Research On The Key Mechanical Problems Of IC Packaging Molding Process

The package of integrated circuit is used to form encapsulation on a semiconductor in-tegrated circuit chip.Plastic molding process and mold is important means and equipment of the semiconductor devices after the procedure.With the development of microelectronic packing tended to miniaturization,pin number is from tens to hundreds.The gap,in this narrow space,is small between the leads.Gold wire skewing is one of the most important defect in the molding process of microelectronic packaging.At the same time,when the IC element develop toward the thin element and high density, exploring the wire skewing analysis will become more difficult and challenging.The traditional injection molding theory cannot precisely describe the forming process, because the micro scale effect has a greater influence on the forming.In addition, the residual stress has a great influence on plastic parts,so we study residual stress from the angle of the pressure release resulting in plastic parts expansion and cooling resulting in plastic parts contraction.The application of professional mold flow analysis software are useful for the experiment, and to be able to verify experiment each other.Through a comparison of before and after packaging chart, it is a scientific analyzing method with the theoretical CAE combination, which can directly reflect the real wire skewing of package.The plastic packaging of SSOP-20 L integrated circuit block is the main object of study.On the base of ensuring stable condition,compare the wire offset data when the plastic mold gate inset has same thickness(0.25mm) and different incident angle(20o、30o、40o、50o).According to that,we can obtain different gate parameters influence on the deformation degree of wire.Besides that,we also can optimize plastic mold gate parameters and thecondition of molding process.Using MOLDFLOW and ANSYS software,it will commonly analysis the skewing size in the encapsulation process.CAE will be used to analysis wire skewing law and its influencing factors in microelectronic packaging.I use the same way experimental method combined with CAE,studying effects of processing parameters on the residual stress.By the stress polariscope,we can qualitatively analyze the stress distribution trend in plastic packaging material,and quantitatively analyze the effect of process parameters on residual stress by the ANSYS fluid solid coupling module.Based on the experiment and analysis of CAE, I find that when the thickness of the ga te is 0.25 mm, the average offset of gold increases firstly with the increase of the incidence angle,and when the incidence angle is above 30o decreases with the increase of incident angle.In the set range, increasing the holding pressure and prolonged injection time can all reduce the residual stress.Besides that,residual stress rangeability of Prolonged injection time is not as good as residual stress rangeability of increasing the holding pressure,which shows that holding pressure is the main factor influencing the residual stress, injection time is only a secondary factor.At the same time,residual stress is mainly concentrated in the midlle part,because epoxy resin high glass transition temperature and mold temperature and mo ld temperature are basically the same.