Start at the package and end at the environment
Trace the expected heat flow from the die through the package pad, solder joint, board copper, and eventual cooling path. TI's exposed-package thermal-layout guidance evaluates how board copper and via arrangements affect thermal behavior. Its results are tied to the simulated structures. Use them to identify variables worth reviewing, not to assign your assembly a thermal resistance copied from a different board. Include enclosure, airflow, heatsink contacts, and nearby heat sources.
Confirm the pad's electrical role
An exposed pad is not automatically ground. Check the device datasheet before connecting it to planes or adding a via array. Where direct copper connection is appropriate, ensure that plane-pour settings do not unintentionally reduce the useful heat path to narrow spokes. Also inspect isolation requirements and clearances to neighboring electrical regions. A thermally attractive copper connection that violates the package's electrical function is not a viable solution.
Coordinate the via array with solder deposition
Vias in an exposed land can interact with solder volume and voiding. Discuss hole size, filling or capping, mask treatment, stencil apertures, and inspection expectations with the assembler and fabricator. Different packages and processes may need different approaches. Avoid copying a universal tenting instruction from an unrelated application note. Specify the actual structure needed beneath the component and make sure the manufacturing files and assembly documentation describe the same arrangement.
Evaluate whether more vias address the bottleneck
Compare an added via row with a larger connected copper area or an improved path to the chassis. If the receiving plane is isolated or the final cooling path is weak, additional vias may have limited benefit. Use simulation or a controlled prototype comparison where temperature margin is tight. During measurement, record power dissipation, ambient conditions, airflow, board orientation, and measurement location. That context makes a thermal result useful for the product's operating case.
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
Are more thermal vias always better?
No. The value depends on the complete heat path and assembly constraints. Additional vias can have diminishing benefit if spreading or external cooling dominates.
Can I use the datasheet junction-to-ambient value directly for my board?
Only with care about the stated test conditions. A different copper structure, enclosure, or airflow can produce a different thermal result.
References & further reading
Method & assumptions · General design guidance. Validate the proposed construction and acceptance criteria for your project.