State the mechanical purpose
Explain whether separate leaves serve installation geometry, relative movement, or another packaging need. Identify which layers form each leaf and where they become one assembly. Compare the concept with a fully bonded option under the same installed constraints. The air-gap construction guide focuses on the space and handling questions created by separated leaves.
Selective-bonding definition
| Stack feature | Specify | Engineering question |
|---|---|---|
| Leaves | Copper, dielectric and protection per leaf | What moves independently? |
| Bond map | Bonded and unbonded boundaries | How is the region manufactured? |
| Transition | Join length and nearby features | How do loads enter the bonded area? |
| Assembly | Leaf order and restraints | Can parts rub, snag or be reversed? |
Draw bonding boundaries in two views
Provide a plan view of bonded and unbonded areas plus sections through both and their transition. Specify material extents, conductor continuity, protection, and any features near the boundary. Use bonding-layer definition to identify the material being selectively applied. Ask how the fabricator proposes to create and verify each region.
Review motion and assembly at the transition
An unbonded span can move differently from a single laminated beam, but its useful behavior depends on restraints and the installed path. Check leaf interference, sliding, edge contact, and how the leaves enter the bonded region. Define handling instructions and a representative prototype test. Do not claim a bend-life improvement until the actual construction has evidence relevant to its duty.
Before you release the design
- Explain why selective bonding is needed.
- Provide region and section drawings.
- Define leaf order and orientation.
- Agree an inspection approach.
- Test the actual transition and restraints.
Watch points
- An unbonded region without defined terminations can transfer an unresolved problem to its bonded ends.
Practical questions
Is selective bonding the same as an air gap?
They are related concepts but describe different aspects: where layers join and how separated layers occupy space. Define both when both matter.
Can it be added late to reduce thickness?
It changes the mechanical construction and processing. Review the full concept rather than treating it as a simple adhesive deletion.
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.