PCB Tolerances in Fabrication
As we all know, PCB tolerances exist in every PCB fabrication aspect. When design a new product, you do so with a specific set of dimensions in mind, these are known as the nominal dimensions. You should know that the tighter or smaller the tolerance the higher the cost or longer lead time of manufacturing will be. For the industrial production of printed boards, there are international standards and these also the PCB tolerances.
Every PCB manufacturer has different PCB tolerances that affect an engineer’s target impedance control and stack-up. While not mandatory, it is extremely beneficial for the PCB designer to contact the PCB fabricator and PCB assembler as early as possible in the design and layout process to get a copy of the PCB tolerance requirements and stack-up. One of the benefits of working with a supplier like MADPCB is everything is managed under one-roof -design, engineering consultations, fabrication, component sourcing and assembly. Our specialty is in providing solution to the most complex design challenges and ultra-demanding applications -be that high-heat or critical-reliability standards. We supply these advanced technologies to you, transforming the old way you would order printed circuit boards; with MADPCB, there is no more need to manage multiple supplier relationships and account for miscommunication on aspects like component overages or tolerances.
MADPCB’s PCB Tolerances
During your design process, follow these printed circuit board tolerance guidelines to ensure the quality (and feasibility) of the manufactured PCBs is maximized. All of our circuit boards are built within valid IPC guidelines and standards, typically IPC-A-600 Class 2 standards. HDI boards can be produced with smaller tolerances. To help you understand where these PCB tolerances originate from, we’ve created a series of informative guidelines as following.
| PCB Tolerances | ||
| Description | Tolerance | Notes |
| Materials -Rigid PCB | ||
| FR4 Base Materials | +/-10% | The information about the base material thickness exclusively defines the thickness of the dielectric including base copper. The other layer structure such as electroplated copper layers or solder mask layers result in increased final thickness. Refer to our CCL. |
| Aluminum Base Materials | +/-10% | |
| Copper Base Materials | +/-10% | |
| PTFE Base Materials | +/-10% | |
| Max Bow &Twist on Boards with SMDs | 0.75% | Please note that the twist and bow value is increased above averages, if the copper balance of the PCB is locally very unequal or if the circuit board is very thin. Refer to our PCB Materials. |
| Ma Bow &Twist on Boards without SMDs | 1.5% | |
| Rigid PCB Thickness | ||
| Producibility Level B (standard) |
+/-10% or +/-0.178mm |
Thickness tolerances for pressed multilayer according to IPC-2222A. When measured over metallization or coatings, those thicknesses and tolerances must be considered. |
| Materials -Flex PCB | ||
| Dielectric Thickness >=0.075mm | +/-10% | Specifications according to IPC-4204A. The information on the thickness of the flexible base material defines solely the dielectric thickness or adhesive thickness including base copper. The other layer structures such as e.g. copper plating or solder mask lead to an increased flex circuit final thickness. Refer to our FCCL. |
| 0.025mm<=Dielectric Thickness>=0.075mm | +/-10% | |
| 0.020mm<=Dielectric Thickness>=0.025mm | +/-12.5% | |
| Dielectric Thickness <0.020mm | +/-15% | |
| Adhesive Thickness>=0.075mm | +/-10% | |
| 0.025mm<=Adhesive Thickness>=0.075mm | +/-15% | |
| 0.020mm<=Adhesive Thickness>=0.025mm | +/-20% | |
| Adhesive Thickness <=0.020mm | +/-30% | |
| For woven or combinations with woven stiffener: Adhesive Thickness >=0.025mm | +/-20% | |
| Flex PCB Thickness | ||
| Flexible Part Thickness | +/-0.03mm | Refer to our Flexible Circuit |
