Article by Dario Gozzi
In-Circuit Testing and Functional Testing are the two main methods for the testing of assembled electronic boards. ICT focuses on testing individual components and detecting manufacturing defects. FCT evaluates the functionality and overall performance of the assembled board. Understanding the differences is critical to selecting the appropriate approach based on the PCBAs to be tested. By leveraging the strengths of ICT and FCT, manufacturers can ensure the quality of their assemblies in various applications. Although ICT and FCT both aim to identify defects and failures, they differ in approach and scope. In-circuit Testing is a method to test electronic components and connections on a PCBA, to verify the correct assembly of components and ensure their proper operation. It is typically performed early in the manufacturing process to detect and correct any problems to prevent defective products from leaving production.
The ICT measures various parameters such as resistance, capacitance, and diodes. It verifies that electronic components are correctly placed and connected. And it provides a complete control of the board with the goal of intercepting defects that arose in manufacture. A specific software controls the testing process. This allows accurate measurements and reduces the risk of misjudgment. With ICT, manufacturers can simplify troubleshooting and eventual PCBA repair. This not only speeds up the production process, but also improves the quality of the final product. Functional Testing is a test method that evaluates the overall functionality of the assembly. Unlike ICT, which focuses on individual components, the FCT tester tests the entire PCBA. This test method simulates the operating environment of the device under test (DUT). And it checks its various functional parameters such as voltage, current, power factor, frequency, and duty cycle.
Electronics today
The widespread deployment of electronics presents major challenges for electronic board manufacturers. This in terms of process technology, materials, fast product changes, variability in the batches etc. As a result, they also face the same challenges in the testing phase of manufactured boards. There is often the need to test densely populated boards on both sides. They are boards with test points having limited or no access, with components to be programmed. And even special features, such as LEDs, requiring both electrical and optical functional testing. All regardless of the size of boards and components.
Considering the levels of hardware and software achieved nowadays, mobile probe testing technology should be viewed from a holistic aspect. The performance of the whole is greater than the sum of its individual components. Flexibility, excellent coverage and speed of testing are three very good reasons for approaching this testing philosophy. This because they make it a business-strategic investment with extremely beneficial economic-productive implications. In addition, Flying Probe testing has the enormous advantage of not needing fixtures. Which means not having to set up extra equipment and locate a space to store it.
Technological developments
The ability to perform full testing simultaneously on both sides of the board is now an indispensable requirement. Flexibility is characterized by having an adequate number of heads to support the functions with which the system is equipped. The heads are equally distributed on both sides of the board, which is increasingly positioned vertically. The vertical position of the board has many advantages, including inherent stability during testing. And a size-optimized physical architecture of the system (small footprint) that saves space. Placing the measuring instruments directly inside each head makes it possible to speed up test execution. It also makes it possible to eliminate disturbances and improve measurement accuracy and overall performance. Besides, the addition of the more advanced performance means that in addition to traditional ICT testing, functional tests and Boundary Scan can be performed. And doing component programming on boards that require it can also be performed.
Test speed is as crucial as the previous features. And it could not be otherwise, because slow testing is a bottleneck on the line as it lowers its productivity. In the case of flying probe testing, speed should not only be considered relatively test execution. But also under the “logistics” aspect. The flying probe tester does not require tooling and is quickly programmable simply by importing CAD data. In the past these testers were mostly oriented toward prototyping, today they also belong to the world of medium/high-volume production. Not only because of the performance in terms of testing speed, but also for a new testing concept: distributed testing.
Distributed testing
The concept of distributed testing is based on the integration of multiple systems in a line, usually automated. Each is dedicated to performing a part of the application required by the product testing specifications. The modular approach simplifies the specialization of the system according to the type of test for a specific product, allows for the optimization of the testing process time and the reduction of costs. The time and tooling required for product code changes are practically reduced to zero, in most cases.
It is not difficult to see how much all this contributes to speeding up time-to-market and helps to achieve immediate results, as much in prototype testing as in production. It all makes it a strategic tool for producing profits and, not least, for giving a quick return on investment. Functional testing is for all intents and purposes an integral part of the process and cannot be separated from feeding the board. The latest generation probes can bring power directly to the board while dedicated software commands allow switching between the measurement (or stimulus) state and the delivery of a programmed current value.
Today, very often electronic boards also include Boundary Scan Components. The most advanced flying probe systems offer the possibility of specializing one of the flying probes with a multi-channel tool that extends its contact capability, without the addition of external cables. From here to the integration of on-board programming capability is a short step.
The platform of modern flying probe systems also includes the ability to perform various types of tests on board-mounted LEDs. Among these tests we have RGB, saturation, and intensity, performed through the addition of specialized sensors and LED spectrometers, which are the most commonly used tools for this type of testing. Performance ensuring the positioning accuracy of the probes has become increasingly important to address the growing miniaturization of the circuits being tested. A key performance to increase the contact accuracy of probes is the measurement, by laser, of any deformations of the board, this allows the calculation of the resulting Z-axis positioning compensation.
This performance also measures component height, an essential piece of data for optimizing test paths and verifying the presence/absence of the component itself. Real-time control of the pressure exerted by probes on the test points is critical to avoid board and component damage. The most advanced flying probe systems have the ability to detect probe contact pressure, collecting, for each test point, the force applied during the test. Together, the force measurements at the various points make it possible to generate topographic maps of the pressure exerted on the device under test, providing an additional element of process quality traceability. This is especially important when dealing with delicate ceramic boards and on wafers, as well as on PCBAs for avionics and satellite applications, where contact delicacy and traceability are a must.
The power of software
At the end of design validation, using the resources of the software platform and CAD data from the design, the software of a modern flying probe system enables the automatic generation of a complete test program, a process that needs to be lean and fast to minimize setup time for prototype, pre-series, and production testing. Optimized software management enables parallelization of different types of tests, saving valuable operational time. It can also include intelligent analysis functionality, which, using a set of algorithms based on artificial intelligence principles, further optimizes the test flow at runtime, thus keeping coverage goals intact.
Full compatibility with the smart factory is now in basic requirement, and the software platform of an advanced flying probe system can provide intelligent integration with all aspects of the customer’s production processes (data collection, traceability, interaction with MES, repair operations). The platform can include on-board industrial management solutions for remote monitoring of power and voltage consumption, verification of power grid status and temperature level, status of indicator lights and all those parameters useful to indicate proper test operation, and to provide (always in real time) information related to predictive maintenance.
The solution at your fingertips
Pilot VX is a flexible, configurable test system with a technologically advanced toolset that can provide the test solutions required by the enormous diversity that characterizes today’s electronics and has become essential in many manufacturing environments regardless of board volumes and complexity because it is an extraordinarily powerful resource that can be used at every stage of the product lifecycle, from design through prototyping to production. Its ability to provide immediate and highly accurate access to all test points, coupled with an extensive suite of hardware and software measurement tools, enables testing and validation of prototypes and pre-series quickly and with minimal technical and economic effort, without requiring operators with extensive and specific training on how to generate and execute test programs.
For this reason and those mentioned above, Seica’s Pilot VX has emerged as the new gold standard in terms of speed and performance, a fully automated test solution that addresses the fundamental concerns of electronic board manufacturers wishing to optimize their investments.
