{"id":12027,"date":"2025-08-15T11:55:06","date_gmt":"2025-08-15T03:55:06","guid":{"rendered":"https:\/\/www.bestpcbs.com\/blog\/?p=12027"},"modified":"2025-08-15T12:00:12","modified_gmt":"2025-08-15T04:00:12","slug":"4-layer-rigid-flex-pcb-design-manufacturer-fast-delivery","status":"publish","type":"post","link":"https:\/\/www.bestpcbs.com\/blog\/2025\/08\/4-layer-rigid-flex-pcb-design-manufacturer-fast-delivery\/","title":{"rendered":"4-Layer Rigid Flex PCB Design &amp; Manufacturer, Fast Delivery"},"content":{"rendered":"<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_82_2 ez-toc-wrap-left counter-hierarchy ez-toc-counter ez-toc-grey ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">Table of Contents<\/p>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"Toggle Table of Content\"><span class=\"ez-toc-js-icon-con\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/span><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/www.bestpcbs.com\/blog\/2025\/08\/4-layer-rigid-flex-pcb-design-manufacturer-fast-delivery\/#What_Is_a_4-Layer_Rigid_Flex_PCB\" >What Is a 4-Layer Rigid Flex PCB?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/www.bestpcbs.com\/blog\/2025\/08\/4-layer-rigid-flex-pcb-design-manufacturer-fast-delivery\/#4_Layer_Rigid_Flex_PCB_Stackup\" >4 Layer Rigid Flex PCB Stackup<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/www.bestpcbs.com\/blog\/2025\/08\/4-layer-rigid-flex-pcb-design-manufacturer-fast-delivery\/#How_thick_is_a_4-Layer_Rigid_Flex_PCB\" >How thick is a 4-Layer Rigid Flex PCB?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/www.bestpcbs.com\/blog\/2025\/08\/4-layer-rigid-flex-pcb-design-manufacturer-fast-delivery\/#Why_Use_4-Layer_Rigid_Flex_PCB\" >Why Use 4-Layer Rigid Flex PCB?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/www.bestpcbs.com\/blog\/2025\/08\/4-layer-rigid-flex-pcb-design-manufacturer-fast-delivery\/#When_to_Use_4_Layer_Rigid_Flex_PCB\" >When to Use 4 Layer Rigid Flex PCB?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/www.bestpcbs.com\/blog\/2025\/08\/4-layer-rigid-flex-pcb-design-manufacturer-fast-delivery\/#How_to_Design_a_4-Layer_Rigid_Flex_PCB\" >How to Design a 4-Layer Rigid Flex PCB?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/www.bestpcbs.com\/blog\/2025\/08\/4-layer-rigid-flex-pcb-design-manufacturer-fast-delivery\/#How_to_Make_a_4-Layer_Rigid_Flex_PCB\" >How to Make a 4-Layer Rigid Flex PCB?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-8\" href=\"https:\/\/www.bestpcbs.com\/blog\/2025\/08\/4-layer-rigid-flex-pcb-design-manufacturer-fast-delivery\/#Why_Choose_EBest_Circuit_Best_Technology_as_Rigid_Flex_PCB_Manufacturer\" >Why Choose EBest Circuit (Best Technology) as Rigid Flex PCB Manufacturer?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-9\" href=\"https:\/\/www.bestpcbs.com\/blog\/2025\/08\/4-layer-rigid-flex-pcb-design-manufacturer-fast-delivery\/#Our_Rigid-Flex_PCB_Capabilities\" >Our Rigid-Flex PCB Capabilities<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-10\" href=\"https:\/\/www.bestpcbs.com\/blog\/2025\/08\/4-layer-rigid-flex-pcb-design-manufacturer-fast-delivery\/#How_Can_I_Get_a_Quote_for_a_4_Layer_Rigid-Flex_PCB\" >How Can I Get a Quote for a 4 Layer Rigid-Flex PCB?