What is PCB Tolerances
PCB Tolerances refer to the deviations in size, thickness, angle, value and other parameters between the actual Printed Circuit Boards produced by PCB manufacturer and the drawings from customer. For examples, a PCB is design as 1.6mm thickness, PCB manufacturer cannot make sure all the PCBs are exactly 1.6mm thickness, individual PCB may be thicker or thinner than 1.6mm. Then there should be a tolerance. For 1.6mm PCB, the tolerance should be ±0.16mm normally, or as low as ±0.1mm or less in special requirement.
Generally speaking, tighter tolerance means higher manufacturing difficulty and lower yield rate. But at the same time, tighter tolerance means better function reliability. PCB tolerance requirements also change depending on the application and environment. For example, if a PCB is intended for use in aerospace, it may require much tighter PCB tolerances than those for use in consumer products. Therefore, PCB Tolerances must also be considered when designing PCBs, as any discrepancies may result in a poorly functioning PCB.
Except the requirements from the customer’s drawings, there are also well-known industry standards for PCBs, the most commonly used is IPC-A-600. PCB manufacturers should adhere to IPC-A-600 standards regarding PCB tolerance requirements and acceptance standards. By strictly adhering to PCB tolerance requirements, PCB manufacturers can ensure the quality and performance of PCBs.
In Viasion, we strictly follow customer’s requirement and IPC-A-600 Class 2 and Class 3/3A standards in tolerances, to delivery the highest quality PCBs to our customers. Please refer fer to the most commonly used tolerances for printed circuit board production as below.
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| DESCRIPTION | TOLERANCE | NOTES |
|---|---|---|
| Material thickness | ≤1.0mm:±0.1mm | |
| | ＞1.0mm: ±10% | Best: ≤2.0mm ±0.1mm; 2.1-3.0mm ±0.15mm; 3.1-7.0mm +/-0.25m |
| Flexible PCB Thickness | +/-0.025mm | Stiffener area: +/-0.05mm |
| Maximum Bow and Twist | 0.75% | |
Drilling
| DESCRIPTION | TOLERANCE | NOTES |
|---|---|---|
| Plated Hole Size (PTH) | ≤4.00mm +/- 0.75mm | Best: +/- 0.05mm |
| | >4.00mm +/- 0.10mm | |
| Non-Plated Hole Size (NPTH) | ≤4.00mm +/- 0.05mm | |
| | >4.00mm +/- 0.10mm | |
| Plated Slot Size by Dril (PTH Slot) | +/- 0.1mm | Best: +/- 0.75mm |
| Non-Plated Slot Size by Dril (NPTH Slot) | +/- 0.075mm | Best: +/- 0.05mm |
| Hole Position | +/-0.075mm | |
| Back drill Deepth | +/-0.1mm | |
| Contersink Hole Angle | +/- 10° | |
| Contersink Hole Size Size | +/-0.15mm | |
| Aspect Ratio | 1:18 | Drill size: PCB thickness |
Hole Wall Copper
| DESCRIPTION | TOLERANCE | NOTES |
|---|---|---|
| Minimum Copper Thickness | 20μm for IPC A-600 Class 2 | 25μm for IPC A-600 Class 3 |
Surface Finish Thickness
| DESCRIPTION | TOLERANCE | NOTES |
|---|---|---|
| HAL lead free | 2 – 40μm | |
| Immersion gold (ENIG) | Ni:3- 8 μm; Au: 0.05 – 0.10μm | |
| Immersion Silver | 0.2 – 0.4μm | |
| Immersion Tin | >=1.0um | |
| OSP | 0.1-0.3um | |
| ENEPIG | Ni:3-8um Pa:0.05-0.15um Au:0.05-0.1um | |
| Plating gold | Ni: 3 – 6μm; Au: 0.1- 4μm | |
| Carbon Ink | 0.10–0.35mm | |
| Peelable Mask | 0.20–0.80mm | |
Soldermask
| DESCRIPTION | TOLERANCE | NOTES |
|---|---|---|
| Min. Soldermask to Trace Clearance | 0.05mm | |
| Min. Soldermask Track Cover | 0.05mm | |
| Min. Soldermask Web | 0.075mm | |
| Thickness on Copper Trace | 10-18um | |
| Thickness on Edge of Copper Trace | >10μm | |
Legend/Silksreen
| DESCRIPTION | TOLERANCE | NOTES |
|---|---|---|
| Minimum Width | 0.10mm | |
| Minimum Height | 1.00mm | |
Routing/Profiling
| DESCRIPTION | TOLERANCE | NOTES |
|---|---|---|
| Min. trace/pad to outline – Outer Layers | 0.15mm | |
| Min. trace/pad to outline – Outer Layers | 0.20mm | |
| Profile Dimensional Tolerance | +/- 0.13mm | Best: +/- 0.13mm |
Scoring/V-Cut
| DESCRIPTION | TOLERANCE | NOTES |
|---|---|---|
| Maximum PCB Thickness | 3.20 mm | |
| Minimum PCB Thickness | 0.60mm | |
| Min. V-cut Copper Distance | 0.3mm | |
| Difference after Separation | +/-0.20mm | |
| Normal Rest Material | 0.50mm +/- 0.10mm | |
| V-cut Positional Tolerance top to bottom | +/- 0.1mm | |
| Minimum Score Depth | 0.1mm | |
Edge Beveling
| DESCRIPTION | TOLERANCE | NOTES |
|---|---|---|
| Bevel Angle Tolerance | +/- 5° | 15°, 30°, 45°, 60° |
| Remain Material Thickness Tolerance | +/-0.1mm | |
Imepdance
| DESCRIPTION | TOLERANCE | NOTES |
|---|---|---|
| Impedance Tolerance | +/- 10% | +/- 5% |
Electrical Test
| DESCRIPTION | TOLERANCE | NOTES |
|---|---|---|
| Minimum Test Pitch | 0.10mm | |
| Smallest Testable Pad | 0.05mm | |
| Test Voltage | 500V | |
| Test Current | 200 mA | Adjustable |
| Continuity Test | Min. 5Ω | |
| Isolation Test | Max. 500 MΩ | |
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