Ceramic sintering for uniform color for a housing of an electronic device

• US 10,264,690 B2
• Filed: 06/01/2017
• Issued: 04/16/2019
• Est. Priority Date: 09/01/2016
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Ely, Colin M., Memering, Dale N., Takagi, Kazuya, Matsuyuki, Naoto, Waniuk, Theodore A.
• Primary Examiner(s): Miggins, Michael C
• Application Number:
  US15/611,329
• Publication Number:
  US 20180063975A1
• Time in Patent Office: 684 Days
• CPC Class Codes: C04B 2235/3244 Zirconium oxides, zirconates, hafnium oxides, hafnates, or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3262 Manganese oxides, manganates, rhenium oxides or oxide-forming salts thereof, e.g. MnO
• CPC Class Codes: C04B 2235/3275 Cobalt oxides, cobaltates or cobaltites or oxide forming salts thereof, e.g. bismuth cobaltate, zinc cobaltite
• CPC Class Codes: C04B 2235/6567 Treatment time
• CPC Class Codes: C04B 2235/661 Multi-step sintering
• CPC Class Codes: C04B 2235/9661 Colour
• CPC Class Codes: C04B 35/48 based on zirconium or hafnium oxides, zirconates, zircon or hafnates
• CPC Class Codes: C04B 35/486 Fine ceramics
• CPC Class Codes: C04B 35/64 Burning or sintering processes C04B33/32 takes precedence ; powder metallurgy B22F
• CPC Class Codes: C09C 1/0009 Pigments for ceramics C09C1/0015, C09C1/0078 take precedence
• CPC Class Codes: H05K 5/0217 Mechanical details of casings covers, lids, hoods or members for covering apertures H05K5/03

Abstract

A method of manufacturing a housing of an electronic device includes determining a sintering profile configured to produce a selected color at a selected depth within a wall of the housing, sintering a ceramic housing precursor in accordance with the determined sintering profile, thereby forming the housing, and removing material from the housing up to the selected depth.

Claims

1. A housing for an electronic device, comprising:

a wall defining an exterior surface of the housing and comprising;

a ceramic material;

a pigment incorporated with the ceramic material;

wherein

a color distance between a first portion of the ceramic material at or near the exterior surface and a second portion of the ceramic material about 0.5 mm below the exterior surface has a Delta E 76 value of less than or equal to about 2.0; and

a color of the first portion and a color of the second portion each has an L* value greater than about 87.

2. The housing of claim 1, wherein the Delta E 76 value is less than or equal to about 1.0.

3. The housing of claim 1, wherein the Delta E 76 value is less than or equal to about 0.5.

4. The housing of claim 1, wherein:

the first portion has a first b* value; and

the second portion has a second b* value that is less than about 0.5 units different from the first b* value.

5. The housing of claim 1, wherein:

the first portion has a first b* value; and

the second portion has a second b* value that is less than about 0.3 units different from the first b* value.

6. The housing of claim 1, wherein the ceramic material is zirconia.

7. The housing of claim 1, wherein:

a color of the first portion has an a* value between about −

15 and about 5.0, and a b* value between about −

10 and about 10; and

a color of the second portion has an a* value between about −

15 and about 5.0, and a b* value between about −

10 and about 10.

8. The housing of claim 1, wherein the color of the first portion has an L* value between about 88 and about 93 and the color of the second portion has an L* value between about 88 and about 93.

9. A method of manufacturing a housing of an electronic device, comprising:

heating, at a first temperature for a first duration, a ceramic housing precursor comprising a ceramic material and a pigment, thereby sintering the ceramic material and forming the housing;

heating the housing at a second temperature for a second duration, the second temperature being lower than the first temperature, lower than a sintering threshold of the ceramic material, and higher than a pigment stabilization threshold;

cooling the housing; and

removing material from the housing up to a selected depth.

10. The method of claim 9, wherein:

the ceramic material comprises zirconia; and

the pigment comprises one or both of manganese oxide and cobalt oxide.

11. The method of claim 9, wherein the second duration is longer than the first duration.

12. The method of claim 9, wherein the operation of heating the housing at the second temperature does not coarsen a microstructure of the housing.

13. The method of claim 9, wherein the pigment stabilization threshold is about 700°

C.

14. The method of claim 9, wherein:

the first duration is between about 1.5 hours and about 2.5 hours; and

the second duration is between about 1.5 hours and about 5.5 hours.

15. A housing for an electronic device, comprising:

a pigmented ceramic wall defining a machined exterior surface of the housing and having;

a color, of the machined exterior surface of the housing, having an L* value greater than about 87, an a* value between about −

5.0 and about 5.0, and a b* value between about −

5.0 and about 5.0; and

a color distance between the machined exterior surface of the housing and a portion of the ceramic material about 0.25 mm below the machined exterior surface has a Delta E 76 value of less than or equal to about 1.0.

16. The housing of claim 15, wherein the color of the machined exterior surface of the housing has an L* value between about 88 and about 93, an a* value between about −

2.0 and about 3.0, and a b* value between about −

1.5 and about 3.5.

17. The housing of claim 15, wherein the color distance between the machined exterior surface of the housing and the portion of the ceramic material about 0.25 mm below the machined exterior surface has a Delta E 76 value of less than or equal to about 0.5.

18. The housing of claim 15, wherein the pigmented ceramic wall comprises zirconia.

19. The housing of claim 15, wherein the pigmented ceramic wall has been machined to remove at least about 0.25 mm of material.