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Circuit Boards Specifications

PCB designers often haven’t been in a printed circuit board manufacturing setting. With a good design there are processing limitations to be considered to build a quality product consistently. When considering your PCB design, using a Free DFM service such as Epec’s will save you cost, time, and prototyping.

  Standard Advanced
Annular Ring - holes are drilled larger than the finished size required to meet the tolerances. 0.005 over the finish size in most cases. +\-0.003 is the standard plated hole tolerance.
Internal Minimum Pad Size 0.014" larger than finished hole size 0.012" larger than finished hole size w/tear drop. Half-ounce ONLY
External Minimum Pad Size 0.014" larger than finished hole size 0.014" larger than finished hole size w/tear drop. Half-ounce ONLY
Increase pad size accordingly for annular ring requirements greater than 0.001" such as CLASS III product or press fit holes.
Holes requiring greater than 0.001" copper (0.0007 per IPC) - (i.e. 2oz base plated to 4oz finish) require additional 0.004 pad diameter.
Plane Layer Clearance
PTH & NPTH Hole Clearance to Plane 0.030" larger than finished hole size 0.020" larger than finished hole size
(0.10" per side over FHS)
PTH & NPTH Hole to Inner Layer Trace 0.015" Spacing 0.010" Spacing (edge-to-edge)
Line Width and Space - mixed copper technology is not included in the parameters below.
Inner layer width on 1/4 ounce copper Minimum -0.004" Minimum -0.003"
Inner Layer Line width on H ounce copper Minimum -0.003" Minimum -0.0025"
Inner Layer Line width on 1 ounce copper Standard -0.005" Minimum -0.004" Half-ounce ONLY
Inner Layer Line width on 2 ounce copper Minimum -0.008" Minimum -0.008"
Inner Layer Line width on 3 ounce base copper or greater Minimum -0.012" Minimum -0.012"
Outer Layer Line width on H ounce base copper Minimum -0.004" Minimum -0.004"
Outer Layer Line width on 1 ounce base copper Minimum -0.005" Minimum -0.004" Half-ounce ONLY
Outer Layer Line width on 2 ounce copper Minimum -0.008" Minimum -0.008"
Outer Layer Line width on 3 ounce base copper or greater Minimum -0.012" Minimum -0.012"
Inner layer Feature to Feature on 1 ounce or less base copper Minimum -0.005" Minimum -0.004" Half-ounce ONLY
Inner layer Feature to Feature on 2 ounce Base Copper Minimum -0.008" Minimum -0.008"
Inner layer Feature to Feature on 3 ounce copper or greater Minimum -0.012" Minimum -0.012"
Outer layer Feature to Feature on 1 ounce or less base copper Minimum -0.005" Minimum -0.004" Half-ounce ONLY
Outer layer Feature to Feature on 2 ounce Base Copper Minimum -0.008" Minimum -0.008"
Outer layer Feature to Feature on 3 ounce copper or greater Minimum -0.012" Minimum -0.012"
Trace to Plane Spacing Minimum -0.008" Minimum -0.008"
Feature to Board Edge *does not include tabs Minimum -0.010" Minimum -0.008"
Feature to Score Edge Minimum -0.020" Minimum -0.015"
Solder Mask - Liquid Photo Imageable Mask. Some color mask such as White, Black, or Blue have additional requirements.
LPI Conductor Overlap 0.015" Larger Than Feature Size 0.010" Larger Than Feature Size
LPI Mask Clearance 0.015" Minimum 0.013" Minimum
LPI Mask Web 0.005" Minimum 0.005" Minimum
Less than 4 mil web between component pins may result in loss of mask between SMT pads.   Decrease clearance to 5 mil, then web to 3.5mil, then clearance to 4 mil, etc.
Silkscreen
Silk Screen Ink 0.008" minimum aperture 0.006" minimum aperture
Copper Features (ETCHED TEXT) 0.010" minimum aperture 0.010" minimum aperture
Font Height 0.065" minimum height 0.045" minimum height

If the specifications of a board design fall into the advanced category, it may be subject to additional charges.

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