Laser Ablation of Unsupported Polymer Layers
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Solution Overview
Problem
Laser ablation of openings in polymer layers over cavities can result in 'chads' that fall into the cavity, causing blockages in fluidic structures and interfering with subsequent laser processing, due to uneven etching rates leading to the center portion dropping into the cavity.
Innovation Solution
A two-step laser ablation process where the first step creates a wider opening shape and the second step uses a smaller laser spot to avoid penetrating the thinner edges, ensuring the center portion remains attached, and the edges are controlled using laser masks or optical adjustments to prevent chad formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If laser ablation is used to create openings in polymer layers over cavities, then openings are formed for fluidic structures, but chads form and fall into the cavity causing blockages
Solution Approach 1:
The laser ablation process is divided into multiple passes with different parameters. The first pass creates an initial opening with specific shape and depth, while subsequent passes refine the opening with different laser settings. This segmentation of the ablation process allows control over chad formation by adjusting pulse duration, power, and overlap between passes.
Solution Approach 2:
The method performs preliminary laser ablation passes that create controlled etching patterns before final opening formation. These preliminary passes prepare the material by creating stress patterns and partial removal that prevent uncontrolled chad formation during subsequent ablation steps. The preliminary action establishes a foundation for clean opening creation.
2Productivity
If laser ablation parameters are increased to improve etching speed, then productivity increases, but chad formation increases due to uneven etching rates
Solution Approach 1:
The laser ablation employs periodic pulsed action with specific duty cycles and repetition rates. By using short pulses with adequate cooling intervals, the process maintains high average power for productivity while preventing excessive heat accumulation that causes uneven etching and chad formation. The periodic nature allows thermal diffusion between pulses to promote uniform material removal.
Solution Approach 2:
The method dynamically changes laser parameters during the ablation process, including pulse duration, power level, scanning speed, and pulse overlap. These parameter changes are applied in sequences or gradients across the material surface to maintain optimal etching conditions throughout the process, preventing the formation of chads while sustaining high productivity.
3Device complexity
If a single laser pass is used to create openings, then the process is simple and fast, but chads form and may interfere with subsequent laser etching
Solution Approach 1:
The laser processing is segmented into distinct passes: a first pass that creates the primary opening structure, and a second pass that refines the opening and removes potential chads. This segmentation ensures that subsequent laser etching operations can proceed without interference from chad material, improving reliability of the overall manufacturing process.
Solution Approach 2:
The first laser pass performs preliminary action by creating the initial opening structure and removing material that could form chads. This preliminary pass prepares the surface and cavity interface for subsequent processing, preventing chad interference with second laser etching operations and ensuring reliable multi-step manufacturing.
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 method prevents the formation of chads, ensuring fluid flow through the structure and avoiding obstructions that could cause equipment failures or faults in the manufacturing process, while maintaining precise control over the opening shape and size.
Implementation Method 1
ablating the portion of the first material over the cavity at a first shape, and ablating the portion of the second material over the cavity at a second shape
Implementation Method 2
methods of ablating openings in unsupported layers of material
Data Source
AI summary
A method of forming openings in a polymer layer includes positioning a layer of a material over a cavity such that a portion of the first material lies over a cavity, ablating the portion of the material at a first shape, and ablating the portion of the material at a second shape, wherein the second shape lies within the first shape. A method of forming openings in a polymer layer includes positioning a layer of a first material over a second material having a cavity such that a portion of the first material lies over the cavity, ablating the portion of the first material over the cavity at a first shape, and ablating the portion of the second material over the cavity at a second shape, wherein the second shape lies within the first shape.