your PCB. Read and understand these tips before you start your layout using
Ultiboard… We recommend watching “Ultiboard PCB software”:.
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Creating a Printed Circuit Board The instructions to make a PCB are separated into 2 parts. In the first part you use Ultiboard to create Gerber files. In the second part you use those same Gerber files to create an LMD file that is provided to the milling technician and directly read by the milling machine.
The CCNY Electrical Engineering department recommends you use Ultiboard to create your PCB. Read and understand these tips before you start your layout using Ultiboard… We recommend watching “Ultiboard PCB software”:
http://www.youtube.com/watch?v=22j3u4BRTbs and reading the “NI Ultiboard Fundamentals”: http://www.ni.com/pdf/manuals/373180a.pdf The manual to Ultiboard is located here: http://www.ni.com/pdf/manuals/374488e.pdf You can also borrow a printed manual from the technician’s office.
PART A 1. Placing Components Generally, it is best to place parts only on the top side of your board. Unless necessary, we recommend you do this. You will have to explain and justify if you don’t. When placing components, make sure that the snap-to-grid is turned on. Usually, a value of 0.050" for the snap grid is best for this job. First place all the components that need to be in specific locations. This includes connectors, switches, LEDs, mounting holes, heat sinks or any other item that amounts to an external location. Give careful thought when placing component to minimize trace lengths. Put parts next to each other that connect to each other. Doing a good job here will make laying the traces much easier. Arrange ICs in only one or two orientations: up or down, and, right or left. Align each IC so that pin one is in the same place for each orientation, usually on the top or left sides. Position polarized parts (i.e. diodes, and electrolytic caps) with the positive leads all having the same orientation. Also use a square pad to mark the positive leads of these components.
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3/22/2011 You will save a lot of time by leaving generous space between ICs for traces. Frequently the beginner runs out of room when routing traces. Leave 0.350" - 0.500" between ICs, for large ICs allow even more. Parts not found in the component library can be made by placing a series of individual pads and then grouping them together. Or you can use the PARTS WIZARD which is located Tool>Parts Wizard. Place one pad for each lead of the component. It is very important to measure the pin spacing and pin diameters as accurately as possible. Use a dial or digital calipers for this job. After placing all the components, print out a copy of the layout. Place each component on top of the layout. Check to insure that you have allowed enough space for every part to rest without touching each other. 2. Placing Signal Traces When placing traces, it is always a good practice to make them as short and direct as possible. Use vias (also called feed-through holes) to move signals from one layer to the other. A via is a pad with a plated-through hole. Generally, the best strategy is to lay out a board with vertical traces on one side and horizontal traces on the other. Add via where needed to connect a horizontal trace to a vertical trace on the opposite side. A good trace width for low current digital and analog signals is 0.010". Traces that carry significant current should be wider than signal traces. The table below gives rough guidelines of how wide to make a trace for a given amount of current. 0.010" 0.3 Amps 0.015" 0.4 Amps 0.020" 0.7 Amps 0.025" 1.0 Amps 0.050" 2.0 Amps 0.100" 4.0 Amps 0.150" 6.0 Amps When placing a trace, it is very important to think about the space between the trace and any adjacent traces or pads. You want to make sure that there is a minimum gap of 0.007" between items, 0.010" is better and is best is 45mil. Leaving less blank space runs the risk of a short developing in the board manufacturing process. It is also necessary to leave larger gaps when working with high voltage. Also, larger gaps make soldering easier. The milling machine interprets gaps as areas of isolation. When you use Circuit Cam to process the layout you will determine how much copper to remove and hence provide the amount of isolation you desire. Later, if you are not able to use an isolation width of 45 mils around your traces YOU WILL NEED TO EXPLAIN WHY NOT. Your board may be rejected for milling. It is a common practice to restrict the direction that traces run to horizontal, vertical, or 45 degree angles. When placing narrow traces, 0.012" or less, avoid sharp right angle turns. The problem here is that in the board manufacturing process, the outside corner can be etched a little narrower. The solution is to use two 45 degree bends with a short leg in between. 3. A note about drilling:
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3/22/2011 The Milling machine has drill bits ranging from .5 mm to 3mm for holes bigger than 3mm the milling machine uses a Contour Router which cuts out the hole. However, the larger variety of drill holes you use, the more drill bits you will need and the more time it will take to setup and complete your project. Unless necessary, we recommend you make any holes smaller than 0.118110 inches, the same size. You will have to explain and justify the variation of your drill hole sizes and if they are deemed unnecessary the technician will ask you to RESUMBMIT your layout. Please use the least amount of variation in drill hole sizes as possible. For example, if your project requires 3 different holes that are .025, .028, and .032 you may want to make all of these holes .032 since it will save time and fit all these sizes. Consult a technician if you have any questions. Once you know what size all your drill holes will be You can also double check the drill hole sizes you are using after you finish part 5 of the “Processing the layout data by means of CircuitCAM” tutorial. 4. Checking Your Work After all the traces are placed, it is best to double check the routing of every signal to verify that nothing is missing or incorrectly wired. Do this by running through a printout of your schematic, one wire at a time. Carefully follow the path of each trace on your PC layout to verify that it is the same as on your schematic. After each trace is confirmed, mark that signal on the schematic with a yellow highlighter. Inspect your layout, both top and bottom, to insure that the gap between every item (pad to pad, pad to trace, trace to trace) is 0.007" or greater. Use the Pad Information tool to determine the diameters of pads that make up a component. Check for missing vias. Check for traces that cross each other. Check that the back is not the front and vice versa. Metal components such as heat sinks, crystals, switches, batteries and connectors can cause shorts if they are placed over traces on the top layer. Inspect for these shorts by placing all the metal components on a printout of the top layer. Then look for traces that run below the metal components. After you’ve finished creating your board export it as Gerber RS-274X files. Next in PART B, you will take those Gerber files and create a LMD and CAM file which will be submitted to the PCB milling machine technician for milling. The LMD/CAM file should be free of all errors.
