{"id":4262,"date":"2026-06-23T10:18:30","date_gmt":"2026-06-23T10:18:30","guid":{"rendered":"https:\/\/blogs.lcsc.com\/blog\/?p=4262"},"modified":"2026-06-23T10:18:30","modified_gmt":"2026-06-23T10:18:30","slug":"pcb-annular-ring-guide","status":"publish","type":"post","link":"https:\/\/blogs.lcsc.com\/blog\/pcb-annular-ring-guide\/","title":{"rendered":"PCB Annular Ring Guide: Sizing Rules &#038; IPC Standards"},"content":{"rendered":"<h2><b><span data-font-family=\"Arial\">\u00a0Key Takeaways<\/span><\/b><\/h2>\n<ul>\n<li><span data-font-family=\"Arial\">Annular ring = copper pad area surrounding a drilled or laser-machined <a href=\"https:\/\/www.lcsc.com\/pcba\">PCB<\/a> hole.<\/span><\/li>\n<li><span data-font-family=\"Arial\">Width = (Pad Diameter \u2013 Finished Hole Diameter) \/ 2; ranges from 1 mil (HDI microvias) to 8+ mil (standard).<\/span><\/li>\n<li><span data-font-family=\"Arial\">IPC Class 3 requires \u22652 mil on external layers and \u22651 mil on internal layers; zero breakout or tangency.<\/span><\/li>\n<li><span data-font-family=\"Arial\">Teardrop pads are mandatory for Class 3 and recommended for traces narrower than 20 mil.<\/span><\/li>\n<li><span data-font-family=\"Arial\">HDI microvias (IPC-2226 Level B) allow 1 mil minimum rings thanks to laser-drill accuracy of \u00b10.5 mil.<\/span><\/li>\n<\/ul>\n<h2><b><span data-font-family=\"Arial\">Product Entity Definition<\/span><\/b><\/h2>\n<p><span data-font-family=\"Arial\">The PCB annular ring \u2014 sometimes referred to as the &#8220;ring&#8221; or &#8220;land ring&#8221; \u2014 is the copper area that remains around a drilled or laser-machined hole on each layer of a printed circuit board. More precisely, it is the copper donut-shaped region between the outer edge of the finished hole wall and the outer boundary of the copper pad. When viewed from above, plated vias display this ring pattern clearly, which is the origin of the term &#8220;annular&#8221; (from the Latin annulus, meaning ring).<\/span><\/p>\n<p><span data-font-family=\"Arial\">Annular rings are present on both through-hole vias and component plated through-holes (PTHs), spanning all layers the hole passes through. The width of an annular ring is calculated as half the difference between the pad diameter and the finished hole diameter: Annular Ring Width = (Pad Diameter \u2013 Finished Hole Diameter) \/ 2. Typical widths range from 0.05 mm (2 mil) for high-density HDI boards to 0.2 mm (8 mil) or more for standard commercial designs, depending on the IPC product class and the manufacturing capability of the fabricator.<\/span><\/p>\n<p><span data-font-family=\"Arial\">These structures are governed primarily by IPC-2221 (Generic Standard on Printed Board Design), IPC-6012 (Qualification and Performance Specification for Rigid Printed Boards), and IPC-2226 (Design Standard for High Density Interconnect), and they appear in virtually every PCB manufactured for consumer electronics, industrial automation, medical devices, aerospace systems, and telecommunications infrastructure.<\/span><\/p>\n<h2><b><span data-font-family=\"Arial\">Product Overview<\/span><\/b><\/h2>\n<p><span data-font-family=\"Arial\">The annular ring serves two critical functions simultaneously: it provides the electrical interface between a copper trace on a given layer and the conductive barrel of the via, and it provides the mechanical anchor that keeps the plated barrel bonded to the board substrate under thermal cycling, vibration, and assembly stresses. Without a sufficient annular ring, a drill hit that wanders even a few mils from the center of the pad can sever the trace-to-via connection entirely \u2014 a condition known as breakout \u2014 resulting in an open circuit that may not be detected until final electrical test or, worse, field failure.<\/span><\/p>\n<p><span data-font-family=\"Arial\">Beyond simple connectivity, the annular ring width directly affects yield and cost. Tighter rings require higher precision equipment, slower throughput, and more stringent inspection \u2014 all of which translate into higher per-board cost and potentially lower first-pass yield. Conversely, excessively large pads consume routing space on dense boards, making it harder to escape BGA patterns and route tight signal layers. The designer&#8217;s task is to choose the minimum annular ring that satisfies the target IPC product class while giving the fabricator just enough process margin to achieve consistently high yield.