Parasitic Capacitance thiab Parasitic Inductance ntawm Via

1. Via

Vias yog ib qho ntawm cov khoom tseem ceeb ntawm ntau txheej PCBs, thiab tus nqi ntawm qhov drilling feem ntau yog 30 feem pua ​​​​rau 40 feem pua ​​​​ntawm cov nqi ntawm PCB manufacturing. Yooj yim muab, txhua qhov ntawm PCB tuaj yeem hu ua viav vias. Los ntawm qhov kev xav ntawm kev ua haujlwm, vias tuaj yeem muab faib ua ob pawg: ib qho yog siv rau kev sib txuas hluav taws xob ntawm cov khaubncaws sab nraud povtseg; lwm qhov yog siv los kho lossis tso cov khoom siv. Nyob rau hauv cov nqe lus ntawm cov txheej txheem, cov vias no feem ntau muab faib ua peb pawg, uas yog dig muag vias, faus vias thiab vias. Qhov qhov muag tsis pom kev nyob rau sab saum toj thiab hauv qab ntawm lub rooj tsav xwm luam tawm thiab muaj qhov tob rau kev sib txuas ntawm cov kab hluav taws xob saum npoo thiab lub hauv paus hauv Circuit Court. Qhov tob ntawm lub qhov feem ntau tsis tshaj ib qho piv txwv (aperture). Cov qhov faus yog hais txog cov qhov sib txuas uas nyob rau hauv txheej sab hauv ntawm lub rooj tsavxwm luam tawm, uas tsis txuas mus rau qhov chaw ntawm lub rooj tsavxwm. Qhov saum toj no ob hom ntawm qhov yog nyob rau hauv lub puab txheej ntawm lub Circuit Court board. Ua ntej lamination, cov txheej txheem los ntawm lub qhov yog siv los ua kom tiav, thiab ob peb txheej txheej sab hauv tuaj yeem sib tshooj thaum lub sijhawm tsim los ntawm lub qhov. Hom thib peb yog hu ua lub qhov los ntawm qhov, uas dhau los ntawm tag nrho lub rooj tsav xwm hauv Circuit Court thiab tuaj yeem siv los ua kom paub txog kev sib txuas sab hauv lossis ua lub qhov mounting qhov chaw rau cov khoom. Txij li thaum lub qhov los ntawm qhov yooj yim dua kom paub txog hauv cov txheej txheem thiab tus nqi qis dua, feem ntau cov ntawv luam tawm Circuit boards siv nws es tsis txhob siv ob hom vias. Cov vias tau hais hauv qab no, tshwj tsis yog tias tau teev tseg, raug suav tias yog vias. Los ntawm tus qauv tsim ntawm qhov pom, ib qho ntawm feem ntau yog tsim los ntawm ob ntu, ib qho yog qhov laum qhov nruab nrab, thiab lwm qhov yog qhov chaw ncoo nyob ib ncig ntawm lub qhov laum, raws li qhia hauv daim duab hauv qab no. Qhov loj ntawm ob ntu no txiav txim siab qhov loj ntawm cov viav vias. Obviously, nyob rau hauv high-speed, high-density PCB tsim, tus tsim ib txwm cia siab tias qhov me me ntawm lub qhov, qhov zoo dua, yog li ntawd muaj ntau qhov chaw xaim tuaj yeem tso rau ntawm lub rooj tsavxwm. Tsis tas li ntawd, qhov me me ntawm lub qhov, qhov me me ntawm tus kab mob parasitic capacitance ntawm nws tus kheej. Qhov me me, nws yog qhov tsim nyog rau high-speed circuits. Txawm li cas los xij, qhov txo qis hauv qhov loj me kuj ua rau tus nqi nce ntxiv, thiab qhov loj ntawm lub qhov ntawm lub qhov tsis tuaj yeem raug txo kom tas mus li. Nws raug txwv los ntawm kev siv tshuab drilling thiab plating: qhov me me ntawm lub qhov, qhov yooj yim dua nws yog laum Lub qhov ntev yuav siv sij hawm, qhov yooj yim dua nws yog deviate los ntawm qhov chaw nruab nrab; thiab thaum qhov tob ntawm lub qhov siab tshaj 6 npaug ntawm txoj kab uas hla ntawm lub qhov drilled, nws yog tsis yooj yim sua kom paub meej tias lub qhov phab ntsa tuaj yeem sib npaug plated nrog tooj liab. Piv txwv li, lub thickness (los ntawm-qhov tob) ntawm ib txwm 6- txheej PCB board yog hais txog 50Mil, yog li lub drilling txoj kab uas hla PCB manufacturers muab tau me me li 8Mil.

