Closed Loop Wire Bonding Force Calibration
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Solution Overview
Problem
Conventional wire bonding systems face issues with inconsistent bonding energy application, leading to undesirable bonds, over-squashed bonds, and short wire tails due to the lack of precise control over bonding energy and force, especially when the contact is not properly 'pinned down' against the device supporting surface.
Innovation Solution
Implementing a 'closed loop' approach in wire bonding by detecting when a contact is pressed against the device supporting surface using techniques such as impedance detection, force threshold measurement, and bonding tool position verification, allowing for precise application of bonding energy and force only after the contact is securely positioned.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bonding energy is applied after contact is established between wire/bonding tool and contact, then bonding process can proceed, but undesirable bonds and over-squashed bonds occur when contact is not pinned down
Solution Approach 1:
The system performs preliminary detection to determine whether the contact is properly pinned down against the device supporting surface before applying bonding energy. This preliminary check ensures that the contact is in the correct position and stable, preventing undesirable bonds and over-squashed bonds that would occur if bonding energy were applied without verification of proper contact positioning.
2Productivity
If bonding energy is applied without detecting contact position, then bonding process is simpler and faster, but vibration and resonance problems result in over-squashed bonds and short wire tail lengths
Solution Approach 1:
The system implements a feedback mechanism where the state of the contact (whether it is pinned down or not) is detected and used to control the application of bonding energy. The detection system provides real-time information about contact positioning, and this feedback determines whether bonding energy should be applied, thereby preventing vibration and resonance problems that lead to non-uniform bonds while maintaining efficient bonding processes.
3Speed
If contact is not pinned down before bonding, then bonding tool can reach contact faster, but vibration and resonance problems occur leading to defective bonds
Solution Approach 1:
The system performs a preliminary detection action to verify that the contact is pinned down before proceeding with bonding energy application. This preliminary check ensures that even though the bonding tool reaches the contact quickly, the bonding only occurs when proper contact positioning is confirmed, thereby preventing vibration and resonance problems that would compromise bond reliability.
Solution Approach 2:
The system uses feedback from the detection system to control the bonding process. The detection system monitors whether the contact is properly pinned down, and this information feeds back to control whether bonding energy is applied. This feedback mechanism ensures that high-speed bonding does not compromise reliability by preventing bonding until proper contact positioning is confirmed.
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 method improves bond uniformity, quality, and yield rate by ensuring that bonding energy is applied only when the contact is correctly aligned, reducing resonance problems and enhancing the reliability of wire bonds.
Implementation Method 1
varying types of bonding energy may be used including, for example, ultrasonic energy, thermosonic energy, thermocompressive energy
Implementation Method 2
varying types of bonding energy may be used including, for example, ultrasonic energy, thermosonic energy, thermocompressive energy
Implementation Method 3
varying types of bonding energy may be used including, for example, ultrasonic energy, thermosonic energy, thermocompressive energy
Implementation Method 4
detecting when a portion of the contact is pressed against a device supporting surface (e.g., the heat block) of the wire bonding machine
Implementation Method 5
detecting when a portion of the contact is pressed against a device supporting surface
Data Source
AI summary
A method of applying bonding energy to form a bond between a portion of a wire and a contact of a bonding location using a wire bonding machine is provided. The method includes: (1) moving a bonding tool towards the contact; (2) detecting when a portion of the contact (100a) is pressed against a device supporting surface (112) of the wire bonding machine; and (3) applying bonding energy to the portion of the contact such that a bond is formed between the contact and the portion of wire.