<\/span><\/p>\n<p><span data-font-family=\"Arial\">Compliance with IPC class requirements is not optional in regulated industries. Class 3 boards used in aerospace, military, and medical applications legally require a minimum annular ring of 2 mil on external layers and 1 mil on internal layers, with zero tolerance for breakout or tangency. Failing to meet these requirements results in board rejection, costly rework, and in some cases, full lot scrapping \u2014 making correct annular ring design one of the highest-ROI decisions in the <a href=\"https:\/\/blogs.lcsc.com\/blog\/backplane-pcb-design\/\">PCB<\/a> layout stage.<\/span><\/p>\n<h2><b><span data-font-family=\"Arial\">PCB Annular Ring Key Features and Advantages<\/span><\/b><\/h2>\n<table>\n<tbody>\n<tr>\n<td colspan=\"1\" rowspan=\"1\" width=\"173.33333333333334\"><b><span data-font-family=\"Arial\">Feature<\/span><\/b><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"258.6666666666667\"><b><span data-font-family=\"Arial\">Description<\/span><\/b><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"192\"><b><span data-font-family=\"Arial\">Benefit<\/span><\/b><\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\" width=\"173.33333333333334\"><span data-font-family=\"Arial\">Electrical Continuity<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"258.6666666666667\"><span data-font-family=\"Arial\">Copper ring bridges trace and via barrel across every layer<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"192\"><span data-font-family=\"Arial\">Ensures signal and power integrity in multi-layer stackups<\/span><\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\" width=\"173.33333333333334\"><span data-font-family=\"Arial\">Drill Wander Compensation<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"258.6666666666667\"><span data-font-family=\"Arial\">Extra copper margin absorbs CNC positional tolerance of \u00b12\u20133 mil<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"192\"><span data-font-family=\"Arial\">Prevents open circuits from off-center drill hits<\/span><\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\" width=\"173.33333333333334\"><span data-font-family=\"Arial\">Teardrop Reinforcement<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"258.6666666666667\"><span data-font-family=\"Arial\">Additional copper fillet at trace-to-pad junction<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"192\"><span data-font-family=\"Arial\">Prevents trace severance under thermal cycling and mechanical stress<\/span><\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\" width=\"173.33333333333334\"><span data-font-family=\"Arial\">IPC Class Scalability<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"258.6666666666667\"><span data-font-family=\"Arial\">Ring sizing adapts to Class 1 \/ 2 \/ 3 requirements<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"192\"><span data-font-family=\"Arial\">Matches board reliability tier without over-engineering standard products<\/span><\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\" width=\"173.33333333333334\"><span data-font-family=\"Arial\">DFM Integration<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"258.6666666666667\"><span data-font-family=\"Arial\">Minimum ring rules enforced by EDA DRC checks (Altium, Cadence, KiCad)<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"192\"><span data-font-family=\"Arial\">Catches violations before Gerbers are submitted to fab<\/span><\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\" width=\"173.33333333333334\"><span data-font-family=\"Arial\">Layer-Specific Measurement<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"258.6666666666667\"><span data-font-family=\"Arial\">External rings from finished hole wall; internal rings from drilled hole wall<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"192\"><span data-font-family=\"Arial\">Accounts for copper plating thickness (0.8\u20131 mil) for accurate IPC compliance<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h2><b><span data-font-family=\"Arial\">Technical Specifications<\/span><\/b><\/h2>\n<table>\n<tbody>\n<tr>\n<td colspan=\"1\" rowspan=\"1\" width=\"312\"><b><span data-font-family=\"Arial\">Parameter<\/span><\/b><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"312\"><b><span data-font-family=\"Arial\">Value \/ Range<\/span><\/b><\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\" width=\"312\"><span data-font-family=\"Arial\">Annular Ring Width Formula<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"312\"><span data-font-family=\"Arial\">(Pad Diameter \u2013 Finished Hole Diameter) \/ 2<\/span><\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\" width=\"312\"><span data-font-family=\"Arial\">IPC Class 1 Minimum (External)<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"312\"><span