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PCB Pad & Footprint Orientation |
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Nick B 
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Joined: 02 Jan 2012 Status: Offline Points: 1925 |
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 Topic: PCB Pad & Footprint OrientationPosted: 7 hours 47 minutes ago at 10:04pm |
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Printed circuit board technology uses geometry to define the rotational angle of every object in the PCB design. Objects use geometry to define the orientation starting at 0,0 which is located on the right center. Cartesian coordinates are also defined per the PCB or Footprint origin. Popular Pad and Footprint rotations are 0, 90, 180 and 270 degrees, but can be placed at any angle. Pad and Footprint orientations start at 0,0 and rotate counterclockwise.  1. Pad Rotations Start at 0,0 in the Positive X Location Pad rotation follows geometry standards.  Footprint rotations are in 90° increments starting with the zero-component orientation per the IEC 61188-7 Rotation B released in 2007 with pin 1 in the Lower Left corner. IEC 61188-7 reflects the same zero component orientation documented in the IPC-SM-782 standard that was released in March 1987. The main reason to establish and follow a zero-component orientation is to help automate the assembly process. A known zero-component orientation will eliminate hours of research in PCB assembly trying to figure out the footprint rotations in the CAD library. IPC-7351 released in 2005 made a huge mistake by redefining pin 1 orientation to the Upper Left and broke an 18 standard where from 1987 – 2005 IPC defined the pin 1 orientation in the lower left. Also, the zero-component orientation should follow the Tape and Reel, Tube and Tray orientations defined by EIA. However, component manufacturer rotations vary from one mfr. to another for the same package type. A standard must be adhered to by component manufacturers. Here are the zero component orientations from IPC-7351, IEC 61188-7 and EIA-481-D.
Per all the JEDEC standard package definitions, quadrant 1 is where pin 1 should be located. IPC and IEC use consistent rotations throughout their standard where EIA uses multiple rotation variations.
This study concludes that the Zero Component output Orientation in the IPC Calculator should be 100% definable to allow the user to output any of the three industry standard rotations for CAD library construction. The only alternative is for the three standards organizations to collaborate on a single standard for the future. The IPC Calculator is being used all over the world. In the USA, military contractors, including General Dynamics in Canada, are asking for the IPC Calculator to output CAD library parts in the EIA-481-D rotation. In Japan, Germany, Australia and South Korea, IPC Calculator users are asking to output CAD library parts in the IEC 61188-7 rotation. The proposed IPC-7351C included Level A (current IPC standard) and Level B (IEC standard) component rotations. The main scope of zero-component orientations was to establish a consistent technique for the description of electronic component orientation, and their land pattern geometries, that facilitates and encourages a common data capture and transfer methodology amongst and between global trading partners. IPC, in conjunction with the International Electrotechnical Commission (IEC), have established several standards that are in the process of being coordinated. One of the standards is on the design of land patterns geometries (IPC-7351/IPC-7352/IEC 61188-5-1); the other set is on electronic description for data transfer between design and manufacturing (IPC-2581/IEC 61182-2). To maintain a consistent method where these two important standards describe the component mechanical outlines, and their respective mounting platforms, a single concept must be developed that takes into account various factors within the global community. Many large firms have spent millions of dollars creating and implementing their own unique standards for their own “Electronic Product Development Automation”. These standards are proprietary to each firm and are not openly shared with the rest of the industry. This has resulted in massive duplication of effort costing the industry millions of man hours in waste and creating industry chaos and global non-standardization. The industry associations responsible for component descriptions and tape and reel orientation have tried valiantly to influence the industry by making good standards that describe the component outlines and how they should be positioned in the delivery system to the equipment on the manufacturing floor. Suppliers of parts have either not adhered to the recommendations or have misunderstood the intent and provided their products in different orientations. The Land pattern standards put an end to the “Proprietary Intellectual Property” and introduce a world standard so every electronics firm can benefit from Electronic Product Development Automation. The data format standards (IPC-2581 and IEC 61182-2) are an open database XML software code that is neutral to all the various CAD ASCII formats. For true machine automation to exist, the world desperately needs a neutral CAD database format that all PCB manufacturing machines can read. The main purpose of creating the land pattern standards is to achieve reliable solder joint formation platforms; the reason for developing the data transfer structure is to improve the efficiency with which engineering intelligence is converted to manufacturing reality. Even if the neutral CAD format can drive all the manufacturing machines, it would be meaningless unless the component description standard for CAD land patterns was implemented with some consistency. Zero Component Orientation has a key role in machine automation. The obvious choice for global standardization for EE hardware engineering, PCB design layout, manufacturing, assembly and testing processes is to incorporate the standard land pattern conventions. Any other option continues the confusion and additional manual hours of intervention in order to achieve the goals of automation. In addition, the ease of having one system export a file so that another system can accomplish the work may require unnecessary manipulation of the neutral format in order to meet the object of clear, unambiguous software code. The design of any assembly will continue to permit arrangement and orientation of components at any orientation consistent with design standards. Starting from a commonly understood data capture concept will benefit the entire supply chain. Here is the flow for zero-component orientation and the counterclockwise rotation of a standard 8-pin SOIC.   PCB Footprint Expert The Footprint Expert reliably creates footprints and 3D STEP models with your preferred rotation. Modify any setting, then batch-rebuild your entire library! The Footprint Expert helps you create flawless PCB designs much more efficiently! Get your FREE Footprint Calculator or Footprint Expert Evaluation License: Call: 847-557-2300 |
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SDTKO
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Joined: 11 Dec 2019 Status: Offline Points: 31 |
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Posted: 4 hours 39 minutes ago at 1:12am |
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Is there an actual standard for bottom side zero component location and rotation direction? I feel like this just depends on how the CAD tool happens to implement it. There are tools that do it like this for example:  |
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