pcb-tips

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pcb-tips [2020/09/08 12:30]
benh created
pcb-tips [2022/07/15 16:02] (current)
benh
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-Processing ​tips! +==== Miscellaneous processing ​tips! ==== 
-ProtoMat: +//So you made a few boards. ​Or not! Either waythis 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 themThis is basically ​the Institutional Knowledge of the LPKF equipment ​at The HiveWe make no guarantee ​with any of thesebut we have found that they'​ve helped us in some way//\\
-  * Use the “ProtoLaser – ProtoMat – Double Sided – NoTHP” template +
-  * Orient all your boards ​*before* creating any fiducials. +
-  * 4 fiducials – always. +
-  * Do not forget to save before the toolpath! +
- +
-ProtoLaser:​ +
-  * 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.) +
- +
-Electroplater:​ +
-  * Clean with IPA and a TexWipe before beginning processing. +
-  * If you would like to adjust ​the plating time, ask a PI to put you in touch with an MPI. +
-  * Do not let your substrate sit in the bath (any bath) for very long after the timer runs out. +
-  * If the machine throws an error on startup, it’s likely a bath needs to be topped off. Get a PI to help. +
-  * After bath 3 (activator):​ +
-    * Swipe a “reasonable” amount off with squeegee (mostly just don’t want it dripping) +
-    * Dry for 20+ mins at 150F(Higher than this can cause the ink to bake into the copper.) +
-    * 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. +
-  * Bath 5: +
-    * If the current drops to zero or is very low (<10A reverse): +
-    * First attempt to re-seat the PCB holder (i.e. take PCB holder out and put back onto pegs) and try again. +
-    * If that doesn’t workyou may need to sand down the PCB holder’s pegs that hold the substrate to the holder (i.e. remove the board, rinse 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 bath, dry for 20+ minutes ​in the oven*** Place a towel underneath the board to prevent reactions between the oven shelf and the copper layers ***+
  
 +  * 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 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:
 +    * The best method is if your CAD program allows you to generate oval holes. Then just export those with your drill file (either plated or unplated) and it should work fine.
 +    * If you have square slots with a minimum dimension of at least 1mm AND they do not need plating, you 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.
 +    * 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 above, but instead of generating a "​Contour Routing"​ toolpath, you'd generate a "​Drills"​ toolpath with the new "​Slots"​ layer as the source file. Note 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.
 +    * 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. ​
 +  * If you're interested in optimizing your ProtoLaser experience, see 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 many) of which are likely beyond your control as a 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):
 +    * Flatness of your substrate
 +    * Laser power and other material-specific settings
 +    * Design choices (e.g. spacing, trace widths, substrate, copper thickness, etc.)
 +    * Position of the design on the substrate (left, right, center, etc.)
 +    * Cleanliness of the laser lens*
 +    * Level-ness of the floor*
 +    * Level-ness of the sample plate*
 +    * Filter cleanliness*
 +  * 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 size. Think 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 substrate) while keeping in mind that there are some things out of your control. Once 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 work. Try to hold as many systemic parameters constant as possible, e.g. the same position on the substrate, the same substrate piece, etc. 
 +  * 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.
 +  * For the laser, if 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.
 +  * Laser cannot do two-sided jobs with plating by itself; the plotter is required for fiducials. No idea why.
 +  * 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.
  
 +[[pcb-book-of-kane|The Book of Kane]]
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  • Last modified: 2020/09/08 12:30
  • by benh