³Ô¹Ïtv

Read the woven-aramid architecture before the headline number

The official 45NK sheet identifies woven Kevlar aramid reinforcement and reports typical X-Y CTE of 5–7 ppm/°C, with a Tg of 170°C and IPC-4101/50 context. The architecture is part of the material identity, not a decorative detail in the product name.

Those source values do not establish the effective expansion of every copper-patterned board. Direction, copper balance and temperature interval need to be carried into the mechanical model. A finished multilayer is a composite of all its layers.

Evidence and construction decision

Define the dimensional requirement at the actual interface

Identify the package, mounting feature or optical/mechanical alignment that controls the design. State the reference datum, direction and temperature excursion. An outline tolerance measured at room temperature is a different requirement from displacement during operation.

If a ceramic package is the concern, use a length tied to the attachment geometry. If layer registration is the concern, define the fabrication and measurement stages. These two tasks can benefit from low expansion but require different evidence.

Use free mismatch to frame the mechanical discussion

The worksheet multiplies common length, coefficient difference and temperature change. Its generic 50 mm example with a 10 ppm/°C coefficient difference and 100°C excursion gives 50 µm free differential movement. The example is not a prediction for a particular 45NK board.

The result excludes restraint, bending, package compliance and solder behavior. It cannot prove a reduction in fatigue failures. Use the sign and magnitude to check assumptions, then evaluate the constrained assembly with the method appropriate to the project.

Compare the reinforcement routes separately

55NT uses nonwoven aramid with epoxy, and 85NT uses nonwoven aramid with polyimide. Compare resin, reinforcement, process and source-qualified properties as distinct fields. Similar in-plane CTE ranges do not establish interchangeable construction.

If thick copper clearance filling is the actual problem, 84HP addresses a different filled-prepreg task. Low expansion and gap filling are not the same manufacturing requirement, even when both occur in one multilayer design.

Free differential thermal expansion

Optional cost comparison from your own allowances

Use a quotation or a clearly labeled internal assumption for each input. Keep the quantity, construction and inspection scope the same when comparing alternatives. This uncalibrated planning model adds entered values; it contains no current market rates and does not issue a ³Ô¹Ïtv quotation. You can contact the team without completing it.

Review press and dimensional controls for the actual stackup

The supplier's process discussion notes that aramid fabric compression and distortion require attention to pressure. This is a reason for a qualified layup and process, not an invitation to copy a universal pressure setting from a website.

Provide copper distribution, layer symmetry, thickness and critical registration features. Agree the measurements needed after fabrication and assembly. The public sheet's availability table also requires clarification before treating its 85N-prefixed entries as 45NK order codes.

Build a quotation around the controlled dimensions

Send the exact 45NK callout, stackup, copper, package or mounting interface, thermal range and dimensional limits. Include quantity, evidence requirements and the permitted alternative policy. State which dimensions are inspection characteristics and which are analysis assumptions.

The cost worksheet uses only entered allowances. It cannot price a special construction or qualify a dimensional claim. The useful next step is an agreed material and manufacturing proposal with a measurable verification plan, preserved with the drawing for future orders.

Review the package, board and attachment together

The finished board combines a dielectric, copper patterns, holes, surface coatings and a manufacturing history. Its behavior cannot be inferred from a family name alone. State the supplied grade, reinforcement, thickness, copper and processing conditions that matter to the intended application.

Keep handling and assembly requirements with the fabrication drawing. A thin panel, punched outline or unusual support condition can change the production route even when the electrical circuit is simple. Ask the fabricator to review the actual features and panel format rather than assuming a dimensional example represents a production capability.

For cost comparison, hold the drawing, quantity, test scope and acceptance requirements constant. Record one-time tooling separately from recurring work, and distinguish raw material utilization from accepted-board yield. Any calculator on this page uses supplied assumptions; an actual quotation requires the files and an agreed scope.

A source-qualified table should be read alongside the exclusions and footnotes, not separated from them. If the supplier limits an application, identify whether that limitation affects the current design before requesting a price. A familiar family classification does not override an explicit restriction, and a positive calculator result cannot remove it.

For a repeat build, compare the newly proposed supply with the previously approved material record. Exact grade, manufacturing site where relevant, foil treatment, reinforcement and dimensional basis can matter. Define which changes require notification and which need technical approval. This avoids turning a purchasing substitution into an unnoticed design change.

Receiving records should support the agreed identity and traceability requirement. A certificate for a raw material, a finished-board inspection report and an assembly test result cover different boundaries. Request the records that actually answer the project questions rather than collecting unrelated certificates.

When a source contains conflicting values, keep the discrepancy visible until a controlled revision or written supplier response resolves it. Do not create a new table by combining the most favorable entries from several sources. The released drawing, material list and quotation should all describe the same accepted construction.

Compare in-plane expansion along the same direction and temperature interval. A package body, ceramic carrier, copper pattern and reinforced board need not move equally. The free differential-expansion result identifies a dimensional mismatch; it does not calculate solder-joint strain because joint geometry, distance from the neutral point, constraints and temperature cycling are excluded.

Record woven or nonwoven reinforcement explicitly. The fiber architecture can affect drilling, dimensional behavior and moisture response independently of the resin family. Do not choose a replacement solely because its nominal expansion is close to a package value. The finished construction and attachment must be reviewed together, including any permitted assembly repair.