新穎底部填膠材料對覆晶封裝可靠度之研究

Abstract

針對兩種bisphenol樹脂基材之底部填膠分析其重要的熱機械性質(thermo-mechanical properties)；利用熱機械分析(TMA)、示差掃描熱量計(DSC)、奈米壓痕儀(NI)、四點彎矩(4PT Bending)和雙懸臂樑(DCB)試驗量測底部填膠的熱膨脹係數(CTE)、玻璃轉換溫度(Tg)、彈性模數(E)、硬度(H)、彎曲彈性模數(Ef)和界面強度(Gc)。 所量測底部填膠性質將利用ANSYS二維(2-D)有限元素法(FEM)模擬覆晶封裝體中銲錫球(solder)和內連層(ILD)的熱應力分布情形，並根據模擬結果預測覆晶封裝的可能失效部位及底部填膠影響可靠度的關鍵性質。 結果可發現模擬結果與熱循環試驗(TCT)結果有很好的相關性。對高鉛銲錫凸塊(high lead solder)而言，選擇低熱膨脹係數(CTE)和高彎曲彈性模數(Ef)之底部填膠可以有效提高其可靠度。 本研究並說明薄膜材料的界面強度量測方法，利用四點彎矩、雙懸臂樑試驗量測晶片內連層的薄膜之界面強度和底部填膠與晶片之間的界面強度。

The thermo-mechanical properties of two bisphenol resin-based underfill materials including coefficient of thermal expansion (CTE), glass transition temperature (Tg), hardness (H), Young’s modulus (E), flexure modulus (Ef) and adhesion (Gc) were measured and validated against vendor’s data by differential scanning calorimetry (DSC), thermomechanical analyzer (TMA), nanoindentation (NI), four-point bend (4PT Bending) and double cantilever beam (DCB), respectively. Underfill properties data were then used as the input for calculating the stresses at the bump and Cu-low-k structure two-dimensional finite-elements-method (FEM) simulation by ANSYSTM in order to predict the loci of potential failure and identify critical properties of underfill. Excellent correlation was established between the temperature cycling test (TCT) and stress simulation results. The results show that for high lead solder, underfill with low CTE and high modulus is preferred. Finally, the methodologies for characterizing thin-film adhesion such as four-point bending(4PT) and double cantilever beam(DCB) for measuring the fracture energy of interconnect and underfill/passivation interface were reported in this study.