Based on the numerical analysis theory of laser welding instability of thin plate

the simulation model of external instability deformation of rectangular grid structure was established by extracting the inherent strain distribution of ultra-thin plate cross structure after laser spot welding. The first positive eigenvalue buckling mode of the cross joint was calculated

which was shown as deflection deformation.With the increase of heat input

the out-of-plane deformation of the joint increases obviously

and the deflection direction changes. Based on the eigenvalue buckling deformation analysis of the grid structure under two kinds of welding sequence

it was found that there is an obvious downward deviation at the joint of the first thin plate under the condition of welding sequence 1

and the deformation deflection was 27μm. Under the welding sequence 2

the buckling eigenvalue of the thin plate was smaller

and the overall deflection of the thin plate increased. With the increase of the number of solder joints

the instability deformation is more likely to occur

which is shown by the continuous decrease of the buckling characteristic value of the thin plate. The coupling of buckling deformation near the solder joint will significantly increase the out-of-plane deformation of the grid structure in the middle layer compared with the top and bottom areas.