1. When the temperature of a high Tg PCB reaches a certain threshold, the substrate transitions from the “glass state” to the “rubber state.”

2. This temperature is referred to as the glass transition temperature (Tg) of the board.

3. Specifically, Tg represents the maximum temperature (°C) at which the base material retains its rigidity.

4. In contrast, standard PCB substrate materials will continue to soften, deform, and melt at elevated temperatures.

5. Concurrently, there will be a significant decline in both mechanical and electrical properties.

6. This degradation can negatively impact the product’s lifespan.

7. Typically, Tg for standard boards is above 130 degrees Celsius; high Tg is generally above 170 degrees Celsius, while medium Tg exceeds 150 degrees Celsius.

8. Boards with a Tg of ≥ 170 degrees Celsius are categorized as high Tg printed circuit boards.

9. An increase in substrate Tg enhances the board’s heat resistance, as well as its moisture resistance, chemical resistance, and overall stability.

10. The higher the Tg value, the greater the temperature resistance of the board.

11. This is particularly important in lead-free processes, where high Tg materials are increasingly utilized.

12. Thus, high Tg denotes high heat resistance, which is crucial in the fast-evolving electronics industry.

1. Especially in electronic products like computers, the demand for high functionality and multilayer designs necessitates PCB substrate materials with enhanced heat resistance as a prerequisite.

2. The advent and advancement of high-density mounting technologies, exemplified by SMT and CMT, have increasingly tied the performance of PCBs to the support of high-heat-resistant substrates, particularly in terms of smaller apertures, fine wiring, and reduced thickness.

3. Consequently, the distinction between standard FR-4 and high Tg materials becomes clear: at elevated temperatures—especially post moisture absorption—the mechanical strength, dimensional stability, adhesion, water absorption, thermal decomposition, and thermal expansion of the materials vary. High Tg products outperform standard PCB substrate materials in these respects.

4. Current knowledge and standards regarding PCBs reveal several types of copper-clad laminates widely utilized in our country, characterized as follows: the types of copper-clad laminates, their properties, and classification methods.

5. Generally, based on different reinforcing materials, these laminates can be categorized into five groups: paper-based, glass fiber cloth-based, composite (CEM series), multilayer laminate, and special material bases (ceramic, metal core, etc.).

6. When classified according to the types of resin adhesives used, common paper-based CCL includes: phenolic resin (XPc, XxxPC, FR-1, FR-2, etc.), epoxy resin (FE-3), polyester resin, and others.

7. The prevalent glass fiber cloth-based CCL typically features epoxy resin (FR-4, FR-5), which is currently the most commonly used type in this category.

8. Additionally, there are other special resins that incorporate glass fiber cloth, polyamide fiber, and non-woven fabric as additives, including bismaleimide modified triazine resin (BT), polyimide resin (PI), diphenylene ether resin (PPO), maleic anhydride imine-styrene resin (MS), polycyanate resin, and polyolefin resin.

9. Based on flame-retardant performance classification, CCL can be divided into flame-retardant types (UL94-VO, UL94-V1) and non-flame-retardant types (UL94-HB).

10. In recent years, as environmental protection concerns have gained prominence, a new category of non-brominated, flame-retardant CCL has emerged, referred to as “green flame-retardant CCL.”

11. With the rapid advancement of electronic product technology, performance demands for CCL have intensified. Thus, CCL is categorized by performance into general, low dielectric constant, high heat resistance (with a normal board temperature exceeding 150 degrees Celsius), low thermal expansion coefficient (typically used for packaging substrates), and other types.

12. As electronic technology evolves, new requirements for PCB substrate materials continue to emerge, driving the ongoing development of copper-clad laminate standards.