Wangling F4BM245 PCB 20mil Laminate 2-Layer Immersion Gold No Solder Mask Silkscreen

High-Frequency RF Printed Circuit Board — Product Description & CCL Material Guide

Figure 1. F4BM245 PCB — 20mil 2-Layer Immersion Gold

Executive Summary

Thisarticle presents a comprehensive technical overview of the F4BM245 PCB, a 2-layer rigid high-frequency printed circuit board built onWangling F4BM245 PTFE fiberglass laminate with a 20mil (0.508mm) core thickness and immersion gold surface finish. Engineered for microwave, RF, and radar applications, this board combines a low dielectric constant (Dk 2.45 at 10GHz), ultra-low dissipation factor (0.0012 at 10GHz), and excellent thermal stability to deliver reliable signal integrity at high frequencies. Part I details the PCB construction, stackup, statistics, performance characteristics, and applications. Part II provides an in-depth knowledge guide to the F4BM245 copper-clad laminate (CCL) material, including its complete data sheet, material composition, available configurations, and comparative advantages.

Part I: F4BM245 PCB Product Description

1. Product Introduction

The F4BM245 PCB is a 2-layer rigidhigh-frequency printed circuit board designed for demanding RF and microwave applications. At its core is Wangling F4BM245 laminate, a PTFE (polytetrafluoroethylene) fiberglass cloth-based material with a precisely controlled dielectric constant of 2.45 at 10GHz. The board features a finished thickness of 0.6mm with 1oz (35um) copper on both outer layers and an immersion gold surface finish, providing excellent solderability, corrosion resistance, and flat contact surfaces for high-frequency connectors.

2. PCB Construction Details

The table below summarizes the key construction parameters of the F4BM245 Wangling PCB, defining its physical dimensions, manufacturing capabilities, and finish specifications.

3. PCB Stackup

The stackup below defines the layered structure of this 2-layer rigid PCB, specifying the copper weights and core material thickness that determine its electrical and mechanical properties.

4. PCB Statistics

The table below provides a quantitative breakdown of the board's design complexity, including component count, pad distribution, via count, and net count.

5. Material Performance and High-Frequency Characteristics

The F4BM245 laminate at the heart of this PCB delivers exceptional electrical performance for high-frequency applications. With a dielectric constant of 2.45 at 10GHz and a tight tolerance of +/-0.05, designers can achieve precise impedance control — a critical factor in RF circuit matching. The dissipation factor of 0.0012 at 10GHz (and 0.0017 at 20GHz) ensures minimal signal attenuation, making this material suitable for applications extending into the millimeter-wave range.

Thermal stability is another hallmark of theF4BM245 material. The coefficient of thermal expansion (CTE) is 20 ppm/C on the x-axis and 25 ppm/C on the y-axis (from -55C to 288C), closely matching the CTE of copper (approximately 17 ppm/C), which minimizes thermal stress on plated through-holes and solder joints during temperature cycling. The z-axis CTE of 187 ppm/C is well-controlled for a PTFE-based material. The thermal coefficient of Dk is -120 ppm/C (from -55C to 150C), ensuring that the dielectric constant remains stable across operating temperature ranges — essential for phase-sensitive applications such as phased array antennas and phase shifters.

The material's moisture absorption of <=0.08% is exceptionally low, preventing performance degradation in humid environments. With a long-term operating temperature range of -55C to +260C and UL-94 V0 flammability rating, the F4BM245 PCB suits harsh environmental conditions including aerospace and defense. Thermal conductivity of 0.30 W/(m.K) provides adequate heat dissipation, and volume resistivity of >=6 x 10^6 MOhm.cm ensures excellent insulation between conductive elements.

6. Surface Finish: Immersion Gold

The immersion gold (ENIG) surface finish provides key advantages forhigh-frequency PCBs. A thin gold layer (0.05–0.1um) over a nickel barrier (3–5um) offers excellent corrosion resistance, keeping pads solderable and conductive over the product lifetime. For RF applications, the flat gold surface provides consistent contact resistance for connectors and switches, minimizing signal reflection at the interface. ENIG also supports multiple reflow cycles without degradation, suiting complex assembly processes.

