Yuav daws teeb meem EMI li cas hauv Multilayer PCB tsim?

Koj puas paub yuav daws qhov teeb meem EMI li cas thaum tsim ntau txheej PCB?

Cia kuv qhia koj!

Muaj ntau txoj hauv kev los daws cov teeb meem EMI.Niaj hnub nimno EMI kev tiv thaiv muaj xws li: siv EMI kev tiv thaiv txheej, xaiv qhov tsim nyog EMI kev tawm tsam thiab EMI simulation tsim.Raws li cov txheej txheem PCB yooj yim tshaj plaws, daim ntawv no tham txog kev ua haujlwm ntawm PCB pawg hauv kev tswj hwm EMI hluav taws xob thiab kev tsim PCB.

lub zog tsheb npav

Qhov tso zis hluav taws xob dhia ntawm IC tuaj yeem ua kom nrawm dua los ntawm kev tso lub peev xwm tsim nyog nyob ze ntawm lub hwj chim tus pin ntawm IC.Txawm li cas los xij, qhov no tsis yog qhov kawg ntawm qhov teeb meem.Vim tias qhov tsawg zaus teb ntawm lub capacitor, nws tsis yooj yim rau lub capacitor los tsim kom muaj lub zog sib haum xeeb uas xav tau los tsav lub IC tso tawm kom huv hauv tag nrho cov zaus band.Tsis tas li ntawd, qhov hluav taws xob hloov pauv tau tsim rau ntawm lub tsheb npav fais fab yuav ua rau qhov hluav taws xob poob ntawm ob qho kawg ntawm qhov inductance ntawm txoj kev decoupling.Cov kev hloov pauv hloov pauv no yog qhov tseem ceeb ntawm hom EMI cuam tshuam qhov chaw.Peb yuav daws tau tej teeb meem no li cas?

Nyob rau hauv cov ntaub ntawv ntawm IC nyob rau hauv peb lub rooj tsavxwm Circuit Court, lub hwj chim txheej nyob ib ncig ntawm lub IC yuav suav hais tias yog ib tug zoo high-frequency capacitor, uas muaj peev xwm sau tau lub zog los ntawm discrete capacitor uas muab high-frequency zog rau huv si tso zis.Tsis tas li ntawd, qhov inductance ntawm lub hwj chim zoo yog me me, yog li cov teeb liab hloov pauv hloov pauv los ntawm inductor kuj me me, yog li txo cov hom EMI.

Tau kawg, kev sib txuas ntawm cov txheej txheem hluav taws xob thiab IC fais fab mov tus pin yuav tsum luv li sai tau, vim tias qhov nce ntawm ntug ntawm cov teeb liab digital yog nrawm dua thiab nrawm dua.Nws yog qhov zoo dua los txuas nws ncaj qha mus rau lub ncoo qhov twg IC fais fab tus pin nyob, uas yuav tsum tau sib tham nyias.

Txhawm rau tswj hwm hom EMI, cov txheej txheem hluav taws xob yuav tsum yog cov txheej txheem tsim hluav taws xob zoo los pab decouple thiab muaj qhov inductance tsawg txaus.Qee tus neeg yuav nug, nws zoo npaum li cas?Cov lus teb nyob ntawm lub hwj chim txheej, cov khoom nruab nrab ntawm cov khaubncaws sab nraud povtseg, thiab kev khiav hauj lwm zaus (piv txwv li, ib qho kev ua haujlwm ntawm IC nce lub sijhawm).Feem ntau, qhov sib nrug ntawm lub hwj chim txheej yog 6mil, thiab cov interlayer yog FR4 cov khoom, yog li qhov sib npaug capacitance ib square inch ntawm lub hwj chim txheej yog li 75pF.Obviously, qhov me me ntawm txheej txheej, qhov loj dua qhov capacitance.

Tsis muaj ntau cov khoom siv nrog lub sijhawm nce ntawm 100-300ps, tab sis raws li kev txhim kho tam sim no ntawm IC, cov khoom siv nrog lub sijhawm nce siab hauv thaj tsam ntawm 100-300ps yuav nyob hauv qhov sib faib siab.Rau circuits nrog 100 mus rau 300 PS nce lub sij hawm, 3 mil txheej sib nrug yog tsis muaj feem xyuam rau feem ntau daim ntaub ntawv.Thaum lub sij hawm ntawd, nws yog ib qho tsim nyog yuav tau txais kev siv thev naus laus zis delamination nrog lub interlayer sib nrug tsawg dua 1mil, thiab hloov cov khoom siv FR4 dielectric nrog cov khoom siv siab dielectric tas li.Tam sim no, ceramics thiab potted plastics tuaj yeem ua tau raws li cov qauv tsim ntawm 100 txog 300ps nce lub sij hawm circuits.

Txawm hais tias cov ntaub ntawv tshiab thiab cov txheej txheem yuav raug siv yav tom ntej, feem ntau 1 txog 3 ns nce lub sij hawm circuits, 3 mus rau 6 mil txheej spacing, thiab FR4 dielectric cov ntaub ntawv feem ntau yog txaus los tuav high-end harmonics thiab ua rau ib ntus teeb liab tsawg txaus, uas yog , hom hom EMI tuaj yeem txo qis heev.Nyob rau hauv daim ntawv no, tus qauv tsim ntawm PCB txheej stacking yog muab, thiab txheej txheej yuav tsum yog 3 mus rau 6 mil.

electromagnetic shielding

Los ntawm lub teeb liab routing taw tes ntawm view, ib tug zoo txheej txheej yuav tsum tau muab tag nrho cov teeb liab kab nyob rau hauv ib los yog ntau tshaj txheej, uas nyob ib sab ntawm lub hwj chim txheej los yog hauv av dav hlau.Rau cov khoom siv hluav taws xob, cov txheej txheem txheej txheej zoo yuav tsum yog cov txheej txheem hluav taws xob nyob ib sab ntawm lub dav hlau hauv av, thiab qhov kev ncua deb ntawm lub hwj chim txheej thiab lub dav hlau hauv av yuav tsum tsawg li tsawg tau, uas yog qhov peb hu ua "txhim kho" lub tswv yim.

