Comparison of Paper-based and fiberglass-based insulation laminates and Copper Clad Laminates ( CCL )

Technical Comparison of Paper-Based, Fabric-Based and Fiberglass-Based Insulation Laminates and Copper Clad Laminates (CCL) 
(From the Perspective of Resin Formulation and Impregnation Process) 
This document is prepared from the perspective of an insulation laminate and copper clad laminate (CCL) resin formulation and impregnation process specialist.
The comparison focuses on resin systems, raw materials, and processing mechanisms, explaining the fundamental differences and classifications of paper-based, fabric-based, and fiberglass-based insulation materials and CCLs.
The discussion emphasizes engineering principles and process fundamentals, rather than market-oriented descriptions.
1, Fundamental Differences from a System Perspective:
The essence of insulation laminates and CCLs is a composite system composed of reinforcing material and a thermosetting resin system.
The primary differences among paper-based, fabric-based, and fiberglass-based materials do not originate from the “laminate” itself, but from the combination of: 
Reinforcement structure × Resin chemistry × Impregnation and curing mechanism

II. Fundamental Differences from the Resin System Perspective (Core Factor)
1, Paper-Based Insulation Laminates
(1) Typical resin system
- Phenolic resin (PF) — dominant and almost exclusive
- Minor modifications:
- Urea-modified phenolic
- Alcohol-soluble or water-soluble phenolic
(2) Resin formulation characteristics
- Base-catalyzed condensation polymerization
- Broad molecular-weight tolerance
- Typical solid content: 45–55%
- Low viscosity to ensure full paper impregnation
(3) Resin–paper interaction mechanism
- Resin does not merely coat the surface; it fully penetrates and fills the fiber network
- Phenolic resin infiltrates cellulose capillary structures
- After curing, a quasi-homogeneous composite structure is formed
(4) Engineering conclusion
- Paper-based laminates impose low chemical performance requirements on the resin, but extremely high requirements on impregnation capability.
2. Fabric-Based Insulation Laminates (Cotton / Fabric)
(1) Typical resin systems
- Phenolic resin (PF) — mainstream
- Epoxy resin (EP) — mid- to high-grade products
- PF/EP hybrid systems — limited applications
(2) Resin formulation and processing features
- Compared with paper-based systems:
- Higher solid content (typically 50–60%)
- Higher viscosity
- Greater emphasis on rheological stability
The resin must balance:
-  Penetration into fabric pores
- Adequate resin retention on the fabric surface
(3) Reinforcement structure characteristics
- Fabric is a woven structure
- Contains:
-- Warp and weft interlacing pores
-- Inter-bundle voids
- Resin must both penetrate and remain
(4) Engineering nature
Fabric-based laminates follow a structural-component design philosophy, where the resin functions not only as an insulating medium but also as a load-bearing bonding phase.

3. Fiberglass-Based Materials
This category represents the core material system of electronic-grade CCLs.
3.1 Main resin system classifications

3.2  Fundamental shift in resin formulation
Resin formulation is no longer a simple “resin + curing agent” process, but a reaction-system engineering problem, involving:
- Molecular-weight distribution
- Reaction activity window
- Controlled B-stage behavior
3.3 Critical resin parameters
- Gelling time
- B-stage tack window
- Exothermic reaction rate
- Volatile content control
3.4 Resin–fiberglass interface considerations
- Fiberglass is an inorganic material
- Effective bonding relies on:
-- Silane coupling agents
-- Surface treatment systems
- Chemical affinity between resin and fiberglass is critical
In fiberglass systems, resin is not merely a filler; it is the key determinant of dielectric performance and long-term reliability.
1- Differences from the Impregnation Process Perspective
2- Comparison of impregnation methods

2. Differences in prepreg (PP) state
- Paper-based
-- No true “prepreg” concept
-- Direct lamination after impregnation
- Fabric-based
-- Semi-cured sheets
-- Relatively wide process tolerance
- Fiberglass-based
-- Prepreg is an independent engineered product
-- Resin flow, gel time, and surface condition must be quantitatively controlled
IV. Engineering Logic Behind Final Product Classification
4.1 Insulation laminates (without copper)
4.2 Copper-clad laminates (CCL)


V. One-Sentence Engineering Summary (From a Resin Perspective)
- Paper-based systems
Resin determines whether complete impregnation is achievable
- Fabric-based systems
Resin determines mechanical strength and structural stability
- Fiberglass-based systems / CCL
Resin determines dielectric performance, reliability, and product grade