Blade breakage reduction in CSP singulation process

Abstract

To reduce blade breakage problem in CSP (Chip Scale Package) singulation process. Blade breakage problem at CSP singulation process leads to major yield loss contribution to the IC (Integrated Circuit) assembly production. The high rate of blade breakage post several problems such as increased reject rate, higher blade usage, increased machine down time, and production cycle time not meeting expected target. The research is conducted by using CSP saw singulation process of AMD (Thailand) Ltd. as a case study. The equipment used in singulation process is Intercon Tools Solid BGA Sawing System Model DS-8800 Series made by Intercon Technology. The methodology of the research was to set up a quality circle team consisting of members from process engineering, preventive maintenance, production operators and technicians, and vendors. The team participated in a brainstorming session to identify possible causes of blade breakage by applying a cause and effect diagram and FMEA (Failure Mode Effect and Analysis). The potential solutions and various alternatives were developed and implemented in sequence to solve the chronic problem. The methodology also involves the use of statistical tools such as factorial design to study the effectiveness of a new saw sequence and a new high water pressure nozzle design and ANOVA (Analysis of Variance) was also applied to confirm on the cutting quality. Process capability analysis (Cpk) was performed to determine the variation of CSP singulation process after the developed solutions were implemented. The conclusions from factorial design of experiment suggested that implementing a new 4 channel cutting sequence had successfully eliminated the blade breakage problem and together with a new dual high-pressure nozzle design had minimized dented ball rejects caused by scrap remains. There was zero blade breakage after long production run. Furthermore, ANOVA analysis indicated there was no impact on cutting quality from the changes. The Cpk of critical parameters such as package dimensions and ball array offsets also met the expected goal of 1.5. The tangible benefits of thesis include an improvement of MTBA (Mean Time Between Assist) 12 times, reduction of maintenance time by 60%, reject reduction by 63%, blade life improvement by 2.3 times, and estimated total cost saving to be worth US$ 147,201 per year. Other benefits are elimination of spindle seizure that can cause CSP production line to shut down due to AMD Thailand operating as a modular production line, reduction of reworking effort, supporting ball inspection sampling project, technical skill improvement in dicing dynamics and shorter cycle time. The most critical benefits of all is minimizing potential catastrophic issue where package or die crack units could escape final inspection and released as good product to IC manufacturer customers.