Assign the thickness to a function
Identify whether the film separates conductors, supports a single copper layer, covers traces, or reinforces a terminal. A film used in coverlay has an additional adhesive decision. Qnity’s Kapton specifications list multiple film grades and gauges; a listed film option does not establish availability in a particular copper-clad construction. Confirm the proposed laminate, not just the raw film.
Film-thickness choices by location
| Decision | Define | Review |
|---|---|---|
| Base dielectric | Available laminate grade | Copper and electrical spacing |
| Cover film | Film plus bonding layer | Openings and total insulation |
| Terminal reinforcement | Local finished thickness target | Connector tolerance budget |
| Moving span | Complete local stack | Motion geometry and handling |
Work from the critical region
Calculate the free span, connector tail, and reinforced island separately. Show where film is continuous and where an opening removes it. Use the stack thickness worksheet to include adhesive, copper, protection, and reinforcement. For a mating tail, the connector drawing controls the finished section; the film choice follows that combined requirement.
Compare electrical and mechanical consequences
A changed dielectric thickness can affect routing geometry, insulation questions, and the mechanical review. Do not preserve a controlled-impedance trace width without checking the new construction. Ask the fabricator how the proposed film fits handling and registration needs for your outline. The dimensional-stability guide helps define which post-process dimensions need attention before finalizing a thin construction.
Before you release the design
- Label film thickness separately from finished board thickness.
- Confirm the material combination is available.
- Revisit impedance after a dielectric change.
- Specify critical dimensions after processing.
Watch points
- Do not calculate connector fit from base film alone.
Practical questions
Can a film's nominal gauge be the board thickness?
Only if it describes an isolated film item. A circuit includes other physical layers, and the critical section must account for them.
Does thinner film guarantee more bend cycles?
No. Copper, layer order, bend path, processing, and the installed environment remain part of the mechanical qualification.
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.