Flexible printed circuit board

Abstract

There is provided a flexible printed circuit board. The flexible printed circuit board includes: a flexible insulation layer having a first surface and a second surface; a first land which is conductive and which is provided on the first surface of the flexible insulation layer; and a conductive member which is provided on the second surface of the flexible insulation layer. A recess is formed on the first land.

What is claimed is: 
     
         1 . A flexible printed circuit board comprising:
 an insulation layer which has a first surface and a second surface, and in which a through hole connecting the first surface and the second surface is formed;   a metallic first land which is provided on the first surface and which is provided around an opening in the first surface defined by the through hole;   a metallic second land which is provided on the second surface and which is provided around an opening in the second surface defined by the through hole, the insulation layer being sandwiched by the metallic first land and the metallic second land; and   a metallic connecting portion provided in the through hole to connect the metallic first land and the metallic second land,   wherein a channel which connects the through hole and an outside of the metallic first land so that the through hole and the outside of the metallic first land are in fluid communication with each other is formed at a position lower than a top of the metallic first land.   
     
     
         2 . The flexible printed circuit board according to  claim 1 , wherein the metallic connecting portion is provided on an inner circumferential surface of the through hole. 
     
     
         3 . The flexible printed circuit board according to  claim 2 , wherein the metallic connecting portion is provided on an entire region of the inner circumferential surface of the through hole. 
     
     
         4 . The flexible printed circuit board according to  claim 1 , wherein the metallic connecting portion covers a side surface of the insulation layer, the side surface defining the through hole. 
     
     
         5 . The flexible printed circuit board according to  claim 1 , wherein the metallic first land is a disk-shaped member which covers the through hole, and the channel is a slit which extends in a radial direction of the disk shaped member and which divides the disk-shaped member into two parts. 
     
     
         6 . The flexible printed circuit board according to  claim 1 , wherein the flexible printed circuit board is a flexible printed circuit board to be soldered to a counterpart electrode with a heater, the top of the metallic first land is a contact surface to which a heating surface of the heater is brought into contact, and in a case that the heating surface of the heater is in contact with the contact surface of the metallic first land, an air in the through hole is released to the outside of the metallic first land through the channel. 
     
     
         7 . The flexible printed circuit board according to  claim 1 , wherein the channel is a groove. 
     
     
         8 . The flexible printed circuit board according to  claim 1 , wherein a solder escape portion is provided on a wiring connected to the metallic second land. 
     
     
         9 . The flexible printed circuit board according to  claim 1 , wherein the metallic first land in which the channel is formed includes a plurality of lands disposed in a zigzag pattern. 
     
     
         10 . The flexible printed circuit board according to  claim 9 , wherein the channels of the lands are formed as grooves, and
 two lines respectively extending along longitudinal directions of the grooves of two adjacent lands do not overlap with each other.