Causes, Characterization and Mitigation of Non Wet Open Defects for Area Array Components
Authors: Dudi Amir, Satyajit Walwadkar, Srinivasa Aravamudhan, Lilia May and Kok Kwan Tang Company: Intel Corporation Date Published: 4/17/2013
Abstract: There is an increase in the incidences of a SMT non-wet type of solder joint defect where the termination of an area array component does not solder to the printed circuit board (PCB) land. This defect is called Non Wet Open (NWO) and is a phenomenon recently detected in the industry after the surface mount assembly reflow process. This defect is hard to detect with conventional inspection techniques and is sometimes misconstrued as a pad wetting issue or no paste printed. This paper will report on the NWO defect in area array components such as Solder Grid Array (SGA) and Flip Chip Ball Grid Array (FCBGA) packages observed after surface mount assembly. A previous study has touched some certain aspects of this defect . This paper will define the NWO defect, and describe its formation mechanism and the critical SMT materials and process factors that can influence it. The paper will also document best practices during the surface mount assembly process to mitigate the defect and optimize the SMT process for high yields. Finally, the paper will compare the NWO defect to the better known and widely characterized head- -on-pillow (HoP) defect.