1. Explain the process of electronic hardware design, including hardware requirements specification, schematic design, PCB design, PCB prototyping, PCB manufacturing, UT (ultrasonic testing), and integration testing, among others.
2. In the PCB fabrication and manufacturing stages, to ensure the production quality of the PCB, manufacturers typically employ a variety of detection methods to identify different PCB defects during the production process.
**7 Commonly Used Inspection Methods for PCB Boards**
1. **Manual Visual Inspection of PCB Boards**
Using a magnifying glass or a calibrated microscope, the operator visually inspects the PCB board to determine its quality and whether any corrective action is needed. This is the most traditional detection method. However, with the increase in PCB production and the reduction in wire spacing and component volume, this method has become less feasible.
**Advantages:** Low budget cost, no test fixtures required.
**Disadvantages:** Subject to human error, high long-term costs, discontinuous defect detection, difficulty in data collection, etc.
2. **PCB Board Online Test**
This method identifies manufacturing defects and tests analog, digital, and mixed-signal components through electrical performance testing to ensure they meet specifications. Various testing methods include bed-of-needle testers and flying probe testers.
**Advantages:** Low cost per board, strong digital and functional testing capabilities, fast and thorough short-circuit and open-circuit testing, firmware programming, high defect coverage, and easy programming.
**Disadvantages:** Requires test fixtures, programming and debugging time, high cost of making fixtures, and complexity in use.
3. **PCB Board Function Test**
The functional system test uses specialized equipment at the mid-stage and end of the production line to conduct comprehensive testing of the circuit board’s functional modules to confirm its quality. This method, one of the earliest automatic testing principles, can be performed with various equipment on specific boards or units. Types include final product testing, latest physical model, and stacked testing. However, functional testing usually lacks detailed data for process improvement and requires specialized equipment and custom test procedures. Writing functional test programs is complex, making this method unsuitable for most production lines.
4. **Automatic Optical Inspection (AOI)**
Also known as automatic visual inspection, AOI utilizes optical principles along with image analysis, computer technology, and automatic control to detect and address defects in circuit board production. It is a modern method for identifying manufacturing defects and is typically used before and after reflow and before electrical testing to enhance the pass rate of these tests. The cost of correcting defects at this stage is significantly lower compared to after final testing, often more than ten times cheaper.
5. **Automatic X-ray Inspection**
This method uses X-ray absorption rate differences to view parts and detect defects. It is mainly used to identify issues such as bridging, missing pieces, and poor alignment caused by ultra-fine pitch and high-density circuit boards and assembly processes. Additionally, its tomographic imaging technology can detect internal defects in IC chips. Currently, it is the only method to test the soldering quality of ball grid arrays and blocked solder balls.
**Advantages:** Detects BGA welding quality and embedded component issues, no fixture costs.
**Disadvantages:** Slow speed, high failure rate, difficulty in detecting reworked solder joints, high cost, and long program development time.
6. **Laser Detection System**
This is a cutting-edge PCB testing technology. It scans the printed board with a laser beam, collects measurement data, and compares the actual values to preset limits. This technology has been proven effective on bare boards and is being evaluated for use in assembly board testing, with sufficient speed for mass production lines.
**Advantages:** Fast output, no fixture or visual non-covered access required.
**Disadvantages:** High initial cost, numerous maintenance and usage issues.
7. **Size Detection**
Using a two-dimensional image measuring instrument, this method measures dimensions such as hole position, length, width, and other features. Because PCBs are small, thin, and flexible, contact measurements can easily cause deformation and inaccuracies. The two-dimensional image measuring instrument has become the preferred tool for high-precision size measurement.
Different inspection methods have their own advantages and disadvantages. Manufacturers select appropriate inspection methods based on PCB board types, complexity, defects, and other specific conditions to ensure PCB quality.
**Interesting Knowledge**
Some people only learn that a green board is called a PCB after attending university. In reality, not all PCBs are green; they can also be black, purple, or other colors. The green color comes from a “green oil layer,” also known as a “solder mask,” which protects the circuit and prevents short circuits.
