Study On Dynamic Response And Failure Of The Circuit Systems Under High G Value Impact

In the process of projectile penetratingthe protective engineering of target,the circuit systems should withstand high g value impact,and it needs to be protected by potting with epoxy.In order to further improve the potting-protection technology,this paper researched the dynamic response and failure mechanism of the circuit system under high g value impact.By comparing the dynamic response between different encapsulation and potting modes,the potting material’s ability to reduce stress wave amplitude were verified,and the differences of shock resistance for variouscircuit systems were analyzed.Besides,as a viscoelastic material the epoxy have the ability of shock absorber.By the simulation calculation,the impacts ofthe epoxy’s high-frequency relaxation time and impact pulse width on the frequency responses of the structure,dissipative energy,and dissipative time were analyzed by referencing orthogonal experimental design,and the theory about the viscoelastic materials’ capability of waning vibration under alternating stress was verified.Finally,the displacement difference between the pin and the chip and PCB plates is used as the "bridge",and the reliability of pin welding in different situations is calculated.Results show that:(1)the potting structure has obvious ability to reduce stress wave amplitude,but the stress concentration caused by the circuit board components structure,made the soldering parts of QFP chips to pins are easily injured;the solder joint in BGA package is easy to break;The transverse BGA packaging circuit board has relatively good shock resistance.(2)the shorter the high frequency response time of the potting material,the faster the dissipation speed of the sealing body to the internal mechanical energy,and the better the shock absorption effect;the larger the load pulse width is,the longer the response vibration period of the system is,the smaller the dissipation energy is,but the difference in dissipation time is not significant.(3)there are three main forms of pin welding failure,including the large amplitude of the impact load,which causes the deformation of the sealing body to extrude and "squeeze";The pulse width of the impact load is too small,resulting in too large amplitude of structure and "vibration fault" at the end of the impact;The high frequency relaxation time of the sealing material leads to too long vibration time and fracture.