Prepreg: Thickness 0.05-0.2 mm, Flow 15-30%, Dk 3.8-4.2

Component Specifications

Definition

Prepreg (pre-impregnated composite fibers) is a semi-cured thermosetting resin matrix reinforced with woven or non-woven fiberglass fabric. In multilayer PCB manufacturing, it serves as the dielectric insulating layer between copper-clad laminates, bonding them together during lamination under heat and pressure. The material undergoes partial curing (B-stage) during production, allowing it to flow and fully cure (C-stage) during PCB fabrication to form a solid, insulating bond.

Working Principle

Prepreg works by utilizing a partially cured thermosetting resin (typically epoxy) impregnated into fiberglass reinforcement. During PCB lamination, heat (typically 180-200°C) and pressure (200-400 psi) cause the resin to flow, wetting adjacent copper layers and core materials, then fully polymerize into a rigid, insulating dielectric layer that bonds the PCB layers together while providing electrical insulation and mechanical stability.

Materials

Fiberglass fabric (E-glass, NE-glass, or low-loss glass) impregnated with thermosetting resin (epoxy, polyimide, BT, or cyanate ester), with flame retardant additives (brominated or halogen-free) to meet UL94 V-0 standards. Typical resin content: 40-60%, glass transition temperature (Tg): 130-180°C, dielectric constant (Dk): 3.5-4.5 at 1 GHz.

Technical Parameters

Parameter	Typical range	Notes & selection driver
Df	0.015-0.025 at 1 GHz
Dk	3.8-4.2
Tg	140-170°C
CTE	40-60 ppm/°C
Flow	15-30%
Gel Time	60-120 seconds at 170°C
Thickness	0.05-0.2 mm
Resin Content	45-55%

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Standards

IPC-4101, IPC-4103, ISO 9001, UL 94

Parent Products

This component is used in the following industrial products

Multilayer PCB

A printed circuit board consisting of multiple conductive copper layers separated by insulating dielectric materials, laminated together to form a single integrated board.

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Engineering Analysis

Risks & Mitigation

Moisture absorption causing delamination
Incomplete resin flow during lamination
Thermal degradation during multiple lamination cycles
Inconsistent dielectric properties

FMEA Triads

Trigger: Improper storage conditions leading to moisture absorption
Failure: Void formation and delamination during lamination
Mitigation: Implement controlled storage (-5°C to 5°C) with moisture barrier packaging and monitor shelf life

Trigger: Incorrect lamination temperature or pressure profiles
Failure: Incomplete resin flow and poor interlayer bonding
Mitigation: Validate lamination profiles through TMA/DSC testing and implement SPC for process control

Trigger: Resin chemistry variations between batches
Failure: Inconsistent dielectric properties and impedance control
Mitigation: Implement incoming material testing for Dk/Df and establish supplier quality agreements

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance

Thickness tolerance: ±10%, Dielectric constant tolerance: ±0.2

Test Method

IPC-TM-650 test methods for dielectric properties, thermal analysis (TMA/DSC), and mechanical testing per IPC-4101

Procurement Evaluation Criteria

A practical evidence checklist for RFQ preparation and supplier evaluation.

Technical documentation

Request current drawings, revision history, and a signed specification sheet.

Manufacturing capability

Verify equipment lists, process limits, capacity, and representative production evidence.

Inspection readiness

Confirm test methods, calibrated equipment, sampling plans, and traceable reports.

Supplier transparency

Check the legal entity, factory address, ownership, certifications, and direct contacts.

CNFX does not score or rank suppliers. Buyers must verify all claims and documents with the legal manufacturer before ordering.

Manufacturers of Prepreg

Manufacturer profiles associated with Prepreg.

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Compiled and source-reviewed by the CNFX editorial team. Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review

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Frequently Asked Questions

What is the difference between prepreg and core material in PCBs?

Core material is fully cured copper-clad laminate with copper on both sides, while prepreg is partially cured dielectric material without copper, used to bond cores together during lamination.

How does prepreg thickness affect PCB performance?

Prepreg thickness controls dielectric spacing between copper layers, affecting impedance control, signal integrity, and thermal management in high-frequency and high-speed PCB designs.

What are the storage requirements for prepreg?

Prepreg must be stored at -5°C to 5°C in moisture-barrier packaging with desiccant, with limited shelf life (typically 3-6 months) to prevent premature curing and moisture absorption.

Data Basis

Editorial classification, named public sources where available, and source-reviewed manufacturer records. See the editorial policy.

Preliminary Technical Classification

This page supports structured research, RFQ preparation, and supplier evaluation. It does not replace buyer-led supplier qualification, standards review, or technical approval.

Prepreg