What you need to pay attention about cover glass tolerances
Jun 17, 2026
Each cover glass spec sheet has tolerance, below are more information:
Thickness tolerance
Per GB/T 36259-2018 ±0.02mm is the industry baseline, it's the standard for touchscreen cover glass in China. Tigther means pay more, but looser may have lamination issues.
Warpage(flatness)
It kills yield. Chemical strengthened glass keeps warpage under 0.2mm for 3mm thickness. Thermal tempered glass is 0.5mm, which is a big gap.
For display bonding, shops spec warpage<0.2%. For a 100mm product that's 0.2mm max. Anything over and you get bonding voids or touch sensor misalignment.
After chemical strengthening, typical warpage for a 0.7mm sheet is around 130μm if you don't control it.
Actually, it's inversely proportional to thickness squared-so going from 0.7mm to 2.0mm drops warpage from 130μm to about 16μm. That's why thicker parts are easier to keep flat.
Edge profiling and cutouts
2.5D and 3D edges run at ±0.5mm tolerance typically.
Camera holes down to 1mm diameter need careful drilling. Hole wall light leakage is a spec item too-if the edge ink doesn't block light completely, you see it on the display.
The warpage gotcha
Float glass warps toward the tin side after strengthening.
Top surface vs bottom surface have different Na₂O content-that's what drives the bend. The fix?
Dealkalization treatment on one side to balance ion exchange rates. When the Na₂O difference hits 0.38–1.2% by mass, warpage drops. 0.4–0.7% is the sweet spot.
