Targeted chemical strengthening of glass articles
Components of an electronic device, such as glass articles, are susceptible to breakage, especially in regions where machining a glass article has created flaws. Chemical strengthening can be performed to create deeper compression layers at regions of a glass article that have been machined, include and/or are adjacent to an edge feature, have greater surface roughness, and/or have more or deeper cracks.
1. A glass article for an electronic device, the glass article comprising:
a first region having a first surface roughness, wherein the first region defines a first compression layer having a first depth, wherein the first surface roughness has a corresponding surface roughness parameter R a that is greater than 10 μm; and
a second region having a second surface roughness less than the first surface roughness, wherein the second region defines a second compression layer having a second depth less than the first depth.
2. The glass article of claim 1 , wherein the first region includes an edge comprising a chamfer, curve, spline curve, s-curve, bevel, fillet, radius, or taper.
3. The glass article of claim 1 , wherein the first region includes an edge at a periphery of an opening that extends through the glass article.
4. The glass article of claim 1 , wherein the glass article comprises: a front surface; and
a back surface, wherein the first region includes an edge at a transition between the front surface to the back surface.
5. The glass article of claim 1 , wherein a thickness of the glass article is uniform across at least a portion of the first region and at least a portion of the second region.
6. The glass article of claim 1 , wherein the first and second compression layers each have a greater density of alkali metal ions than other portions of the glass article.
7. The glass article of claim 1 , wherein the first depth is greater than a depth of a crack extending from a surface of the first region.
8. The glass article of claim 1 , wherein the first depth is greater 50 μm and the second depth is less than 50 μm.
9. A method of strengthening a glass article for an electronic device, the method comprising:
applying a mask to a glass article having a first region and a second region, the first region having a first surface roughness and the second region having a second surface roughness less than the first surface roughness, wherein the first region includes an edge and the mask covers the second region, wherein the first surface roughness has a corresponding surface roughness parameter R a that is greater than 10 μm;
forming a first compression layer in the first region by chemically strengthening the first region;
removing the mask; and
forming a second compression layer in the second region by chemically strengthening the second region, wherein the first compression layer has a first depth and the second compression layer has a second depth less than the first depth.
10. The method of claim 7 , further comprising, prior to applying the mask, machining the first region of the glass article to form the edge.
11. The method of claim 7 , further comprising:
prior to applying the mask, heating the glass article having opposing first and second surfaces and a third surface connecting the first and second surfaces;
applying a press mold to the glass article to form the edge at the first surface or the second surface and to form an elongated portion at the third surface; and
removing the elongated portion from the third surface such that the third surface is substantially flat.
12. The method of claim 7 , further comprising:
prior to applying the mask, heating the glass article; and
applying a press mold to the glass article to form curved surfaces on the glass article.
13. The method of claim 12 , wherein the curved surfaces comprise a concave portion on a first side of the glass article and a convex portion on a second side of the glass article, the second side being opposite the first side.
14. The method of claim 7 , wherein the first and second compression layers each have a greater density of alkali metal ions than other portions of the glass article.
15. The method of claim 7 , further comprising, while forming the second compression layer in the second region, enlarging the first compression layer in the first region.
16. A glass article for an electronic device, the glass article comprising:
a first region, wherein the first region defines a first compression layer having a first depth and a first surface roughness having a corresponding surface roughness parameter R a that is greater than 10 μm; and
a second region, wherein the second region defines a second compression layer having a second depth less than the first depth and having a second surface roughness less than the first surface roughness,
wherein the glass article has a uniform thickness across the first region and the second region.
17. The glass article of claim 16 , further comprising an edge adjacent to a portion of the first region that has the uniform thickness.
18. The glass article of claim 17 , wherein the edge is disposed at a periphery of an opening that extends through the glass article.
19. The glass article of claim 16 , wherein the first and second compression layers each have a greater density of alkali metal ions than other portions of the glass article.