{"id":1576,"date":"2026-08-10T08:24:29","date_gmt":"2026-08-10T00:24:29","guid":{"rendered":"https:\/\/www.jingpengpcb.com\/?p=1576"},"modified":"2026-10-02T19:37:42","modified_gmt":"2026-10-02T11:37:42","slug":"hdi-manufacturing-process","status":"publish","type":"post","link":"https:\/\/www.jingpengpcb.com\/en\/blog\/hdi-manufacturing-process\/","title":{"rendered":"A Comprehensive Analysis of the HDI PCB Manufacturing Process: From Single-Layer to Any Number of Layers"},"content":{"rendered":"<style>\n.jp-tw{overflow-x:auto;margin:26px 0;-webkit-overflow-scrolling:touch;}\n.jp-tw table{border-collapse:collapse;width:100%;min-width:560px;font-size:15px;line-height:1.65;background:#fff;}\n.jp-tw th,.jp-tw td{border:1px solid #dde3ea;padding:11px 14px;text-align:left;vertical-align:top;}\n.jp-tw thead th{background:#eef2f7;color:#1b2733;font-weight:700;white-space:nowrap;border-bottom:2px solid #c9d3de;}\n.jp-tw tbody tr:nth-child(even){background:#fafbfc;}\n.jp-tw tbody tr:hover{background:#f1f5fa;}\n.jp-tw tbody td:first-child{font-weight:600;color:#1b2733;}\n@media(max-width:767px){.jp-tw table{font-size:14px;min-width:520px;}.jp-tw th,.jp-tw td{padding:9px 11px;}}\n<\/style>\n<p>High-density interconnect (HDI) circuit boards are the core hardware foundation for smartphones, wearable devices, 5G base stations, and aerospace electronic systems.<\/p>\n<p>As end products have evolved toward smaller sizes and greater multifunctionality, the manufacturing process for HDI boards has also gradually progressed from the initial first- and second-order structures to third-order and even \u201cAny Layer\u201d structures.<\/p>\n<p>Understanding the engineering rationale behind these order levels is crucial for hardware engineers, procurement managers, and product decision-makers.<\/p>\n<p>This article will provide an in-depth analysis of the differences in the production processes for HDI boards of various tiers, focusing on core processes such as lamination, drilling, and electroplating, and will offer recommendations for selecting the appropriate type.<\/p>\n<h2>1. Basic Concepts and Order Definitions for HDI Circuit Boards<\/h2>\n<p>The essence of HDI (High-Density Interconnect) circuit boards is achieved through<strong>Micro-blind holes<\/strong>(Microvia) and<strong>Blind Hole<\/strong>(Buried Via) enables high-density interconnects, with line widths and line spacings typically \u22644 mil and via diameters \u22640.15 mm.<\/p>\n<p>\"Order\" refers to the process in build-up manufacturing,<strong>Number of Laser Drilling (Laser Hole Formation) Cycles<\/strong>. Each laser drilling operation adds another step to the connection between the outer and inner layers.<\/p>\n<p>For example, a first-order board has a \u201c1+N+1\u201d structure, while a second-order board has a \u201c2+N+2\u201d or \u201c1+1+N+1+1\u201d structure; the higher the order, the greater the number of internal interconnect layers, and the greater the routing flexibility.<\/p>\n<h2>2. First-Order HDI Manufacturing Process: An Entry-Level High-Density Solution<\/h2>\n<p>First-order HDI is the most basic type of HDI. With its mature manufacturing process and high yield rates, it is widely used in entry-level cell phones, industrial control modules, and IoT sensors.<\/p>\n<h3>2.1 Core Processes and Structure<\/h3>\n<p>The manufacturing of first-order HDI can be summarized as follows:<strong>\u201cOne pressing operation + one laser drilling operation\u201d<\/strong>\u3002<\/p>\n<p>Taking a 6-layer first-order board as an example, its structure consists of laser-drilled blind vias on layers L1 and L2, laser-drilled blind vias on layers L5 and L6, and mechanical through-holes connecting inner layers L2 through L5. The specific steps include:<\/p>\n<ul>\n<li><strong>Manufacturing the Inner Core Panel<\/strong>: Material cutting, inner layer circuit etching, AOI optical inspection.<\/li>\n<li><strong>Single-pass pressing<\/strong>: The core board, prepreg, and copper foil are laminated together under high temperature and pressure to form a multilayer substrate.<\/li>\n<li><strong>Mechanical Drilling<\/strong>: Drill through-holes that penetrate the entire thickness of the board (for internal interconnects).<\/li>\n<li><strong>Electrolytic Copper Plating and Electroplating<\/strong>: Metallize the through-holes.<\/li>\n<li><strong>Outer-layer laser drilling<\/strong>: Use a CO\u2082 or UV laser to ablate the dielectric layer at predetermined pad locations, forming blind vias (L1-L2) with a typical diameter of 0.1 mm.