| Flexible Part + Stiffener Thickness | +/-0.05mm | |
| Trace (/Conductor) | ||
| Width Tolerance | +/-15% (min 1.5mil) | |
| Spacing Tolerance | +/-15% (min 3mil) | |
| Drilling | ||
| Production Hole Oversize – Plated | 0.10mm | Refer to our PCB Vias and Microvias |
| Production Hole Oversize – Non-Plated | 0.00mm | |
| Plated Thru-Hole (PTH) Size |
<=4.00mm: +/-0.075mm >4.00mm: +/-0.125mm |
|
| Non-Plated Thru-Hole (NPTH) Size |
<=4.00mm: +/-0.05mm > 4.00mm: +/-0.10mm |
|
| Hole Position Tolerance | 0.10mm | |
| Min Hole to Hole Distance | 0.25mm | |
| Min NPT Production Hole to Copper | 0.25mm | |
| Hole Wall Copper | ||
| Average Copper Thickness |
Via: >=20μm Microvia: >=12μm |
|
| Pad Size | +/-20% | |
| Routing | ||
| Board Outline |
Standard: +/-0.25mm Advanced: +/-0.125mm Special: +/-0.075mm |
Refer to our Milling |
| Internal Cutouts |
Standard: +/-0.25mm Advanced: +/-0.125mm Special: +/-0.075mm |
Refer to our Slots &Cutouts |
| Copper Trace | ||
| Trace Width/Spacing | +/-20% | |
| Pad | ||
| Wiring Pad | >=0.3mm + Hole Dia. | |
| Non-Wiring Pad | >=0.4mm + Hole Dia. | |
| Surface Finish | ||
| Lead free HASL | 1-30μm (pad coverage) | Refer to our PCB Surface Finishes |
| Electroless Gold over Nickel (ENIG) |
Ni: 120-240μ’’ Au: 2-3μ’’ |
|
| Immersion Silver | 6-12μ” | |
| Plated Hard Gold over Nickel |
Ni: 100-200μ” Au: 30-50μ” |
|
| Solder Mask (SM) | ||
| On the PCB | >10μm but <27μm | This depends on the copper pattern classification, refer to our Solder Mask |
| On the Conductor Edge | >5μm but <25μm | |
| Min SM to Pad Clearance |
LDI -0.03mm Conventional -0.10mm |
|
| Min SM Trace Covering |
LDI -0.06mm Conventional -0.09mm |
|
| Min SM Web |
LDI -0.07mm Conventional -0.13mm |
|
| Min SM to Pad Clearance | 0.125mm | |
| Min Via Filling Finished Holes Size Resin or SM | 0.50mm | |
| SM Thickness on Conductor Edges | >7μm | |
| Coverlay | ||
| Coverlay Holes to Traces and/or Edges (Min) | >=0.13mm | Refer to our Coverlay |
| Coverlay to Pad (min) | 0.1mm | |
| Coverlay to Trace (min) | 0.1mm | |
| Coverlayer Width (min) | 0.25mm | |
| Stiffener Holes | ||
| NPTH Hole Diameter (min) on Stiffeners | >=0.25mm + Access Hole | |
| Legend | ||
| Min Line Width | 0.10mm | Refer to our Silkscreen |
| Min Height Legibility | 1.00mm | |
| Legend to SM Cut-Back (Clipping) | 0.10mm | |
| Break-Routing | ||
| Min Clearance PCB Edge to Copper Traces/Pads -Outer Layer | 0.40mm | Refer to our PCB Milling, and Slots and Cutouts |
| Min Slot Finished Width | 0.50mm | |
| Profile Dimensional Tolerance | +/-0.20mm | |
| Slot Dimensional Tolerance |
Width: +/-0.20mm Length: +/-0.20mm |
|
| Min Copper Around Plated and Non-Plated Slots | As copper ring | |
| V-Scoring/V-Cut | ||
| Max PCB Thickness for Scoring | 2.00mm | Refer to our V-Scoring |
| Min PCB Thickness for Scoring | +/-0.80mm | |
| Min Clearance PCB Edge to Copper Pattern | 0.45mm | |
| Profile Dimensional Tolerance after Separation | 0.30mm | |
| Rest Material | 0.45mm+/-0.10mm | |
| Positional Tolerance Upper to Lower Score | +/-0.25mm | |
| Min Score Depth | 0.15mm | |
| Edge Beveling | ||
| Nominal Bevel Angle | 30o+/-5o | |
| Rest Material | 0.25mm | |
| Via Fill | ||
| Max Via Fill Finished Hole Size | 0.50mm | Refer to our Via Protection |
| Peelable Mask | ||
| Min Width of Any Peel-off Element | 0.50mm | |
| Max Coverable Hole End-Size | 6.00mm | |
| Min Overlap on Copper Pattern | 0.60mm | |
| Min Clearance to Free Copper | 0.60mm | |
| Min Distance from PCB Outline | 0.50mm | |
| Tolerance on Position | +/-0.30mm | |
| Carbon Ink Printing | ||
| Min Carbon to Carbon Spacing | 0.40mm | Refer to our Carbon Ink PCB |
| Min Carbon Line Width | 0.30mm | |
| Min Carbon on Copper Overlap | 0.20mm | |
| Min Carbon on SM Overlap | 0.10mm | |
| Impedance Control | ||
| Rigid PCB Impedance Control Tolerance | +/-5%, +/-10% | |
| FPC Hatch Impedance Control Tolerance | +/-5%, +/-10% | |