Flip-Chip Bonding Laser Uniformity via Dynamic Scanning
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Solution Overview
Problem
Conventional flip-chip bonding techniques face challenges such as non-uniform energy distribution due to the Gaussian intensity profile of laser beams, leading to thermal deformation and reduced bonding strength, especially when dealing with semiconductor chips of varying sizes, and require precise movement of the bonding stage for efficient irradiation.
Innovation Solution
A flip-chip bonding method and apparatus that uses a lens assembly with scan mirrors and a linear velocity adjusting lens to uniformly irradiate the semiconductor chip with a laser beam, allowing the central laser beam position to move continuously across the chip's surface, adjusting the beam diameter and velocity to ensure even heating and eliminate the need for stage movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional laser beam with Gaussian intensity profile is used for heating, then the bonding process can be performed, but non-uniform energy distribution occurs leading to thermal deformation and reduced bonding strength
Solution Approach 1:
The patent makes the laser beam dynamic by continuously moving it across the semiconductor chip surface using scan mirrors, transforming the static Gaussian intensity profile into a dynamic scanning pattern that achieves uniform energy distribution over time and space
Solution Approach 2:
The patent introduces temporal and spatial dimensions to the laser heating process by scanning the beam across the chip surface, converting a one-point static heating method into a multi-point dynamic heating method that covers the entire bonding area
2Area of stationary object
If the bonding stage is moved to irradiate different areas of the chip, then the entire chip surface can be covered, but the device complexity and operation difficulty increase
Solution Approach 1:
Instead of moving the bonding stage to irradiate different areas, the patent inverts the approach by keeping the stage stationary and moving the laser beam itself across the chip surface using optical scan mirrors
Solution Approach 2:
The patent replaces the mechanical stage movement system with an optical scanning system using mirrors, eliminating complex mechanical motion mechanisms while achieving the same goal of covering the entire chip surface
3Area of stationary object
If the laser beam intensity is increased to cover peripheral areas, then the irradiation area is sufficient, but the central area receives excessive energy causing overheating
Solution Approach 1:
The patent uses periodic scanning action of the laser beam across the chip surface, systematically moving the beam from one location to another in a controlled sequence, ensuring each area receives appropriate energy exposure over time
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 achieves high productivity and reliable solder bonding by ensuring uniform energy distribution across the semiconductor chip, preventing distortion and enhancing bonding strength, while accommodating chips of different sizes without requiring stage movement.
Implementation Method 1
A laser beam 11 being emitted from a laser irradiation means 3 passes through a shutter 25, is reflected by a dichroic mirror 5, focused by a condenser lens 7 to irradiate and heat the lead terminal 9 and the semiconductor chip 1A such that the lead terminal 9 and the semiconductor chip 1A are bonded together
Implementation Method 2
A flip-chip bonding method and apparatus that uses a lens assembly with scan mirrors and a linear velocity adjusting lens to uniformly irradiate the semiconductor chip with a laser beam, allowing the central laser beam position to move continuously across the chip's surface
Data Source
AI summary
Provided are a laser flip-chip bonding method having high productivity and excellent bonding reliability and a flip-chip bonder employing the same. The flip-chip bonder includes: a bonding stage on which a substrate rests; a bonding head picking up a semiconductor chip and attaching the semiconductor chip to the substrate; and a semiconductor chip heating unit heating the semiconductor chip to a bonding temperature. The semiconductor chip heating unit includes: a laser light source; and a lens assembly refracting a laser beam emitted by the laser light source to a top surface of the semiconductor chip so that a central position of the laser beam varies across the top surface of the semiconductor chip.