Home ≫ PCB Process Capability ≫ PCB Specification
PCB Specification Guide
Before a board gets quoted, the specification is what determines whether it can actually be built the way it’s designed — trace width, drill size, annular ring, board thickness, and the IPC Class the finished board needs to meet.
Get these right early, and manufacturing is routine. Get them wrong, and a design that looked fine on screen comes back with a DFM flag or a blown budget.
Table of Contents
What does “PCB specification” actually cover?
It’s the full set of dimensional and tolerance parameters that define whether a board design is manufacturable as drawn: minimum trace width and spacing, drill and via size, annular ring, board thickness and its tolerance, copper weight, and the IPC Class (2 or 3) the finished board is held to.
Every one of those parameters interacts with the others — tighter trace/space usually means a different drill strategy, thicker copper changes achievable trace width, and IPC Class 3 tightens nearly every tolerance in the list at once. Getting specification right isn’t about picking the tightest numbers available; it’s about matching each parameter to what the design actually needs.
Where This Fits
This page is one of five capability areas covered in depth on our PCB Process Capabilities hub — the reference layer underneath every product page on this site.
If you’re comparing specification against impedance control, surface finish, base material, or cost trade-offs, start there for the full picture; this page goes deep on specification alone.
Core Specification Parameters
The dimensional and tolerance parameters that define manufacturability
| Parameter | Standard Process capability | Advanced / fine-pitch capability | Why it matters |
| Minimum trace width/spacing | 4mil/4mil | 2.5mil/3mil and tighter (HDI construction) | Determines routing density and directly trades off against yield |
| Minimum drill diameter (mechanical) | 0.20mm (8 mil) mechanical drill | 0.10–0.15mm (laser-drilled microvia) | Smaller drills cost more and limit aspect ratio(Note: Laser drilling is suitable for HDI microvias and must be processed on the HDI production line) |
| Annular ring | 4 mil minimum | 3 mil and tighter with tighter registration control | Too little annular ring risks a broken connection if drilling drifts even slightly |
| Aspect ratio (board thickness: drill diameter) | Up to 9:1 | 12:1 and higher with controlled-depth or laser drilling | High aspect ratio makes reliable plating through the hole harder to achieve |
| Copper weight tolerance | ±10% of nominal | Tighter with additional process control | Affects both current-carrying capacity and achievable trace width |
| Board thickness tolerance | ±10% of nominal | ±5% with additional process control | Loose tolerance is fine for most designs; connector fit and controlled impedance need tighter control |
IPC Class 2 vs Class 3
IPC Class 2 covers general-purpose electronics where high reliability is expected but continuous, uninterrupted operation isn’t mission-critical — most commercial and industrial boards fall here.
IPC Class 3 is reserved for high-reliability electronics — think railway signaling, aerospace, medical, and safety-critical control systems — where extended field life and near-zero defect tolerance are required. The practical difference shows up in tighter annular ring and plating requirements, stricter inspection criteria, and more rigorous documentation at every stage of manufacturing.
For the full breakdown of what changes between the two classes and how to decide which one your project actually needs, see PCB Quality Standards: Understanding IPC Class 2 vs Class 3.
Board Thickness Options
Standard board thickness options run from roughly 0.4mm up through 3.2mm, with 1.6mm as the most common general-purpose default.
Thickness selection interacts with layer count, connector fit, and mechanical rigidity requirements — a thin board flexes more than a thick one, which matters for edge-connector applications, while a thick board may be the only way to fit a high layer count within reasonable copper-to-dielectric ratios.
For the full set of standard and non-standard thickness options and how to choose between them, see Typical PCB Thickness: Standard Options and How to Choose.
Specification by Product Line
Which specification parameters matter most depends on which product technology you’re building.
| Product line | Specification parameter that matters most | Product page |
| HDI PCB | Minimum trace/space and microvia drill diameter | HDI PCB manufacturing service |
| Multilayer PCB | Board thickness and layer-to-layer registration | Multilayer PCB manufacturing service |
| RF / High-Frequency PCB | Dielectric thickness tolerance (interacts with impedance, not specification alone) | High-Frequency PCB manufacturing service |
| Heavy Copper PCB | Copper weight tolerance and its knock-on effect on achievable trace width | Heavy copper PCB manufacturing service |
| High-Speed PCB | Board thickness tolerance and drill aspect ratio (backdrilling depends on both) | High-speed PCB manufacturing service |
Specification Requirements by Industry
Specification tolerances aren’t chosen in a vacuum — the industry a board is built for often dictates the IPC Class and tolerance floor before a single trace is routed.
Safety-critical applications：
Commonly require IPC Class 3 as a baseline, given the redundancy and failure-mode requirements these programs carry — see our Safety-critical PCB manufacturing page for how that plays out across fire safety, interlock, and control system applications.
Aerospace programs:
Frequently combine IPC Class 3 with DO-160/DO-254 qualification testing — see our Aerospace PCB manufacturing page for the fuller compliance picture.
Medical device programs:
Often need Class 3-equivalent reliability alongside ISO 13485 documentation, particularly for implantable and patient-contact devices — see our Medical device PCB manufacturing page for how specification and biocompatibility requirements interact.
Certifications & Documentation
Specification compliance isn’t just a manufacturing claim — it’s backed by a documented quality system with inspection records at each stage.
Every board is measured against its called-out specification before it ships, with the depth of documentation scaled to the IPC Class and industry the program requires.
Specification & Assembly
Bare-board specification is only half the manufacturability picture — the finished specification also has to be compatible with your assembly process.
Fine-pitch components need tighter solder mask registration than a through-hole connector does, and mixed-technology boards need specification tolerances that work for both.
See our PCB Assembly services overview for how specification and assembly capability fit together across turnkey, prototype, and mixed SMT/THT programs.
What you want to ask
Frequently Asked Questions
Q: Can you actually hold IPC Class 3 tolerances, or is that just a checkbox on a datasheet?
A: Class 3 tolerances are backed by inspection records and process controls specific to that class, not just a claim on a spec sheet. See our certifications page for the current quality certificates and inspection process behind that claim.
Q: What happens if my design doesn’t fit inside your standard specification limits?
A: We review it as part of the quoting process — some designs need a small layout adjustment, others genuinely need tighter process control than standard capability. Where a project also needs full component sourcing alongside a non-standard specification, our turnkey PCB assembly program is often the right path, since it puts engineering and sourcing on the same team from the start.
Q: Can I get a small batch built to verify my specification actually holds before committing to a full production run?
A: Yes — quick-turn prototype assembly exists specifically for this: validating that a design’s specification, fit, and function all hold up before you commit to volume.
Q: Does the specification I need change depending on whether I need SMT, through-hole, or mixed assembly?
A: Yes — fine-pitch SMT components need tighter solder mask registration than through-hole connectors do, and a board combining both needs a specification that works for either. See our mixed SMT/THT PCB assembly page for how that interacts with the specification choices covered above.
Other capability areas:
- PCB Impedance Control
- PCB Surface Finishes
- PCB Base Materials
- PCB Cost Drivers
Other Industries we serve:
- Automotive PCB manufacturing
- Datacom PCB manufacturing
- Industrial PCB manufacturing
- Power & Energy PCB manufacturing
- Railway PCB manufacturing
- Telecom PCB manufacturing
Contact us
Have a specification you need reviewed before you commit to a layout?
Send us your trace/space, drill size, and IPC Class requirements, and we’ll come back with a manufacturability review and quote.
Or contact us at: [email protected]
