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8 SMT Magazine • November 2016 by Stephen Las Marias I-CONNECT007 The Impact of Vias on PCB Assembly The continuing trend towards smaller and smaller devices with even more functionality has resulted in a dramatic reduction in the size of components, silicon packages, and the PCBs themselves. Component technologies such as BGAs and CSPs have challenged PCB manufac- turing technologies due to the number of in- put/output connections and tighter and tighter pitches associated with these devices. Don't for- get the costs associated with fabrication. Via technology—including blind and bur- ied—has been one of the solutions to address the miniaturization and component density challenges in current electronic assemblies. Ad- vantages include improved electrical and ther- mal performance; increased wiring density; space-saving in PCBs; placement of even more chips and components in PCBs; and finally, smaller PCBs. However, vias are not without their own set of challenges. In our recent survey that focused on vias, respondents mentioned challenges such as impedance matching, routing, place- ment of vias, minimum size limitations, aspect ratio, and the limitations for the PCB manufac- turer. One respondent commented: "In-pad vias in thermal pads and regular lands often cause processing issues. If they are tented, trapped res- idues and 'popping' are issues. If they are not tented, solder thieving is an issue. We have also E DITOR'S NOTE

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