Core requirements for material selection
\nLow dielectric constant (Dk) with low loss factor (Df)
\nKey parameters:
\nDk stability: Dk fluctuations need to be small as frequency increases (e.g. Rogers RO4350B Dk=3.48\u00b10.05 over 1~40 GHz).
\nExtremely low Df: Df \u2264 0.003@10 GHz (e.g. Taconic Taconic RF-35, Df=0.0018@10 GHz).
\nTypical materials:
\nPTFE base material (polytetrafluoroethylene): Dk=2.1~2.5 for millimeter wave (e.g. 28GHz 5G antenna).
\nCeramic filler material (e.g. Rogers RO4003C): Dk=3.38, Df=0.0027, balancing cost and performance.
\nModified FR-4 (e.g. Isola I-Tera MT40): Dk=3.45, compatible with conventional FR-4 process.
\nThermal stability matched to CTE
\nGlass transition temperature (Tg): \u2265180\u00b0C (e.g. Arlon 25N, Tg=220\u00b0C), compatible with lead-free soldering.
\nCoefficient of Thermal Expansion (CTE): Z-axis CTE \u2264 30 ppm\/\u00b0C, reducing interlayer separation due to temperature cycling.
\n2. Key Process Challenges and Solutions
\nFine Line Processing
\nLine width\/spacing: \u22643 mil (75 \u03bcm) with mSAP (semi-additive method) process to minimize side etching.
\nCopper foil roughness: ultra-low profile copper (HVLP copper, Ra \u2264 1.5\u03bcm), reduced skinning loss (skinning depth \u03b4 \u2248 1.3\u03bcm@10GHz).
\nDrilling and Hole Metallization
\nLaser drilling: for blind holes (hole diameter \u2264 100\u03bcm), depth to diameter ratio \u2264 0.8:1 (e.g. 0.1mm hole diameter \/ 0.08mm depth).
\nPlating to fill holes: copper thickness in holes \u226525\u03bcm, hole resistance <1m\u03a9, using pulse plating to enhance uniformity.
\nSurface treatment
\nChemical nickel-palladium gold plating (ENEPIG): thickness Ni \u2265 3\u03bcm, Au \u2248 0.05\u03bcm, suitable for high-frequency welding and oxidation resistance.
\nImmersion Silver: low-cost solution, anti-sulfide corrosion (storage time <6 months).<\/p>\n
3. Typical application scenarios and design cases
\n5G millimeter wave antenna module
\nRequirements: 28GHz band, 2GHz bandwidth, insertion loss <1dB\/cm.
\nDesign:
\nMaterial: Rogers RO3003 (Dk=3.0, Df=0.0013@28GHz).
\nTransmission line: coplanar waveguide (line width 0.15mm, spacing 0.1mm), ground crossing spacing 0.5mm.
\nAntenna array: 4\u00d74 patch antenna, feed line impedance 50\u03a9, radiation efficiency >80% optimized by simulation.
\nSatellite communication RF front-end
\nRequirements: Ka-band (26.5~40GHz), extreme temperature resistance (-55\u2103~+125\u2103).
\nDesign:
\nMaterial: PTFE substrate (Dk=2.2, CTE=16 ppm\/\u00b0C).
\nLayer structure: 6-layer hybrid dielectric (HF layer + power layer), blind hole connection to reduce parasitic inductance.
\nHeat dissipation: embedded copper-tungsten alloy heat sink block (thermal conductivity 180 W\/m-K), connected to housing heat sink.<\/p>","protected":false},"excerpt":{"rendered":"
1.5G millimeter wave antenna module
\n2.Satellite communication RF front-end<\/p>","protected":false},"featured_media":1130,"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-1129","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