A backlight unit (BLU), comprising: a base substrate in which a light emitting area (LA) and a non-light emitting area (NLA) are defined; a wiring layer comprising: a lower conductive layer disposed on the base substrate ; an intermediate conductive layer disposed on the lower conductive layer ; and an upper conductive layer disposed on the intermediate conductive layer ; a coupling force between the lower conductive layer and the base substrate is greater than a coupling force between the intermediate conductive layer and the base substrate ; the upper conductive layer is made of a conductive material having better corrosion resistance than the intermediate conductive layer ; the intermediate conductive layer includes copper or a copper alloy; a light emitting element disposed on the wiring layer in the light emitting area (LA); a connection member (SR1, SR2) electrically connecting the light emitting element and the wiring layer , the connection member (SR1, SR2) contacting the intermediate conductive layer of the wiring layer and the light emitting element ; a backlight flexible substrate (FPC2) electrically connected to the wiring layer in the non-light emitting area (NLA); and a pad connection member (AP) electrically connecting the wiring layer and the backlight flexible substrate (FPC2) in the non-light emitting area (NLA), the pad connection member (AP) contacting the upper conductive layer of the wiring layer , wherein a coupling force between the connection member (SR1, SR2) and the intermediate conductive layer of the wiring layer is greater than a coupling force between the connection member (SR1, SR2) and the upper conductive layer . a base substrate in which a light emitting area (LA) and a non-light emitting area (NLA) are defined; a wiring layer comprising: a lower conductive layer disposed on the base substrate ; an intermediate conductive layer disposed on the lower conductive layer ; and an upper conductive layer disposed on the intermediate conductive layer ; a coupling force between the lower conductive layer and the base substrate is greater than a coupling force between the intermediate conductive layer and the base substrate ; the upper conductive layer is made of a conductive material having better corrosion resistance than the intermediate conductive layer ; the intermediate conductive layer includes copper or a copper alloy; a lower conductive layer disposed on the base substrate ; an intermediate conductive layer disposed on the lower conductive layer ; and an upper conductive layer disposed on the intermediate conductive layer ; a coupling force between the lower conductive layer and the base substrate is greater than a coupling force between the intermediate conductive layer and the base substrate ; the upper conductive layer is made of a conductive material having better corrosion resistance than the intermediate conductive layer ; the intermediate conductive layer includes copper or a copper alloy; a light emitting element disposed on the wiring layer in the light emitting area (LA); a connection member (SR1, SR2) electrically connecting the light emitting element and the wiring layer , the connection member (SR1, SR2) contacting the intermediate conductive layer of the wiring layer and the light emitting element ; a backlight flexible substrate (FPC2) electrically connected to the wiring layer in the non-light emitting area (NLA); and a pad connection member (AP) electrically connecting the wiring layer and the backlight flexible substrate (FPC2) in the non-light emitting area (NLA), the pad connection member (AP) contacting the upper conductive layer of the wiring layer , wherein a coupling force between the connection member (SR1, SR2) and the intermediate conductive layer of the wiring layer is greater than a coupling force between the connection member (SR1, SR2) and the upper conductive layer . <EOS>