2. In the PCB fabrication and manufacturing stages, to ensure the production quality of the PCB, manufacturers typically employ a variety of detection methods to identify different PCB defects during the production process.
**7 Commonly Used Inspection Methods for PCB Boards**
1. **Manual Visual Inspection of PCB Boards**
Using a magnifying glass or a calibrated microscope, the operator visually inspects the PCB board to determine its quality and whether any corrective action is needed. This is the most traditional detection method. However, with the increase in PCB production and the reduction in wire spacing and component volume, this method has become less feasible.
**Advantages:** Low budget cost, no test fixtures required.
**Disadvantages:** Subject to human error, high long-term costs, discontinuous defect detection, difficulty in data collection, etc.
2. **PCB Board Online Test**
This method identifies manufacturing defects and tests analog, digital, and mixed-signal components through electrical performance testing to ensure they meet specifications. Various testing methods include bed-of-needle testers and flying probe testers.
**Advantages:** Low cost per board, strong digital and functional testing capabilities, fast and thorough short-circuit and open-circuit testing, firmware programming, high defect coverage, and easy programming.
**Disadvantages:** Requires test fixtures, programming and debugging time, high cost of making fixtures, and complexity in use.
3. **PCB Board Function Test**
The functional system test uses specialized equipment at the mid-stage and end of the production line to conduct comprehensive testing of the circuit board’s functional modules to confirm its quality. This method, one of the earliest automatic testing principles, can be performed with various equipment on specific boards or units. Types include final product testing, latest physical model, and stacked testing. However, functional testing usually lacks detailed data for process improvement and requires specialized equipment and custom test procedures. Writing functional test programs is complex, making this method unsuitable for most production lines.
4. **Automatic Optical Inspection (AOI)**
Also known as automatic visual inspection, AOI utilizes optical principles along with image analysis, computer technology, and automatic control to detect and address defects in circuit board production. It is a modern method for identifying manufacturing defects and is typically used before and after reflow and before electrical testing to enhance the pass rate of these tests. The cost of correcting defects at this stage is significantly lower compared to after final testing, often more than ten times cheaper.
5. **Automatic X-ray Inspection**
This method uses X-ray absorption rate differences to view parts and detect defects. It is mainly used to identify issues such as bridging, missing pieces, and poor alignment caused by ultra-fine pitch and high-density circuit boards and assembly processes. Additionally, its tomographic imaging technology can detect internal defects in IC chips. Currently, it is the only method to test the soldering quality of ball grid arrays and blocked solder balls.
**Advantages:** Detects BGA welding quality and embedded component issues, no fixture costs.
**Disadvantages:** Slow speed, high failure rate, difficulty in detecting reworked solder joints, high cost, and long program development time.
6. **Laser Detection System**
This is a cutting-edge PCB testing technology. It scans the printed board with a laser beam, collects measurement data, and compares the actual values to preset limits. This technology has been proven effective on bare boards and is being evaluated for use in assembly board testing, with sufficient speed for mass production lines.
**Advantages:** Fast output, no fixture or visual non-covered access required.
**Disadvantages:** High initial cost, numerous maintenance and usage issues.
7. **Size Detection**
Using a two-dimensional image measuring instrument, this method measures dimensions such as hole position, length, width, and other features. Because PCBs are small, thin, and flexible, contact measurements can easily cause deformation and inaccuracies. The two-dimensional image measuring instrument has become the preferred tool for high-precision size measurement.
Different inspection methods have their own advantages and disadvantages. Manufacturers select appropriate inspection methods based on PCB board types, complexity, defects, and other specific conditions to ensure PCB quality.
**Interesting Knowledge**
Some people only learn that a green board is called a PCB after attending university. In reality, not all PCBs are green; they can also be black, purple, or other colors. The green color comes from a “green oil layer,” also known as a “solder mask,” which protects the circuit and prevents short circuits.
