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PCBA testing and methods

PCB-testing-and-methods

With the continuous development of the electronics industry, the PCBA industry has increasingly high requirements for long-term reliability of products. Besides, the whole PCBA process is very complex that from PCB design, component and material IQC, SMT and DIP assembly, PABA testing and so on.

Among them, the PCBA test at the end of the production process is an essential part to strictly control the quality and determines the effectiveness of the finished product. PCBA test refers to the test of the pressure, IC burn-in, voltage, current, line on-off on the PCBA board.

What are the main tests in PCBA?

According to different products and customer requirements, PCBA test will be different, PCBA test mainly includes ICT online test, FCT function test, aging test, fatigue test, test in harsh environment.

ICT

Ict-testingICT (In-Circuit Test System) measures resistance, capacitance, inductance, diode, IC protection diode test and other components through the probe touching the test points of the PCB layout. According to the statistics, Common defects in assembly include missing parts, less tin, solder balling (solder beading), solder bridge (short circuit), inveracious soldering (empty soldering), etc., accounting for more than 90%.

Therefore, the purpose of all test technologies is to detect those assembly defects quickly. At the same time, it can perform functional testing on functional devices like Transistor-Transistor-Logic (TTL), diode, resistance, open-relay , and programming of IC programs. ICT can greatly improve production efficiency and reduce production costs for manufacturers because it is accurate located the defects. Therefore, it becomes a standard and popular test method.

FCT

PCBA-FCTFCT (functional circuit test) is mainly used in PCB function test. The system equipment consists of conveyor belt line, PCB positioning mechanism, needle bed, vision system and electronic control system. The automatic FCT can test up to 8 PCBs at the same time.

FCT consists of a test station, which is a function test station. The whole machine is designed according to modularization, and different test functions are independent into a module, which is convenient for subsequent maintenance and inspection. future upgrades. The FCT unmanned test system allows the factory to reduce staff and increase efficiency.

Advantages of FCT functional test system:
● Fast mold change, stable test system
● Advanced intelligent quality management function
● Convenient visual analysis tools
● Single-layer, double-layer online test
● Multiple units in parallel, serial online test

Burn-in test

PCBA-burn-in-testingAfter the PCBA has undergone SMT and DIP process, it generally needs an aging test before it can be delivered to the customer, which can improve the quality of the PCBA and avoid quality problems when it is delivered to the customer, and bringing more after-sales. Therefore, the burn-in test is an important quality assurance behavior in PCBA manufacturing.

The PCBA aging test generally simulates the external environment to test the finished PCBA. It simulates the daily use environment of the PCB product, for example high temperature, low temperature, high and temperature changes, and under electrical power and continuous use. Then It will also expose PCBA defects, such as poor welding, component parameters Mismatches, as well as faults caused during debugging, which will play a role in stabilizing parameters for defect-free PCBA boards.

Fatigue test

Fatigue_testFirstly, people need to conduct random sampling inspection of the PCBA board, and perform high-frequency and long-term operation of the function, then observe whether there are defects, and estimate the rate of failure of product, which can feedback the working condition of the PCBA board in the electronic product.

Testing in Harsh Environments

Testing-in-Harsh_EnvironmentsThe PCBA board is placed in harsh and extreme environments, such as high temperature, severe cold, and falling. The reliability of the PCBA board is calculated through the test results. This test is not commonly used and mainly used for military industry, off-road vehicles, special equipment and other products under harsh working conditions. Test items include temperature, humidity, drop, splash, vibration limit.

Common test methods for PCBA

Manual testing

Manual_testingManual testing is one of the most widely used in-circuit testing methods to confirm component placement on a PCB through human vision and comparison. However, with the increase of production and the shrinking of circuit boards and components, some functional defects are not easy to be found, and this method is increasingly unsuitable. Low upfront cost and no test fixtures are its main advantages.

Meantime, it also has a lot of shortcomings, for example,it’s difficult to collect the data, defects are not continuous, besides, visual and some electrical testings are limited which will spend a lot time and cost.

AOI

PCBA testing-AOIAOI, meaning automated optical inspection,whose principle is to detect common defects in welding production. During it works, the machine automatically scans the PCB through the camera and collects images using high-speed and high-precision visual processing technology. , then compares the tested solder joints with the qualified parameters in the database. After image processing, the defects on the PCB are inspected and displayed or marked on the display.

Find and eliminate errors early in the assembly process for good process control by using AOI as a defect reduction tool. Early detection of defects will avoid sending bad boards to subsequent assembly stages, besides, AOI will reduce repair costs and will avoid scrapping non-repairable boards.

By using AOI as a defect detection tool, manufacturers can find and eliminate defects early in the assembly process to achieve good process control, and can avoid sending bad boards to subsequent assembly processes, which will waste cost and time. In addition , AOI can reduce repair costs and avoid scrapping non-repairable boards.