data-font-family=\"Arial\">\u2248 plating thickness (~0.8 mil); breakout permitted<\/span><\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\" width=\"312\"><span data-font-family=\"Arial\">IPC Class 2 Minimum (External)<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"312\"><span data-font-family=\"Arial\">0 mil (tangency acceptable); 90\u00b0 breakout allowed<\/span><\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\" width=\"312\"><span data-font-family=\"Arial\">IPC Class 3 Minimum (External)<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"312\"><span data-font-family=\"Arial\">2 mil (0.05 mm); zero breakout, zero tangency<\/span><\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\" width=\"312\"><span data-font-family=\"Arial\">IPC Class 3 Minimum (Internal)<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"312\"><span data-font-family=\"Arial\">1 mil (0.025 mm); zero breakout<\/span><\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\" width=\"312\"><span data-font-family=\"Arial\">HDI Microvia (IPC-2226 Level B)<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"312\"><span data-font-family=\"Arial\">0.025 mm (1 mil) minimum<\/span><\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\" width=\"312\"><span data-font-family=\"Arial\">Standard Mechanical Drill Min.<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"312\"><span data-font-family=\"Arial\">4\u20136 mil (0.10\u20130.15 mm) industry typical<\/span><\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\" width=\"312\"><span data-font-family=\"Arial\">Laser Drill Microvia Minimum<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"312\"><span data-font-family=\"Arial\">2 mil (0.05 mm)<\/span><\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\" width=\"312\"><span data-font-family=\"Arial\">Fabrication Allowance (IPC-2221C)<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"312\"><span data-font-family=\"Arial\">8 mil maximum drill wander<\/span><\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\" width=\"312\"><span data-font-family=\"Arial\">Typical Pad Size (Class 1\/2)<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"312\"><span data-font-family=\"Arial\">Via diameter + 8 mil<\/span><\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\" width=\"312\"><span data-font-family=\"Arial\">Typical Pad Size (Class 3)<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"312\"><span data-font-family=\"Arial\">Via diameter + 10 mil<\/span><\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\" width=\"312\"><span data-font-family=\"Arial\">Copper Weight Adjustment<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"312\"><span data-font-family=\"Arial\">+2 mil per additional oz\/ft\u00b2 above 1 oz<\/span><\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\" width=\"312\"><span data-font-family=\"Arial\">Layer Count Adjustment<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"312\"><span data-font-family=\"Arial\">+2 mil for boards with &gt;8 layers<\/span><\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\" width=\"312\"><span data-font-family=\"Arial\">Governing Standards<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"312\"><span data-font-family=\"Arial\">IPC-2221C, IPC-6012D, IPC-2226<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h2><b><span data-font-family=\"Arial\">Customization &amp; Design Options<\/span><\/b><\/h2>\n<p><span data-font-family=\"Arial\">Annular ring sizing is configurable at the design stage based on the following parameters:<\/span><\/p>\n<ul>\n<li><span data-font-family=\"Arial\">Via type: Through-hole vias require larger rings (4\u20138 mil) than laser-drilled microvias (2\u20134 mil) due to mechanical drill wander tolerances.<\/span><\/li>\n<li><span data-font-family=\"Arial\">IPC product class: Select Class 1 (consumer), Class 2 (general industrial), or Class 3 (high-reliability) to define the minimum acceptable ring width and breakout policy.<\/span><\/li>\n<li><span data-font-family=\"Arial\">Copper weight: For 2 oz\/ft\u00b2 copper, add 2 mil to the base ring minimum; adjust accordingly for heavier weights.<\/span><\/li>\n<li><span data-font-family=\"Arial\">Layer count: Boards exceeding 8 layers require an additional 2 mil allowance due to layer-to-layer registration stack-up.<\/span><\/li>\n<li><span data-font-family=\"Arial\">Teardrop pads: Add teardrop fillets at trace-to-pad junctions for traces narrower than 20 mil, or on all vias for Class 3 and flex PCBs.<\/span><\/li>\n<li><span data-font-family=\"Arial\">Via-in-pad (VIP): HDI designs using via-in-pad require copper filling and planarization; annular ring sized to IPC-2226 Level B (0.025 mm minimum).