{"id":1154,"date":"2025-09-27T00:09:20","date_gmt":"2025-09-26T16:09:20","guid":{"rendered":"https:\/\/ulpcb.com\/?page_id=1154"},"modified":"2025-09-27T00:11:17","modified_gmt":"2025-09-26T16:11:17","slug":"flex-rigid-pcb","status":"publish","type":"page","link":"https:\/\/ulpcb.com\/as\/flex-rigid-pcb\/","title":{"rendered":"Flex &#8211; rigid PCB"},"content":{"rendered":"<div data-elementor-type=\"wp-page\" data-elementor-id=\"1154\" class=\"elementor elementor-1154\">\n\t\t\t\t<div class=\"wd-negative-gap elementor-element elementor-element-34b6d6ae e-flex e-con-boxed e-con e-parent\" data-id=\"34b6d6ae\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-6f24d31f wd-el-breadcrumbs text-left elementor-widget elementor-widget-wd_element_breadcrumbs\" data-id=\"6f24d31f\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"wd_element_breadcrumbs.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<nav class=\"wd-breadcrumbs\"><a href=\"https:\/\/ulpcb.com\/as\/\">Home<\/a><span class=\"wd-delimiter\"><\/span><span class=\"wd-last\">\u09aa\u09c3\u09b7\u09cd\u09a0\u09be <\/span><\/nav>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"wd-negative-gap elementor-element elementor-element-79896fd0 e-flex e-con-boxed e-con e-parent\" data-id=\"79896fd0\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t<div class=\"elementor-element elementor-element-3c2fb350 e-con-full e-flex e-con e-child\" data-id=\"3c2fb350\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t<div class=\"elementor-element elementor-element-591a2b4f wd-width-100 elementor-widget elementor-widget-wd_images_gallery\" data-id=\"591a2b4f\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"wd_images_gallery.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<div class=\"wd-images-gallery photoswipe-images wd-carousel-container\" style=\"--wd-align-items:center; --wd-justify-content:center;\">\n\t\t\t\t\t\t\t<div class=\"wd-carousel-inner\">\n\t\t\t\t\t\t<div class=\"wd-carousel wd-grid\" data-wrap=\"yes\" style=\"--wd-col-lg:1;--wd-col-md:1;--wd-col-sm:1;--wd-gap-lg:0px;\">\n\t\t\t\t\t\t\t\t\t<div class=\"wd-carousel-wrap\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<div class=\"wd-gallery-item wd-carousel-item\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t<a  href=\"https:\/\/ulpcb.com\/wp-content\/uploads\/2025\/09\/4-layer-Flex-rigid-PCB-1.webp\" data-width=\"500\" data-height=\"500\" data-index=\"1\" data-elementor-open-lightbox=\"no\">\n\t\t\t\t\t\t\n\t\t\t\t\t\t<img fetchpriority=\"high\" decoding=\"async\" width=\"400\" height=\"400\" src=\"https:\/\/ulpcb.com\/wp-content\/uploads\/2025\/09\/4-layer-Flex-rigid-PCB-1.webp\" class=\"attachment-600x400 size-600x400\" alt=\"The 4 - layer rigid - flex PCB is a medium - to - high - end category widely used among rigid - flex PCBs. Its core feature is the alternating combination of &quot;2 - 3 layers of rigid substrates + 1 - 2 layers of flexible substrates&quot;, along with the use of metallized vias to achieve inter - layer interconnection. This not only retains the mechanical support and high - density wiring capabilities of rigid boards\" srcset=\"https:\/\/ulpcb.com\/wp-content\/uploads\/2025\/09\/4-layer-Flex-rigid-PCB-1.webp 500w, https:\/\/ulpcb.com\/wp-content\/uploads\/2025\/09\/4-layer-Flex-rigid-PCB-1-300x300.webp 300w, https:\/\/ulpcb.com\/wp-content\/uploads\/2025\/09\/4-layer-Flex-rigid-PCB-1-150x150.webp 150w, https:\/\/ulpcb.com\/wp-content\/uploads\/2025\/09\/4-layer-Flex-rigid-PCB-1-12x12.webp 12w\" sizes=\"(max-width: 400px) 100vw, 400px\" \/>\n\t\t\t\t\t\t\t\t\t\t\t\t\t<\/a>\n\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t<div class=\"wd-nav-arrows wd-pos-sep wd-hover-1 wd-icon-1\">\n\t\t\t<div class=\"wd-btn-arrow wd-prev wd-disabled\">\n\t\t\t\t<div class=\"wd-arrow-inner\"><\/div>\n\t\t\t<\/div>\n\t\t\t<div class=\"wd-btn-arrow wd-next\">\n\t\t\t\t<div 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the flexible layers through \"blind vias\", avoiding through - holes passing through the flexible areas and affecting bending.