IPC Standards · Inspection · Acceptance Criteria
Bare Board PCB Quality & Acceptance Guide
Quality on a bare board is not a feeling — it is measurable conformance to agreed standards. This guide explains how IPC-A-600 and IPC-6012 define acceptability, what product classes change, where a certified fabricator verifies quality (AOI, electrical test, microsection, finish checks), and what you should specify to make acceptance objective on every order.
- IPC-A-600 · IPC-6012 The visual and performance standards your boards are accepted against
- 100% Electrical Test Every production board verified for opens and shorts before shipping
- ISO 9001 · IATF 16949 · UL An audited quality system behind every inspection step
Quick Answer · Scope · Acceptance Reference
What “Quality” Means for a Bare Board
This guide covers the bare board only — how its quality is defined by IPC standards, verified during fabrication, and accepted on receipt. Assembly-side quality (solder joints, placement, component authenticity) is a separate discipline with its own standards.
Bare board quality is measurable conformance to agreed acceptance standards — primarily IPC-A-600 (acceptability of printed boards, the visual and dimensional criteria) and IPC-6012 (qualification and performance requirements). A board is accepted against a defined product class, and that acceptance is backed by objective evidence: inspection records, electrical test results, microsections and thickness measurements. A board that merely “looks fine” has not been verified — appearance alone cannot see barrel cracks, thin plating or internal misregistration.
What This Guide Covers
- IPC-A-600 acceptability and IPC-6012 performance requirements
- Product classes (1 / 2 / 3) and what they change in practice
- In-process inspection: AOI, plating and registration checks
- Electrical testing — flying probe and fixture (bed-of-nails)
- Microsection, TDR impedance and finish thickness verification
- Quality documentation: CoC, test reports and inspection records
What This Guide Is Not
- Assembly-side quality — solder joints, placement, BGA X-ray
- Component sourcing, authenticity or counterfeit control
- Functional testing of the assembled product
- A substitute for the IPC documents themselves
- A fix for designs that violate fabrication DFM rules
Assembly quality — solder joint inspection, AOI/X-ray of populated boards, functional test — belongs to the assembly scope handled by our partner JHYPCB.For design-side rules, see our PCB DFM Guide.
Acceptance Criteria Quick Reference
| Criterion | Typical Reference | Why It Matters |
|---|---|---|
| Product class | IPC Class 2 standard; Class 3 on request | Class decides allowable defect criteria, inspection rigor and cost |
| Hole wall copper | Class 2 ≥ 20 μm avg; Class 3 ≥ 25 μm avg | Thin plating barrels crack under assembly reflow and thermal cycling |
| Annular ring | Class-dependent; breakout restricted, none for Class 3 | Breakout weakens the plated connection and long-term reliability |
| Bow & twist | ≤ 0.75% for SMT boards; ≤ 1.5% through-hole | Warped boards jam stencil printing and pick-and-place |
| Conductor width reduction | Localized reduction limited by class (typically ≤ 20%) | Over-etched or nicked traces change current capacity and impedance |
| Solder mask | No lifting, peeling, or exposed copper where mask is required | Mask defects cause solder bridges and corrosion in service |
| ENIG thickness | Ni 3–6 μm; Au ≥ 0.05 μm | Thin or porous gold leads to black pad and non-wetting at assembly |
| Electrical test | 100% opens/shorts against reference net list | The only test that proves every net is connected — and nothing else is |
References above reflect common industry interpretation, not a commitment for every construction. Your order confirmation states the acceptance standard and product class applied to your boards.
Inside the Factory · Six Checkpoints
Where Quality Gets Verified: Six Checkpoints
Quality is built in stages — each checkpoint below catches a different class of defect before it can reach your boards. Each card explains what is verified and links to a detailed article from our engineering blog.
Checkpoint 01 · CAM
Engineering Data Quality Control
Quality starts before production: Gerbers, drill data and stackup notes are checked line by line. Ambiguous or conflicting data caught here costs hours; caught later, it costs a re-spin.