<\/span><\/li>\n<li><span data-font-family=\"Arial\">Anti-pad sizing: For vias passing through non-connected copper planes, the anti-pad diameter must clear the annular ring per IPC-2221C guidance.<\/span><\/li>\n<\/ul>\n<h2><b><span data-font-family=\"Arial\">Application Scenarios<\/span><\/b><\/h2>\n<h4><b><span data-font-family=\"Arial\">Consumer Electronics (Class 1\u20132)<\/span><\/b><\/h4>\n<p><span data-font-family=\"Arial\">Smartphones, wearables, and laptop motherboards use minimum annular rings (4\u20135 mil) to maximize routing density on fine-pitch BGA layers. Tangency is generally acceptable; breakout is managed through high-precision automated drilling.<\/span><\/p>\n<h4><b><span data-font-family=\"Arial\">Industrial Automation &amp; Control (Class 2)<\/span><\/b><\/h4>\n<p><span data-font-family=\"Arial\">PLC backplanes, motor drives, and sensor interface boards require Class 2 compliance where 90\u00b0 breakout is permitted but tightly monitored. Rings of 5\u20136 mil support reliable operation across wide temperature ranges.<\/span><\/p>\n<h4><b><span data-font-family=\"Arial\">Medical Devices (Class 3 \/ IPC-6012 EM)<\/span><\/b><\/h4>\n<p><span data-font-family=\"Arial\">ECG monitors, surgical robotics, and implantable device PCBs mandate IPC-6012 EM Class 3 compliance. Minimum 2 mil external rings with teardrop pads are non-negotiable; failure can be life-critical.<\/span><\/p>\n<h4><b><span data-font-family=\"Arial\">Aerospace &amp; Defense (Class 3 \/ IPC-6012 ES)<\/span><\/b><\/h4>\n<p><span data-font-family=\"Arial\">Avionics, radar systems, and satellite boards must survive extreme thermal cycling (\u221255\u00b0C to +125\u00b0C) and vibration. Class 3 rings of 3\u20135 mil with mandatory teardrops and high-Tg laminates are standard.<\/span><\/p>\n<h4><b><span data-font-family=\"Arial\">Automotive Electronics (Class 2\u20133 \/ IPC-6012 EA)<\/span><\/b><\/h4>\n<p><span data-font-family=\"Arial\">ADAS modules, ECUs, and battery management systems operate in high-vibration, wide-temperature environments. IPC-6012 EA specifies automotive-specific annular ring and via reliability criteria.<\/span><\/p>\n<h4><b><span data-font-family=\"Arial\">High-Frequency RF &amp; Telecommunications<\/span><\/b><\/h4>\n<p><span data-font-family=\"Arial\">RF PCBs require consistent pad geometry to avoid impedance discontinuities at the via transition. Circular, uniform annular rings are preferred; irregular shapes introduce parasitic capacitance degrading signal integrity above 5 GHz.<\/span><\/p>\n<h2><b><span data-font-family=\"Arial\">Manufacturing Capability<\/span><\/b><\/h2>\n<p><span data-font-family=\"Arial\">Professional PCB fabricators control annular ring quality through a combination of precision equipment and process controls. Leading manufacturers use vision-registered drilling (optical fiducial alignment) to reduce drill wander to \u00b11\u20132 mil for standard mechanical drills, and laser-drilling systems achieve positional accuracy better than \u00b10.5 mil for microvias. Hole size tolerances for plated holes are typically controlled within \u00b13 mil; press-fit and non-plated holes achieve \u00b12 mil.<\/span><\/p>\n<p><span data-font-family=\"Arial\">Prototype runs are typically available with a 24\u201372 hour turn, allowing design teams to validate annular ring adequacy before committing to production. Most fabricators offer DFM review as standard \u2014 CAM engineers analyze Gerber files for annular ring violations, drill-to-copper clearances, and pad registration before releasing to the floor. Engineering support for teardrop addition, anti-pad sizing, and IPC class documentation is widely available. Production quantities benefit from automated optical inspection (AOI) and X-ray cross-section analysis to verify ring integrity on inner layers. Lead times for production quantities range from 5 to 15 working days with global shipping support for most major markets within 3\u20135 days.