Abstract: Shadow mask, an electron sieve mounted in the front of CRT in color TV, is inevitably heated by the captured electrons. Thermal deformation leads to deflection of electron beams, which will spoil color purity. This paper discusses the relation between the thermal deformation of a shadow mask and its slot size, and predict the beamlanding shift. An improved equivalent structural elastic modulus with orthogonal anisotropy is proposed to construct the finite element model for the mask. The equivalence requires that the same bending stiffness across both slot and bridge are the same, and the extensional stiffness between the model and the prototype are also the same. This paper takes a large number of different representative units from the entire shadow mask according to the local geometries and erosion features of the slots to localize the equivalent elastic modulus in our model. In addition, this paper takes advantage of asymptotic method to confirm the effects of the modulus on deformation. Simulation results agree with the practice, which can be used to guide the mask design.

Key words: asymptotic method, beam landing shift, FEM, thermal deformation, shadow mask