Research On Delamination Of SOP Type Plastic Packaging Devices

Plastic packaging devices are widely used in the civil field due to their light weight and low price.However,in the military and aerospace fields with high reliability requirements,domestic plastic devices occupy a smaller share.The fundamental reason is that there are still serious reliability problems in plastic devices.The most typical is the internal delamination failure of the plastic device.Therefore,this paper takes SOP-8 plastic devices as the research object.Research is carried out through a combination of experimental research and simulation.Firstly,the failure analysis of the laminated device is carried out to determine the process and specific delamination location of the delamination.The delamination failure mechanism is experimentally verified.Then,the packaging process of the plastic device is simulated and analyzed,and the injection molding process parameters are optimized.Finally,the temperature cycling process of the plastic device is simulated and analyzed.Based on the modified simulation model,the package structure and packaging material are optimized and analyzed.The specific research and conclusions are as follows:（1）Research and experimental verification of delamination failure analysis of plastic devices.With the help of ultrasonic scanning electron microscope and other experimental equipment,the key links in the entire production process of plastic devices are analyzed.It was determined that there was significant delamination after the injection molding and temperature cycling processes.There is a clear pattern of delamination in the array of plastic devices.That is,after injection molding,the delamination position is the surrounding and middle two columns of the plastic device array.After temperature cycling,the delamination area of the molded device is expanded on the original basis.At the same time,new delamination appear at the pin or base island location.Further analysis of the delamination of individual devices determines that the specific delamination is between the leadframe and the molded body.（2）Injection molding process simulation analysis and process parameter optimization.Based on Moldex3D software,the model is established to simulate the injection molding process.The number of pores and warpage deformation were selected as the process quality evaluation indexes.The influence of mold temperature,injection pressure,holding pressure,holding pressure and injection speed on process quality was analyzed by the one-factor method.The results show that the injection speed has the greatest influence on the number of pores.The larger the injection speed,the fewer the number of pores.The mold temperature has the greatest influence on the amount of warpage deformation.The lower the mold temperature,the smaller the amount of warpage deformation.On this basis,the orthogonal test of L₂₅（5⁶）is designed.The gray correlation method was used to comprehensively consider the two evaluation indexes of the number of stomata and the amount of warpage deformation.Combined with the range analysis method,the optimal combination of process parameters is finally obtained as mold temperature 165°C,injection pressure 40 kg/cm²,holding pressure 20 kg/cm²,holding pressure time 250s,and injection speed 9mm/s.The number of pores in the optimized process parameter combination is 244,which is 3 fewer than the default process parameters.The warpage deformation is0.08292mm,which is 0.00685mm less than the default process parameters.（3）Temperature cycling simulation analysis and package optimization.A single device model was established and the temperature cycling process simulation analysis was carried out to obtain the stress field distribution results.The maximum equivalent stress is 264.43 MPa.Further analysis of the stress field shows that there is a part of the area around the adhesive layer in the base island of the lead frame with large stress.The stress field distribution and the delamination of the plastic device were compared,and the simulation results were in line with the actual stratification.Based on this simulation model,the package structure and packaging material are optimized separately.1)In terms of package structure,the chip volume,adhesive layer thickness and plastic body thickness are optimized and analyzed.The chip volume and adhesive layer thickness were basically positively correlated with the maximum equivalent stress,while the change of plastic body thickness had little effect on the maximum equivalent stress.When the thickness of the plastic sealing body is 1.43mm,the stress value is minimal.2)In terms of packaging materials,four different plastic sealing materials and lead frames were selected for simulation analysis.The coefficient of thermal expansion and elastic modulus of the material have a great influence on the maximum equivalent stress in the simulation.That is,the greater the coefficient of thermal expansion and the greater the modulus of elasticity,the greater the equivalent stress.Among the materials selected,the SMT-B-1F model plastic sealing material and the lead frame made of Alloy-42 material have the lowest equivalent stress.Through the above research,this paper determines the specific process of delamination of plastic devices,the specific delamination location and the delamination law.The mold flow simulation model is established to study the influence of process parameters on process quality,and the current process is optimized and analyzed.The temperature cycle simulation model is established,and the stress field distribution is in line with the delamination position of the actual device.Based on this model,the package structure and packaging material are optimized and analyzed.The above research results have certain engineering significance for improving the reliability of plastic device products.