PCBs are highly complex because it’s made up of a large number of components. It is crucial that each of these components performs to its optimal capacity. Any defect in these components can lead to the malfunctioning of the PCB and hence of the electronic device. That’s why testing each component separately becomes very important. This is what in-circuit testing entails as it helps in diagnosing any faults in the components of the PCB.
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What is In-circuit Testing?
In-circuit testing helps in testing components of the board individually; so, we can determine faults if it is present in a particular component. An automated test goes a long way in detecting the defect & taking appropriate action. In-circuit testing is conducted in two parts:
- Power-off tests
- Power-on tests
Why is In-circuit testing important?
The simple reason for in-circuit testing being so important is the fact that it helps catch errors before they become too costly. The importance of this testing also lies in the following facts:
- They are easy to program.
- There is little room for operator error.
- The testing is quick & reliable.
- The testing is comprehensive.
- The results are easy to interpret.
ICT & Fault Coverage Verification
ICT is typically known to find around 98% of faults and therefore is known for its high fault coverage. The reasons why some faults may be left undiagnosed is because:
- It isn’t always possible to gain total coverage of the board.
- Low value capacitors can pose a problem.
- It may not be possible to access all nodes on the board on account of varying reasons such as the tester having insufficient capacity, the tester is shielded by a large component. In such cases implied testing needs to be carried out where a section of the circuit is tested as an entity.
Defect that identifies by In-circuit Testing
With in-circuit testing, the following parts of a PCB are tested and defects identified:
- Component spacing
- Soldering
- Shorts
- Open circuits
- Resistor values
- Jumpers & switches
- Wrong or missing components
- Components that aren’t correctly oriented
- Capacitance value
- Inductance value
- Short circuits
Components in ICT testing
There are a number of in-circuit test systems that are available. Irrespective of the kind that you choose, some components that are common to all ICT testers include:
- Controller
- Software
- Interface
- Fixture
- Analog scanner
- Powered Analog tests
- Analog Digital Opens
ICT Testing Advantages
ICT offers a wide variety of advantages including:
- It is highly accurate.
- It is fast and reliable.
- It is easy to program.
- Is economical, particularly when it comes to bulk testing.
- Ensures high fault coverage.
- Works well for through-hole assemblies.
- Does not require high maintenance.
ICT testing disadvantages
Despite the fact that ICT is quite comprehensive, it comes with its own set of disadvantages, namely:
- In case of small SMT components with high density, this method isn’t too helpful.
- In case the test pins aren’t in proper contact with the test pads, there will be inconsistency in results.
- It is imperative that the test pins are cleaned so that chances of failure are minimized.
Different types of In-circuit testing equipment
Even if the term In-circuit testing is widely used, the fact remains that there are several different types of testers. The choice of testers largely depends upon:
- The manufacturing/test process used
- The volume & type of boards
Some of the In-Circuit testing equipment that are widely used, include:
Standard ICT Machine
This offers basic resistance and continuity measurements while also offering capacitance testing as also testing of device functionality.
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Flying Probe
This is found extremely useful as it has a fixture to hold the board. Importantly, contact is made through probes that can move around the board. The fact that there is a software that makes it easy to accommodate any board updates, adds to its efficacy
Manufacturing Defect Analyzer
Popularly referred to as MDA, it offers testing related to resistance, continuity as well as insulation. This test is useful for ascertaining manufacturing defects such as open circuit connections or short circuits
Cable Form Tester
This tester comes in handy to test cables. It works like the MDA, however, in this case, sometimes, high voltage needs to be applied to test for insulation.
In-circuit Testing FAQs
1. What is the difference between dynamic testing and in-circuit testing?
ICT is an example of white box testing wherein an electrical probe tests a populated printed circuit board for its individual components. It helps check for faults such as shorts, opens & more. When it comes to dynamic testing, the board is exposed to high temperatures and input signals are applied to all components of the board so that the exact point where PCB failure may occur, is identified.
2. What is ICT for PCB?
ICT or in-circuit testing helps check a printed circuit board for faults such as shorts, opens, and more. It works by checking errors that occur during fixing components on the board. Essentially, it helps you replace any defective part, easily. Additionally, ICT also help check whether the solders are sturdy as well as the malleable strength of chips.
Mer-Mar Electronics is proud to be one of the reputed organizations offering high-quality PCB assembly services for over 40 years. Our in-warranty rejection rate for assembly defects has averaged below 0.7%. Our consistency in product quality and regular upgradation of the latest tools and machinery is the primary reason we are able to retain our customer base year to year.
