Through-hole and surface-mount assembly describe how components attach to a PCB. Through-hole leads enter specified board holes; surface-mount terminations connect to surface pads. Neither approach is universally better, and a single assembly can use both.
Start with the actual component
Choose a part that meets the electrical and mechanical requirements, then evaluate its available packages. A connector with a defined mating interface may constrain the choice differently from a small passive component. Avoid changing a package solely to fit a broad preference for one technology.
Check footprint and pin mapping using the exact order code. A through-hole lead does not create its own hole during assembly; the fabricated board must already contain the required hole geometry.
Compare the practical tradeoffs
| Question | What to evaluate |
|---|---|
| Available space | Package outline, routing and access on both board sides |
| Mechanical interface | Expected loads and the intended support arrangement |
| Assembly method | Compatible soldering process and necessary tooling |
| Inspection | Which connections are visible or need another method? |
| Service | Whether replacement is intended and practical |
Do not equate through-hole with hand soldering
Ersa’s selective-soldering overview describes processes for joining individual through-hole components to a PCB. Automated methods may therefore be available, depending on the board. Similarly, surface-mount work can include manual operations in prototypes or rework.
The relevant choice is a controlled process suitable for the component set. Ask the assembler to review access and neighboring parts rather than assuming that one package category dictates one universal production sequence.
Review a mixed assembly as a whole
Consider what happens to already assembled parts during later operations. Review support, handling and any fixture requirements. Include component-specific restrictions and the intended cleaning or coating steps in the process discussion.
Decide when inspection and functional testing occur. Some connections become difficult to access after mechanical integration, so the acceptance plan should account for the sequence.
Compare total implementation cost
Include component price, board area, tooling, assembly and inspection. A smaller package does not automatically lower every cost, and a mechanically convenient package may still require additional process work. Ask for separate setup and recurring costs when comparing a prototype build with a later production quantity using the same parts.
Use a representative build to confirm the chosen combination. Document the approved footprint, fitted part and assembly instructions so later substitutions do not silently change the connection requirements.
Primary reference: Ersa selective soldering information. See the through-hole and surface-mount assembly guides.
Move from reading to a build-ready project
Use the fabrication and assembly checklists to prepare drawings, production files and test requirements.
Open the DFM checklist