Basic Study On Ultrasonic Vibration Assisted Underfill Process For Flip-chip

With the development of automotive electronic technology,the widespread adoption of electronic products has become a competitive mean of the automotive industry.The chips used in electronic products are mostly flip chip,and its packaging reliability has become particularly important.At present,underfill is an important process of flip chip encapsulation because of its great impact on the reliability of the packaging.In electronic manufacturing industry,the requirements of high-density,large-size flip chip are getting higher and higher.So the capillary-driven underfill process is suffering from the manufacturing problems of insufficient filling force and long curing cycle.In order to overcome the two problems in the capillary-driven underfill process,a novel ultrasonic vibration assisted underfill process for high density flip chip encapsulation is proposed.Firstly,the effect of ultrasonic vibration on the underfill process of flip chip was studied by the combination of experiment and simulation in this thesis.In the experimental process,the experimental platform for ultrasonic vibration assisted underfill was established.In the simulation process,the finite element model of ultrasonic vibration assisted underfill was established based on the ANSYS software to simulate the flow of the encapsulant.Influences of the ultrasonic parameters and the height of the gap on the flow of the encapsulant were analyzed.Finally,the curing process of epoxy resin encapsulant was observed by differential scanning calorimetry(DSC).Based on the Kamal autocatalytic cure kinetic model,the epoxy resin encapsulant curing reaction model was established.In this cure kinetic model,by contrasting with or without ultrasonic vibration in two cases,the effects of ultrasonic vibration on the curing process of epoxy resin encapsulant were investigated.Through the study of this thesis,we can see that ultrasonic vibration can accelerate the flow of encapsulant in the gap during the underfill process.When the frequency and the amplitude of ultrasonic vibration was higher,the encapsulant can flow faster in the gap.When the gap height was smaller,the ultrasonic vibration accelerate effect was more obvious.During the curing process,the ultrasonic vibration was applied to the encapsulant.Then,the activation energy and the pre-exponential factor were reduced to promote the curing reaction,and the time of the curing process is reduced.In this thesis,combined with the traditional flip chip underfill process,the experiment platform of ultrasonic vibration assisted underfill process was established.Through the causal correlation analysis with the experimental results,effects of ultrasonic vibration on the improvement of the underfill process were studied from the aspects of filling the gap and curing.The research results of this thesis can provide some theoretical basis and practical guidance for the improvement of the underfill process in actual production.