Qhov thib ob, tus kab mob parasitic capacitance ntawm lub via

Lub qhov nws tus kheej muaj tus kab mob parasitic capacitance rau hauv av. Yog tias nws paub tias txoj kab uas hla ntawm qhov kev sib cais ntawm cov txheej hauv av yog D2, txoj kab uas hla ntawm lub ncoo yog D1, lub thickness ntawm lub rooj tsavxwm PCB yog T, thiab qhov dielectric qhov tsis tu ncua ntawm lub rooj tsavxwm substrate yog ε, cov kab mob parasitic capacitance. ntawm lub qhov ntawm lub qhov yog kwv yees li: C=1.41εTD1/(D2-D1) Lub ntsiab cuam tshuam ntawm tus kab mob parasitic capacitance ntawm lub qhov ntawm lub Circuit Court yog kom ntev lub sij hawm sawv ntawm lub teeb liab thiab txo. qhov ceev ntawm Circuit Court. Piv txwv li, rau lub rooj tsavxwm PCB nrog lub thickness ntawm 50Mil, yog tias ib lub qhov ntawm lub qhov nrog ib txoj kab uas hla ntawm 10Mil thiab lub ncoo txoj kab uas hla ntawm 20Mil yog siv, thiab qhov kev ncua deb ntawm lub ncoo thiab hauv av tooj liab thaj tsam yog 32Mil, ces peb tuaj yeem kwv yees qhov ntawm lub qhov los ntawm cov qauv saum toj no Cov kab mob parasitic capacitance yog kwv yees li: C=1.41x4.4x0.{{30 }}50x0.020/(0. )=2.2 x0.517x(55/2)=31.28ps. Los ntawm cov txiaj ntsig no, nws tuaj yeem pom tau tias txawm hais tias qhov cuam tshuam ntawm kev ua kom qeeb ntawm qhov nce qeeb los ntawm cov kab mob parasitic capacitance ntawm ib qho ntawm ib qho tsis pom tseeb, yog tias lub viav vias siv ntau zaus hauv cov xaim los hloov ntawm cov txheej, tus tsim qauv tseem xav tau. ua tib zoo xav.

3. Parasitic inductance ntawm vias

Ib yam li ntawd, muaj cov kab mob parasitic inductance nrog rau cov kab mob parasitic capacitance hauv lub qhov ntawm lub qhov. Nyob rau hauv kev tsim ntawm high-speed digital circuits, qhov teeb meem tshwm sim los ntawm cov kab mob parasitic inductance ntawm lub qhov ntawm lub qhov feem ntau ntau dua li qhov cuam tshuam ntawm cov kab mob parasitic capacitance. Nws cov kab mob parasitic inductance yuav ua rau tsis muaj zog rau kev koom tes ntawm bypass capacitor thiab ua rau tsis muaj zog lim dej ntawm tag nrho lub zog. Peb tuaj yeem siv cov qauv hauv qab no kom yooj yim xam qhov kwv yees tus kab mob parasitic inductance ntawm a via: () - PCB Tsim Cov Lus Qhia - Txog Vias qhov twg L yog hais txog qhov inductance ntawm lub vias, h yog qhov ntev ntawm qhov, thiab d yog txoj kab uas hla. qhov nruab nrab drilled qhov. Nws tuaj yeem pom los ntawm cov qauv hais tias txoj kab uas hla ntawm lub qhov ntawm lub qhov muaj qhov cuam tshuam me ntsis ntawm qhov inductance, tab sis qhov ntev ntawm lub qhov ntawm lub qhov muaj qhov cuam tshuam zoo rau qhov inductance. Tseem siv cov piv txwv saum toj no, qhov inductance ntawm lub vias tuaj yeem suav ua: L=5.08x0.050[ln(4x0.050/0.010) 1]{13}}.015nH. Yog tias lub sijhawm nce ntawm lub teeb liab yog 1ns, ces nws qhov sib npaug impedance yog: XL=πL / T10-90=3.19Ω. Xws li impedance yuav tsis raug ignored thaum muaj ib tug high-frequency tam sim no hla. Tshwj xeeb, nws yuav tsum tau muab sau tseg tias lub bypass capacitor yuav tsum dhau los ntawm ob vias thaum txuas lub hwj chim txheej thiab hauv av txheej, kom cov kab mob parasitic inductance ntawm vias yuav ob npaug. 4. Ntawm kev tsim hauv high-speed PCB Los ntawm kev soj ntsuam saum toj no ntawm cov kab mob parasitic ntawm vias, peb tuaj yeem pom tias nyob rau hauv high-speed PCB tsim, seemingly yooj yim vias feem ntau coj zoo tsis zoo rau Circuit Court tsim. nyhuv.

