Mobile electronic products continually require finer geometries for packaged integrated circuits. Wireless phones, PDA and digital cameras continue to merge into a common device that will benefit from 
finer pitch and lower profile wire bonding or ball bumping for flip chip, stacked chip and other advanced packaging technologies. Inherent variations in materials, tools and process can cause variations in ball shape and size, stitch shape, bond quality, and thus, yield.
Shrinking electronic package geometries are driving continuous improvements in interconnect technologies. Wire bonding is a mature technology that continues to meet challenges of finer geometric capability: loop shape, bond pitch, ball size, and stitch size control.
The packaging industry is looking for a common set of improvements as geometries continue to shrink:
- Uniformity of ball bump height and/or bump diameter
- Reduced bond pitch for wires
- Reduced bond pitch for bumps
- Better bump coplanarity
- Uniformity of stitch impressions
- Minimize adverse impacts to sensitive materials for stitch
- Process
- Reduced process development time
- Reduced sensitivity to material, environment, and setup variation
- Real-time capture/qualification of production data
- Data trending analysis of production data
Adaptive Bond DeformationTM
Adaptive Bond DeformationTM is a method recently developed to control the geometry of both ball and stitch according to process parameter inputs supplied by the user.
This technique adapts to normal variations in bond surface, bond tool coupling, part fixture, and other difficult-to-measure influences to produce bonded ball bumps and stitches with significant improvement in geometry consistency with similar or better results for ball shear and pull strength when compared to non-adaptive bonding.
Ball Geometry and Shear Definitions
|
Measure |
Definition |
|
FABD |
Free air ball is the diameter of the ball created from the electronic flame off process while the ball is in free air and before it contacts the bond surface. |
|
MBD |
Mashed ball diameter is the diameter of the ball after ultrasonic bonding is complete. (Largest diameter in plan view) |
|
BBD |
Bonded ball diameter is the diameter of bond contact between ball and substrate. |
|
TH |
Top height is the height of ball measured from substrate surface to top of the ball. |
|
SF |
Shear force of the ball in grams |
|
SS |
Shear strength of the ball is calculated as the SF/BBD area in grams/mil2. |
Learn more. Download "Geometry & Bond Improvements for Wire Ball Bonding & Ball Bumping."
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Daniel Evans
Senior Scientist / Applications Manager
Palomar Technologies