<\/h2>\n\t\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-2506424f e-con-full e-flex e-con e-child\" data-id=\"2506424f\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t<div class=\"elementor-element elementor-element-2e0cdc9 elementor-widget elementor-widget-wd_popup\" data-id=\"2e0cdc9\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"wd_popup.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<div class=\"wd-button-wrapper text-left\" >\n\t\t\t<a class=\"btn btn-style-default btn-shape-rectangle btn-size-default wd-open-popup btn-color-primary btn-icon-pos-right\"  href=\"#quote\">\n\t\t\t\t<span class=\"wd-btn-text\" data-elementor-setting-key=\"text\">\n\t\t\t\t\tGet a Quote\t\t\t\t<\/span>\n\n\t\t\t\t\t\t\t\t\t<span 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Enter ve Space ile \u00f6geleri a\u00e7abilir, Escape ile \u00f6geleri kapatabilir ve Y\u00f6n tu\u015flar\u0131 ile \u00f6geler aras\u0131nda gezinebilirsiniz.\" data-no-translation-aria-label=\"\">\n\t\t\t<div class=\"e-n-tabs-heading\" role=\"tablist\">\n\t\t\t\t\t<button id=\"e-n-tab-title-8731776721\" data-tab-title-id=\"e-n-tab-title-8731776721\" class=\"e-n-tab-title\" aria-selected=\"true\" data-tab-index=\"1\" role=\"tab\" tabindex=\"0\" aria-controls=\"e-n-tab-content-8731776721\" style=\"--n-tabs-title-order: 1;\">\n\t\t\t\t\t\t<span class=\"e-n-tab-title-text\">\n\t\t\t\tDescription\t\t\t<\/span>\n\t\t<\/button>\n\t\t\t\t\t<\/div>\n\t\t\t<div class=\"e-n-tabs-content\">\n\t\t\t\t<div id=\"e-n-tab-content-8731776721\" role=\"tabpanel\" aria-labelledby=\"e-n-tab-title-8731776721\" data-tab-index=\"1\" style=\"--n-tabs-title-order: 1;\" class=\"e-active elementor-element elementor-element-1529d092 e-con-full e-flex e-con e-child\" data-id=\"1529d092\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t<div class=\"wd-negative-gap elementor-element elementor-element-3ce6a09d e-flex e-con-boxed e-con e-child\" data-id=\"3ce6a09d\" data-element_type=\"container\" data-e-type=\"container\" data-settings=\"{&quot;background_background&quot;:&quot;classic&quot;}\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-414c3e37 elementor-widget elementor-widget-wd_text_block\" data-id=\"414c3e37\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"wd_text_block.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<div class=\"wd-text-block reset-last-child text-left\">\n\t\t\t\n\t\t\t<h3 class=\"header-vfC6AV auto-hide-last-sibling-br\">I. Core Structural Framework of 4 - layer Rigid - Flex PCB<\/h3><div class=\"auto-hide-last-sibling-br paragraph-JOTKXA paragraph-element br-paragraph-space\">The structural design of a 4 - layer rigid - flex PCB needs to balance the \"stability of the rigid areas\" and the \"bendability of the flexible areas\". The typical structure takes \"rigid area - transition area - flexible area - transition area - rigid area\" as the overall framework, and each area realizes functional differentiation through specific layer - stacking combinations. According to the number and position of flexible substrates, the mainstream 4 - layer stacking schemes can be divided into two types: the \"2 rigid + 1 flexible\" symmetrical structure and the \"2 rigid + 2 flexible\" composite structure. The specific layer - stacking breakdown is as follows:<\/div><h4 class=\"header-vfC6AV auto-hide-last-sibling-br\">(1) Main Stacking Scheme 1: \"2 rigid + 1 flexible\" Symmetrical Structure (Most Commonly Used)<\/h4><div class=\"auto-hide-last-sibling-br paragraph-JOTKXA paragraph-element br-paragraph-space\">This scheme takes \"rigid substrate + flexible substrate + rigid substrate\" as the symmetrical core, with the flexible area in the middle and the rigid areas on both sides symmetrically distributed. It takes into account both structural stability and bending reliability, and is suitable for scenarios where \"both ends are fixed and the middle is bent\" (such as the hinge circuit of a foldable - screen mobile phone). The specific layer - stacking (from the top layer to the bottom layer) is as follows:<\/div><div class=\"container-utlnW2 md-box-line-break wrapper-d0Cc1k undefined\">\u00a0<\/div><div