2.8mm PCB Thickness: When Standard Options Don’t Fit Your Design

Sometimes the standard options just don’t work. I’ve been in this situation more times than I can count—you’ve got a design that demands something between 2.4mm and 3.2mm, and neither of those stock thicknesses will do. That’s when you start looking at custom specifications, and 2.8mm PCB thickness becomes a serious consideration.

Most engineers default to standard thicknesses because they’re readily available, cost-effective, and well-documented. But real-world projects don’t always fit into neat categories. When your enclosure has precisely 3.1mm of clearance, or your multilayer stack-up calculations land you at 2.75mm, you’re faced with a choice: compromise your design or go custom. This guide is for engineers who’ve decided that compromise isn’t acceptable.

In my experience, the decision to specify a 2.8mm PCB usually comes from one of two scenarios: either the mechanical constraints of your system demand it, or your electrical stack-up requirements land you there naturally. Either way, understanding how to successfully execute a custom thickness design can save your project from costly redesigns.

Understanding Non-Standard PCB Thickness

Before diving into the specifics of 2.8mm boards, let’s establish what “non-standard” actually means in PCB manufacturing.

What Makes 2.8mm PCB a Custom Thickness?

The PCB industry has settled on a set of commonly manufactured thicknesses based on historical precedent and manufacturing efficiency. These standard options include 0.8mm, 1.0mm, 1.2mm, 1.6mm, 2.0mm, 2.4mm, and 3.2mm. Notice that 2.8mm isn’t on this list—it falls in the gap between 2.4mm and 3.2mm, making it a custom specification.

When you request a 2.8mm PCB from your fabricator, they can’t simply pull pre-made laminate off the shelf. Instead, they must combine specific core materials and prepreg layers to achieve your target thickness. This isn’t necessarily difficult, but it does require planning and adds variables to the manufacturing process.

Standard vs. Custom Thickness Comparison

The 2.8mm thickness sits in an interesting position. It’s thick enough to provide substantial mechanical benefits over 2.4mm, but not so extreme that it creates major manufacturing challenges. For many applications, it represents an optimal middle ground.

When to Specify 2.8mm PCB Thickness

The decision to go custom should be driven by genuine technical requirements, not arbitrary preferences. Here are the scenarios where 2.8mm PCB thickness makes engineering sense.

Mechanical Fit Requirements

The most common reason I’ve specified 2.8mm boards is simple: they fit where standard thicknesses don’t. Consider these real-world scenarios:

Retrofit designs where you’re replacing an existing board in legacy equipment. The original designer used a thickness that’s no longer common, and your replacement must match exactly for connector alignment and mounting hole registration.

Card cage systems with fixed slot dimensions. Many industrial card cages were designed around specific board thicknesses, and deviation by even 0.4mm can cause insertion problems or inadequate card retention.

Multi-board assemblies where stack height is critical. When you’re sandwiching boards with specific standoff heights, the cumulative tolerance of each board thickness matters.

Multilayer Stack-Up Optimization

Sometimes the 2.8mm thickness emerges naturally from your electrical requirements rather than mechanical constraints. This happens when:

Your controlled impedance calculations require specific dielectric thicknesses between signal and reference layers. After specifying the dielectrics needed for your target impedance values, the total stack-up lands at 2.8mm.

You need a particular number of routing layers with adequate copper weights, and the combination of cores and prepregs that achieves your electrical goals totals 2.8mm.

Your design requires specific layer spacing for EMI control or crosstalk management, and those spacings sum to a non-standard total.

Heavy Copper with Moderate Thickness

The 2.8mm PCB thickness enables some interesting heavy copper configurations that wouldn’t work well on thinner boards. You can achieve 3oz or 4oz copper on multiple layers while maintaining reasonable aspect ratios for vias—something that becomes problematic if you try to cram heavy copper into a standard 2.4mm board.

The 2.8mm thickness provides adequate substrate material to buffer the thermal stress from heavy copper without the weight and cost penalty of jumping to 3.2mm.

Designing Your 2.8mm PCB Stack-Up

Creating a successful 2.8mm PCB starts with a well-planned stack-up. Since you’re working outside standard configurations, you’ll need to be more hands-on with material selection.

Sample 4-Layer 2.8mm Stack-Up

Sample 6-Layer 2.8mm Stack-Up

The key to achieving 2.8mm is combining available core and prepreg thicknesses creatively. Work with your fabricator early—they’ll know exactly which materials they stock and can suggest combinations that hit your target.

Manufacturing Considerations for 2.8mm PCB

Going custom means paying closer attention to manufacturing factors that you might overlook with standard boards.

Aspect Ratio and Via Design

For a 2.8mm board, maintaining good via aspect ratios requires attention. Most manufacturers prefer aspect ratios of 10:1 or better for reliable plating. This means minimum via diameters of 0.28mm (about 11 mils) for through-hole vias.

