SMTA International Conference Proceedings


Authors: Bala Nandagopal, Sue Teng and Mason Hu
Company: Manufacturing Technology Group - Cisco Systems, Inc.
Date Published: 10/11/2007   Conference: SMTA International

Abstract: The objective of this study is to determine the shelf life of Organic Surface Protectant (OSP) finished Printed Circuit Boards (PCBs) under various storage and aging conditions. A test vehicle with a 32.5mm Ceramic Ball Grid Array (CBGA) and a through hole design is used for the study. The experiment variables include PCBs from four suppliers (A, B, C and D) that were stored in two different storage conditions (sealed and open packages) with four aging periods (3, 6, 9 and 12 months). Surface mount and wave solder assembly for all the aging and storage conditions was performed at the end of the 12month aging period.

The boards were subjected to Accelerated Thermal Cycling (ATC) of -40/125 degrees C with 20 minute ramps and 10 minute dwells per IPC9701. The characteristic life (?) results indicated that all the aging periods and storage conditions had comparable reliability except for the 12 month open package storage condition which showed a significant drop in solder joint reliability. However, comparing the 1% life showed that both open and sealed packaged PCBs had similar reliability. PCBs from 3 of the 4 suppliers showed similar performance with respect to solder joint reliability, while the 4th supplier (A) consistently outperformed the rest by about 25%. The Mechanical shock testing performed at 200g and 340g with in-situ resistance and strain monitoring showed that there was no degradation in solder joint reliability due to any of the variables studied. The only failure mode observed was pad cratering on the PCB side. Overall, we may conclude that there is no degradation to the solder joint reliability for OSP PCBs stored in the sealed and open package conditions up to one year.

Key words: PCB, OSP, Shelf life, Reliability

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