<\/span><\/p>\n<h2><b><span data-font-family=\"Arial\">Comparison: IPC Class Requirements<\/span><\/b><\/h2>\n<table>\n<tbody>\n<tr>\n<td colspan=\"1\" rowspan=\"1\" width=\"156\"><b><span data-font-family=\"Arial\">Attribute<\/span><\/b><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"156\"><b><span data-font-family=\"Arial\">Class 1 (General)<\/span><\/b><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"156\"><b><span data-font-family=\"Arial\">Class 2 (Dedicated Service)<\/span><\/b><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"156\"><b><span data-font-family=\"Arial\">Class 3 (High Reliability)<\/span><\/b><\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\" width=\"156\"><span data-font-family=\"Arial\">Typical Applications<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"156\"><span data-font-family=\"Arial\">Consumer, toys, non-critical<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"156\"><span data-font-family=\"Arial\">Telecom, industrial, computers<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"156\"><span data-font-family=\"Arial\">Medical, aerospace, military<\/span><\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\" width=\"156\"><span data-font-family=\"Arial\">External Ring Minimum<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"156\"><span data-font-family=\"Arial\">\u2248 plating thickness<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"156\"><span data-font-family=\"Arial\">0 mil (tangency ok)<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"156\"><span data-font-family=\"Arial\">2 mil (0.05 mm)<\/span><\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\" width=\"156\"><span data-font-family=\"Arial\">Internal Ring Minimum<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"156\"><span data-font-family=\"Arial\">0 mil (breakout allowed)<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"156\"><span data-font-family=\"Arial\">0 mil (breakout allowed)<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"156\"><span data-font-family=\"Arial\">1 mil (0.025 mm)<\/span><\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\" width=\"156\"><span data-font-family=\"Arial\">Breakout Policy<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"156\"><span data-font-family=\"Arial\">Permitted<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"156\"><span data-font-family=\"Arial\">90\u00b0 breakout allowed<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"156\"><span data-font-family=\"Arial\">Not permitted<\/span><\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\" width=\"156\"><span data-font-family=\"Arial\">Tangency Policy<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"156\"><span data-font-family=\"Arial\">Permitted<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"156\"><span data-font-family=\"Arial\">Permitted with conditions<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"156\"><span data-font-family=\"Arial\">Not permitted<\/span><\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\" width=\"156\"><span data-font-family=\"Arial\">Teardrop Requirement<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"156\"><span data-font-family=\"Arial\">Not required<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"156\"><span data-font-family=\"Arial\">Recommended &lt;20 mil traces<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"156\"><span data-font-family=\"Arial\">Mandatory<\/span><\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\" width=\"156\"><span data-font-family=\"Arial\">Governing Standard<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"156\"><span data-font-family=\"Arial\">IPC-6012 Class 1<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"156\"><span data-font-family=\"Arial\">IPC-6012 Class 2<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"156\"><span data-font-family=\"Arial\">IPC-6012 Class 3 \/ -ES \/ -EM \/ -EA<\/span><\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\" width=\"156\"><span data-font-family=\"Arial\">Relative Mfg. Cost<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"156\"><span data-font-family=\"Arial\">Lowest<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"156\"><span data-font-family=\"Arial\">Moderate<\/span><\/td>\n<td colspan=\"1\" rowspan=\"1\" width=\"156\"><span data-font-family=\"Arial\">Highest (~2\u00d7 Class 2)<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h2><b><span data-font-family=\"Arial\">Frequently Asked Questions<\/span><\/b><\/h2>\n<h3><b><span data-font-family=\"Arial\">Q1: What is the difference between tangency and breakout?<\/span><\/b><\/h3>\n<p><span data-font-family=\"Arial\">Tangency occurs when the drilled hole is slightly off-center and its outer edge just touches the outer edge of the copper pad, leaving effectively zero ring width on one side. Breakout is more severe: the drill exits the pad boundary entirely, leaving no copper on that side and creating a risk of open circuit. Under IPC-6012, Class 1 and 2 boards permit 90-degree breakout provided the connection remains functional, while Class 3 boards permit neither tangency nor breakout.<\/span><\/p>\n<h3><b><span data-font-family=\"Arial\">Q2: How do I calculate the correct pad diameter for a given IPC class?