Uniform Metal Droplet Controllable Printing Technology For Bump Array Used In Electronic Packaging

Due to the electronic devices has become miniaturization,multifunction,and integration,the electronic packaging structure changed from in-line package,quad flat package to flat bump package.The solder bump array is utilized in this packaging structure for electronic connection.Thus,how to fabricate the solder bump array with precise location and consistent height become the key problem for the electronic packaging development.The uniform droplet spraying technology,based on the additive manufacturing,provides a low cost and high flexibility method for manufacture solder bump array,which has a great potential applications in the electronic packaging.However,the process of fabricating solder bump array using uniform droplet spraying technology is significantly influenced by various factors and coupling fields,which involves the metal droplet fluid dynamics and heat transfer behaviors.It is difficult to print uniform height solder bumps directly.Based on the theoretical analysis,numerical simulation,and experiment research,the effect of process parameters on the droplet ejection was studied and a method for controlling the droplet position precision was proposed.The fluid dynamics and heat transfer behaviors were analyzed.The influence factors on the final bump shapes were obtained.The source of bump height deviation was revealed.A method for printing precise location and consistent height solder bump array was presented.The present work laid the foundation for the application of uniform droplet spraying technology to microelectronic packaging.Based on the theory and experiment approach,a dynamics model was developed to predicting the droplet velocity and location.The effect of process parameters on droplet ejection was studied and the parameter range for producing the single droplet was obtained.After analyzing the droplet lateral instability reason,the method for controlling the droplet deposition accuracy was first proposed,and the parameter map was calculated theoretically.Droplets were generated stably and precisely based on the above researches,which provided the experimental basis for printing solder bump array.The ineluctable underdamped oscillation of droplet was obtained by the dimensionless parameter calculation and high speed images.The droplet solidification behavior was also obtained by the numerical simulation.The effect of substrate material and droplet solidification rate on the final bump shapes was investigated experimentally in order to provide evidences on the height deviation of solder bumps.The effect of process parameters on the solder bump height deviation was studied and the deviation source was analyzed using experimental and statistical method.A method for suppressing the height deviation of solder bumps was first presented.A theoretical model for predicting bump height deviation was developed and the deviation transfer from the droplet diameter to bump height was revealed.The solder bump array with precise location and consistent height was successfully printed.The method for direct printing multi size bumps based on the single droplet generator was proposed,which provides guidance for the industrial application of uniform droplet spraying technology.