Txhawm rau txo qhov tsis zoo tshwm sim los ntawm cov kab mob parasitic ntawm vias, peb tuaj yeem sim peb qhov zoo tshaj plaws hauv kev tsim:

1. Xav txog cov nqi thiab cov teeb liab zoo, xaiv qhov tsim nyog ntawm lub qhov loj. Piv txwv li, rau 6-10 txheej ntawm nco module PCB tsim, nws yog qhov zoo dua los siv 10/20Mil (drilling/pad) vias. Rau qee qhov siab ceev thiab me me, koj tuaj yeem sim siv 8/18Mil vias. qhov. Raws li cov txheej txheem tam sim no, nws nyuaj rau siv cov vias me me. Rau lub zog lossis av vias, xav txog kev siv qhov loj dua los txo qhov impedance.

2. Los ntawm ob lub qauv uas tau tham saum toj no, nws tuaj yeem xaus lus tias siv lub rooj tsav xwm PCB thinner yog qhov zoo los txo cov kab mob parasitic ntawm ob lub vias.

3. Sim tsis txhob hloov cov txheej txheej ntawm cov teeb liab kab ntawm PCB, uas yog hais tias, sim tsis txhob siv cov vias tsis tsim nyog.

4. Cov pins ntawm lub hwj huam mov thiab hauv av yuav tsum tau drilled ntawm qhov nyob ze. Qhov luv luv cov coj ntawm lub qhov ntawm lub qhov thiab cov pins, qhov zoo dua, vim tias lawv yuav ua rau kom cov inductance. Nyob rau tib lub sijhawm, cov coj ntawm lub zog thiab hauv av yuav tsum yog tuab li ua tau kom txo qis impedance.

5. Muab ib co grounded vias ze ntawm lub vias qhov twg lub teeb liab hloov cov khaubncaws sab nraud povtseg los muab lub voj kaw rau lub teeb liab. Nws tseem muaj peev xwm tso ntau qhov av tsis tu ncua ntawm lub PCB. Tau kawg, yuav tsum muaj kev hloov pauv hauv kev tsim. Cov qauv ntawm kev sib tham saum toj no yog rooj plaub uas txhua txheej muaj lub ncoo, thiab qee zaum, peb tuaj yeem txo lossis txawm tias tshem cov ntaub qhwv ntawm qee cov khaubncaws sab nraud povtseg. Tshwj xeeb tshaj yog nyob rau hauv cov ntaub ntawv ntawm ib tug loj heev ntawm qhov ceev, nws yuav ua rau ib tug tawg qhov chaw uas cais lub voj ntawm cov tooj liab txheej. Yuav kom daws tau qhov teeb meem no, ntxiv rau kev txav txoj hauj lwm ntawm cov viav vias, peb kuj tuaj yeem txiav txim siab tso qhov ntawm ntawm txheej tooj liab. Lub ncoo loj yog txo.