Under Fill Technology Analysis And Optimization For Flip Chip Packagings

Flip-chip technology is widely used in various advanced packages as a key interconnection method in the chip assembly,but the solder joint reliability problem caused by the particularity of its structure has also existed.As an effective method for improving the reliability of connection bumps,underfill is a widely used in this interconnection system,but the void and filler content are the two major defect of underfill process.These two defect will decrease the filling quality and product reliability.Therefore,study and optimized the underfill process parameter,to reduce the void and incomplete filling defect rate will significant improve the assembly yield,product reliability and cost.Based on the statistics and analysis of a large number of void failure samples,it is found that excessive moisture content in the filling system is the main cause of void defect.In order to effectively inhibit the moisture invasion in the filling process,a large number of experiments and data analysis are carried out in this paper,and effective process optimization conditions are summarized.In order to solve the problem of glue mismatch,this paper establishes a standard glue dispensing model based on the actual filling standard and the dispensing process,and then proposes a new glue dispensing calculation method according to the established glue dispensing model.This method can calculate the glue quantity required by the product according to the actual dispensing state and improve the accuracy of glue dispensing.The experimental verification and statistics of production data show that the optimized operating conditions and methods can effectively reduce the incidence of voids and glue mismatch in the underfill.According to the statistical data,the incidence of void decreased from 0.478% to0.317%,decreased by 33.8%,the incidence of glue mismatch decreased from 0.28% to 0.16%,decreased by 43%,and the waste of glue decreased by about 17.8%.