Picosecond UV Laser Micromachining Reduces Thermal Damage
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Solution Overview
Problem
Current laser micromachining technologies face challenges in achieving high throughput and machining quality for layered organic, inorganic, and metallic microelectronic materials, particularly in materials like FR4 and green ceramics, due to suboptimal wavelengths, pulsewidths, pulse energies, and repetition rates.
Innovation Solution
Employing a picosecond pulsewidth solid-state UV laser for via drilling and ablation of electronic materials, which reduces the number of pulses required for cleaning and improves machining efficiency by creating steeper temperature gradients, thereby reducing thermal damage and enhancing sidewall quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If Q-switched UV laser with nanosecond pulsewidth is used for via drilling, then material removal capability is achieved, but thermal damage and heat-affected zones increase requiring multiple cleaning pulses
Solution Approach 1:
The patent changes the pulsewidth parameter from nanosecond (Q-switched) to picosecond regime, which fundamentally alters the laser-material interaction mechanism. This parameter change reduces thermal diffusion time and minimizes heat-affected zones, thereby reducing the number of cleaning pulses needed while maintaining effective material removal capability
Solution Approach 2:
The patent employs ultrafast picosecond pulsed laser action instead of continuous or longer-pulse periodic action. The extremely short pulse duration creates a non-thermal ablation regime that removes material without significant heat diffusion, reducing the need for subsequent cleaning operations
2Quantity of substance
If longer pulsewidth lasers are used for material removal, then material vaporization capability is achieved, but thermal diffusion increases causing larger heat-affected zones
Solution Approach 1:
The patent changes the temporal parameter of pulsewidth from nanosecond to picosecond scale, which is sufficient to vaporize and remove material through ablation while being short enough to prevent significant thermal diffusion into surrounding areas, thus achieving both material removal and minimal thermal damage
Solution Approach 2:
The ultrafast picosecond laser pulses deliver energy so rapidly that material vaporization occurs before heat can diffuse to surrounding areas. This 'rushing through' the thermal process allows effective material removal with minimal heat-affected zones
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 picosecond pulsewidth solid-state UV laser significantly reduces the number of pulses needed for pad cleaning, decreases thermal diffusion, and improves machining quality by minimizing heat-affected zones and thermal damage, especially in materials like FR4 and green ceramics.
Implementation Method 1
improves machining efficiency by creating steeper temperature gradients, thereby reducing thermal damage
Implementation Method 2
employing a picosecond pulsewidth solid-state UV laser for via drilling and ablation of electronic materials
Data Source
AI summary
In some embodiments, laser output including at least one laser pulse having a wavelength shorter than 400 microns and having a pulsewidth shorter than 1,000 picoseconds permits the number of pulses used to clean a bottom surface of a via or the surface of a solder pad to increase process throughput. An oscillator module in cooperation with an amplification module may be used to generate the laser output.