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      <title>Defining a PCB assembly</title>
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      <div class="title_topic3" id="xps10_pagetitle">Defining a PCB assembly</div>
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      <p class="para_topic">You can use the PCB.xchange toolbar to define a new PCB Assembly, including its mechanical design and general layout, as well as the placement of certain critical components. You can export the PCB assembly to an ECAD file for import into most ECAD systems.</p>
      <p class="para_topic">If the PCB assembly requires a board or component that does not already exist as a part, you can create it using the Modeling application.</p>
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                  <p class="para_td">Nomenclature correspondence</p>
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                  <p class="para_td">ECAD nomenclature</p>
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                  <p class="para_td">NX assembly nomenclature</p>
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                  <p class="para_td">Reference designator</p>
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                  <p class="para_td">Assembly component name</p>
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                  <p class="para_td">Package name</p>
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                  <p class="para_td">Part name (and part file name, without the .prt extension</p>
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                  <p class="para_td">Part number</p>
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                  <p class="para_td">Value of the MAYA_PCB_COMP_NUMBER attribute of the assembly component</p>
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      </table><br><div class="title_division"> Procedure for creating a PCB assembly</div>
      <p class="para_division">The basic procedure for defining a new PCB assembly is much the same regardless of the assembly you are creating. </p>
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            <p class="para_item">Create or open a PC board part to serve as the root part of the assembly.</p>
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            <p class="para_item">Sketch on the top and/or bottom surface of the board to represent the outlines of any keep-outs or keep-ins. Add simple hole features to the board to represent any drilled holes. Define the attributes of these items using the appropriate PCB.xchange toolbar icon. </p>
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         <li>
            <p class="para_item">Create any new parts you need for components in the assembly. The component part's Absolute CSYS serves as the component origin as defined in the IDF standard, identifying component orientation and placement, including offset. </p>
         </li>
         <li>
            <p class="para_item">In the Assemblies application, use the Components commands to add existing parts as components in the assembly. Define the component name as the reference designator. Build up the assembly with the <b class="commandName">Add Component</b> and <b class="commandName">Reposition Component</b> commands. 
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                        <p class="para_note_body">Use the Assembly navigator as an aid to organizing your work. MB3 on the column headings allows you to display the component name (reference designator) as a column in the navigator.</p>
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            <p class="para_item">Use the PCB.xchange toolbar to set component attributes as required. </p>
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            <p class="para_item">Validate the PCB assembly and correct any errors detected.</p>
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      <p class="para_division">The following sections of this article provide additional details on this procedure.</p>
      <div class="title_division"> Positioning a component</div>
      <p class="para_division">Use the <b class="commandName">Reposition Component</b> command to position the component. Position the component so that at least part of it is within the X-Y boundaries of the board. Ensure that no component overlaps any other component.
      </p>
      <p class="para_division">When the PCB assembly is exported to ECAD, the software uses the position and rotation of the component part's Absolute CSYS to determine component placement and orientation (with respect to the board part's Absolute CSYS). If necessary, rotate the part so that the Z-axis points away from the board. Offset mounting is defined by positioning the origin of the component's Absolute CSYS above the board surface.</p>
      <p class="para_division">According to the IDF standard, rotations of the component are defined as the rotation from the X of the Board CS to the X of the Component CS; counter-clockwise is <em>positive</em> rotation. Also note that according to IDF, the rotations (and board placement) are relative to the board side. That is, X-Y location and rotation is viewed by flipping the board over for the back side and  not by looking through the board (as is the ECAD convention).
      </p>
      <div class="title_division"> Creating new parts for the PCB assembly</div>
      <p class="para_division">New parts (components or boards) can be created with the Modeling application. You must create the part with the Absolute CSYS location and orientation identical to those of the component or board in the ECAD application library. See <a class="links" href="javascript:void(0)" onclick="top.openFile('pcb/mu_managing.html');return(false);">Managing Detailed Component Parts</a> for more information.
      </p>
      <div class="title_division">Creating a PC board part</div>
      <p class="para_division">If the PC board is taken from an existing collection of parts set up in accordance with practices outlined in the section  <a class="links" href="javascript:void(0)" onclick="top.openFile('pcb/mu_managing.html');return(false);">Managing Detailed Component Parts</a>, it will already have a coordinate system set up at the proper location. However,  you must define the Board Attributes with the PCB.xchange toolbar in order for the board to be recognized as a valid board when translated to ECAD.
      </p>
      <p class="para_division">The absolute coordinate system (CSYS) serves as the coordinate system for the PCB assembly in ECAD. The Absolute CSYS provides a means of passing geometry data to PCB.xchange for writing the ECAD file. Component placement and locations of drilled holes are all referenced from the Absolute CSYS.</p>
      <p class="para_division">The board's Absolute CSYS coordinate system's X-Y plane must lie in the top plane of the board. The +Z axis determines the top surface of the board. Standard practice is to define the CS origin at the lower-left most point on the board or at the lower-left most tooling/mounting hole on the board.</p>
      <div class="title_division">Creating a component part</div>
      <p class="para_division">If the component is taken from an NX component collection set up in accordance with practices outlined in   <a class="links" href="javascript:void(0)" onclick="top.openFile('pcb/mu_managing.html');return(false);">Managing Detailed Component Parts</a>, it will already have a coordinate system set up correctly. However,  you must define the Component Attributes with the PCB.xchange toolbar in order for the component to be recognized as a valid component when translated to ECAD.
      </p>
      <p class="para_division">If you are creating a new part, or building a component collection for use with the PCB.xchange toolbar, make sure the part's Absolute CSYS origin and orientation correspond to the origin and coordinate system in ECAD. The Absolute CSYS +Z axis defines component mounting direction and offset. If the Absolute CSYS of each part is defined correctly, their displayed orientation in the assembly will match the IDF orientation when the assembly is written to ECAD.</p>
      <p class="para_division">Standard practice is to define the Absolute CSYS origin at the center of pin 1, if applicable. For flush-mounted components, the Absolute CSYS origin is in the plane of contact between the component and the PC board. Mounting offset is defined by the distance from the board surface to the Absolute CSYS origin.</p>
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