during circuit formation and during LED mounting can be improved. A metal base circuit board, having an insulating layer with a linear expansion coefficient of 60 ppm per degree C. or higher and 120 ppm per degree C. or lower, a metal foil provided on one side of the insulating layer, comprising a metal material with a linear expansion coefficient of 10 ppm per degree C. or higher and 35 ppm per degree C. or lower, a circuit portion and a non-circuit potion having a linear expansion coefficient of 10 ppm per degree C. or higher and 35 ppm per degree C. or lower, and a white film formed on top of the insulating layer, circuit portion, and non-circuit portion, the total sum of the areas of the non-circuit portion and the circuit portion on top of the insulating layer being 50% or higher and 95% or lower relative to the area of the metal foil, and the relation between the linear expansion coefficients of each of the materials being: linear expansion coefficient of insulating layer>linear expansion coefficient of metal foil>linear expansion coefficient of circuit portion and non-circuit portion.
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