Iyo via imwe yezvakakosha zvikamu zve-multi-layer PCB, uye mutengo wekuchera unowanzo verengera 30% kusvika 40% yemutengo wePCB board.Zvichitaurwa zviri nyore, gomba rega rega paPCB rinogona kunzi via.
The basic concept of the via:
Kubva pamaonero ebasa, iyo via inogona kukamurwa kuita mapoka maviri: imwe inoshandiswa semagetsi ekubatanidza pakati pematanho, uye imwe yacho inoshandiswa sekugadzirisa kana kumira kwechishandiso.Kana kubva mukuita, makomba aya anowanzo kupatsanurwa muzvikamu zvitatu, zvinoti mapofu mapofu, makomba akavigwa uye kuburikidza nemakomba.
Mabofu maburi anowanikwa pamusoro uye pasi pepamusoro pebhodhi redunhu rakadhindwa uye ane humwe hudzamu hwekubatana kwedunhu repamusoro uye remukati redunhu pazasi, uye kudzika kwemakomba kazhinji hakupfuuri imwe reshiyo (aperture).
Gomba rakavigwa rinoreva gomba rekubatanidza riri muchikamu chemukati chebhodhi rakadhindwa redunhu, iro risingapfuuri kumusoro kwebhodhi.Idzi dziri pamusoro pemhando mbiri dzemakomba dziri muchikamu chemukati chebhodhi redunhu, iro rinopedzwa ne kuburikidza negomba rekuumba nzira isati yasvika, uye zvidimbu zvakawanda zvemukati zvinogona kupindirana panguva yekuumbwa kweburi.
Mhando yechitatu inonzi kuburikidza-maburi, iyo inopfuura nepakati pese redunhu bhodhi uye inogona kushandiswa kuwana yemukati yekubatanidza kana sekuisa nzvimbo yekuisa maburi ezvikamu.Nekuti iyo kuburikidza neburi iri nyore kuwana mukuita uye mutengo wakaderera, ruzhinji rweakadhindwa edunhu mabhodhi anoishandisa, pane mamwe maviri kuburikidza nemakomba.Makomba anotevera, pasina mirairo yakakosha, anoonekwa semaburi.
Kubva pamagadzirirwo ekuona, via via anonyanya kuumbwa nezvikamu zviviri, chimwe chiri pakati pegomba rekuchera, uye imwe yacho inzvimbo yewelding pad yakatenderedza gomba rekuchera.Saizi yezvikamu zviviri izvi inosarudza saizi ye via.
Zviripachena, mune yakakwirira-kumhanya, yakakwira-density PCB dhizaini, vagadziri vanogara vachida gomba sediki sezvinobvira, kuitira kuti nzvimbo yakawanda ye wiring irege kusiiwa, nekuwedzera, iyo diki via, yayo parasitic capacitance idiki, yakakodzera zvakanyanya. kumatunhu anomhanya-mhanya.
Nekudaro, kudzikiswa kweiyo via size kunounzawo kuwedzera kwemitengo, uye saizi yegomba haigone kudzikiswa nekusingaperi, inoganhurwa nekuchera uye electroplating tekinoroji: iyo gomba diki, iyo yakareba kuchera kunotora, kunova nyore ndiko kutsauka kubva pakati;Kana kudzika kwegomba kunopfuura katanhatu pahupamhi hwegomba, hazvibviri kuve nechokwadi kuti rusvingo rwegomba runogona kuiswa zvakafanana nemhangura.
Semuyenzaniso, kana ukobvu (kuburikidza negomba kudzika) kweyakajairwa 6-layer PCB board iri 50Mil, ipapo iyo shoma yekuchera dhayamita iyo PCB vagadziri vanogona kupa mumamiriro ezvinhu akajairika inogona kungosvika 8Mil.Nekuvandudzwa kwelaser drilling tekinoroji, saizi yekuchera inogona zvakare kuve idiki uye idiki, uye iyo dhayamita yegomba kazhinji isingasviki kana kuenzana ne6Mils, isu tinodaidzwa microholes.
Microholes inowanzoshandiswa muHDI (yakakwirira density interconnect structure) dhizaini, uye microhole tekinoroji inogona kubvumira gomba kuti riburitswe zvakananga padhi, iyo inovandudza zvakanyanya mashandiro edunhu uye inochengetedza nzvimbo yewaya.Iyo via inoratidzika senge yekutyora kwe impedance discontinuity pamutsara wekutapurirana, zvichikonzera kuratidzwa kwechiratidzo.Kazhinji, iyo yakaenzana impedance yegomba inenge 12% yakaderera pane tambo yekufambisa, semuenzaniso, iyo impedance ye50 ohms transmission line ichaderedzwa ne6 ohms kana ichipfuura nepagomba (chaizvo uye saizi ye via, kukora kweplate kunobatanidzwawo, kwete kudzikisira zvachose).
