Assembly test technology
At present in the electronic assembly and testing technology used in the measurement field are commonly used with manual visual inspection (Manual Visual Inspection, referred to as MVI), online test (In-Circuit Tester, referred to as ICT), automatic optical test (Automatic Optical Inspection, referred to as AOI), the automatic X ray test (Automatic X-ray Inspection, referred to as AXI), function test (Functional Tester, referred to as FT). Due to the complexity of the electronic assembly industry, it is difficult to define which methods are necessary for the assembly industry, and which ones are not needed. The application areas and testing methods of each test technology are different.
First, testing techniques are introduced
1. Automatic optical inspection AOI (Automatic, Optical, Inspection)
2, process tracking (Process tracking).
3, online tester ICT (In-circuit tester)
4, automatic X ray inspection AXI (Automatic X-ray Inspection)
In 5, the function test (Functional Tester)
Two, test technology comparison
1, ICT can effectively find various defects and faults in the process of SMT assembly, but it can not evaluate the performance of the whole circuit board system at clock speed. ICT test is the most commonly used testing method in the production process, which has the advantages of strong fault ability and fast test speed. This technology is very convenient and quick for manufacturers of large quantities and products.
2, the function test can test whether the entire system can achieve the design goal, it will be tested on the circuit board unit as a function of body, provide the input signal of the output signal is detected according to the design requirements of the body function. This test is to ensure that the circuit board can work properly according to the design requirements. So the function test the most simple method, is a special line of electronic equipment will be assembled on the circuit board is connected to the appropriate equipment, and then add the voltage, if the normal operation of the equipment, circuit board that qualified. This method is simple and less investment, but it can not diagnose the fault automatically.
3, AOI technology does not need the needle bed, in a computer program under the drive of regional automatic scanning PCB camera, image acquisition, compare the parameters of solder joint and qualified in the test database, through image processing, check out the PCB defect. Very short test procedures, development time and flexibility are the biggest advantages of AOI. AOI in addition to check out the defect inspection cannot be found, AOI can make the quality of each process in the production process and defects type etc. the collection, feedback, analysis and management personnel for process control. However, AOI can not detect circuit errors, and can not detect invisible solder joints. And we found that AOI test technology requires higher testing conditions.
4, AXI technology is a relatively mature testing technology, and its coverage rate of process defects is very high, usually more than 97%. The process defects generally account for 80%-90% of the total defects and check the invisible solder joints, but the AXI technology can not test the defects and faults of the electrical performance of the circuit. Nevertheless, the application prospects of AXI technology in the electronic communications industry are still promising.
Because each technique compensates for the disadvantages of another technology: from the point of view of combining AXI technology with ICT technology, on the one hand, X rays mainly focus on the quality of solder joints. It determines whether the component exists, but does not verify that the component is correct and that the direction and value are correct. On the other hand, ICT can determine the direction and value of the component, but it can not determine whether the welding point is acceptable, especially the solder joints at the bottom of the package, such as BGA, CSP and so on. It should be noted that with the development of AXI technology, AXI systems and ICT systems can "talk to each other" at the moment, and this technology, called AwareTest, can eliminate duplicate testing between the two. By reducing the excess test coverage of ICT/AXI, the contact number of ICT can be greatly reduced. This simplified ICT test only the original test points 30% can maintain the current high test coverage, and reduce the ICT test points can shorten the test time and speed up the ICT ICT programming and programming costs and reduce ICT fixture. In the past two or three years, the combined test technology, especially the AXI/ICT combination testing of complex circuit board have a phenomenal growth, but the growth rate is accelerating, as more industry leading manufacturers aware of the advantages of this technology and will be put into use.