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A study of 3D cover glass design that improves handheld device drop reliability
Author(s) -
Zhang Bin,
Gorelchenko Petr,
Hu Guangli
Publication year - 2016
Publication title -
journal of the society for information display
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.578
H-Index - 52
eISSN - 1938-3657
pISSN - 1071-0922
DOI - 10.1002/jsid.504
Subject(s) - materials science , mobile device , drop (telecommunication) , enhanced data rates for gsm evolution , toughened glass , drop test , finite element method , reliability (semiconductor) , radius , range (aeronautics) , computer science , composite material , optics , mechanical engineering , structural engineering , engineering , telecommunications , power (physics) , physics , computer security , quantum mechanics , operating system
Cover glass in commercial handheld devices is now evolving from flat (2D) to curved (3D) shapes. For example, some commercial devices have utilized sled‐shape cover glass,[1][, 2016] which partially covers long edges of the device. According to the patents published by key handheld manufacturers,[2][, 2013], [3][, 2013] we can expect more variety of 3D shaped cover glass for handheld devices in the market. In this study, we have focused on the reliability of 3D cover glass when it is dropped to a rigid surface. The key parameters under study are the corner/edge bend radius and angle of the cover glass, which determines the 3D shape of the cover glass. To achieve this goal, we developed a finite element model to simulate the drop[4][, 1989], [5][, 2004], [6][, 2004], [7][, 2004], [8][, 2009], [9][, 2015], [10][, 1998], [11][, 2007], [12][, 2005], [13][, 2002] of a handheld device with 3D‐shaped glass. The model uses explicit algorithm to simulate the high speed impact on the device during the drop test. The glass performance was evaluated based on contact force between the glass and the ground and maximum principal stress in the glass. We showed that to avoid severe damage because of first impact between the glass and the ground, the bend angle of 3D glass has to be in the range between 0 and 45°. For drop angles of 45° and higher, with the proposed glass bend angle, the impact can be taken over by the edge of the back cover of the device. In addition, we showed that optimum glass bend radius is in the range of 3.8 mm and larger. This is required to reduce stress in glass because of impact. The approach and conclusions from the current study can serve as a general guideline to improve the 3D cover glass reliability of a handheld device.