Flexible printed circuit board for light emitting diode backlight unit and method of fabricating the same

• US 8,067,697 B2
• Filed: 10/16/2009
• Issued: 11/29/2011
• Est. Priority Date: 12/29/2008
• Status: Active Grant

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Display Co., Ltd.
• Inventors: Lee, Koo-hwa, Lee, Rok-hee, Lee, Geun-woo
• Primary Examiner(s): Chen; Xiaoliang
• Application Number:
  US12/580,598
• Publication Number:
  US 20100165657A1
• Time in Patent Office: 774 Days
• Field of Search: 174/254, 174/253, 174/262, 361/517, 257/99, 257/698, 257/737, 349/39, 349/48, 298/48, 298/52, 438/106, 438/149
• US Class Current: 174/254
• CPC Class Codes: H05K 1/028 Bending or folding regions of flexible printed circuits H05K1/0283 takes precedence
• CPC Class Codes: H05K 1/147 at least one of the printed circuits being bent or folded, e.g. by using a flexible printed circuit H05K1/148 takes precedence
• CPC Class Codes: H05K 2201/093 Layout of power planes, ground planes or power supply conductors, e.g. having special clearance holes therein
• CPC Class Codes: H05K 2201/09663 Divided layout, i.e. conductors divided in two or more parts
• CPC Class Codes: H05K 2201/09781 Dummy conductors, i.e. not used for normal transport of current; Dummy electrodes of components
• CPC Class Codes: H05K 2201/10106 Light emitting diode [LED]
• CPC Class Codes: H05K 3/244 Finish plating of conductors, especially of copper conductors, e.g. for pads or lands selective plating methods H05K3/243; finish plating of conductors made by printing techniques H05K3/246; solder as finish H05K3/3457, e.g. by plating H05K3/3473
• CPC Class Codes: Y10T 29/49156 with selective destruction of conductive paths
• CPC Class Codes: Y10T 29/49158 with molding of insulated base
• CPC Class Codes: Y10T 29/49165 by forming conductive walled aperture in base

Abstract

A flexible printed circuit board (PCB) for a light emitting diode backlight unit includes a flexible base film; a plurality of metal lines on a first surface of the flexible base film; a cover layer on the metal lines and covering a center portion of the first surface of the flexible base film; a first gold-plating pattern on the metal lines and at both ends of the first surface of the flexible base film; a metal pattern on a second surface of the flexible base film and including a first sub-pattern at one end of the second surface, a second sub-pattern at the other end of the second surface and a plurality of third-sub patterns between the first and second sub-patterns of the metal pattern; and a second gold-plating pattern on the metal pattern and including a fourth sub-pattern on the first sub-pattern, a fifth sub-pattern on the second sub-pattern, and a plurality of sixth-sub patterns each on the third sub-patterns, wherein a first groove between a first double-layered pattern of the first sub-pattern and the fourth sub-pattern and a second double-layered pattern of the third sub-pattern and the sixth sub-pattern, a second groove between a third double-layered pattern of the second sub-pattern and the fifth sub-pattern and a second double-layered pattern of the third sub-pattern and the sixth sub-pattern, and a third groove between adjacent second double-layered patterns respectively expose a portion of the second surface of the flexible base film.

Claims

1. A flexible printed circuit board (PCB) for a light emitting diode backlight unit, comprising:

a flexible base film;

a plurality of metal lines on a first surface of the flexible base film;

a cover layer on the metal lines and covering a center portion of the first surface of the flexible base film;

a first gold-plating pattern on the metal lines and at both ends of the first surface of the flexible base film;

a metal pattern on a second surface of the flexible base film and including a first sub-pattern at one end of the second surface, a second sub-pattern at the other end of the second surface and a plurality of third-sub patterns between the first and second sub-patterns of the metal pattern; and

a second gold-plating pattern on the metal pattern and including a fourth sub-pattern on the first sub-pattern, a fifth sub-pattern on the second sub-pattern, and a plurality of sixth-sub patterns each on the third sub-patterns,

wherein a first groove between a first double-layered pattern of the first sub-pattern and the fourth sub-pattern and a second double-layered pattern of the third sub-pattern and the sixth sub-pattern, a second groove between a third double-layered pattern of the second sub-pattern and the fifth sub-pattern and a second double-layered pattern of the third sub-pattern and the sixth sub-pattern, and a third groove between adjacent second double-layered patterns respectively expose a portion of the second surface of the flexible base film.

