【作者】 张振强；

【导师】 王晓东；

【作者基本信息】 大连理工大学 ， 机械电子工程， 2009， 硕士

【摘要】 将超声波塑料焊接技术引入微流控芯片的封装具有不引入外部介质、键合强度高、键合时间短、材料适用范围广的优势。但就超声波塑料焊接技术而言,人们对其机理的理解还不十分深入。研究超声波塑料焊接的机理,可以更清楚的理解微流控芯片超声波键合时材料的熔融行为和焊接参数对键合过程的影响,为实现高质量键合服务。因此本文就超声波塑料焊接的机理做了部分基础性研究工作。首先针对聚合物材料,提出了一种粘弹性力学模型,该模型以广义Maxwell模型为基础,借助Boltzmann叠加原理和“时-温等效性原理”,可以将聚合物的动态模量表示为温度和频率的函数。然而在利用“时-温等效性原理”将松弛曲线片段平移为松弛主曲线时存在平移不准确的问题,因此文中对“时-温平移方程”进行了修正。推导了周期应变载荷下的粘弹性产热方程,从中得出,粘弹性热是在一定的温度范围内很短的时间里产生的,且低温段的粘弹性产热并不明显。对承受静压力和高频振动载荷的带矩形导能筋的有限元模型进行了动力学仿真,结果显示角点处的瞬时摩擦应力和相对滑动速度可以达到很高的数值,从而提出低温段超声波塑料焊接的热源来自界面上的摩擦热的观点。分别对摩擦热和粘弹性热提出了相应的仿真策略,结果表明超声波焊接接头上的温度场为非均匀温度场,粘弹性热使材料内的温度在很短的时间内攀升到很高的温度。用热电偶温度传感器进行了超声波塑料焊接接头温度场的实际测量,所得结果与仿真结果具有类似的趋势。对不同焊接压力和振幅作用下的模型温度场进行了仿真,结果显示温升速率随焊接压力和振幅的提高而提高,且振幅的影响要大于焊接压力的影响。最后,针对塑料微流控芯片的封装给出了两种不同的导能筋形式,从机理方面分析了其可行性,并对该两种形式导能筋的芯片进行了超声波键合实验。更多还原

【Abstract】 It’s a modern thing that introduces ultrasonic plastic welding technology to the field of microfluidic chip encapsulation,which has some advantages,such as external substance free, higher bonding strength,shorter bonding time,wider applying material,etc.To the ultrasonic plastic welding technology,however,the joining mechanism is not well understood.Research on the mechanism helps understand the melting behavior and the effects of welding parameter on the welding process,which would greatly benefit welding quality improvement.Aiming at providing theories to the advanced implication of the technology,the dissertation focuses on researching the joining mechanism of ultrasonic plastic welding.Firstly,a practical viscoelastic model to the polymer material is proposed.Based on generalized Maxwell model and Boltzmann superposition principle and TTEP (Time-Temperature Equal Principle),the dynamic modulus could be expressed as the function of temperature and frequency.However,when shifting relaxation modulus segments of PMMA(polymethyl methacrylate) to gain a master curve,inaccuracy appears,so the normal Time-Temperature Shifting Factors is modified in the dissertation.The viscoelastic thermogenesis equation of viscoelastic material under periodical strain load is deduced.From the numerical solution it could be concluded that,viscoelastic heat is generated in a very short time in specified temperature range,and viscoelastic heat is not apparent at low temperature. Other heat generating mechanism may exist at temperature below T_g.Subsequently,kinetic simulation was proceeded to the Finite Element Model with a rectangular energy director, which bears both welding pressure and high-frequency vibrating loads.In the simulation, corner of the energy director produces high instantaneous friction stress and relative sliding velocity.So viewpoint was derived that the heat generating mechanism at low temperature is friction heat right at the interface.Simulating strategy to the friction heat and viscoelastic heat was put forward.The results showed that temperature field on the rectangular energy director is nonuniform,and viscoelastic heat makes the temperature rises in a very short time.To validate the proposed heat generating mechanism and the simulating method,experiments were proceeded with measurements of temperature tendency of energy director during welding process.Simulation of the temperature field when the welding parameters,that is welding pressure and amplitude,varies is proceeded,indicating that temperature rise rate tends to increase with the applied welding pressure and amplitude.At last,two kinds of energy director shape,triangular and rectangular,for the encapsulation of microfluidic chips is presented,and their feasibility is discussed theoretically.Encapsulating experiments of the two kinds of microfluidic chips were proceeded.更多还原