When should you use a SoM instead of designing a complete board?

Start with the system, not the processor

List the required interfaces, power budget, operating environment and software requirements. Then separate product-specific needs from functions an existing platform can provide. A SoM can integrate processing and memory, while a carrier board provides application interfaces.

The module does not eliminate carrier-board engineering. Power supply, startup sequencing, connectors, signal integrity and mechanical constraints remain part of the system. Assess the complete assembly, including thermal management and access to debug signals.

Compare total development cost

Compare alternatives across volume scenarios. Include the module, carrier, development, validation and software maintenance. A custom board may lower some unit costs, but it also requires investment and ownership of a larger portion of the platform.

Request documentation before committing to the architecture: pinouts, layout guides, reference schematics, supply conditions and lifecycle policy. Establish which software deliverables come with the module and how they will be maintained.

Validate risks before freezing the design

Use an evaluation kit to test critical interfaces, measure power consumption and run a representative application workload. Record differences between the kit and the future carrier. A successful kit test is initial evidence, not validation of the final board.

Document the decision: requirements met, limitations, supplier dependencies, estimated cost and a replacement strategy. The right platform is the one whose tradeoffs fit the product.