<\/a><\/li><\/ul><\/nav><\/div>\n<div class=\"yzp-no-index\"><\/div>\n<p>What is a <strong><a href=\"https:\/\/www.bestpcbs.com\/blog\/2025\/08\/4-layer-rigid-flex-pcb-design-manufacturer-fast-delivery\/\" title=\"\">4-layer rigid flex PCB<\/a><\/strong>? Let&#8217;s explore its stackup, thickness, benefits, applications, design guide and manufacturing processes through this blog.<\/p>\n\n\n\n<p><strong><mark style=\"background-color:rgba(0, 0, 0, 0);color:#079cf9\" class=\"has-inline-color\">Are you troubled with these issues?<\/mark><\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong><mark style=\"background-color:rgba(0, 0, 0, 0);color:#079cf9\" class=\"has-inline-color\">Is the line impedance fluctuation exceeding the standard after the product is bent? (Precision impedance control is used on rigid-flex boards, ensuring fluctuations of &lt;5% after bending)<\/mark><\/strong><\/li>\n\n\n\n<li><strong><mark style=\"background-color:rgba(0, 0, 0, 0);color:#079cf9\" class=\"has-inline-color\">Is stress concentration causing cracking during multi-module assembly? (A four-layer stepped transition design distributes 90% of mechanical stress)<\/mark><\/strong><\/li>\n\n\n\n<li><strong><mark style=\"background-color:rgba(0, 0, 0, 0);color:#079cf9\" class=\"has-inline-color\">Is crosstalk severe during high-speed signal transmission? (Embedded shielding layer + differential pair routing, crosstalk suppression -50dB)<\/mark><\/strong><\/li>\n<\/ul>\n\n\n\n<p><strong><mark style=\"background-color:rgba(0, 0, 0, 0);color:#079cf9\" class=\"has-inline-color\">EBest Circuit (Best Technology) can provide service:<\/mark><\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong><mark style=\"background-color:rgba(0, 0, 0, 0);color:#079cf9\" class=\"has-inline-color\">Intelligent DFM Platform: Automatically detects design flaws and generates 3D assembly simulation videos<\/mark><\/strong><\/li>\n\n\n\n<li><strong><mark style=\"background-color:rgba(0, 0, 0, 0);color:#079cf9\" class=\"has-inline-color\">Hot-Compression Process Library: Provides six compression profiles, increasing yield to 99.2%<\/mark><\/strong><\/li>\n\n\n\n<li><strong><mark style=\"background-color:rgba(0, 0, 0, 0);color:#079cf9\" class=\"has-inline-color\">Full-Process Dashboard: Real-time display of 12 process statuses, including substrate cutting, lamination, and electroplating<\/mark><\/strong><\/li>\n<\/ul>\n\n\n\n<p><strong><mark style=\"background-color:rgba(0, 0, 0, 0);color:#079cf9\" class=\"has-inline-color\">Welcome to contact us if you have any request for<a href=\"https:\/\/www.bestpcbs.com\/products\/rigid-flex.htm\" title=\"\"> rigid flex PCB<\/a>: <a href=\"mailto:sales@bestpcbs.com\">sales@bestpcbs.com<\/a>.<\/mark><\/strong><\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"What_Is_a_4-Layer_Rigid_Flex_PCB\"><\/span>What Is a 4-Layer Rigid Flex PCB?<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>The<strong> <a href=\"https:\/\/www.bestpcbs.com\/blog\/2025\/08\/4-layer-rigid-flex-pcb-design-manufacturer-fast-delivery\/\" title=\"\">4-Layer rigid flex PCB<\/a><\/strong> is a composite board made by combining a flexible printed circuit board (FPC) and a rigid printed circuit board (PCB) through a special process, which has the characteristics of both. Its core structure usually includes a four-layer design, with the middle two layers being flexible areas and the two sides being rigid areas. The rigid-flex combination is achieved through a lamination process.