Laser Control Structure for Selective Bonding Without Warpage
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Solution Overview
Problem
Conventional thermocompression laser bonding processes face challenges such as warpage and damage due to thermal expansion differences between substrates and semiconductor elements, especially when using high-temperature soldering, which reduces reliability and limits the ability to perform selective bonding.
Innovation Solution
A laser bonding method that utilizes a laser control structure with alternating thin film laminates on a substrate to control laser light absorption and reflectance, allowing for precise heating of bonding regions to prevent thermal deformation and enable high-temperature soldering at low laser power, thereby simplifying the bonding process for components with different melting points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high-temperature soldering is applied to bond semiconductor elements with substrates, then bonding strength is improved, but thermal damage and warpage occur due to difference in coefficient of thermal expansion
Solution Approach 1:
The patent applies different thin film laminate structures to different regions (first region and second region) of the substrate. The first thin film laminate has different reflectance or absorptivity characteristics compared to the second thin film laminate, allowing localized control of laser energy absorption and heating during bonding processes.
Solution Approach 2:
The patent uses composite thin film laminate structures consisting of multiple layers with different material properties. These composite structures are designed to control laser light interaction, enabling precise thermal management during bonding while protecting against thermal expansion differences between substrate and semiconductor elements.
2Ease of manufacture
If the same laser power is applied to all regions, then processing simplicity is maintained, but thermal deformation occurs in regions where bonding is not required
Solution Approach 1:
The patent implements region-specific thin film laminate configurations where the first thin film laminate and second thin film laminate have different optical properties. This allows the same laser power to be applied uniformly while achieving localized heating control - bonding regions absorb more energy while non-bonding regions reflect more energy, preventing unwanted thermal deformation.
3Productivity
If conventional thermocompression laser bonding is used, then bonding process is achieved, but selective bonding capability is reduced due to heating and pressurization of entire substrate
Solution Approach 1:
The patent enables selective bonding by creating spatial variations in laser energy absorption through different thin film laminate structures. The first region with its specific thin film laminate configuration absorbs laser energy for bonding, while the second region with different laminate configuration remains cooler, allowing precise selective bonding without heating the entire substrate.
Solution Approach 2:
The patent divides the substrate into distinct functional regions (first region and second region) with different thin film laminate structures. This segmentation allows independent thermal control of different areas during laser bonding, enabling selective bonding operations on specific regions while leaving other regions unaffected.
4Reliability
If low-temperature soldering is used to prevent damage to flexible substrates, then substrate reliability is improved, but bonding strength decreases
Solution Approach 1:
The patent changes the optical parameters of different substrate regions through varying thin film laminate structures. By controlling reflectance and absorptivity characteristics of the first and second thin film laminates, the system can concentrate laser energy in bonding regions to achieve high bonding strength while maintaining lower overall substrate temperature to preserve flexible substrate reliability.
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 prevents thermal damage and warpage, allows for selective bonding of components with different melting points in a single process, and enhances the reliability of the bonding process by controlling light-to-heat conversion efficiency and thermal energy delivery.
Implementation Method 1
light-to-heat conversion efficiency of a laser light source is solely dependent on a substrate and a bonding object upon a laser bonding process
Implementation Method 2
reflectance or absorptivity of the first thin film laminate with respect to laser is different from reflectance or absorptivity of the second thin film laminate
Implementation Method 3
irradiating a laser toward the bonding object and the bonding portions; using the controlled quantity of laser light to heat the bonding portions and the bonding object to a bonding temperature
Implementation Method 4
a bonding process technology that overcomes those shortcomings is a laser assisted bonding (LAB) process
Data Source
AI summary
Provided are a laser control structure and a laser bonding method using the same, and more particularly, a laser bonding method including: forming bonding portions on a substrate; providing a bonding object onto the bonding portions; providing a laser control structure onto the bonding object or the substrate; irradiating a laser toward the bonding object and the bonding portions; controlling quantity of laser light absorbed through the laser control structure; using the controlled quantity of laser light to heat the bonding portions and the bonding object to a bonding temperature; and bonding the bonding portions and the bonding object, wherein the laser control structure includes: a first substrate including a first region and a second region; a first thin film laminate on the first region; and a second thin film laminate on the second region, wherein: the first thin film laminate includes at least one first thin film layer and at least one second thin film layer, which are laminated on the first region; the second thin film laminate includes at least one third thin film layer and at least one fourth thin film layer, which are laminated on the second region; reflectance or absorptivity of the first thin film laminate with respect to laser is different from reflectance or absorptivity of the second thin film laminate; and the bonding temperature varies according to the quantity of laser light.