Engineer’s Guide to ICT (In-Circuit Testing)

ICT In-circuit test

PCBs are complex with multiple layers, hundreds of components, thousands of solder connections, and traces running every which way. Each component of the printed circuit board is expected to perform its role in the design in order to carry out the engineer’s vision. Even a minor defect could affect the overall quality and performance. PCBA testing can be done in a variety of different ways but today we will focus on ICT (in-circuit testing). In-circuit testing checks individual components on the board and its electronic characteristics for any imperfections. This is why ICT (in-circuit testing) has been a relied upon method of testing for electronics for years.

What is In-Circuit Testing

In-Circuit Testing, ICT is a method of testing which helps detect defective components by using an electrical probe to check components at individual points. ICT checks for shorts, opens, resistance, capacitance, and other basic quantities which will flag any discrepancies. This fully automated test allows the techs to replace any faulty parts and thus move it along to QC for approval before its end use. In-circuit tests are usually conducted in two parts such as Power-off Tests and Power-on Tests. As the name implies, in Power-off Tests, tests are conducted before power is applied and in the second part, tests are performed after power is applied.

Defects Identified Through In-Circuit Testing

ICT’s popularity stems from the amount of errors it is able to find on a board. Its through test coverage is a huge reason. Other methods may check that a board works but ICT verifies each component on a board, one by one. ICT encompasses the following:

  • Short circuits
  • Solder bridges
  • Wrong or missing components
  • Component spacing, lead spacing, land sizes, and component sizes
  • Component markings
  • Soldering and process issues
  • Shorts between traces and/or component leads
  • Open circuits (“opens”) where electrical continuity should exist
  • Resistor Values
  • Jumpers/switches in correct location/setting or not
  • Presence or absence of passive components
  • Presence or absence of active analog components
  • Analog components with wrong orientation
  • Digital components with wrong orientation
  • Capacitance and inductance values

Where ICT falls short is detecting multi power connections missing, redundant power connections decoupling capacitors missing, mechanical fixings, and overall look of the board among other things.

Types of In-Circuit Tester

Engineers should familiarize themselves with the different in-circuit test systems that are available on the market right now and understand how each differs. Understanding the difference in performance, capability and procedure helps ensure the best final product at the best cost available. It is crucial that the engineers utilize the right tester to access required points on the printed circuit board. No matter the tester, there are some common elements to all ICT testers:

  • Software
  • Controller
  • Fixture
  • Interface
  • Powered Analog Tests
  • Analog Scanner
  • Analog Digital Opens

ICT is a reliable, high-quality, high-volume testing, ensures that the circuit has been manufactured correctly to perform to the highest standard in applications.

OEMs require nothing less than perfect when it comes to the PCBs used in their products. Even a small flaw with the PCB can drastically affect the overall functioning and reliability of the end use. Companies are currently implementing stringent quality checks and test during the assembly process. The term in-circuit testing, as a result, has been relied upon for a quick and reliable test method that delivers component-level failure analysis.

Pros and Cons of ICT

Like any other form of circuit board testing, in-circuit tests have several advantages and disadvantages. When determining the best method of test for any given application, it is crucial to review the pros and cons of each system thoroughly.

Advantages of In-Circuit Testing

Since its a relatively simple, fast, and accurate method of testing with ability to locate fault location, ICT is becoming more and more popular today. Engineers employ this method because of the following:

  • ICT is extremely easy to program and detects defects in components, continuity and other faults.
  • Operation is easy and leaves little room for error
  • Speed (usually 1-2 minutes per assembly). As a result, the test is great for larger volumes.
  • Very reliable and comprehensive as compared to other methods of test.
  • In-circuit testing is very thorough and assures high fault coverage for manufacturing defects.
  • Test results are relatively easy to understand.
  • Best testing method for medium to high volume through-hole PCBAs.
  • Requires minimal maintenance costs.

Disadvantages of ICT

In-circuit testing is not a catch all and includes its own set of drawbacks

  • Test fixtures are expensive to create and develop.
  • ICT sometimes cannot identify connector faults in high density, small package size SMT components.
  • If test pins do not make proper contact with the appropriate test pads it shows inconsistent results .
  • Test pins must be regularly cleaned and replaced to prevent failure and false calls.

Even with these flaws, the technology is still considered one of the best ways to test many PCBAs to this day.

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 Vinatronic 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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