Numerical Simulation Study And Application Of Interface Delamination In High Density Electirc Packaging

With the more density of the electronic packaging, the film, which is the mechanical interconnection between IC and substrate, becomes thinner. It suffers more serious stress condition in the packaging process. With the trend of lead-free material application, the film would suffer more stringent reliability test. These inner and outer factors cause interface delamination, which is more serious in the high density package. Therefore, it is important to adopt the typical packages, develop numerical simulation study for interface delamination, and apply the numerical methods to delamination mechanism analysis and solutions.This paper studied the interface delamination in high density package, adopted two typical packages—chip on glass (COG) and chip scale package (CSP), developed advanced numerical simulation methods for interface delamination, applied the numerical methods to mechanism analysis, gave the methods to solve the delamination for different packages. The content and results are summarized as follows.Firstly, this paper adopted two typical packages—COG and CSP to study numerical methods, delamination mechanism and solutions respectively. The interface delamination study can be applied to other high density electric packages.Secondly, this paper developed several advanced numerical simulation methods. For the anisotropic conductive film (ACF) delamination of COG, the paper proposed novel non-linear and sequentially coupled thermal-mechanical method to solve the uncoupling of transient thermal-mechanical loadings in the previous packaging process modeling. This paper also proposed the equivalent particle method for ACF packaging simulation to model the numerous conductive particles. By the global-local method, the delamination study was implemented from mm scale to um scale. Meanwhile, for the die-attach (DA) film interface delamination of CSP during preconditioning test (one of the reliability test, including soaking and reflow), the paper proposed the moisture diffusion modeling method, named direct concentration approach (DCA), to simulate the moisture diffusion under varying ambient temperature and humidity. Also, this paper proposed simplified transient micromechanics-based vapor pressure model (STMVPM) to simplify the vapor pressure calculation inside electronic package.Thirdly, the COG process was simulated with advanced modeling methods, the IC warpage from global model was validated with the resolution of 93% by warpage measurement system, and ACF/glass interface was determined to be easier to delaminate by local model and IC shear test. Meanwhile, moisture diffusion and vapor pressure evolution during preconditioning test were simulated with advanced modeling methods, and the DCA was validated by analytical solution and independent variable method with the resolution of 97%. The feasibility of DCA application to CSP was validated by experiments. The STMVPM was validated by conditional criterion and micromechanics-based vapor pressure model.Fourthly, the relationship between IC warpage and ACF delamination was established with the dalamination mechanism analysis. The ACF delamination was induced due to the large difference of shrinkage and warpage between IC and glass substrate during cooling, which caused large residual shear and normal stress at ACF interface. The interface delamination located at the ACF/glass interface at the IC edge. Meanwhile, vapor pressure was determined as the major driving force for the DA film delamination with the analysis of moisture diffusion and vapor pressure evolution during preconditioning test.Lastly, with the parametric modeling and delamination mechanism analysis for COG packaging process, ACF delamination can be avoided by decreasing bonding head temperature, increasing glass substrate temperature, decreasing bonding temperature difference, thinning IC thickness, shortening IC length, thickening glass substrate thickness, improve adhesion between ACF and glass. Meanwhile, with the DA film delamination mechanism analysis, moisture diffusion and vapor pressure evolution modeling, and test validation, DA film delamination can be solved by thinning substrate thickness and extending in-line baking of reflow process.The interface delamination study based on the COG and CSP can be applied to other high density electric packages. The non-linear and sequentially coupled thermal-mechanical method can be applied to the packaging process modeling under thermal-mechanical loadings. The equivalent particle method can be applied to the ACF bonding simulation. The DCA and STMVPM can be applied to moisture diffusion and vapor pressure evolution modeling for high density electric package. The methods to solving film delamination in this paper have been validated in the COG and CSP.