SLDA021B Application note | 德州仪器 TI.com.cn

SLDA021B March 2014 – February 2020 AM3892 , AM3894

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2.1 Land Diameters and Solder Mask Opening Diameters

The primary board design considerations include metal-pad sizes and associated solder-mask openings. PCB pads/land patterns, which are used for surface mount assembly:

Non-solder mask defined (NSMD) — The metal pad on the PCB (to which a package BGA solder ball is attached) is smaller than the solder mask opening.

Figure 1 and Figure 2 illustrate the metal-pad and associated solder-mask openings

Figure 1. NSMD Pads – Top View

Figure 2. NSMD – Cross-Sectional View