7 Tips to Make Your PCB Quoting Experience Smoother

7-tips-smoother-pcb-quoting

I recently designed the hardware for a really cool wearable device being developed by another startup. I contacted several local manufacturers to get quotes on costs. During the process, I ran into several challenges that I’m definitely going to remember for next time. Here are 7 tips from my recent adventures that will make your next collaboration with a manufacturer go smoother!

  1. Clarify ahead of time if they’ll find orderable generic parts for you. Passive components, like resistors and caps usually comprise the majority of your BOM. It often doesn’t matter which manufacturer part number is used during assembly as long as your specs for each component are met. We all know how painful it is to find an orderable manufacturer part number for a 0.1uF X7R 0402 10V ceramic cap and then repeat this search for the 100 other passives on the BOM! Thankfully, many manufacturers will do this search for you, saving you a lot of time. But make sure to clarify ahead of time so that you’re not surprised.One of Upverter’s superpowers is the Generics feature. It lets you put down generic parts (mostly passives) on your schematic without having to create a specific part in the library or worry about the manufacturer part number in that moment. You simply specify the value and specs you care about and move forward with designing.
  2. Make it clear whether or not you are okay with the manufacturer “upgrading” generic passives. For example, in my schematic, I specified that several caps should be rated for at least 6V since they were decoupling a 3.3V rail. But there were other caps in the design that had all of the same specs with the exception of being rated for at least 10V. It might be cheaper for the manufacturer to order only 10V caps so let them know they can make “upgrades” like this. This sort of thing often happens with capacitor temperature coefficients and resistor/cap tolerances.
  3. Make sure all your passive component values are real! Resistor and capacitor values are mostly standardized but sometimes, you have to calculate exact values for your particular application. For example, you may have to calculate resistor values to set the output voltage of an LDO. Or a capacitor value to set the soft-start on a switching power supply. Just remember to choose the closest orderable value at the end so the manufacturer isn’t confused. Manufacturers don’t like to make assumptions on your behalf. The less back-and-forth you have with them, the faster you can have your board built.For caps, in addition to making sure your chosen value is a standard one, there are other attributes (like voltage rating, tolerance, temperature coefficient, dielectric, etc.) that you should confirm are orderable from your distributor.
  4. Consolidate identical parts onto the same line in the BOM. This makes both yours and the manufacturer’s life easier since the BOM is shorter and more organized.
  5. Get their PCB fab capabilities, specifications, and DFM constraints up front. You need to know this stuff before starting the layout. It will be a huge pain to fix your board if you use a trace width or hole size that the manufacturer doesn’t support. I know that sounds obvious but you’d be surprised how often this gets overlooked. But what if you haven’t chosen a specific manufacturer by the time your layout starts? Here’s a list of conservative guidelines I averaged between 6 different manufacturers. If you follow these specs, you can be assured that the majority of manufacturers will have no problem making your board:
    • Trace width/spacing = 8 / 8 mils
    • Minimum annular ring = 6 mils
    • Minimum hole size = 12 mils (10 mils is usually fine)
    • Copper to board edge clearance = 40 mils (20 mils is usually fine)
    • Component to board edge clearance = 100 mils
    • SMT component to SMT component clearance = 20 mils
  6. If you want to get a rough idea of cost before your layout starts, you can directly ask your manufacturer(s) for it. You’ll just need to supply the following information (They will update the quote when they have your finalized gerbers but it shouldn’t change much):
    • PCB dimensions (LxW)
    • PCB thickness (0.62 inches is standard)
    • Number of layers
    • Copper weight (1 oz is common)
    • Soldermask colour (default is usually green)
    • Controlled impedence traces? Yes or no
    • Double-sided SMT? Yes or no
    • Number of through hole components
    • Number of fine-pitched SMT components (pitch < 0.5mm)
    • Number of BGA/QFN/Leadless SMT components
    • Number of remaining SMT components
    • Number of unique manufacturer part numbers on the BOM
    • Completed BOM

    Remember, Upverter’s Design Report feature gives you much of this information from the design’s Project page!

  7. Clarify with the manufacturer if they will take care of panelizing and adding guide rails. Their assembly equipment needs to grab onto the sides of the PCB. So if you have components within 250 mils of the board edge, they usually add extra strips of PCB material (called rails). This may make your PCB more expensive since potentially, fewer boards can be added to a panel. So just be aware of this.

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