Accurate predictions of flip chip BGA warpage

Abstract

Organic flip chip BGA has been quickly adopted as the mainstream package solution for high speed, high density and high power ASIC and PLD. For these applications, both die and package dimensions are generally large. It is common to see dies over 25 mm and packages of 40 mm or larger. Therefore, warpage is a big challenge. A three-dimensional finite element model was developed to predict the warpage. The model includes substrate, underfill, die, thermal interface material (TIM), heat spreader, stiffener and adhesives. The model has consistently shown excellent accuracy. The average prediction error for a number of packages was less than 10%. The modeling techniques are presented in details in the paper. Using the model, various factors, such as materials and structures of heat spreader, die size and package size, and thermal interface materials were studied.