Method for assembling a tiled, flat-panel microdisplay array having reflective microdisplay tiles and attaching thermally-conductive substrate

• US 6,556,261 B1
• Filed: 06/21/2000
• Issued: 04/29/2003
• Est. Priority Date: 02/15/1999
• Status: Expired due to Term

• Current Assignee: Hanger Solutions, LLC (IP Investments Group LLC)
• Original Assignee: Rainbow Displays, Inc.
• Inventors: Seraphim, Donald P., Krusius, J. Peter
• Primary Examiner(s): Kim, Robert H.
• Assistant Examiner(s): QI, ZHI QIANG
• Application Number:
  US09/597,662
• Time in Patent Office: 1,042 Days
• Field of Search: 349/73, 349/74, 349/20, 349/21, 349/122, 349/45, 349/153, 349/155, 349/158, 349/190, 345/103
• US Class Current: 349/73
• CPC Class Codes: G02F 1/13336 Combining plural substrates to produce large-area displays, e.g. tiled displays
• CPC Class Codes: G02F 1/136277 formed on a semiconductor substrate, e.g. of silicon

Abstract

This invention describes fabrication techniques for producing microdisplays suitable for combining into tiled, flat-panel displays having visually imperceptible seams. Assembly techniques to overcome flatness requirements imposed by tiled, flat-panel display assemblies are also described. Edge treatment techniques for individual microdisplays while still part of the silicon die or wafer are also described. The use of these inventive techniques allows the assembly microdisplays into tiled, flat-panel that are appear visually seamless and optically uniform.

Claims

1. A method for assembling a plurality of microdisplay tiles into a tiled, microdisplay, the projected image of said microdisplay having visually imperceptible seams in reflection, the steps comprising:

a) providing a plurality of monolithic, reflective microdisplay tiles, each microdisplay having a front, active face and a rear, mounting face, at least one inner, precision finished edge, each of said microdisplay tiles comprising an array of pixels having a predetermined pixel pitch and each tile having an integrated circuit silicon backplane embedded therein and a predetermined thermal coefficient of expansion (TCE);

b) three-dimensionally arranging said plurality of microdisplay tiles with respect to one another with said at least one inner, precision finished edge of a first one, of said plurality of microdisplay tiles adjacent to said at least one precision finished edge of a second one of said plurality of microdisplay tiles;

c) releasably attaching said plurality of microdisplay tiles to an optically flat carrier;

d) after said arranging step (b) and said attaching step (c), applying a filling material to said rear faces of said plurality of microdisplay tiles, if required, to fill any gaps between said inner, precision finished edges of said microdisplay tiles;

e) after completing said arranging step (d), attaching a thermally-conductive, common silicon substrate having a TCE substantially equal to said predetermined TCE of said microdisplay tiles to said rear faces of said plurality of microdisplay tiles;

f) after said attaching step (e), removing said plurality of microdisplay tiles from said optically flat carrier and polishing said front active faces of each of said plurality of microdisplay tiles to an optical local flatness of less than approximately 100 nm;

g) attaching a common transparent cover plate proximate said front faces of said plurality of microdisplay tiles; and

h) placing liquid crystal material between said front faces of said plurality of microdisplay tiles and said common cover plate to complete a liquid crystal cell.

2. The method for assembling a plurality of microdisplay tiles into a tiled, microdisplay as recited in claim 1, wherein said attaching step (e) comprises the sub-step:

i) applying a thermally-conductive adhesive to at least one of said rear faces of said plurality of tiles and said substrate.

3. The method for assembling a plurality of microdisplay tiles into a tiled, microdisplay as recited in claim 2, wherein said thermally-conductive adhesive comprises an adhesive material having thermally-conductive particles dispersed therein.

4. The method for assembling a plurality of microdisplay tiles into a tiled, microdisplay as recited in claim 3, wherein said thermally-conductive particles comprise particles of at least one from the group of diamond, boron nitride, silicon carbide, aluminum nitride, other thermally-conductive ceramics, silver, copper, gold, tin, and solder.

