Yadda za a warware matsalar EMI a Multilayer PCB design?

Shin kun san yadda ake warware matsalar EMI lokacin ƙirar PCB mai yawan Layer?

Bari in gaya muku!

Akwai hanyoyi da yawa don magance matsalolin EMI.Hanyoyin murkushe EMI na zamani sun haɗa da: yin amfani da shafi na EMI, zabar sassa na EMI masu dacewa da ƙirar simintin EMI.Dangane da mafi mahimmancin shimfidar PCB, wannan takarda ta tattauna aikin tari na PCB wajen sarrafa hasken EMI da ƙwarewar ƙirar PCB.

bas na wuta

Za a iya haɓaka tsallen wutar lantarki na IC ta hanyar sanya ƙarfin da ya dace kusa da fil ɗin wutar lantarki na IC.Duk da haka, wannan ba shine ƙarshen matsalar ba.Saboda ƙayyadaddun amsawar mitar na capacitor, ba shi yiwuwa capacitor ya samar da ikon daidaitawa da ake buƙata don fitar da fitar da IC mai tsabta a cikin cikakken rukunin mitar.Bugu da kari, wutar lantarki na wucin gadi da aka kafa akan bas din wutar lantarki zai haifar da raguwar wutar lantarki a bangarorin biyu na inductance na hanyar yankewa.Waɗannan ƙarfin lantarki na wucin gadi sune manyan hanyoyin tsoma baki na EMI na gama gari.Ta yaya za mu magance waɗannan matsalolin?

A cikin yanayin IC a kan allon mu, za a iya ɗaukar madaurin wutar lantarki a kusa da IC a matsayin mai kyau mai karfin mita mai girma, wanda zai iya tattara makamashin da aka yi amfani da shi ta hanyar capacitor mai hankali wanda ke ba da makamashi mai yawa don fitarwa mai tsabta.Bugu da kari, inductance na mai kyau Layer iko kadan ne, don haka siginar wucin gadi da aka haɗa ta inductor shima ƙarami ne, don haka rage yanayin gama gari na EMI.

Tabbas, haɗin da ke tsakanin layin samar da wutar lantarki da fil ɗin wutar lantarki na IC dole ne ya zama gajere kamar yadda zai yiwu, saboda tashin gefen siginar dijital yana da sauri da sauri.Yana da kyau a haɗa shi kai tsaye zuwa ga kushin inda aka samo fil ɗin wutar lantarki na IC, wanda ke buƙatar tattaunawa daban.

Domin sarrafa yanayin gama-gari na EMI, madaurin wutar lantarki dole ne ya zama gyare-gyaren nau'ikan nau'ikan wutar lantarki da aka ƙera don taimakawa ƙullawa da samun isassun ƙarancin inductance.Wasu mutane na iya tambaya, yaya kyau yake?Amsar ta dogara ne akan layin wutar lantarki, kayan da ke tsakanin yadudduka, da mitar aiki (watau aikin lokacin tashin IC).Gabaɗaya, tazarar yadudduka na wutar lantarki shine mil 6, kuma mai shiga tsakani abu ne na FR4, don haka madaidaicin ƙarfin kowane inci murabba'in na madaurin wuta kusan 75pF.Babu shakka, ƙarami tazarar Layer, mafi girma da capacitance.

Babu na'urori da yawa tare da lokacin tashi na 100-300ps, amma bisa ga ƙimar ci gaba na yanzu na IC, na'urorin da ke da lokacin tashi a cikin kewayon 100-300ps za su mamaye babban rabo.Don kewayawa tare da lokutan tashin 100 zuwa 300 PS, tazarar mil 3 ba ta da amfani ga yawancin aikace-aikace.A wannan lokacin, ya zama dole a yi amfani da fasahar delamination tare da tazarar interlayer kasa da 1mil, kuma maye gurbin FR4 dielectric abu tare da kayan tare da babban dielectric akai.Yanzu, yumbu da tukwane robobi na iya biyan buƙatun ƙira na 100 zuwa 300ps hawan lokacin da'irori.

Ko da yake ana iya amfani da sabbin kayayyaki da hanyoyin a nan gaba, na yau da kullun 1 zuwa 3 ns tashi lokaci da'irori, 3 zuwa 6 mil Layer tazarar, da FR4 dielectric kayan yawanci isa don sarrafa high-karshen jituwa da kuma yin transient sigina low isa, wato. , Yanayin gama gari EMI na iya ragewa sosai.A cikin wannan takarda, an ba da misalin ƙira na tarawar PCB, kuma ana ɗaukar tazarar Layer ya zama mil 3 zuwa 6.

garkuwar lantarki

Daga ra'ayi na siginar sigina, kyakkyawan dabarun shimfidawa ya kamata a sanya duk alamun sigina a cikin daya ko fiye da yadudduka, wanda ke kusa da layin wutar lantarki ko jirgin sama.Don samar da wutar lantarki, dabarun shimfidawa mai kyau ya kamata ya zama cewa layin wutar lantarki yana kusa da jirgin sama, kuma nisa tsakanin layin wutar lantarki da jirgin ƙasa ya kamata ya zama kadan kamar yadda zai yiwu, wanda shine abin da muke kira dabarun "laying".

