1. What is PCB CTI Value?

Comparative Tracking Index (CTI) is a vital electrical property of PCB materials that measures their resistance to tracking—a phenomenon where carbonized, conductive paths form across an insulating surface due to electrical stress and moisture. The higher the CTI value, the better the insulation performance under harsh conditions such as high voltage and humidity.

A high CTI value reduces the risk of arcing, short circuits, and board failure, making it crucial for safety-critical applications like automotive electronics, medical devices, and industrial control systems.

PCB CTI

2. PCB CTI Classification and Material Grades

CTI values are categorized into different classes based on IEC 60112 standards. The classification is as follows:

Materials in CTI Class 0 and 1 are highly recommended for mission-critical and high-voltage environments, where electrical tracking could result in catastrophic failure.

3. CTI Ratings of Common PCB Materials

Different PCB base materials exhibit varying CTI values based on their composition and structure. Here’s a breakdown:

For high-voltage and high-reliability applications, FR4-High CTI, Polyimide, and Ceramic boards should be your go-to materials.

4. CTI Testing: IEC 60112 Method Explained

The IEC 60112 standard defines the method for determining CTI:

● Sample Preparation: Material is cut and conditioned to test size.
● Electrolyte Application: A solution (commonly ammonium chloride) is dripped at regular intervals.
● Voltage Application: Step voltage is applied across two electrodes.
● Failure Monitoring: The CTI is the highest voltage at which no electrical tracking is observed.

In addition to IEC 60112, other supporting tests include:

5. Why CTI Matters in PCB Design

Selecting the right CTI class is not just about compliance—it’s about preventing failure in the field. Here’s why it’s essential:

● Reduces Arcing & Short Circuits: Prevents unintentional current paths.
● Improves Longevity: Better resistance to environmental stress.
● Enhances Safety: Meets UL, IPC, and IEC standards.
● Boosts Product Quality: Lower field failure rates and better brand reputation.

6. Industry Applications Based on CTI Requirements

Every industry has its own insulation performance demands. Choosing the right CTI material ensures optimal performance and safety.

7. The SQPCB Advantage in High CTI PCB Manufacturing process

SQPCB leverages advanced manufacturing equipment to deliver top-tier PCBs with high CTI ratings. Our production capabilities include:

● LDI Inline Exposure Machines for both circuit and solder mask imaging
● CCD Automatic Inkjet Printers for precision silkscreening
● Self-owned Lamination, HASL, and ENIG lines for controlled quality and fast lead times

Why does this matter?
These technologies eliminate common errors associated with traditional film-based exposure—such as shrinkage, misalignment, scratches, and rework—resulting in higher yields, better solder mask gloss, and improved board integrity.

8. Conclusion: Choosing the Right CTI = Safer, Stronger PCB

CTI is more than just a number—it’s your insurance policy against electrical tracking, failure, and safety violations. Whether you’re designing for the automotive sector or developing next-gen industrial systems, selecting high-CTI materials is essential.

For your next project, trust SQPCB, a reliable PCB supplier with:

LDI inline imaging for precision

In-house plating and pressing for consistent quality

Capability to handle complex and urgent orders

FAQs About PCB CTI Value

Q1: What does CTI mean in PCB manufacturing?
CTI stands for Comparative Tracking Index, which indicates how resistant a PCB material is to forming conductive tracks under high voltage and humid conditions.

Q2: What CTI rating is best for automotive applications?
CTI values of 400V–599V (Class 1) are ideal, particularly using high-CTI FR4 or CEM-3 to withstand the vibration and temperature variations in vehicles.

Q3: How is CTI different from dielectric strength?
While CTI measures long-term resistance to electrical tracking, dielectric strength measures the maximum voltage a material can withstand before breaking down instantly.

Q4: Can low-CTI materials be used in high-voltage systems?
No. Low-CTI materials are more prone to arc tracking and should be avoided in high-voltage environments. Always select CTI ≥ 600 for such applications.

Q5: How does SQPCB ensure CTI quality control?
SQPCB uses inline LDI exposure machines and automated printing to enhance precision, minimize human error, and maintain high-quality CTI-compliant boards. In-house lamination and plating ensure full process control.