5. The method for assembling a plurality of microdisplay tiles into a tiled, microdisplay as recited in claim 4, wherein said thermally-conductive particles are spherically shaped.

6. The method for assembling a plurality of microdisplay tiles into a tiled, microdisplay as recited in claim 2, wherein said thermally-conductive, common substrate comprises a cooling structure.

7. The method for assembling a plurality of microdisplay tiles into a tiled, microdisplay as recited in claim 6, wherein said cooling structure comprises a heat sink.

8. The method for assembling a plurality of microdisplay tiles into a tiled, microdisplay as recited in claim 7, wherein said heat sink comprises fins.

9. The method for assembling a plurality of microdisplay tiles into a tiled, microdisplay as recited in claim 6, wherein said cooling structure comprises channels for circulating a cooling fluid within said substrate.

10. The method for assembling a plurality of microdisplay tiles into a tiled, microdisplay as recited in claim 6, wherein said cooling structure comprises thermoelectric cooling means.

11. The method for assembling a plurality of microdisplay tiles into a tiled, microdisplay as recited in claim 6, wherein said cooling structure comprises a heat pipe.

12. The method for assembling a plurality of microdisplay tiles into a tiled, microdisplay as recited in claim 1, wherein said attaching step (e) further comprises the sub-step:

i) applying a thermally conductive, metallic coating to substantially the entire area of at least one of said rear faces of said plurality of tiles and said substrate to enhance thermal conductivity therebetween.

13. The method for assembling a plurality of microdisplay tiles into a tiled, microdisplay as recited in claim 12, wherein said conductive, metallic coating comprises a thin coating of a least one metal from the group of silver, copper, indium, tin and solder.

14. The method for assembling a plurality of microdisplay tiles into a tiled, microdisplay as recited in claim 13, wherein said applying sub-step (ii) comprises plating.

15. The method for assembling a plurality of microdisplay tiles into a tiled, microdisplay as recited in claim 13, wherein said applying sub-step (ii) comprises sputtering.

16. The method for assembling a plurality of microdisplay tiles into a tiled, microdisplay as recited in claim 13, wherein said applying sub-step (ii) comprises evaporation.

17. The method for assembling a plurality of reflective microdisplay tiles as recited in claim 1, wherein said attaching step (d) comprises arranging said plurality of microdisplay tiles with respect to a direction substantially perpendicular to the plane of said front faces of said microdisplay tiles.

18. The method for assembling a plurality of reflective microdisplay tiles as recited in claim 17, wherein arranging said plurality of microdisplay tiles with respect to a direction perpendicular to said faces results in tile-to-tile differences less than approximately 100 nm.

19. The method for assembling a plurality of reflective microdisplay tiles as recited in claim 18, wherein tile-to-tile differences in said perpendicular direction of said tiles in said arrangement is less than one half the distance between said faces thereof.

20. The method for assembling a plurality of reflective microdisplay tiles as recited in claim 18, wherein tile-to-tile differences in said perpendicular direction of said tiles in said arrangement is less than one quarter the distance between said faces thereof.

21. The method for assembling a plurality of reflective microdisplay tiles as recited in claim 18, wherein tile-to-tile differences in said perpendicular direction of said tiles in said arrangement is less than one tenth the distance between said faces thereof.

22. The method for assembling a plurality of reflective microdisplay tiles as recited in claim 17, wherein said optically flat carrier is removable.

23. The method for assembling a plurality of reflective microdisplay tiles as recited in claim 1, wherein said laterally arranging step (b) comprises arranging said plurality of microdisplay tiles with respect to at least one of two orthogonal, lateral directions parallel to said faces of said microdisplay tiles.

24. The method for assembling a plurality of microdisplay tiles into a tiled, microdisplay as recited in claim 1, the steps further comprising:

j) after completing said releasably attaching step (c), polishing said rear, mounting face of each of said plurality of microdisplay, if required.