class=\"auto-hide-last-sibling-br mdbox-table-root table-container-GhL7Lo\" data-scroll-inline-overflow=\"true\" data-scroll-inline-at-start=\"true\" data-scroll-inline-start-overflow=\"false\" data-scroll-inline-at-end=\"false\" data-scroll-inline-end-overflow=\"true\"><div class=\"table-scroll-container-hgHkfW mdbox-table-scroll-container\"><table><thead><tr><th>Layer Number<\/th><th>Area Attribute<\/th><th>Material \/ Structure Type<\/th><th>Thickness Range<\/th><th>Core Function<\/th><\/tr><\/thead><tbody><tr><td>1<\/td><td>Top - layer Rigid Area<\/td><td>Rigid substrate (FR - 4) + copper - foil circuit<\/td><td>Substrate: 0.2 - 0.4mm<div class=\"container-utlnW2 md-box-line-break wrapper-d0Cc1k undefined\">\u00a0<\/div>Copper foil: 1oz (35\u03bcm)<\/td><td>\u2460 Bears top - layer components (such as chips, connectors) and provides mechanical support. \u2461 Arranges high - frequency \/ high - power circuits to ensure signal integrity.<\/td><\/tr><tr><td>2<\/td><td>Transition Area \u2192 Flexible Area<\/td><td>Flexible substrate (PI polyimide) + copper - foil circuit<\/td><td>Substrate: 0.025 - 0.05mm<div class=\"container-utlnW2 md-box-line-break wrapper-d0Cc1k undefined\">\u00a0<\/div>Copper foil: 0.5oz (18\u03bcm)<\/td><td>\u2460 Core of the flexible area: Enables the bending transmission of circuits. The PI substrate can withstand more than 100,000 bending times (180\u00b0 bending). \u2461 Transition area: Reduces stress concentration through a gradually changing thickness (from rigid substrate to prepreg to flexible substrate), avoiding inter - layer cracking during bending.<\/td><\/tr><tr><td>3<\/td><td>Bottom - layer Rigid Area<\/td><td>Rigid substrate (FR - 4) + copper - foil circuit<\/td><td>Substrate: 0.2 - 0.4mm<div class=\"container-utlnW2 md-box-line-break wrapper-d0Cc1k undefined\">\u00a0<\/div>Copper foil: 1oz (35\u03bcm)<\/td><td>\u2460 Bears bottom - layer components (such as resistors, capacitors), forming a symmetrical support with the top - layer rigid area. \u2461 Arranges power \/ ground circuits, forming a \"signal - ground\" reference structure with the top - layer signal circuits to reduce interference.<\/td><\/tr><tr><td>4<\/td><td>Inter - layer Connection<\/td><td>Metallized vias (through - holes \/ blind vias) + prepreg (PP)<\/td><td>Via diameter: 0.1 - 0.2mm<div class=\"container-utlnW2 md-box-line-break wrapper-d0Cc1k undefined\">\u00a0<\/div>Prepreg: 0.05 - 0.1mm<\/td><td>\u2460 Metallized vias: Realize the electrical connection of the 4 - layer circuits (through - holes penetrate the entire board, and blind vias connect the surface layer of the rigid area and the inner layer of the flexible area). \u2461 Prepreg: Only used in the rigid area and the transition area to bond the rigid substrate and the flexible substrate. There is no prepreg in the flexible area (to avoid affecting bending).<\/td><\/tr><\/tbody><\/table><\/div><\/div><div class=\"container-utlnW2 md-box-line-break wrapper-d0Cc1k undefined\">\u00a0<\/div><div class=\"auto-hide-last-sibling-br paragraph-JOTKXA paragraph-element br-paragraph-space\">Key design details: The flexible area only retains \"PI substrate + copper - foil circuit\", without a rigid substrate and prepreg. The copper - foil circuit adopts an \"arc - corner\" design (to avoid stress concentration at right - angles). The prepreg in the transition area should be a \"low - fluidity resin\" to prevent resin from overflowing into the flexible area during lamination, affecting the bending performance.