<\/li>\n<li><strong>Outer Layer Circuit Fabrication<\/strong>: Plating to fill holes, circuit etching, solder mask application, and surface treatment.<\/li>\n<\/ul>\n<h3>2.2 Process Characteristics and Limitations<\/h3>\n<p>First-order HDI allows interconnections only between the outer layer and the adjacent inner layer (Layer 2); it cannot directly connect to inner layers deeper than that.<\/p>\n<p>Therefore, when component pin density is high, first-order boards often lack sufficient routing channels, limiting further increases in routing density.<\/p>\n<h2>3. Second-Generation HDI Manufacturing Process: The Top Choice for Mid- to High-End Performance<\/h2>\n<p>Second-order HDI is widely used in smartphone motherboards, tablets, and automotive radar systems; it offers higher interconnect density while keeping costs within a manageable range.<\/p>\n<h3>3.1 Two Mainstream Design Types<\/h3>\n<p>Second-order HDI is not a single process; depending on the blind via stacking method, it is classified into<strong>Staggered Pattern<\/strong>\u548c<strong>Stacked Type<\/strong>, and in addition, there is<strong>Direct-Drilling Type<\/strong>(Drill a hole through the outer layer to penetrate two layers of material).<\/p>\n<ul>\n<li><strong>Offset Hole Type<\/strong>: The two laser-drilled holes are offset from each other and connected by short conductors in the intermediate layer. This process is relatively simple and has low alignment tolerance requirements, making it the mainstream solution for second-order boards.<\/li>\n<li><strong>Stacked-hole type<\/strong>: When the second blind hole is vertically superimposed on the first blind hole (e.g., L1-L2-L3 through-holes), it is necessary to use<strong>Electroplating to Fill Holes<\/strong>The process requires that the blind holes in the lower layer be completely filled before drilling can begin on the upper layer. This places extremely high demands on the smoothness of the filled holes and the precision of interlayer alignment, resulting in a significant increase in costs.<\/li>\n<li><strong>Direct-Drilling Type<\/strong>: Using a high-energy laser to penetrate two layers of material in a single pass (e.g., drilling directly from L1 to L3) places stringent demands on laser energy control and material properties, and is therefore rarely used.<\/li>\n<\/ul>\n<h3>3.2 Core Manufacturing Process (Using the Offset-Hole Type as an Example)<\/h3>\n<ul>\n<li><strong>First Pressing<\/strong>: Manufacture the inner core panel and press it together.<\/li>\n<li><strong>First Laser Drilling<\/strong>: Drill blind holes through L2-L3 (or the secondary outer layer and the inner layer).<\/li>\n<li><strong>Electroplating and Via Filling<\/strong>: Electroplating is used to fill the blind holes on this layer.<\/li>\n<li><strong>Second Pressing<\/strong>: Apply another layer of prepreg and copper foil to form a new outer layer.<\/li>\n<li><strong>Second Laser Drilling<\/strong>: Drill blind holes in L1-L2 (offset from the positions of the first set of blind holes).<\/li>\n<li><strong>Outer Layer Traces<\/strong>: Complete subsequent processes such as electroplating and etching.<\/li>\n<\/ul>\n<p>Second-order HDI requirements<strong>Two press runs, two laser drilling operations<\/strong>, the process complexity increases by approximately 50% compared to the first-order process, and costs typically rise by 20% to 30%.<\/p>\n<h2>4. Three-layer and higher, and HDI at any layer: cutting-edge technology<\/h2>\n<p>When the order reaches the third order ((3+N+3)) or higher, it is common to use<strong>Any Layer<\/strong>The design allows each layer to be interconnected with any other layer via blind vias.<\/p>\n<p>This structure is commonly found in the fan-out regions of flagship smartphone main chips and high-end AI accelerator cards.<\/p>\n<ul>\n<li><strong>Stacked Micro-Blind Holes<\/strong>: All blind holes are stacked, requiring multiple electroplating cycles to fill the holes and precise alignment; the coefficient of thermal expansion must be strictly controlled during each lamination and drilling process.<\/li>\n<li><strong>Accuracy of Laser Drilling Machines<\/strong>: Positioning accuracy must be \u2264\u00b15 \u03bcm, and real-time compensation for material deformation is required.<\/li>\n<li><strong>Material Selection<\/strong>: It is essential to use specialized HDI substrates with low expansion and high Tg (such as the Panasonic MEGTRON series), in combination with low-flow prepregs, to ensure consistent layer thickness.