Page 8 - Wire Bonding in Microelectronics

Co n t e n t s vii

4.2.4 Effect of Metallurgy and Bonding
Processes on the Bond
Pull Force . . . . . . . . . . . . . . . . . . . . . . . 86
4.2.5 Effect of Wire Elongation on Bond Pull
Force (Primarily for Large-Diameter
Al, but also for Au Wire Used in Ball
Bonding)[4-9] . . . . . . . . . . . . . . . . . . . 88
4.3 Ball-Bond Shear Test . . . . . . . . . . . . . . . . . . . . . 92
4.3.1 Introduction . . . . . . . . . . . . . . . . . . . . . 92
4.3.2 Apparatus . . . . . . . . . . . . . . . . . . . . . . . 93
4.3.3 A Manual Shear Probe As an Aid in
Setting Up Ball Bonder (For
Laboratory Use) . . . . . . . . . . . . . . . . . 95
4.3.4 Interferences to Making Accurate
Ball-Shear Test Measurements . . . . . 97
4.3.5 Ball-Shear Force versus Bonded
Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
4.3.6 Effect of Gold-Aluminum
Intermetallics on the
Shear Force . . . . . . . . . . . . . . . . . . . . . . 107
4.3.7 Pluck Test, Pry Test, Flip Test, etc.
(Failure Analysis Technique) . . . . . . . 107
4.3.8 Comparison of the Ball-Shear and the
Bond-Pull Tests . . . . . . . . . . . . . . . . . . 109
4.3.9 Applications of the Ball-Shear
Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
4.3.10 Shear Test for Wedge Bonds . . . . . . . 112
4.3.11 Ball-Shear Test Standardization . . . . 115
4.4 Evaluating Both the Ball and the Wedge Bond
on a Single Wire . . . . . . . . . . . . . . . . . . . . . . . . . 116
4.5 Thermal Stress Test for Au-Al Wire Bond
Reliability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
4.6 Future Issues in Wire Bond Testing . . . . . . . . 117
Appendix 4A Typical Failure Modes of the
Ball-Shear Test (Failure Mode 2 Is the
Normal Desired Test Result) . . . . . . . . . . . . . . 118
Appendix 4B The Nondestructive Bond
Pull Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
4B.1 Introduction . . . . . . . . . . . . . . . . . . . . . 120
4B.2 Metallurgical and Statistical
Interpretation of the NDP Test . . . . . 121
4B.3 Assessment of Any NDP Test-Induced
Metallurgical Defects . . . . . . . . . . . . . 123
4B.4 Limitations of the NDP Test . . . . . . . 124