1. Design codes and core challenges
\nBlind Buried Hole Design Rules
\nHole diameter and depth-to-diameter ratio:
\nBlind hole: laser drilled hole diameter \u2265 0.1mm, depth-to-diameter ratio \u2264 1:1 (e.g. 0.1mm hole diameter \/ 0.1mm depth).
\nBuried hole: mechanically drilled hole diameter \u2265 0.2mm, depth-to-diameter ratio \u2264 10:1 (e.g. 0.3mm hole diameter corresponds to 3mm laminate thickness).
\nSpacing requirements:
\nHole edge to wire spacing \u2265 0.15mm, spacing between holes \u2265 0.2mm, to avoid plating short circuit.
\nImpedance control:
\nThe capacitance introduced by blind holes needs to be compensated by simulation (e.g. HFSS optimization) to ensure impedance tolerance \u00b18%.
\nLamination optimization strategy
\nSequential lamination method:
\nLayer by layer lamination (e.g., L2-L5, then L1 and L6-L8) to reduce interlayer stress.
\nStacked Via vs. Staggered Via:
\nStacked Via saves space but increases process difficulty; Staggered Via improves reliability but occupies more area.<\/p>\n
2. Material selection and process key points
\nSubstrate Material Requirements
\nHigh Tg material: Tg\u2265170\u2103 (e.g. Isola FR408HR), able to withstand high temperature (180~200\u2103) for multiple pressing.
\nLow CTE matching: Z-axis CTE \u2264 50 ppm\/\u00b0C to prevent hole copper fracture after lamination (e.g. Panasonic MEGTRON6).
\nCore process steps
\nLaser drilling:
\nCO2 laser (for non-metallic materials) or UV laser (metal + medium), accuracy \u00b115\u03bcm.
\nHole wall roughness Ra <1\u03bcm, plasma cleaning required to remove carbonized residues.
\nElectroplated hole filling:
\nBlind holes are filled with copper (conductive paste) or resin plugged holes, surface flatness \uff1c10\u03bcm.
\nBuried holes need to be plated before lamination to ensure that the copper thickness in the holes is \u226520\u03bcm.
\nLamination alignment:
\nUse X-ray alignment system, interlayer offset \u226425\u03bcm, to avoid blind hole misalignment leading to open circuit.<\/p>\n
3. Typical application scenarios and design cases
\nSmartphone motherboard (10-layer arbitrary layer HDI)
\nBlind holes: L1-L2 and L9-L10, hole diameter 0.1mm, copper filling to ensure flatness.
\nBuried holes: L3-L8 interlayer buried holes, hole diameter 0.2mm, staggered to reduce crosstalk.
\nHigh-speed server CPU slots
\nBlind vias: L1-L3 short stubs (Stub <0.1mm) to reduce signal reflection.
\nBuried hole: L4-L6 interlayer differential pair hopping, hole spacing 0.3mm, impedance 100\u03a9\u00b15%.<\/p>","protected":false},"excerpt":{"rendered":"
1.Smartphone motherboard (10-layer arbitrary layer HDI)
\n2.High-speed server CPU slots<\/p>","protected":false},"featured_media":1134,"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-1133","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