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PCB via current capacity chart showing 1 mil plating via current capacity & resistance versus diameter on a 1.6 mm PCB. In printed circuit board (PCB) design, a via consists of two pads in corresponding positions on different copper layers of the board, that are electrically connected by a hole through the board.
Traditionally, a number of different sizes were defined for large sheets of paper, and paper sizes were defined by the sheet name and the number of times it had been folded. Thus a full sheet of "royal" paper was 25 × 20 inches, and "royal octavo" was this size folded three times, so as to make eight sheets, and was thus 10 × 6 + 1 ⁄ 4 inches.
The codes given in the chart below usually tell the length and width of the components in tenths of millimeters or hundredths of inches. For example, a metric 2520 component is 2.5 mm by 2.0 mm which corresponds roughly to 0.10 inches by 0.08 inches (hence, imperial size is 1008).
Visualization with paper sizes in formats A0 to A8, exhibited at the science museum CosmoCaixa Barcelona An A4 paper sheet folded into two A5 size pages. ISO 216 is an international standard for paper sizes, used around the world except in North America and parts of Latin America.
For similar reasons, a technique called trace necking reduces (or necks down [7] [8] [9]) the width of a trace that approaches a narrower pad of a surface-mounted device or a through-hole with a diameter that is less than the width of the trace, or when the trace passes through bottlenecks (for example, between the pads of a component). [8] [9 ...
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A via fence consists of a row of via holes, that is, holes that pass through the substrate and are metallised on the inside to connect to pads on the top and bottom of the substrate. In a stripline format both the top and bottom of the dielectric sheet are covered with a metal ground plane so any via holes are automatically grounded at both ends.