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full is-resized\"><a href=\"https:\/\/www.bestpcbs.com\/blog\/wp-content\/uploads\/2025\/08\/main-21.jpg\"><img decoding=\"async\" src=\"https:\/\/www.bestpcbs.com\/blog\/wp-content\/uploads\/2025\/08\/main-21.jpg\" alt=\"What Is a 4-Layer Rigid Flex PCB?\" class=\"wp-image-12029\" style=\"width:840px;height:auto\"\/><\/a><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"4_Layer_Rigid_Flex_PCB_Stackup\"><\/span>4 Layer Rigid Flex PCB Stackup<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Layer 1 (Top):<\/strong> Rigid signal layer (routing + key components)<\/li>\n\n\n\n<li><strong>Layer 2 (Inner Layer 1): <\/strong>Flexible ground layer (PI substrate, providing shielding and mechanical support)<\/li>\n\n\n\n<li><strong>Layer 3 (Inner Layer 2): <\/strong>Flexible signal layer (low-speed\/auxiliary signals, optimizing routing density)<\/li>\n\n\n\n<li><strong>Layer 4 (Bottom): <\/strong>Rigid power\/ground plane (FR4, reducing noise coupling)<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"How_thick_is_a_4-Layer_Rigid_Flex_PCB\"><\/span>How thick is a 4-Layer Rigid Flex PCB?<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>A <strong><a href=\"https:\/\/www.bestpcbs.com\/blog\/2025\/08\/4-layer-rigid-flex-pcb-design-manufacturer-fast-delivery\/\" title=\"\">4-layer rigid-flex PCB<\/a><\/strong> typically has a total thickness range of <strong>0.8mm to 1.6mm<\/strong>, depending on the design requirements and material combinations. <strong>Rigid sections<\/strong> (FR4) usually measure <strong>1.2mm<\/strong> thick, providing structural support. <strong>Flex sections<\/strong> (polyimide) are much thinner, commonly <strong>0.1mm<\/strong>, allowing bending and flexibility. The overall thickness is influenced by the copper weight (e.g., 1oz for signal layers, 2oz for power\/ground planes) and dielectric material (FR4 or prepreg) used in the stackup.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Why_Use_4-Layer_Rigid_Flex_PCB\"><\/span>Why Use 4-Layer Rigid Flex PCB?<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>Advantages of 4-layer rigid flex PCB:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Space and Routing Optimization: <\/strong>A layered design separates signal and power planes, increasing wiring density and making it suitable for compact devices like smartphones.<\/li>\n\n\n\n<li><strong>Signal and Electromagnetic Performance:<\/strong> Adjacent power\/ground layers reduce noise, and thick inner copper ensures stable high-speed signal transmission.<\/li>\n\n\n\n<li><strong>Efficient Thermal Management: <\/strong>The inner copper foil evenly dissipates heat, and thermal vias enhance reliability in high-temperature environments.<\/li>\n\n\n\n<li><strong>Mechanical and Durability: <\/strong>A rigid-flexible structure reduces bending failures, and a multi-layered, vibration-resistant design is suitable for industrial applications.<\/li>\n\n\n\n<li><strong>Design and Cost Balance:<\/strong> Customized stacking optimizes performance and cost, while eliminating cables and streamlining the assembly process.