So that you’ve just accomplished your PCB design, and also you’re about ready to send these CAD files over to the fabrication house. However there’s just one problem-you’ve designed a new form factor with unusual specs, and you’ve got a nagging feeling that you must probably check those dimensions and tolerances before you pick a manufacturer.
However where do you start? Which numbers are most essential to consider when designing for manufacturing? In this post, we’ll walk you through the different dimensions and tolerances to consider for the manufacturability of your PCB design.
Board Dimensions
Board measurement will have a direct impact on the price of manufacturing your PCB. Here’s a quick list of the naked board dimensions which can be critical to the fabrication house:
Board size (LxW): On the end of the day, your PCB will must be cut from a bigger slab of material. For single board processing, the minimum dimension of the longest edge of a single board acceptable by most manufacturer conveyors is 2.zero”. For smaller boards, panelization is typically required.
Number of layers: The more layers you have the more your board will cost. 1–2 layers is pretty normal, 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 inside layers. 0.020″ of inner layer clearance is fairly normal, with premiums available for tighter tolerances.
If your PCB is towards the extremes (large or small) of the form factor spectrum, it is likely to be a good idea to check the minimum and maximum board size necessities of the producer you need to use. The minimal and most dimensions of the board itself may also be affected by growing the number of layers.
Panelization Considerations
Panelization helps manufacturers keep costs down by permitting you to arrange a number of boards on a single panel for processing by means of a manufacturing line. Listed below are the vital dimensions and tolerances you want to know to incorporate panelization into your design:
Panel dimension: 18 x 24 inch panels are customary, with ½ inch perimeter of clearance for double sided boards. Such a panel would possibly fit a most single board dimension of 16 x 22 inches.
Routing/Scoring clearances: There’s a ± 0.010 inch tolerance on board outlines and inside cutouts, with 0.one hundred inch spacing between individual PCBs for tab rout spacing.
Both you and your manufacturing house benefit from eliminating the amount of wasted material on the panel. You can select the panel to your PCB design after picking one of the normal formats available at 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 familiar with both imperial and metric units, as well because the drill gauge system.
Production gap oversize: In case 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. four mil or 0.10 mm for PTH).
Frequent hole tolerances: You’ll generally be fine going with the minimal hole dimension really useful by your fabrication house for vias, typically 0.three–0.4 mm
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