IEC TR 61188-8 pdf – Circuit boards and circuit board assemblies – Design and use – Part 8: 3D shape data for CAD component library
a) dimensions (see 5.2);
b) material distinction (see 5.3);
c) marking (see 5.4);
d) component identification information (see 5.5);
e) reference point and placement angle (see 5.6);
f) scale (see 5.7);
g) CAD format (see 5.8);
h) component shape levels (see 5.9);
i) other attributes (see 5.10).
5.2.1 Dimensions of 2D drawing
The dimensions of 2D drawing in all dimensions of the prepared data are basically nominal values.
5.2.2 Dimensions of 3D shape models
The dimensions of 3D shape models are as follows:
a) basically, all dimensions in the data to be prepared should be nominal values;
b) The tolerances with 2D drawing are important to clarify;
c) When the description of the dimension is “1.0+0.3/-0.1”, “1.0” is taken as a nominal value.
5.3 Material distinction
To check locations with resin surface and those with metal surface, it is desirable to distinguish them with different colours.
If the component has polarity or orientation markings, the markings should not be omitted in the component shape data. An example of marking is shown in Figure 1.
5.5 Component identification information
The shape data should be included with identification information for the purpose of retrieval and storage.
Representative items of identification information are shown in items a) to g) below:
a) part number;
b) manufacturer name;
c) manufacturer model name or manufacturer part number;
d) design use data: file name and version;
e) complement data: file name and version;
As for the constitution information, XML should be used as a searchable description format.
5.6 Reference point and placement angle
Rules for 2D drawings
The rules for 2D drawings are as follows:
a) components and land patterns are drawn in top view;
b) the component point of origin is shown by “+” or “x”;
c) A circumscribing rectangle which contains the component body and land patterns (in top view) should be a part of the library component description. This rectangle is the “Courtyard” that provides a minimum electrical and physical clearance for the part and the land pattern. The point of origin of the description should match that of the component and land pattern. The descriptions of the components, land patterns, and circumscribed rectangles, described are the same in the computer library, and each description uses the same origin coordinates. It is recommended that the point of origin is the same as the way the component is positioned on the final design of the board which is normally by the centroid of the component body.
5.6.2 Rules for 3D shape models (component with no moving part)
The rules for 3D shape models (component with no moving part) described are as follows:
a) relation between 2D drawing and 3D shape model;
It is desirable to design the reference point and placement angle according to the same rules.
b) reference point;
The center of the outline of the largest rectangle containing the electrodes described are the reference point.
The sitting plane is considered to have a Z value of 0, and the direction moving below the seating plane is considered the minus direction of the Z-axis.
c) placement angle
Indicate the polarity so that it is in the minus direction in the X-axis or in the minus directions of both X- and Y-axes. The example of placement angle is shown in Figure 2.
5.6.3 Rules for 3D shape models (component with moving part) Connectors 126.96.36.199 In case of connectors with a moving part, the center of the outline of the largest rectangle containing the electrodes in closed position should be the reference point. The example of placement angle of connectors is shown in Figure 3.