Back Drilling PCB Capabilities

iso
ISO 9001/UL Certified
icon assembly
PCB Assembly Specialists
icon truck
97% of PCB Shipped on Time
icon time
98% of PCB Delivered to Spec
icon guarantee
Delivery Guarantee

Why is Back Drill PCB Needed?

PCB Manufacturing Process

online quote
Online Quote
upload pcb
Upload PCB File
order review
Order Review
payment
Payment
order update
Order Updates
truck
Delivery
received
Confirm Received

Factors That Influence the Effectiveness of Back Drilling

Board Material and Thickness

FR4 is the most common material used to build PCBs and it is fairly easy to drill regardless of its thickness. But high-performance circuit boards built using metal (metal cores) and ceramic have some drilling challenges because the materials are relatively tougher than FR4. These materials are more thermally conductive as well, so you’ll need different drilling parameters and bits to get the job done.

Via Size and Spacing

Small vias spaced close to each other require tiny drill bits to conduct more precise drilling, but large vias with more spacing in between give you more leeway. But you’ll need a larger drill bit and possibly do multiple passes to eliminate the unwanted copper and substrate materials. Read more about PCB Via sizes.

Trace and Plane Clearance

While backdrilling, it is important to avoid damaging the board by drilling through the copper power/ground planes and transmission lines. Suppose the clearance between these components and the drill bit is too narrow. In that case, it might be better to avoid backdrilling, use an extremely tiny drill bit with utmost precision, or avoid mechanical drilling. Laser and plasma drilling options are more accurate.

How Much Residual Stub Can Remain After Backdrilling?

sp1
sp2
sp3

sp1
sp2
sp3

When you decide to backdrill your multilayer PCB, you must determine how far you’ll dig in or the stub length you want to remain. Determining this value depends on several factors, but the key one is signal integrity.

The longer the stub length that remains, the higher the signal loss, so the shorter it is, the better. Here’s a breakdown of how to determine the residual stub to leave behind based on the signal loss.

Back Drill Table with
Design Values

Types Value min.
Back drilling Ø 400 μm
Plated-through via Ø 200 μm
Copper clearance 150 μm
Ø-Difference circumference 100 μm
Back drilling depth 200 μm
Distance to connected layer See below
Thickness target layer See below
Thickness stub remainder (safety) See below

Required Target layer
Thickness “G”

F ≤ 1.0 mm 1.0 mm < F ≤ 2.0 mm 2.0 < F ≤ 3.0 mm 3.0 < F ≤ 4.0 mm
G min. 250 μm 300 μm 400 μm 500 μm
H 125 μm 150 μm 200 μm 250 μm
Tolerance ±100 μm ±125 μm ±175 μm ±225 μm

Key
Gmin. = Thickness Target Layer.
H = Distance To Connected Layer.
Tolerance = Thickness Stub Remainder.

sp3
moon shape
wave w

PCB Assembly Services

icon assembly service
Turnkey PCB Assembly

We handle everything from parts sourcing to final assembly, providing a hassle-free experience that ensures top-quality boards every time.

icon production
Prototype & Full Production Runs

Whether you need a few prototypes or large-volume batches, our flexible assembly services adapt to your project’s scope and timeline.

icon leaf
RoHS & Lead-Free Compliance

Stay environmentally responsible with our compliant assembly processes, offering RoHS and lead-free options for safe, reliable builds.

icon gear
Single-Sided, Double-Sided, or Mixed

No matter the complexity, we can assemble boards of all configurations—single-layer, multi-layer, or a mix—to match your exact specifications.

icon layers
Small Quantities & High-Volume Capabilities

From one-off prototypes to bulk orders, we accommodate projects of all sizes without compromising on quality or turnaround time.

icon qa
Trusted by Over 3,000 Customers Worldwide

Join our growing community of satisfied clients who rely on our dependable assembly expertise and dedicated customer support.

Millions of business and innovators use OurPCB

PCB Board Process

Order Received

  • Component Procurement
  • Preparation
  • PCB Manufacture
  • Make Process Flow

Soldering

  • Solder Printing/Wave Soldering
  • SMT/Plugging
  • Inspection (repair if necessary)
  • AOI (repair if necessary)
  • Transfer

Parts Assembly

  • Manual Assembly
  • Cleaning
  • Wire Screw
  • Inspection
  • Repair If Necessary

Finalization

  • Final Confirmation
  • Packing
  • Shiping

Technical Capabilities

wave w
mcd
sp3

Capabilities & Services

Steps for a Back Drill

FAQ's

What does back drilling involve, how much extra does it cost, and why should I consider it?

Back drilling is a secondary machining step performed after the plated-through holes have been created on a PCB, where an additional drill pass removes the unused copper “stub” on the far side. This process typically adds up to 20% more in manufacturing costs. Despite the extra expense, removing the stub delivers noticeable performance benefits: it improves signal integrity by reducing reflections and insertion loss on high-speed traces, lowers electromagnetic interference by eliminating an unintended antenna, and frees up board real estate to support tighter routing and higher layout density. In many high-speed or densely packed designs, these gains in electrical performance and reliability make back drilling a cost-effective choice.

Why is Back drill also called control depth drilling?

It is because a back drill requires specific calculations. Hence, it achieves the depth necessary for accurate results during the drill.

How much should the dielectric thickness design be?

The ideal dielectric thickness design is at least 0.2mm.

Most Effective Alternatives To Back Drilling

The most effective alternatives are buried and blind vias, where the buried via interconnects the board’s internal layers without being exposed to the outside.

What’s the difference between back drilling and blind vias

Blind vias connect an outer layer to one or more inner layers without going all the way through the board. Back drilling starts with a plated-through via and then removes the unwanted copper “stub” on the far side.

Advantages of blind vias over back-drilled holes

  • Signal integrity & EMI
    • No residual copper stub → fewer reflections, lower signal loss and reduced electromagnetic interference.
  • Cost & reliability
    • Eliminates the extra drilling step required for back drilling.
    • Reduces the risk of mechanical damage during manufacturing.
what testing protocols validate performance

Prototype Cable Assemblies

Prototype cable assemblies are the very important place in between PCB design ideas and interconnects. OurPCB brings prototype assemblies with PCB solutions to your tables.

Read More »
what is a multilayer pcb

What is a Multilayer PCB?

ContentsKey TakeawaysWhat is a Multilayer-Printed Circuit Board?How do Multilayer PCB Boards Work?Multilayer PCB ApplicationsMultilayer PCB Manufacturing Process: StepsMultilayer PCB Manufacturing MachinesBenefits of Multilayer Circuit BoardsWhat

Read More »