ICT（線路內測試）

ICT（線路內測試） is a widely used electrical testing method in PCB 組裝 that verifies the performance and integrity of individual components and circuits on a fully assembled PCB. It is commonly applied after SMT 組裝 to ensure that each component is correctly placed, soldered, and functioning as intended.

ICT is one of the most effective ways to detect manufacturing defects early and ensure high product quality in mass production.

What Does ICT Test?

ICT focuses on checking the electrical behavior of each component on the board. It can detect:

• Open circuits (broken connections)
• Short circuits (unwanted connections)
• Incorrect component values (e.g., wrong resistor or capacitor)
• 缺失的元件
• Faulty or damaged components
• Polarity errors (e.g., diodes, capacitors)

👉 ICT ensures that the PCB Assembly is electrically correct before functional testing.

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How ICT Works

ICT uses a bed-of-nails fixture to make contact with test points on the PCB:

1. The assembled PCB is placed on a fixture
2. Spring-loaded pins contact designated test points
3. Electrical signals are applied and measured
4. Results are compared with expected values

This allows fast and accurate testing of each circuit node.

Types of ICT Methods

Bed-of-Nails ICT (Fixture-Based)

• Uses a custom test fixture
• High-speed testing for mass production
• High upfront cost (fixture design)

Flying Probe Testing

• Uses movable probes instead of a fixture
• No need for dedicated tooling
• Slower but more flexible
• Ideal for prototypes and small batches

👉 Flying probe is often used when ICT fixtures are not cost-effective.

Advantages of ICT

• High fault coverage (detects most electrical issues)
• Fast testing speed in production
• Accurate and repeatable results
• Reduces defective products reaching customers
• Improves overall PCB 組裝 quality

Limitations of ICT

• Requires test points in PCB design
• High initial fixture cost
• Cannot fully verify real-world functionality
• Less effective for very high-density boards without proper design

ICT vs Functional Testing (FCT)

👉 ICT and functional testing are often used together in SMT 組裝 項目。.

When is ICT Used?

ICT is most suitable for:

• Medium to high-volume production
• Products requiring high reliability
• Complex PCB Assembly designs
• Industries like automotive, medical, and industrial electronics

Design Considerations for ICT

To enable effective ICT testing:

• Add sufficient test points
• Ensure proper spacing for probes
• Avoid obstructed access
• Follow DFT (Design for Testing) guidelines

Good design significantly improves ICT efficiency.

Role of ICT in PCB Assembly Process

In a typical PCB 組裝 workflow:

• Performed after SMT Assembly and soldering
• Identifies manufacturing defects early
• Reduces rework and repair costs
• Improves yield and production efficiency

總結

ICT (In-Circuit Testing) is a powerful and essential testing method in PCB 組裝, providing fast and accurate verification of electrical performance at the component level. When combined with SMT 組裝 and functional testing, ICT helps ensure high-quality, reliable electronic products.

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