Abstract
This paper studies the three dimensional (3D) simulation of fluid flows through the ball grid array (BGA) to replicate the real underfill encapsulation process. The effect of different solder bump arrangements of BGA on the flow front, pressure and velocity of the fluid is investigated. The flow front, pressure and velocity for different time intervals are determined and analyzed for potential problems relating to solder bump damage. The simulation results from Lattice Boltzmann Method (LBM) code will be validated with experimental findings as well as the conventional Finite Volume Method (FVM) code to ensure highly accurate simulation setup. Based on the findings, good agreement can be seen between LBM and FVM simulations as well as the experimental observations. It was shown that only LBM is capable of capturing the micro-voids formation. This study also shows an increasing trend in fluid filling time for BGA with perimeter, middle empty and full orientations. The perimeter orientation has a higher pressure fluid at the middle region of BGA surface compared to middle empty and full orientation. This research would shed new light for a highly accurate simulation of encapsulation process using LBM and help to further increase the reliability of the package produced.
Highlights
The earliest integrated circuits were packaged in ceramic flat packs that is converted into dual in-line package (DIP)
This study discloses the importance of the solder bump arrangement in fluid flow filling time, pressure distribution and velocity distribution on the ball grid array (BGA)
The fluid flow simulation is validated by the experiment and it was proven that Lattice Boltzmann Method (LBM) is capable of predicting the fluid flow motion during the encapsulation process
Summary
The earliest integrated circuits were packaged in ceramic flat packs that is converted into dual in-line package (DIP). Due to limitations of DIP packaging for use on very-large-scale integration (VLSI) pin counts number, pin grid array (PGA) and leadless chip carrier (LCC) packages are introduced [1]. Ball grid array (BGA) is introduced to overcome the limitations of the PGA technology. The conventional flat packages consist of very thin and closely spaced pins that are damaged and require close control of the soldering process. BGA packages offer more advantages over PGA such as more interconnection pins rather than just perimeter, shorter lead that results in better performance at higher speeds and lower thermal resistance within silicon chip which allows more heat conducted out of the device faster [1]. Underfill process involves dispensing a controlled amount of material into
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