In order to achieve the minimum diameter when design PCB according to the requirement of PAD, the diameter at least should be 0.5mmlarger than maximum diameter of soldering pin outer flange.

Designer has to provide testing PAD for all of joints according to ANSI/IPC 2221. JOINT means the electric connection among 2 or above components. One testing PAD need to use one signal node, coordinate location of testing PAD (also need to specify which side the testing PAD at) and X-Y coordinate axis of printed circuit board datum mark. Designer need to provide fixing installation data for SMT, as well as PCB layout technology, through which the testability of circuit diagram can be improved by the assistance of IN-CIRCUIT test fixing installation.

Below conditions are required:

1>    Diameter of PAD specify for in-circuit electric testing shouldn’t larger than0.9mm;

2>    Space around testing PAD should larger than0.6mmbut smaller than5mm, if the height of component greater than6.7mm, then this testing PAD should be placed5mmaway from this component;

3>    No components or testing PAD would be allowed to placed within3mmarea;

4>    Testing PAD should be placed in the center of2.5mmdiameter, if possible, apply a standard probe and more reliable fixing device is allowable.

5>    Don’t use the edge of connector’s pin to instruct PAD testing, since the testing probe could readily damage the gold-plated pins.

Aspect ratio of plated-through hole has great impact on effectively through-hole plating capability for manufacturer, it is also very critical for ensuring the structure of PTH/PTV. When the diameter of hole smaller than 1/4 of basic printed circuit board thickness, tolerance should increase0.05mm. When drilling hole diameter is0.35mmor even smaller, aspect ratio could be 4:1 or even larger, manufacturer should use the proper way to shield or block the through-hole to prevent entering of the solder, generally speaking, printed circuit board thickness and plated through hole ratio should less than 5:1.

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