It seems like the word “test” has a really negative connotation attached to it these days. Maybe this is a carryover from our school days when tests were to be avoided at all costs. Whatever the reason, the word “test” has been falsely accused of all sorts of evil when, in reality, the exact opposite is true. Our lives are full of products and events that must be thoroughly tested to assure safety and comfort, and this includes the printed circuit boards that we have manufactured as well.
Printed circuit boards need to be tested for many different requirements. These include testing for manufacturing defects as well as testing for functionality. The key is to make sure that your contract manufacturer is fully testing your board so that you can have full assurance that the board will function in the field as expected. For this to happen, you need to partner with a CM that will go the extra distance with you on your PCB functional tests. Consider the following as you evaluate CMs for their proficiency in testing your board.
The PCB Functional Test and Why It’s Important
Your printed circuit board should go through many different testing phases while it is being manufactured. There are visual inspections that will utilize automated optical inspection and X-ray systems. The in-circuit test (ICT) and flying probe testing will reveal manufacturing defects, such as solder shorts, incorrect components, missing components, and open nets or connections. Even manual bench tests performed by technicians to look for specific signal or voltages can be conducted as needed. But the most comprehensive test to determine the final pass/fail status of your board after manufacturing is the functional test.
The functional test (FCT) will verify the functionality of your PCB. It will do this by applying a range of different signals and currents to stimulate the board’s behavior based on testing software developed for the board, and then measure how the board reacts. It will detect both analog and digital signal problems, including distortions, incorrect currents, and signal timing issues.
FCT is facilitated through a combination of connecting a cable to your PCBs on-board connectors, and the use of test probes contacting test points where necessary on your board. The testing software for the board is developed to conduct the tests per the specific requirements of the board’s function.
The goal of the functional test is to look at your entire board and its functionality to determine whether or not it has been manufactured according to your specifications. This requires a skilled and experienced manufacturer who knows how to best work with your board for testing.
How Your CM Can Help You to Get the Most Out of Your PCB Functional Test
The functional test is an evolving technology as these testing systems are constantly being updated with improved features and capabilities. There are also more libraries of test routines available now from component vendors, along with improvements in how these routines can be implemented within the testing programs.
All of this has helped to make functional testing of PCBs the reliable process that it has become in the hands of qualified users. To get the most out of testing your board, your CM should have the following:
- Qualified test engineers that continually evaluate and develop test coverage from an assembly and functional perspective.
- Personnel that will work together with their customers to help their customers design into their boards the features necessary for successful testing.
- A full array of testing equipment to not only handle the functional test, but also ICT, flying probe, or other testing procedures to handle any type of board that is manufactured.
- The ability to develop both the hardware and the software of test fixtures for customers that do not have this capability.
- The ability to evaluate existing customer test fixtures and work with them to implement any needed changes or updates in the hardware or software.
Your CM should be able to supply you with all of the information and recommendations needed for you to successfully design your board for complete testing. This requires a skilled and experienced staff that is ready to work with you.
Partnering With a CM That Gives You the Best
When choosing a manufacturing partner for your next project, you need a CM that knows what is needed to fully test your PCB, and that is armed with both the staff and the testing facilities to give you the best possible results.
The test engineers here at VSE bring with them years of experience in testing PCBs and are able to design, debug, tune, or update test fixtures as needed. They are skilled at evaluating PCB designs and working with design engineers to speed test development and debug times, as well as conducting thorough testing of PCBs. We are also fully equipped with a wide range of testing hardware and processes including:
- Automated optical inspection
- In-circuit test
- Flying probe
- CableScan
- LabVIEW
- Functional test
