Requirements for Electronic and Mechanical Assembly

To avoid delays in processing your quotations, on turn key or consignment assemblies, please supply the following information.

 

Documentation requirements

• BOMs	• Software
• Drawings
Documents may be supplied as Word files, Excel files or hard copy. Bill of Materials include: Manufacturer’s part number Component locations listed by reference designators and quantity Through hole or SMT Device notation Drawings: Assembly drawings, including any change notices, may be supplied as "Gerber" files, ".dxf", ".pdf" files or hard copy. Dimensional specifications for non-standard components such as connectors, headers, sockets, transformers, LEDs, etc. Software requirements: Solder paste stencil file in "Gerber" format. Electronic "Centroid data" in ASCII format: These are the "X" & "Y" coordinates for the location of the parts on the board. These coordinates should reflect the location of the center of the component body referenced to the same zero point. This information should also include the respective component designations as well as the component rotation. The preferred format for coordinates is in millimeters.

PCB Requirements

• Fiducials	• Finish
• PCBs
Fiducial marks Circuit board with fiducial marks to be used for registration of boards or panels is preferred. Fiducial marks are isolated targets placed on the board for the purpose of verifying registration of the board, panel, or component location during assembly. Fiducials are usually placed diagonally opposing on two of the outside corners. There should be a minimum solder mask clearance of .015". Fine pitch components with spacing of 25 mils or less should include 2 fiducials for placement verification. One should be in the center and the other should be diagonally placed to the outside edge of the component. PCBs For assembly throughput, a minimum of 0.25" space clearance from any edge of the panel to the edge of the nearest component body. Circuit boards must meet bow and twist specifications of IPC–D-600. When boards are smaller than 4 X 5 inches, or not rectangular, please array the boards panel form with scores whenever possible. Finish The finish on the surface mount pads must be flat to allow for proper placement of SMT components. Flatness becomes more critical as the pitch becomes smaller. Examples of a preferred flat finish would be Ni/Au (immersion gold over electroless nickel), OSP(Organic Solderability Preservatives) or Electroless Palladium(recommended). Soldermask should cover all traces and exhibit good registration.

Components

• Packaging	• First Article
• Extra Parts	• Quotes
Component requirements apply for all components supplied by the customer and not supplied by A and M Electronics. Packaging SOICs should be supplied in either tubes or on tape and reel (T&R) with a 12" leader. PLCC components should be supplied in trays, tubes, or T&R. QFP components are to be packaged in trays. To prevent damage to QFPs, please do not remove from their original trays and do not break the hermetic seal. T&Rs are preferred for all components whenever possible. Extra Parts All SMT components provided on T&R should have a factory-attached leader approximately 12" long before the first component. When practical, please provide 5% extra for all parts provided on T&R and 2% extra for all other forms of packaging. Unused parts will be returned after the completion of assembly. First Articles: The first time we set-up a new assembly for SMT, it is both important and necessary that we verify solder paste stencil set-up, placement programming, feeder set-up and optimization, placement accuracy and oven profile for proper reflow of the solder paste with the components mounted. It is not recommended that these parameters for proper assembly be learned "on the fly". The multitudes of possible problems encountered during this exercise are far too numerous to list. These potential problems must be identified and corrected before the production order is run through the entire sequence of events required for proper SMT assembly. It may often be required that we build 1 or 2 assemblies for purposes of proofing the set-up. It is possible that these boards may or may not be usable after this exercise. We will not mount components identified as expensive for this proofing and we request that if you are the supplier of the boards, please send any extra bare boards that you may have on hand. These bare boards may be scrap due to damage or defects in manufacturing, extras, or possibly an older revision that has become obsolete, but please identify them as scrap to be used for test purposes only. Quotes Prices are subject to change until after final review and receipt of all supplied parts and/or boards for assembly. Delivery times are based on the receipt of completed kits on customer furnished material. Set-up charges quoted are also based on the above requirements. Set-up charges include: Solder paste screen, custom tooling or fixtures, kit audit and verification, programming for pick and place, feeder preparation,and product specific thermal profile for solder paste reflow.