Cracking the Code:

The Essential Tech Behind Copper Foil in High TG Copper Clad Laminates

In the fast-paced world of electronics manufacturing, staying ahead of the curve is crucial. Today, we’re diving deep into a topic that’s on the minds of many industry professionals: the technology behind copper foil in high TG copper clad laminates. If you’ve ever grappled with issues related to copper foil performance in high TG boards, this blog post is your ultimate guide to understanding, troubleshooting, and optimizing.

Unraveling the Mystery of High TG Boards

Before we explore the intricacies of copper foil technology, let’s start with the basics of high TG (Glass Transition Temperature) boards. In the realm of printed circuit boards (PCBs), the ability to withstand heat is non-negotiable. The TG point is the temperature at which a PCB transitions from a rigid “glass state” to a more malleable “rubber state.” It’s a critical factor that determines a board’s dimensional stability and overall performance under heat.

A higher TG value indicates superior heat resistance. As the electronics industry evolves towards high-functionality and multi-layered designs, high TG PCBs have become indispensable. Technologies like SMT (Surface Mount Technology) and CMT (Chip Mount Technology) rely on the high heat resistance of these boards to support small apertures, fine circuits，and thin profiles. Compared to standard FR-4, high TG FR-4 boards excel in mechanical strength, dimensional stability, and resistance to moisture, chemicals, and thermal expansion—especially when exposed to moisture and heat.

The Pitfalls of Mixing TG Values

One common question in the industry is: Why can’t we mix standard TG and high TG materials? The answer lies in the fundamental differences in their material properties. Mixing low TG and high TG boards during lamination can lead to disastrous results. Using a low TG board in a high TG lamination process results in insufficient curing time, potentially causing the board to delaminate. Conversely, applying high TG lamination parameters to a low TG board can lead to excessive resin flow and a thinner board.

Typically, boards with a TG of 130°C or higher are considered high TG, with values often exceeding 170°C for top-tier products. This significant temperature difference makes it essential to keep TG values consistent during manufacturing.

The Copper Foil Conundrum in High TG Boards

Now, let’s turn our attention to the star of the show: copper foil. When used in high TG copper clad laminates, copper foil faces a unique challenge: a significant drop in peel strength. For instance, a 70-micron copper foil that boasts a peel strength of over 2.5 N/mm when laminated with a TG 140 material system sees this value plummet to around 1.8 N/mm with a TG 150 system and 1.5 N/mm with a TG 170 system. But why does this happen, and how can we address it?

Key Differences Between Standard and High TG Copper Foil

1.Alloy Layer Composition: One of the primary distinctions between standard and high TG copper foil lies in the alloy layer on the rough side. High TG copper foil uses a multi-element alloy layer to prevent direct contact between copper and zinc, inhibiting the formation of unwanted copper-zinc compounds during high-temperature lamination and repeated thermal cycling.

2.Roughened Layer Structure: High TG copper foil features a more robust roughened layer with a larger surface area. This enhanced structure improves adhesion between the copper foil and the laminate, crucial for maintaining peel strength.

3.Silane Coupling Agent Selection: The choice of silane coupling agent is pivotal. The conventional KH560 agent tends to degrade under high-temperature lamination and repeated thermal shocks. Opting for alternative silanes and optimizing their concentration is key to preventing peel strength degradation.ile on the rough surface. This isn’t just about uniformity; the peaks must be distinct, avoiding a “hilly” appearance. Achieving this requires meticulous adjustment of additives and manufacturing processes.

4.Consistent Foil Peak Profile: High TG copper foil requires a uniform and precisely controlled peak profile on the rough surface. This isn’t just about uniformity; the peaks must be distinct, avoiding a “hilly” appearance. Achieving this requires meticulous adjustment of additives and manufacturing processes.

Practical Solutions for Industry Professionals​

Navigating the challenges of copper foil in high TG boards may seem daunting, but with the right knowledge, you can overcome these hurdles. By focusing on the key differences outlined above—alloy composition, roughened layer structure, silane selection, and foil peak profile—manufacturers can significantly improve the performance of copper foil in high TG applications.​

As high TG copper clad laminates become the new norm, it’s essential for copper foil manufacturers and PCB fabricators to collaborate closely. By implementing these technical insights, you can ensure that your products meet the stringent demands of modern electronics, giving you a competitive edge in the market.​

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