Reliability Study of FCBGA Package

摘要

Reliability of Flip Chip Ball Grid Array (FCBGA) with multiple layer and high density build up organic substrates for higher density interconnect and signal integrity is studied. The package stability, board level reliability and thermal conductivity are enhanced by copper stiffener and nickel-plated copper lid. The substrate with features of core layer stacked up/lamination provides the flexibility for routing high I/O device from die center and reducing layer count. This high 1849 I/O package are constructed for potential high-end graphic, high-end serve, and microprocessor applications. To assess the reliability of the FCBGA and identify the process window in the early stage of product development cycle, a test vehicle (TV) with daisy chain (DC) construction, separation header to isolate die from substrate, and DC jump-out are designed for real-time monitoring of the failure cycle during he Accelerated Temperature Cycling test. Algorithm of Daisy Chain Match-making Methodology (DCMM) is developed to facilitate the design of matching DC of the TV to the DC of package. A statistic methodology was implenented from our earlier study. This paper will briefly describe this methodology to consolidate the package and board level reliability assessment to facilitate the potential of shortening the product development cycle. Design of Experiment (DOE) is extensively used from process development to package reliability study. Laser scanning is used in the pre-processing stage to assess the package flatness. With reflow-emulated thermal process applied on the FCBGA, the Shadow Moire was also used to monitor the package warpage along with site coplanarity investigated by surface mapping of 5DX. Fatigue fracture mote and life cycle will be analysis by 5DX, dye penetrant, TDR, failure analysis, and Webull distribution of the failure. Three types of reliability tests are conducted to study the test board and via integrity and solder joint reliability. Interconnect Stress Test is conducted to scan the reliability of trace and via in the TV. Test method and its advantage are illustrated. Two major fracture modes are studied by checking against a tentative failure criterion. Repetitive torsion test similar to Mechanical Deflection System was used as a quick assessment method for response of reliability of the solder joint. Accelerated Thermal Cycling is in progress on samples from a full-scale DOE with package, PCB and process variables.