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As the labor cost is getting higher and higher and the quality requirements are getting higher and higher, the way of testing the circuit board has also changed. Let me introduce the PCBA function test in the PCBA test.
Introduce PCBA function test, PCBA test content-PCBA function test
The current PCBA function tests are mainly divided into the following types:
1. Manual test fixture
The manual test fixture uses Bakelite and Acrylic to make a needle board, draws out the input, output, and power supply of the board to be tested, uses artificial input to simulate the input, and artificially confirms whether the output is correct or not. It is characterized by low price, heavy use of manpower, slow testing efficiency, and there is no way to guarantee products with incomplete testing.
2. Single-chip control function test
Make clamp lock fixtures or pneumatic fixtures, and then lead the probes out. Then connect the input, output, and power supply to the circuit of the single-chip microcomputer, let the single-chip microcomputer automatically run the test program to simulate the input, and measure the correctness of the output. Its characteristics are moderate price, high test efficiency, good test quality, and less human intervention. But the versatility is not strong, generally only one machine model can be equipped with one fixture.
3. Computer test system
Use pneumatic or automated testing institutions on the production line to test the quality of products through computer control. It is characterized by relatively expensive price, fast test speed, no need for human intervention, and fully automatic test. Good versatility, similar products can be used universally, and the test is relatively comprehensive.
Next, the editor will introduce the content of the PCBA function test:
1. Power supply part test: Whether the power supply is working normally, test the voltage of each point-use a comparator or other.
2. Port (interface) test: Whether there is Short&Open, causing an exception.
3. IC module ICI/O read and write function test: Flash&EEPROM&CPU&SDRAM&LogicICetc.
4. Special function test (different circuit board requirements are inconsistent): If an infrared ray is provided, an external receiver is required.
The PCBA test depends on what test you are doing, ICT or FCT. Different test methods charge differently, because ICT equipment and tooling are relatively expensive. But ICT can give good test results and bring great benefits to PCBA processing.
Acceptable standard of tin bead size on PCBA board surface
Source: PCBA Editor: PCBA Processing Date: 2018-07-24 View: 3385
In the process of PCBA processing, some tin beads will inevitably remain on the surface of the PCBA board, and the industry will have an acceptable standard for the size and quantity of the tin beads on the PCBA board. The following is the acceptable standard of PCBA appearance inspection standard (abbreviated as national standard) for PCBA surface tin beads.
Acceptable standards for PCBA board tin beads:
1. The diameter of the tin bead does not exceed 0.13mm
2. The number of tin beads with a diameter of 0.05mm-0.13mm within the range of 600mm2 does not exceed 5 (single side)
3. The number of tin beads below 0.05 is not required
4. All tin beads must be wrapped by the flux and cannot be moved (the flux encapsulated to more than 1/2 of the height of the tin beads is judged to be pinched)
5. Tin beads did not reduce the electrical clearance of different network conductors to below 0.13mm
Note: Except for special control areas
PCBA board tin beads
Rejection criteria for tin beads:
Any non-compliance of the acceptance criteria is judged to be rejected.
Remark:
1. Special control area: tin beads visible under a 20x microscope are not allowed within 1mm around the capacitor pad on the differential signal line at the golden finger end
2. The existence of tin bead itself represents a process warning. SMT chip processing manufacturers should continuously improve the process to minimize the occurrence of tin bead.
The PCBA appearance inspection standard is one of the most basic standards for the acceptance of electronic products. According to different products and customer requirements, the acceptable requirements for tin beads will be different. Generally, it is based on the national standard and combined with customer requirements. To determine the standard.
