Laser Hole Formation in Brittle Substrates With Stress-Relief Heating
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Solution Overview
Problem
Laser ablation-based hole forming methods in brittle materials like glass and ceramics often result in crack formation around holes, which reduces substrate strength and requires time-consuming etching to repair, increasing costs.
Innovation Solution
Heating the substrate to a temperature between 500°C and 1500°C, above the annealing point but below the softening point, followed by irradiation with an IR laser to form holes, which reduces stress and prevents crack formation by relaxing transient and residual stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser ablation is used to form holes in brittle substrates, then hole formation is achieved, but crack formation occurs around the holes
Solution Approach 1:
The substrate is heated to a temperature above the annealing point before laser hole formation. This preliminary heating action reduces residual stresses in the substrate, preventing crack formation during subsequent laser drilling while maintaining hole formation efficiency
Solution Approach 2:
The thermal state of the substrate is changed by heating it above the annealing temperature. This parameter change (temperature) modifies the substrate's mechanical properties, reducing its brittleness and preventing crack propagation during laser processing
2Reliability
If etching is performed to remove cracks, then substrate strength is improved, but production time and cost increase
Solution Approach 1:
Heating the substrate above the annealing point before laser drilling prevents crack formation in the first place. This preliminary stress relief action eliminates the need for subsequent etching processes, reducing both time and cost while maintaining substrate strength
Solution Approach 2:
The heating process, which could be seen as an additional step, actually converts a potential harm (crack formation) into a benefit (crack prevention). By heating above the annealing point, residual stresses are relieved, transforming the substrate into a state that resists crack formation during laser drilling
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 effectively minimizes crack formation during hole creation, maintains substrate strength, reduces the need for post-drilling treatments, and enables faster, more cost-effective production of panel components with multiple holes.
Implementation Method 1
heating at least a portion of the substrate at least to the depth d to a temperature Tp that is above 500° C. and below 1500° C., to form a heated area of the substrate
Implementation Method 2
irradiating at least a portion of the heated area of the substrate with a laser beam emitted from an IR laser to form at least one hole in the substrate
Implementation Method 3
heating the substrate during hole formation, and preferably heating the substrate or keeping the substrate's temperature elevated above 600° C. but less than 1000° C. (or example to a temperature Tp that is above 600° C. and below 1000° C.) for at least 1 to 30 minutes after the hole formation, inhibits crack formation around the holes in brittle substrates
Data Source
AI summary
A method of making a brittle substrate comprising the steps of: (i) heating at least a portion of the substrate at least to the depth d to a temperature Tp that is above 500° C., but below 1500° C., to form a heated area of the substrate; and (ii) irradiating at least a portion of the heated area of the brittle substrate with a laser beam emitted from an IR laser to form at least one hole in the brittle substrate.