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PART B Processing the layout data by means of CircuitCAM The layout data has to be processed into production data in CircuitCAM and must be exported to the LMD-format. I. Importing the layout data to CircuitCAM 1. On the desktop double click on the CircuitCAM symbol. or: Click on Start > Program Files > LPKF Laser & Electronics > CircuitCAM... . 2. Click on File> Import 3. Find the directory or folder containing the Gerber files you exported from Ultiboard and select the following files with the Ctrl key depressed: NameOfCircuit_V1 - Board Outline.gbr; NameOfCircuit_V1 - Copper Bottom.gbr; NameOfCircuit_V1 - Copper Top.gbr; NameOfCircuit_V1 Drill-Copper Top-Copper Bottom.gbr 4. Click on Open. The Import window is opened with the selected files. 5. In order to assign the desired layer: – In the file list, click on the name of the desired “NameOfCircuit_V1” file (column File name), to select the file. – In the column Layer/Template, click on the dropdown list and select the desired layer. (→ Tab. 1: „Layer assignation“)
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6. Assign a certain layer to each layout file. Use the following settings: File Name
Layer/Template
NameOfCircuit_V1 - Board Outline.gbr
BoardOutline
NameOfCircuit_V1 - Copper Bottom.gbr
BottomLayer
NameOfCircuit_V1 - Copper Top.gbr
TopLayer
NameOfCircuit_V1 - Drill-Copper Top-Copper Bottom.gbr
DrillPlated
Tab. 1: Layer assignation
The settings are instantly displayed on the register card Graphic. 7. Click on OK.
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[ ] After you have imported all layout files, the data will be displayed in the CircuitCAM graphic window.
II. Removing tracks in CircuitCAM UltiBOARD leaves reference holes and reference lines around your board outline which need to be removed.
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1. First highlight them by left clicking the top left corner of each of them and dragging the highlight box down to the right. -
It helps to zoom in. Zoom in by clicking on View>Zoom In
2. After each track or reference hole is highlighted in white, press delete. – Do this for all three reference holes and all four corner reference tracks.
[ ] After you remove all of the excess traces there should be nothing outside of your board outline. III. Generating Insulation for Bottom and Top Layer Insulation means the calculation of insulation channels around interconnected traces, pads and other areas. The insulation channels are required for PCB prototype production with the LPKF 7
3/22/2011 mill/drill plotter. The minimum isolation width is 8 MILS (0.008 inches) but we recommend making the insulation 45 MILS (.045 inches). 45 Mills leaves you enough room to not make hand soldering too difficult and also doesn’t excessively wear out the milling bits by having them remove all the Copper from the board. If you do not use 45 mills of isolation YOU WILL NEED TO JUSTIFY AND EXPLAIN WHY TO TECHNICIAN.
Figure 1. Example of PCB with 8 mill (.2 mm) insulation
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Figure 2. Example of PCB with 45 mill ( 1.14 mm) insulation
1. Click on the tool path>Insulate 2. In the main tab select Bottom(Solder Side)
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3. Change Width Base(ALL) to 45 mil 4. Click Run 5. Repeat for Top (Component Side).
[ ] After you insulated the Bottom and Top layers, the insulation will be displayed in CircuitCAM.
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3/22/2011 IV. Generating contours Contours are needed so the board can be cut out at the end of the milling process. 1. Click on the Contour Routing button.
The Contour Routing window is opened. Select the following settings: Outside Source Destination Layer
Layer
Used tool
List
CutingOutside
Tool Breakout
BoardOutline
LpkfCuttingTools ContourRouter 1.0 mm (39 mil)
4 edges Width
1 mm
2. Click on Run. The contour is displayed as a line 1 mm in width.
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V. Exporting data as project The export will automatically produce a *.cam and a *.LMD file. The latter is used for the production by means of the LPKF circuit board plotter and is referred to as a project. 1. Click on the Export LPKFCircuitBoardPlotter button.
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The Save as window will be opened.
3. Save the NameOfCircuit_V1.cam file in the desired directory. The *.LMD file is exported automatically to the same directory and you will need to email both files to machine technician to create your PCB. 4. Click on OK. 5. Email milling machine technician the LMD and CAM file.
VI. Filling out Capstone Milling Form The final step is filling out the Capstone Milling Form and look up what tools will be needed in order to create your PCB. Take the time to fill out sections 1 through 11. For section 7, 10 and 11, give as much detail as possible. You will be required to redo your board if isolation widths and variations in drill bits are deemed unnecessary. Now for sections 12, 13 and 14 you will have to do the following in order to know what tools will be used during milling: 1. On the left of the page click the Tools tab.
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2. Click on LPKF MILL/DRILL> LpkfCuttingTools and LPKF MILL/DRILL> LpkfMillingTools 3. The milling tools that are needed are highlighted (hence not in gray) under LpkfCuttingTools and LpkfMillingTools. - Record what milling tools are needed in the Tools Needed section of the Capstone Milling Form.
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4. Next Click on Gerber>GerberDefault3 to see what drill bits will be needed.
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3/22/2011 The milling machine will use the drill bit that is closest to the hole size needed. In the example, drill bit .9 mm will be used for both .889 mm and .9 mm. Below is a list of all the possible drill bits. Please record which drill bits will be needed in the Tools Needed section of the Capstone Milling Form. Available Drill sizes in mm 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2 2.1 2.2 2.3 2.4 2.5 2.6 2.95 3
Now you’re done and should submit the form to the technician for processing.
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