<\/span><\/b><\/h3>\n<p><span data-font-family=\"Arial\">Use the formula: Pad Diameter = Finished Hole Diameter + 2 \u00d7 (Minimum Annular Ring) + Fabrication Allowance. For a Class 3 board with a 0.3 mm (12 mil) finished hole, a 2 mil minimum ring, and an 8 mil fabrication allowance: Pad = 12 + 2(2) + 8 = 24 mil (0.61 mm). Add 2 mil for boards with more than 8 layers or copper weight above 1 oz\/ft\u00b2.<\/span><\/p>\n<h3><b><span data-font-family=\"Arial\">Q3: Can I use the same annular ring size for internal and external layers?<\/span><\/b><\/h3>\n<p><span data-font-family=\"Arial\">No. IPC standards measure external and internal rings differently. External rings are measured from the edge of the copper-plated via wall to the pad edge, while internal rings are measured from the raw drilled hole edge. Because plating adds approximately 1 mil to the hole wall, the same physical pad produces an external ring reading that is ~1 mil smaller than the internal reading. For Class 3, specify 2 mil minimum externally and 1 mil minimum internally.<\/span><\/p>\n<h3><b><span data-font-family=\"Arial\">Q4: When should I add teardrop pads to my via annular rings?<\/span><\/b><\/h3>\n<p><span data-font-family=\"Arial\">Teardrops should be added whenever a trace narrower than 20 mil (0.5 mm) connects to a via, on all vias in Class 3 designs, and on all vias in flex or rigid-flex PCBs subject to bending or vibration. Teardrops add a gradual copper fillet at the trace-to-pad junction, preventing trace severance if the drill slightly encroaches on that side, and improving resistance to fatigue cracking at the copper-laminate interface.<\/span><\/p>\n<h3><b><span data-font-family=\"Arial\">Q5: How does HDI microvia design change annular ring requirements?<\/span><\/b><\/h3>\n<p><span data-font-family=\"Arial\">Laser-drilled microvias (typically 0.075\u20130.125 mm diameter) are governed by IPC-2226 rather than IPC-2221. The minimum annular ring for HDI microvias under IPC-2226 Level B is 0.025 mm (1 mil) \u2014 achievable because laser drilling achieves positional accuracy better than \u00b10.5 mil, far tighter than mechanical CNC drilling. Designers should also ensure microvias are properly filled and planarized to \u00b15 \u00b5m before placing components or via-in-pad structures on top.<\/span><\/p>\n<h2><b><span data-font-family=\"Arial\">What You Can Find in <a href=\"http:\/\/lcsc.com\">LCSC<\/a><\/span><\/b><\/h2>\n<p><span data-font-family=\"Arial\">LCSC Electronics \u2014 the component sourcing platform operated by JLCPCB&#8217;s parent company EasyEDA \u2014 carries an extensive catalogue of through-hole and SMD components that pair directly with the annular ring specifications discussed in this article. Whether you are designing to IPC Class 2 tolerances for an industrial controller or Class 3 standards for a medical device, LCSC provides a single-source destination for the passive and active components your PCB layout requires.<\/span><\/p>\n<p><span data-font-family=\"Arial\">LCSC also provides competitive pricing on popular IPC-compliant components from both international brands and high-quality Asian manufacturers, making it a practical sourcing option for prototype quantities through volume production. With real-time stock visibility and global shipping to over 200 countries, engineers can move from validated PCB design to component procurement without switching platforms \u2014 a meaningful efficiency gain on time-sensitive projects.<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u00a0Key Takeaways Annular ring = copper pad area surrounding a drilled or laser-machined PCB hole. Width = (Pad Diameter \u2013 Finished Hole Diameter) \/ 2; ranges from 1 mil (HDI microvias) to 8+ mil (standard). IPC Class 3 requires \u22652 mil on external layers and \u22651 mil on internal layers; zero breakout or tangency. Teardrop [&hellip;]<\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"iawp_total_views":3,"footnotes":""},"categories":[177,175],"tags":[181,155],"class_list":["post-4262","post","type-post","status-publish","format-standard","hentry","category-pcb-techniques","category-pcb-smt","tag-pcb","tag-pcba"],"blocksy_meta":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.8 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>PCB Annular Ring Guide: Sizing Rules &amp; IPC Standards Blog | LCSC Electronics<\/title>\n<meta name=\"description\" content=\"Learn PCB annular ring IPC rules and source matching components at LCSC Electronics.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/blogs.lcsc.com\/blog\/pcb-annular-ring-guide\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"PCB Annular Ring Guide: Sizing Rules &amp; 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