pcb-tips

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pcb-tips [2021/01/13 22:35]
benh
pcb-tips [2022/07/15 16:02] (current)
benh
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 ==== Miscellaneous processing tips! ==== ==== Miscellaneous processing tips! ====
 +//So you made a few boards. Or not! Either way, this is a running list of tips and tricks for users - things to do and things to avoid, in absolutely no order whatsoever other than the order in which we discovered them. This is basically the Institutional Knowledge of the LPKF equipment at The Hive. We make no guarantee with any of these, but we have found that they'​ve helped us in some way. //\\
  
-Some additional notes on board design and fabrication:​ 
-  * Slots are hard in this process. Please consider using a single drill hit that’s wide enough if possible. If it’s unavoidable,​ the current recommended option is to use overlapping drill hits. 
   * Plating is typically avoidable by making vias with a diameter of 40 mil (1 mm). A standard 0.1” header pin can then be pushed through and soldered on both the top and bottom. ​   * Plating is typically avoidable by making vias with a diameter of 40 mil (1 mm). A standard 0.1” header pin can then be pushed through and soldered on both the top and bottom. ​
-  * Higher polygon isolation will reduce the chance of bridging to a plane during assembly (since we don’t really offer soldermask). However, it will also increase etch time. +  * Higher polygon isolation will reduce the chance of bridging to a plane during assembly (since we don’t really offer soldermask). However, it will also increase etch time because more of the substrate will be etched. "​Isolataion"​ is usually a setting that you can edit per specific polygon; 10 mil is the default often, but 24 or 32 mil (or more, though the benefits decrease) will reduce the risks further.  
- +  * Slots! We can do them! Here are a few methods for doing them: 
-ProtoMat: +    The best method is if your CAD program allows you to generate oval holesThen just export those with your drill file (either plated or unplated) and it should work fine
-  * Use the “ProtoLaser – ProtoMat – Double Sided – NoTHP” template +    If you have square slots with a minimum dimension of at least 1mm AND they do not need platingyou can add the slots in the same layer as the board's outline in your CAD software such that they get plotted onto the Gerber that gets assigned to the "​BoardOutline"​ layer in the LPKF CircuitPro software(You can also just put the slots onto a completely different layer in your CAD program, generate an additional Gerber for that layer, and then in the LPKF software, import it onto either the "​BoardOutline"​ layer or onto its own layer.) Once in the LPKF software, if your slot are on the "​BoardOutline"​ layer, select the outline ​of all slots that are currently on the BoardOutline layer and move them to a new layer that you create in the "​Layers"​ pane (making sure that the "​BoardOutline"​ layer is selectable has helped us to select the path in question, and then right-click on one of them to reach the "​Assign to layer..." submenu). Once that's done, and you're ready to generate your toolpath (save first!), generate the entire toolpath as you would normally first, and then go back into the toolpath generation window. Deselect everything but the "​Contour Routing"​ step. Click "Show details"​ under that step. Select the layer you have the slots on as the "​Source",​ the "1mm contour router"​ as the tool, "No Gaps" for the number/​style of breakout tabs, uncheck "​Replace existing toolpath",​ and check "​Inside"​ (rather than "​Outside"​). Note that sometimes changing one of these resets the others, so double check these settings prior to pressing "​Start"​ to generate the additional toolpath
-  Orient all your boards *before* creating any fiducials. +    Plated square slots have not been demonstrated yet, but my guess would be that if they have a minimum dimension of at least 1mm, then you can use a similar method ​to the un-plated square slots from abovebut instead of generating ​"​Contour Routing"​ toolpath, ​you'd generate a "​Drills"​ toolpath ​with the new "​Slots"​ layer as the source fileNote that in this situation, ​the slot would have to be converted to a polygon first (right-click and select "​Convert to polygon"​ if it's not already one). YMMV here. 
-  * 4 fiducials – always+    * Overlapping drill hits can be used as a rough approximation ​for a slot, and get definitely be plated, by just putting them with the other plated holes.  
