Understand what the sensor measures physically
An inertial sensor, temperature sensor and pressure sensor respond to different aspects of their surroundings. Identify the intended measurand and the unwanted effects that could resemble it. This prevents a compact layout from placing a temperature sensor next to a heat source or a strain sensitive package near a mounting load.
ST's MEMS guidance describes how board and assembly stress can affect sensor behavior. Use the selected component's documentation to review mechanical placement, and record the mounting arrangement alongside the electrical design.
Use an error budget to guide layout effort
List the measurement uncertainties that matter to the application, then identify which can be influenced by PCB geometry or assembly. Reserve attention for those contributors rather than making every trace equally short. Include supply and reference behavior where they affect the selected sensor architecture.
Plan a prototype measurement that can distinguish electronic noise from mounting or thermal effects. For example, compare readings before and after enclosure fastening under otherwise similar conditions. State the purpose and limits of the comparison in the test record.
Protect the sensing environment while shrinking
Compare an HDI layout with a modestly larger layout using the same package location and mechanical datums. If the denser version moves a regulator or connector close to the sensor, evaluate the resulting tradeoff explicitly. Area savings do not necessarily improve the useful measurement volume.
- Mark sensor axes, ports or exposed surfaces in assembly documentation.
- Review fasteners, shields and adhesive near the sensor.
- Define assembly handling and calibration stages.
- Reserve supply and reference measurements without disturbing the sensing region.
Control the calibrated configuration
Record whether calibration occurs on a bare assembly or inside the completed housing. Changes in bonding, screws or support can make those configurations different. Tie calibration data to a board identifier and the relevant mechanical revision.
When transferring production, examine the process steps that can alter stress or temperature exposure. Use comparative builds where needed, with a defined acceptance method. A material or assembly substitution should not be considered equivalent solely because the board still passes continuity testing.
Adjacent-layer access, one connection at a time
Dielectric · geometry + material
Core or build-up dielectric
Illustrative only. Copper thickness, dielectric construction and via spans require a reviewed stackup.
Common questions
Will a smaller PCB always improve sensor accuracy?
No. It may change strain, heat flow, coupling and access to the measured environment. Accuracy needs to be evaluated against the intended assembled configuration.
When should sensor calibration be planned?
During architecture and assembly planning. Determine which configuration the calibration represents and which later operations could change the sensor's behavior.
References & further reading
Method & assumptions · General design guidance. Validate the proposed construction and acceptance criteria for your project.