FCT - functional circuit test means providing a simulated running environment (excitation and load) to a UUT, making it functional in different design situations. Then, getting a range of different design situations to improve the UUT function. In short, it is suitable to load to the UUT, and the UUT output shows whether or not the board fits the design; it is called the PCBA functional test.
What’s the difference between ICT test devices and FCT fixture?
ICT test device mainly tests the performance of all components. The aim is to check if there are problems or defects for boards in production. The test object is a semi-finished product, but the FCT fixture test object is a PCBA functional test. FCT fixture mainly to simulate the product working environment to verify the function of boards during working conditions. ICT test device and FCT fixture both are online tests.
Introduction to FCT Testing System
FCT refers to the functional test in which PCBA connects the power. It includes voltage, current, power, power factors, frequency, duty ratio, position determination, LED lighting, LED color, sound recognition, temperature measurement and control, pressure measurement and control, precision micro motion control, FLASH, and EEPROM online programming. It refers to the operating environment (excitation and load) that provides simulation against the UUT.
2. Functional Test Classification
1. For different control mode
(1）Manually control functional tests
(2）Semi-automatic control function test
(3）Fully automatic control function test
The earliest function tests are mainly automatic and semi-automatic. In order to simplify the design and reduce production costs, manual and semi-automatic are still used. With the technology development, to save production costs and improve production efficiency, most of the functional tests are fully automated.
2. For different controller
(1) MCU controller
(2) Embedded CPU controller
(3) PC controller
MCU controller is an embedded control, MCU and embedded CPU controller characteristics as below
(1) Test speed is fast
(2) Simple test steps
(3) Dedicated circuits and programs for data display and output
(4) Highly targeted test solution
(5) Easy to modify test software
PC controller is most widely used for FCT testing, and the main reasons are listed below:
- PC technology is already widely available
- PC pricesare lower
- The data output and file processing of the test results can be very convenient to achieve on the PC operating system
- The operation of the test software is intuitive
- Special test program development software
PLC control is a common FCT development mode, and the focus is to control the induction part. However, the measurement function is weak. This is because PLC is for professional industrial control.
3. The Composition of the Functional Test System
PCBA functional test is mainly divided into the following parts:
- System control center:The main parts of the full test system composed of PC, MCU, ARM, central processing. The primary functions are to control all test processes, record the contents and results of each step test, and create a final test result.
- Control executive:Control executive is composed mainly of I/O. It is the execution of logical actions during the testing process. The system builds various testing environments based on the testing function.
- Measurement part: The measurement part is mainly composed of a special measurement board and instrument. It mainly completes the collection of various analog or digital during the test process. It is also called data collection.
- Data processing and output: The purpose of the final test result is to figureout how to store and output the results data. It will be advantageous for us to control the PCBA quality effectively. This is the responsibility of data processing and output.
In the PCBA batch process, it is impossible to achieve 100% running status on the equipment and human operators. PCBA are good,so it requests all kinds of test equipment and test tools at the end of production. This leads to the other types of testing, such as ICT, AOI, X-Ray, Boundary Scan, to make sure all the circuit boards according to the design of various specifications and parameters.
FCT fixture Spec
1. FCT Fixture Definition：
FCT means providing a simulated running environment (excitation and load) to a UUT, making it functional in different design situations. Then, getting a range of different design situations to improve the UUT function. In short, it is suitable to load to the UUT, and the UUT output shows whether or not the board fits the design; it is called the PCBA functional test. FCT fixture is a fixture that simulates the finished PCBA.
The difference between ICT and FCT
ICT only tests if the PCBA is connected, short-circuited, LCP value, wrong orientation diode, and other semiconductor connections. The principle is to isolate other components then test a single or series-parallel group of components individually.
FCT is different; it is a functional test. It tests PCBA key components or output waveform through the relevant voltage or signal and determines if the values are within the acceptable range. Do not test against components. If the component fails, the functionality will be affected.
ICT has a universal tester. FCT can only be conducted according to the specific test requirements.
2. FCT Scope：
FCT fixture has electric/cylinder/manual quick clip, manual crank, and other mechanisms.
The materials can be imported bakelite, acrylic, aluminum alloy, iron, racing steel, or
fiberboard. They are then applied to the computer main board, LED lamp main board, LCD TV main board, communication equipment main board, and other electronic products. The different control modes include manual control function test, semi-automatic control function test, and fully automatic control function test.
