As the carrier with a hub for a variety of signal transmission circuit components , PCB has become the most important and critical part of the electronic information products , the quality and reliability of its quality determines the level of quality and reliability of the whole device. However, due to technical and cost reasons , PCB of a large number of failures occurred in the production and application process .
Then they would have to use some common failure analysis techniques. PCB between the main structural features and failure mode , this article will focus on nine for PCB failure analysis techniques, including : visual inspection , X-ray fluoroscopy , optical biopsy analysis, thermal analysis, photoelectron spectroscopy , which was micro- infrared analysis , scanning electron microscopy and X -ray spectroscopy analysis. Microsection analysis which belongs destructive analysis techniques , by using these two techniques , the sample destroyed, and can not be restored ; addition, as the sample preparation requirements may SEM and X- ray analysis is sometimes needed partial destruction of the sample . In addition, the course of the analysis may also be due to the failure of the need to locate and verify the cause of failure and may require the use of terms such as heat stress, electrical properties , weldability test and trial size measurement technique described here is not specifically .
1 . Visual inspection Visual inspection is visual or use some simple instruments, such as stereo microscope , metallurgical microscope or magnifying glass and other tools to check the appearance of the PCB , the failure to find evidence related to the site and the main role is to locate and determine the initial failure of the PCB failure mode. Visual inspection of the main PCB contamination inspection , the corrosion , the location of the explosion panel , and the failure of regularity of the circuit wiring , the case of a batch or individual that is not always concentrate in a certain area and the like. In addition , there are many failures PCB PCBA is assembled after the discovery , the assembly process is not used , and process failures caused by the impact of materials also need to carefully check the features of the failure zone.
2.X -ray fluoroscopy for some to not pass a visual inspection of the site and via internal PCB and other internal defects , had to use the X-ray system to check. X-ray system is the use of different materials in different material thicknesses or densities on different principles of X-ray absorption or transmittance to imaging. The technique used to examine more internal PCBA solder defects , locate defects inside the through-hole solder defects and high-density packaging of BGA or CSP devices. Current industrial X -ray apparatus can achieve a resolution of microns , and is two-dimensional to three-dimensional imaging device changes , and even has five dimensions (5D) of the apparatus for inspection of the package, but the X- 5D ray systems are very expensive , very few in the industry have practical applications.
3 slices analysis section analysis is through sampling , mosaic , slicing , polishing , corrosion, observe a series of measures and steps to obtain cross-sectional structure of the PCB process . Can be reflected PCB ( through hole plating , etc. ) the quality of the microstructure of a wealth of information , providing a good basis for further improvement of the quality of the analysis by the slice . However, this method is destructive Once sliced , the sample is bound to be destroyed ; while demanding that the sample preparation method , sample preparation and longer time-consuming , requires trained technicians to complete. Slicing operation process requires detailed , reference standard IPC-TM-650 2.1.1 Process IPC-MS-810 and IPC be predetermined .
