Circuit board

A method of manufacturing a circuit board, the method comprising:

• providing a base board having a circuit and a terminal, the circuit and terminal being separate non-overlapping areas;
• forming a circuit pattern on an upper surface of the base board;
• forming a low-melting-metal layer directly on an upper surface of the circuit pattern which includes
• a first low-melting-metal layer above the circuit,
• a second low-melting-metal layer above the terminal, the terminal being only a portion configured to electrically connect the circuit pattern and an external device and having a globular shape, and
• a third low-melting-metal layer above the circuit, and between first low-melting-metal layer and the second low-melting-metal layer;
• and
• forming a soldering portion by heat-treating the second low-melting-metal layer and third low-melting-metal layer, a melted portion of the third low-melting-metal layer flows into the second low-melting-metal layer, and the heat-treated third low-melting-metal layer has a continuously inclined surface with a lower end at the second low-melting-metal layer and a higher end at the first low-melting-metal layer, the higher end being co-planar with a connecting plane of the first low-melting-metal layer, the connecting plane of the first low-melting-metal layer being lower than a highest plane of the second low-melting-metal layer, the first low-melting-metal layer having a greater overall length on the circuit pattern than an overall length of the second low-melting-metal layer and an overall length of the third low-melting-metal layer on the circuit pattern,
• wherein the circuit corresponds to a circuit of the circuit board, and the terminal is configured to electrically connect the circuit board to other devices, and
• wherein the low-melting-metal layer is made of a metal melted in a temperature range of 100° C. and 250° C.