Free Tool

PCB Stackup Builder

Design and visualize your PCB layer stackup. Build custom configurations for flex, rigid-flex, and multilayer boards.

Quick Presets

Layers

Coverlay
mm
Adhesive
mm
Copper
mm
Polyimide
mm
Copper
mm
Adhesive
mm
Coverlay
mm

Stackup Preview

0.195mmCoverlay (Top)0.025mmAdhesive0.025mmCopper (L1)0.035mmPolyimide Core0.025mmCopper (L2)0.035mmAdhesive0.025mmCoverlay (Bottom)0.025mm

Stackup Summary

Total Thickness0.195 mm
Layer Count2L (7 total)

Thickness Breakdown

Coverlay0.050 mm
Adhesive0.050 mm
Copper0.070 mm
Polyimide0.025 mm

Design Tips

  • Use RA (rolled annealed) copper for dynamic flex applications to improve bend life
  • Place neutral bend axis in the center of the flex section for balanced stress distribution
  • Minimize adhesive layers in flex areas - adhesiveless constructions offer better flexibility
  • Consider asymmetric stackups carefully as they can cause warping

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Frequently Asked Questions

What is a PCB stackup?
A PCB stackup is the arrangement of copper layers and insulating layers that make up a PCB. It defines the layer count, materials used, and thickness of each layer. Proper stackup design is critical for signal integrity, impedance control, and mechanical reliability.
What materials are used in flex PCB stackups?
Flex PCBs typically use: 1) Polyimide (PI) as the flexible base material, 2) Rolled annealed (RA) or electrodeposited (ED) copper for conductors, 3) Adhesive for bonding layers, 4) Coverlay (polyimide + adhesive film) for protection. Rigid-flex boards also include FR4 and prepreg in the rigid sections.
How do I choose the right layer count?
Layer count depends on: 1) Routing complexity and signal count, 2) Power and ground plane requirements, 3) Impedance control needs, 4) Board size constraints. Start with the minimum layers needed, as more layers increase cost and thickness, which can impact flexibility.
What is the difference between coverlay and solder mask?
Coverlay is a polyimide film with adhesive, applied as a sheet and patterned via laser or mechanical drilling. It's more flexible and durable for flex applications. Solder mask is a liquid coating (LPI) that's screen printed or sprayed. Solder mask cracks when flexed, so coverlay is required for flex areas.
How does stackup affect impedance?
Stackup directly affects impedance through: 1) Dielectric thickness (H) - thicker = higher impedance, 2) Dielectric constant (εr) - higher = lower impedance, 3) Copper thickness (T) - affects trace width for target impedance. Consistent layer-to-layer spacing is critical for controlled impedance designs.

Definition And Context

A PCB stackup is the ordered build of copper, dielectric, adhesive, coverlay, and support materials that defines how a circuit is manufactured. In flex and rigid-flex work, the stackup also controls bend behavior, total thickness, and how the finished part can be assembled into the product.

This page was reviewed for GEO clarity by Hommer Zhao of WIRINGO so the content explains the underlying engineering terms, not only the interface or headline claim.

Why Stackup Planning Comes Early

Stackup decisions lock in several downstream choices at once. Trace width targets, bend performance, connector interface height, and stiffener thickness all depend on the structure chosen at the start. A team that treats stackup as a late documentation step usually discovers mechanical or electrical conflicts after the layout is already expensive to change.

A builder page makes those tradeoffs easier to discuss because it turns an abstract layer list into something visible. Even when the first draft is not final, it helps engineers agree on what must stay fixed and what can still be negotiated with the supplier.

What Still Needs Fabricator Review

Material names in a planning tool are not the same thing as qualified production materials. Adhesive systems, copper foil types, and coverlay options differ by supplier, and those differences can shift thickness, impedance, and flex life. After the concept stack is chosen, the fabricator should confirm the exact materials that will be used to hit the target.

That review is also where manufacturability details show up. Registration capability, lamination flow, drill strategy, and selective stiffener placement are process questions that a generic planning tool cannot finalize on its own.

Layer Elements And Their Purpose

Layer ElementPrimary RoleTypical Review Point
CopperCarries power and signalsCurrent, impedance, flex fatigue
Polyimide coreProvides flexible dielectric supportThickness and mechanical durability
Adhesive or bondplyBonds layers togetherFlow, thickness control, reliability
CoverlayProtects traces in flex areasOpenings, stiffness, bend entry
StiffenerAdds local supportConnector zones and assembly fit

Authoritative References

The external references below are included as basic background reading for common manufacturing and interconnect terms used on this page.

  • IPC

    https://en.wikipedia.org/wiki/IPC_(electronics)

  • ISO 9001

    https://en.wikipedia.org/wiki/ISO_9001

  • Crimp joining

    https://en.wikipedia.org/wiki/Crimp_(joining)