<\/div><h4 class=\"header-vfC6AV auto-hide-last-sibling-br\">(2) Main Stacking Scheme 2: \"2 rigid + 2 flexible\" Composite Structure (for High - integration Requirements)<\/h4><div class=\"auto-hide-last-sibling-br paragraph-JOTKXA paragraph-element br-paragraph-space\">Based on the \"2 rigid + 1 flexible\" structure, this scheme adds one more flexible substrate, forming a composite structure of \"rigid area - flexible area - rigid sub - layer - flexible area - rigid area\". It is suitable for scenarios with \"multiple - area bending and high - circuit density\" (such as the multi - joint circuits of minimally invasive medical devices), and can achieve \"independent layout of 4 - layer circuits + multi - direction bending\". The specific layer - stacking features are as follows:<\/div><div class=\"container-utlnW2 md-box-line-break wrapper-d0Cc1k undefined\">\u00a0<\/div><ul class=\"auto-hide-last-sibling-br\"><li><strong>Flexible Layers<\/strong>: Comprise 2 independent PI substrates (both with a thickness of 0.025mm), located respectively between the \"top - layer rigid area and the middle rigid sub - layer\" and between the \"middle rigid sub - layer and the bottom - layer rigid area\", forming two independent bending regions.<\/li><li><strong>Middle Rigid Sub - layer<\/strong>: Utilizes an ultra - thin FR - 4 substrate (with a thickness of 0.1 - 0.2mm), which is only used to separate the two flexible substrates and arrange the middle - layer circuits (such as the ground layer and shielding layer), without undertaking the main support function.<\/li><li><strong>Interconnection Method<\/strong>: Connects the middle rigid sub - layer and the flexible layers through \"buried vias\", and connects the surface - layer rigid areas and the flexible layers through \"blind vias\", avoiding through - holes passing through the flexible areas and affecting bending.<\/li><\/ul><h3 class=\"header-vfC6AV auto-hide-last-sibling-br\">II. Core Structural Components: Coordination and Adaptation of Materials and Processes<\/h3><div class=\"auto-hide-last-sibling-br paragraph-JOTKXA paragraph-element br-paragraph-space\">The structural reliability of a 4 - layer rigid - flex PCB depends on the coordination of \"special materials + precise processes\". The core components include flexible substrates, rigid substrates, inter - layer bonding materials, and metallized vias. The selection and design of each component directly determine the product performance:<\/div><h4 class=\"header-vfC6AV auto-hide-last-sibling-br\">(1) Flexible Substrate (Core of Bendability)<\/h4><ul class=\"auto-hide-last-sibling-br\"><li><strong>Core Material<\/strong>: The mainstream is the PI (polyimide) substrate, which has high - temperature resistance (long - term use temperature from - 269\u2103 to 280\u2103) and good bendability (more than 100,000 bending times at 180\u00b0). In some high - end scenarios, the PEN (polyethylene naphthalate) substrate is used (lower cost, slightly inferior to PI in terms of bendability).<\/li><li><strong>Thickness Control<\/strong>: The thickness of the flexible substrate is usually 0.025 - 0.05mm (about 1\/10 of that of a common FR - 4 substrate). If it is too thick, it will reduce bending flexibility; if too thin, it will affect the circuit - bearing capacity.<\/li><li><strong>Circuit Design<\/strong>: \"Rolled copper foil\" is selected for the copper foil (better ductility than electrolytic copper foil, less likely to break during bending). The line width and line spacing should be \u22650.05mm\/0.05mm (to avoid fine - line breakage during bending), and large - volume components (such as resistors with a package of \u22650402) are prohibited from being arranged in the flexible area.<\/li><\/ul><h4 class=\"header-vfC6AV auto-hide-last-sibling-br\">(2) Rigid Substrate (Core of Mechanical Support)<\/h4><ul class=\"auto-hide-last-sibling-br\"><li><strong>Core Material<\/strong>: Select a high - Tg (glass - transition temperature \u2265170\u2103) FR - 4 substrate to ensure that the rigid area does not deform during soldering (such as 260\u2103 reflow soldering) and use.<\/li><li><strong>Thickness Adaptation<\/strong>: The thickness of the rigid substrate is designed according to the support requirements, usually 0.2 - 0.4mm (single piece). If it needs to bear heavy components (such as camera modules), 2 layers of FR - 4 substrates can be stacked (total thickness 0.4 - 0.8mm).<\/li><li><strong>Component Layout<\/strong>: All large - volume and high - weight components (such as connectors, chips) should be arranged in the rigid area, and the distance from the transition area should be \u22652mm (to avoid stress concentration in the transition area caused by the weight of the components).