Why PCB Tests are required
Any electronic product even if properly designed and built with utmost care is prone to bug and issues. It is very crucial to test the product or PCB thoroughly in early stages of design to save millions of dollars later. The testing can be done at PCB design level wherein after using various design analysis techniques like EMI, Signal Integrity and Power Integrity, the design issues can be minimized. But how do you test the PCB once bare- board PCB is in your hand or after components population i.e. assembly has been done? How do you make sure that there are no shorts, open or bad solder joints? How to make sure current capacity, performance, component value and Impedance are within proper and expected tolerance level?
What are PCB Test Jigs and ATE?
Also we should know and comprehend the common terms used in the Electronics hardware testing domain. Specialized and custom designed Test jigs and fixtures are used to test pcb. Test Point are identified and probed to identify the input to be given and output to be measured. A test jig can be identified as a device or machinery that holds a piece of machine work which now a days comprised of much electronic intelligence and guides the tools operating on it. It should not be confused with Test fixtures which are used to keep the object firmly in place. However, in PCB testing both the terms test jigs and test fixtures are interchangeably used as is meant as a electro-mechanical solution to test the printed circuit boards or PCB’s. Custom made Test jigs and test fixtures are made as per the application of the board to test its test points. Automated Test Equipment (ATE) are those apparatus which makes these tests automated and help to identify issues even at System-On-Chips and Integrated circuits levels. So how do we test PCBs ? we use test jigs, test fixtures and ATE to test the Printed circuit board.
Board testing at various levels
- Bare-Board Tests
- Assembly Level Tests
Bare-board test are the tests done on unpopulated boards where netlist defined circuit connection is verified properly on the fabricated board. A small voltage is applied and is verified at the appropriate points, a “short”, “open” are identified in these types of tests. Industrial CT scanning can show details of soldered path and connections by generating a 3D rendering of the board along with 2D image slices.
Assembly Level Tests & Functionality Tests
After the board has been properly assembled it may be tested in a variety of ways using either manual inspection or using expensive Automatic test equipment (ATE).
Automatic test equipment enables PCB test, and equipment test to be undertaken very swiftly. Automatic test equipment is quite expensive, and therefore it is necessary to select the proper type suitable for the application and board to be tested.
In-Circuit Test, ICT
In-Circuit Test, ICT is a form of ATE is very effective form to test printed circuit boards. It can find short circuits, open circuits, component values, and it can checks the operation of ICs.
JTAG boundary scan
JTAG boundary scan uses the dedicated test logic built into Integrated circuits (ICs), to check if each device is correctly soldered and is properly inserted onto the PCB. The devices which include this logic are FPGAs, CPLDs, microprocessors, DSPs, bus logic, SERDES, telecom encoders, PHYs, ASICs, and Bridges (PCI/PCIe).
When the function of the circuit is tested it is known as Functional test. Functional testers typically interface to the PCB or device under test via its test-probe points or edge connectors. This testing is the simulation of the final environment in which the PCB is meant to function. The test equipment can be chassis or rack based or test equipment which uses GPIB.
A company which has specialized knowledge on various aspects of PCB tests, can be in assistance of OEM and suggest the best test method and test equipment to improve and test the product reliability , defect and issues early in the product life cycle and can thus save both the product development crucial factors cost and time.
Argus Systems Test engineering team can design and offer customized solution for customer specific Requirements.
Services offered are
- In-Circuit Test Development
- DFT implementation and Probe accessibility audits
- Fixture fabrication data to support the vendor of your choice
- Complete documentation and test program conforming to your requirements
- Panellized board testing
- Board testing utilizing dual access, bi-level fixturing
- Boundary-scan test support
- Rapid test program development