Enhanced Polymer Passivation Layer for Wafer Level Chip Scale ...

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Figure 4.11 Cross Section of SolderBrace coated dies with cracks in the solder near the pad surface 92
CHAPTER 5 FINITE ELEMENT ANALYSIS In order to develop a deeper understanding of the solder joint failure mechanism caused by the repeated thermal stress, a finite element based approach for estimating the thermal cycling reliability of chip scale packages is presented in this chapter. ANSYS modeling software was used to model the WLCSP structure to evaluate stress and deformation at various points across the device structure. 5.1 Finite Element Analysis (FEA) models Finite element analysis (FEA) is a computer based numerical technique for calculating the strength and behavior of engineering structures. It is based on the premise that an approximate solution to any complex engineering problem can be reached by subdividing the problem into smaller and manageable elements. The behavior of each individual element can be described with a set of equations. These equations will finally join into an extremely large set of equations that has the behavior of the whole structure. [79]. This technique has being widely used as a convenient and powerful tool for approximation of the solution to many engineering problems in disciplines such as electronics, biomedical, aerospace, chemicals, geotechnical, and manufacturing. In addition to the analysis in classical static structural problems, FEA is also used for such diverse areas as heat transfer, dynamics, mass transport, and stability problems. 93
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Enhanced Polymer Passivation Layer
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SolderBrace coatings were low tempe
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Table of Contents Abstract ........
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4.4 Failure Analysis ..............
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List of Figures Figure 1.1 Trends i
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Figure 3.17 SAC305 Reflow profile .
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CHAPTER 1 INTRODUCTION In the era o
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This effect changes the package to
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1.4 Solder Joint Fatigue Figure 1.2
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leading to the solder joint failure
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umped wafers. The coating is stenci
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11 Bumped Wafer Print over ball Pre
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2.1 Chip Scale Package Technology C
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Mountable with conventional assembl
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Figure 2.3 Cross section of a typic
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Table 2.1 Comparison between tradit
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In-Situ Bumped Wafers Placed Prefor
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of solder joint failure, and they o
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(a) (b) Figure 2.8(a). Metalized ph
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"underfilled" structure distributes
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have generally been the modificatio
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are “low temperature” wafer lev
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2.3.4 Optimized SolderBrace Materia
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CHAPTER 3 WLCSP DIE FABRCIATION In
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Table 3.1 Test Die used for Reliabi
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Figure 3.4 Fabrication Process Flow
Page 53 and 54: spin coating. A layer of light sens
Page 55 and 56: layer, is investigated as a potenti
Page 57 and 58: 10. Final cleaning: After the passi
Page 59 and 60: Cyclopentanone, a colorless liquid
Page 61 and 62: used to check the basic spin and ph
Page 63 and 64: Figure 3.7 SolderBrace film thickne
Page 65 and 66: 6. Post-UV exposure bake: This step
Page 67 and 68: 8. Pattern characterization: The su
Page 69 and 70: offers the optimum flux release cha
Page 71 and 72: fatigue resistance, lower cost SAC
Page 73 and 74: Figure 3.12 Solder Ball Placement M
Page 75 and 76: of solder balls to the holes on the
Page 77 and 78: of thermal shock. If the temperatur
Page 79 and 80: Figure 3.17 SAC305 Reflow profile -
Page 81 and 82: foaming and high performance cleane
Page 83 and 84: - Polish clean: used the optimized
Page 85 and 86: Figure 3.22 SolderBrace printed waf
Page 87 and 88: Voids Figure 3.25 SolderBrace Mater
Page 89 and 90: cutting speed was set at a low valu
Page 91 and 92: Figure 4.2 Process Flow of Board As
Page 93 and 94: pitch, and bump diameter), and subs
Page 95 and 96: 4.2.4 X-Ray Inspection Figure 4.5 R
Page 97 and 98: Figure 4.6 Air to air thermal cycli
Page 99 and 100: Figure 4.7 Thermal Cycling Setup 87
Page 101 and 102: 4.4 Failure Analysis The main purpo
Page 103: Figure 4.10 Pad cratering failure o
Page 107 and 108: 5.1.1 Modeling Approaches Due to th
Page 109 and 110: are shown in Figure 5.2. However, t
Page 111 and 112: 5.1.2 Material Properties Many pack
Page 113 and 114: strain rate sensitivity. The evolut
Page 115 and 116: Morris et a1 [96] used a double pow
Page 117 and 118: focus on the time-dependent effects
Page 119 and 120: 5.2 Modeling Procedure In this proj
Page 121 and 122: Figure 5.6 The diagonal symmetry mo
Page 123 and 124: 5.2.3 Meshing Table 5.2 Anand const
Page 125 and 126: direction, but that the surface is
Page 127 and 128: PREP7 tref,398 ! set zero strain te
Page 129 and 130: 5.2.7 Thermal Fatigue Life Predicti
Page 131 and 132: CHAPTER 6 CONCLUSIONS Wafer level c
Page 133 and 134: References 1. Future Trends in Elec
Page 135 and 136: 23. Electronic Packaging and Interc
Page 137 and 138: 48. Ultra Low Stress and Low Temper
Page 139 and 140: 70. Factors for Successful Wafer-Le
Page 141 and 142: 92. Microstructural Dependendence o
Page 143: 111. Nonlinear Analysis of Full Mat
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