QC of Engineering Data for Multilayer PCBCheckpoint 02 · In-Process
AOI After Patterning & Plating
Automated optical inspection compares every inner and outer layer against the design data, catching opens, shorts, nicks and over-etch while the panel is still repairable.
Pattern Plating & AOI in ProductionCheckpoint 03 · Coupons
Test Coupons & Impedance Verification
Coupons on the production panel carry the same plating and structures as your board. Microsectioned coupons prove hole copper thickness; TDR coupons verify controlled impedance.
TDR & Coupons for Impedance VerificationCheckpoint 04 · E-Test
Electrical Testing of Every Board
Flying probe or fixture testing compares every net against the reference data — the only step that proves connectivity. Boards that pass visual inspection can still fail here.
Testing, QC & Shipping in ProductionCheckpoint 05 · Final
Final Inspection & Acceptance
Visual and dimensional acceptance against IPC-A-600 for the stated product class: surface finish, solder mask, legend, holes, edges, warpage and cleanliness, then pack and ship.
IPC Standards for Manufacturing & AssemblyCheckpoint 06 · Reliability
Reliability & Stress Testing
For demanding builds, thermal stress, solder-float and bend testing demonstrate the board survives assembly and service — not just the final inspection bench.
Reliability Testing Standards & MethodsSee how boards are tested
Prototype and low-volume builds are verified with flying probe testing — no fixture cost, full net coverage: Flying Probe Testing for PCB.
Before You Order · Buyer’s Acceptance Checklist
Is Your Acceptance Criteria Defined?
Acceptance disputes happen when “quality” was never written down. These eight items make acceptance objective — define them on your fabrication drawing or purchase order, and verify them when the boards arrive.
| Check | Why It Matters | What Good Looks Like |
|---|---|---|
| Product class stated | Class decides allowable defect criteria and inspection rigor — without it, accept/reject calls are opinion. | “IPC Class 2” or “IPC Class 3” written in the fab notes and on the PO |
| Acceptance standard named | Naming the standard and revision prevents disputes over which criteria apply. | IPC-A-600 (current revision) referenced as the acceptance document |
| 100% electrical test required | Untested boards can carry opens and shorts straight into assembly — the most expensive place to find them. | E-test (flying probe or fixture) on every board, stated on the PO |
| Impedance verification | Controlled impedance cannot be verified on the board itself — only on coupons. | TDR coupon test with a per-panel impedance report |
| Microsection evidence | Hole copper thickness and internal registration are invisible from the surface. | Cross-section report for the pilot lot, or for every lot on Class 3 builds |
| Warpage limit agreed | Warped boards jam stencil printers and pick-and-place machines at assembly. | Bow & twist limit (e.g. ≤ 0.75% for SMT) stated on the drawing |
| Finish thickness verified | Thin gold, thin tin or degraded OSP cause non-wetting and short shelf life — invisible to the eye. | XRF thickness data available on request for ENIG and other plated finishes |
| Documentation on delivery | Reports close the loop — they are the objective evidence your quality system needs. | CoC, inspection summary and test records shipped with the boards |
Our quality system is documented end to end — see how our quality management works.
Not sure which checks your product actually needs? Tell us the application — we will recommend the class, tests and documentation level that fit, without paying for rigor you do not use.
Discuss Quality RequirementsQuality Library · From Our Engineering Blog
Go Deeper on Standards, Testing & Finishes
These articles expand each part of this guide — IPC standards, in-line inspection and test, and the surface finishes that decide solderability. Part of the PCBELEC fabrication knowledge base.
Avoid These · Three Common Mistakes
Where Acceptance Usually Goes Wrong
Most quality disputes between buyers and fabricators trace back to three assumptions. All three are free to fix — on your purchase order, before production starts.
Mistake 01
Assuming “QC Passed” Means 100% Electrically Tested
“Inspected” can mean anything from full e-test to a visual look at a sample. Boards that pass visual inspection still carry opens and shorts — and those surface only when your assembly line stalls.
