Why is ICT testing rarely used in PCBA production
2024-11-21
ICT testing was once used in PCBA production to prevent short circuits, but was replaced by FCT with the advancement of electronic technology. ICT costs are high, fixtures need to be customized and maintenance is expensive, and PCBA design is limited. FCT testing covers a more comprehensive range and achieves functional testing through programming.
1.ICT testing used to be an important part of PCBA production.
ICT: abbreviation for In Circuit Tester.
In the era of underdeveloped technology, due to backward production processes and underdeveloped electronic technology, problems such as material placement, soldering, and air soldering often occurred, resulting in short circuits and open circuits.
For example, in the production of computer motherboards, ICT plays a crucial role in preventing the burning of testing equipment such as power supplies, CPUs, memory, graphics cards, and hard drives. It can intercept power short circuits, power and signal line short circuits, and prevent voltage increases caused by component soldering, reducing damage to testing fixtures and tools.
With the development of technology, electronic technology and production processes have been qualitatively improved. Electronic components themselves have short-circuit protection, overvoltage protection, overcurrent protection, and overheating protection, which will not cause PCBA to burn out.
The improvement of FCT testing has gradually replaced ICT testing, with a coverage rate of only 90%, mainly testing power supplies, connectors, and other major circuits. The coverage rate of FCT testing can reach 100%, which can cover the testing content of ICT.
2.Why has ICT testing disappeared?
• High cost:
The cost of ICT fixtures includes development costs, maintenance costs, warehousing costs, and usage costs.
20 years ago, ICT technology had a fixed needle tray, which could be used for all projects on a unified platform. For example, there were international standards for computer motherboard types: ATX, BTX. A set of testing fixtures can be used until it is scrapped.
Today, each PCBA has its own pattern, without any commonality. The upper and lower needle plates need to be developed separately, customized, and specific testing programs need to be written, which is very expensive. After the development of the needle tray project, it was left in the warehouse for dust disposal, becoming an idle storage cost.
The maintenance cost is high, and the ICT testing needle tray is composed of many gold-plated probes. Prolonged use of the probes may cause problems such as needle jamming, breakage, and insufficient elasticity. If not replaced, the needle jamming probes are prone to puncture the PCBA, resulting in PCBA scrap. Broken needles and insufficient elasticity can result in unstable test results.
ICT testing requires reserving test points on the PCBA. With the current small size of the PCBA, reserving test points will increase the design volume of the PCBA and increase costs.
3.FCT has replaced ICT testing.
FCT stands for Functional Circuit Test.
By writing FCT testing programs, taking mobile phone products as an example:
Step 1: Power on the PCBA and conduct a current test. The static standard current is 3mA and the current is 0mA. If the power circuit of the PCBA is not working properly and exceeds 3mA, it is considered that there is leakage current in the PCBA.
Step 2: Power on current test, static current is normally equal to 3mA, perform the first power on, and the basic circuit (BF) starts to power on, including CPU, memory, and flash memory. If the standard current is set to 500mA, and it is lower than 500mA, it indicates that BF has problems such as empty welding and is not working properly. If it is greater than 500mA, it is considered that there is a short circuit in the BF circuit.
Step 3: BF current is equal to 500mA, programming software cannot be programmed, BF circuit has a fault.
Step 4: Software burning is completed, power on current test is conducted, and the standard value is set to 2A. If it is greater than 2A, there is a short circuit fault in the functional module that needs to be turned on by the software. Less than 2A, there is protection or open circuit in the circuit that requires software control.
Step 5: Conduct functional testing on software controlled functional circuits.
At this point, FCT testing has ended, replacing ICT testing.
How to do PCB design
ICT(In-circuit Test) Online test process sharing
Related Article
