PRINTED BOARD AND ITS MANUFACTURE

PROBLEM TO BE SOLVED: To obtain an improved printed board on which such an accident as the cracking, stripping off, etc., of solder hardly occurs even when the coefficient of thermal expansion of electronic parts is different from that of the board and which can cope with the increase of the packing density of electronic parts. SOLUTION: The main part of a parts mounting section 30 is separated from a printed board 1 by providing a slit 3 so as to surround a pad train 20 connected to the wiring pattern 4 of a printed board 1 and the mounting section 30 is only supported by the pattern 4 and a base material section 13. The slit 3 is formed by irradiating a slit forming area (on the periphery of the mounting section 30) on the board 1 with a laser beam through a prescribed mask under a condition where only a base material can be selectively machined without giving any damages to the pattern 4. The mounting section 30 is supported on the substrate 1 through the pattern 4 and the base material 13 left under the pattern 4. Therefore, the connection reliability can be sufficiently improved even in the conventional example even when any special material which is selected by taking the difference of the coefficient of thermal expansion between mounted parts and the printed board 1 into consideration is used as the base material of the printed board 1.