Record the exposure history
Keep packaging condition, storage requirements, opening time, and subsequent handling with the lot record. Include attached components, stiffener adhesives, and other materials when the circuit has already been assembled. Use traceability planning to decide which events must be retained. A bare laminate instruction may not apply to a populated assembly with additional process limits.
Handling instruction ownership
| Requirement | Question to resolve | Drawing or process record |
|---|---|---|
| Incoming material | What packaging and storage instructions apply? | Supplier-specific handling record |
| Opened material | What exposure history must be tracked? | Lot-linked handling log |
| Preparation | Is a drying step required and compatible? | Approved procedure for the complete item |
| After preparation | How is the prepared state preserved? | Defined transfer and storage conditions |
Obtain a construction-specific preparation instruction
Ask the material supplier and assembly provider whether drying is required and, if so, what controlled procedure applies to the complete item. Coordinate it with reflow planning. Document allowable support, atmosphere, temperature, duration, handling after preparation, and any limits on repetition as specified by the responsible suppliers; do not invent these values.
Investigate defects before changing the process
If blistering or separation appears, preserve failed and unprocessed samples and their histories. Review storage alongside lamination, material, assembly, and design evidence in a delamination investigation. Changing a drying step may be a testable hypothesis, but it should not erase the evidence or become an assumed root cause without comparison.
Before you release the design
- Use instructions for the exact material or assembly stage.
- Retain storage and processing history for suspect lots.
- Check compatibility with every attached material before heating.
- Record any deviation and the responsible disposition.
Watch points
- Do not publish a generic baking time and temperature as suitable for all flex boards.
Practical questions
Should every flex PCB be baked before soldering?
Determine that from the material, storage history, and approved assembly process. A blanket instruction can conflict with other materials or process limits.
Does baking prove that moisture caused a defect?
No. It changes a process variable. Establish cause through controlled comparison and examination of the failed interface, with the original history preserved.
Technical references
References support the material or design context. Check the exact grade, part number, document revision and project conditions before release.Updated 27 September 2026 · Technical content policy · Engineering guidance supports project review; the agreed drawing defines the build.