Flexible printed circuit board with embedded optical waveguide structure

Patent metadata

Field	Value
Publication number	US-12446149-B2
Application number	US-202318373263-A
Country	US
Kind code	B2
Filing date	Sep 26, 2023
Priority date	Sep 26, 2023
Publication date	Oct 14, 2025
Grant date	Oct 14, 2025

Abstract

A flexible printed circuit board with embedded optical waveguide structure, including a photoelectric transmission unit, wherein the photoelectric transmission unit includes a flexible insulation layer, a first optoelectronic unit and a second optoelectronic unit embedded in the photoelectric transmission unit, at least one redistribution layer having at least one conductive structure stacked with the flexible insulation layer and electrically connected with the first optoelectronic unit and second optoelectronic unit, an optical waveguide structure stacked with the flexible insulation layer, a first metal bump and a second metal bump adjacent to the optical waveguide structure and in optical alignment respectively with the first optoelectronic unit and the second optoelectronic unit to provide reflection planes for optical signal, wherein first metal bump and second metal bump are solid structures made of the same material as the one of redistribution layer.

First claim

What is claimed is:

1. A flexible printed circuit board with embedded optical waveguide structure, comprising at least one photoelectric transmission unit, wherein each said photoelectric transmission unit comprises:
a flexible insulation layer;
a first optoelectronic unit embedded in said photoelectric transmission unit and configured to convert electrical signal into optical signal;
a second optoelectronic unit embedded in said photoelectric transmission unit and configured to convert optical signal into electrical signal;
at least one redistribution layer having at least one conductive structure stacked with said flexible insulation layer and electrically connected with said first optoelectronic unit and said second optoelectronic unit;
an optical waveguide structure stacked with said flexible insulation layer for transmitting optical signal;
a first metal bump adjacent to said optical waveguide structure and in optical alignment with said first optoelectronic unit to provide a reflection plane for optical signal;
a second metal bump adjacent to said optical waveguide structure and in optical alignment with said second optoelectronic unit to provide a reflection plane for optical signal; and
a first flexible cover layer covering on said first metal bump, said second metal bump and said optical waveguide structure;
wherein said first metal bump and said second metal bump are solid structures made of the same material as the one of said redistribution layer.

2. The flexible printed circuit board with embedded optical waveguide structure of claim 1 , wherein said reflection plane of said first metal bump is in optical alignment with a light-emitting position of said first optoelectronic unit, and said reflection plane of said second metal bump is in optical alignment with a light-receiving position of said second optoelectronic unit.

3. The flexible printed circuit board with embedded optical waveguide structure of claim 2 , wherein said redistribution layer further comprising at least one dielectric film between said flexible insulation layer and said conductive structure, and two openings are provided in said dielectric film, and said reflection planes of said first metal bump and said second metal bump are aligned respectively with said light-emitting position and said light-receiving position through said two openings.

4. The flexible printed circuit board with embedded optical waveguide structure of claim 1 , wherein a material of said reflection plane of said first metal bump and said second metal bump is the same as a material of inner structure of said first metal bump and said second metal bump.

5. The flexible printed circuit board with embedded optical waveguide structure of claim 1 , wherein a width of a base of said first metal bump and said second metal bump is 30-60 μm, and a height of said first metal bump and said second metal bump is 15-30 μm.

6. The flexible printed circuit board with embedded optical waveguide structure of claim 1 , wherein said first optoelectronic unit comprises a vertical cavity surface emitting laser (VCSEL) diode and a VCSEL driver.

7. The flexible printed circuit board with embedded optical waveguide structure of claim 1 , wherein said second optoelectronic unit comprises a photodiode and a transimpedance amplifier (TIA).

8. The flexible printed circuit board with embedded optical waveguide structure of claim 1 , further comprising underfill filling in gaps between said first optoelectronic unit, said second optoelectronic unit and said flexible insulation layer.

9. The flexible printed circuit board with embedded optical waveguide structure of claim 1 , further comprising a second flexible cover layer covering on the other side of said flexible insulation layer opposite to said first flexible cover layer.

10. The flexible printed circuit board with embedded optical waveguide structure of claim 1 , comprising a plurality of said photoelectric transmission units, wherein said photoelectric transmission units are laminated together with said first optoelectronic units at one end and said second optoelectronic units at the other end of said flexible printed circuit board.

11. The flexible printed circuit board with embedded optical waveguide structure of claim 10 , further comprising two connectors respectively at said two ends of said flexible printed circuit board, and said two connectors are electrically connected with said first optoelectronic units and said second optoelectronic units through the conductive structure of said redistribution layer.

12. The flexible printed circuit board with embedded optical waveguide structure of claim 1 , wherein said optical waveguide structure comprises optical waveguide cores and optical waveguide claddings around each said optical waveguide core, and a refractive index of said optical waveguide cores is greater than a refractive index of said optical waveguide claddings.

13. A method of manufacturing a flexible printed circuit board with embedded optical waveguide structure, comprising:
embedding a first optoelectronic unit and a second optoelectronic unit in a flexible insulation layer;
forming at least one redistribution layer having at least one conductive structure stacked with said first optoelectronic unit, said second optoelectronic unit and said flexible insulation layer;
forming a first metal bump, a second metal bump and an optical waveguide structure on a first flexible cover layer; and
bonding said first flexible cover layer on one side of said flexible insulation layer, said first optoelectronic unit and said second optoelectronic unit, wherein said optical waveguide structure is in optical alignment respectively with said first metal bump and said second metal bump on said first flexible cover layer;
wherein said first metal bump and said second metal bump are solid structures made of the same material as the one of said conductive structure of said redistribution layer.

14. The method of manufacturing a flexible printed circuit board with embedded optical waveguide structure of claim 13 , further comprising:
providing said first flexible cover layer, wherein said first flexible cover layer comprises an insulation layer and two metal claddings respectively on two sides of said insulation layer;
forming a patterned photoresist on one of said metal claddings, wherein said photoresist is provided with opening patterns of said first metal bump and said second metal bump;
performing an electroplating process to form said first metal bump and said second metal bump on said one of said metal claddings;
removing said patterned photoresist;
performing an etching process to remove said metal claddings exposed from said first metal bump and said second metal bump; and
forming said optical waveguide structure on said insulation layer between said first metal bump and said second metal bump.

15. The method of manufacturing a flexible printed circuit board with embedded optical waveguide structure of claim 14 , further comprising:
forming patterned photoresist on the other said metal claddings; and
performing an electroplating process to form circuit patterns on said the other one of said metal claddings.

16. The method of manufacturing a flexible printed circuit board with embedded optical waveguide structure of claim 14 , wherein said first flexible cover layer is flexible metal clad laminate, said first metal bump, said second metal bump and said optical waveguide structure are provided on said first flexible metal clad laminate, and both of said first metal bump and said second metal bump is pr

Assignees

• Cyntec Co Ltd

Inventors

• Hsu Chia-Fu
• Chen Chun-Yen

Classifications

• H05K3/188

  by direct electroplating · CPC title

• H05K2201/09985

  Hollow waveguide combined with printed circuit · CPC title

• H05K2201/10121

  Optical component, e.g. opto-electronic component · CPC title

• H05K2201/0367

  Metallic bump or raised conductor not used as solder bump · CPC title

• H05K3/0094

  Filling or covering plated through-holes or blind plated vias, e.g. for masking or for mechanical reinforcement · CPC title