<\/li>\n<\/ul>\n<p>The manufacturing cycle for any-layer HDI is more than twice as long as that for second-order HDI, and the yield rate drops significantly; therefore, it is used only in scenarios with extreme requirements for space and electrical performance.<\/p>\n<h2>5. In-Depth Comparison of Key Process Technologies<\/h2>\n<p>To provide a clearer understanding of the differences between the various stages, the table below summarizes the key process parameters and cost factors:<\/p>\n<div class=\"jp-tw\">\n<table style=\"border-collapse: collapse; width: 100%; font-size: 0.95em;\" border=\"1\" cellpadding=\"6\">\n<tbody>\n<tr style=\"background: #f2f2f2;\">\n<th>Project<\/th>\n<th>First-Order HDI<\/th>\n<th>Second-Order HDI (Staggered Via)<\/th>\n<th>Second-Order HDI (Stacked Vias)<\/th>\n<th>Any Layer (Level 3+)<\/th>\n<\/tr>\n<tr>\n<td>Number of Pressing Cycles<\/td>\n<td>1<\/td>\n<td>2<\/td>\n<td>2<\/td>\n<td>\u22653<\/td>\n<\/tr>\n<tr>\n<td>Number of Laser Drilling Cycles<\/td>\n<td>1<\/td>\n<td>2<\/td>\n<td>2<\/td>\n<td>\u22653<\/td>\n<\/tr>\n<tr>\n<td>Blind Hole Structure<\/td>\n<td>Single-layer (L1-L2)<\/td>\n<td>Staggered over two levels<\/td>\n<td>Vertical Stacking<\/td>\n<td>Full Stack<\/td>\n<\/tr>\n<tr>\n<td>Hole-Filling Requirements<\/td>\n<td>Standard Plated Holes<\/td>\n<td>Standard Plated Holes<\/td>\n<td>Completely leveled<\/td>\n<td>Completely leveled<\/td>\n<\/tr>\n<tr>\n<td>Alignment Accuracy (\u03bcm)<\/td>\n<td>\u00b125<\/td>\n<td>\u00b115<\/td>\n<td>\u00b18<\/td>\n<td>\u00b15<\/td>\n<\/tr>\n<tr>\n<td>Relative Cost (with through-hole boards set to 1)<\/td>\n<td>1.5<\/td>\n<td>2.0<\/td>\n<td>2.5<\/td>\n<td>3.5~5.0<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<h2>6. Technical Details of Laser Drilling and Electroplating Hole Filling<\/h2>\n<p>Regardless of the number of layers, laser drilling and electroplating are both core processes that determine the reliability of HDI boards.<\/p>\n<ul>\n<li><strong>CO\u2082 Laser<\/strong>(Wavelength: 9.4 \u03bcm) This is primarily used for processing media layers containing glass fibers; the energy density is typically set at 2\u20133 J\/cm\u00b2, and the hole wall roughness is \u226410 \u03bcm.<\/li>\n<li><strong>UV Laser<\/strong>(Wavelength: 355 nm) It can directly ablate copper foil and is suitable for ultra-small apertures (&lt;75 \u03bcm) and stacked-hole applications, but its production efficiency is only one-third that of a CO\u2082 laser.<\/li>\n<li><strong>Electroplating to Fill Holes<\/strong>Special additives (brighteners, leveling agents, and inhibitors) are required to ensure upward filling of the bottoms of blind vias through pulse electroplating, thereby preventing voids. Inadequate via filling can lead to fractures after thermal cycling and is one of the primary causes of early HDI failure.<\/li>\n<\/ul>\n<h2>7. How to Choose the Right Order? \u2014 A Guide to Engineering Decision-Making<\/h2>\n<p>When selecting an order, one should not simply assume that \u201chigher is better\u201d; instead, the following factors should be considered comprehensively:<\/p>\n<ul>\n<li><strong>Wiring Density<\/strong>: If the BGA pitch is \u22640.4 mm or the number of pins exceeds 300, it is recommended to use at least second-order HDI; if the pitch is \u22640.3 mm, any layer should be considered.<\/li>\n<li><strong>Signal Integrity<\/strong>: High-speed signals (\u226510 Gbps) require shorter return paths; stacked vias can reduce via stubs, which improves SI\/PI performance.<\/li>\n<li><strong>Cost Budget<\/strong>: Second-order stacked pores are approximately 251 TP3T more expensive than misaligned pores, and the cost increases exponentially for any layer. Given that performance requirements are met, low-order solutions should be prioritized.<\/li>\n<li><strong>Delivery Date<\/strong>: The manufacturing cycle for high-density interconnect (HDI) boards is typically 5 to 8 days longer than that for first-order boards, which directly affects time to market.<\/li>\n<\/ul>\n<p>The evolution of HDI circuit board layers is, at its core, a continuous response by manufacturing processes to the demand for increased integration in electronic systems.<\/p>\n<p>First-order boards offer cost-effective solutions for basic interconnects; second-order via-in-via boards strike a good balance between density and cost, making them the mainstream choice for mid- to high-end products; and any-layer HDI boards represent the pinnacle of current mass-production processes, providing the physical foundation for top-tier performance.