Skip to main content
Sierra Circuits
Best-in-Class PCB Fabrication, Assembly, & Components.
Industry Leading PCB Designer's Tools.

Speak to an Account Manager Telephone +1 (800) 763-7503

Quote Now

Annular Ring Size Considerations

LEARN PCB
PCB Manufacturing
PCB Assembly
PCB Design and Layout
PCB Basics
Vias, Drilling & Throughplating
Mechanics
Surface
SMD
Quality
SPECIFICATIONS
PCB Fabrication
STANDARDS & POLICY
PCB Ordering
Policy

The minimum annular ring width should be greater than or equal to the values defined in the PCB design.

minimum-annular-ring-width

When an annular ring is less than the specified width, the attachment of the component might be affected. This might lead to a pad breakout that refers to a condition of an annular ring being absent or of zero width. Here, the circuit will enter the pad, minimizing the current-carrying capacity of the circuit.

Given below is a table of annular ring sizes for rigid, flex, and rigid-flex PCBs:

Rigid PCB Standard fab Advanced fab Micro fab
Process pad diameter D +0 .012” (1-mil annular ring) D + 0.008” (Tangency) D +0 .008” (Tangency)
Flex and rigid-flex PCBs Flex Rigid-flex
Process pad diameter D + 0.014″ (1-mil  annular ring) D + 0.014″ (1-mil  annular ring)

Tolerances

When drilling vias, a drill wander of 2 mils is expected. Therefore, the annular ring should not be lesser than 2 mils for microvias/laser drills and 4 mils for mechanically drilled vias.

Note that annular ring measured in the CAM software considers the drilled hole size and not the finished hole size. Plated holes are drilled at a bigger size to accommodate for plating and surface finish.

Teardropped annular ring

Teardropping is used to fix breakout vias and to reinforce connections. When vias breakout at the junction of the conductor and the pad, adding copper around the via can reestablish the broken connection. This will fix the short and ensure the signal can still reach where it needs to go.

teardropped-annular-ring

Teardrop annular rings are critical when dealing with traces thinner than 20 mils. The structural integrity they provide is of great importance in flex boards against shear forces and vibration.

To learn more about annular rings, read annular ring explained by a PCB manufacturer.

» MORE

One-stop PCB assembly services, capabilities, and testing

We source components from chip manufacturers across the globe, including Mouser, Digi-Key, Arrow Electronics and others. We also warehouse a significant inventory of common parts. If we cannot source a specific component, our engineers will make recommendations for fair-price alternatives. Get started now.

Sierra Circuits is headquartered in Silicon Valley.  We welcome visitors at our 70,000 sqft facility,  located at 1108 West Evelyn Avenue in Sunnyvale, California. Book a tour with an account manager today! Let us introduce you to one of the most innovative communities of engineers and designers in the world. We can help you plan your project from design to assembled board.

Manufacturing Equipment at Sierra Circuits

Our 70,000 sqft state-of-the-art campus in the heart of Silicon Valley contains the most advanced equipment required for the manufacture and assembly of your PCBs. Whether you're looking for standard quick turn PCBs or boards with the tightest tolerances, made from exotic metals, there's a reason Sierra Circuits leads the industry in quality and performance.

PCBs manufactured and assembled in the United States

Turn-times as fast as 1 day.

Sierra Circuits can manufacture your PCB and have it expedited to you within 24 hours. Full turnkey boards, with assembly and components in as fast as 5 days. Get an Instant, Itemized Quote

Talk to a Sierra Circuits PCB Expert today

24 hours a day, 7 days a week.

Call us: +1 (800) 763-7503
Email us: through our Customer Care form