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. Pib los ntawm qhov yooj yim tshaj plaws PCB layout, tsab xov xwm no tham txog lub luag hauj lwm thiab tsim cov tswv yim ntawm PCB txheej stacking nyob rau hauv kev tswj EMI hluav taws xob.

Tsim nyog tso cov capacitors ntawm lub peev xwm tsim nyog nyob ze ntawm lub hwj huam mov pins ntawm IC tuaj yeem ua rau IC tso zis voltage dhia nrawm dua. Txawm li cas los xij, qhov teeb meem tsis xaus ntawm no. Raws li cov lus teb tsawg zaus ntawm cov capacitors, qhov no ua rau cov capacitors tsis tuaj yeem tsim lub zog sib haum xeeb uas yuav tsum tau 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 tsim ib qho hluav taws xob poob hla lub inductor ntawm txoj kev decoupling. Cov kev hloov hluav taws xob tam sim no yog hom tseem ceeb EMI cuam tshuam qhov chaw. Peb yuav tsum daws cov teeb meem no li cas?

Raws li IC ntawm peb lub rooj tsav xwm hauv Circuit Court muaj kev txhawj xeeb, cov txheej txheem hluav taws xob nyob ib puag ncig IC tuaj yeem suav tau tias yog lub tshuab hluav taws xob zoo tshaj plaws, uas tuaj yeem sau tau ib feem ntawm lub zog tawm los ntawm kev sib cais capacitor uas muab lub zog ntau zaus rau kev huv. tso zis. Tsis tas li ntawd, qhov inductance ntawm lub hwj huam zoo yuav tsum yog me me, yog li cov teeb liab hloov pauv los ntawm inductance kuj me me, yog li txo qis EMI hom.

Tau kawg, kev sib txuas ntawm lub hwj chim txheej thiab IC lub hwj chim tus pin yuav tsum yog luv li sai tau, vim tias qhov nce ntawm ntug ntawm cov teeb liab digital tau nrawm dua thiab nrawm dua, thiab nws yog qhov zoo tshaj plaws los txuas nws ncaj qha mus rau lub ncoo qhov twg lub zog IC. pin yog nyob. Qhov no yuav tsum tau sib tham nyias.

Txhawm rau tswj hwm hom EMI, lub dav hlau fais fab yuav tsum pab cuam tshuam thiab muaj qhov inductance tsawg txaus. Lub dav hlau fais fab no yuav tsum yog ib lub dav hlau tsim tau zoo. Tej zaum ib tug yuav nug, zoo npaum li cas? Cov lus teb rau lo lus nug yog nyob ntawm qhov txheej txheem ntawm cov khoom siv hluav taws xob, cov khoom siv nruab nrab ntawm cov khaubncaws sab nraud povtseg, thiab kev ua haujlwm zaus (uas yog, kev ua haujlwm ntawm lub sijhawm nce ntawm IC). Feem ntau, qhov sib nrug ntawm lub hwj chim txheej yog 6mil, thiab lub interlayer yog FR4 cov khoom, qhov sib npaug ntawm lub hwj chim txheej ib square inch yog hais txog 75pF. Obviously, qhov me me ntawm txheej txheej, qhov ntau dua qhov capacitance.

Tsis muaj ntau yam khoom siv nrog lub sijhawm nce ntawm 100 mus rau 300 ps, ​​tab sis raws li kev txhim kho IC tam sim no, cov khoom siv nrog lub sijhawm nce siab nyob rau hauv thaj tsam ntawm 100 txog 300 ps yuav nyob hauv qhov feem ntau. Rau circuits nrog lub sij hawm sawv ntawm 100 mus rau 300ps, 3mil txheej sib nrug yuav tsis haum rau feem ntau daim ntaub ntawv. Thaum lub sij hawm ntawd, nws yog ib qho tsim nyog yuav tsum siv cov txheej txheem txheej txheej nrog cov txheej txheem sib nrug tsawg dua 1 mil, thiab hloov FR4 dielectric cov ntaub ntawv nrog cov khoom siv nrog cov dielectric siab. Tam sim no, ceramics thiab ceramics tuaj yeem ua tau raws li cov qauv tsim ntawm 100 txog 300 ps nce lub sij hawm circuits.

