Comprehensive In-Circuit Testing (ICT) Guide

As the number of PCB layers increases, manufacturing costs correspondingly rise. According to statistics, the manufacturing cost may increase by 30-40% when moving from a 2-layer PCB to a 4-layer PCB. This price increase primarily stems from three aspects: raw materials, processes, and faults. Therefore, adopting necessary testing methods not only enhances customer trust in the brand but also helps save costs and time wasted on rework. Among various testing methods, ICT is considered the most effective measure for verifying electronic components, circuit connections, and electrical performance on a circuit board. In this article, TechSparks will comprehensively explore topics related to ICT testing, including its concepts and features.

What is ICT Testing

ICT, short for In-Circuit Testing, is an efficient circuit and electrical testing technique achieved through customized hardware and software. What makes this method unique is that it verifies connections and component correctness without the need to disassemble components from the circuit board. Essentially, you can think of ICT testing as an advanced multimeter. During testing, the PCB is placed in a test fixture, and then test points are probed using probes or a bed of nails. ICT testing covers various aspects, including connection testing, component testing, power testing, and thermal testing. With ICT testing, you can identify over 90% of errors in the PCB assembly process, saving a significant amount of time and cost. Specifically:

In connection testing, reliability of connections is verified by measuring the current and voltage at test points.

Component testing focuses on validating the values of various components on the PCB, ensuring they are within specified ranges.

Power testing confirms whether power consumption in different parts of the PCB meets expectations.

Thermal testing uses thermally sensitive components or infrared temperature measurement to detect temperature distribution on the PCB.

Characteristics of ICT Testing

As the most commonly used testing method in the PCB industry, ICT PCB testing offers great flexibility, allowing users to customize it based on specific project needs. For small projects, flying probes can be used to test components individually, verifying their connectivity. For larger projects, bed-of-nails fixtures can be used to detect multiple connections and components on the circuit board in a shorter time. Additionally, ICT testing provides convenience for prototype projects. In situations where design modifications may be needed, ICT testing allows for software updates at any time, ensuring that you always use the latest testing methods and standards to meet evolving requirements.

Moreover, ICT test PCB is known for its accuracy. Test equipment typically has high-resolution measurement capabilities, directly checking circuit connections and components for accurate resistance, capacitance, inductance, and other parameters. In addition, equipment integrates multiple testing functions, allowing simultaneous testing of multiple components and circuits. This ensures that potential issues in the production process can be identified and addressed early, ensuring products meet high-quality standards.

Compared to other PCB testing methods, ICT is renowned for its fast turnaround and low cost. It can complete tests for all components in a few minutes or even less. As the testing time for each PCB shortens, the overall cost of the testing process also decreases. The entire testing process can be automated using equipment, saving significantly on labor costs.

However, it’s essential to note that ICT testing requires customized test fixtures, making it a relatively expensive testing method. Additionally, these testing tools need regular cleaning and replacement to prevent malfunctions. Importantly, as mentioned earlier, while ICT testing can identify 90% of errors, it may not always detect contact instability caused by cold/soldering issues.

PCB Defects Identifiable by ICT Testing

In-Circuit Testing is an efficient method for detecting defects in electronic circuit boards, capable of finding various types of defects. Here are some defects that can be discovered through ICT testing:

Soldering Issues:

  • Short circuits: ICT can detect short circuits that should not exist in the circuit.
  • Open circuits: It checks for open circuits, indicating unconnected portions.
  • Poor soldering: It verifies if solder joints are secure, avoiding connection problems caused by poor soldering.

Component Issues:

  • Missing components: ICT detects whether there are components that have not been installed.
  • Component polarity errors: It checks if components are installed with the correct polarity.
  • Damaged components: It identifies components that are damaged or malfunctioning.

Circuit Parameter Issues:

  • Resistance value: It tests whether the resistance values in the circuit meet specifications.
  • Capacitance and inductance: It detects the values of capacitance and inductance in the circuit.
  • Frequency response: It examines the circuit’s response at different frequencies.

Power Supply Issues:

  • Power supply voltage: It checks if the power supply voltage is within the specified range.
  • Power supply current: It examines the circuit’s power consumption and current consumption.

Special Function Testing:

  • Communication interfaces: It tests the normal operation of communication interfaces.
  • Sensor detection: It verifies the accuracy and sensitivity of sensors.
  • Memory testing: It checks the read/write functionality of memory.

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