<\/li><\/ul><h4 class=\"header-vfC6AV auto-hide-last-sibling-br\">(3) Inter - layer Bonding Material (Core of Structural Stability)<\/h4><ul class=\"auto-hide-last-sibling-br\"><li><strong>Bonding in Rigid Areas<\/strong>: Use a conventional prepreg (PP, with the same resin composition as FR - 4), with a thickness of 0.05 - 0.1mm to ensure firm bonding between rigid layers without bubbles or delamination.<\/li><li><strong>Bonding in Transition Areas<\/strong>: Use a \"low - fluidity prepreg\" (such as Panasonic R - 1515) with a resin fluidity of \u226415% to prevent resin from overflowing into the flexible area during lamination, affecting bending.<\/li><li><strong>Treatment in Flexible Areas<\/strong>: No prepreg is used in the flexible area. The inter - layer stability is maintained only by the self - bonding force between the copper foil and the PI substrate. Some high - end products will cover a \"PI cover film\" (with a thickness of 0.025mm) on the surface of the flexible area to enhance circuit protection.<\/li><\/ul><h4 class=\"header-vfC6AV auto-hide-last-sibling-br\">(4) Metallized Vias (Core of Inter - layer Interconnection)<\/h4><ul class=\"auto-hide-last-sibling-br\"><li><strong>Via Type Selection<\/strong>: \"Through - holes\" can be used in the rigid area (penetrating the entire board to connect all layers), while \"blind vias \/ buried vias\" must be used in the transition area and the flexible area (to avoid the breakage of the metallized via walls of through - holes during bending).<\/li><li><strong>Via - wall Treatment<\/strong>: For blind vias in the flexible area, the \"laser drilling + electroless copper plating\" process should be adopted. The thickness of the copper layer on the via wall should be \u226515\u03bcm (to ensure reliable conductivity), and the roughness of the via wall should be \u22641.5\u03bcm (to reduce stress concentration during bending).<\/li><li><strong>Via - diameter Control<\/strong>: The diameter of blind vias in the flexible area should be \u22640.2mm (if the via diameter is too large, the PI substrate is likely to crack during bending), and the diameter of through - holes in the rigid area can be relaxed to 0.3mm (to fit the pins of connectors).<\/li><\/ul><h3 class=\"header-vfC6AV auto-hide-last-sibling-br\">III. Key Principles of Structural Design (Avoiding Common Failures)<\/h3><div class=\"auto-hide-last-sibling-br paragraph-JOTKXA paragraph-element br-paragraph-space\">The structural design of a 4 - layer rigid - flex PCB needs to avoid three major risks: \"bending fracture, inter - layer delamination, and signal interference\". The core principles include:<\/div><h4 class=\"header-vfC6AV auto-hide-last-sibling-br\">(1) Design Principles for Flexible and Transition Areas<\/h4><ul class=\"auto-hide-last-sibling-br\"><li><strong>Bending Radius Control<\/strong>: The minimum bending radius of the flexible area should be \u22653 times the total thickness of the flexible area (for example, if the total thickness of the flexible area is 0.1mm, the minimum bending radius should be \u22650.3mm) to avoid excessive bending causing circuit breakage.<\/li><li><strong>Transition - area Length Design<\/strong>: The length of the transition area (from the rigid area to the flexible area) should be \u22655mm, and a \"gradually changing thickness\" design should be adopted (gradually changing from 0.4mm in the rigid area to 0.05mm in the flexible area) to reduce stress concentration.<\/li><li><strong>Prohibition of Cross - area Wiring<\/strong>: When a circuit enters the flexible area from the rigid area, \"line - width transition\" should be completed in the transition area (line width in the rigid area is 0.1mm \u2192 gradually changes to 0.05mm in the transition area \u2192 line width in the flexible area is 0.05mm). It is prohibited for the line width to suddenly change (become wider or narrower) in the flexible area.