Instead: state the test explicitly on the PO: 100% electrical test, flying probe or fixture, against the reference net list. Ask for the e-test record with the shipment.
Mistake 02
Never Stating a Product Class
Without a class, “acceptable” is opinion. The same annular-ring breakout is a pass under one interpretation and a reject under another — and the dispute happens after the boards are built.
Instead: write “IPC-A-600, Class 2” (or Class 3 where the application needs it) into the fabrication notes. One line removes most acceptance ambiguity — see the acceptance checklist above.
Mistake 03
Judging Finish Quality by Appearance
A bright, even ENIG surface can still be too thin, porous, or carrying the nickel corrosion that causes black pad. The defects that kill solderability and shelf life are measured in micrometers — invisible to the eye.
Instead: request XRF thickness data for plated finishes and solderability evidence where shelf life matters. Store boards vacuum-sealed and assemble within the finish’s rated window.
FAQ · Quality & Acceptance Questions
Frequently Asked Questions About Bare Board Quality
Short answers to the questions engineers and buyers ask about standards, testing and acceptance. For anything project-specific, send us your requirements below.
Which IPC standards apply to bare board acceptance?
Two standards work together. IPC-A-600, Acceptability of Printed Boards, defines the visual and dimensional accept/reject criteria — annular rings, conductor condition, solder mask, warpage and more. IPC-6012, the performance specification, defines qualification and conformance requirements such as plating thickness and electrical testing. Both are applied per product class, so the acceptance criteria on your boards depend on the class you specify.
What is the difference between IPC Class 2 and Class 3?
Class 2 covers dedicated-service electronics — products expected to run reliably over an extended life where uninterrupted service is desirable but not critical. Class 3 covers high-reliability products where continued performance is critical and downtime is unacceptable. In practice, Class 3 tightens the criteria: thicker hole copper, stricter annular-ring rules, more inspection evidence — and a higher price to match. Most commercial and industrial products are built to Class 2.
Is every board electrically tested?
At PCBELEC, production boards are 100% electrically tested for opens and shorts against your reference net list. Across the industry this is not universal — some prototype quotes include visual inspection only. Whatever supplier you use, state the e-test requirement explicitly on the purchase order and ask for the test record with the shipment.
What quality documents can I request with my order?
Typical documentation includes: a Certificate of Conformance (CoC), the final inspection summary, electrical test records, TDR impedance reports for controlled-impedance builds, microsection reports showing hole copper and registration, XRF finish thickness data, and material certificates for the laminate. Tell us which documents your quality system requires and we will confirm what is included by default and what is quoted as an option.
How much board warpage is acceptable?
Under IPC-A-600, bow and twist is commonly limited to 0.75% of the diagonal for boards with surface-mount components, and 1.5% for through-hole-only boards. Warpage matters because it jams stencil printing and pick-and-place at assembly. If your assembly process is sensitive, state a tighter limit on the drawing rather than relying on the default.
Can I get inspection data on a prototype order?
Yes. Prototypes ship with the same electrical test and final visual inspection as production builds. Microsection, TDR and XRF reports are available on request — they add a small cost and occasionally a day to the schedule, so mention them when you request the quote rather than after the boards are built.
Quality Requirements · Free Quotation
Discuss Quality & Acceptance Requirements
Tell us the product class, tests and documentation your build needs, and we will quote with those requirements written in — so acceptance on receipt matches what was agreed before production, not negotiated after.
What to Include in Your Inquiry
- Product class required (IPC Class 2 or Class 3)
- Electrical test requirement and any fixture constraints
- Impedance targets, if controlled impedance applies
- Reports needed: microsection, TDR, XRF finish thickness, CoC
- Quantity per build and your target delivery date
New to fabrication files? Check the manufacturing file requirements first.
Need Assembly as Well?
PCBELEC fabricates the bare boards. Turnkey assembly — component sourcing, SMT and through-hole — is handled by our partner JHYPCB. Mention it in your inquiry and we will coordinate both scopes.
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