<\/li>\n<\/ul>\n\n\n\n<figure class=\"wp-block-image size-full\"><a href=\"https:\/\/www.bestpcbs.com\/blog\/wp-content\/uploads\/2025\/08\/4-6.png\"><img decoding=\"async\" src=\"https:\/\/www.bestpcbs.com\/blog\/wp-content\/uploads\/2025\/08\/4-6.png\" alt=\"Why Use 4-Layer Rigid Flex PCB?\" class=\"wp-image-12030\"\/><\/a><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"When_to_Use_4_Layer_Rigid_Flex_PCB\"><\/span>When to Use 4 Layer Rigid Flex PCB?<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>Applications of  4 Layer Rigid Flex PCB:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>High-Density Electronic Devices<\/strong> &#8211; Smartphones, tablets, and wearables requiring compact layouts with dynamic bending zones.<\/li>\n\n\n\n<li><strong>Automotive Electronics<\/strong> &#8211; Dashboard control units and sensors exposed to vibration and temperature fluctuations.<\/li>\n\n\n\n<li><strong>Medical Devices<\/strong> &#8211; Implantable monitors and portable diagnostics needing lightweight, biocompatible designs.<\/li>\n\n\n\n<li><strong>Aerospace Systems<\/strong> &#8211; Avionics and satellite components demanding weight reduction and shock resistance.<\/li>\n\n\n\n<li><strong>Industrial Robotics <\/strong>&#8211; Articulated arms with repeated motion joints requiring durable yet flexible interconnections.<\/li>\n\n\n\n<li><strong>Consumer Electronics <\/strong>&#8211; Foldable displays and rotating-camera mechanisms necessitating 3D PCB solutions.<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"How_to_Design_a_4-Layer_Rigid_Flex_PCB\"><\/span>How to Design a 4-Layer Rigid Flex PCB?<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>Here are <strong><a href=\"https:\/\/www.bestpcbs.com\/blog\/2025\/08\/4-layer-rigid-flex-pcb-design-manufacturer-fast-delivery\/\" title=\"\">4-layer rigid flex PCB design<\/a><\/strong> guide:<\/p>\n\n\n\n<p><strong>1. Layer Stackup &amp; Material Selection<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Rigid Zones<\/strong>: Use FR4 substrate (1.6mm thickness) for structural integrity.<\/li>\n\n\n\n<li><strong>Flex Zones<\/strong>: Opt for polyimide substrates (e.g., DuPont Pyralux AP\/LF\/FR) with 0.1\u20130.3mm thickness to accommodate dynamic bending.<\/li>\n\n\n\n<li><strong>Copper Type<\/strong>: Rolled Annealed (RA) copper for flex layers to ensure \u2265100,000 bend cycles.<\/li>\n\n\n\n<li><strong>Coverlay<\/strong>: Match coverlay thickness to copper weight (0.5oz Cu \u2192 1mil coverlay; 1oz Cu \u2192 1.5mil coverlay).<\/li>\n<\/ul>\n\n\n\n<p><strong>2. Bend Radius Calculation<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Formula<\/strong>: Minimum bend radius\u00a0<em>R<\/em>=<em>t<\/em>\u00d7<em>K<\/em>, where\u00a0<em>t<\/em>\u00a0= total flex-zone thickness,\u00a0<em>K<\/em>\u00a0= layer-dependent coefficient (single-layer\u00a0<em>K<\/em>=6\u201310; dual-layer\u00a0<em>K<\/em>=10\u201315; four-layer\u00a0<em>K<\/em>=20\u201350).<\/li>\n\n\n\n<li><strong>Example<\/strong>: For a 0.29mm four-layer flex zone, dynamic bend radius must be \u22655.8mm to prevent copper cracking.<\/li>\n<\/ul>\n\n\n\n<p><strong>3. Routing &amp; Impedance Control<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Signal Layer Allocation<\/strong>: Place high-speed signals (e.g., DDR, PCIe) on outer layers (L1\/L4); use inner layers (L2\/L3) for power\/ground planes.<\/li>\n\n\n\n<li><strong>Trace Rules<\/strong>: Follow IPC-2223 standards (e.g., 70\u00b5m trace width\/90\u00b5m spacing for 0.5mm BGA).