A solder composition for use in solder joints of printed circuit boards (PCBs), including a compound layer comprising an alloy of bismuth and tin; and a graphene coating positioned on the compound layer.

A solder composition for use in solder joints of printed circuit boards (PCBs), including a compound layer comprising an alloy of bismuth and tin; and a graphene coating positioned on the compound layer.

With the increasing density of in-vehicle electronic circuits, not only conventional cracks at bonding interfaces such as between the substrate and the solder attachment site or a component and the solder attachment site but also novel cracking problems of cracks occurring in the Sn matrix in the interior of the bonded solder have appeared. To solve the above problem, a lead-free solder alloy with 1-4 mass % Ag, 0.6-0.8 mass % Cu, 1-5 mass % Sb, 0.01-0.2 mass % Ni and the remainder being Sn is used. A solder alloy, which not only can withstand harsh temperature cycling characteristics from low temperatures of −40° C. to high temperatures of 125° C. but can also withstand external forces that occur when riding up on a curb or colliding with a vehicle in front for long periods, and an in-vehicle electronic circuit device using the solder alloy can thereby be obtained.

With the increasing density of in-vehicle electronic circuits, not only conventional cracks at bonding interfaces such as between the substrate and the solder attachment site or a component and the solder attachment site but also novel cracking problems of cracks occurring in the Sn matrix in the interior of the bonded solder have appeared. To solve the above problem, a lead-free solder alloy with 1-4 mass % Ag, 0.6-0.8 mass % Cu, 1-5 mass % Sb, 0.01-0.2 mass % Ni and the remainder being Sn is used. A solder alloy, which not only can withstand harsh temperature cycling characteristics from low temperatures of −40° C. to high temperatures of 125° C. but can also withstand external forces that occur when riding up on a curb or colliding with a vehicle in front for long periods, and an in-vehicle electronic circuit device using the solder alloy can thereby be obtained.

A solder alloy includes 1.1% by mass or more and 8% by mass or less of Cu; 6% by mass or more and 20% by mass or less of Sb; 0.01% by mass or more and 0.5% by mass or less of Ni; and 0.001% by mass or more and 1% by mass or less of Co; a balance being Sn. An amount of Cu (% by mass) and an amount of Ni (% by mass) satisfies following formula: the amount of Ni/(the amount of Cu+the amount of Ni)<0.10.

A solder alloy includes 1.1% by mass or more and 8% by mass or less of Cu; 6% by mass or more and 20% by mass or less of Sb; 0.01% by mass or more and 0.5% by mass or less of Ni; and 0.001% by mass or more and 1% by mass or less of Co; a balance being Sn. An amount of Cu (% by mass) and an amount of Ni (% by mass) satisfies following formula: the amount of Ni/(the amount of Cu+the amount of Ni)<0.10.

Provided is a high-temperature lead-free solder alloy having excellent tensile strength and elongation in a high-temperature environment of 250° C. In order to make the structure of an Sn—Sb—Ag—Cu solder alloy finer and cause stress applied to the solder alloy to disperse, at least one material selected from the group consisting of, in mass %, 0.003 to 1.0% of Al, 0.01 to 0.2% of Fe, and 0.005 to 0.4% of Ti is added to a solder alloy containing 35 to 40% of Sb, 8 to 25% of Ag, and 5 to 10% of Cu, with the remainder made up by Sn.

Provided is a high-temperature lead-free solder alloy having excellent tensile strength and elongation in a high-temperature environment of 250° C. In order to make the structure of an Sn—Sb—Ag—Cu solder alloy finer and cause stress applied to the solder alloy to disperse, at least one material selected from the group consisting of, in mass %, 0.003 to 1.0% of Al, 0.01 to 0.2% of Fe, and 0.005 to 0.4% of Ti is added to a solder alloy containing 35 to 40% of Sb, 8 to 25% of Ag, and 5 to 10% of Cu, with the remainder made up by Sn.

A solder alloy contains 0.5 mass % or more and 1.25 mass % or less of Sb, In which satisfies 5.5≦[In]≦5.50+1.06[Sb] in a case of 0.5≦[Sb]≦1.0; and 5.5≦[In]≦6.35+0.212[Sb] in a case of 1.0<[Sb]≦1.25 (in the expression, [Sb] indicates the Sb content percentage (mass %) and [In] indicates the In content percentage (mass %)), 0.5 mass % or more and 1.2 mass % or less of Cu, 0.1 mass % or more and 3.0 mass % or less of Bi, and 1.0 mass % or more and 4.0 mass % or less of Ag. The remainder is formed from Sn.

A solder alloy contains 0.5 mass % or more and 1.25 mass % or less of Sb, In which satisfies 5.5≦[In]≦5.50+1.06[Sb] in a case of 0.5≦[Sb]≦1.0; and 5.5≦[In]≦6.35+0.212[Sb] in a case of 1.0<[Sb]≦1.25 (in the expression, [Sb] indicates the Sb content percentage (mass %) and [In] indicates the In content percentage (mass %)), 0.5 mass % or more and 1.2 mass % or less of Cu, 0.1 mass % or more and 3.0 mass % or less of Bi, and 1.0 mass % or more and 4.0 mass % or less of Ag. The remainder is formed from Sn.