Numerical Analyse Of The Dynamic Stresses Distribution In Adhesively Bonded Metal Joints

In this paper, a single-lap joints and electronic package to the common electronic QFP package containing the plastic joints as the main object has been studied by finite element method to optimize the distribution of joint stress and improve the joint strength, the plastic joints of the stress response and its impact factors under the dynamic load and load temperature have been investigated, the results indicated that:1) Based on the plastic model, the effect of the loading rate on stress distribution of single-lap joint was studied though high-level language of the APDL cycle process. The results shows that, the loading rate on joint stress distribution have a certain impact on termination of certain load: When loading rate is relatively larger, SEQV peak was smaller. Contrarily, loading rate is relatively smaller, SEQV peak was larger. The plastic joints possibly bear different loading rate in practical application, which has great significance of understanding the practical application of the plastic bearing joints.2) The effect of high or low-speed impact load on stress distribution of joints was studied using elasto-plastic model. The results show that, the stress of the most dangerous point in adhesive layer didn't change greatly with time under high-speed loading, which because when the hammer hit by stick-on, the adhesive layer was torn quickly. Under low rate loading, with the increase of the rate, the stress of the most dangerous point in adhesive layer increased. When the hammer was hit on the adherend, the stress of adhesive layer increased rapidly. The stress of adhesive layer has viscoelastic response to time after the collision.3) The effect of different levels of moisture in adhesive layer on the stress distribution of single-lap joint was studied by numerical simulation .The results showed that, With the increased level of moisture, the yield strength of adhesives decreased greatly; main load was born by the adhesive layer in fillet transferred to middle zone with the weak function of the fillet. Under the same condition, the load bearing of joint declines as the moisture level of adhesive layer increases.4) Based on the fracture mechanics model of a single-lap joint, the effect of crack length on the distribution of stress in a single-lap joint was studied. The results showed that, crack point SEQV equivalent stress gradually increased as the increase of the crack length, and the stress of the crack point is far greater than the stress of the adhesive layer in the central area of the overlap, thus the high-value stress of the crack point provided a driving to the expansion of the crack in the adhesive layer; studied on the relationship between the fracture gene of the type I and type II and the initial crack length and the size of the load, the results showed that, the fracture gene of the type I and type II gradually increased trend as the increase of the crack length; with the increasing load, I and type II-type fracture Factor was also gradually increasing trend. As the size of the load increasing, the fracture gene was also gradually increasing trend.5)Based on the viscous plasticity model, using the cycle process which workout by the APDL senior language, the first time studied on the effect of temperature loading rate, holding time and cycle times on the QFP spot interface stress in the wider application of the solder temperature cycle under 63Sn37Pb the impact by the numerical simulation. The results showed that, temperature loading rate had a great impact on 63Sn37Pb spot interface stress: the greater the temperature loading rate, the higher the peak stress; holding time had a certain impact on 63Sn37Pb spot interface stress: the longer the time, the higher the peak stress; the number of recycling also had the impact on the 63Sn37Pb spot interface stress, but the impact began weakened after the loop 10 times.6) Based on the multilinear kinematic hardening model, using the cycle process which workout by the APDL senior language, the first time studied on the interface stress and stress-strain loop which formed by different common packaging adhesive in the QFP Microelectronics Packaging under the temperature impact, pointed out: the interface stress between this three kinds of commonly used packaging adhesives and FR-4 board was very different, the SEQV equivalent stress in the adhesive point which formed by ASA acrylonitrile is minimum, would help improve the reliability of the connection in the electronic packaging device; after experiencing 10 times the temperature cyclic loading, the maximum of the stress accumulated which formed by ASA acrylonitrile was generally in the left chamfer and the right inner chamfer crossing.