Advantages And Disadvantages Of In-Circuit Testing

When it comes to testing PCBs, ICT is considered one of the best methods. It may have a high initial cost and other limitations. But many manufacturers use the bed-of-nails type of test fixtures in Jacksonville for comprehensive and reliable results. Weighing its pros and cons can help you decide whether to go for it or not.

What Is ICT Testing?

ICT stands for in-circuit test in the world of circuits. This method is also known as the bed-of-nails ICT. This testing method is used to check for faults in a printed circuit board (PCB), such as shorts, opens, etc. using electrical probes.

The test is usually performed with the help of a featureless in-circuit alignment or bed of nails type of test fixtures. Here, we will look at the latter type of testing equipment. This is a fast, effective and accurate way of analyzing defects in the board. It allows you to identify and replace defective parts.

ICTs may use suction cups to check the sturdiness of the solders and the malleable strength of the chips.

How Does In-Circuit Test Work?

The PCB is pressed by the operator against the fixed bed of probes that have been designed to fit a particular circuit board. The needles shoot up from the bottom and come in contact with the board. The boards are designed to allow access to the pins. The tester uses these pins to measure the values of the PCBs. 

These values determine whether the test was successful or not.

ICT is fully automated with no human input needed in most cases. A technician presses the circuit board down and hits the start button. They may also give a few okays here and there but the fixture does the measurements.

Advantages Of ICT

- Easy Test Setting: You can program the In-circuit tester to test errors in continuity, components and more with ease.

- Consistency: ICT gives the same test the same way.

- Quick: This method takes only one minute because it contacts all of the board’s test points. Flying probe testers, by comparison, take about 25 minutes. This makes it economical for large volumes.

- Ball Grid Array: ICT can be used to test ball grid array (BGA) assemblies, unlike flying probe testers or automated tet inspections.

- Straightforward Interpretation: You don’t necessarily have to be a trained professional to interpret the results. They are straightforward and leave little room for operator errors or poor decision-making.

- Comprehensive: Each component is tested individually during the process. You can use it to test assembly defects and functionality. It’s among the more comprehensive testing methods.

- Low Maintenance Cost: In-circuit testers are very low-maintenance and it saves maintenance and repair costs by making some other tests unnecessary.

Disadvantages Of In-Circuit Test

- Design Adjustments: You may need to alter the PCB design to test it through ICT. Moreover, your board needs to have as many access points as possible for the nails to reach their destination.

- Cost: The initial cost of purchasing an ICT fixture is high. The exact cost may depend on its size and complexity. Moreover, most manufacturers offer an expensive support contract.

- Maintenance: You need to clean and replace the pins regularly.

- Failures: Failures may occur when the test pins don’t contact the appropriate test pads. It may also fail to identify high-density small package size SMT components.

- Inability To Test Certain Components: It’s unable to test connectors, non-electrical components and test components that work together.

When To Use It?

In-circuit testing works best on surface mount technology (SMT) designs. Sticking to one-layer or one-sided designs for the test works best. It’s ideal for you if you’re planning to stick with a continuous product design for 3-4 years. Moreover, an order of 3000 or more PCBs is needed before ICT becomes viable. If you’re looking to test 100 PCBs, the upfront cost might not be worth it.

Alternatives

Needless to say, visual inspection is not an alternative. Though you can use it for additional assurance, it’s best used for crimping wires in Jacksonville. Real alternatives include 

- Flying Probe Testing: Consists of moveable probes that move from one test point to another.

- Automated Optical Inspection: Uses one 2D or two 3D cameras with a light source to take precise pictures to be compared with the schematic diagrams.

- Automated X-ray Inspection: Similar to AOI but uses x-ray to inspect hidden components.