2. Case Studies & Specifications Overview

2.1 PCB Case-1: 6-Layer Board with Resin-Filled Vias

Isola 6-layer FR408HR PCB utilizes the full thermal and electrical benefits of the FR408HR system in a robust construction.

Feature	Specification	Technical Note
Layer Count	6 Layers	Optimized for complex routing and power integrity.
Core Material	Isola FR408HR Laminate & Prepreg	High-performance multifunctional resin system with E-glass reinforcement.
Finished Copper Weight	1 oz per layer (35 µm)	Consistent current-carrying capacity across all signal and plane layers.
Total Thickness	1.60 mm	Standard thickness achieved through precise lamination.
Surface Finish	Immersion Gold (ENIG)	Reliable, flat surface for fine-pitch components and wire bonding.
Solder Mask & Legend	Blue Mask, White Legend (Top & Bottom)	Enhanced contrast for Automated Optical Inspection (AOI).
Board Dimensions	79 x 105 mm (per piece)	Compact form factor for integrated assemblies.
Special Via Process	Resin Filling for vias 0.2mm - 0.4mm	Prevents solder wicking, improves planarity, and enhances reliability for HDI designs.

 

2.2 PCB Case-2: 4-Layer Board with L1-L3 Blind Vias

This 4-layer design implements advanced interconnect technology to save space and improve performance.

Feature	Specification	Technical Note
Layer Count	4 Layers	Efficient design for moderate complexity and high-speed needs.
Core Material	Isola FR408HR Laminate & Prepreg	Same high-performance base material ensuring thermal and electrical consistency.
Finished Copper Weight	1 oz per layer (35 µm)	Uniform copper distribution for controlled impedance.
Total Thickness	1.58 mm	Slightly thinner profile for weight or space-constrained applications.
Surface Finish	Immersion Gold (ENIG)	Excellent solderability and corrosion resistance.
Solder Mask & Legend	Blue Mask, White Legend (Top & Bottom)	Compatible with optical positioning and AOI systems.
Board Dimensions	96 x 115 mm (per piece)	Larger area suitable for controller or interface boards.
Special Via Process	Blind Vias (L1 to L3)	Increases routing density, saves space, and improves signal integrity by reducing stub lengths.

 

3. In-Depth: Isola FR408HR Material Technology

 

Isola's FR408HR printed circuit board represents a significant advancement in FR-4 technology, engineered to bridge the gap between thermal robustness and electrical performance for modern multilayer PCB applications.

 

FR408HR 4-Layer 1.6mm Via in Pad HDI PCB with Tg190 is designed for high-reliability applications, delivering excellent stability under extreme thermal and electrical conditions.

 

3.1. Key Material Parameters & Certifications

 

High Thermal Performance: Glass Transition Temperature (Tg) of 190°C and Decomposition Temperature (Td) of 360°C ensure stability during lead-free assembly and high-temperature operation.

 

Optimized Electrical Properties: Dielectric Constant (Dk) of 3.68 and Dissipation Factor (Df) of 0.0092 at specific frequencies provide a 25% improvement in electrical bandwidth over standard FR-4, making it a true mid-loss material.

 

Industry Compliance: Conforms to IPC-4101/98/99/101/126 specifications and holds UL recognition (File Number E41625), guaranteeing material quality and safety.

 

3.2. Enhanced Performance Advantages

 

Superior Reliability: The patented resin system delivers a 30% improvement in Z-axis expansion, drastically reducing the risk of via cracking under thermal stress.

 

Moisture Resistance: Excellent performance during reflow soldering, minimizing the risk of delamination or "popcorning" in humid environments.

 

Manufacturing Compatibility: The material is laser fluorescing and UV blocking, ensuring maximum compatibility and accuracy with Automated Optical Inspection (AOI) systems, optical positioning equipment, and photo-imagable solder mask processes.

 

4. Target Applications

 

The combination of the FR408HR material's properties and the featured PCB designs makes them ideal for demanding sectors:

 

High-Speed Digital Computing: Server motherboards, network switch/router boards, and high-performance computing cards requiring stable Dk/Df.

 

Telecommunications Infrastructure: Baseband units, power amplifiers, and optical network equipment where thermal cycling reliability is critical.

 

Industrial & Automotive Electronics: Control units, sensor modules, and power converters operating in harsh environments.

