process_stencils

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process_stencils [2022/03/01 11:46] – benhprocess_stencils [2022/05/23 10:54] – benh
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 Before you start, you'll want to make sure that you have your solderpaste gerber files ready, along with your piece of polyimide. Note that we (typically) have either full 8x12 sheets, or a 24"-wide roll. If you need a full sheet, use one. Otherwise, use scissors to cut an appropriately-sized piece from the roll, making sure to leave enough room for a sizeable (~1 inch) frame/boarder around the design. Before you start, you'll want to make sure that you have your solderpaste gerber files ready, along with your piece of polyimide. Note that we (typically) have either full 8x12 sheets, or a 24"-wide roll. If you need a full sheet, use one. Otherwise, use scissors to cut an appropriately-sized piece from the roll, making sure to leave enough room for a sizeable (~1 inch) frame/boarder around the design.
  
-  - Log into the ProtoLaser. Turn on the tool and/or start the software if they are not already on and running.+  - Log into the ProtoLaser. Turn on the tool and/or start the software if they are not already on and running. Brush off the processing surface; it needs to be clear of debris so that the polyimide can sit flat.
   - Start a new project ("File" > "New").    - Start a new project ("File" > "New"). 
   - Select the "Stencil" template. (Note: I'm not sure what the "short" version is, so just use the regular one.)   - Select the "Stencil" template. (Note: I'm not sure what the "short" version is, so just use the regular one.)
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 **NOTE!!** The human eye is very good at detecting mismatched edges! However, this process is surprisingly tolerant, especially with regular-pitch components. Try not to be too picky. You can also always reflow again, or cut traces later if needed. It's a bit of trial and error to get a feel for this. **NOTE!!** The human eye is very good at detecting mismatched edges! However, this process is surprisingly tolerant, especially with regular-pitch components. Try not to be too picky. You can also always reflow again, or cut traces later if needed. It's a bit of trial and error to get a feel for this.
 +
 +One other thing to note about this process is that it's extremely likely that it will look like the pads are shorted together, i.e. the paste will connect across pads. This is typically okay! When the paste melts, it will naturally wick to the nearby copper, which is hotter than the soldermask and/or the bare FR4. **BE AWARE!!** If you have a bare board, i.e. without soldermask, it's critical to etch copper away from between the pads, or you //**will**// get shorted pads later. This must be done prior to board fabrication. (Soldermasking can be attempted with Kapton tape, but YMMV and it's a very unsupported process. See [[process_kaptonMask|this page]] for how you can try that.)
  
 After the paste is applied to your satisfaction, move your board and all the components for placement to near where the reflow will happen (either a bench with a reflow station if you're a masochist, or near the reflow oven in the semi-clean room). You want to do the actual placement of components near to where the reflow will happen because the less you need to move the board with all your non-soldered-on components, the better. Using tweezers (we have plenty upstairs), place each component onto the PCB in the proper position. Double check the component //and orientation// prior to placement! You'll be sad later if you discover you put a key IC on backwards and fried it. Pin 1 is often indicated with a dot.  After the paste is applied to your satisfaction, move your board and all the components for placement to near where the reflow will happen (either a bench with a reflow station if you're a masochist, or near the reflow oven in the semi-clean room). You want to do the actual placement of components near to where the reflow will happen because the less you need to move the board with all your non-soldered-on components, the better. Using tweezers (we have plenty upstairs), place each component onto the PCB in the proper position. Double check the component //and orientation// prior to placement! You'll be sad later if you discover you put a key IC on backwards and fried it. Pin 1 is often indicated with a dot. 
  • process_stencils.txt
  • Last modified: 2024/03/03 12:48
  • by benh