Capillary Stitch Bonding Without Tool Marks on Bond Pads
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Solution Overview
Problem
Existing wire bonding techniques often result in tool marks on semiconductor devices, which can lead to oxidation, contamination, and reduced bond strength.
Innovation Solution
A method and system for wire bonding that involves forming a ball bond at a first location and a stitch bond at a second location without contacting the capillary tip with the second location, thereby preventing tool marks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the capillary tip contacts the second location during stitch bonding, then the bonding process is simpler, but tool marks are created on the semiconductor device
Solution Approach 1:
The patent introduces an intermediary fluid (gas or liquid) between the capillary tip and the workpiece surface. This fluid layer allows the capillary tip to approach close to the surface without direct contact, thereby preventing tool marks while maintaining process simplicity. The fluid acts as a mediator that transfers the bonding force without transmitting mechanical contact damage to the surface.
Solution Approach 2:
The patent replaces direct mechanical contact with a fluid-mediated bonding mechanism. Instead of relying on solid-to-solid contact between the capillary tip and the workpiece, the system uses ultrasonic vibrations transmitted through the fluid to achieve bonding, eliminating the mechanical damage that causes tool marks.
2Strength
If the capillary tip contacts the second location during stitch bonding, then bonding force is directly applied, but oxidation and contamination occur
Solution Approach 1:
The patent employs an inert gas (such as nitrogen or argon) as the bonding medium to create a protective atmosphere during the bonding process. This inert environment prevents oxidation and contamination of the workpiece surface and wire bond by excluding reactive gases, while still allowing effective bonding through ultrasonic vibration transmission.
Solution Approach 2:
The inert gas acts as an intermediary medium that enables bonding force transmission while simultaneously providing a protective barrier against oxidation and contamination. The gas layer allows ultrasonic energy to pass through for bonding while preventing direct exposure of the workpiece to harmful atmospheric conditions.
3Productivity
If the capillary tip contacts the second location during stitch bonding, then the bonding process is faster, but bond strength is reduced
Solution Approach 1:
The patent utilizes periodic ultrasonic vibrations as the bonding mechanism. These high-frequency oscillations create intermittent contact and separation between the bonding interface, generating localized heat and pressure that facilitate strong bonding without requiring sustained mechanical contact. This periodic action maintains both high bonding speed and strong bond strength.
Solution Approach 2:
The patent replaces continuous mechanical pressure with pulsed ultrasonic vibration for bonding. The ultrasonic energy provides the necessary bonding force through cyclic deformation and heat generation at the bonding interface, achieving both rapid bonding and strong bond strength without the need for prolonged mechanical contact that would reduce productivity.
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
The solution effectively prevents tool marks on semiconductor devices, enhancing bond strength and reliability, as demonstrated by increased wire material remaining after a pull test.
Implementation Method 1
Wire bonding is an electrical interconnection technique that uses thin wire and a combination of heat, pressure and/or ultrasonic energy. Wire bonding is a solid phase welding process
Implementation Method 2
Wire bonding is an electrical interconnection technique that uses thin wire and a combination of heat, pressure and/or ultrasonic energy
Implementation Method 3
Wire bonding is an electrical interconnection technique that uses thin wire and a combination of heat, pressure and/or ultrasonic energy
Implementation Method 4
attaching a second end of the wire to the second location while preventing contact between the capillary tip and the second location, thereby forming a stitch bond without a tool mark at the second location
Data Source
AI summary
Apparatus and method for tool mark free stich bonding. In some embodiments, a method for wire bonding can include feeding a wire through a capillary tip and attaching a first end of the wire to a first location, thereby forming a ball bond. The method can further include moving the capillary tip towards a second location while the wire feeds out of the capillary tip. The method can further include attaching a second end of the wire to the second location while preventing contact between the capillary tip and the second location, thereby forming a stitch bond without a tool mark at the second location.