Basic Things You Should Know About In-Circuit Testing

Printed Circuit Boards are considered as a complex assembly with hundreds of components and thousands of solder connections. Each component in such an assembly is ought to perform to the highest standard as even a minor defect can affect the overall quality and performance. So, how would you test individual components on the board and its electronic characteristics for any imperfection? Here is where the significance of In-Circuit testing (ICT) lies in. Would you like to know more about this cost-effective testing method that delivers component-level fault diagnosis? Then here you go.

What is In-Circuit Testing

In-Circuit Testing, ICT is a powerful tool, which helps detect defective components by checking them individually. ICT is a highly accurate form of testing that performs a “schematic verification”. The ICT, which is a fully automated test, thus helps detect defects in an assembly, which can be replaced accordingly before making it final. ICT is 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.

What defects are identified in In-Circuit Testing

What accounts for the immense popularity of ICT? Its comprehensive test coverage is the prime reason. Compared to other ways of testing, ICT tests each component on a board, one at a time. The method tests the following in a printed circuit board.

  • 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
  • Values of resistors in the circuit
  • Jumpers/switches in correct location/setting or not
  • Presence/absence of passive components
  • Presence/absence of active analog components
  • Misoriented analog components
  • Misoriented digital components
  • Capacitance and inductance values
  • Wrong or missing components
  • Solder bridges
  • Short circuits

However, ICT fails to detect multi power connections missing, redundant power connections decoupling capacitors missing, mechanical fixings, and overall look of the board among others.

Elements of In-Circuit Tester

There are several types of in-circuit test systems available on the market and each differs with respect to the other in terms of performance, capability and testing procedures. It is important that the PCB manufacturer should employee the right tester to access required points on the circuitry. Whatever type you choose, there are some components common to all ICT testers, they are as follow:

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

ICT, which is a reliable, high-quality, high-volume testing, ensures that the circuit has been manufactured correctly to perform to the highest standard in applications. So far you have seen a few basic things about ICT including the definition, defect coverage and elements in a tester.

Product manufacturers look for nothing less than perfect when it comes to the printed circuit boards used in their products. Since a small flaw of the board drastically affects the overall functioning/performance of the end applications, PCB manufacturers are currently implementing stringent quality checking and testing during the assembly. The term in-circuit testing thus has utmost prominence as it is considered as a quick and reliable testing method that delivers component-level fault diagnosis. The last post concentrated on ICT including its test coverage and elements. This post discusses the advantages and disadvantages of the same.

Advantages of In-Circuit Testing

With the assurance of simple, fast and rapid, accurate fault location, ICT is becoming more and more popular today. The testing method is vastly employed due to its several advantages including:

  • In-circuit tester is extremely easy to program to detect defects in components, continuity and so on.
  • There is a very little room for operator error.
  • It will not take a long time to detect errors (usually 1-2 minutes per assembly). Hence, the test is economical for larger volumes.
  • It is a highly reliable and a comprehensive testing method as compared to other testing methods.
  • In-circuit testing assures high fault coverage for manufacturing defects.
  • Its test results are relatively easy to interpret.
  • It is the best testing method for medium to high volume through-hole conventional assemblies.
  • In-circuit test (ICT), which has been around for many years now, requires minimal maintenance costs.

Disadvantages of ICT

Every technology will have a set of drawbacks as well. In Circuit testing is also not free from the same. The following are amongst the disadvantages associated with ICT.

  • Its test fixtures are expensive.
  • ICT sometimes fails to identify connector faults in high density, small package size SMT components.
  • It shows inconsistent results if test pins do not make proper contact with the appropriate test pads.
  • Its test pins need to be regularly cleaned and replaced to prevent failure.

Although the testing method has some flaws, the technology is still considered as the best way to test a printed circuit board (PCB) assembly.

Conducting PCB testing and inspection not only helps manufactures to check the performance of each component but also enables them to complete the testing in less time. ICT, which have been in use for many years, still maintains its popularity owing to its ability to rapidly respond to dynamic product test requirements. All the leading names like Accelerated Assemblies, who offer prototypes and/or printed circuit board (PCB) assembly services, utilize ICT as a major tool to test the boards for defects.