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PCB coating reliability and failure analysis

date:2021-07-09 17:38:36

With the development of electronic design in the direction of lightness and thinness, the high-density integration (HDI) technology in the PCB manufacturing process makes the terminal product design more miniaturized, while meeting the requirements of electronic performance and efficiency. HDI is currently widely used in mobile phones, digital, automotive electronics and other products. HDI blind hole bottom cracks and other abnormalities are one of the reliability problems of high-density interconnect printed circuit boards. There are many influencing factors and are not easy to be detected during the manufacturing process. The industry calls them typical gray defects, which are often after the terminal is installed. It was discovered that quality problems occurred, which led to large claims.

Jinjian laboratory is equipped with aging test equipment such as thermal shock, reflow test, mechanical grinding, argon ion polishing, FIB ion beam and other sample preparation methods, scanning electron microscope/transmission electron microscope, EDS energy spectrum and other analytical methods. For customers such as PCB board factories, syrup manufacturers, etc., we can provide failure analysis of coating open circuit, coating crack, coating cavity, columnar crystal, hole wall separation, etc.; reliability analysis of thermal shock, reflow soldering, coating crystallization, coating coverage, etc.

01. Hot and cold shock

The Jinjian laboratory tests the thermal shock of PCB boards and detects resistance changes. Argon ion polishing or FIB cutting can be used to observe the cracks between the plating layers, the plating layer open circuit, the separation of the hole wall and other undesirable defects. It is a process improvement for the PCB board factory. Point out the direction.

FIB-SEM observation of blind hole bottom crack abnormality after hot and cold impact of blind hole coating

02. Reflow soldering test

Jinjian laboratory reflow soldering simulates SMT and rework conditions, which can effectively test the thermal reliability of the coating, and can quickly test whether the coating has defects such as poor adhesion and cracking of the coating, and analyze the defects.

03. Coating morphology and crystallization

After being polished by argon ion in the Jinjian laboratory, the field emission electron microscope can observe the morphology of different coatings, and can intuitively judge whether the copper coating has "columnar crystals" and other crystalline states that seriously affect the thermal reliability of the coating. It can also be observed whether there are "voids", "cracks" and other abnormalities that are not easy to monitor between different coatings.

Through-hole observation of micro-voids between the copper layer and the electroplating layer, the electroplating layer is normally crystalline

04. Coating coverage

As the most critical process for the conduction in the hole, the copper layer has a thickness of about 0.3-0.5μm. Conventional backlight coverage can only be qualitatively observed for the overall coverage level. When there is an abnormality such as a hole without copper, it is often impossible to infer the backlight level. Abnormal sources, such as observing the coverage and thickness in the hole after mechanical polishing, the copper layer is damaged, and the state of the copper layer cannot be accurately determined. Jinjian Laboratory can observe the coverage of the copper layer in the glass fiber and resin position through the field emission electron microscope after argon ion polishing, which can provide a basis for judging the difference in copper coverage of PCB factory, and can also provide a reference for the research and development stage of syrup manufacturers.

After blind hole ion polishing, observe that the copper layer is well covered on the resin part and the glass fiber part



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