PCB tari

Wane irin dabarar tari zai iya taimakawa garkuwa da murkushe EMI?Matsakaicin tari mai layi na gaba yana ɗauka cewa wutar lantarki tana gudana akan Layer guda ɗaya kuma ana rarraba wutar lantarki ɗaya ko maɗaukaki masu yawa a sassa daban-daban na Layer ɗaya.Za'a tattauna batun yadudduka masu yawa daga baya.

4-farantin karfe

Akwai wasu matsaloli masu yuwuwa a cikin ƙirar laminate 4-ply.Da farko, ko da siginar siginar yana cikin Layer na waje kuma wutar lantarki da jirgin ƙasa suna cikin Layer na ciki, nisa tsakanin layin wutar lantarki da jirgin ƙasa yana da girma sosai.

Idan abin da ake buƙata na farashi shine farkon, za a iya la'akari da zaɓuɓɓuka biyu masu zuwa ga al'adar al'ada 4-ply.Dukansu biyun suna iya haɓaka aikin hanawar EMI, amma sun dace ne kawai ga yanayin inda yawancin abubuwan da ke kan allon ke da ƙarancin isa kuma akwai isasshen yanki a kusa da abubuwan da aka haɗa (don sanya murfin jan ƙarfe da ake buƙata don samar da wutar lantarki).

Na farko shine makircin da aka fi so.Yadudduka na waje na PCB duk yadudduka ne, sai yadudduka biyu na tsakiya sigina / yaduddukan wuta.Ana yin amfani da wutar lantarki a kan siginar siginar tare da layi mai fadi, wanda ya sa hanyar da ake amfani da wutar lantarki a halin yanzu ta ragu da ƙananan siginar siginar microstrip.Daga hangen nesa na sarrafa EMI, wannan shine mafi kyawun tsarin PCB mai Layer 4 da ake samu.A cikin tsari na biyu, Layer na waje yana ɗaukar iko da ƙasa, kuma tsakiyar biyu yana ɗaukar siginar.Idan aka kwatanta da al'ada na al'ada 4-Layer, haɓakar wannan makirci ya fi ƙanƙanta, kuma tsaka-tsakin tsaka-tsakin ba shi da kyau kamar na gargajiya 4-Layer board.

Idan ana so a sarrafa magudanar wayoyi, tsarin tarawa na sama ya kamata a yi taka-tsan-tsan don sanya wayoyi a ƙarƙashin tsibirin jan ƙarfe na samar da wutar lantarki da ƙasa.Bugu da ƙari, tsibirin jan ƙarfe a kan samar da wutar lantarki ko stratum ya kamata a haɗa shi da haɗin kai kamar yadda zai yiwu don tabbatar da haɗin kai tsakanin DC da ƙananan mita.

Farantin karfe 6

Idan yawan abubuwan da aka gyara akan allon 4-Layer ya girma, farantin 6-Layer ya fi kyau.Koyaya, tasirin garkuwar wasu tsare-tsare a cikin ƙirar allo mai Layer 6 bai isa ba, kuma siginar bas ɗin wutar lantarki ba ta rage ba.An tattauna misalai biyu a ƙasa.

A cikin akwati na farko, ana sanya wutar lantarki da ƙasa a cikin layi na biyu da na biyar bi da bi.Saboda tsananin rashin ƙarfi na samar da wutar lantarki na jan karfe, ba shi da kyau a sarrafa yanayin gama gari na EMI radiation.Duk da haka, daga ra'ayi na sigina impedance iko, wannan hanya ne sosai daidai.

A cikin misali na biyu, ana sanya wutar lantarki da ƙasa a cikin layi na uku da na huɗu bi da bi.Wannan zane yana magance matsalar tagulla clad impedance na samar da wutar lantarki.Saboda ƙarancin aikin garkuwar lantarki na lantarki na Layer 1 da Layer 6, yanayin bambancin EMI yana ƙaruwa.Idan adadin siginar siginar akan manyan yadudduka na waje biyu shine mafi ƙanƙanta kuma tsayin layin yayi gajere sosai (kasa da 1/20 na mafi girman tsayin siginar jituwa), ƙirar zata iya magance matsalar yanayin yanayin EMI.Sakamakon ya nuna cewa dakatar da yanayin bambancin EMI yana da kyau musamman lokacin da Layer na waje ya cika da tagulla kuma yankin da aka rufe da tagulla yana ƙasa (kowane tazarar tsawon zangon 1/20).Kamar yadda aka ambata a sama, za a shimfiɗa tagulla


Lokacin aikawa: Yuli-29-2020