SMTA International Conference Proceedings


Authors: Srinivasa Aravamudhan, Marc Apell, Joe Belmonte, G
Company: Intel Corporation
Date Published: 9/24/2006   Conference: SMTA International

Abstract: One of the areas in lead-free assembly process that need more investigation is the effect of oxygen concentration during reflow on passive resistors and capacitors. Although studies to minimize the effect of tombstoning have been done on numerous occasions, there is lack of experiments/data to study the effect of various levels of O2 on tombstoning. This study will allow us to understand the interaction between O2 levels and the occurrence of tombstones. Additionally, this study will help us to provide process recommendations for the assembly of passive resistors such as 0402s and 0201s with lead-free materials. Experiments will be performed to identify the effect of oxygen concentration during reflow on tombstoning for passives such as 0402s and 0201s. In addition, we will develop understanding of process conditions that produce tombstoning for lead-free pastes. The questions that will be answered in this study: 1. What is the effect of O2 on tombstoning and what ppm of O2 minimizes its occurrence 2. Understand the effect of pad size, solder paste, stencil design and reflow parameters on tombstoning in the assembly of 0402s and 0201s for lead-free materials This paper will discuss the results from this study and provide statistically valid data to answer these questions. Key words: Lead-Free, Tombstone, Reflow Process, Nitrogen Reflow, 0201s, 0401s, and Passive Resistors

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