J Fail. Anal. and Preven.(2008)8: 524-532 Conclusions The comprehensive analysis on the two types of PCBs by both macroscopic and microscopic methods shows that cracking of the blind vias causes open-circuit faults the PCBs. the raw materials of the boards are acceptable, and there is also no noticeable delamination around the failure sections Improper locations of pads and blind vias are based or improper circuit design, and lead to high stresses and asymmetry deformations that generate cracking some weak joints once heated. Therefore, the design default is a primary cause for cracking of the blind vias The residue S appearing in the wall interface of the blind vias has a fatal effect on the structural integrity and deposition quality of the copper plating with a formation f Curs in the interface of copper grains. The structure of Curs can change with different temperatures, induc- ing an embrittlement intercrystalline fracture during SMT. Accordingly, the incomplete desmear is the predominant factor for failure of the vias An inappropriate reduction in thickness of type 2 PCB and together with the asymmetric configuration of compo- Gate Pos: 16ns width 88 n nents lead to excessive warpage and deformation of the ig tensile force or a bendi stress around pads linked with blind vias. However, under some conditions, cracking will occur in those weak connections of the vias. So. the unsuitable dimension design of the PCB is another potential risk of failure. 680069007000710072007007400750m Suggestions alax It is advised that the design of relative locations among Gate Pos: 9712ns width 62 ns 61 pads and components should be optimized through simulation (FEM) and bench test inspection on the wall of the blind vias should be emphasized before plating to provide a clean wall surface. (d) The best thickness of the board should be simulated 4009500960097009800 hrough FEM and essential property experiments to Fig 9 SAM inspection of the bare board before and after therma ensure adequate stiffness of the substrate cycle test. (a)Before testing.(b) After testing.(e) Spectra before sting.(d) Spectra after testin Acknowledgment The financial support by both the Shanghai Leading Academic Discipline Project(Project Number: B113) and China Circuit Technology(Shantou) Corporation (CCTC)(Grant with blind vias, leading to a cracking in some weak con- SGH2021073)is acknowledged. nections of different layers in the In summary, both the improper location design of pads and blind vias and the incomplete desmear process before References copper plating constitute the main causes of the cracking The inappropriate dimension design of type 2 PCB I. Richard, S, Jamal, H, Prado, E: High-density PWB microvia liability for space application. Aerosp. Conf. 3-10 March another potential risk of failure 2007,正EE,Pp.l-8(2007 2 Springerwith blind vias, leading to a cracking in some weak con￾nections of different layers in the vias. In summary, both the improper location design of pads and blind vias and the incomplete desmear process before copper plating constitute the main causes of the cracking. The inappropriate dimension design of type 2 PCB is another potential risk of failure. Conclusions • The comprehensive analysis on the two types of PCBs by both macroscopic and microscopic methods shows that cracking of the blind vias causes open-circuit faults in the PCBs. The raw materials of the boards are acceptable, and there is also no noticeable delamination around the failure sections. • Improper locations of pads and blind vias are based on improper circuit design, and lead to high stresses and asymmetry deformations that generate cracking in some weak joints once heated. Therefore, the design default is a primary cause for cracking of the blind vias. • The residue S appearing in the wall interface of the blind vias has a fatal effect on the structural integrity and deposition quality of the copper plating with a formation of CuxS in the interface of copper grains. The structure of CuxS can change with different temperatures, induc￾ing an embrittlement intercrystalline fracture during SMT. Accordingly, the incomplete desmear is the predominant factor for failure of the vias. • An inappropriate reduction in thickness of type 2 PCB and together with the asymmetric configuration of compo￾nents lead to excessive warpage and deformation of the board, which will generate a big tensile force or a bending stress around pads linked with blind vias. However, under some conditions, cracking will occur in those weak connections of the vias. So, the unsuitable dimension design of the PCB is another potential risk of failure. Suggestions • It is advised that the design of relative locations among pads and components should be optimized through simulation testing including finite element methods (FEM) and bench test. • Meanwhile, the quality inspection on the wall of the blind vias should be emphasized before plating to provide a clean wall surface. • The best thickness of the board should be simulated through FEM and essential property experiments to ensure adequate stiffness of the substrate. Acknowledgment The financial support by both the Shanghai Leading Academic Discipline Project (Project Number: B113) and China Circuit Technology (Shantou) Corporation (CCTC) (Grant SGH2021073) is acknowledged. References 1. Richard, S., Jamal, H., Prado, E.: High-density PWB microvia reliability for space application. Aerosp. Conf. 3–10 March, 2007, IEEE, pp. 1–8 (2007) Fig. 9 SAM inspection of the bare board before and after thermal cycle test. (a) Before testing. (b) After testing. (c) Spectra before testing. (d) Spectra after testing J Fail. Anal. and Preven. (2008) 8:524–532 531 123