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Select the bonding construction, not just a glass style

ITEQ prepreg selection connects a resin system, reinforcement construction and manufacturing process to the required pressed bondline. A glass-style number alone does not specify thickness, resin content or compatibility with the chosen core. The useful specification identifies the exact prepreg grade, glass style, resin content, ply count and an approved pressed dimension under the intended construction.

The generic material definition belongs on the PCB prepreg page. This guide focuses on applying that idea to an ITEQ material assignment. For example, the IT-180A family’s manufacturer documentation distinguishes IT-180ATC copper-clad laminate from IT-180ABS prepreg. Do not describe every core and bondline using the same shortened laminate label.

The worksheet here adds dimensions supplied by you or a reviewed manufacturing source. It does not contain a universal ITEQ glass-style thickness library. An official model or manufacturer-provided construction table may support selection, but the production pressed result still needs to be agreed for the actual copper pattern, materials and process.

Five fields that make the requirement usable

Keep the source and revision beside these fields. A catalogue example may represent one copper construction, while the board being designed has a different distribution of retained copper. Do not detach a thickness value from its test or modeling basis. If a supplier supplies a complete pressed bondline thickness, do not multiply it again by the number of plies already included in that value.

For a current material-family overview, refer to the . Its headline Dk/Df groups use different resin-content references. Those reference groups are not instructions to choose the same resin percentage for every prepreg layer in an actual PCB.

Add supplied pressed-ply contributions

Enter one row per distinct ply construction: grade, glass style, resin content, quantity, nominal pressed contribution and plus/minus allowance. Thickness is in micrometres. The tool multiplies each contribution by its quantity, then adds the nominal values and the absolute tolerances. It compares the nominal sum with a target complete bondline dimension.

Two hypothetical contributions of 70 ± 10 µm produce a 140 µm nominal sum and a conservative arithmetic range of 120–160 µm. These are illustrative inputs, not published ITEQ 1080 values. The result assumes that the supplied contributions are meaningful for the intended construction. It does not determine them from the glass style or the entered resin content.

Worst-case addition is deliberately different from a statistical tolerance calculation. It does not assume that positive and negative deviations cancel, that measurements are independent, or that a chosen interval predicts production yield. If a supplier specifies the whole bondline directly, use that approved value in the final stackup and retain the detailed ply record as its supporting definition.

The downloadable brief preserves every row and its source note. Editing any input invalidates the result and disables the old download until you calculate again. The Contact route remains available without a result. Downloading the brief does not send it to ³Ô¹Ïtv; attach it manually when you want an engineering review.

Why resin content cannot be treated as a thickness percentage

Resin content is normally expressed as a mass fraction for the defined prepreg. For a simplified material balance, let G be the glass areal mass and r the resin mass fraction written as a decimal. Resin areal mass is G × r / (1 − r). The expression is a mass relationship, not a prediction of the thickness left between copper layers after pressing.

For an illustrative glass mass of 100 g/m², 50% resin content corresponds to 100 g/m² of resin, while 60% corresponds to 150 g/m². A change from 50 to 60 percentage points therefore increases the resin mass in this example by 50%, not 10%. This is why percentage labels should be interpreted with their definitions rather than used as simple thickness multipliers.

To turn mass into a retained volume, additional data and assumptions would be required, including density and the relevant material state. Cure, flow, local pressure, glass compression and resin movement alter the finished interface. Copper pattern creates different spaces to fill. The online worksheet avoids inventing those missing quantities and uses a supplied pressed contribution instead.

A high-resin construction is not automatically the best choice. The actual design may require a controlled minimum dielectric spacing, stable dimensions, appropriate handling and a qualified process. Too little useful resin in a local region is a different concern from choosing a nominal overall bondline thickness. Resolve the local geometry with the fabricator rather than assuming a larger resin-content number solves every issue.

Evaluate the actual interface and adjacent copper

Look at the copper facing each bondline, not only the board outline. Large cleared regions, heavy copper features and abrupt pattern changes can create different local conditions. Two boards using the same nominal prepreg list may not produce identical local geometry if their retained copper differs. Copper balance and layer placement belong in the manufacturing review.

The PCB lamination process guide explains how the proposed construction becomes a bonded board. This page does not prescribe a generic press temperature, pressure or heating rate for ITEQ materials. Processing guidance must match the exact material revision, equipment and qualified manufacturing route. Copying a schedule from another family can conceal a material-specific requirement.

Storage and handling are also tied to the actual grade and packaging. Ask for the applicable supplier instructions and lot history rather than using one universal shelf-life statement. A nominal material choice can be undermined by uncontrolled exposure before lamination. Record unresolved handling or out-time questions in the review instead of allowing a calculator’s successful arithmetic to close them.

Move from a ply proposal to a released stackup

First, identify the core and each required interlayer spacing. Next, obtain candidate bonding constructions with their glass, resin and pressed-dimension basis. Review the copper pattern and process constraints. Then place the agreed bondline contribution in the physical stack. The ITEQ stackup assignment tool provides a separate place to sum all copper and dielectric entries without confusing a ply list with a complete board.

If the available prepreg differs from the first design assumption, update the electrical geometry before release. A changed dielectric spacing can alter the trace dimensions needed for a controlled impedance target. Do not silently keep an old trace-width table alongside a new bondline construction. The drawing, material record and electrical requirement should describe the same configuration.

As a practical review example, a team proposes changing two thin plies to one thicker ply while preserving nominal total thickness. The arithmetic may look identical, but the glass arrangement, resin distribution, handling and local fill behavior need review. Treat it as a construction change. Record the proposed alternative and the evidence needed to approve it rather than classifying it as a clerical simplification.

The quotation should identify what has been accepted and what remains provisional. An allowance based on one prepreg arrangement should not become a fixed price for every arrangement in the same grade family. If material procurement or additional qualification is needed, ask for that scope explicitly through ITEQ PCB manufacturing.

ITEQ prepreg questions