Overhang Die Wire Bonding Z-Axis Force Profile Optimization
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Solution Overview
Problem
In semiconductor packaging, wire bonding of overhang dies is challenging due to die deflection, which can cause damage during the bonding process, as the dies bend and may crack or collide with other structures, leading to inefficiencies and potential damage to the die and wire loops.
Innovation Solution
A method is developed to determine and apply a z-axis force profile, maximum bond force, and z-axis constant velocity profile for each bonding location on overhang dies, using iterative processes and z-axis encoder feedback to optimize damping gain, die settle time, and bond force, thereby minimizing die deflection and oscillation during wire bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wire bonding is performed on overhang die, then electrical interconnection is achieved, but die deflection occurs causing damage or contact with structures below
Solution Approach 1:
The system performs preliminary characterization of the overhang die by measuring z-axis deflection at multiple bonding locations before actual wire bonding. This preliminary action establishes a deflection model that predicts die behavior under bonding forces, allowing optimization of bonding parameters to prevent damage while achieving reliable interconnection
Solution Approach 2:
The system uses z-axis encoder feedback to measure actual die deflection during bonding operations and compares it against predicted values. This feedback loop allows real-time adjustment of bonding parameters and validation of the deflection model, ensuring reliable bonding while preventing die damage
2Strength
If bond force is increased to ensure reliable bonding, then bonding strength improves, but die deflection increases causing damage or oscillation
Solution Approach 1:
The system determines optimal bonding parameters (bond force, damping gain, settle time) by characterizing die deflection response at multiple z-axis positions. This allows customization of bonding parameters for each specific overhang die configuration, achieving sufficient bond strength while maintaining die stability through optimized force application
Solution Approach 2:
The system dynamically adjusts bonding parameters based on real-time die deflection measurements and predictions. By monitoring z-axis position during bonding and adjusting forces accordingly, the system maintains die stability while achieving reliable bond formation, preventing oscillation and damage
3Reliability
If die deflection is reduced through parameter optimization, then die damage is prevented, but processing time increases
Solution Approach 1:
The system performs die characterization and model generation as a preliminary one-time action before production bonding. This preliminary characterization captures die deflection characteristics that can then be reused for multiple bonding operations, minimizing per-unit processing time while ensuring die integrity through optimized parameters
Solution Approach 2:
The system creates a digital model (copy) of the die's mechanical response characteristics through preliminary characterization. This model can then be used to predict and optimize bonding parameters without requiring repeated physical measurements, significantly reducing processing time while maintaining die integrity through accurate parameter prediction
Data Source
AI summary
A method of providing a z-axis force profile applied to a plurality of bonding locations during a wire bonding operation is provided. The method includes: (a) determining a z-axis force profile for each of a plurality of bonding locations on an unsupported portion of at least one reference semiconductor device; and (b) applying the z-axis force profile during subsequent bonding of a subject semiconductor device. Methods of: determining a maximum bond force applied to a bonding location during formation of a wire bond; and determining a z-axis constant velocity profile for formation of a wire bond, are also provided.