Pan Pacific Symposium Conference Proceedings


MECHANICAL STRESS CONTROL AND MANAGEMENT IN THE ASSEMBLY PROCESSES FOR Sn-Pb AND Pb-FREE SYSTEM *PHASE I - A METHODOLOGY FOR...

Author: Hana Hsu et al.
Company: Mitac International Corp.
Date Published: 2/10/2004   Conference: Pan Pacific Symposium


Abstract: Ultra high-density printed circuit board layout to fulfill miniaturization of die size and electric and signal performances have imposed great challenging in advancement of manufacturing technology and process control. One of the most critical process developments is to ensure solder joint integrity under various mechanical and thermal processes in surface mount and mechanical package insertion. Mechanical stress and strain become an essential assessment in front-end process development as well as on-line process real-time monitoring.

Strain measurement by strain gage was developed and used in material test for decades. Recent applications on PCB assembly have shown great advantage to monitoring the strain response on PCB surface under mechanical force field. Study of quasi-brittle and instantaneous fracture solder joint under these external loads also raise great interest in the recent electronic industry. In this study, this approach was widely used in the PCB assembly to identify potential risk in various assembly processes, handling, touch-up assembly and mechanical insertion, and testing etc. such that these damaging stress can be reduced or eliminated immediately.

An advanced research methodology will be also proposed to correlate the loading speed and deflection to the ATC reliability scale to further resolve the inadequate understanding of residue stress or permanent displacement under external force field and their relationship to the reliability scale. Above approach was used in existing assembly process in eutectic soldering and will be applied in lead-free process development and control as well.

Key word: BGA, strain gage, SMT, mechanical stress.



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