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--- pcb-tips [2021/01/13 22:35] – benh
+++ pcb-tips [2022/06/27 11:30] – benh
@@ Line 1: / Line 1: @@
 ==== 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. 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.
-  * 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! There are probably a couple of methods for doing this, but the way we've had success is to add the slots onto the "BoardOutline" layer in the software. How this happens depends on your EDA (CAD) software, but in essence, you either need to have your slot in a new gerber (which you can assign to "BoardOutline" in the Import step) or you need to put your slots onto the layer in your EDA that spits out your Board Outline gerber file (in Eagle, this layer is called "Dimensions"). Unfortunately, we haven't found a good way to do plated slots because in the above method, the slot is made //after// the etching is done (and therefore after the plating would be done). An alternative in this case would be to design your slot as overlapping drill hits which are done prior to plating.
-ProtoMat:
+  * 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.
-  * Use the “ProtoLaser – ProtoMat – Double Sided – NoTHP” template
+  * 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):
-  * Orient all your boards *before* creating any fiducials.
+    * Flatness of your substrate
-  * 4 fiducials – always.
+    * Laser power and other material-specific settings
-  * Do not forget to save before the toolpath!
+    * Design choices (e.g. spacing, trace widths, substrate, copper thickness, etc.)
+    * Position of the design on the substrate (left, right, center, etc.)
-ProtoLaser:
+    * Cleanliness of the laser lens*
-  * Sometimes, when 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.)
+    * Level-ness of the floor*
+    * Level-ness of the sample plate*
-Electroplater:
+    * Filter cleanliness*
-  * Clean with IPA and a TexWipe before beginning processing.
+  * 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.
-  * If you would like to adjust the plating time, ask a PI to put you in touch with an MPI.
+  * 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.
-  * Do not let your substrate sit in the bath (any bath) for very long after the timer runs out.
+  * 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.
-  * If the machine throws an error on startup, it’s likely a bath needs to be topped off. Get a PI to help.
+  * Laser cannot do two-sided jobs with plating by itself; the plotter is required for fiducials. No idea why.
-  * 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 work, you 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 ***
+[[pcb-book-of-kane|The Book of Kane]]