<\/li>\n\n\n\n<li><strong>Microvias<\/strong>: Use laser-drilled microvias (\u22640.1mm diameter) with copper-filled construction (IPC-4761 Type VII).<\/li>\n<\/ul>\n\n\n\n<p><strong>4. Mechanical &amp; Thermal Design<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Transition Zones<\/strong>: Implement &#8220;key-and-slot&#8221; designs or plastic frames to reduce stress concentration at rigid-flex junctions.<\/li>\n\n\n\n<li><strong>Thermal Management<\/strong>: Use \u22651oz copper in power\/ground planes; add thermal via arrays (spacing \u22641mm) for heat dissipation.<\/li>\n\n\n\n<li><strong>Component Reinforcement<\/strong>: Add stiffeners (Kapton or aluminum, &lt;10mil thickness) under flex-zone components to mitigate soldering stress.<\/li>\n<\/ul>\n\n\n\n<p><strong>5. Manufacturing &amp; Testing Standards<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>IPC Compliance<\/strong>: Meet IPC-6013 Class 3\/A requirements via 100% electrical testing, AOI, and X-ray inspection.<\/li>\n\n\n\n<li><strong>Reliability Tests<\/strong>: Conduct thermal shock (-40\u00b0C to 125\u00b0C), vibration (\u226520G random), and bend cycle (\u22651000 iterations) validations.<\/li>\n<\/ul>\n\n\n\n<figure class=\"wp-block-image size-full\"><a href=\"https:\/\/www.bestpcbs.com\/blog\/wp-content\/uploads\/2025\/08\/2-11.png\"><img decoding=\"async\" src=\"https:\/\/www.bestpcbs.com\/blog\/wp-content\/uploads\/2025\/08\/2-11.png\" alt=\"How to Design a 4-Layer Rigid Flex PCB?\" class=\"wp-image-12032\"\/><\/a><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"How_to_Make_a_4-Layer_Rigid_Flex_PCB\"><\/span>How to Make a 4-Layer Rigid Flex PCB?<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>Below are 4-Layer rigid flex PCB manufacturing processes:<\/p>\n\n\n\n<p><strong>Flexible Circuit (Flex) Processing<\/strong><\/p>\n\n\n\n<p><strong>1. Shearing: <\/strong>Cut raw flex material (e.g., polyimide w\/ copper) to size.<br><strong>2. Drill: <\/strong>Use CNC to drill holes for layers\/connections (4 &#8211; layer flex \u2192 holes for interlayer links).<br><strong>3. PTH: <\/strong>Plate copper inside drilled holes (electro\/electroless plating) for layer connectivity.<br><strong>4. Dry Film Lamination:<\/strong> Apply photosensitive dry film (heat\/pressure) as etching mask.<br><strong>5. Develop:<\/strong> UV &#8211; expose film, wash off unexposed areas.<br><strong>6. Etch: <\/strong>Remove unmasked copper (acid bath) to form traces.<br><strong>7. Strip:<\/strong> Chemically remove remaining dry film.<br><strong>8. AOI: <\/strong>Scan for defects (opens, shorts, wrong trace widths) via automated optical inspection.<\/p>\n\n\n\n<ol class=\"wp-block-list\"><\/ol>\n\n\n\n<ol class=\"wp-block-list\"><\/ol>\n\n\n\n<p><strong>Rigid Circuit (Rigid) Processing<\/strong><\/p>\n\n\n\n<p><strong>1. Shearing:<\/strong> Trim raw rigid material (e.g., FR &#8211; 4) to panel size.<br><strong>2. Drill: <\/strong>CNC &#8211; drill holes for components\/vias.<br><strong>3. Dry Film Lamination: <\/strong>Apply dry film (heat\/pressure) as etching mask.<br><strong>4. Develop: <\/strong>UV &#8211; expose, wash unexposed film.<br><strong>5. Etch: <\/strong>Acid &#8211; etch unmasked copper to create traces.<br><strong>6. Strip:<\/strong> Remove leftover dry film.