Quality Tips and Tricks to Help You Get Your PCB Layer Stack Right

| Created: September 28, 2017 | Updated: January 8, 2026

Quality Tips and Tricks To Help You Get Your Layer Stack Right

You know everything possible about signal integrity, EMC, and manufacturing, but the PCB stackup design still seems to come up as a gotcha before PCB manufacturing. PCB stackups are not that complex, and yet even pro designers with plenty of experience might have to make changes before manufacturing. There are multiple reasons for this, such as materials availability, sudden cost changes, or processing constraints with the fab vendor.

Regardless of why a PCB stackup needs to be changed, there are some tips designers can follow which can help prevent changes before going to fabrication. At minimum, the changes might only involve a substitution request based on IPC slash sheets. Keep reading to see these pro tips and understand what questions to ask your fabricator.

Your PCB Stackup is a Critical Manufacturing Platform

If you don't do the PCB stackup right, you won't know you have a problem until it's time to manufacture it. After building many PCBs, I've found that there are several areas relating to stackup design where manufacturers have requested changes:

Material substitutions, either due to cost or availability
Copper weight changes, typically due to the plating thickness versus clearance requirements
Changes to vias in order to satisfy aspect ratio limits
Changes in layer ordering, most commonly when sub-laminations are used
Changes to total thickness at high layer count

Fortunately, there are some easy ways to get around these mistakes and avoid stackup changes before manufacturing.

Send Your PCB Fabrication Company an Email

If your design requires very specific materials and you have an initial stackup in mind, it never hurts to send your PCB fabrication company an email about your proposed materials and stackup. I continue to be surprised by the number of designers that will not do this when they have a stackup materials requirement.

While it helps to have an ideal stackup in mind or even a complete stackup design, this is not required before you talk to a fabricator. For example, if you know that you will need an advanced or less common material in your PCB stackup, you can ask the fabrication house for their lead time, or if they stock a specific material in-house. Even if they don't stock the material, they might offer a suitable alternative that works the same or better in your timeline.

Will a Standard Stackup Work?

PCB fabricators offer standard stackups as a tool for quickly getting a board into production. There are plenty of designs that don't have hard material requirements, only the layer count and the total PCB thickness matter. When this is the case, a standard stackup from the PCB fabricator can be used. This offers two big advantages:

Lower cost, or more predictable cost
Process reliability as standard stackups are heavily qualified
Zero lead time as all the materials are generally kept in stock
Ability to quickly scale to volume with common materials
Some fabricators have a lot of impedance data for their stackups

PCB production assembly

Fabricators often provide material names and datasheets for the materials used in their standard stackups, and this allows designers to take a controlled dielectric approach for impedance-controlled designs. In other words, you can use the dielectric data and create your own transmission line designs without requiring the fabricator’s input. However, standard stackups also admit a controlled impedance approach, where the manufacturer uses their data to verify the impedance values of specific nets in your design.

Learn more about controlled impedance vs. controlled dielectric

Some fabrication companies will also offer standardized advanced stackups, such as flex or rigid-flex, high voltage, RF, and even HDI. Make sure to check with the fabrication vendor to see their service offerings.

Copper Weights, Plating, and Clearances

You might think using heavy copper or multiple lamination/plating cycles makes you a pro designer, but the real skill comes from understanding the DFM constraints that come with heavier copper.

Clearances: Plating with heavier copper requires larger spacing between copper features to allow for copper growth during the plating process. This means that, even though your base PCB stackup materials will start with 0.5 oz. or 1 oz. copper, you will need to allow for larger clearances based on fully plated copper weight.

Through-hole pads and annular rings: Heavier copper can increase drill drift in mechanical drilling as the drill is pushed through the copper pads on each layer. This will require increasing the pad sizes to allow for larger annular rings on plated through-holes.

Via aspect ratio: Mechanically-drilled via aspect ratios can be limited when copper weight is heavier, either due to the usage of higher copper weight or due to multiple copper plating cycles with sub-laminations. This may require increasing the drill diameter in order to accommodate heavier copper.

Manufacturers can provide the clearance requirement for heavier copper. This will typically be some base clearance value plus another factor related to the plated copper thickness. If the clearance requirements are not given on the manufacturer’s website, email the manufacturer for a capabilities statement.

Understand Slash Sheets

A useful tool for understanding PCB material compatibility in stackup fabrication is an IPC slash sheet. The slash sheet number for a material identifies its compatibility with other commercially-available materials. It is therefore common in PCB stackups that do not have a dielectric constant or impedance requirement to specify a slash sheet for the core/prepreg materials in the PCB fabrication notes.

For example, take a look at the slash sheet for FR408HR from Isola. I have circled the IPC-4101 slash sheet numbers in blue. To learn more about slash sheets and to see a table listing compatibility across different slash sheet entries, read this article.

Slash sheets do not perfectly align to specific capabilities or material properties, but they do align with processing. If you specify a slash sheet for a material, but you need to have some other specification met by the materials (for example, high-voltage reliability), then you should specify this in the fabrication notes or select a commercial material that meets the specifications.

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About Author

Zachariah Peterson has an extensive technical background in academia and industry. He currently provides research, design, and marketing services to companies in the electronics industry. Prior to working in the PCB industry, he taught at Portland State University and conducted research on random laser theory, materials, and stability. His background in scientific research spans topics in nanoparticle lasers, electronic and optoelectronic semiconductor devices, environmental sensors, and stochastics. His work has been published in over a dozen peer-reviewed journals and conference proceedings, and he has written 2500+ technical articles on PCB design for a number of companies. He is a member of IEEE Photonics Society, IEEE Electronics Packaging Society, American Physical Society, and the Printed Circuit Engineering Association (PCEA). He previously served as a voting member on the INCITS Quantum Computing Technical Advisory Committee working on technical standards for quantum electronics, and he currently serves on the IEEE P3186 Working Group focused on Port Interface Representing Photonic Signals Using SPICE-class Circuit Simulators.