Using drill size as the insertion size
Plating changes the finished opening. State finished hole requirements and the lead geometry used to establish fit.
Services / PROJECT FIELD GUIDE
Through-hole Assembly
Include connectors, power components and mechanical loads in the assembly plan.
TAKE THIS PAGE INTO YOUR NEXT REVIEW
Less guesswork. A clearer release.
- Understand the relevant choices
- Compare requirements and next steps
- Download useful notes for your review
What to know before you decide
Through-hole assembly inserts component leads into PCB holes before soldering. It remains useful for many connectors, larger components and assemblies where mechanical interfaces dominate the design. Successful assembly requires more than a lead fitting into a hole: finished hole size, lead geometry, solder access, thermal mass and component processing limits must work together. Specify the exact component and board thickness, then review how the selected soldering process reaches every required joint.
01 / DECISION GUIDE
Make the trade-offs explicit
01
Check finished-hole fit with the real lead
Use the component drawing and account for the lead's maximum dimensions, not only its nominal round diameter. Include plating and finished-hole tolerance in the PCB review. For rectangular pins, consider the geometry required for insertion. Verify hole location and connector mating position together, because an easy insertion does not guarantee the assembled connector aligns with the enclosure.
02
Choose access before choosing the process
Compare hand, selective and wave soldering in the context of the assembled board. Nearby underside components, tall obstructions and thermal mass can affect access or heat delivery. A layout that is simple to hand solder may need changes for repeat production. Ask for the proposed process sequence and tooling constraints while component placement can still be changed.
03
Separate solder joints from structural support
Identify insertion forces, cable loads and handling forces at connectors and heavy parts. Use the component's intended mounting provisions and review enclosure support where necessary. Solder joints should not silently inherit every mechanical load. Drawings should distinguish electrical termination requirements from screws, clips, staking or other agreed retention features.
04
Define inspection and special handling
Specify polarity, insertion height, lead forming or trimming and any areas that must remain free of residues. Use the actual connector application specification for its processing limits. Agree how joints with restricted visibility are assessed and how repairs are documented. Product-specific requirements should be attached to the job rather than assumed from a generic workmanship label.
Compare the choices
| Route | Useful context | Review constraint |
|---|---|---|
| Hand soldering | Small lots and accessible joints | Consistency and operator access |
| Selective soldering | Mixed boards with defined solder locations | Nozzle access and nearby parts |
| Wave soldering | Suitable repeated through-hole patterns | Underside protection and thermal exposure |
| Mixed process | SMT plus selected through-hole parts | Sequence, masking and total exposure |
Questions that prevent rework
Ignoring connector seating
A tilted or floating connector may solder successfully yet fail its mechanical interface. Define seating and retention.
Applying another connector's temperature limits
Read the exact manufacturer's specification. Housing materials and approved processing methods differ.
Get a clear answer
Can SMT and through-hole parts be assembled together?
Yes, with a reviewed sequence and access plan. Identify underside parts, temperature-sensitive components and any masking or special tooling required.
Which soldering route is cheapest?
It depends on lot size, access, tooling and process time. Compare the complete assembly plan rather than assuming hand, wave or selective soldering is always the lowest-cost route.
What should the drawing show for connectors?
Include exact part number, orientation, seating, retention and critical mating dimensions. Record any lead-forming or insertion-height requirements that affect the finished product.
Technical references
Check each source’s scope and revision against your project requirements. Confirm the proposed construction with your manufacturing partner.
YOUR PROJECT / YOUR NEXT STEP
Build a useful project brief
Build a through-hole process brief from board mix, access and mechanical loading.
Use this planning aid to prepare a review. It does not approve a design or estimate a price. Selections are processed locally and are not submitted by this tool.