<br><strong>7. AOI: <\/strong>Check for defects (bad traces, opens\/shorts) with automated optics.<\/p>\n\n\n\n<p><strong>Flex + Rigid Integration<\/strong><\/p>\n\n\n\n<p><strong>1. 2nd Drill: <\/strong>Add holes for final connections (flex &#8211; rigid alignment, new vias).<br><strong>2. De &#8211; Burr: <\/strong>Remove drill burrs (brush\/chemical).<br><strong>3. De &#8211; smear: <\/strong>Clean drill residues from holes (solvent\/plasma).<br><strong>4. PTH:<\/strong> Plate copper in new holes (electro\/electroless) for cross &#8211; layer links.<br><strong>5. DES: <\/strong>Repeat develop\/etch\/strip to shape integrated traces (flex + rigid).<br><strong>6. AOI: <\/strong>Verify no misalignments\/shorts between flex + rigid sections.<br><strong>7. Solder mask:<\/strong> Apply liquid polymer, UV &#8211; expose, develop to protect non &#8211; solder areas.<br><strong>8. Surface Finish:<\/strong> ENIG\/ HASL<br><strong>9. Silkscreen: <\/strong>Print ink (stencils) for labels, part markers.<\/p>\n\n\n\n<ol class=\"wp-block-list\"><\/ol>\n\n\n\n<p><strong>Final Assembly<\/strong><\/p>\n\n\n\n<p><strong>1. 2nd Pressing: <\/strong>Bond stiffeners (if needed) via heat\/pressure.<br><strong>2. Flex + Rigid Align:<\/strong> Use fixtures\/optics to align flex + rigid sections.<br><strong>3. FQC: <\/strong>Final visual\/dimensional check (no misalignments, good solder mask).<br><strong>4. Coverlay: <\/strong>Laminate protective film (polyimide) on flex areas (heat\/pressure).<br><strong>5. 2nd Drill:<\/strong> Add final holes (connectors, mounting).<br><strong>6. Outline Rout: <\/strong>Cut board to final shape (CNC routing\/punching).<br><strong>7. PCB Separate:<\/strong> Split multi &#8211; panel boards (routing\/punching).<br><strong>8. E &#8211; Test: <\/strong>Check for opens\/shorts\/impedance issues.<br><strong>9. Stiffener Attach:<\/strong> Add mechanical supports (if needed) to flex zones.<br><strong>10. Packing: <\/strong>Seal in anti &#8211; static bags\/trays (protect from damage\/ESD).<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><a href=\"https:\/\/www.bestpcbs.com\/blog\/wp-content\/uploads\/2025\/08\/3-18.png\"><img decoding=\"async\" src=\"https:\/\/www.bestpcbs.com\/blog\/wp-content\/uploads\/2025\/08\/3-18.png\" alt=\"How to Make a 4-Layer Rigid Flex PCB?\" class=\"wp-image-12033\"\/><\/a><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Why_Choose_EBest_Circuit_Best_Technology_as_Rigid_Flex_PCB_Manufacturer\"><\/span>Why Choose EBest Circuit (Best Technology) as Rigid Flex PCB Manufacturer?<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>International Certifications:<\/strong> ISO 9001\/UL\/IATF 16949\/RoHS certified, with medical-grade ISO 13485 support.<\/li>\n\n\n\n<li><strong>High-End Technical Capabilities: <\/strong>Supports 32-layer board design with a minimum line\/space width of 0.0762mm, compatible with HDI and high-frequency materials (such as Rogers RO4350B).<\/li>\n\n\n\n<li><strong>High-Quality Materials:<\/strong> The flexible area utilizes DuPont polyimide substrate with rolled copper (\u2265100,000 flex cycles) to ensure durability.<\/li>\n\n\n\n<li><strong>Strict Quality Inspection: <\/strong>100% electrical testing + AOI + X-ray inspection, compliant with IPC-6013 Class 3\/A, with impedance control accuracy of \u00b15%.