3D Wire Loop Bonding for Compact Semiconductor Packages
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Solution Overview
Problem
The existing methods for forming wire loops in semiconductor devices are limited by capillary size and the weakness of bonding wires, which restricts the proximity of bonding sites to the semiconductor die perimeter, leading to larger package sizes and potential electrical instability due to wire cracking.
Innovation Solution
A method of forming wire loops where the first and second kinks are on different planes, allowing a longer span portion and a gentler slope, enabling closer placement of bonding points to the semiconductor die perimeter without increasing the risk of wire cracking, by manipulating the capillary's motion to form a triangular prism shape with uniform cross-sectional area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If wire loop bonding sites are positioned nearer to the perimeters of the dice to reduce package size, then the package area is reduced, but the bonding wire is more severely bent causing increased risk of cracking and electrical instability
Solution Approach 1:
The wire loop is formed in three-dimensional space with kinks at different heights, creating a triangular prism shape rather than a planar configuration. This allows the wire to achieve the necessary span and clearance without excessive bending in a single plane, resolving the contradiction between compact packaging and wire reliability
Solution Approach 2:
The wire loop incorporates smooth curved kinks instead of sharp bends, distributing stress more evenly along the wire path. The first kink extends vertically and the second kink creates a gentle slope, reducing stress concentration and preventing wire cracking while maintaining compact dimensions
2Manufacturing precision
If capillary size is reduced to enable closer bonding sites to die perimeter, then bonding precision is improved, but the minimum achievable wire loop dimensions are constrained by capillary physical dimensions
Solution Approach 1:
By utilizing the third dimension (vertical height) for the wire loop configuration, the invention achieves long span lengths without requiring large horizontal distances. The wire extends vertically from the first bonding point and creates kinks at different heights, effectively increasing the wire loop's operational length while maintaining compact horizontal footprint suitable for precise bonding
3Area of stationary object
If wire loop bonding sites are positioned closer to die perimeter to minimize package footprint, then package size is reduced, but clearance between wire loop and die surface is reduced increasing short circuit risk
Solution Approach 1:
The first kink extends the wire vertically upward from the first bonding point, creating height clearance between the wire loop and the die surface. This vertical dimension provides the necessary insulation clearance while allowing the bonding sites to be positioned close to the die perimeter for minimal package footprint
Solution Approach 2:
The smooth curved configuration of the kinks ensures that the wire maintains adequate clearance from the die surface throughout its path. The vertical extension and gentle slopes prevent the wire from making contact with the die, eliminating short circuit risk while preserving compact packaging
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for a higher side view horizontal span length and vertical landing angle, enabling smaller semiconductor packages with increased clearance to prevent short circuits and improve electrical reliability.
Implementation Method 1
Typically an ultrasonic transducer is used to generate ultrasonic energy to attach a free air ball (FAB) from a capillary to a semiconductor die or a carrier
Data Source
AI summary
The invention provides a method of bonding wire between first and second bonding points with a bonding tool. It comprises the steps of forming a first bond at the first bonding point with the bonding tool, forming a first kink located over the first bond, and moving the bonding tool to a first position spaced from the first kink by a predetermined distance to release a length of wire from the bonding tool. It further comprises the step of moving the bonding tool in a direction away from the second bonding point to a second position which is outside a plane comprising the first bonding point, the second bonding point, and the first kink. It also comprises the steps of forming a second kink which lies outside the plane, and moving the bonding tool to the second bonding point to form a second bond.