BGA Fanout Routing Overview


Reading time ( words)

PCB developers are deluged with new challenges caused by increasing density and smaller components. Ball grid arrays (BGAs) create particular challenges during layout, with hundreds of connections in just a few square centimeters. Fortunately, designers now have options for addressing these issues.

Fanout and Escape Routing

Because of the density and distance from the connection points, only the two outermost rows of a BGA can be connected directly to surface circuit traces. All other terminals of the BGA cannot be connected in a direct path on the surface.

Fanout and escape routing is integrated in many PCB design systems to enable further connections. In fanout and escape routing, the two outermost rows, and all other rows of a BGA, are automatically connected to the center of the terminals via a short circuit trace that is executed at a 45° angle. This provides a blind via that forms a direct connection to the next signal layer. Routing can be executed on the next signal layer.

Using via-in-pad eliminates the need for the additional trace to the center of the connections, thereby creating additional space for circuit traces. Therefore, with via-in-pad, the through contact can be placed directly at the terminal of the BGA.

During circuit board manufacturing, these through contacts will be filled with a non-conducting medium and cured. Later, the ends are metallized, planarized, and also over-contacted. This makes the surface of the via flat and can be used the contacts of the BGA. This solution can be used for both stacked and staggered microvias and/or blind vias. IPC-4761 describes how via-in-pads, for example filled and capped vias (IPC-4761 Type VII), are prepared. Despite the higher manufacturing costs, via in pads will always be preferred, because of the higher integration density of BGAs and their lower inductance at high frequencies (signal quality).

To read this entire article, which appeared in the August 2018 issue of Design007 Magazine, click here.

Share




Suggested Items

I-Connect007 Editor’s Choice: Five Must-Reads for the Week

01/20/2023 | Andy Shaughnessy, Design007 Magazine
We’re in the middle of show season, and it certainly “shows.” Thank you very much. I’m here all week. Don’t forget to tip your wait staff. This week, we published a variety of articles, columns, and news items, and much of it centered on trade shows. Technical Editor Dan Feinberg brings us a report from CES 2023. IPC announced the winners of the Best Technical Paper awards for IPC APEX EXPO 2023. And we have an interview with Altium’s Rea Callender about the company’s educational efforts at APEX and around the globe.

Altium Focuses on Design Education

01/16/2023 | I-Connect007 Editorial Team
Altium keeps its eyes on the designers of the future. The company has been working with colleges and universities for years, providing free seats of Altium Designer for the next generation of PCB designers and design engineers. At IPC APEX EXPO 2023, Altium will be providing software for the finalists in the IPC Design Competition just as it did last year. They offer a variety of other educational programs as well, including Upverter classes and a design competition that aims to address environmental change. Here, Rea Callender, Altium’s VP of education, discusses its educational programs and plans for the week of the show.

The Battle of the Boards

01/12/2023 | Patrick Crawford, IPC
Last year, IPC held its first-ever design competition at IPC APEX EXPO in San Diego. PCB designers from around the world competed in a series of heats during the months before the show, culminating in a showdown on the show floor between the top three finalists. Rafal Przeslawski, now with AMD, took home the top prize last year. This year, the competition is back for its sophomore year. I asked Patrick Crawford, manager of design standards and related programs for IPC, to “layout” the details on the design contest, including lessons learned in 2022 and what’s new for the 2023 competition.



Copyright © 2023 I-Connect007 | IPC Publishing Group Inc. All rights reserved.