Engineering practice
The recurring work is to turn a broad technical request into a system that can be designed, procured, tested and accepted without losing the physical process along the way.
1 · Start from the operating window
I separate the required process window from the supplier's preferred equipment configuration. Pressure, gas load, temperature, power, geometry, material state, throughput and diagnostic needs become the basis for reviewing chamber architecture, pumps, valves, sources, heating, gas delivery, fixtures and controls.
2 · Turn requirements into interfaces
Vacuum
Pump-down, base pressure, process pressure, gas load, conductance, isolation, leak rate and pressure measurement.
Process
Source or discharge mode, gas chemistry, heating, power, fixtures, material compatibility and recipe limits.
Control
Sensors, interlocks, calibration, state logic, data logging and the sequence required to reproduce the process.
3 · Review supplier claims against measurements
A component list is not an acceptance test. A proposed pump, gauge, MFC or power supply matters only through the performance of the assembled system. For this reason I prefer acceptance criteria that can be measured at system level: pressure-time behaviour, leak rate, stable process pressure, flow accuracy, temperature uniformity, electrical operating window and repeatability.
4 · Qualification should preserve traceability
| Stage | Useful output |
|---|---|
| Requirement | Measurable process and component acceptance criteria |
| Design review | Interface map, sizing basis, instrumentation and risk list |
| Manufacturing / assembly | Material, geometry, calibration and configuration traceability |
| FAT | Measured system performance and deviations against the agreed criteria |
| Process transfer | Recipe limits tied to material / component results, not only machine settings |
| Operation | Data logs sufficient to diagnose drift and reproduce accepted conditions |
5 · Failure analysis is part of design
When a vacuum or plasma process fails, the useful path is usually to separate vacuum, gas delivery, electrical state, heating, geometry, material surface condition, diagnostics and control sequence rather than changing several variables at once.
This same structure is useful before the equipment exists: if the failure modes are known early, the necessary sensors, access points, calibration and acceptance tests can be designed into the system.
Question → parameters → physical check → records → reject condition
Vacuum coating system acceptance
Question: does the assembled system meet the process window rather than only the component list?
Check: pump-down trace, base pressure, isolated pressure rise, leak result, process-gas pressure and repeatability.
Reject: acceptance depends on a single ultimate-pressure number or untraceable gauge reading.
LPC recipe transfer
Question: does the transferred recipe reproduce the required case on the actual load?
Check: boost/diffusion sequence, temperature, pressure, load geometry, case profile, microstructure and distortion.
Reject: recipe settings match but case depth/microstructure or dimensional behaviour does not.
Cathode-neutralizer testing
Question: can the cathode start, transition and sustain emission reproducibly?
Check: flow/pressure, ignition V-I-time trace, keeper/main transition, drift, restart and post-test condition.
Reject: one ignition is treated as qualification, or damaging transients remain unexplained.
TVAC chamber under xenon gas load
Question: does the chamber remain in the intended test regime with propellant flow?
Check: xenon throughput, effective pumping, chamber pressure, gauge location and stabilization.
Reject: base pressure alone is used to represent loaded test performance.
Plasma nitriding / duplex route
Question: does the process improve the functional surface without losing geometry or substrate support?
Check: layer depth/structure, dimensions, roughness, hardness profile and representative tribology.
Reject: surface hardness rises but tolerance, compound-layer state or tribological performance is unacceptable.
Avinit route for a sliding pair
Question: which surface state is needed on each member of the pair?
Check: substrate support, diffusion/coating route, roughness, lubrication, counterbody and wear/friction response.
Reject: coating hardness is used as a proxy for pair performance.