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Design007-June2019

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34 DESIGN007 MAGAZINE I JUNE 2019 a great set of instructions and an easy-to-fol- low recipe for making this cake. No matter if you are baking a cake or build- ing a circuit board, it's all about clear commu- nication. If the person writing the recipe had not made the choice to clearly communicate what their intentions were for baking that cake, I would have been lost. A missing ingredient here or an incorrect oven temperature there and my birthday surprise would have ended up in the garbage in the same way a success- fully built circuit board starts with clear com- munication from the designer. Circuit board manufacturers want to create a perfect PCB for you, but they can only do so to the extent of the instructions that you give them. Everything truly does start with design, and whether you have success or not is up to you and how you communicate it. To clearly communicate your "recipe" to your board manufacturers, you need to make sure that you include all of the data that they will need to get the job done correctly. This will include variations of the following data files at a minimum for both fabrication and assembly: • PCB image files: These are typically Gerber formatted data files with their accompanying apertures assignments • NC drill files: Excellon formatted data files that have been the standard for years • Fabrication drawings: These should include board layer stackup information and drill sizes with their quantities and locations; they should also include dimensions of the board and any unique cutout features as well as detailed notes for the fabrication of the bare PCB • Assembly drawings: These should include component locations and their reference designators as well as unique assembly details, such as mechanical f eatures and any necessary mounting hardware; there should also be callouts for markings and labels as well as detailed assembly notes • Bill of materials (BOM) report: This will be a data file that lists the details of each part on the circuit board • XY location file (pick and place): This report details the XY location of each part on the circuit board for automated assembly equipment • Netlist: This file will include all of the connectivity of the PCB for automated test routines that will be run by the manufacturer As I said, this is just the minimal amount of data to tell your manufacturer what your PCB design needs to be built. You can do a lot more to improve communication and make your in- tent even clearer. When I was baking the cake, I had a great set of instructions in the recipe I used. But the problem was that I didn't necessarily under- stand all of the detailed instructions in the rec- ipe. For instance, I didn't understand what it meant to "butter and flour the cake pan," or "fold the eggs into the mixture." Hey, don't laugh; if you've never done this before, you might wonder how you "fold" eggs as well. Fortunately, I was able to find some help from online videos, and I quickly learned these little treasures of successful baking techniques. In the same way, we too can add additional helpful instructions to our manufacturing files in the form of "README" files. These can be as simple or as complex as you want to com- municate information that is above and be- yond what you already have in your regular manufacturing files. The key is to make ev- erything as clear as possible with your man- ufacturer. This also includes providing them with your design database if necessary. Many PCB contract manufacturers now prefer work- ing with your entire PCB design database, es- pecially when building prototype boards. This way, they have immediate access to schematic and netlist information that they know is syn- chronized with the layout information. Another way to give your manufacturer more complete information is to use an IPC-2581 for- matted output file. These files contain all of the PCB manufacturing data that the fabrication and assembly shops need to build your board. Many PCB design systems now have the capa- bility to export manufacturing data in this for-

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