<\/li><\/ul><h4 class=\"header-vfC6AV auto-hide-last-sibling-br\">(2) Principles of Inter - layer Symmetry and Balance<\/h4><ul class=\"auto-hide-last-sibling-br\"><li><strong>Symmetrical Design of Rigid Areas<\/strong>: The thickness of the substrates and copper foils in the top - layer and bottom - layer rigid areas should be exactly the same (for example, the top - layer is FR - 4 0.3mm + 1oz copper, and the bottom - layer has the same specification) to avoid warping of the rigid area due to uneven stress after lamination.<\/li><li><strong>Circuit Balance in Flexible Areas<\/strong>: The upper and lower - layer circuits in the flexible area should be symmetrically arranged (for example, if 2 signal lines are arranged on the top - layer, 2 ground lines should be arranged at the corresponding position on the bottom - layer) to avoid the offset of the flexible area during bending due to uneven circuit distribution.<\/li><\/ul><h4 class=\"header-vfC6AV auto-hide-last-sibling-br\">(3) Principles of Signal and Power Isolation<\/h4><ul class=\"auto-hide-last-sibling-br\"><li><strong>Zoning Layout<\/strong>: In the rigid area, \"high - frequency signal circuits\" (such as USB 3.0, MIPI) and \"high - power power circuits\" (such as 5V\/2A) should be arranged on different layers (for example, signals on the top - layer and power on the bottom - layer), separated by a ground layer in the middle.<\/li><li><strong>Shielding in Flexible Areas<\/strong>: If high - frequency signals need to be transmitted in the flexible area (such as the display signal of a foldable - screen mobile phone), a \"ground copper - foil layer\" can be added in the flexible area (located between two layers of signal lines) to form a \"signal - ground - signal\" shielding structure, reducing signal interference during bending.<\/li><\/ul>\n\t\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-19215c0b elementor-widget elementor-widget-wd_image_or_svg\" data-id=\"19215c0b\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"wd_image_or_svg.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\n\t\t<div class=\"wd-image text-left\">\n\t\t\t\t\t\t\t\t<img decoding=\"async\" width=\"500\" height=\"500\" src=\"https:\/\/ulpcb.com\/wp-content\/uploads\/2025\/09\/4-layer-Flex-rigid-PCB-1.webp\" class=\"attachment-full size-full\" alt=\"The 4 - layer rigid - flex PCB is a medium - to - high - end category widely used among rigid - flex PCBs. Its core feature is the alternating combination of &quot;2 - 3 layers of rigid substrates + 1 - 2 layers of flexible substrates&quot;, along with the use of metallized vias to achieve inter - layer interconnection. This not only retains the mechanical support and high - density wiring capabilities of rigid boards\" srcset=\"https:\/\/ulpcb.com\/wp-content\/uploads\/2025\/09\/4-layer-Flex-rigid-PCB-1.webp 500w, https:\/\/ulpcb.com\/wp-content\/uploads\/2025\/09\/4-layer-Flex-rigid-PCB-1-300x300.webp 300w, https:\/\/ulpcb.com\/wp-content\/uploads\/2025\/09\/4-layer-Flex-rigid-PCB-1-150x150.webp 150w, https:\/\/ulpcb.com\/wp-content\/uploads\/2025\/09\/4-layer-Flex-rigid-PCB-1-12x12.webp 12w\" sizes=\"(max-width: 500px) 100vw, 500px\" \/>\t\t\t\t\t<\/div>\n\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>","protected":false},"excerpt":{"rendered":"<p>Home\u9875\u9762 4 layer Flex \u2013 rigid PCB Flexible Layers: Comprise 2 independent PI substrates (both with a thickness of 0.025mm),<\/p>","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-1154","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/ulpcb.com\/as\/wp-json\/wp\/v2\/pages\/1154","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ulpcb.com\/as\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/ulpcb.com\/as\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/ulpcb.com\/as\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/ulpcb.com\/as\/wp-json\/wp\/v2\/comments?post=1154"}],"version-history":[{"count":3,"href":"https:\/\/ulpcb.com\/as\/wp-json\/wp\/v2\/pages\/1154\/revisions"}],"predecessor-version":[{"id":1159,"href":"https:\/\/ulpcb.com\/as\/wp-json\/wp\/v2\/pages\/1154\/revisions\/1159"}],"wp:attachment":[{"href":"https:\/\/ulpcb.com\/as\/wp-json\/wp\/v2\/media?parent=1154"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}