4-layer TU-872 SLK Sp HDI PCB High Tg Material Featuring Blind Vias and Buried Vias with Immersion Gold

Printed Circuit Boards are custom-made products; the images and specifications provided are for reference only.

Brief Introduction

This 4-layer TU-872 SLK Sp PCB utilizes low Dk/Df FR-4 material with 1oz copper on each layer, finished with immersion gold surface treatment and green solder mask. TU-872 PCB has a final thickness of 1.6mm (±10%) and is arrayed in a panel of 16 units. It incorporates HDI technology featuring blind vias from the top layer to inner layer 1 and buried vias between inner layers 1 and 2. Manufactured to IPC-Class-2 standards, each board is vacuum-sealed for secure shipment.

PCB Specifications

Typical Applications

1. Radio Frequency

2. Backpanel, High performance computing

3. Line cards, Storage

4. Servers, Telecom, Base station

5. Office Routers

High Tg PCB

The thermal performance of a resin system is characterized by its glass transition temperature (Tg), which is always expressed in °C. The most commonly referenced thermal property is thermal expansion. When measuring thermal expansion against temperature, an expansion curve (as shown in the following figure) can be obtained. The Tg value is determined by the intersection of the tangent lines of the flat and steep segments of this curve.

Below the glass transition temperature, epoxy resin exhibits a rigid, glass-like state. Once the temperature exceeds Tg, the resin transitions to a soft, rubbery state.

Tg of Common Epoxy Resins and Soldering Risks

For the most widely used epoxy resins (FR-4 grade), the glass transition temperature typically ranges from 115°C to 130°C. This means the Tg is easily exceeded during PCB soldering processes.

When the board temperature surpasses Tg, two key changes occur:

The PCB expands in the Z-axis direction, creating stress on the copper layer of the hole walls.

The thermal expansion rate of epoxy resin becomes 15 to 20 times that of copper, significantly increasing the risk of plated-through hole (PTH) wall cracking. The more resin surrounding the hole wall, the higher this risk.

In contrast, below Tg, the expansion rate ratio between epoxy resin and copper is only 3:1, making the risk of cracking negligible.

Definition of High Tg PCB

General PCB: Tg ≥ 130°C

Medium Tg PCB: Tg ≥ 150°C

High Tg PCB: Tg ≥ 170°C

PCBs with a glass transition temperature of 170°C or higher are generally defined as high Tg PCBs.

Partial High Tg Material in House