Laser Welding Bump Electrodes Spatial Light Modulator
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Solution Overview
Problem
Existing methods for welding bump electrodes to a wiring substrate face issues with non-uniform heating and prolonged processing times, particularly in achieving accurate and efficient welding of multiple electrodes.
Innovation Solution
An electrode welding method and apparatus utilizing a laser irradiation apparatus with a spatial light modulator to adjust the energy distribution of the laser beam, ensuring uniform heating of bump electrodes on a semiconductor chip, which are then welded to the wiring substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the whole of the back surface of the semiconductor chip is irradiated with a laser beam to heat and melt the bump electrodes, then the plural bump electrodes are simultaneously welded to connection terminals of a substrate, but the plural bump electrodes are not uniformly heated and the welding becomes non-uniform
Solution Approach 1:
The patent applies local quality by using a spatial light modulator to create different energy distribution patterns across the laser beam profile. This allows different regions of the semiconductor chip to receive appropriately tailored laser energy, ensuring uniform heating of bump electrodes even though they are located at different positions on the chip. The spatial light modulator adjusts the intensity distribution locally across the beam cross-section to compensate for variations in heat conduction and material properties.
2Manufacturing precision
If irradiation with a laser beam is individually executed with each individual bump electrode targeted, then the welding can be precise, but a long time is taken and it is difficult to accurately position the focal point position toward the bump electrode individually
Solution Approach 1:
The patent merges multiple individual welding operations into a single simultaneous operation by using a spatial light modulator to pattern the laser beam. Multiple focal points are created within a single laser beam profile, allowing simultaneous welding of multiple bump electrodes. This combining approach maintains the positioning accuracy of individual focal points while achieving the productivity of parallel processing, as all welded portions are processed in one laser irradiation step.
3Manufacturing precision
If irradiation with a laser beam is individually executed with each individual bump electrode targeted, then precise welding can be achieved, but it takes a long time to weld all bump electrodes
Solution Approach 1:
The patent employs periodic action through pulse modulation of the laser beam, controlled by a spatial light modulator. The laser beam is modulated into multiple pulses that sequentially or simultaneously target different bump electrodes. This periodic modulation allows precise control of energy delivery to each electrode while maintaining high-speed processing, as the pulsed nature of the irradiation enables rapid cycling through multiple welding points without the need for mechanical repositioning.
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 ensures uniform melting and efficient welding of bump electrodes, addressing non-uniform heating and reducing processing time by selectively adjusting heated regions with the spatial light modulator.
Implementation Method 1
a laser oscillator that emits a laser beam with a wavelength having absorbability with respect to the semiconductor chip
Implementation Method 2
a wavelength having absorbability with respect to the semiconductor chip
Implementation Method 3
a spatial light modulator that adjusts energy distribution of the laser beam emitted from the laser oscillator
Implementation Method 4
irradiating a back surface of the semiconductor chip with the laser beam and welding the bump electrodes of the device to the electrodes of the wiring substrate
Data Source
AI summary
An electrode welding method includes a laser irradiation apparatus preparation step of preparing a laser irradiation apparatus including a laser oscillator that emits a laser beam with a wavelength having absorbability with respect to a semiconductor chip and a spatial light modulator that adjusts the energy distribution of the laser beam emitted by the laser oscillator, an electrode positioning step of positioning, corresponding to electrodes of a wiring substrate, bump electrodes of a device, and an electrode welding step of irradiating the back surface of the semiconductor chip with the laser beam and welding the bump electrodes to the electrodes of the wiring substrate.