When customers request a “2OZ copper thickness” for their PCBs, it seems like a straightforward specification. After all, 2OZ copper equates to 70μm in theory. But here’s where it gets tricky—once the PCB Manufacturer is manufactured and cross-sectioned, the measured copper thickness often shows just around 60μm, sometimes even lower. This discrepancy frequently causes misunderstandings and disputes between customers and suppliers.

So, what’s the real story behind 2OZ copper thickness? And what does IPC actually say?

Let’s break it down.

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1. The Common Dispute: 2OZ Copper Thickness Requested, 60μm Measured

Many buyers expect the finished PCB to have a uniform 70μm copper thickness when they order 2OZ. But in reality, the final product may come in at 60μm or slightly less after processing—especially when plated copper is involved.

Does that mean the board is out of spec? Not necessarily. It depends on the IPC-6012 standard.

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2. IPC-6012 Defines Inner Layer Copper Requirements Clearly

According to IPC-6012 Section 3.6.2.13, the minimum required thickness for 2OZ copper on the inner layers is:

              55.7μm minimum after processing

              Rework is allowed once, with a maximum loss of 6μm

Therefore, the absolute minimum thickness for an acceptable inner layer is 49.7μm—far below 70μm.

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3. Outer Layer Copper? That’s Where It Gets Vague

While IPC is clear about inner layers, its guidance on outer layer copper thickness is much less specific. Here’s what the standard outlines:

3.1 Starting from 1OZ base copper:

                Minimum final copper thickness:

                    Class 1 & 2: 47.9μm

                    Class 3: 52.9μm

               With rework (max 6μm loss):

                   Class 1 & 2: ≥ 41.9μm

                   Class 3: ≥ 46.9μm

3.2 Starting from 2OZ base copper:

                Minimum final copper thickness:

                   Class 1 & 2: 78.7μm

                   Class 3: 83.7μm

              With rework:

                   Class 1 & 2: ≥ 71.7μm

                  Class 3: ≥ 77.7μm

3.3 The reality in production:

For most 2OZ outer layer requirements, factories plate from a 1OZ base copper

This means the finished copper rarely reaches 70μm

Still, IPC Class 2 accepts 47.9μm or even 41.9μm depending on the process

3.4 No IPC definition for 1.5OZ copper

Another nuance: IPC doesn’t define a minimum thickness for 1.5OZ copper, so interpretation is up to the manufacturer and client agreement.

3.5 Cost impact of starting with 2OZ base copper

The cost delta is significant—choosing 2OZ base copper for double-sided PCBs can increase the board cost by around 25% compared to using 1OZ.

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4. The Supplier’s Dilemma: Win Orders or Ensure No Dispute?

Here’s the catch…

Quoting based on 1OZ base copper offers a price advantage, helping win the order, but risks post-delivery disputes

Quoting based on 2OZ base copper avoids any quality debate, but raises costs, making the supplier less competitive

In a highly competitive market, this puts PCB manufacturers in a tough spot.

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5. Why Not Just Make It Thicker or Choose Positive Tolerance Foils?

That sounds ideal, but it’s not that easy:

5.1 Standardized copper foil and base material market

                Copper foil and laminates are standard commodities

                Standard specs are readily available and affordable

5.2 Copper, CCL and PCB Manufacturers prefer negative-tolerance copper foil

 To maximize surface yield and reduce cost, copper foil vendors favor the lower bound of the tolerance range

5.3 Positive-tolerance copper foil is rare and custom

              To get copper that’s consistently thicker than spec, a special order is required

              But here’s the kicker—it comes with:

                  1-ton minimum order

                  7–15 days for foil production

                  3–7 days for laminate processing

                  7–10 days for PCB fabrication

                   Total lead time: 25+ days

Not ideal for fast-moving projects or price-sensitive markets.

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6. It’s Not Cutting Corners. It’s the IPC Standard at Work.

When PCB manufacturers choose 1OZ base copper + plating to meet 2OZ outer layer requirements, it’s not about “cutting corners.” It’s about working within IPC’s framework and balancing cost, lead time, and yield.

Unfortunately, not all procurement professionals are fully aware of these IPC nuances—leading to misplaced blame on suppliers.

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7. SQPCB’s Transparent Approach

At SQPCB, we’ve also faced customer concerns around copper thickness. That’s why we take a proactive approach:

All orders with 2OZ copper requirements come with clear, upfront communication

                We help clients decide whether they want:

                    Lower cost with IPC-compliant plating

                    Or guaranteed 2OZ base copper with higher costs

By explaining both technical and cost implications, we ensure our customers make the right choice—based on design needs, thermal/load requirements, and budget.

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Final Thoughts

2OZ copper thickness is more than just a number. It involves IPC interpretation, real-world manufacturing constraints, procurement expectations, and supplier strategy. Misunderstandings are common, but with proper communication and an understanding of the standards, they can be avoided.

If you need guidance on copper thickness selection or PCB stack-up design, SQPCB’s engineering team is here to help. Let’s work together to find a balance between performance, compliance, and cost-efficiency.

Frequently Asked Questions (FAQs)

1. Why is 2OZ copper thickness often measured below 70μm in finished PCBs?
Because PCB copper thickness includes multiple processing steps—etching, plating, and potential rework—some material is naturally lost. IPC-6012 allows for this and defines acceptable post-processing minimums (e.g., ≥49.7μm for 2OZ inner layers), which are often misunderstood.

2. Is using 1OZ base copper with plating considered non-compliant for 2OZ outer layer requests?
Not necessarily. If the final copper thickness meets IPC’s defined minimums for 1OZ base copper + plating (e.g., ≥47.9μm for Class 2), it is still compliant. However, clear communication is essential to align expectations.

3. What is the risk of using 2OZ base copper vs. 1OZ base copper?
2OZ base copper ensures no thickness disputes, but adds 20–25% to board cost and increases lead time. 1OZ base copper with plating is more economical but may raise concerns if buyers expect to see 70μm exactly.

4. Does IPC-6012 define tolerance for 1.5OZ copper foil?
No, IPC does not provide a specific standard or minimum copper thickness for 1.5OZ. Manufacturers and customers must agree on the acceptance criteria for such non-standard copper weights.

5. How can I ensure my 2OZ copper PCB is truly compliant?
Work with a supplier like SQPCB who clearly explains the base copper used, plating process, and IPC compliance criteria. Request cross-section samples and technical confirmation upfront to avoid confusion.