Wire Bonding Tail Cutting Load Control
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Solution Overview
Problem
The wire bonding process faces challenges in achieving optimal bond strength between the inner lead and the wire, leading to issues such as weak or strong bonds, which can result in improper tail cutting, wire deformation, and subsequent short defects in semiconductor devices.
Innovation Solution
A wire bonding apparatus equipped with a capillary, clamper, load sensor, and control apparatus that measures and controls the breaking load during tail cutting to ensure it falls within an optimum range, preventing wire deformation and ensuring a suitable tail length for proper bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the bond strength of the inner lead and the wire is increased to ensure proper tail cutting, then the reliability of the connection is improved, but the wire may be severed at the top of the inner lead preventing tail formation and causing direct contact between the capillary and electrode
Solution Approach 1:
The patent employs a load sensor to detect the breaking load during tail cutting and provides feedback to the control apparatus. The control apparatus adjusts the bond strength parameters based on this feedback to maintain the breaking load within an optimal range, ensuring both reliable connection and proper tail formation without capillary-electrode contact.
Solution Approach 2:
The patent dynamically adjusts bonding parameters (such as ultrasonic power, bonding time, or pressure) based on the detected breaking load. By changing these parameters in response to measured values, the system maintains optimal bond strength that prevents both weak connections and excessive strength that would cause wire severance and tail formation failures.
2Strength
If a high breaking load is applied during tail cutting to ensure proper separation, then the connection strength is improved, but the wire undergoes spring back phenomenon and buckling deformation
Solution Approach 1:
The load sensor provides real-time feedback on the breaking load during tail cutting. The control apparatus uses this information to adjust the cutting parameters to keep the breaking load within an optimal range, preventing both insufficient separation and excessive load that would cause spring back and wire buckling.
Solution Approach 2:
The patent dynamically adjusts the tail cutting parameters based on the measured breaking load. By making the cutting process adaptive rather than fixed, the system can optimize the breaking load in real-time to achieve proper wire separation without causing deformation or spring back effects.
3Reliability
If the bond strength is optimized for tail cutting, then the tail cutting reliability is improved, but the deformed wire from spring back may contact adjacent wire connections causing short defects
Solution Approach 1:
The load sensor monitors the breaking load during tail cutting and provides feedback to the control apparatus. This feedback mechanism enables real-time adjustment of bonding parameters to maintain the breaking load within an optimal range, ensuring reliable tail cutting while preventing wire deformation that could lead to short defects.
Solution Approach 2:
The patent adjusts bonding and cutting parameters based on the measured breaking load to optimize the process. By dynamically changing parameters such as ultrasonic power, bonding time, or cutting force, the system achieves reliable tail cutting while minimizing wire deformation and preventing subsequent short defects.
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
The apparatus effectively suppresses wire deformation and prevents the use of deformed wires in bonding, thereby reducing yield defects and ensuring optimal bonding conditions by monitoring and adjusting the breaking load during tail cutting.
Implementation Method 1
a load sensor configured to measure load incurred on the wire
Implementation Method 2
a capillary moving portion to which the other ends of the transducer horn and the clamper supporting portion are fixed and which is configured to move the transducer horn and the clamper supporting portion as one
Data Source
AI summary
A wire bonding method involves bonding a wire in order at a first bonding point and a second bonding point; raising a capillary, through which the wire is inserted, on the second bonding point; cutting the wire by closing a clamper provided above the capillary at a time when the capillary has reached a prescribed height; and measuring a load incurred on the wire at a time of cutting of the wire.