Copper Wire Ball-Bonding with Inert Gas and Gold Buffer
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Solution Overview
Problem
Conventional semiconductor device manufacturing methods using gold wires face issues with oxidation during wire bonding, increased material costs, and connection failures due to the hardness and ductility of copper wires, leading to unstable cutting and potential short circuits.
Innovation Solution
The use of copper wires with through-holes in the island of the semiconductor device for inert gas flow to prevent oxidation, combined with gold ball formation on electrode pads to prevent short circuits, and individual lead fixation to ensure stable bonding and reduced material costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If copper wire is used instead of gold wire, then material cost is reduced and current handling capability is improved, but oxidation occurs during wire bonding
Solution Approach 1:
The patent applies inert atmosphere by introducing a nitrogen gas flow between the capillary and the workpiece during wire bonding. This nitrogen curtain creates an inert environment that prevents copper wire oxidation while allowing cost-effective copper wire to be used instead of gold wire, directly resolving the contradiction between material cost reduction and oxidation prevention
2Quantity of substance
If copper wire is used instead of gold wire, then material cost is reduced, but wire cutting stability deteriorates due to hardness and ductility
Solution Approach 1:
The patent applies preliminary action by forming a spherical ball at the tip of the copper wire before bonding. This pre-formed ball structure facilitates stable ultrasonic bonding and subsequent cutting by creating a consistent geometry that works well with the bonding process, thereby improving wire cutting stability while maintaining the cost benefits of copper wire
3Quantity of substance
If copper wire is used instead of gold wire, then material cost is reduced, but connection reliability worsens due to potential short circuits
Solution Approach 1:
The nitrogen gas flow creates an inert atmosphere that prevents copper wire oxidation, ensuring connection reliability by avoiding oxide layers that would cause poor electrical contact or short circuits, thus maintaining reliability while using cost-effective copper wire
4Power
If multiple wires are used to handle large currents, then current handling capability is improved, but device complexity increases
Solution Approach 1:
The patent changes the material parameter from gold to copper, which has superior electrical conductivity. This parameter change allows single copper wires to handle larger currents more efficiently, reducing the number of wires needed while maintaining or improving current handling capability, thereby reducing device complexity
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 approach reduces material costs, enhances adherence between the island and resin package, prevents oxidation, and ensures stable wire bonding with reduced connection failures and material usage, allowing for efficient handling of large currents with smaller wire counts.
Implementation Method 1
through-holes which are located above a gas exhaust hole provided in a placement stage of a wire bonding apparatus, and an inert gas supplied to the mounting portions is exhausted from the gas exhaust hole through the through-holes
Implementation Method 2
a metal ball formed at a tip end of a capillary is connected with an electrode pad by a technique of thermal compression bonding in combination with ultrasonic vibration
Implementation Method 3
a metal ball formed at a tip end of a capillary is connected with an electrode pad by a technique of thermal compression bonding in combination with ultrasonic vibration
Data Source
AI summary
A semiconductor element (10) is secured to an island (7), and a plurality of through-holes (8) are formed in the portion of the island (7), which surrounds the area to which the semiconductor element (10) is secured. Further, the electrode pads of the semiconductor element (10) and leads (4) are electrically connected by copper wires (11). In this structure, the cost of materials is reduced by using the copper wires (11) in comparison with gold wires. Further, a part of a resin package (2) is embedded in through-holes (8), so that the island (7) can be easily supported within the resin package (2).