Write the exposure history
Record temperature, duration, repetitions, atmosphere, and mechanical restraint for each exposure. A soldering excursion and years of operation answer different material questions. Use the assembly-profile guide to capture process heat and keep it separate from the operating requirement. Include rework if it is part of the intended production or service route.
Separate thermal requirements
| Decision | Define | Review |
|---|---|---|
| Assembly heat | Profile and number of exposures | Materials and component compatibility |
| Sustained service | Temperature and duration | Relevant aging evidence |
| Thermal cycles | Extremes, transition and restraint | Product-level dimensional and joint checks |
| Local heating | Load and heat-removal path | Actual temperature at critical features |
Review every constituent
List base film, laminate interfaces, coverlay adhesive, stiffener attachment, finish, components, and connectors. A film’s test result cannot qualify the rest of the assembly. Supplier data should be relevant to the selected grade and exposure. Where a property is missing, request evidence or propose a focused test rather than borrowing a limit from another material family.
Qualify the relevant failure modes
Decide what thermal exposure could change in your product: alignment, bond integrity, insulation, resistance, contact operation, or movement behavior. Coordinate thermal-cycle planning with the installed mechanical conditions. Measure the features tied to acceptance before and after exposure, and document sample construction. Qualification is most useful when it can distinguish a material issue from assembly damage or an unsuitable installation.
Before you release the design
- Specify exposure duration as well as temperature.
- Include all adhesive and connector materials.
- Define acceptance measurements.
- Record the exact tested construction.
Watch points
- A solder-float test is not a continuous-use rating for the finished circuit.
Practical questions
What is the maximum temperature of a polyimide PCB?
There is no single value that covers every construction and duty. Define the assembly and exposure, then review its limiting constituents.
Does a high-temperature film remove the need for baking controls?
No. Storage, moisture handling, and assembly preparation need their own reviewed process instructions.
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.