PCB Pad Tips

Dated:2018-01-22      Popularity:1127


PCB Pad

In Allegro, before making a symbol, you must create pins of PCB components first. Component package are divided into two types: SMD and line. Different packages require different pads.

Pads in Allegro mainly includes:

1.Physical pads of components

a.Regular pads with round, square, oval, rectangle, octagon, and arbitrary shapes. Specific size is set according to the actual size of the package, refer to ‘IPC-SM-782A Surface Mount Design and Land Pattern Standard’;

b.Thermal relief with round, square, oval, rectangle, octagon, and arbitrary shapes. Usually 20mil larger than the regular pad size, if regular pad size is less than 40mil, you need to appropriately reduce the size difference;

c.Anti pads with round, square, oval, rectangle, octagon, and arbitrary shapes, used to prevent pins from connecting to other networks. Usually 20mil larger than the regular pad size, if regular pad size is less than 40mil, you need to appropriately reduce the size difference. 

2.Soldermask

Solder mask is the part of the board that is going to be greenish. In fact, the solder mask is used negative output, to increase the thickness of the copper, usually using a solder mask to mark the green ink, and then add tin to increase the effect of copper thickness. Usually 4mil larger than the regular pad.

3.Pastemask

It is used during the SMD process. Usually solder mask can not be larger than the actual size of the pad. It is usually the same size as a regular pad.

4.Filmmask

It is used to add user-defined information. It is less used, thus, users can set their own size.

Package pads of line components contain several main elements:

1.Begin layer: sizes of thermal relief and anti pad are 0.5mm larger than the actual size of the regular pad;

2.End layer: sizes of thermal relief and anti pad are 0.5mm larger than the actual size of the regular pad;

3.Default internal: middle layer

Drilling hole size: actual PIN size + 10mil;

Pad size: at least hole size + 16mil (hole size <50);

Pad size: at least hole size + 30mil (hole size> = 50);

Pad size: at least drilling size +40 mil (drilling hole is rectangular or oval);

Anti pad: drilling size +30 mil;

Solder mask: regular pad size + 6mil;

Solder mask: regular pad size;

Inner hole size: drilling size + 16mil;

Outer hole size: drilling size + 30mil.


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