PCB pawg

Lub tswv yim zoo li cas tuaj yeem pab tiv thaiv thiab tiv thaiv EMI?Cov txheej txheem txheej txheej hauv qab no xav tias cov khoom siv hluav taws xob tam sim no ntws ntawm ib txheej thiab qhov hluav taws xob ib leeg lossis ntau qhov hluav taws xob raug faib rau ntau qhov sib txawv ntawm tib txheej.Cov ntaub ntawv ntawm ntau lub hwj chim txheej yuav tham tom qab.

4-ply phaj

Muaj qee qhov teeb meem hauv kev tsim ntawm 4-ply laminates.Ua ntej tshaj plaws, txawm tias lub teeb liab txheej nyob rau hauv txheej txheej thiab lub zog thiab lub dav hlau hauv av nyob hauv txheej txheej, qhov kev ncua deb ntawm lub hwj chim txheej thiab lub dav hlau hauv av tseem loj heev.

Yog tias tus nqi yuav tsum yog thawj zaug, ob qho kev xaiv hauv qab no rau cov tsoos 4-ply board tuaj yeem txiav txim siab.Ob leeg tuaj yeem txhim kho EMI kev tiv thaiv kev ua tau zoo, tab sis lawv tsuas yog tsim nyog rau cov ntaub ntawv uas qhov ntom ntawm cov khoom ntawm lub rooj tsavxwm yog tsawg txaus thiab muaj thaj tsam txaus nyob ib puag ncig cov khoom (kom tso cov txheej tooj liab uas yuav tsum tau ua rau lub hwj chim mov).

Thawj yog cov txheej txheem nyiam.Cov txheej txheej txheej ntawm PCB yog txhua txheej, thiab nruab nrab ob txheej yog teeb liab / fais fab txheej.Lub hwj chim mov ntawm lub teeb liab txheej yog routed nrog cov kab dav, uas ua rau txoj kev impedance ntawm lub hwj chim mov tam sim no qis thiab impedance ntawm teeb liab microstrip txoj kev tsawg.Los ntawm qhov kev xav ntawm EMI tswj, qhov no yog qhov zoo tshaj plaws 4-txheej PCB qauv muaj.Hauv cov txheej txheem thib ob, txheej txheej txheej nqa lub zog thiab hauv av, thiab nruab nrab ob txheej nqa lub teeb liab.Piv nrog rau cov tsoos 4-txheej board, kev txhim kho ntawm cov tswv yim no yog me me, thiab interlayer impedance tsis zoo li cov tsoos 4-txheej board.

Yog tias qhov thaiv thaiv kab hluav taws xob yuav tsum tau tswj hwm, cov txheej txheem txheej txheej saum toj no yuav tsum tau ceev faj heev kom nteg cov xaim hauv qab cov kob tooj liab ntawm cov khoom siv hluav taws xob thiab hauv av.Tsis tas li ntawd, cov kob tooj liab ntawm cov khoom siv hluav taws xob lossis cov stratum yuav tsum sib cuam tshuam ntau li ntau tau los xyuas kom meej qhov kev sib txuas ntawm DC thiab tsawg zaus.

6-ply phaj

Yog tias qhov ntom ntawm cov khoom ntawm 4-txheej board loj, 6-txheej phaj yog zoo dua.Txawm li cas los xij, cov nyhuv tiv thaiv ntawm qee cov txheej txheem stacking hauv kev tsim ntawm 6-txheej board tsis zoo txaus, thiab lub sijhawm hloov pauv ntawm lub zog tsheb npav tsis txo.Ob qho piv txwv tau tham hauv qab no.

Nyob rau hauv thawj rooj plaub, lub hwj chim mov thiab av yog muab tso rau hauv lub thib ob thiab thib tsib txheej.Vim lub siab impedance ntawm tooj liab clad fais fab mov, nws yog heev unfavorable los tswj cov hom EMI hluav taws xob.Txawm li cas los xij, los ntawm qhov pom ntawm lub teeb liab impedance tswj, txoj kev no yog qhov tseeb heev.

Hauv qhov piv txwv thib ob, cov khoom siv hluav taws xob thiab hauv av tau muab tso rau hauv cov txheej thib peb thiab thib plaub.Qhov kev tsim no daws qhov teeb meem ntawm tooj liab clad impedance ntawm lub hwj chim mov.Vim tias tsis zoo electromagnetic shielding kev ua tau zoo ntawm txheej 1 thiab txheej 6, qhov sib txawv ntawm EMI nce.Yog hais tias tus naj npawb ntawm cov teeb liab kab ntawm ob txheej txheej yog qhov tsawg tshaj plaws thiab qhov ntev ntawm cov kab yog luv heev (tsawg dua 1/20 ntawm qhov siab tshaj plaws harmonic wavelength ntawm lub teeb liab), tus tsim yuav daws tau qhov teeb meem ntawm txawv hom EMI.Cov txiaj ntsig tau pom tias qhov kev tawm tsam ntawm kev sib txawv ntawm hom EMI yog qhov zoo tshwj xeeb tshaj yog thaum cov txheej txheej sab nrauv tau ntim nrog tooj liab thiab thaj chaw tooj liab clad yog grounded (txhua 1/20 wavelength interval).Raws li tau hais los saum no, tooj liab yuav tsum muab tso rau


Post lub sij hawm: Jul-29-2020