Patent ID: 7134582

Claim:
A substrate ( 1 ) with a first ( 11 ) and a second side ( 12 ) and a thickness ( 20 ), which substrate ( 1 , 101 ) is provided at its first side ( 11 ) with: a first groove ( 4 ) having a depth ( 24 ) with respect to the first side ( 11 ), characterized in that the first groove ( 4 ) has a protrusion ( 3 ) in an initiation point ( 19 ) for forming a crack; a second ( 5 ) and a third groove ( 6 ), each having a depth ( 24 ) with respect to the first side ( 11 ), wherein the first groove ( 4 ) intersects the second and the third groove ( 5 , 6 ) in a first and a second point of intersection ( 17 , 18 ), respectively, the initiation point ( 19 ) lies between the first and the second point of intersection ( 17 , 18 ), and the second and third grooves ( 5 , 6 ) at the first and the second point of intersection ( 17 , 18 ) are deepened to a depression depth ( 22 ) greater than the depth of the first, the second or the third groove.