Key Takeaways
- Accurate simulations now include gravity to better predict strip warpage in electronic packages during the assembly process.
- Results show that gravity significantly influences warpage after flip chip attach (FCA) but less so after post mold cure (PMC).
- Factors like substrate geometry and the presence of cores or slots in strips are crucial in determining warpage outcomes.
The mechanical behavior of electronic packages plays a critical role in their assembly, particularly concerning strip warpage, which can affect manufacturability and yield. Recent simulations have included gravity to better predict warpage levels, addressing discrepancies between simulated data and actual measurements.
Traditional simulations often omit the effect of a package’s weight under gravitational force. While this assumption may be applicable in some scenarios, it falls short when simulating realistic conditions post-assembly. To improve accuracy, gravity was integrated into the simulations to more effectively match actual warpage results. Initial studies indicated that incorporating gravity into panel warpage simulations significantly reduced discrepancies, especially for larger panels.
This comprehensive study focused on refining simulations for strip warpage, utilizing models calibrated with real warpage data from various pre- and post-mold strips. Key parameters included substrate geometry, stiffness variations, and their respective reactions to gravitational force.
Simulation Setup and Methodology
The simulations were executed using Ansys Workbench, applying a quarter symmetric model comprising the strip and a supporting table. Materials used in simulations mirrored those in actual strips to ensure accurate weight representation. Contact conditions were implemented to mirror real-world interactions between the strip and the table surface.
By applying gravity, it became evident that it influenced warpage significantly post-FCA, while its impact diminished after PMC. Notably, strip geometry also affected outcomes; the study analyzed different configurations, including coreless and cored strips, with and without slots.
Validation of Simulations
Warpage measurements taken after the flip chip attach and post-molding were compared against simulation results. It was found that simulations incorporating gravity closely aligned with actual measurements at both stages, with gravity contributing significantly to reducing warpage in strips after FCA. Without gravity, simulations produced exaggerated warpage values far removed from reality.
Key Influencing Factors
- Effect of EMC: The inclusion of an epoxy molding compound (EMC) minimized warpage discrepancies, particularly during the PMC phase, as it increased the strip’s structural integrity.
- Impact of Strip Size: Evaluating the CA95 and CA74 strip sizes showed that gravity’s effects remained consistent across different dimensions.
- Core vs. Coreless: Cored substrates exhibited reduced warpage compared to coreless configurations. The increased thickness and stiffness of cored strips rendered them more resilient to warpage induced by gravity.
Slot Presence in Strip Configurations
The effect of design elements like slots was also evaluated. While slots did not notably influence warpage during FCA, they were beneficial under gravitational influence during the PMC stage. When cores were present, whether in designs with or without slots, warpage consistently showed improvement.
In summary, integrating gravity into simulations of strip warpage significantly enhances predictive accuracy. The findings emphasize the importance of material properties, geometrical configurations, and structural design in managing warpage during electronic packaging processes. Understanding these factors can lead to better manufacturing strategies and enhanced product quality.
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