If your design requires finer vias, discuss blind or buried via options with your manufacturer. These don’t traverse the full board thickness, enabling smaller diameters without aspect ratio concerns.

Material Availability and Lead Time

Not every prepreg and core combination exists in every thickness. When you specify 2.8mm PCB thickness, your fabricator may need to:

• Order specific laminate materials that aren’t in regular stock
• Combine unusual prepreg configurations to hit the target
• Allow extra time for material procurement

Plan for an additional 3-7 days of lead time compared to standard thickness orders. For prototype quantities, this might stretch longer if materials must be cut from larger sheets specifically for your order.

Tolerance Considerations

Custom thickness boards often have slightly wider tolerances than standard options. While a 1.6mm board might hold ±0.1mm easily, a 2.8mm PCB might specify ±0.15mm or even ±0.2mm depending on the specific stack-up.

If your application requires tighter thickness control, discuss this with your manufacturer before finalizing the design. Tighter tolerances may require specific material selections or additional process controls.

Read more Different PCB Thickness:

0.1mm PCB: The Complete Guide to Ultra-Thin Circuit Boards

0.2mm PCB: Complete Guide to Thin Circuit Board Design & Manufacturing

0.4mm PCB: The Starting Point for Multilayer Circuit Board Design

0.6mm PCB: The First Thickness Supporting All Surface Finishes

0.8mm PCB: Complete Guide to Half-Thickness Board Design & Applications

1.2mm PCB Thickness Guide: Perfect Balance Between Flexibility & Durability

1.5mm PCB: The Often Overlooked Standard Thickness Explained

1.6mm PCB: Why It Became the Industry Standard & Complete Design Guide

1.8mm PCB: The Non-Standard Thickness for Multilayer Board Design

2.0mm PCB: The Heavy-Duty Thickness for Industrial & High-Power Applications

2.4mm PCB: The Ultimate Thick Board Guide for High-Power & Extreme Applications

2.8mm PCB Thickness: When Standard Options Don’t Fit Your Design

3.0mm PCB: Complete Guide for Heavy-Duty Boards Without the 3.2mm Overkill

4.2mm PCB: Custom Backplane Thickness for When 4.0mm Falls Short

4.8mm PCB: Heavy-Duty Backplane Thickness When You Need Nearly 5.0mm Performance

5.6mm PCB: The Ultra-Thick Sweet Spot Between 5.0mm and 6.0mm Backplanes

Cost Analysis: Is 2.8mm PCB Worth It?

Custom thickness adds cost—there’s no way around that. The question is whether the benefits justify the premium.

Cost Factors for Custom Thickness

Material costs: Non-standard combinations may require purchasing materials in smaller quantities at higher unit prices.

Setup time: The fabricator must calculate and verify the custom stack-up, potentially running test panels.

Yield risk: Less-characterized processes carry slightly higher scrap risk, which gets priced into the quote.

Minimum orders: Some fabricators have higher minimums for custom work to justify the setup investment.

When Custom Thickness Pays Off

Despite the premium, 2.8mm PCB specifications often make economic sense when:

• Redesigning to standard thickness would require expensive mechanical changes elsewhere in the system
• The alternative is multiple design iterations to fit standard thickness constraints
• Field reliability improvements from optimal thickness reduce warranty costs
• The board is destined for high-reliability applications where performance outweighs material cost

I’ve seen projects where engineers spent weeks trying to force a design into 2.4mm thickness when a 2.8mm custom board would have solved all their problems for an extra $50 per prototype run. Sometimes the “expensive” option is actually cheaper when you account for engineering time.

Working with Manufacturers on Custom Thickness

Successful custom thickness projects require closer collaboration with your fabricator than standard orders.

Early Engagement is Critical

Don’t wait until your design is complete to discuss thickness with your manufacturer. Reach out early with your requirements:

• Target thickness and acceptable tolerance range
• Layer count and copper weight requirements
• Any impedance control needs
• Expected production volumes

This conversation often reveals options you hadn’t considered. Your fabricator might have a semi-standard 2.8mm stack-up they’ve used before, or they might suggest a 2.75mm or 2.85mm alternative that uses more readily available materials.

Documentation Requirements

Custom boards require more explicit documentation than standard orders. Include:

• Detailed stack-up drawing with all layer thicknesses
• Material callouts (specific FR-4 grade, prepreg types)
• Thickness tolerance requirements
• Any special processing notes

Don’t rely on the fabricator to interpret your intent—spell everything out clearly.

