Fracture Analysis of the Glass Scoring Process0 pages

Fracture Analysis of the
Glass Scoring Process
Technical Information Paper

TIP 308
Issued: November 2004
Supercedes: xxxx
R.A. Allaire
Science and Technology Group, Corning Incorporated, Corning, NY 14831
T. Ono
Shizuoka Technical Center, Corning Japan K.K.

Abstract
The scoring process is widely used for sizing of glass sheets. In this process, the score wheel generates a
small crack on the glass surface, which is then propagated through the glass for complete separation., This
report will present a description of the scoring process and an interpretation of the marking found on the
glass edges. Interpreting these markings can provide process understanding and assistance in problem
resolution.
Introduction
The scoring process is often used as a reliable and inexpensive method for sizing of glass sheets. Glass
manufacturers use it for removing undesirable portions of their formed sheet and for glass sizing. This report
will focus the fracture signatures and an interpretation of their origins. Examples for this discussion are drawn
from the scoring of sheet glass for AMLCD substrates. In this application, 0.7mm thick glass dominates the
market. Score wheels for this application, are often 2.5mm in diameter.
Fundamentals of Scoring
In the scoring process, a score wheel is used to generate a median or vent crack in the glass surface. As the
wheel rolls on the glass, the median crack is pushed downward and ahead of the wheel. The wheel rides on top
of an open crack, forcing the crack open with a wedging action. The scoring wheel penetrates into the glass
surface to a depth of only 2-5pm, yet the median crack typically reaches a depth of 50-120 pm. The individual
panels are then separated by the application of a bending stress for driving the median crack completely through
the glass thickness.
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