Lub dielectric qhov tsis tu ncua (Dk) thiab qhov tsis zoo (Df) ntawm cov khoom siv hluav taws xob ntau zaus yog cov ntsiab lus tseem ceeb uas txiav txim siab qhov zoo ntawm cov teeb liab kis tau zoo. Ntau tus neeg tsim khoom lag luam 'nominal tsis muaj teeb meem xws li opaque kuaj cov xwm txheej thiab cov ntawv sau tsis tseeb, uas tuaj yeem yooj yim ua rau muaj teeb meem hauv kev tsim thiab tsim khoom. Hauv qab no, peb yuav sau cov ntsiab lus tseem ceeb ntawm kev paub txog ntawm ob qhov kev txwv no los pab koj kom tsis txhob muaj cov cuab yeej cuab tam.
Basic txhais thiab kev lag luam Common Terminology
Dielectric qhov tsis tu ncua (Dk / ε r): characterizes lub peev xwm ntawm pcb substrate los khaws cov nqi hauv hluav taws xob. Nyob rau hauv engineering, nws yog hais txog tus txheeb ze dielectric tas li (nqus nqi ntawm 1), uas yog ib tug dimensionless intrinsic khoom.
Loss factor (Df / tan δ): Hais txog qhov feem ntawm hluav taws xob hluav taws xob hloov mus rau hauv thermal zog ib chav tsev ib lub sij hawm los ntawm ib tug substrate nyob rau hauv high zaus alternating hluav taws xob teb, kuj hu ua lub dielectric poob tangent.
Qhov yooj yim tshaj plaws overlooked parameter ntxiab
Kev ntsuas zaus tsis sib haum: Dk ntawm qhov zoo tib yam fr4 feem ntau yog ntsuas ntawm qhov tsawg zaus ntawm 1MHz, thaum lub siab zaus luam tawm Circuit Court boards yuav tsum muaj tsawg kawg yog 10GHz (X-band) ntawm cov ntaub ntawv ntsuas, thiab qhov tsis tshua muaj zaus tsis tuaj yeem sawv cev rau qhov kev ua haujlwm siab ntawm txhua qhov.
Nominal tolerance virtual marking: Lub Dk batch sib txawv ntawm fr4 zoo tib yam tuaj yeem ncav cuag ± 0.2, thaum Dk kam rau siab ntawm cov khoom tsim nyog yuav tsum tau tswj tsis pub dhau ± 0.02. Lub cim cim virtual yuav ncaj qha ua rau qhov tseeb impedance sib txawv ntawm 5-10 Ω, tshaj qhov yuav tsum tau ua siab ntev ntawm ± 2% rau RF circuits.
Ib puag ncig kev ruaj ntseg zais zais: Ntau yam tsawg- cov khoom siv hluav taws xob muaj nqi siab tsis sau cov dielectric qhov kub thiab txias coefficient τ Dk. Hauv cov xwm txheej sab nraud xws li -40℃mus rau +85 degree, Dk hloov pauv nrog qhov kub thiab txias, ncaj qha ua rau impedance drift thiab teeb liab tsis sib haum.
Kev cuam tshuam ntawm cov av tsis tau piav qhia: thaum cov dej nqus ntawm cov substrate siab dhau lawm, Dk yuav nce ntxiv tom qab kev nqus dej, Df yuav deteriorate synchronously, thiab cov teeb liab poob hauv qhov chaw ntub dej yuav nyob deb tshaj tus nqi nominal.
Qhov tseem ceeb cuam tshuam ntawm ob qhov tsis ua haujlwm ntawm kev ua haujlwm hauv Circuit Court
Dielectric qhov tsis tu ncua (Dk):
Kev txiav txim ncaj qha rau lub teeb liab kis tau tus mob ceev, qhov qis dua Dk, qhov me me ntawm cov teeb liab propagation qeeb, thiab qhov ceev ntawm kev sib kis ceev.
Nws yog cov ntsiab lus tseem ceeb rau impedance simulation, thiab Dk sib txawv tuaj yeem ua rau qhov tsis ua haujlwm ntawm cov qauv impedance xws li 50 Ω / 100 Ω, ua rau muaj kev cuam tshuam cov teeb liab.
Loss factor (Df):
Kev txiav txim ncaj qha rau qhov poob ntawm cov teeb liab ntau zaus, nyob rau hauv lub zaus band siab tshaj 10GHz, qhov poob ib nti ntawm fr4 zoo tib yam tuaj yeem ncav cuag 1-2dB, thiab cov khoom siv zoo zaus tuaj yeem tswj tau hauv 0.2dB.
Df ntau dhau tuaj yeem ua rau lub zog khib nyiab ntawm qhov kawg xa tawm thiab tsis muaj peev xwm demodulate tsis muaj zog cov cim ntawm qhov kawg tau txais, ncaj qha txo qis kev sib txuas lus thiab kev paub txog radar rhiab heev.
Hom parameter siv rau mainstream high zaus sheet hlau
| khoom system | Tus nqi Dk (10GHz) | Tus nqi Df (10GHz) | Cov xwm txheej tseem ceeb siv tau |
|---|---|---|---|
| Yam tsawg kawg FR-4 | 4.2~4.6 | ~0.02 | Tsawg ceev digital circuits hauv qab 1GHz |
| Cov pa roj carbon hydrogen resin series | 3.2~3.7 | 0.003~0.008 | 5G puag chaw nres tsheb, siab -speed optical module |
| RO4000 series | 3.48~3.66 | 0.002~0.0037 | RF amplifier, tsheb radar |
| PTFE hloov series | 2.2~2.6 | 0.001~0.003 | millimeter yoj, satellite kev sib txuas lus, tub rog radar |
Cov txheej txheem kev ntsuas kev tso cai feem ntau siv hauv kev lag luam
Lub Dk thiab Df ntawm high zaus luam tawm Circuit Court board tsis tuaj yeem sim siv Q-txoj kev ntawm fr4 zoo tib yam. Txoj kev siv sawb kab resonance feem ntau siv hauv kev lag luam yog ntsuas qhov resonant zaus ntawm strip kab resonator siv vector network analyzer rau invert Dk, thiab ntsuas qhov zoo tshaj Q tus nqi rau invert Df. Cov txiaj ntsig tau ze dua rau lub xeev ua haujlwm ntawm pcb.