Strengthened covers for electronic devices
Methods for chemically strengthening a cover for an electronic are disclosed. The methods include removing material from a mounting surface of the cover to counteract warping of the mounting surface due to ion exchange. The chemically strengthened covers have a high bend strength and allow a strong seal to be formed between the cover and an enclosure component.
1. An electronic device comprising:
an enclosure component defining a first mounting surface;
an electronic device component positioned at least partially within the enclosure component; and
a cover formed from a glass ceramic material, the cover positioned over the electronic device component and defining:
a central portion;
a second mounting surface at a rear of the cover, at least partially surrounding the central portion, and coupled to the first mounting surface; and
a compressive stress layer having:
a first depth along a first region of the second mounting surface;
a second depth, greater than the first depth, along a second region of the second mounting surface; and
a third depth, greater than the first depth, along a rear surface of the central portion.
2. The electronic device of claim 1 , wherein:
the cover further comprises a peripheral portion at least partially surrounding the central portion; and
the second mounting surface is defined along the peripheral portion.
3. The electronic device of claim 2 , wherein a bend region is defined along the peripheral portion of the cover and extends from the central portion to the second mounting surface.
4. The electronic device of claim 2 , wherein:
the peripheral portion defines a flange extending at an angle from the central portion wherein:
the flange defines:
the first region and the second region of the second mounting surface;
a first height at the first region of the second mounting surface; and
a second height, greater than the first height, at the second region of the second mounting surface;
the first region of the second mounting surface extends along aside of the central portion; and
the second region extends around a corner of the central portion.
5. The electronic device of claim 2 , wherein a surface compressive stress of the second region of the second mounting surface is greater than a surface compressive stress of the first region.
6. The electronic device of claim 2 , wherein:
the electronic device component is a display and the cover is transparent; and
the first and the second regions of the second mounting surface are coplanar to within 25 microns.
7. The electronic device of claim 6 , wherein the first mounting surface is coupled to the second mounting surface through an intermediate component.
8. An electronic device, comprising:
an enclosure component defining a first mounting surface;
a display; and
a glass ceramic cover defining a transparent window over the display and comprising:
a central portion;
a flange at least partially surrounding the central portion, and defining:
a second mounting surface at a rear of the flange;
a first segment extending along a first side of the central portion and defining a first region of the second mounting surface;
a second segment defining a corner of the flange and a second region of the second mounting surface and extending from the first segment to athird segment of the flange; and
the third segment extending along a second side of the central portion and defining a third region of the second mounting surface, each of the first region, the second region, and the third region of the second mounting surface coupled to the first mounting surface; and
a compressive stress layer having:
a first depth at the first region;
a second depth, greater than the first depth, at the second region; and
a third depth, greater than the first depth, along a rear surface of the central portion.
9. The electronic device of claim 8 , wherein a height of the first segment is less than a height of the second segment.
10. The electronic device of claim 8 , wherein the compressive stress layer has a fourth depth, greater than the first depth, at the third region.
11. The electronic device of claim 10 , wherein a length of the third segment is less than a length of the first segment.
12. The electronic device of claim 8 , wherein the compressive stress layer comprises:
a surface zone extending from the first, the second, and the third regions of the second mounting surface;
an internal zone extending from the surface zone; and
a potassium concentration of the surface zone differs from a potassium concentration of the internal zone.
13. The electronic device of claim 12 , wherein the surface zone has a depth from 10 microns to 50 microns.
14. The electronic device of claim 8 , wherein:
the central portion of the glass ceramic cover defines a front surface opposite the rear surface;
the compressive stress layer defines, along the first region of the second mounting surface:
a first surface zone; and
a first internal zone having a first thickness;
the compressive stress layer defines, along the second region of the second mounting surface:
a second surface zone; and
a second internal zone having a second thickness greater than the first thickness; and
the compressive stress layer defines, along the front surface of the central portion:
a third surface zone; and
a third internal zone having a third thickness greater than the first thickness.
15. An electronic device comprising:
an enclosure component defining a first mounting surface;
a display;
a transparent cover positioned over the display and comprising a glass ceramic material, the transparent cover defining:
a central portion;
a peripheral portion at least partially surrounding the central portion and defining a second mounting surface at a rear of the peripheral portion and coupled to the first mounting surface; and
a compressive stress layer having:
a first depth along a first region of the second mounting surface;
a second depth, greater than the first depth, along a second region of the second mounting surface; and
a third depth, greater than the first depth, along a rear surface of the central portion.
16. The electronic device of claim 15 , wherein a surface compressive stress of the second region of the second mounting surface is greater than a surface compressive stress of the first region of the second mounting surface.
17. The electronic device of claim 15 , wherein the glass ceramic material is an alkali aluminosilicate glass ceramic material.
18. The electronic device of claim 17 , wherein the compressive stress layer comprises:
a surface zone extending from the first region of the second mounting surface and having a first potassium concentration; and
an internal zone extending from the surface zone and having a second potassium concentration less than the first potassium concentration.
19. The electronic device of claim 15 , wherein:
the central portion of the transparent cover comprises a front surface and the rear surface is opposite the front surface;
the compressive stress layer defines, along the first region of the second mounting surface:
a first surface zone; and
a first internal zone having a first thickness;
the compressive stress layer defines, along the second region of the second mounting surface:
a second surface zone; and
a second internal zone having a second thickness greater than the first thickness; and
the compressive stress layer defines, along the front surface of the central portion:
a third surface zone; and
a third internal zone having a third thickness greater than the first thickness.
20. The electronic device of claim 15 , wherein the glass ceramic material defines a glass ceramic portion of the transparent cover and the transparent cover further defines a glass portion.