<\/p>\n<p>As an electronics engineer or product manager, a deep understanding of the technical details of each process node not only helps optimize designs but also enables you to make informed trade-offs between cost, performance, and manufacturability.<\/p>\n<p>In the future, as mSAP (modified semi-additive process) and embedded passive component technologies advance, the limits on the number of layers in HDI may be redefined; however, the basic process chain of \u201cdrilling\u2014lamination\u2014plating\u201d will remain the core framework of PCB manufacturing.<\/p>\n<hr \/>\n<h3>Frequently Asked Questions<\/h3>\n<dl>\n<dt><strong>1. What is the difference between \u201corder\u201d and \u201clayer\u201d in HDI?<\/strong><\/dt>\n<dd>\u201cLayers\u201d refers to the physical number of layers in a PCB (e.g., 6-layer, 8-layer), while \u201corder\u201d refers to the number of laser drilling passes. A 6-layer PCB can be first-order (1+N+1) or second-order (2+N+2), depending on the number of dielectric layers traversed by the blind vias.<\/dd>\n<dt><strong>2. Is second-order HDI always better than first-order HDI?<\/strong><\/dt>\n<dd>Not necessarily. If the trace density is high enough, first-order boards offer better advantages in terms of cost, lead time, and reliability. Only higher-order products require second-order or higher-order HDI.<\/dd>\n<dt><strong>3. Why is the yield rate lower for high-density interconnect (HDI) boards?<\/strong><\/dt>\n<dd>The main reasons are the cumulative errors caused by repeated lamination, as well as inconsistencies in via filling and plating during the via-stacking process; these factors reduce the yield and increase testing costs.<\/dd>\n<dt><strong>4. Is HDI on any layer equivalent to a \u201cblind via\u201d design?<\/strong><\/dt>\n<dd>Yes, all interlayer connections in any HDI layer are achieved through stacked micro-blind vias; mechanical through-holes are no longer used, thereby enabling extremely high pin fan-out density.<\/dd>\n<dt><strong>5. How do you determine how many layers of HDI a project requires?<\/strong><\/dt>\n<dd>We recommend using PCB design tools (such as Allegro or Mentor) to perform a preliminary routing evaluation. If all signal fan-outs cannot be completed with the current number of stages, you will need to increase the number of stages; you may also consult the PCB manufacturer for DFM (Design for Manufacturability) recommendations.<\/dd>\n<\/dl>\n<p style=\"margin-top: 20px; color: #555; font-size: 0.9em;\">This article is based on current mainstream HDI manufacturing processes; adjustments should be made during actual production to account for specific materials and equipment capabilities. If you would like to discuss technical matters further, please feel free to contact us at any time.<\/p>","protected":false},"excerpt":{"rendered":"<p>\u9ad8\u5bc6\u5ea6\u4e92\u8fde\uff08HDI\uff09\u7535\u8def\u677f\u662f\u667a\u80fd\u624b\u673a\u3001\u53ef\u7a7f\u6234\u8bbe\u5907\u30015G\u57fa\u7ad9\u548c\u822a\u7a7a\u822a\u5929\u7535\u5b50\u7cfb\u7edf\u7684\u6838\u5fc3\u786c\u4ef6\u57fa\u7840\u3002 \u968f\u7740\u7ec8\u7aef\u4ea7\u54c1\u5411\u5c0f [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":12801,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"slim_seo":{"title":"A Comprehensive Analysis of the HDI PCB Manufacturing Process: From Single-Layer to Any Number of Layers","description":"How are HDI boards manufactured? Break down the manufacturing process and differences in the laminate structure step by step\u2014from first-order, second-order, and third-order to any number of layers\u2014and explain the process limitations and applicable scenarios for each order."},"_slim_seo_primary_term_category":0,"_slim_seo_primary_term_post_tag":0,"footnotes":""},"categories":[26],"tags":[46,289],"class_list":["post-1576","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-blog","tag-hdi"],"_links":{"self":[{"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/posts\/1576","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/comments?post=1576"}],"version-history":[{"count":3,"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/posts\/1576\/revisions"}],"predecessor-version":[{"id":13366,"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/posts\/1576\/revisions\/13366"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/media\/12801"}],"wp:attachment":[{"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/media?parent=1576"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/categories?post=1576"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/tags?post=1576"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}