Txawm hais tias cov ntaub ntawv tshiab thiab cov txheej txheem tshiab yuav raug siv rau yav tom ntej, rau niaj hnub no 1 mus rau 3ns nce lub sij hawm circuits, 3 mus rau 6mil txheej spacing thiab FR4 dielectric cov ntaub ntawv, nws yog feem ntau txaus los tuav high-end harmonics thiab ua rau lub transient teeb liab tsawg txaus. , uas yog hais tias, Hom Hom EMI tuaj yeem txo qis heev. Lub PCB txheej txheej tsim qauv piv txwv tau muab rau hauv tsab xov xwm no yuav xav tias txheej txheej ntawm 3 mus rau 6 mils.

Lub tshuab hluav taws xob tiv thaiv

Los ntawm qhov kev xav ntawm cov teeb liab kab, ib qho zoo txheej txheej yuav tsum tau muab tag nrho cov teeb liab kab nyob rau hauv ib los yog ntau txheej txheej, cov khaubncaws sab nraud povtseg ntawm lub hwj chim txheej los yog av txheej. Rau cov khoom siv hluav taws xob, lub tswv yim zoo txheej txheej yuav tsum yog cov txheej txheem hluav taws xob nyob ib sab ntawm cov txheej hauv av, thiab qhov kev ncua deb ntawm lub hwj chim txheej thiab txheej hauv av yog me me li sai tau. Qhov no yog qhov peb hu ua “layering” tswv yim.

PCB stacking

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 cov 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-txheej board

Muaj ob peb yam teeb meem nrog 4-txheej board tsim. Ua ntej ntawm tag nrho cov, cov tsoos plaub-txheej board nrog ib tug tuab ntawm 62 mils, txawm hais tias lub teeb liab txheej yog nyob rau hauv txheej txheej, thiab lub hwj chim thiab av txheej yog nyob rau hauv lub puab txheej, qhov kev ncua deb ntawm lub hwj chim txheej thiab av txheej. tseem loj heev.

Yog tias tus nqi xav tau yog thawj zaug, koj tuaj yeem xav txog ob qho kev xaiv hauv qab no rau cov tsoos 4-txheej board. Ob txoj kev daws teeb meem no tuaj yeem txhim kho qhov kev ua tau zoo ntawm EMI kev tawm tsam, tab sis lawv tsuas yog tsim nyog rau cov ntawv thov uas qhov sib xyaw ua ke ntawm lub rooj tsavxwm tsis tshua muaj txaus thiab muaj thaj chaw txaus nyob ib puag ncig cov khoom (tso qhov xav tau lub zog tooj liab txheej).

Thawj qhov kev xaiv yog thawj qhov kev xaiv. Cov txheej txheej txheej ntawm PCB yog tag nrho cov txheej hauv av, thiab nruab nrab ob txheej yog teeb liab / fais fab txheej. Lub hwj chim mov ntawm lub teeb liab txheej yog routed nrog ib tug dav kab, uas yuav ua rau txoj kev impedance ntawm lub hwj chim mov tam sim no tsawg, thiab impedance ntawm lub teeb liab microstrip txoj kev kuj yog 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 siv lub zog thiab hauv av, thiab nruab nrab ob txheej siv cov cim. Piv nrog rau cov tsoos 4-txheej board, qhov kev txhim kho yog me me, thiab interlayer impedance yog tsis zoo li cov tsoos 4-txheej board.

Yog tias koj xav tswj cov kab mob impedance, cov txheej txheem stacking saum toj no yuav tsum tau ceev faj heev los npaj cov kab hauv qab lub zog thiab av tooj liab Islands tuaj. Tsis tas li ntawd, cov kob tooj liab ntawm cov khoom siv hluav taws xob lossis cov txheej hauv av yuav tsum muaj kev sib txuas ntau li ntau tau los xyuas kom meej DC thiab kev sib txuas tsis tshua muaj zog.

6-txheej board

Yog tias qhov ntom ntawm cov khoom ntawm 4-txheej board yog qhov siab, 6-txheej board yog qhov zoo tshaj. Txawm li cas los xij, qee cov txheej txheem stacking nyob rau hauv 6-txheej board tsim tsis zoo txaus los tiv thaiv electromagnetic teb, thiab muaj me ntsis cuam tshuam rau kev txo cov teeb liab ntawm lub hwj chim tsheb npav. Ob qho piv txwv tau tham hauv qab no.

Hauv thawj kis, cov khoom siv hluav taws xob thiab hauv av tau muab tso rau ntawm 2nd thiab 5th khaubncaws sab nraud povtseg. Vim hais tias ntawm qhov siab impedance ntawm tooj liab txheej ntawm lub hwj chim 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.