Incoming and Functional Tests: Sensor and Controller Checks

QC starts with functional verification of the complete stack: the sensor, the controller, and the host interface working together. Tests include power-on behavior, touch registration, and controller communication. The goal is to catch dead channels, failed controllers, and assembly faults before reliability testing spends time on a defective sample.

Functional Performance: Accuracy, Response, and Edges

Functional performance is measured, not felt:

• Accuracy — how close reported touches land to the target, measured on a grid (for example, 9-point or 25-point) with a stated tolerance.
• Response — registration latency and reliable detection of taps and drags.
• Edge and corner behavior — the areas where sensors and tuning often lose performance; test the full active area, not just the center.

Accuracy methodology belongs with the calibration guide; QC applies its tests as acceptance criteria.

Reliability Tests: Touch Life, ESD, Drop, and Vibration

Reliability testing stresses the module the way the product will use it:

• Touch life — millions of actuations on resistive or repeated touches on PCAP, checking for wear and drift.
• ESD — electrostatic discharge at the levels the product environment demands.
• Drop and vibration — mechanical stress that can crack the sensor or break bonds.

Each test needs a method, levels, sample count, and pass criteria agreed before testing. Vibration and environmental method details belong to the reliability guides; touch QC selects and applies them.

Environmental Tests: Temperature, Humidity, and Shock

Touch stacks change behavior with temperature and humidity: adhesives soften, sensors drift, and condensation can create false touches. Qualify the stack across the product’s environmental range with thermal cycling, humidity exposure, and thermal shock where the application demands it. The display-level environmental methods have their own owners; the touch module’s QC uses them to validate the stack.

Optical QC: Transmittance, Haze, and Coating Inspection

Touch layers sit between the user and the display, so they cost light and add haze. Optical QC verifies transmittance and haze against the specification and inspects the cover and coatings for scratches, particles, and coating defects that would show on the screen. Optical numbers must be measured under stated conditions, because small changes in measurement geometry change the result.

Documentation: COA, Test Reports, AQL, and Traceability

QC without documentation is unverifiable. Require:

• Certificate of analysis (COA) — the lot’s test results against the specification.
• Test reports — reliability and environmental results with methods and sample identity.
• Traceability — lot records that tie the module back to its materials and process.

Acceptance sampling and defect classification follow AQL practice, which is a general mechanism owned by the LCD AQL guide; touch QC applies it to touch modules. Example AQL and accuracy figures in supplier material are external references, not a CDTech commitment.

Frequently Asked Questions