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Design007-Aug2018

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36 DESIGN007 MAGAZINE I AUGUST 2018 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-con- tacted. This makes the surface of the via flat and can be used as 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 manufactur- ing costs, via in pads will always be preferred, because of the higher integration density of BGAs and their lower inductance at high fre- quencies (signal quality). Fanout routing features in today's tools let you decide between the classical fanout (auto or BGA) and via in pad. For classic fanout routing, Altium Designer offers all the neces- sary settings for the direction of the fanout (direction from pad) whether the via should be placed in the center between the terminals of the BGA or not (via placement mode). The via is placed between the terminals of a BGA in most cases, because of costs and ease of manufacturing. Figure 2: Visual representation of terminals of a BGA with their connection possibilities. Figure 3: Signal lead with fanout and escape routing and a voltage supply connection as with via-in-pad.

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