Abstract
This paper presents a warpage analysis method that predicts the warpage behavior of electroplated Cu films on glass fiber-reinforced polymer (GFRP) packaging substrates. The analysis method is performed using the following sequence: fabricate specimens for scanning 3D contours, transform 3D data into curvatures, compute the built-in stress of the film using a stress-curvature analytic model, and verify it through comparisons of the finite element method (FEM) simulations with the measured data. The curvature is used to describe the deflection and warpage modes and orientations of the specimen. Two primary factors that affect the warpage behavior of the electroplated Cu film on FRP substrate specimens are investigated. The first factor is the built-in stress in a Cu film that explains the room temperature warpage of the specimen under no thermal process. The second factor is the misfit of the coefficient of thermal expansion (CTE) between the Cu and FRP layer, which is a dominant factor during the temperature change. The calculated residual stress, and predicted curvatures using FEM simulation throughout the reflow process temperature range between 25 and 180 °C are proven to be accurate by the comparison of the FEM simulations and experiment measurements.
Highlights
Electronic films and packaging substrate structures in electronic devices have been developed to be thinner and smaller than ever before [1,2,3]
To meet the current trend of electronic packaging devices, inevitably, the warpage problem has become a critical issue, which occurs from the residual stress accumulated from various fabrication and assembly processes [4,5], asymmetric design, and complex material used in the thin film structures for multifunction and high performance in electronics
The specimens were prepared in order to calculate the built-in stress of the Cu film layer and measure the warpage behavior during the temperature change
Summary
Electronic films and packaging substrate structures in electronic devices have been developed to be thinner and smaller than ever before [1,2,3]. To meet the current trend of electronic packaging devices, inevitably, the warpage problem has become a critical issue, which occurs from the residual stress accumulated from various fabrication and assembly processes [4,5], asymmetric design, and complex material used in the thin film structures for multifunction and high performance in electronics. A systematic basic study of the warpage of packaging substrate is necessary in order to analyze the warpage behavior mechanism and solve the warpage issues.
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