Lead Frame Notch Design for Aluminum Wire Bonding
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Solution Overview
Problem
In resin sealing type semiconductor devices, the use of aluminum wires for wire-bonding poses challenges due to the need for intense ultrasonic waves to break oxide films, and the risk of lead frame deformation and incomplete cutting of the outer frame, which can lead to short circuits.
Innovation Solution
The implementation of a lead frame design with specific connection and notch configurations to effectively apply ultrasonic vibration forces and ensure complete cutting of the outer frame, using a lead frame with islands, wire-bonding portions, and notches to enhance bonding reliability and prevent short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aluminum wire is used for wire-bonding to reduce cost and resistance, then manufacturing cost and electrical resistance are improved, but the bonding process requires intense ultrasonic waves which can cause lead frame deformation and incomplete cutting of the outer frame
Solution Approach 1:
The outer frame is segmented by introducing notches that divide it into separable sections. These notches allow the cutting process to completely separate the outer frame from the lead frame, preventing short circuits while containing ultrasonic vibrations during aluminum wire bonding. The segmentation enables the outer frame to be cleanly divided without deformation.
Solution Approach 2:
The notches act as intermediary structures that mediate between the ultrasonic bonding process and the outer frame. They provide controlled points for vibration dissipation and serve as predetermined cutting locations, ensuring complete separation while preventing harmful vibrations during bonding.
2Strength
If intense ultrasonic waves are applied to break oxide films on aluminum wire and pad electrodes, then bonding strength is improved, but the lead frame may deform and the outer frame may not be completely cut
Solution Approach 1:
The notches extract or remove specific portions of the outer frame at predetermined locations, creating separation points that prevent the outer frame from interfering with the ultrasonic bonding process. This extraction allows intense ultrasonic waves to be applied without causing unwanted vibrations or deformation in the lead frame structure.
Solution Approach 2:
The notches convert the potentially harmful effect of intense ultrasonic vibrations into a beneficial outcome by providing controlled locations for vibration dissipation. The same ultrasonic energy that could cause deformation is instead directed and contained, ensuring complete cutting while maintaining bonding strength.
3Strength
If the outer frame is not completely cut after resin sealing, then structural support is maintained, but short circuits may occur between semiconductor dies
Solution Approach 1:
The notches segment the outer frame into separable sections, enabling complete cutting at predetermined locations. This segmentation ensures that the outer frame is fully separated from the lead frame, providing reliable electrical isolation between semiconductor dies while maintaining structural support during the bonding and sealing processes.
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 design achieves stable and reliable wire-bonding using aluminum wires and prevents short circuits by effectively containing ultrasonic vibration forces and ensuring complete removal of the outer frame, resulting in high-reliability resin sealing type semiconductor devices.
Implementation Method 1
the process is performed at room temperature and thus it is necessary to increase the intensity of ultrasonic waves. This is because it is necessary to break an aluminum oxide film formed on the surface of the pad electrode on the semiconductor die, various oxide films formed on the wire-bonding portion on the lead frame, etc.
Data Source
AI summary
The invention is directed to firm bonding between semiconductor dies etc bonded to a lead frame and wire-bonding portions of the lead frame by ultrasonic Al wire bonding, and the prevention of shortcircuit between the semiconductor dies etc due to a remaining portion of the outer frame of the lead frame after the outer frame is cut. By extending the wire-bonding portion etc on the lead frame in a wire-bonding direction and connecting the wire-bonding portion etc to the outer frame of the lead frame through a connection lead etc, the ultrasonic vibration force in the ultrasonic Al wire bonding is prevented from dispersing and the Al wire and the wire-bonding portion etc are firmly bonded. The outer frame is cut after a resin sealing process is completed. Even when a portion of the outer frame remains on the side surface of the resin package, connection between the connection lead etc and other hanging lead etc are prevented by providing a notch etc in the outer frame between the connection lead etc and the hanging lead etc.