Flip-Chip Bonding Tool Layout for Uniform Laser Heating
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Solution Overview
Problem
In flip chip bonding processes, existing technologies face challenges in maintaining uniform temperature distribution across semiconductor chips during laser bonding, leading to potential defects due to thermal stress and warpage, especially when using conventional convection reflow methods or bonding tools with direct contact surfaces that hinder heat transfer uniformity.
Innovation Solution
A bonding tool with a configuration that minimizes contact area through the use of contact protrusions on its surface, allowing for controlled heat transfer, featuring a vacuum adsorption system and a non-contact thermometer for temperature monitoring, ensuring uniform temperature distribution across the semiconductor chip by varying the cross-sectional areas and spacing of contact protrusions from the center to the outer parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bonding tool with a large contact area is used to press the semiconductor chip, then the chip is well-supported and positioned, but heat transfer from the chip to the bonding tool increases causing non-uniform temperature distribution
Solution Approach 1:
The bonding tool divides the contact surface into multiple discrete contact protrusions rather than using a continuous large contact area. This segmentation allows the chip to be supported at multiple points while reducing the total contact area, thereby minimizing heat transfer to the bonding tool and maintaining uniform temperature distribution across the chip during laser bonding.
Solution Approach 2:
The bonding tool implements different contact characteristics at different locations by varying the cross-sectional areas and spacing of contact protrusions from the center to outer parts of the tool. This local differentiation optimizes both chip support stability and heat transfer control, ensuring reliable positioning while maintaining temperature uniformity.
2Temperature
If the contact area between bonding tool and semiconductor chip is reduced, then heat transfer is minimized and temperature uniformity is improved, but chip support and positioning stability deteriorate
Solution Approach 1:
By segmenting the contact surface into multiple protrusions, the tool achieves both reduced total contact area (for temperature uniformity) and distributed support points (for positioning stability). The segmentation allows optimization of heat transfer characteristics while maintaining mechanical support reliability.
Solution Approach 2:
The contact protrusions are designed with asymmetric distribution patterns, with different cross-sectional areas and spacing from center to outer parts. This asymmetric design provides enhanced support where needed while controlling heat transfer, resolving the contradiction between stability and temperature uniformity.
3Reliability
If conventional convection reflow method is used to heat the substrate and semiconductor chip, then bonding is achieved, but thermal stress and warpage occur due to simultaneous heating of both components
Solution Approach 1:
The invention extracts the heating function from the bonding tool itself and separates it into an independent laser heating system. The bonding tool serves only for pressing and positioning, while the laser provides localized heating to the semiconductor chip. This separation eliminates the thermal stress and warpage problems caused by simultaneous heating of both substrate and chip in conventional convection reflow methods.
Solution Approach 2:
The laser beam acts as an intermediary heating source between the energy source and the semiconductor chip. It delivers energy selectively to the chip without directly heating the substrate or the bonding tool, enabling precise thermal control and avoiding the thermal expansion mismatch issues that cause warpage and thermal stress.
4Device complexity
If laser beam is radiated without pressing the semiconductor chip, then equipment complexity is reduced, but bonding quality deteriorates due to bends and warpage of substrate and chip
Solution Approach 1:
The invention merges the pressing function and laser transmission function into a single bonding tool structure. The tool simultaneously provides mechanical support to prevent warpage and allows laser beam transmission for heating, achieving both bonding quality and equipment simplicity through functional integration.
Solution Approach 2:
The bonding tool is designed with multi-functionality, serving both as a mechanical press for positioning and support, and as a transmission medium for the laser beam. This universal design eliminates the need for separate pressing and heating systems, maintaining equipment simplicity while ensuring high bonding quality through proper chip support.
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 configuration enables efficient and uniform heat distribution, reducing temperature variations between the center and outer parts of the semiconductor chip, thereby enhancing bonding quality and reducing the need for high laser output, while maintaining precise control over the bonding process.
Implementation Method 1
The temperature of the semiconductor chip is rapidly increased simultaneously with absorbing energy oscillating from the laser beam
Implementation Method 2
absorbing energy oscillating from the laser beam
Implementation Method 3
fixing the semiconductor chip through vacuum adsorption
Data Source
AI summary
Disclosed is a bonding tool for simultaneously heating a semiconductor chip using a laser and bonding the semiconductor chip in a flip chip laser bonding process, in which a vacuum wall configured to maintain a vacuum at a time of adsorbing the semiconductor chip is formed at the outer parts of the bottom surface of the bonding tool, and a plurality of contact protrusions is formed lengthwise and breadthwise on the bottom surface of the bonding tool in a pattern configured such that a heat transfer area of the semiconductor chip to the bonding tool at the center of the semiconductor chip is relatively large and the heat transfer area is gradually reduced in the direction towards the outer parts of the semiconductor chip so as to achieve a uniform temperature distribution from the center to the outer parts of the semiconductor chip.