The following is reprinted with permission from Accelerated Designs inc.:
The following represents a compilation of the standards we use in creating our libraries. There is certainly more specifications than what we have chosen to include on the web, so if you would like more detail, please feel free to contact us. Remember that most of our components are made with automated tools and exported to many systems, so there may be some variations not covered in this document.
Footprint Patterns: (Construction Standard)
Where possible our parts are consistent with the IPC-7351 standard. We deviate from this standard in our naming conventions, our use of English units of measure. Also areas not covered (like symbols and attributes, silkscreen information etc.) by the standard are either based on other industry standards or are documented in this document.
Units of Measure:
All footprints and symbols are built in English units (Mils) unless otherwise specified. Metric units are input when appropriate (such as the pitch of metric pin spacings) but all dimensions are shown in Mils rounded to two decimal places. Actual locations are stored internal to our tool to 8 decimal place accuracy.
Entities and Attributes:
Each component has a RefDes attribute on the silkscreen layer of the pattern. In applicable tools there is also a RefDes2 attribute or second RefDes attribute on the Top Assembly layer. Where possible a Maximum and Minimum height attribute has been added to each footprint. Each footprint has dimensions on a separate layer to identify key features of the footprint. Each footprint has both a silkscreen layer which clearly identifies the part and any orientation. Also there is an Assembly layer containing data representing the exact size of the part. Each footprint contains a placement boundary if this information is available in the targeted CAD tool and it contains test probe boundaries that change size based on the z axis or height of the footprint. Data is contained for each footprint in our internal database to provide a 3d DXF formatted footprint if desired.
Component Naming Conventions:
Where possible industry standard naming is used. Where possible the naming referred to in the IPC-7351A is used, with the exception that sizes are in Mils rather than MM. An example might be CC1206 for a chip capacitor that is 120 mils by 60 mils. If such is not obvious then a two or three letter designator is assigned (or the standard designator used on PCB silkscreens) such as RES, CAP, FUS, etc. Following this designation would be a pin count or width x spacing designation, Examples: Xtal4_300x300 (overall size of part) or CAP200x400 or RES100x400 (width of part x Pin spacing). The following suffixes are also used:
|A=||Axial||P=||Polarized, Press fit|
|B=||Friction Lock or Ribbon||R=||Right Angle|
|K=||Keyed||T=||Additional Silk Information, Staggered|
|L=||Long or Large||U=||Upright|
|M=||Male or Military||Z=||Mount Holes|
|N=||Non Plated or Non Polarized|
Connectors being special are arranged with a prefix (generally "CON"), then a pin count, then a designation of how many pins in the columns x the rows, and finally a selection of designators to help delineate between the different available connectors. Examples: CON10_2x5 would be a header style part with 2 columns and 5 rows. If it had a -UFKH suffix then it would be an upright connector, female numbering, some sort of keying and would have a shroud of some sort. Additionally, since there are so many connectors that are very similar, we might follow with a style name such as -CLM indicating a particular manufacturer's style of part. This would help us in delineating between two manufacturers with very similar offering, but still different footprints.
The majority of the patterns in the library are built using the Ultra Librarian product to assist in consistency and in reliability.
Where appropriate components are based on the IPC-SM-7351 standard. Exceptions would include thru hole components as well as parts built to a specific standard and so labeled. Where possible components have been built using the 3-tiered complexity level of:
Least Material Condition
Nominal material condition
Maximum material condition
All components follow the Padstack Naming Convention. Where appropriate components contain local fiducials specific libraries for more details on specific included features. Padstack Naming Conventions.
Where appropriate components contain local fiducials.
Naming of padstacks start with a shape designator as follows:
Shape designators are followed by an "x" with the size in mils and then a y dimension with the size in mils. Example: RX40Y30 indicating a rectangular pad with a 40 mil x and a 30 mil y side.
Size is followed by a drill size. SMT pads are designated as "D0." Others as "D" followed by the drill size in mils. So the above example would expand to "RX40Y30D20".
If this padstack is a blind via or buried via it is indicated by a suffix number.
If the padstack is modified from a standard or existing padstack it is designated with a suffix number.
Each pattern has a pick and place point for assembly installed. It is placed on the pin in one of the pattern for thru-hole components and the centroid of the component for SMT patterns.
Each SMT component contains a glue dot as its centroid (where applicable).
Each component contains a placement point for referencing its pickup point in the CAD Tool. This point will reference the 0,0 location of the component for the CAD Tool.
Each component contains a rectangle of drawn lines or a filled polygon (depending on the CAD tool) that designates the total size of the component.
Each component contains a rectangle defining its nominal size for use with the height attribute.
Each component has a RefDes attribute on the silkscreen layer of the pattern.
In applicable tools there is also a RefDes2 attribute on the Top Assembly layer.
All RefDes Attributes are centered in the middle of the part with a Center-Center justification.
A 50 mil height attribute has been assigned to each component.
Component Naming Conventions:
If for some reason there are two components with the same name, a numeral is added at the end to delineate them.
Each pattern contains a silkscreen of the component on the top silkscreen layer. It avoids crossing pads where possible, but depends on a silkscreen removal routine to completely remove silkscreen from pads. Assembly information is included on the top assembly layer. It is intended to have a more complete description of the component available than would be available on the silkscreen layer. Assembly information reflects the true size of the part.
Silkscreen and assembly draw widths are 6 mils wide.
All text is 50 mil high with a 5 mil stroke width.
Pin one is identified on all polarized components.
Vendor Neutral Format from Accelerated Designs Inc.:
All of the libraries for the various CAD tools are generated from a single database. The data is stored in a vendor neutral format. This means that it stores all the relevant data from all the various CAD tools that we support.
Data can be imported from the various CAD tools and converted to the vendor neutral format. When the vendor neutral data is exported, it is converted to the format of the CAD tool of choice.
Both the importing and exporting of data is done with Ultra Librarian, a product developed by Accelerated Design Incorporated. All of the libraries sold were created by Accelerated Design Incorporated