Silicon Piezoresistive Pressure Diaphragm Encapsulation Selection Criteria
Encapsulation selection balances gel potting low cost against oil-filled cell thermal stability to control long term zero drift and field recalibration expenses.
Micro-Laser Seam Welding
Thermal Junction
Modern electronic and sensor packaging utilizes miniature joints to seal sensitive internal elements without overheating adjacent circuitry. The technique of micro-laser seam welding achieves this by delivering rapid pulses of highly focused laser energy to form a continuous hermetic seam. It is primarily used for thin-gauge metal diaphragms and sensor capsules where heat must be localized within a few hundred micrometres.
Pulse Calibration
Process qualification demands rigorous calibration of the laser spot size and pulse-to-pulse overlap. The spot size is verified using a beam profiler to ensure a consistent energy density across the weld zone. An overlap of seventy to eighty percent is typically targeted to guarantee a continuous hermetic barrier without creating excessive heat build-up.
The energy output of the laser is measured before each production run using a calibrated thermopile sensor to ensure the total power remains within a specified tolerance of plus or minus three percent.
Focus Accuracy
Variations in the axial position of the focus relative to the workpiece alter the width and penetration depth of the weld. If the focus shifts too high, the laser power density drops, which leads to incomplete fusion of the seam. Conversely, a focus point that is too deep can cause excessive penetration and burn-through of thin metal diaphragms.
Precision multi-axis stages with optical height sensors are used to maintain the focus position within fifty micrometres across the entire weld path.
Metallurgical Boundary
Precision joining remains highly sensitive to surface contamination such as residual machining oils or oxide layers. Contaminants generate gas bubbles that lead to weld porosity and mechanical failure. This weakness makes cleanroom preparation necessary.