In-Circuit Testing (ICT): Help You Produce High-quality PCBs

In-Circuit testing has emerged as a powerful and indispensable tool in the PCB manufacturing process, providing a comprehensive evaluation of the electrical integrity and performance of the assembled PCBs. At Highleap Electronic, we are dedicated to utilizing advanced ICT techniques to deliver high-quality PCBs that meet the stringent standards of our clients.
This article provides a comprehensive overview of In-Circuit testing covering test, In-Circuit testing workflow, fault diagnosis, and pros and cons of In-Circuit testing.

What is In-Circuit Testing （ICT）

In-Circuit Testing （ICT） also known as the bed-of-nails In-circuit test. It is an electronic testing method used to verify the quality and integrity of circuit board assemblies.
ICT leverages mechanical “bed-of-nails” test fixtures that make temporary electrical contact with test nodes across the board being tested.These pins establish temporary electrical connections with test nodes distributed across the board under examination. Any deviation from the anticipated node levels serves as a precise indicator of potential assembly defects, such as incorrect components, missing parts, subpar solder joints, short circuits, or open circuits.
ICT are usually conducted in two parts such as Power-off Tests and Power-on Tests. This type of testing is particularly effective for high-density PCBs with numerous components.

How an In-Circuit Testing (ICT) works

Fixture Setup

The test fixture is tailor-made for a specific PCB or product and is equipped with a bed of nails or pogo pins. These pins are strategically placed to establish electrical contact with various points on the PCB, such as component leads and test points.

Test Program Development

The test engineer creates a test program for the PCB being tested. The test program encompasses a series of test routines and measurements to be executed on the PCB. The program may include continuity checks, resistance measurements, capacitance measurements, voltage measurements, and functional tests.

Test Execution

To conduct the test, the PCB earmarked for examination is inserted into the ICT fixture, ensuring it aligns with the bed of nails or pogo pins.

Testing

Utilizing the program, the ICT system initiates the testing procedure by transmitting test signals to the PCB via the fixture’s pins. Subsequently, it proceeds to record the PCB’s responses at multiple test points. By comparing these measured values to the expected ones, the system can readily identify any inconsistencies or faults. Commonly detected issues encompass missing components, inaccuracies in component values, short circuits, open circuits, and soldering imperfections.

Reporting

The ICT system produces an extensive test report that specifically points out any test failures or variations from the anticipated values. This comprehensive report serves as a valuable tool for pinpointing and locating defects on the PCB.

What Problems can be detected with In-Circuit Testing?

Power-off tests

• Shorts between component leads
• Open circuits where electrical continuity is cut short
• Absence of passive components
• Lack of active analog components
• Altered degrading values on the resistors
• Jumpers
• Check for missing non-electric components.

Power-on tests

• Wrong analog component
• Wrong digital component
• Misoriented analog and digital component
• Capacitance and inductance values.
• Transistor beta
• Stuck process bus
• Diodes and Zener diodes
• Fuses and switches
• Excess solder

Advantages of ICT

• Ease of Programming: ICT is remarkably straightforward to program and excels at detecting component defects, continuity issues, and other faults.
• Minimal Margin for Error: Its operational simplicity minimizes the potential for errors, ensuring reliable results.
• Speed: ICT typically completes a test in just 1-2 minutes per assembly, making it ideal for larger production volumes.
• Reliability: Compared to alternative testing methods, ICT is highly reliable and provides comprehensive coverage for identifying manufacturing defects.
• Low Maintenance Costs: ICT requires minimal ongoing maintenance, reducing operational expenses.
• Ideal for Medium to High Volumes: It’s considered the best testing method for medium to high-volume through-hole PCBAs.

Defects Identified Through ICT

• Creating and developing test fixtures can be a costly process.
• ICT may struggle to detect connector faults within densely populated, small-sized SMT components.
• Inconsistent results can occur when test pins fail to establish proper contact with the designated test pads.
• Regular cleaning and replacement of test pins are necessary to prevent failures and erroneous readings.

PCBA testing is a crucial part in the manufacturing process and having an understand of the methods can result in the best possible final product. The staff at Highleap Electronic has extensive knowledge in ICT as well as the other test methods. Feel free to reach out to our team for your next project and we’ll happily offer our advice.
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