Glossary - PCB Power


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The purpose of this glossary is to provide you with meanings of the words and phrases explaining the PCB design and circuit board construction while you deal with PCB POWER.

Air Gap: The minimum distance between copper features pad-pad, pad-trace, trace–trace.

Annular Ring:  The portion of conductive material surrounding an entire hole.

Annular Ring = 1/2 (Circuit layer pad diameter – PHD);
Where PHD = Production Hole diameter or Tool Size
= finished hole size + 0.15 mm for Plated through Holes
= finished hole size + 0.05 mm for Non Plated through Holes

Annular Ring

PCB Power recommends,

Minimum Annular ring for Outer layers: 0.125 mm

Minimum Annular ring for Inner layers: 0.125 mm

IMPORTANT: For annular Ring calculations the production TOOLSIZE for the holes is more suitable than the finished hole ENDSIZE.

We recommend a minimum annular ring of 0.50 mm for connected non-plated (NPTH) holes since these holes have no plated barrel and an annular ring of a smaller size may lift during soldering or break away even during normal operating conditions.

Aperture List: An ASCII text data file which describes the size and shape of the apertures used by a photo plotter for any one photo plot.

Aperture file looks as the one given below: (This is the separate file for aperture detail and you can see the contents of this file by opening it with the notepad or WordPad.)

D10ROUNDED8.0008.0000.000 LINE
D12RECTANGULAR80.00024.0000.000 FLASH
D13ROUNDED27.55986.6140.000 FLASH
D14RECTANGULAR27.55986.6140.000 FLASH
D15RECTANGULAR60.00050.0000.000 FLASH
D16RECTANGULAR25.59141.7320.000 FLASH
D17RECTANGULAR78.740125.9840.000 FLASH
D18RECTANGULAR50.00060.0000.000 FLASH
D19RECTANGULAR86.00024.0000.000 FLASH

Aspect Ratio:  Ratio of board thickness to production hole diameter. The larger the aspect ratio, the more difficult it is to achieve reliable plating.

Aspect Ratio = PCB thickness / Drill diameter (P.H.D.)

Aspect Ratio
Array Sub Panel

Array / Sub Panel: Two or more PCBs are arrayed in a panel and handled by both the manufacturing house and assembly house as a single PCB. The sub-panel is usually prepared at the manufacturing house by routing most of the material separating individual PCBs, leaving small tabs. The tabs are strong enough so that the sub-panel can be assembled as a unit and weak enough so that the final separation of assembled modules is easily carried out.

Assembly Drawing: A drawing representing component locations with their reference designators on a PCB.

Assembly Drawing

BGA: Ball Grid Array, a popular surface mount chip package that uses a grid of solder balls as its connectors. BGAs have better electrical and thermal performance and occupy less space than leaded packages. BGA is noted for its compact size, high lead count and low inductance, thus allowing lower voltages to be used.


Build time: It is a leading time to get your PCBs manufactured.

Clearances: It is referred as air gap between any copper features pad-pad, pad-trace, trace –trace, also referred as isolation between copper layers sometime.

Component Side: A board side onto which components are mounted.

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