Reel-to-Reel Laser Reflow for Substrate Thermal Deformation
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Solution Overview
Problem
Conventional reflow processes, such as those using infrared heaters or ceramic heaters, are inefficient and can cause thermal deformation and air gaps, leading to defects in bonding semiconductor elements to thin substrates, and existing laser-based methods fail to adjust the laser beam emission area effectively.
Innovation Solution
A reel-to-reel laser reflow method and device that unwinds a substrate, forms a solder portion, seats emission and non-emission target elements, and uses an optical unit to adjust and emit a uniformized laser beam specifically to the emission target element, preventing air gaps and thermal deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If mass reflow process using infrared heater or ceramic heater is used, then heating coverage is comprehensive, but operation time is long (at least minutes) and thermal deformation occurs
Solution Approach 1:
The patent replaces the conventional infrared heater or ceramic heater (thermal radiation system) with a laser beam system. The laser beam directly irradiates the solder material, enabling rapid heating and melting without the need for prolonged thermal radiation exposure. This substitution reduces operation time from minutes to seconds while maintaining effective heating coverage through focused energy delivery.
Solution Approach 2:
The patent employs a movable stage that selectively positions the substrate under the laser beam only when the laser head is at a specific location. This allows localized heating of the solder material at precise positions rather than comprehensive heating of the entire substrate, thereby reducing overall operation time and preventing thermal deformation in non-bonding areas.
2Reliability
If mass reflow process is used, then bonding can be achieved, but air gaps form between substrate and conveyor belt causing heat trapping and thermal deformation
Solution Approach 1:
The patent replaces the conveyor belt system with a movable stage mechanism. The movable stage supports the substrate from below and can be precisely positioned to bring the substrate into contact with the laser head. This eliminates the air gap problem between substrate and conveyor belt, preventing heat trapping and thermal deformation while maintaining bonding capability through controlled laser irradiation.
Solution Approach 2:
The movable stage acts as an intermediary between the substrate and the laser head. It precisely controls the relative positioning and contact between these components, ensuring that the substrate is properly supported and positioned during laser irradiation without creating air gaps that would trap heat and cause deformation.
3Device complexity
If fixed laser beam emission area is used, then device structure is simple, but emission area cannot be adjusted to match different element shapes and positions
Solution Approach 1:
The patent introduces a movable stage that can dynamically adjust the position of the substrate relative to the laser head. This dynamic positioning capability allows the laser beam to be precisely directed at different locations on the substrate, enabling adaptation to different element shapes and positions without requiring a complex adjustable emission area system. The simplicity of the optical system is maintained while achieving versatility through motion control.
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 method allows for precise adjustment of the laser beam emission area and reduces operation time, preventing substrate damage and enhancing bonding efficiency by eliminating air gaps and thermal deformation, thus improving the bonding process.
Implementation Method 1
emitting a laser square beam to the solder portion, on which the emission target element is seated, such that the emission target element is attached to the substrate
Data Source
AI summary
The present invention relates to a reel-to-reel layer reflow method, which emits a uniformized laser beam, which can easily adjust the emission area, and which is for the purpose of improving productivity. An embodiment of the present invention provides a reel-to-reel layer reflow method comprising the steps of: a) transferring a substrate, which has been wound in a roll type, to one side while unwinding the same; b) forming a solder portion on the substrate; c) seating an emission target element on the solder portion and seating a non-emission target element on the substrate; d) surface-emitting a laser beam to the solder portion, on which the emission target element is seated, such that the emission target element is attached to the substrate; e) inspecting the substrate structure manufactured through said step d); and f) winding the substrate structure in a roll type.