PCB FCT test: A Comprehensive Guide

An integral element of building a PCB is testing its circuitry. Manufacturers may ensure top-notch product quality and avoid a wide range of production faults by conducting functional tests. Multiple circuit tests are at the disposal of manufacturers, one of which is FCT.

What is FCT in PCB?/What is the ICT electronics test?

FCT is the acronym for functional circuit test. It is a type of test performed on printed circuit boards during the manufacturing process. FCT involves testing the board by stimulating its operating environment. The text investigates glitches, such as open circuits and shorts in the PCB, and verifies if the board is functioning appropriately. FCT is a relatively straightforward scrutinization that does not require any specialized equipment. If any problems are found during the test, qualified technicians will typically be able to isolate them and determine what caused them. FCT is a veritable step in PCB quality control, typically performed after the soldering process.

Likewise, the ICT or In-circuit electronics test aims to scrutinize the performance of all board components and check for defects in the production process. In-circuit testing (ICT) is a software-based procedure in which a machine manually positions the PCB on a series of pins (spring-loaded). The pins align to different testing points on the PCB. The resistivity and capacitors of a PCB can be tested in-circuit to guarantee that the final specs are correct.

Why is FCT Important?

Functional circuit test is essential because it helps ensure the PCBs function correctly and there are no manufacturing defects. Moreover, it is a test that can help identify problems with the PCB before it is shipped to the customer. Thus, the test helps save manufacturers time and money.

What is required for Functional Testing?

The things required for FCT are –

• Test fixture to hold the PCB in place during the examination
• Probe cards to link the test equipment to the PCB
• Test software to manipulate the testing method and gather important data

Top Three Benefits of Performing FCT for Your PCB Assembly

• FCT can enhance product quality by detecting functional glitches early in manufacturing
• The test also allows you to make design changes quickly and easily without incurring heavy losses.
• The functional circuit test can save time by identifying potential problems with the PCB before it is shipped to the customer.

Classification of PCB FCT Test

Classification based on the control mode

• Manually controlled functional tests
• Semi-automatic functional tests
• Fully automatic functional tests

The best PCB FCTs are mainly automatic and semi-automatic. With the rapid development of technology and intending to improve production efficiency, most functional tests have become fully automated. However, manual and semi-automatic FCT continues to be in use to simplify design and reduce production costs.

Classification based on a different controller

• MCU controller and Embedded CPU controller – They are speedy and simple functional circuit tests targeted at dedicated circuits and programs for data display and output. Both of them have highly targeted test solutions.

• PC Controller – It is the most widely used FCT because of the ubiquitous availability of PC technology. In addition, lower prices also contribute to its popularity. Here, the data output and file processing of the test outcome can be quite convenient to achieve on the PC operating system. Moreover, the entire operation of the test software is very intuitive.

• PCL Controller – It is a common FCT in the development mode and focuses on the need to control the induction part. PLC is mainly used for professional industrial control.

Other Different PCB Testings

Besides functional circuit tests, other PCB testings are –

• X-ray inspection
• Peel test
• Soder float test
• PCB contamination test
• Micro-sectioning analysis
• Four-terminal sensing
• PCB solderability test
• Fourth-terminal sensing
• Time-domain reflectometer test or TD

How to Make Functional Circuit Test or FCT

Now that we have dabbled into the basics of the FCT, it is time to learn how to make one. Firstly, you will need the following things for a successful PCB FCT –

• A breadboard
• Jumper wires
• An oscilloscope

Firstly, you have to connect the power supply to the positive and negative rails of the breadboard. After that, you must connect the oscilloscope to the power supply. One end of the jumper wire should be connected to the positive rail and the other tip to the rail (negative) of the breadboard.

An additional jumper wire is needed, with one end connected to the breadboard’s positive rail and the other inserted into a hole in the row directly above. Make sure to do it for each row until there are eight connected rows.

Finally, link the last jumper wire from the top left to the ground, and viola, your functional circuit test is complete.

FCT Test Fixture

The FCT test fixture is a device that we use to test PCBs. They have a power supply, an oscilloscope, and a breadboard. As the name suggests, the power supply renders power to the PCB while it uses the oscilloscope to measure the voltage levels on the PCB. Finally, the breadboard is used to connect the multiple components of the FCT test.

FCT Test – test Points

Test points are the places on the PCB where we can measure the voltage levels. Furthermore, they are also co-opted to connect different parts of the FCT test and are typically marked with a red or black dot.

FCT Test – ICT Test

The ICT examines the PCB for any potential shorts between the various tracks. High voltage is applied to one track, and the effect is measured on another. If there is a short, the voltage’s power is lower than expected. The ICT test is fundamental in finding shorts that are not visible to the naked eye. Thus, every PCB must pass the ICT test.

Summary

In a nutshell, the PCB FCT is a fundamental part of the PCB manufacturing process. It helps us ensure that the boards function as they should, without glitches, defects, or errors. So, in case you are looking for a reliable PCB manufacturer, start by enquiring about the inclusion of functional tests in their boards. In Absolute PCB, we never compromise on quality, and our complete PCB FCT is a testament to our manufacturing process’s prowess.