Flying probe test

flying-probe-testingFlying probe testing is the latest solution to some of the major problems in electrical testing.Flying probe testers check for shorts, opens and component values. A camera was also used on the flying probe test to help find missing components. Use a camera to inspect well-oriented component shapes, such as polar capacitors. With probe positioning accuracy and repeatability in the range of 5-15 microns, flying probe testers can precisely probe UUT.

Flying probe testing solves a number of existing problems seen in PCB assembly: such as test development cycles that can be as long as 4-6 weeks; fixture development costs of approximately $10,000-$50,000; inability to economically test low volume production; and Prototype assemblies cannot be quickly tested.

Flying probe testing is an invaluable production resource because of the ability to have close contact to the shielded UUT and the ability to bring new products to market faster. Also, since an experienced test development engineer is not required, the system also has the benefits of saving manpower and time.

MDA

MDA (Manufacturing Defect Analyzer) is a great tool for diagnosing manufacturing defects in a high-volume/low-mix environment.Because most defects in PCBA process are connection issues, MDA is mainly to measure continuity of wires and components, like resistors, capacitors, and transistors. Besides, detection of integrated circuits can also be achieved using protection diodes to indicate proper component placement.

Common equipment in PCBA testing

ICT

ICT, In-Circuit Test, is a standard test method to check manufacturing defects and defective components by testing the electrical properties and electrical connections of online components. It is used to test each component on an assembled circuit board like open and short circuit and It is easy to operate and can locate faults quickly and accurately without fixtures and a long time of program development.

The world’s major ICT automatic test equipment manufacturers mainly include Agilent Technologies (United States), Teradyne (United States), Check Sum (United States), AEROFLEX (United States), Hioki (Japan), Takaya (Japan), Tescon (Japan), Okano (Japan), Shixin (Taiwan), SRC Galaxy, Rohde & Schwarz, Scorpion, Shindenski, SPEA, Tecnost -MTI, Testronics, WK Test, Schuhll, Viper, TTI and other brands.

FCT

Functional test (FCT) generally refers to the test after the PCBA is powered on, mainly including voltage, current, power, frequency, brightness and color, voice, temperature measurement, pressure measurement, motion control , FLASH and EEPROM burning and other test items of semi-finished products or finished products. Nowadays, the control method of FCT test fixture is mainly automatic and its test speed of this control method is very fast and the test data is accurate.

In terms of structure, the FCT automatic test system is generally composed of measurement and control computer, test software, test circuit, test needle bed, mechanical transmission and other parts. the FCT system can be divided into three modes–manual,semi-automatic and fully control function test,which is classified according to the operation mode. Besides, according to different control methods, FCT can be divided into: embedded MCU control method, PLC-based control method, PC-based control method, etc.

Burn-in test

PCBA Burn-in testingGenerally, after the following aging test steps and standards, it is possible to detect whether a board is defective, and good products can be handed over to customers with confidence. Good products make customers rest assured, reduce repairs and after-sales, make manufacturers more trustworthy, and strengthen cooperation with customers.

What is the PCBA burn-in test standard?
■ Low temperature work: place the PCBA board at a temperature of -10±3℃ for 1h. Under this condition( rated load 187V and 253V), all programs should be powered on and run, which shows the program is correct.
■ High temperature work: After placing the PCBA board at 80±3℃/h, under this condition, with load 187V and 253V, power on and run all programs, and the programs should be correct.
■ High temperature and high humidity work: run the PCBA board under the conditions of temperature 65±3℃, humidity 90-95% for 48h, power on with rated load and run each program, each program should be correct

What is the method of PCBA burn-in test?
■ Put the PCBA board with ambient temperature into the thermal burn-in equipment. The temperature of all the equipment should be same, and the PCBA board should be in a running state.
■ Lower the equipment temperature to the specified value at a prescribed rate. When the temperature reaches a stable level, the PCBA board should be put into a low temperature condition for 2 hours.
■ Turn up the temperature of equipment to the specified temperature at a specified speed. When the temperature is stable, the PCBA board should be exposed to a high temperature condition for 2 hours.
■ Turn down the temperature in the equipment to room temperature at a specified rate, and repeat it continuously. Then we measure, observe and record condition of PCBA board according to the specified burn-in time.

Conclusion

PCBA-testingPCBA testing is an indispensable and important part to ensure the quality of product delivery. It determines the performance of the product, controls the quality of the product, reduces after-sales and repair rates, makes customers more trustworthy, and promotes win-win cooperation between enterprises and customers.

IBE was established in 2005 and is located in Shenzhen, China. The company currently has a factory area of 75,000 square meters in China, the United States, and Vietnam, 14 SMT production lines, 6 DIP lines and wave soldering lines, 4 product assembly production workshops, equipped with advanced and complete digital management system. IBE provides PCBA one-stop solution including PCBA processing services, SMT and DIP processing services, OEM electronic processing services, and ODM services.

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