Manufacturing method of opto-electric hybrid flexible printed circuit board and opto-electric hybrid flexible printed circuit board

A manufacturing method of an opto-electric hybrid flexible printed circuit board, the opto-electric hybrid flexible printed circuit board including a flexible printed circuit board having a first principal surface and a second principal surface on an opposite side to the first principal surface;

• a flexible optical waveguide provided along the first principal surface of the flexible printed circuit board and made of organic polymer;
• and a surface light-emitting element and a surface light-receiving element both of which are implemented on the second principal surface of the flexible printed circuit board, the method comprising:
• a step of pasting a first flexible cladding layer with a flexible core layer;
• a step of forming a core, by patterning the flexible core layer, such that a width of one end of the core is larger than that of a light-emitting part of the surface light-emitting element and that a width of other end of the core is smaller than that of a light-receiving part of the surface light-receiving element;
• a step of producing the flexible optical waveguide by pasting a second flexible cladding layer on the first cladding layer so as to cover the core;
• a step of pasting the flexible optical waveguide at a predetermined position on the first principal surface of the flexible printed circuit board via an adhesive sheet;
• a mirror forming step of respectively forming, at the one end and the other end of the core, a first optical path converting mirror and a second optical path converting mirror each of which converts an optical path of signal light due to light reflection on an end face by processing the flexible optical waveguide pasted with the flexible printed circuit board;
• a first ultrasonic bonding step, performed after the mirror forming step, of implementing the surface light-emitting element on the flexible printed circuit board such that the signal light emitted from the light-emitting part of the surface light-emitting element is reflected by the first optical path converting mirror and propagates in the core;
• and
• a second ultrasonic bonding step, performed after the mirror forming step, of implementing the surface light-receiving element on the flexible printed circuit board such that the signal light reflected by the second optical path converting mirror is incident on the light-receiving part of the surface light-receiving element, wherein
• in the first ultrasonic bonding step, an ultrasonic wave traveling along a width direction of the core is applied to the surface light-emitting element while pressure in a thickness direction is exerted on the surface light-emitting element placed at a predetermined position on the flexible printed circuit board, thereby electrically connecting a first electrode of the surface light-emitting element, which is provided on the same face as that of the light-emitting part, to a first pad provided on the second principal surface of the flexible printed circuit board,
• in the second ultrasonic bonding step, the ultrasonic wave traveling along the width direction of the core is applied to the surface light-receiving element while the pressure in the thickness direction is exerted on the surface light-receiving element placed at a predetermined position on the flexible printed circuit board, thereby electrically connecting a second electrode of the surface light-receiving element, which is provided on the same face as that of the light-receiving part, to a second pad provided on the second principal surface of the flexible printed circuit board.