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When designing pads for components not specifically covered in this manual, it is suggested that manufacturing, part vendors and assembly vendors be contacted for design recommendations.The nominal dimensions of components will be used to design pad geometries.
Caution is advised when designing for a component with multiple vendors as package dimensions may not be the same.Indicate pin 1 on all connectors, headers, crystals, and any other component where pin 1 is not readily identifiable.Panelization is the placing of 2 or more board images on blank material for processing, thus saving time and material over processing one board at a time (see Figure 2-2).A series of holes are drilled at several locations along the edge of the board, and the board outline is partially routed to form a tab to hold the processed board in the blank.The board may then be snapped out of the blank before or after components have been installed and soldered.An example of a tab would be 5 holes with center to center spacing of 0.041″ and a hole diameter of 0.021″.
** PAD CAP OUTER LAYERS ARE RECOMMENDED ** If used, solder mask clearance is required around all surface mount and through hole pads, tooling holes, shield contact areas, fiducials, and any areas where electrical contact or soldering is required. Tooling holes are required for positioning the PWB in machines and fixtures needed to process the board (e.g.
An attempt should be made to provide designators for all component outlines shown on the silkscreen.
Designators should be readable when components are installed.
The extra board material may then be snapped off after the assembly is complete.
Be aware that tab locations may interfere with installation of the board into later assemblies, and the appropriate engineering groups should be consulted to determine correct tab placement and board configuration.
In the case of small and flex type boards, where exceptions to these standards may be required, fabrication and assembly vendors should be consulted and approval sought from the responsible engineering group.