Wire Bonding Method Reducing Loop Height via Capillary Treading
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Solution Overview
Problem
Conventional wire-bonding methods result in high wire loop heights due to the formation of a wire neck that rises from the pressure-bonded ball, making it difficult to reduce the overall thickness of semiconductor devices.
Innovation Solution
A modified wire-bonding method involving a capillary that moves upward and downward to tread on the ball neck, folding it back and pressing it against the pressure-bonded ball, followed by an oblique upward movement to form a kink, reducing the height of the wire loop by folding the wire back towards the second bonding point and bonding it at a lower height.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the capillary is moved upward to form a wire neck that rises from the pressure-bonded ball, then the wire can be properly bonded to the first bonding point, but the height of the wire loop increases, making it difficult to reduce the overall thickness of semiconductor devices
Solution Approach 1:
The capillary performs preliminary actions of moving upward and downward to tread on the ball neck before the final bonding operation. This preliminary treading compresses and shapes the ball neck, preparing it for the subsequent bonding step while controlling the wire loop height. The capillary moves upward to a first height to tread on the ball neck, then moves downward to a second height, repeating this sequence multiple times before the final bonding operation.
Solution Approach 2:
The capillary employs dynamic movement patterns with varying heights and speeds during the bonding process. It moves upward to a first height, downward to a second height, and repeats this dynamic sequence multiple times. The capillary also performs an oblique upward movement at a third height that is higher than the first height but lower than the second height, creating a kink in the wire. These dynamic movements allow precise control of the wire loop height while ensuring reliable bonding.
2Ease of manufacture
If the capillary moves horizontally in the direction of the second bonding point with respect to the capillary, then the wire can be connected to the second bonding point, but the neck portion is often damaged due to friction between the capillary and the thin metal wire
Solution Approach 1:
The capillary performs preliminary treading movements upward and downward multiple times before the final horizontal movement to connect the wire to the second bonding point. This preliminary action strengthens and stabilizes the wire neck, preventing damage during the subsequent horizontal movement. The repeated upward and downward movements prepare the wire neck for the final connection operation.
Solution Approach 2:
The bonding process employs continuous useful actions where the capillary moves upward and downward in a continuous sequence multiple times to tread on the ball neck, then performs the final horizontal movement without interruption. This continuous action ensures the wire neck is properly prepared and connected in one seamless operation, maintaining wire neck strength throughout the process.
3Reliability
If the wire is folded up onto the pressure-bonded ball and pressed to form a head portion, then the wire can be secured, but the head portion cannot be made particularly low, failing to satisfy the demand for decreasing the height of the wire loop
Solution Approach 1:
The capillary performs preliminary treading movements upward and downward multiple times before the final bonding operation. This preliminary action compresses and shapes the wire, creating a compact head portion that is both secure and low-profile. The repeated upward and downward movements prepare the wire for a compact final configuration.
Solution Approach 2:
The capillary employs dynamic movement with varying heights, moving upward to a first height, downward to a second height, and repeating this sequence. The capillary also performs an oblique upward movement at a third height to create a kink, then moves upward to a fourth height for the final bonding. These dynamic movements enable precise control of the head portion height while ensuring reliable wire securing.
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 effectively reduces the height of the wire loop, allowing for a lower overall thickness of semiconductor devices by folding the wire back and bonding it at a lower height, preventing the wire from projecting upward and maintaining a low profile.
Implementation Method 1
the neck portion is often damaged due to a friction between the capillary and the thin metal wire that is produced while moving
Implementation Method 2
an initial ball is first formed at a tip end of the wire, and the initial ball is pressure-bonded to the pad of the semiconductor chip using the capillary
Data Source
AI summary
After forming a pressure-bonded ball and a ball neck by bonding an initial ball to a pad, a capillary is moved upward, away from a lead, and then downward, thereby the ball neck is trodden on by a face portion that is on the lead side of the capillary. Subsequently, the capillary is moved upward and then toward the lead until the face portion of the capillary is positioned above the ball neck, thereby a wire is folded back toward the lead. Then, the capillary is moved downward such that a side of the wire is pressed by the capillary against the ball neck that has been trodden on. After the capillary is moved obliquely upward toward the lead and then looped toward the lead, the wire is pressure-bonded to the lead.