Quick clip Retainer Manual crank Pneumatic
3. FCT Content：
FCT fixture production process：
3.1 FCT fixture raw material selection
3.2 FCT Fixture design work
3.3 FCT Fixture assembly and debugging
3.4 FCT Fixture inspection standard
3.5 FCT Fixture user caution
3.6 Fixture maintenance
4. FCT Accrual：
4.1 Production department is responsible for CNC programming, CNC processing, and FCT fixture assembly.
4.2 The quality department inspect it according to the ordering list and FCT inspection standards.
4.3 Purchase department purchase raw materials and ask suppliers to provide the material reports, ROHS, and other documents.
4.4 The sales department will assess and promote the customer design requirements to production and assign inspection personnel to complete the inspection.
4.5 Engineering department is responsible for FCT fixture test circuit installation and debugging.
5. Production specification：
5.1 How to choose FCT fixture raw material：
- Parts material of FCT fixture choose ：
|3||manual crank||steel plate|
|4||Pin board||Acrylic, bakelite|
|5||bearing||Imported plating rod|
- Test system selection：
According to the test board and test requirements, select relay control, embedded microcontroller control mode, PC control mode, and PLC control mode. Then select the corresponding components after the mode is determined.
5.2 FCT fixture design according to clients document：
- PCBA test document
- PCBA schematic
- PCB Gerber files
- Sample: Bare PCB, assembled PCBA like the picture:
5. Other tools will be used to load the device
5.2.1 FCT fixture structure design:
- Select the control model according to UUT and test request, then design the fixture structure like load board, press plate, connector model, etc.
- 2. The loading/pressing board of the fixture should be positioned appropriately to avoid damaging the test boardwhen testing the product.
- Fixture accurate positioning, and the docking of the connector should be smooth.
- 4. Reasonable fixture box layout,enough space for the assembly control system.
- Correctspacing for fixture interface position.
- Correct spacingfor optical fiber/MIC/SPK/SIM.
- The locking of the fixture box should adopt the way of case buckle or pressure buckle to facilitate maintenance and replacement of parts.
- The front of the fixture should be engraved with the name of the fixture: Song style, height 10mm, white color, middle position. Company LOGO, and date. Song body, 8mm height, white color, the bottom left corner position. Or paste the nameplate made by the company.
- Keyword should specify the purpose and function of each key and switch.
- Big bottom like: Emergency switch type, need to add white race steel protection. The height of the matchingsteel should not be lower than the highest point of switch bounce.
- 11.Function, lifetime, maneuverability, esthetic should be considered when design work. To achieve stable test and long service life, Beautiful appearance and humanized operation
- Fixture should use the green and yellow cable with length 80-100cm. One side is alligator clamps, and the other side is clamp-shaped terminals.
5.2.2 Test system design (software, hard software)
its system is mainly divided into the following parts No matter how to test the PCBA:
- System control center：
This part contains PC, MCU, PLC, and other central processor components. Its main role is to control the whole test process and each step of the test content for evaluation and test results. It is the brain of the whole test system.
In the control center, consider the test board function, cost, test efficiency, and other control center system selection.
- Control parts：
The control execution part comprises I/O components, induction, and execution mechanism of logical actions in the test process. The system builds a variety of testing environments to achieve the testing functions.
The control execution unit should be designed for safe use of the test board and can run reliably for an extended period.
- Parameter measurement part：
The measurement part is mainly composed of board instruments. It mainly completes the collection of various analog or digital data in the testing process.
- Data processing and output：
The final test result of each step and date storage should be in the data processing and output.
The results of data output are displayed visually and audibly. It will simplify the processing work of the facility operator.
5.3 FCT fixture assembly and debugging:
Structural partial assembly：
5.3. Non-functional acute angles should be chamfered R1 or 0.5×45°.
5.3.2. Black hexagonal socket screws are used for locking when using black bakelite, and stainless steel hexagonal socket screws are used for red dot wood and acrylic.
5.3.3. Each assembly step should be followed carefully and correctly to ensure the parallelism of the press board to the load board vertical board. This is to ensure the accuracy of the test fixture.
5.3.4. Select the correct test probe, test point normally is Pin ,Component pin using claw needle, if customers have special requirements can use other types of probe (round class). Probe contact 3.5mm-4.0mm, more test points can reduce the contact travel accordingly.
5.3.5.The positioning PIN is made of stainless steel, and the PIN head is processed into a ball shape, which prevents scratches to the test products.