7. Quality Assurance and Manufacturing

This F4B DK2.45 PCB is manufactured to IPC-Class-2 quality standards for dedicated service electronic products, ensuring consistent commercial and industrial performance. Every board undergoes 100% electrical testing prior to shipment, verifying all connections and identifying any opens or shorts. The Gerber RS-274-X artwork format ensures worldwide manufacturing compatibility, with global availability for consistent quality and lead times.

8. Typical Applications

The F4BM245 high frequency PCB is well-suited for a broad range of high-frequency applications, including:

• Microwave, RF, and radar systems

• Phase shifters and phase-sensitive circuits

• Power dividers, directional couplers, and combiners

• Feed networks for antenna systems

• Phased array antennas and base station antennas

• Satellite communications equipment

• Test and measurement instrumentation

9. PCB Conclusion

The F4BM245 2-layer 20mil PCB with immersion gold finish represents a high-performance, reliable solution for RF and microwave circuit designers. Built on Wangling's F4BM245 PTFE fiberglass laminate with a precisely controlled Dk of 2.45 and ultra-low Df of 0.0012 at 10GHz, this board delivers excellent signal integrity and thermal stability. Its 20mil core thickness, 1oz copper weight, and fine-line capability (4/5 mil trace/space) provide design flexibility, while the immersion gold finish ensures durable, high-quality contacts. With IPC-Class-2 manufacturing standards, 100% electrical testing, and global availability, thisWangling F4BMPCB is a dependable choice for engineers developing high-frequency circuits in communications, aerospace, defense, and industrial markets.

Part II: F4BM245 Copper-Clad Laminate (CCL) Material Knowledge

Figure 2. F4BM245 PTFE Fiberglass Copper-Clad Laminate (CCL)

1. Introduction to F4BM245 CCL

Wangling's F4BM245 is a PTFE fiberglass cloth-based copper-clad laminate designed specifically for high-frequency and microwave PCB applications. Manufactured by Taizhou Wangling Insulation Materials Factory, this material is scientifically formulated and strictly pressed using a combination of fiberglass cloth, polytetrafluoroethylene (PTFE) resin, and PTFE film. The F4BM245 represents an advancement over the earlier F4B245 material, offering improved electrical performance through lower dielectric loss, increased insulation resistance, and enhanced stability. It is engineered to be a cost-effective alternative to comparable foreign high-frequency laminates.

2. Material Composition and Manufacturing

The F4BM245 Wangling laminate is composed of PTFE resin reinforced with fiberglass cloth, with copper foil clad on one or both sides. The PTFE resin provides the material's exceptional low-loss dielectric properties, while the fiberglass cloth reinforcement enhances dimensional stability and mechanical strength. By precisely adjusting the ratio between PTFE and fiberglass cloth, Wangling achieves accurate control of the dielectric constant. A higher dielectric constant corresponds to a higher proportion of fiberglass, resulting in better dimensional stability, lower thermal expansion coefficient, improved temperature drift characteristics, and a slight increase in dielectric loss.

The F4BM245 is paired with ED (Electrodeposited) copper foil, making it suitable for applications without PIM (Passive Intermodulation) requirements. For applications requiring excellent PIM performance, the F4BME245 variant is available, which pairs the same dielectric layer with reverse-treated foil (RTF) copper, offering more precise line control and lower conductor loss. Both variants share the same dielectric layer composition, allowing designers to select the appropriate copper foil based on their specific application requirements.

