Spot Heat Wirebonding with Electromagnetic Reflector
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Solution Overview
Problem
Existing wirebonding techniques face challenges in achieving secure bonds due to inadequate pressure and ultrasonic energy application, excessive heat, and inefficient heat distribution, particularly in complex configurations like overhangs or stacked die assemblies, which can result in poor bonding or damage to circuitry.
Innovation Solution
A method and system that utilize electromagnetic heating of the bondwire and bonding tool, combined with a heat reflector to precisely direct heat to the bonding site, reducing the need for excessive ultrasonic energy and pressure, and incorporating a concave mirror to reflect heat back onto the bonding area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional wirebonding is performed without preheating, then the bonding process is simple, but insufficient heat leads to poor bonding quality
Solution Approach 1:
A heat reflector is introduced as an intermediary component between the heat source and bonding site to efficiently direct thermal energy. The reflector concentrates heat onto the bonding area without requiring complex heating systems, thereby improving bonding quality while maintaining system simplicity
Solution Approach 2:
Heat is applied locally to the bonding site rather than heating the entire device. The heat reflector focuses thermal energy precisely where needed (at the bonding interface between ball and pad), ensuring reliable bonding without unnecessarily heating surrounding circuitry
2Reliability
If excessive heat is applied to the bonding site, then bonding quality improves, but surrounding circuitry is damaged
Solution Approach 1:
The heat reflector concentrates thermal energy into a focused beam that targets only the bonding interface. This localized heating approach delivers sufficient heat for quality bonding while minimizing thermal exposure to surrounding sensitive circuitry, thereby preventing heat-related damage
Solution Approach 2:
The heating process is segmented into a controlled, directed path from heat source through the reflector to the bonding site. This segmentation allows precise control over where heat is applied, separating the bonding zone from surrounding areas to prevent collateral thermal damage
3Object-affected harmful factors
If insufficient pressure is applied during bonding, then circuitry damage is reduced, but bonding quality deteriorates
Solution Approach 1:
The bonding process parameters (heat, pressure, ultrasonic energy) are optimized and balanced. Preheating the bondwire to its melting point allows bonding to proceed with reduced pressure requirements, maintaining bonding quality while minimizing mechanical stress on the circuitry
4Reliability
If excessive ultrasonic energy is applied, then bonding quality improves, but bond stress increases
Solution Approach 1:
The ultrasonic energy parameter is reduced due to preheating of the bondwire. By heating the bondwire to its melting point before bonding, the material becomes softer and more formable, allowing adequate bonding with lower ultrasonic energy levels that reduce stress on the nascent bond
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 enables secure wirebonding with reduced ultrasonic energy and pressure, precise heat application, and minimized heat transfer to sensitive areas, enhancing bond quality and reducing the risk of damage to semiconductor devices.
Implementation Method 1
heating the bondwire, ball, and bonding tool with an electromagnetic radiation source
Implementation Method 2
incorporating a concave mirror to reflect heat back onto the bonding area
Implementation Method 3
The ultrasonic energy applied by the bonding tool abrades the ball of the bondwire against the surface of the bond pad
Implementation Method 4
A controlled amount of pressure is then applied by the capillary for a selected amount of time, contributing to the formation of a metallurgical weld between the bondwire and the bond pad as well as deforming the ball into its final shape
Data Source
AI summary
Methods and systems are disclosed for forming secure wirebonds between electrical contacts in electronic device assemblies. Representative embodiments of the invention are described for forming a wirebond including system components and method steps for generating electromagnetic energy from a heat source and transmitting heat to a ball formed on a bondwire. Subsequently, pressure applied to the ball at the bonding site is used in the formation of a wirebond.