-  Do not forget to save before the toolpath! +  * If you're interested in optimizing your ProtoLaser experiencesee the [[https://​gtvault.sharepoint.com/:​b:/​s/​HiveMakerspace/​EZGQyfhrC0BItpbSxd_rjRQBzDyNWUubu-RCuJr6a3OI9A?​e=8kXjaA|LPKF ProtoLaser Optimization]] document for more information
- +  * Laser precision is dictated by many things, some (even manyof which are likely beyond your control as user. Here is a completely-uncomplete list of some of these things ​(a * indicates things that you, as a user, will not be able to adjust, but get in touch if you think it's a major contributor to any issues you're seeing): 
-ProtoLaser:​ +    * Flatness of your substrate 
-  * Sometimeswhen placing ​the board, the fiducials move in the opposite direction ​as the board. ​This is a known bug! You can either: try estimating ​the location ​of the fiducials ​and starting the process; start a new document; restart ​the software; or restart ​the hardware(The latter two require a fresh 20 minute warmup for optimal performance.) +    * Laser power and other material-specific settings 
- +    * Design choices ​(e.g. spacing, trace widths, substrate, ​copper ​thickness, etc.) 
-Electroplater:​ +    * Position ​of the design on the substrate (left, right, center, etc.) 
-  * Clean with IPA and a TexWipe before beginning processing+    * Cleanliness of the laser lens
-  If you would like to adjust ​the plating timeask PI to put you in touch with an MPI. +    * Level-ness of the floor* 
-  * Do not let your substrate sit in the bath (any bath) for very long after the timer runs out+    * Level-ness of the sample plate* 
-  * If the machine throws an error on startupit’s likely a bath needs to be topped offGet a PI to help+    * Filter cleanliness* 
-  * After bath 3 (activator)+  * One way to minimize systematic errors from the laser system itself is to do what might be termed a "dose test"This would involve make a very small design that has one or more features at and/or around your actual design'​s minimum feature sizeThink something that can be etched in a minute or two. You develop your material settings on this design so that you can try many iterations of material settings within a shorter time frame (and you can likely fit many of them on a single sheet of your substratewhile keeping in mind that there are some things out of your controlOnce you've determined settings ​that seem to work, do a test etch of the dose-test design prior to etching your actual design. If done properly, this can tell you if the etch will be up to spec for your workTry to hold as many systemic parameters constant as possible, ​e.g. the same position on the substrate, the same substrate piece, etc.  
-    * Swipe “reasonable” amount off with squeegee ​(mostly just don’t want it dripping+  Another suggestion for the laser would be to define a metric for etch quality using the aforementioned test design. That way, you can quantitatively determine which parameters are doing better than others
-    * Dry for 20+ mins at 150F. (Higher than this can cause the ink to bake into the copper.) +  * For the laserif you're using a substrate thinner than 5 mil (0.125mm), tabs in your design are a near-requirement! You can make them in the laser. 
-    * When rinsing after drying (after “bath 4”), scrub the copper surface with a sponge to remove as much of the dried activator off the copper as possible+  ​Laser cannot do two-sided jobs with plating by itself; the plotter is required for fiducials. No idea why. 
-  Bath 5: +  ​You can actually make boards with more required bits than the tool magazine has slots. It will yell at you about it, but just walk through ​the process as normal ​and it will ask you to put the bits into the magazine when it needs them.
-    * If the current drops to zero or is very low (<10A reverse): +
-    * First attempt to re-seat the PCB holder (i.etake PCB holder out and put back onto pegsand try again. +
-    * If that doesn’t ​work, you may need to sand down the PCB holder’s pegs that hold the substrate ​to the holder (i.e. remove ​the boardrinse it, and then sand down the holder before restarting ​the acid bath step)+
-    Don’t forget ​to screw down the holder into place+
-  * After final bathdry for 20+ minutes ​in the oven. *** Place a towel underneath ​the board to prevent reactions between ​the oven shelf and the copper layers *** +
  
 +[[pcb-book-of-kane|The Book of Kane]]
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  • Last modified: 2021/01/13 22:35
  • by benh