Electronic Device Display with a Backlight

• US 20200133046A1
• Filed: 06/12/2019
• Published: 04/30/2020
• Est. Priority Date: 10/26/2018
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Goyal, Supriya, Zhao, Yuxi, Chu, Xinsheng, Park, Chan Hyuk, Tao, Min, Zhu, Wenyong
• Granted Patent: US 11,221,513 B2
• Time in Patent Office: Days
• CPC Class Codes: G02B 6/0028 Light guide, e.g. taper
• CPC Class Codes: G02B 6/0038 Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide
• CPC Class Codes: G02B 6/005 provided by one optical element, or plurality thereof, placed on the light output side of the light guide
• CPC Class Codes: G02B 6/0051 Diffusing sheet or layer
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02B 6/0061 to provide homogeneous light output intensity
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources
• CPC Class Codes: G02B 6/0073 Light emitting diode [LED]
• CPC Class Codes: G02B 6/0083 Details of electrical connections of light sources to drivers, circuit boards, or the like
• CPC Class Codes: G02B 6/0088 of the light guide or other optical sheets in the package
• CPC Class Codes: G02B 6/009 of the light source in the package G02B6/0021 takes precedence
• CPC Class Codes: G02F 1/13306 Circuit arrangements or driving methods for the control of single liquid crystal cells G02F1/132, G02F1/133382 take precedence
• CPC Class Codes: G02F 1/133603 with LEDs
• CPC Class Codes: G02F 1/13452 Conductors connecting driver circuitry and terminals of panels
• CPC Class Codes: G02F 1/1368 in which the switching element is a three-electrode device G02F1/136277 takes precedence
• CPC Class Codes: G09G 3/006 Electronic inspection or testing of displays and display drivers, e.g. of LED or LCD displays testing individual LED's G01R31/2635; testing lamps G01R31/44; testing of optical features of LCD displays G02F1/1309
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: H01R 12/62 connecting to rigid printed circuits or like structures
• CPC Class Codes: H01R 4/04 using electrically conductive adhesives
• CPC Class Codes: H05K 1/0281 Reinforcement details thereof
• CPC Class Codes: H05K 1/118 : specially for flexible printed circuits, e.g. using folded portions
• 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 1/189 : characterised by the use of a flexible or folded printed circuit H05K3/326 takes precedence
• CPC Class Codes: H05K 2201/094 : Array of pads or lands differing from one another, e.g. in size, pitch, thickness; Using different connections on the pads using different types of conductors H05K2201/0391
• CPC Class Codes: H05K 2201/10106 : Light emitting diode [LED]
• CPC Class Codes: H05K 2201/10136 : Liquid Crystal display [LCD]
• CPC Class Codes: H05K 2201/10674 : Flip chip
• CPC Class Codes: H05K 3/361 : Assembling flexible printed circuits with other printed circuits

Abstract

An electronic device may include display layers such as liquid crystal display layers and a backlight unit that provides illumination for the display layers. The backlight unit may include light-emitting diodes that emit light into the edge of a light guide film. To minimize the inactive area of the display, the light-emitting diodes may be tightly spaced to approximate a line light source instead of point light sources. Color and/or luminance compensation layers may be incorporated at various locations within the backlight structures to ensure that the backlight provided to the display layers is homogenous. A thin-film transistor layer of the display may be coupled to a printed circuit board by a flexible printed circuit. The flexible printed circuit may have additional solder mask layers to improve robustness, may include encapsulation, and may have traces with a varying pitch.

Claims

1. An electronic device comprising:

display layers that include a thin-film transistor layer;

a printed circuit board;

a flexible printed circuit coupled between the thin-film transistor layer and the printed circuit board, wherein the flexible printed circuit has traces that are electrically connected to the thin-film transistor layer and wherein the traces have a varying pitch across the flexible printed circuit; and

a display driver integrated circuit mounted on the flexible printed circuit.

2. The electronic device defined in claim 1, wherein the pitch of the traces is at a minimum at a center of the flexible printed circuit and wherein the pitch of the traces is at a maximum at an edge of the flexible printed circuit.

3. The electronic device defined in claim 1, wherein the pitch of the traces follows a profile that increases with a distance from a center of the flexible printed circuit.

4. The electronic device defined in claim 3, wherein the profile increases according to a step function.

5. The electronic device defined in claim 1, further comprising:

a stainless steel stiffener attached to the flexible printed circuit.

6. The electronic device defined in claim 5, wherein the flexible printed circuit has first and second opposing surfaces, wherein the display driver integrated circuit is mounted to the first surface of the flexible printed circuit and wherein the stainless steel stiffener is attached to the second surface of the flexible printed circuit below the display driver integrated circuit.

7. The electronic device defined in claim 1, wherein the flexible printed circuit includes a solder resist layer that overlaps an edge of the thin-film transistor layer.

8. The electronic device defined in claim 1, wherein the flexible printed circuit includes a copper trace and a tin trace formed over the copper trace and wherein the flexible printed circuit has a bent region in which the tin trace is omitted.

9. The electronic device defined in claim 8, wherein a solder resist layer is in direct contact with the copper trace in the bent region and wherein the solder resist layer is in direct contact with the tin trace outside of the bent region.

10. An electronic device comprising:

display layers that include a thin-film transistor layer;

a printed circuit board that includes a first contact;

a flexible printed circuit coupled between the thin-film transistor layer and the printed circuit board, wherein the flexible printed circuit has a second contact that is coupled to the first contact on the printed circuit board;

a display driver integrated circuit mounted on the flexible printed circuit; and

a gap-filling layer on the printed circuit board that is interposed between an edge of the printed circuit board and the first contact, wherein the second contact overlaps the gap-filling layer.

11. The electronic device defined in claim 10, wherein the gap-filling layer is formed form a solder mask layer.

12. The electronic device defined in claim 10, further comprising:

an anisotropic conductive film that attaches the first contact to the second contact.

13. The electronic device defined in claim 10, further comprising:

an encapsulant layer that is attached to a lower surface of the flexible printed circuit and the edge of the printed circuit board.

14. The electronic device defined in claim 10, further comprising:

an encapsulant layer that conforms to an edge of the flexible printed circuit and an upper surface of the printed circuit board.

15. The electronic device defined in claim 10, wherein the gap-filling layer comprises a plurality of discrete gap-filling layers.

16. An electronic device comprising:

display layers that include a thin-film transistor layer;

a printed circuit board that includes a first contact;

a flexible printed circuit coupled between the thin-film transistor layer and the printed circuit board, wherein the flexible printed circuit has a second contact that is coupled to the first contact on the printed circuit board and wherein the first and second contacts have first and second opposing sides;

a display driver integrated circuit mounted on the flexible printed circuit;

a first encapsulant layer formed on the first side of the first and second contacts; and

a second encapsulant layer formed on the second side of the first and second contacts.

17. The electronic device defined in claim 16, wherein the first encapsulant layer is attached to a lower surface of the flexible printed circuit and an edge of the printed circuit board.

18. The electronic device defined in claim 16, wherein the second encapsulant layer conforms to an edge of the flexible printed circuit and an upper surface of the printed circuit board.

19. The electronic device defined in claim 18, wherein the second encapsulant layer conforms to the second side of the first and second contacts.

20. The electronic device defined in claim 18, wherein the second encapsulant layer directly contacts an upper surface of the flexible printed circuit, the edge of the flexible printed circuit, and the upper surface of the printed circuit board.