Flip-Chip Laser Bonding for Warpage-Free Thin Chip Assembly
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Solution Overview
Problem
Existing flip-chip bonding methods, such as reflow and thermal compression, face challenges with temperature-induced bending and warping of thin semiconductor chips, leading to defects and low productivity due to prolonged high-temperature exposure and slow heating processes.
Innovation Solution
A flip-chip laser bonding apparatus and method that uses laser light to rapidly bond semiconductor chips to a substrate, employing a substrate support member, chip support member, chip transfer unit, and laser head to align and bond the chips with minimal temperature increase, preventing defects and improving productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high-temperature reflow processing is used to bond semiconductor chips to substrate, then bonding strength is improved, but semiconductor chips bend or warp due to prolonged high-temperature exposure
Solution Approach 1:
The patent replaces the conventional thermal conduction heating method with laser beam heating. The laser head irradiates the substrate with laser beams to locally melt solder bumps, achieving bonding without prolonged high-temperature exposure that causes chip warping. This substitutes thermal field with optical field for more precise and rapid heating.
Solution Approach 2:
The patent employs periodic pulsed laser irradiation instead of continuous heating. The laser operates in pulses to melt solder bumps rapidly and then allows rapid cooling, preventing thermal accumulation that would cause chip deformation. This periodic action enables precise thermal control at the solder bump level.
2Reliability
If thermal compression bonding method is used with heating block, then bonding is achieved, but heating time is prolonged and productivity is reduced
Solution Approach 1:
The patent replaces the mechanical thermal conduction system (heating block) with an optical system (laser head). The laser beams directly irradiate the substrate and solder bumps, transferring energy much faster than thermal conduction through a heating block, thereby dramatically reducing bonding time and increasing productivity.
Solution Approach 2:
The patent applies laser heating locally to specific solder bump positions rather than heating the entire substrate and chip uniformly. This localized heating melts only the necessary solder bumps for bonding, reducing overall heating time and energy consumption while maintaining bonding quality.
3Reliability
If conventional heating methods are used, then solder bumps are melted for bonding, but temperature of semiconductor chip is unnecessarily increased causing damage
Solution Approach 1:
The patent substitutes thermal conduction heating with direct laser irradiation. The laser head targets the substrate and solder bumps directly, heating only these areas to the melting point. The chip itself experiences minimal temperature increase because the laser energy is focused on the bonding interface, not the chip body, preventing thermal damage.
Solution Approach 2:
The substrate acts as an intermediary that absorbs laser energy and transfers it locally to the solder bumps. The laser irradiates the substrate, which then conducts heat to the solder bumps at the bonding interface, preventing direct overheating of the semiconductor chip while still achieving sufficient solder melt for bonding.
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 enables high-quality, rapid bonding of flip-chip semiconductor chips with reduced risk of contact defects and thermal damage, maintaining chip quality by using laser light to instantaneously melt solder bumps and controlling the bonding process to prevent warpage and increase operational speed.
Implementation Method 1
a laser head configured to bond the semiconductor chip to the substrate by irradiating the lower surface of the substrate supported on the substrate support member with laser light
Implementation Method 2
a substrate support member configured to adsorb, hold, and support a lower surface of a substrate
Data Source
AI summary
A flip-chip laser bonding apparatus and method are provided in which flip-chip type semiconductor chips are bonded to a substrate using laser light. The flip-chip laser bonding apparatus and method are effective in rapidly bonding bent or flexible flip-chip type semiconductor chips to a substrate with high quality without contact defects of solder bumps.