2. The flexible PCB according to claim 1, wherein each of the metal lines and the metal pattern is formed of copper.

3. The flexible PCB according to claim 1, wherein the flexible PCB is bent at each of the grooves.

4. The flexible PCB according to claim 1, wherein the first groove is larger than each of the second and third grooves.

5. The flexible PCB according to claim 4, wherein the first distance has a range within about 1 centimeter to about 3 centimeter, and the second distance has a range within about 0.5 millimeter to about 2 millimeter.

6. The flexible PCB according to claim 1, wherein the first, second and third sub-patterns have the same shape as the fourth, fifth and sixth sub-patterns, respectively.

7. The flexible PCB according to claim 1, further comprising a kapton tape on the fifth sub-pattern and having an adhesive layer on a portion of the kapton tape.

8. A method of fabricating a flexible PCB for a light emitting diode backlight unit, comprising:

etching a first metal layer on a first surface of a flexible base film to form a plurality of metal lines and a second metal layer on a second surface of the flexible base film to form a metal pattern including a first sub-pattern at one end of the second surface, a second sub-pattern at the other end of the second surface and a plurality of third-sub patterns between the first and second sub-patterns of the metal pattern;

forming a cover layer by forming and pattering a cover material layer on the metal lines, the cover layer covering a center of the first surface of the flexible base film;

forming a first gold-plating pattern on the metal lines and at both ends of the first surface of the flexible base film; and

forming a second gold-plating pattern including a fourth sub-pattern on the first sub-pattern, a fifth sub-pattern on the second sub-pattern, and a plurality of sixth-sub patterns each on the third sub-patterns,

wherein a first groove between a first double-layered pattern of the first sub-pattern and the fourth sub-pattern and a second double-layered pattern of the third sub-pattern and the sixth sub-pattern, a second groove between a third double-layered pattern of the second sub-pattern and the fifth sub-pattern and a second double-layered pattern of the third sub-pattern and the sixth sub-pattern, and a third groove between adjacent second double-layered patterns respectively expose a portion of the second surface of the flexible base film.

9. The method according to claim 8, wherein the step of etching the first metal layer and the second metal layer includes:

forming a first photoresist pattern on the first metal layer and corresponding to the metal lines;

etching the first metal layer using the first photoresist pattern as an etching mask;

forming a second photoresist pattern on the second metal layer and corresponding to the metal pattern; and

etching the second metal layer using the second photoresist pattern as an etching mask; and

stripping the first and second photoresist patterns.

10. The method according to claim 8, further comprising forming a kapton tape on the fifth sub-pattern and having an adhesive layer on a portion of the kapton tape.

11. The method according to claim 8, wherein the step of forming the first gold-plating pattern and the step of forming the second gold-plating pattern includes dipping the base film into an aqueous solution including gold-potassium cyanide.

12. The method according to claim 8, wherein each of the metal lines and the metal pattern is formed of copper.

13. The method according to claim 8, wherein the first groove is larger than each of the second and third grooves.

14. The method according to claim 13, wherein the first distance has a range within about 1 centimeter to about 3 centimeter, and the second distance has a range within about 0.5 millimeter to about 2 millimeter.

15. A backlight unit for a liquid crystal display module, comprising:

a reflective sheet;

a light guide plate on the reflective sheet;

at least one light emitting diode at a side of the light guide plate and on a printed circuit board;

a flexible printed circuit board including;

a flexible base film;

a plurality of metal lines on a first surface of the flexible base film;

a cover layer on the metal lines and covering a center portion of the first surface of the flexible base film;

a first gold-plating pattern on the metal lines and at both ends of the first surface of the flexible base film;

a metal pattern on a second surface of the flexible base film and including a first sub-pattern at one end of the second surface, a second sub-pattern at the other end of the second surface and a plurality of third-sub patterns between the first and second sub-patterns of the metal pattern; and

a second gold-plating pattern on the metal pattern and including a fourth sub-pattern on the first sub-pattern, a fifth sub-pattern on the second sub-pattern, and a plurality of sixth-sub patterns each on the third sub-patterns; and

a plurality of optical sheets over the light guide plate,

wherein a first groove between a first double-layered pattern of the first sub-pattern and the fourth sub-pattern and a second double-layered pattern of the third sub-pattern and the sixth sub-pattern, a second groove between a third double-layered pattern of the second sub-pattern and the fifth sub-pattern and a second double-layered pattern of the third sub-pattern and the sixth sub-pattern, and a third groove between adjacent second double-layered patterns respectively expose a portion of the second surface of the flexible base film, and wherein an end of the flexible printed circuit board connected to the printed circuit board.