Useful Resources for Custom PCB Design

Design Tools and Calculators

• Saturn PCB Design Toolkit – Includes stack-up planning tools and impedance calculators (free download at saturnpcb.com)
• Polar Instruments Speedstack – Professional stack-up planning with manufacturer material libraries
• Altium Designer Stack-up Manager – Integrated stack-up design with impedance modeling

Industry Standards

• IPC-4101 – Specification for Base Materials for Rigid and Multilayer Printed Boards
• IPC-6012 – Qualification and Performance Specification for Rigid Printed Boards
• IPC-2221 – Generic Standard on Printed Board Design

Manufacturer Resources

Most fabricators publish design guidelines and standard stack-up options on their websites. Request custom stack-up capabilities directly—this information often isn’t published but is readily available to serious customers.

Common Applications for 2.8mm PCB

Based on my project experience, here are the applications where I most frequently see 2.8mm PCB specifications:

Industrial Control and Automation

Process controllers, PLCs, and industrial I/O modules often end up at 2.8mm due to the combination of heavy connectors, power handling requirements, and rigid card cage mounting systems inherited from earlier equipment generations.

Test and Measurement Equipment

Instrumentation often has specific board thickness requirements driven by RF shielding enclosure designs or precision connector mounting. The 2.8mm thickness frequently appears in high-precision analog front ends where mechanical stability affects measurement accuracy.

Telecom and Networking Equipment

Line cards and switch modules in established chassis designs sometimes require 2.8mm boards. These systems were often designed with specific slot dimensions that don’t accommodate standard modern thicknesses.

Custom Power Electronics

Medium-power converters and inverters benefit from the 2.8mm thickness when they need heavy copper but aren’t pushing into the extreme-thickness territory that would require 3.2mm boards.

Frequently Asked Questions About 2.8mm PCB

Why would I choose 2.8mm instead of rounding to 3.0mm or 3.2mm?

The primary reasons are mechanical fit, weight, and cost. If your enclosure or mounting system requires 2.8mm, rounding up to 3.2mm creates interference problems. Additionally, the extra 0.4mm of material adds weight—significant in mobile or aerospace applications—and increases material cost by 10-15%. When your design naturally lands at 2.8mm from stack-up calculations, there’s no engineering benefit to adding unnecessary thickness.

How much longer is the lead time for 2.8mm PCB compared to standard thickness?

Expect 3-7 additional days for prototype quantities due to material procurement and stack-up verification. For production quantities, the lead time impact diminishes once the fabricator has validated the process and stocked appropriate materials. Some fabricators may be able to expedite if they happen to have suitable materials in stock from previous custom orders. Always confirm lead time before committing to a 2.8mm PCB specification in a time-sensitive project.

Can all PCB manufacturers produce 2.8mm thickness boards?

Most capable fabricators can produce 2.8mm boards, but not all will accept the order. Some high-volume manufacturers focused on standard products may decline custom thickness work as it disrupts their optimized processes. Mid-tier fabricators specializing in prototype and low-volume production are often better equipped for custom specifications. Always confirm capability before starting your design, and be prepared to provide detailed stack-up specifications rather than expecting the manufacturer to figure it out.

What’s the typical tolerance for 2.8mm PCB thickness?

Standard tolerance for 2.8mm PCB is typically ±10%, meaning acceptable finished thickness ranges from 2.52mm to 3.08mm. Tighter tolerances of ±0.15mm or better are achievable with specific material selections and process controls, but expect additional cost. For applications where thickness variation is critical—such as card-edge connector fit—specify your tolerance requirement explicitly and confirm the fabricator can meet it before placing the order.

Is 2.8mm thick enough for heavy copper designs?

Yes, 2.8mm provides excellent support for heavy copper configurations up to 4oz on outer layers and 3oz on inner layers. The additional thickness compared to 2.4mm boards helps accommodate the mechanical stress from CTE mismatch between copper and FR-4 during thermal cycling. For extremely heavy copper (6oz and above), consider whether 3.2mm might provide better long-term reliability, but for most heavy copper power applications, the 2.8mm PCB thickness is a solid choice.

Making the Custom Thickness Decision

Specifying a 2.8mm PCB is a deliberate choice that should be driven by concrete technical requirements. The extra cost and lead time are worthwhile when standard thicknesses genuinely don’t meet your needs—whether due to mechanical constraints, stack-up optimization, or heavy copper requirements.

The key to success with custom thickness boards is early engagement with your fabricator, explicit documentation of your requirements, and realistic expectations about tolerance and lead time. When you approach it thoughtfully, custom thickness opens up design possibilities that simply aren’t available with off-the-shelf options.

If you’re sitting on the fence between forcing your design into 2.4mm or 3.2mm versus going custom at 2.8mm, consider the total project cost including engineering time and potential redesigns. Often, the custom board pays for itself by eliminating compromise elsewhere in your system.

Not every design needs custom thickness—but when yours does, understanding how to execute it successfully can be the difference between a problematic build and a smooth production run.