 

Advanced Consumer Electronics: High-end gaming systems, VR/AR hardware, and other devices where signal integrity and miniaturization (via HDI techniques like blind vias) are key.

 

Typical Values Table

Property		Typical Value	Units	Test Method
			Metric (English)	IPC-TM-650 (or as noted)
Glass Transition Temperature (Tg) by DSC		190	°C	2.4.25C
Decomposition Temperature (Td) by TGA @ 5% weight loss		360	°C	2.4.24.6
Time to Delaminate by TMA (Copper removed)	A. T260 B. T288	60 >30	Minutes	2.4.24.1
Z-Axis CTE	A. Pre-Tg B. Post-Tg C. 50 to 260°C, (Total Expansion)	55 230 2.8	ppm/°C ppm/°C %	2.4.24C
X/Y-Axis CTE	Pre-Tg	16	ppm/°C	2.4.24C
Thermal Conductivity		0.4	W/m·K	ASTM E1952
Thermal Stress 10 sec @ 288ºC (550.4ºF)	A. Unetched B. Etched	Pass	Pass Visual	2.4.13.1
Dk, Permittivity	A. @ 100 MHz B. @ 1 GHz C. @ 2 GHz D. @ 5 GHz E. @ 10 GHz	3.72 3.69 3.68 3.64 3.65	—	2.5.5.3 2.5.5.9 Bereskin Stripline Bereskin Stripline Bereskin Stripline
Df, Loss Tangent	A. @ 100 MHz B. @ 1 GHz C. @ 2 GHz D. @ 5 GHz E. @ 10 GHz	0.0072 0.0091 0.0092 0.0098 0.0095	—	2.5.5.3 2.5.5.9 Bereskin Stripline Bereskin Stripline Bereskin Stripline
Volume Resistivity	A. After moisture resistance B. At elevated temperature	4.4 x 107 9.4 x 107	M阝-cm	2.5.17.1
Surface Resistivity	A. After moisture resistance B. At elevated temperature	2.6 x 106 2.1 x 108	M阝	2.5.17.1
Dielectric Breakdown		>50	kV	2.5.6B
Arc Resistance		137	Seconds	2.5.1B
Electric Strength (Laminate & laminated prepreg)		70 (1741)	kV/mm (V/mil)	2.5.6.2A
Comparative Tracking Index (CTI)		2 (250-399)	Class (Volts)	UL 746A ASTM D3638
Peel Strength	A. Low profile copper foil and very low profile copper foil all copper foil >17 阝m [0.669 mil] B. Standard profile copper 1. After thermal stress 2. After process solutions	1.14 (6.5) 0.96 (5.5) 0.90 (5.1)	N/mm (lb/inch)	2.4.8C 2.4.8.2A 2.4.8.3
Flexural Strength	A. Length direction B. Cross direction	72.5 58.0	ksi	2.4.4B
Tensile Strength	A. Length direction B. Cross direction	54.5 38.7	ksi	ASTM D3039
Young's Modulus	A. Length direction B. Cross direction	3695 3315	ksi	ASTM D790-15e2
Poisson's Ratio	A. Length direction B. Cross direction	0.137 0.133	—	ASTM D3039
Moisture Absorption		0.061	%	2.6.2.1A
Flammability (Laminate & laminated prepreg)		V-0	Rating	UL 94
Relative Thermal Index (RTI)		130	°C	UL 796

 

 

5. Conclusion

 

These 6-layer and 4-layer PCBs, built on the Isola FR408HR substrates, provide a robust and reliable foundation for advanced electronic systems. By leveraging the material's enhanced thermal resistance, improved electrical bandwidth, and superior moisture performance, designers can achieve greater reliability and signal integrity in their products. The implementation of specialized via processes—resin filling for micro-vias and blind vias—further demonstrates the capability to support high-density interconnect (HDI) and miniaturized designs, making these solutions ready for the challenges of next-generation electronics.

 

 

Founded in 2003, Shenzhen Bicheng Electronics Technology Co., Ltd is an established high frequency PCB supplier and exporter in Shenzhen, China, serving customers worldwide.

 

We are devoted to delivering high-frequency PCB products and solutions of the highest quality, along with customized service. Get in touch with us to start your project !

Visit https://www.bicheng-enterprise.com to learn more.