8-Layer 10oz Heavy Copper TU-865 Substrate PCB With ENIG Blind &Buried Via

8-Layer 10oz Heavy CopperTU-865 Substrate PCB With ENIG Blind &Buried Via

Overview

This 8-layer 10oz heavy-copper printed circuit board is engineered for high-power, high-reliability, and harsh-environment applications including automotive power control, industrial inverters, server power modules, telecommunication base stations, and high-current equipment. Built on Panasonic TU-865 halogen-free high-Tg laminate, this multilayer PCB combines ultra-thick copper conductivity, multilayer structural stability, blind/buried via routing, and robust material performance to support sustained high current, extreme thermal cycling, lead-free assembly, and long-term operation under high temperature and high humidity.

With a finished board thickness of 4.5mm and 10oz (350μm) copper on every layer, the design prioritizes current-carrying capacity, thermal dissipation, mechanical strength, and CAF resistance. Compliance with IPC-4101E /127, /128, /130 and UL94 V-0 flammability ensures global qualification for safety-critical and high-reliability electronics. This 8-Layer PCB delivers premium performance in power density, thermal management, and environmental durability for demanding industrial and automotive use cases.

PCB Construction Details

The following table summarizes the key structural and manufacturing specifications of the 8-layer 10oz heavy-copper PCB. These parameters define mechanical form, layer structure, copper thickness, via system, surface treatment, and quality assurance.

PCB Stackup Design

The 8-layer PCB stackup is balanced for symmetry, thermal distribution, and impedance stability. Symmetric layer arrangement minimizes warpage after lamination and soldering. Thick dielectric spacing supports high voltage isolation and low CAF risk.

Mechanical and Thermal Performance

With 10oz heavy copper and 4.5mm overall thickness, this 8-Layer TU-865 PCB provides exceptional mechanical rigidity and thermal robustness. Thick copper reduces DC resistance, boosts current-carrying capacity, and accelerates heat spreading across the board. The TU-865 substrate features high Tg (DSC 200°C, TMA 185°C), low CTE (X-axis 11–15 ppm/°C, Y-axis 11–15 ppm/°C, Z-axis expansion <1.8%), and outstanding thermal stability. It withstands 288°C solder float for more than 60 seconds without delamination or blistering. T260, T288, and T300 resistances exceed 60 minutes, 60 minutes, and 30 minutes respectively, ensuring reliable performance during multiple lead-free reflow cycles and prolonged high-temperature operation. Maximum operating temperature reaches 130°C, suitable for automotive engine compartments and industrial environments. Low water absorption (0.13%) preserves insulation resistance and prevents performance degradation in high-humidity environments.

Electrical Properties

TU-865 provides stable electrical performance across frequency and temperature. At 1GHz, dielectric constant is approximately 4.3–4.6; dissipation factor is around 0.010–0.013. At 10GHz, loss tangent remains controlled near 0.014, placing the material in the mid-loss category ideal for mixed analog/digital and power-radio systems. Volume resistivity exceeds 10¹⁰MΩ·cm; surface resistivity exceeds 10⁸MΩ. Dielectric strength is greater than 40 kV/mm, and dielectric breakdown exceeds 50kV, supporting high-voltage isolation and safety in power circuits. Excellent anti-CAF performance suppresses conductive anode filament growth, greatly improving long-term reliability under high humidity and voltage bias.

Via Structure and Reliability

The heavy copper PCB integrates blind vias, buried vias, and half-holes to achieve high routing density while preserving structural integrity in a thick 4.5mm core. All through-holes are filled with conductive copper paste to improve thermal conduction, enhance via strength, prevent solder wicking, and protect inner layers from thermal stress. Filled vias also improve planarity for surface-mount assembly and boost thermal fatigue resistance under rapid temperature changes. This via system is optimized for heavy-copper processing and supports reliable interlayer connection under high current and thermal load.

Surface Treatment and Appearance

Immersion Gold surface finish provides excellent flatness, solderability, and wire-bond capability. It protects copper circuits from oxidation and ensures reliable soldering even after long-term storage. Green solder mask offers insulation, protection against dust and moisture, and resistance to chemical cleaning. White silkscreen ensures clear component marking, polarity indication, and test point identification. The combination delivers excellent visual inspection compatibility and supports AOI verification.

Application Fields

This 8-layer heavy-copper PCB is intended for high-power and high-reliability scenarios:

• Automotive: ECU, motor control, battery management, inverter, on-board charger
• Industrial: high-power inverter, welding equipment, power supply
• Servers & Telecom: base station power, server voltage regulation, high-current backplanes
• Harsh environment: high temperature, high humidity, repeated thermal cycling

TU-865 Copper Clad Laminate (CCL) Technical Knowledge

Material Introduction

TU-865 is a halogen-free high-Tg epoxy resin-based copper clad laminate reinforced with E-glass fabric. It is formulated with phosphorus-nitrogen flame retardant to achieve UL94 V-0 without halogens, antimony, or red phosphorus. Developed for harsh environments and high-reliability electronics, it combines excellent thermal performance, electrical stability, chemical resistance, dimensional stability, and CAF resistance. TU-865P is the matching prepreg for multilayer PCB fabrication.

Key Advantages

• Halogen-free, environmentally safe
• High Tg for thermal stability
• Mid-loss electrical performance
• Low CTE for reduced thermal stress
• Excellent moisture resistance
• Compatible with lead-free assembly
• Strong anti-CAF performance
• UV-blocking property supports AOI inspection

Industry Approvals

• IPC-4101E Type: /127, /128, /130
• IPC-4101E /130 QPL Certified
• UL ANSI Grade: FR-4.1
• UL File No.: E189572
• Flammability: UL94 V-0
• Max Operating Temperature: 130°C

Standard Specifications

• Thickness: 0.05mm to 1.58mm
• Copper foil: 1/3oz to 12oz
• Glass styles: 106, 1080, 2113, 2116, 1506, 7628
• Available forms: sheets, panels, prepreg rolls

Typical Properties of TU-865 Laminate

Material Summary

TU-865 is a high-performance halogen-free CCL designed for high-reliability PCBs exposed to extreme thermal, chemical, and humidity conditions. Its balanced thermal, electrical, and mechanical properties make it the preferred choice for automotive, server, telecom, and harsh-environment applications. When used in 10oz heavy-copper designs, it provides exceptional current capacity, thermal dissipation, and long-term reliability.