Surface-mount type switching power supply unit and mounting method for the same

Abstract

A transformer of a switching power-supply circuit is placed and mounted nearly in the middle area of a circuit board. The transformer is of a low-profile type, and a broad and flat upper surface of the transformer functions as a suction surface for a suction nozzle. When a surface-mount type switching power-supply unit is mounted in a mother board, firstly, the upper surface of the above transformer is held by the suction nozzle, the surface-mount type switching power-supply unit is transferred to a target mounting area on the mother board by the suction nozzle, and the surface-mount type switching power-supply unit is surface mounted in the mother board. Because it is not required to provide a nozzle suction surface for the suction nozzle's exclusive use, transfer molding is not needed, and accordingly a low-profile and low-cost surface-mount type switching power-supply unit can be facilitated.

What is claimed is:  
     
         1 . A surface-mount type switching power-supply unit comprising: 
 a circuit board; and    a switching power-supply circuit including a transformer provided on the circuit board,    wherein a substantially flat nozzle suction surface to be held by a suction nozzle for transferring the surface-mount type switching power-supply unit is provided as an upper portion of the transformer mounted on the circuit board.    
     
     
         2 . The surface-mount type switching power-supply unit as claimed in  claim 1 , wherein the nozzle suction surface of the transformer is nearly parallel to a board surface of the circuit board.  
     
     
         3 . The surface-mount type switching power-supply unit as claimed in  claim 1 , wherein protruding terminals are formed in the transformer, a through-hole portion for placing the transformer is provided in the circuit board and connection pads are formed at a periphery of the through-hole portion, the transformer is placed in the through-hole portion, the terminals are connected to the connection pads, and the transformer is thereby mounted to the circuit board.  
     
     
         4 . The surface-mount type switching power-supply unit as claimed in  claim 2 , wherein protruding terminals are formed in the transformer, a through-hole portion for placing the transformer is provided in the circuit board and connection pads are formed at a periphery of the through-hole portion, the transformer is placed in the through-hole portion, the terminals are connected to the connection pads, and the transformer is thereby mounted to the circuit board.  
     
     
         5 . The surface-mount type switching power-supply unit as claimed in  claim 1 , wherein the transformer comprises a coil pattern portion formed in or on the circuit board and core materials, core-pin insertion through-holes are formed in an area where the coil pattern portion is formed in or on the circuit board, and the core materials are mounted adjacent the coil pattern of the circuit board by leg portions of the core materials inserted into the core-pin insertion through-holes.  
     
     
         6 . The surface-mount type switching power-supply unit as claimed in  claim 2 , wherein the transformer comprises a coil pattern portion formed in or on the circuit board and core materials, core-pin insertion through-holes are formed in an area where the coil pattern portion is formed in or on the circuit board, and the core materials are mounted adjacent the coil pattern of the circuit board by leg portions of the core materials inserted into the core-pin insertion through-holes.  
     
     
         7 . The surface-mount type switching power-supply unit as claimed in  claim 5 , wherein the upper portion of the core materials comprises the flat nozzle suction surface.  
     
     
         8 . The surface-mount type switching power-supply unit as claimed in  claim 6 , wherein the upper portion of the core materials comprises the flat nozzle suction surface.  
     
     
         9 . The surface-mount type switching power-supply unit as claimed in  claim 1 , wherein the transformer is arranged at the approximate center of gravity of the surface-mount type switching power-supply unit.  
     
     
         10 . The surface-mount type switching power-supply unit as claimed in claim  2 , wherein the transformer is arranged at the approximate center of gravity of the surface-mount type switching power-supply unit.  
     
     
         11 . The surface-mount type switching power-supply unit as claimed in  claim 3 , wherein the transformer is arranged at the approximate center of gravity of the surface-mount type switching power-supply unit.  
     
     
         12 . The surface-mount type switching power-supply unit as claimed in  claim 5 , wherein the transformer is arranged at the approximate center of gravity of the surface-mount type switching power-supply unit.  
     
     
         13 . The surface-mount type switching power-supply unit as claimed in  claim 7 , wherein the transformer is arranged at the approximate center of gravity of the surface-mount type switching power-supply unit.  
     
     
         14 . The surface-mount type switching power-supply unit as claimed in  claim 1 , wherein components comprising the switching power-supply circuit board are exposed without molding resin on a surface of the surface-mount type switching power-supply unit.  
     
     
         15 . The surface-mount type switching power-supply unit as claimed in  claim 2 , wherein components comprising the switching power-supply circuit board are exposed without molding resin on a surface of the surface-mount type switching power-supply unit.  
     
     
         16 . The surface-mount type switching power-supply unit as claimed in  claim 3 , wherein components comprising the switching power-supply circuit board are exposed without molding resin on a surface of the surface-mount type switching power-supply unit.  
     
     
         17 . The surface-mount type switching power-supply unit as claimed in  claim 5 , wherein components comprising the switching power-supply circuit board are exposed without molding resin on a surface of the surface-mount type switching power-supply unit.  
     
     
         18 . The surface-mount type switching power-supply unit as claimed in  claim 7 , wherein components comprising the switching power-supply circuit board are exposed without molding resin on a surface of the surface-mount type switching power-supply unit.  
     
     
         19 . The surface-mount type switching power-supply unit as claimed in  claim 9 , wherein components comprising the switching power-supply circuit board are exposed without molding resin on a surface of the surface-mount type switching power-supply unit.  
     
     
         20 . A mounting method for a surface-mount type switching power-supply unit in which an upper surface of a transformer comprises a substantially flat nozzle suction surface, comprising the steps of: 
 applying suction to the upper surface of the transformer of the surface-mount type switching power-supply unit with a suction nozzle;    transferring the surface-mount type switching power-supply unit to a target mounting area of a mother board by the suction nozzle; and    surface mounting the surface-mount type switching power-supply unit to the mother board.    
     
     
         21 . The method of claim  20 , further comprising mounting the transformer at a location on a circuit board of the surface-mount type switching power supply unit so that the transformer is at approximately the center of gravity of the surface-mount type switching power-supply unit.