1. Basic structure and typical applications
\nRange of layers
\nUsually 4~12 layers (higher layers can be more than 20 layers), through the lamination process to realize the alternating stack of insulating layers and conductive layers.
\nExample: The common structure of 6-layer board is Signal-GND-Power-Signal-GND-Signal.
\nTypical Application Scenarios
\nLow to medium speed digital circuits (e.g., industrial control motherboards, power supply modules);
\nAnalog signal processing (such as audio amplifiers);
\nGeneral consumer electronics (such as home appliance control boards, routers).<\/p>\n
2. Material Characteristics Requirements
\nSubstrate selection
\nFR-4 epoxy glass cloth: mainstream material, low cost, suitable for most scenarios (Tg=130~140\u2103).
\nHigh-frequency scenario: optional low-loss material (e.g. Isola 370HR, Dk=4.0, Df=0.02@1GHz).
\nCopper Foil Thickness
\nThe outer layer is usually 1oz (35\u03bcm), the inner layer is 0.5~1oz, and can be locally thickened to 2oz for high current path.
\n3. Design Specifications and Process Requirements
\nLine design
\nLine width\/spacing: 5~8mil (125~200\u03bcm) for conventional design, can be reduced to 3mil (75\u03bcm) for high precision.
\nImpedance control: \u00b110% tolerance (e.g. 50\u03a9 single-ended, 100\u03a9 differential) to be realized by stacking design.
\nDrilling and Hole Metallization
\nMechanical drilling: hole diameter \u2265 0.3mm (12mil), depth to diameter ratio of \u2264 10:1 (e.g. 0.3mm hole diameter corresponds to 3mm plate thickness).
\nCopper plating thickness: hole wall copper thickness \u226520\u03bcm, to ensure mechanical strength and electrical conductivity.
\nInterlayer alignment: Interlayer offset \u2264 50\u03bcm (to be calibrated by optical positioning system).
\n4. Key process steps
\nLamination process
\nAlternate stacking of prepreg and copper foil, high temperature and high pressure curing (180~200\u2103).
\nThickness tolerance (\u00b110%) after lamination needs to be controlled.
\nSurface treatment
\nSpray tin (HASL): low cost, but poor flatness, suitable for large pitch components.
\nImmersion gold (ENIG): high flatness, suitable for BGA \/ SMD welding, but need to prevent \u201cblack disk\u201d problem.
\nOSP (organic protective film): low-cost program for short storage cycles.
\n5. Reliability test standards
\nThermal Reliability
\nThermal cycle test (-40\u2103~125\u2103, no delamination after 500 cycles).
\nSoldering heat resistance test (260\u00b0C, 10 seconds, no blistering after 3 cycles).
\nMechanical Reliability
\nPeel strength test (\u22651.0N\/mm, IPC-TM-650 2.4.8)
\nVibration test (e.g. 20G RMS, 3 axes, 2 hours per axis without failure).<\/p>","protected":false},"excerpt":{"rendered":"
1.Low to medium speed digital circuits (e.g., industrial control motherboards, power supply modules);
\n2.Analog signal processing (such as audio amplifiers);
\n3.General consumer electronics (such as home appliance control boards, routers).<\/p>","protected":false},"featured_media":1124,"comment_status":"open","ping_status":"closed","template":"","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","theme-transparent-header-meta":"default","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"set","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""}}},"product_brand":[],"product_cat":[45],"product_tag":[],"class_list":{"0":"post-1123","1":"product","2":"type-product","3":"status-publish","4":"has-post-thumbnail","6":"product_cat-pcb","7":"desktop-align-left","8":"tablet-align-left","9":"mobile-align-left","11":"first","12":"instock","13":"shipping-taxable","14":"product-type-simple"},"yoast_head":"\n