<\/li>\n\n\n\n<li><strong>24 Hours Rapid Prototyping: <\/strong>Standard orders are completed within 7 days, expedited orders within 3 days, with two free prototype verifications per month.<\/li>\n\n\n\n<li><strong>Flexible Custom Design: <\/strong>Supports 4-layer rigid + 2-layer flex stack-ups, blind and buried vias, metal edges, and other special processes.<\/li>\n\n\n\n<li><strong>Free Technical Support:<\/strong> Design-for-Function (DFM) checks and optimization, with 24\/7 engineer assistance for impedance matching and thermal management.<\/li>\n\n\n\n<li><strong>Cost-effective solution:<\/strong> Tiered pricing for bulk orders (e.g., 6-ply panels at $200\/10), and intelligent panelization reduces material waste by 15-20%.<\/li>\n\n\n\n<li><strong>End-to-End Service: <\/strong>Support rigid-flex PCB prototyping, design, manufacturing, assembly service and help you reduce time and production cost a lot.<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Our_Rigid-Flex_PCB_Capabilities\"><\/span>Our Rigid-Flex PCB Capabilities<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td><strong>Parameter Category<\/strong><\/td><td><strong>Parameter Name<\/strong><\/td><td><strong>Parameter Value<\/strong><\/td><\/tr><tr><td rowspan=\"2\">Flexible Layer Count<\/td><td>Layer Range<\/td><td>1-10 layers<\/td><\/tr><tr><td>Configuration<\/td><td>Bonded or Air Gap<\/td><\/tr><tr><td>Rigid Layer Count<\/td><td>Layer Range<\/td><td>1-40 layers<\/td><\/tr><tr><td>Total Layer Count<\/td><td>Layer Range<\/td><td>2-50 layers<\/td><\/tr><tr><td rowspan=\"3\">Flexible Core Material<\/td><td>Material Type<\/td><td>Polyimide (PI)<\/td><\/tr><tr><td>Thickness Range<\/td><td>0.5 mil to 4 mils<\/td><\/tr><tr><td>Adhesive Construction<\/td><td>Adhesive or Adhesiveless<\/td><\/tr><tr><td rowspan=\"2\">Copper Thickness<\/td><td>Flexible Circuit<\/td><td>1\/3 oz \u2013 2 oz (RA or ED Copper Foil)<\/td><\/tr><tr><td>Rigid Circuit<\/td><td>0.5 oz to 10 oz<\/td><\/tr><tr><td rowspan=\"2\">Coverlay<\/td><td>Material Type<\/td><td>Polyimide (PI)<\/td><\/tr><tr><td>Thickness Range<\/td><td>0.5 mil to 2 mils<\/td><\/tr><tr><td>Stiffener Material<\/td><td>Material Type<\/td><td>Polyimide (PI), FR4, Stainless Steel, Aluminum<\/td><\/tr><tr><td>Rigid Material<\/td><td>Material Type<\/td><td>FR4 (TG 130\/170\/180), Low Flow Prepreg<\/td><\/tr><tr><td>EMI\/RF Shielding<\/td><td>Shielding Film<\/td><td>EMI\/RF Shielding Films<\/td><\/tr><tr><td rowspan=\"2\">Special Via Structures<\/td><td>Blind Vias &amp; Buried Vias<\/td><td>Supported<\/td><\/tr><tr><td>Any Layer Interconnect<\/td><td>Supported<\/td><\/tr><tr><td>Controlled Impedance<\/td><td>Impedance Values<\/td><td>50\u03a9, 90\u03a9, 100\u03a9, 110\u03a9, and Custom Values<\/td><\/tr><tr><td>Surface Finishing<\/td><td>Process Types<\/td><td>ENIG, ENEPIG, Gold Plating, Gold Fingers (3-30\u00b5\u201d Au), Immersion Silver<\/td><\/tr><tr><td>IPC Standard<\/td><td>Certification Levels<\/td><td>IPC 6013 Class II &amp; Class III Available<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"How_Can_I_Get_a_Quote_for_a_4_Layer_Rigid-Flex_PCB\"><\/span>How Can I Get a Quote for a 4 Layer Rigid-Flex PCB?<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p><strong>Essential Documents to Submit for Quotation<\/strong><\/p>\n\n\n\n<p><strong>1. Gerber Files<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Include all layers (L1-L4) in 274X format with drill files.