3. Key Features

• Dielectric constant (Dk) of 2.45 at 10GHz with +/-0.05 tolerance for precise impedance control

• Ultra-low dissipation factor of 0.0012 at 10GHz and 0.0017 at 20GHz for minimal signal loss

• Low thermal coefficient of Dk at -120 ppm/C (-55C to 150C) for phase-stable performance

• CTE x-axis: 20 ppm/C, y-axis: 25 ppm/C, z-axis: 187 ppm/C (-55C to 288C)

• Exceptionally low moisture absorption of <=0.08% for humid-environment reliability

• UL-94 V0 flammability rating and long-term operating temperature of -55C to +260C

• Thermal conductivity of 0.30 W/(m.K) in the z-direction for effective heat dissipation

• Radiation resistant and low outgassing, suitable for aerospace and high-altitude applications

• Commercialized, mass-produced, and cost-effective as a domestic alternative to foreign laminates

4. Complete Data Sheet

The following table presents the complete technical data sheet for the F4BM245 laminate, covering electrical, thermal, mechanical, and environmental properties. All values are typical measurements tested per IPC-TM-650 or GB/T 4722-2017 standards unless otherwise noted.

Note: Dielectric constant is measured in the Z-direction using the stripline method per GB/T 12636-1990 or IPC-TM-650 2.5.5.5. All test data are typical measurements intended to assist customers in material selection and do not constitute an express or implied warranty. Customers are responsible for verifying the suitability of Wangling materials in each specific application.

5. Available Copper Foils

F4BM245 is paired with ED (Electrodeposited) copper foil, available in the following standard thicknesses:

• 0.5 oz (0.018 mm)

• 1 oz (0.035 mm)

• 1.5 oz (0.05 mm)

• 2 oz (0.07 mm)

The F4BME245 variant uses reverse-treated RTF (Reverse Treated Foil) copper foil, available in 0.5oz (0.018mm) and 1oz (0.035mm). RTF copper offers a smoother surface, resulting in lower conductor loss at high frequencies, more precise line width control, and excellent PIM performance — making it the preferred choice for high-performance antenna and base station applications.

6. Available Panel Sizes

The F4BM245 laminate is available in the following standard panel sizes:

• 460 x 610 mm

• 500 x 600 mm

• 850 x 1200 mm

• 914 x 1220 mm

• 1000 x 1200 mm

Custom and non-standard sizes are available upon request, including 300x250mm, 350x380mm, 500x500mm, 840x840mm, and 1000x1500mm. Note that for laminate thickness >=4.0mm or <=0.2mm, the maximum panel size is limited to 500 x 610mm due to manufacturing constraints.

7. Available Thicknesses and Tolerances

The F4BM245 laminate is available in a wide range of standard thicknesses, from 0.1mm (dielectric thickness) up to 12.0mm. The table below lists the available thickness options and their corresponding tolerances. The thinnest available dielectric thickness is 0.1mm. Customers should specify whether the quoted thickness includes copper (total thickness) or is dielectric-only when placing orders.

8. Aluminum and Copper Base Variants

The F4BM and F4BME series are also available with aluminum or copper base substrates. These variants feature the dielectric layer with copper foil on one side and an aluminum or copper base on the other, providing electromagnetic shielding or enhanced heat dissipation functions. Model designations include F4BM-AL, F4BME-AL, F4BM-CU, and F4BME-CU. These metal-backed laminates are particularly useful for high-power RF circuits where thermal management is critical, or for applications requiring ground-plane shielding to reduce electromagnetic interference.

9. CCL Conclusion

Wangling's F4BM245 copper-clad laminate is a high-performance, cost-effective PTFE fiberglass material that delivers exceptional electrical and thermal properties for high-frequency PCB applications. With its precisely controlled Dk of 2.45, ultra-low Df of 0.0012 at 10GHz, excellent dimensional stability (CTE x/y of 20/25 ppm/C), and broad operating temperature range (-55C to +260C), it provides a reliable foundation for RF and microwave circuit designs. 

The material's availability in multiple copper foil thicknesses (0.5oz to 2oz ED copper), panel sizes, and thickness options (0.1mm to 12.0mm), along with aluminum/copper base variants and the PIM-optimized F4BME245 RTF copper variant, offers designers significant flexibility. As a domestically produced alternative to comparable foreign high-frequency laminates, F4BM245 combines performance, availability, and cost-effectiveness, making it an excellent choice for engineers and procurement professionals in the high-frequency PCB industry.