A formed plastic head can look satisfactory while the retained PCB has been loaded or heated differently from the intended construction. Qualify the entire heat-staking operation with the actual board and housing. Head appearance is one observation within that qualification, not the complete acceptance decision.
Identify the permitted retention method
Use the housing or module supplier’s drawing and assembly guidance. Record the plastic feature, PCB hole and board thickness. Confirm whether heat staking is the intended method for that feature rather than adapting an existing screw boss without approval.
Infineon’s HybridPACK Drive G2 guide presents heat staking as a defined PCB-retention option with tooling and process boundaries. Its example applies to that construction; another housing needs its own material and process qualification.
Review contact throughout the cycle
| Stage | Observation |
|---|---|
| Initial seating | Board position and support before deformation |
| Tool contact | Alignment to the intended plastic feature |
| Heating and forming | Approved thermal and force sequence |
| Cooling and release | Retention of the defined shape and board position |
| Final assembly | Clearance and integrity around each retained location |
Inspect the actual populated board in the fixture. Nearby components, underside terminations and board support can change the contact path compared with an unpopulated dimensional sample.
Use a trial that can reveal hidden effects
Measure the relevant retained geometry and perform the product’s mechanical and electrical checks. Where necessary, use destructive samples to examine the formed feature and surrounding interface. Select acceptance evidence with the design and process owners before the trial begins.
For example, a head may cover the PCB hole correctly but retain the board at a slight tilt because an adjacent feature prevented full seating. Checking the head diameter alone would miss the installed-board error.
Record the sequence if several staking positions are formed separately. If they are formed together, identify the tooling configuration that establishes alignment and loading across the board.
Record the material and condition of a replacement thermode. A tool that produces a similar visible head can still have a different contact geometry, so its first qualified samples should represent the actual replacement equipment.
Define rework before production
Determine whether removal, replacement or any repair is permitted. A permanent plastic retention feature should not be treated like a reusable fastener without evidence for the proposed service route.
Keep tool wear, plastic variant and board thickness changes visible in process review. Each can alter the formed result even when the nominal heating program remains unchanged.
The support-map guide helps describe physical contact, while fastener sequence review addresses an alternative mechanical operation with its own required order.
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