<\/li>\n\n\n\n<li>Specify rigid\/flex zones and bend areas in layer notes.<\/li>\n<\/ul>\n\n\n\n<p><strong>2. Stackup Diagram<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Detail material thickness (e.g., FR4 for rigid, polyimide for flex).<\/li>\n\n\n\n<li>Copper weight (e.g., 1oz inner layers, 0.5oz flex zones).<\/li>\n<\/ul>\n\n\n\n<p><strong>3. Technical Specifications<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Board dimensions (\u00b10.1mm tolerance).<\/li>\n\n\n\n<li>Min. trace\/space (e.g., 4\/4mil for rigid, 5\/5mil for flex).<\/li>\n\n\n\n<li>Surface finish (e.g., ENIG, immersion gold).<\/li>\n<\/ul>\n\n\n\n<p><strong>4. Special Requirements<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Impedance control (e.g., \u00b110% for 50\u03a9 signals).<\/li>\n\n\n\n<li>Stiffener locations (e.g., FR4 at connector areas).<\/li>\n<\/ul>\n\n\n\n<p><strong>5. Quantity &amp; Lead Time<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Prototype (5-10pcs) or bulk order (e.g., 1k pcs\/month).<\/li>\n\n\n\n<li>Urgency (standard 15 days or expedited 7 days).<\/li>\n<\/ul>\n\n\n\n<p>Contact EBest Circuit (Best Technology) with your project details for a competitive quote for rigid-flex PCB needs: <strong><a href=\"mailto:sales@bestpcbs.com\">sales@bestpcbs.com<\/a><\/strong>.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>What is a 4-layer rigid flex PCB? Let&#8217;s explore its stackup, thickness, benefits, applications, design guide and manufacturing processes through this blog. Are you troubled with these issues? EBest Circuit (Best Technology) can provide service: Welcome to contact us if you have any request for rigid flex PCB: sales@bestpcbs.com. What Is a 4-Layer Rigid Flex [&hellip;]<\/p>\n","protected":false},"author":33247,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_uf_show_specific_survey":0,"_uf_disable_surveys":false,"footnotes":""},"categories":[175,174,164,165],"tags":[2005,2004],"class_list":["post-12027","post","type-post","status-publish","format-standard","hentry","category-best-pcb","category-bestpcb","category-design-guide","category-fr4-pcb","tag-4-layer-rigid-flex-pcb-2","tag-4-layer-rigid-flex-pcb"],"acf":[],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/www.bestpcbs.com\/blog\/wp-json\/wp\/v2\/posts\/12027","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.bestpcbs.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.bestpcbs.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.bestpcbs.com\/blog\/wp-json\/wp\/v2\/users\/33247"}],"replies":[{"embeddable":true,"href":"https:\/\/www.bestpcbs.com\/blog\/wp-json\/wp\/v2\/comments?post=12027"}],"version-history":[{"count":5,"href":"https:\/\/www.bestpcbs.com\/blog\/wp-json\/wp\/v2\/posts\/12027\/revisions"}],"predecessor-version":[{"id":12042,"href":"https:\/\/www.bestpcbs.com\/blog\/wp-json\/wp\/v2\/posts\/12027\/revisions\/12042"}],"wp:attachment":[{"href":"https:\/\/www.bestpcbs.com\/blog\/wp-json\/wp\/v2\/media?parent=12027"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.bestpcbs.com\/blog\/wp-json\/wp\/v2\/categories?post=12027"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.bestpcbs.com\/blog\/wp-json\/wp\/v2\/tags?post=12027"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}