So that you’ve just accomplished your PCB design, and you’re about ready to send these CAD files over to the fabrication house. But there’s just one problem-you’ve designed a new form factor with unusual specs, and also you’ve received a nagging feeling that you must probably check these dimensions and tolerances earlier than you pick a manufacturer.
But the place do you start? Which numbers are most necessary to consider when designing for manufacturing? In this publish, we’ll walk you thru the different dimensions and tolerances to consider for the manufacturability of your PCB design.
Board Dimensions
Board dimension will have a direct impact on the cost of manufacturing your PCB. Here’s a quick list of the naked board dimensions which might be critical to the fabrication house:
Board measurement (LxW): At the end of the day, your PCB will should be reduce from a bigger slab of material. For single board processing, the minimal measurement of the longest edge of a single board settle forable by most manufacturer conveyors is 2.zero”. For smaller boards, panelization is typically required.
Number of layers: The more layers you will have the more your board will cost. 1–2 layers is pretty standard, with some manufacturers going as high as 20 layers or more.
Thickness: Generally, there are thickness requirements associated with the board itself and its particular person internal layers. 0.020″ of internal layer clearance is fairly commonplace, with premiums available for tighter tolerances.
In case your PCB is towards the extremes (giant or small) of the form factor spectrum, it could be a good idea to check the minimal and maximum board dimension necessities of the producer you need to use. The minimal and most dimensions of the board itself may additionally be affected by increasing the number of layers.
Panelization Considerations
Panelization helps producers keep costs down by allowing you to prepare a number of boards on a single panel for processing by way of a producing line. Listed below are the essential dimensions and tolerances it is advisable know to incorporate panelization into your design:
Panel dimension: 18 x 24 inch panels are commonplace, with ½ inch perimeter of clearance for double sided boards. Such a panel might fit a maximum single board size of 16 x 22 inches.
Routing/Scoring clearances: There’s a ± 0.010 inch tolerance on board outlines and inner cutouts, with 0.a hundred inch spacing between particular person PCBs for tab rout spacing.
Each you and your manufacturing house benefit from eliminating the amount of wasted materials on the panel. You possibly can select the panel on your PCB design after picking one of many customary formats available on the fabrication house.
Drilling holes and vias in PCBs
There are a number of dimensions and tolerances to consider when drilling any holes in your PCB:
Drill diameters: Drills are often manufactured in increments of 0.05 mm (or 2 mils). You’ll wish to be acquainted with each imperial and metric units, as well as the drill gauge system.
Production gap oversize: Should you’ll be plating your througholes, it’s a good suggestion to oversize the drill a little to account for the thickness of the plating (e.g. 4 mil or 0.10 mm for PTH).
Widespread hole tolerances: You’ll generally be fine going with the minimum gap measurement really helpful by your fabrication house for vias, typically 0.3–0.4 mm
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