Capillary Profiles Affecting Ball Bond
Hole Size (H)
is determined based on the Wire Diameter (WD) to be used in a given application. Typically, the ratio is around 1.2X to 1.5X of the WD. A smaller hole size ratio is necessary for ultra-fine pitch application to compensate for the smaller chamfer diameter requirement.
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WD, Given Wire Ø (µm / mil) |
H, Hole Size Ø (µm / mil) |
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18 / 0.7 |
23 / 0.8 - 25 / 1.0 |
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20 / 0.8 |
25 / 1.0 - 28 / 1.1 |
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23 / 0.9 |
28 / 1.1 - 30 / 1.2 |
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25 / 1.0 |
33 / 1.3 - 38 / 1.5 |
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28 / 1.1 |
35 / 1.4 - 38 / 1.5 |
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30 / 1.2 |
38 / 1.5 - 41 / 1.6 |
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33 / 1.3 |
43 / 1.7 - 46 / 1.8 |
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38 / 1.5 |
51 / 2.0 - 56 / 2.2 |
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51 / 2.0 |
64 / 2.5 - 68 / 2.7 |
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64 / 2.5 |
75 / 3.0 - 90 / 3.5 |
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75 / 3.0 |
90 / 3.5 - 100 / 2.9 |
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100 / 3.9 |
127 / 5.0 |
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127 / 5.0 |
178 / 7.0 |
Chamfer Diameter (CD)
Chamfer Diameter (CD) is determined based on the target Mashed Ball Diameter (MBD). Normally, the MBD is
restricted by the bond pad-opening dimension. As a general guide, CD(max) = MBD/1.2.
Chamfer Angle (CA)
Chamfer Angle (CA) provides a certain amount of squash out in the formation of MBD. It also controls Free Air Ball (FAB) centering during impact. Typical chamfer angle is 90°. With a smaller CA, more volume of the FAB can be contained within the inner chamfer, hence a smaller deformed ball size.
Free Air Ball (FAB)
The combination and interaction of the hole size, chamfer diameter, chamfer angle, and inner chamfer determine the total amount of volume necessary to form the ball bond. The total volume of FAB must be greater than the volume created by the above combination so that enough gold material is squashed out of the chamfer area to form the desired MBD.
FABØ3 = 1.5H2(H-WD) + (CD3-H3)/4tan(0.5CA) + 1.5MBD2(MBH)