Abstract: A through hole 2 in a circuit board 1 and to be joined to a lead 5 in a surface mounting component 6 is prepared from a material such as nickel, and palladium having a thermal conductivity equal to or less than 100 W/m.K, the circuit board 1 involving a alloy layer composed of at least a member selected from elements of solder 8, a pad 7, and the lead 5 in a solder joined site of the lead 5 and the pad 7, whereby a quantity of heat transmitted to the joined site via the through hole 2 is reduced at the time when wave-soldering is applied to the back of the circuit board 1 after the surface mounting component 6 was mounted, so that the joined site is maintained at a temperature equal to or less than a melting point of the alloy layer, and hence, exfoliation in an interface of the joined site is prevented, and reliability in the joint of the lead 5 and the pad 7 is elevated.

Abstract: The present invention provides a board ensuring no peel-off of a wall and a land, even if a part is soldered to the board with lead-free solder. The board 10 is comprised of N (N?3) layer patterns electrically insulated from one another, and is formed with a through-hole 14 into which an electrode 19 of an electronic part 18 is to be inserted. An external land 15 is formed on a surface of each of the first and N-th layer patterns. An electrically conductive layer 17 is formed on an inner wall of the through-hole 14 such that the electrically conductive layer is electrically connected to the external land 15 of each of the first and N-th layer patterns. The electronic part 18 is fixed in the through-hole 14 with lead-free solder 20 filled in the through-hole 14. At least one internal land 16 extending from the electrically conductive layer 17 is formed in the same layer as a M-th layer pattern (2?M?(N?1)). The internal land 16 is not electrically connected to the M-th layer pattern.

Abstract: The present invention provides a board ensuring no peel-off of a wall and a land, even if a part is soldered to the board with lead-free solder. The board 10 is comprised of N (N≧3) layer patterns electrically insulated from one another, and is formed with a through-hole 14 into which an electrode 19 of an electronic part 18 is to be inserted. An external land 15 is formed on a surface of each of the first and N-th layer patterns. An electrically conductive layer 17 is formed on an inner wall of the through-hole 14 such that the electrically conductive layer is electrically connected to the external land 15 of each of the first and N-th layer patterns. The electronic part 18 is fixed in the through-hole 14 with lead-free solder 20 filled in the through-hole 14. At least one internal land 16 extending from the electrically conductive layer 17 is formed in the same layer as a M-th layer pattern (2≦M≦(N-1)). The internal land 16 is not electrically connected to the M-th layer pattern.

Abstract: A through hole 2 in a circuit board 1 and to be joined to a lead 5 in a surface mounting component 6 is prepared from a material such as nickel, and palladium having a thermal conductivity equal to or less than 100 W/m.K, the circuit board 1 involving a alloy layer composed of at least a member selected from elements of solder 8, a pad 7, and the lead 5 in a solder joined site of the lead 5 and the pad 7, whereby a quantity of heat transmitted to the joined site via the through hole 2 is reduced at the time when wave-soldering is applied to the back of the circuit board 1 after the surface mounting component 6 was mounted, so that the joined site is maintained at a temperature equal to or less than a melting point of the alloy layer, and hence, exfoliation in an interface of the joined site is prevented, and reliability in the joint of the lead 5 and the pad 7 is elevated.

Abstract: In a circuit board having lands 2 each of which has a through hole 4 through which a lead of an electrical part is inserted, the lead 3 and the land 2 being mounted in the circuit board by using lead-free solder 6, the width of the land 2 corresponding to the difference in radius between the land 2 and the through hole 4 is set to about 0.40 mm or more. The width of the land 2 is set to such a value that the land exfoliation due to the solidification/shrinkage of the lead-free solder 6 and the shrinkage of the circuit board in the thickness direction can be prevented. The circuit board 1 has circuit wires at least on both the surface and the back surface.

Abstract: In a circuit board having lands 2 each of which has a through hole 4 through which a lead of an electrical part is inserted, the lead 3 and the land 2 being mounted in the circuit board by using lead-free solder 6, the width of the land 2 corresponding to the difference in radius between the land 2 and the through hole 4 is set to about 0.40 mm or more. The width of the land 2 is set to such a value that the land exfoliation due to the solidification/shrinkage of the lead-free solder 6 and the shrinkage of the circuit board in the thickness direction can be prevented. The circuit board 1 has circuit wires at least on both the surface and the back surface.