5.3.6. Press bar to choose anti-static black steel bar, choose the flat press bar in the case of not hamper testing and collision, small position can be processed into a cone type
5.3.7. After assembly work it must debugging, correction point. The lettering on the panel is painted in a striking color for easy observation
5.3.8. Aquire spare parts for the components that can be easily damaged
Functional Test and Debugging：
1. Cable connection
- Fix and wire the circuit board and power module of the test system in the fixture box.
- Connect the power supply, pneumatic control, and external switch. Then install and fix.
- Connect the product test point and TP point of the test system according to the drawing, then fix and layout.
2. Prepare the work before connecting the power supply
- Confirm the power polarity and circuit are correct before connecting the power supply.
- Confirm each module of the system before connecting the power supply.
- Check the voltage is correct of each module before connecting the power supply.
3. hard software and software test together
- Check the test hard software power voltage is correct after the power supply is connected.
- Connect the DAQ cable and start software debugging.
- Check the network is correctand check for open short circuits before connecting the device. If any special TP point should be connected during the test, the software should detect the short circuit.
- The resistor and capacitor test value should be within a reasonable range before connectingthe device.
- Use an empty sample to test the board. The short-circuit products witherrorsare checked one by one.
- After confirmingthe short circuit, review the short circuit and pass the test.
- Test for few goods or bad onesunder the test debugging system model. Verify the test results are consistent with the actual product and revise the test standard if necessary.
4. Test standard of FCT fixture
4.1. Test good boards ten times and verify the fixture’s stability.
4.2. Use a good sample, repeat take few times, and verify the fixture's accurate location.
4.3. Verify the test result of the fixture and if all requirements are met.
4.4. Check the safety of the operation button, power supply, and pneumatic control parts.
4.5. Check fixture stability and protection, especially special parts, such as external optical fiber, MIC, automatic card insertion device, adapter plate fixing module, pressing plate needle module, and other special switching devices.
4.6. Check whether the appearance meets the requirements, for example, damage, apparent scratches, etc.
4.7. Check whether the fixture labeling is standard and the high-pressure part and the easy-to-clamp part are labeled.
4.8. Check whether the cooling fan is operating correctly.
4.9. Verify the press bar is correct.
4.10. Check the position of the high parts relative to the sky plate milling grooves.
4.11. Verify the load plate milling groove is correct and whether the unmilling groove will press the parts.
4.12. Probe Pin working well or not, no Skew, no wipe
4.13. The tightness of the casing is moderate, without any loosening phenomenon, and the casing height is correct or not (down test compression is 2/3, up-test compression is 1/3~1/2)
4.14. whether the probe type is correct and whether the loading plate obstructs probe activity
4.15. Whether the clockwise machine is smooth and has no noise
4.16. Whether spare parts meet requirements and prepare the document according to the product list：
- Customized functional test system (including tester and fixture).
- Function test system operation manual.
- Function test system maintenance manual.
- Test board data provided by the customer (software program, drawings, etc.).
- Bare PCB and new sample.
- All other items are provided by the customer (some included in the test system).
- Sufficient spare parts.
5. Notes for the use of FCT fixture：
- Check whether the input voltage meets the requirements when using the FCT fixture.
- FCT fixtures should not be superimposed on each other. They should be placed separately on the shelves to avoid heavy objects.
- Check whether the air pressure in the appropriate range (4-6kg/cm2), the test program and fixture are correct, and the fixture arrangement is connected in order.
- Avoid contact with strong acid and alkali to prolong the service life of the fixture.
- When inserting any test periphery, be sure to turn off the test fixture power to avoid damage to the test periphery. Use both hands to hold the two sides of the CPU. Align the CPU slot and insert the CPU's golden finger from top to bottom. On the contrary, in selecting the application of both hands from the bottom up the CPU out.
- When inserting the SD card, please be careful of the orientation. To eject the memory card, press the memory card first and then let the memory card eject itself.
- Please be careful the cooling fan is running. Otherwise will damage the test system
- Please pay attention to the display during the VFA test and make sure it is the correct paint and color. Also, please pay attention to whether the sound emitted by the buzzer on the board is normal.
- Maintenance of FCT fixture：
- The workers should wash the test probe every seven days to make sure the test probe is clean.
- The workers should maintain the test probe, test cylinder, and electric control parts every three months.
- Fixture should be free of dust. Add lubricating oil to the moving parts regularly.
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