Patent ID: 8569632

Claim:
A circuit board, comprising; a substrate having a hole having a diameter of 23 μm or less, and an aspect ratio of 5 or more; and a wiring formed inside the hole, wherein the wiring is made of a lead free solder alloy having a melting point of 100 to 600° C., the solder alloy consisting of tin (Sn), bismuth (Bi), indium (In) and gallium (Ga), wherein the wiring includes a polycrystalline region of the solder alloy, the wiring includes little voids, wherein the tin (Sn) is included in the solder alloy at 30 to 80 wt %, and the bismuth (Bi) is included in the solder alloy at 20 to 58 wt %, and indium (In) is included in the solder alloy at 3 to 10 wt %, and gallium (Ga) is included in the solder alloy at 0.001 to 1 wt %.