Method of cleaving a brittle material using a point heat source for providing a thermal stress

A method of determining optimum heating conditions for applying a pulse laser point heat source onto a strip of a brittle material at its position in the vicinity of a top of a crack of said strip for cleaving said strip by a thermal stress, the method comprising the step of:

• selecting at least one heating condition from among a non-dimensional pulse time of said pulse laser point heat source, a non-dimensional distance of said pulse laser point heat source from said tip of said crack, and a non-dimensional heating area so that a ratio of non-dimensional stress intensity factor to temperature takes lust or approximately a maximum value,
• wherein said ratio of non-dimensional stress intensity factor to temperature is defined by 2K1/{αET(πW)}, said non-dimensional pulse time is defined by 4κt/W2, said non-dimensional distance is defined by D/W, and said non-dimensional heating area is defined by W/D, where α is a linear thermal expansion coefficient of said strip, κ is a thermal diffusivity of said strip, E is a modulus of longitudinal elasticity of said strip, T is an increased temperature of a heating point of said strip, t is a pulse time of said pulse laser point heat source, W is a width defined as a distance between a cleaving-intended line and a side edge of said strip, R is a radius of a beam spot of said pulse laser point heat source, and D is a distance of a center position of said beam spot of said pulse laser point heat source from a tip of said crack of said strip.

A method of cleaving a strip of a brittle material along a predetermined cleaving line by applying a pulse laser point heat source onto said strip of said brittle material to locally apply a thermal stress in the vicinity of a tip of a crack of said strip, the method comprising the steps of:

• selecting at least one heating condition from among a non-dimensional pulse time of said pulse laser point heat source, a non-dimensional distance of said pulse laser point heat source from said tip of said crack, and a non-dimensional heating area so that a ratio of non-dimensional stress intensity factor to temperature takes just or approximately a maximum value,
• wherein said ratio of non-dimensional stress intensity factor to temperature is defined by 2K1/{αET(πW)}, said non-dimensional pulse time is defined by 4κt/W2, said non-dimensional distance is defined by D/W, and said non-dimensional heating area is defined by R/D. where α is a linear thermal expansion coefficient of said strip, κ is a thermal diffusivity of said strip, E is a modulus of longitudinal elasticity of said strip, T is an increased temperature of a heating point of said strip, t is a pulse time of said pulse laser point heat source, W is a width defined as a distance between a cleaving-intended line and a side edge of said strip, R is a radius of a beam spot of said pulse laser point heat source, and D is a distance of a center position of said beam spot of said pulse laser point heat source from a tip of said crack of said strip;
• and
• cleaving the strip by applying the pulse laser point heat source onto said strip under the selected heating condition.

A method of cleaving a strip of a brittle material along a predetermined cleaving line by applying a pulse laser point heat source onto said strip of said brittle material to locally apply a thermal stress in the vicinity of a tip of a crack of said strip, the method comprising the steps of:

• selecting at least one heating condition from among a non-dimensional pulse time of said pulse laser point heat source, a non-dimensional distance of said pulse laser point heat source form said tip of said crack, and a non-dimensional heating area so that a ratio of non-dimensional stress intensity factor to temperature takes just or approximately a maximum value, wherein said ratio of non-dimensional stress intensity factor to temperature is defined by 2K1/{αET(πW)}, said non-dimensional pulse time is defined by 4κt/W2, said non-dimensional distance is defined by D/W, and said non-dimensional heating area is defined by R/W, where α is a linear thermal expansion coefficient of said strip, κ is a thermal diffusivity of said strip, E is a modulus of longitudinal elasticity of said strip, T is an increased temperature of a heating point of said strip, t is a pulse time of said pulse laser point heat source, W is a width defined as a distance between a cleaving-intended line and a side edge of said strip, R is a radius of a beam spot of said pulse laser point heat source, and D is a distance of a center position of said beam spot of said pulse laser point heat source from a tip of said crack of said strip;
• and
• cleaving the strip by applying the pulse laser point heat source onto said strip under the selected heating condition.