Nekudaro, iyo ratidziro yakakonzerwa neiyo impedance discontinuity kuburikidza idiki kwazvo, uye iyo yekuratidzira coefficient ndeye chete:
(44-50)/(44 + 50) = 0.06
Matambudziko anomuka kubva kuVia anonyanya kutarisana nemhedzisiro yeparasitic capacitance uye inductance.
Via's Parasitic capacitance uye Inductance
Pane parasitic rakarasika capacitance mune via pachayo.Kana iyo dhayamita yenzvimbo yekupikisa solder pane yakagadzikwa iri D2, iyo dhayamita ye solder pad iri D1, ukobvu hwePCB board iT, uye dielectric kugara kweiyo substrate iri ε, iyo parasitic capacitance ye kuburikidza negomba. ingangoita:
C=1.41εTD1/(D2-D1)
Mhedzisiro huru yeparasitic capacitance padunhu ndeyekuwedzera nguva yekusimuka kwechiratidzo uye kuderedza kukurumidza kwedunhu.
Semuyenzaniso, yePCB ine hukobvu hwe50Mil, kana dhayamita yeVia pad iri 20Mil (dhayamita regomba rekuchera iri 10Mils) uye dhayamita renzvimbo inopikisa solder iri 40Mil, saka tinogona kufungidzira kugona kweparasitic. kuburikidza neformula iri pamusoro:
C=1.41x4.4x0.050x0.020/(0.040-0.020)=0.31pF
Huwandu hwekusimuka kwekuchinja kwenguva kunokonzerwa nechikamu ichi che capacitance inenge:
T10-90=2.2C(Z0/2)=2.2x0.31x(50/2)=17.05ps
Zvinogona kuonekwa kubva pane izvi zvakakosha kuti kunyange zvazvo kushandiswa kwekunonoka kunokonzerwa neparasitic capacitance yeimwe nzira haisi pachena, kana iyo via inoshandiswa kakawanda mumutsara kuchinja pakati pezvikamu, maburi akawanda achashandiswa, uye magadzirirwo acho anofanira kunyatsotariswa.Muchigadziro chaicho, iyo parasitic capacitance inogona kuderedzwa nekuwedzera kureba pakati pegomba nenzvimbo yemhangura (Anti-pad) kana kuderedza dhayamita yepedhi.
Mukugadzirwa kwepamusoro-speed digital circuits, kukuvadza kunokonzerwa neparasitic inductance kunowanzova kukuru kudarika simba reparasitic capacitance.Iyo parasitic series inductance inoderedza mupiro weiyo bypass capacitor uye kuderedza kushanda kwesefa kwesimba rose resimba.
Isu tinogona kushandisa inotevera empirical formula kungoverenga iyo parasitic inductance yekupfuura-gomba fungidziro:
L=5.08h[ln(4h/d)+1]
Apo L inoreva kudhonzwa kwe via, h ndiko kureba kwe via, uye d ndiko kureba kwegomba repakati.Zvinogona kuoneka kubva kuformula kuti dhayamita yeVia haina pesvedzero paiyo inductance, nepo kureba kweiyo via kune pesvedzero huru pane inductance.Uchiri kushandisa muenzaniso wepamusoro, iyo-ye-hole inductance inogona kuverengerwa se:
L=5.08x0.050[ln(4x0.050/0.010)+1]=1.015nH
Kana nguva yekusimuka kwechiratidzo iri 1ns, saka yakaenzana impedance saizi ndeye:
XL=πL/T10-90=3.19Ω
Iyo impedance yakadaro haigone kufuratirwa pamberi peiyo yakakwira-frequency ikozvino kuburikidza, kunyanya, cherechedza kuti bypass capacitor inoda kupfuura nemakomba maviri kana ichibatanidza simba layer uye kuumbwa, kuitira kuti parasitic inductance yegomba iwande.
Nzira yekushandisa sei via?
Kuburikidza nekuongororwa kwepamusoro kwemaitiro eparasitic egomba, tinogona kuona kuti mukumhanya kwePCB dhizaini, maburi anoita seakareruka anowanzo kuunza mhedzisiro yakaipa padhizaini yedunhu.Kuti uderedze mhedzisiro inokonzerwa neparasitic mhedzisiro yegomba, dhizaini inogona kunge iri kure sezvinobvira:
Kubva pamativi maviri emutengo uye chiratidzo chemhando, sarudza saizi inonzwisisika yeiyo via saizi.Kana zvakakodzera, unogona kufunga kushandisa siyana hukuru vias, akadai simba rekupa kana pasi waya makomba, unogona kufunga kushandisa hombe saizi kuderedza impedance, uye nokuda chiratidzo wiring, unogona kushandisa diki via.Ehe, sezvo saizi yeVia inodzikira, mutengo unoenderana uchawedzerawo
Iwo maviri mafomula akurukurwa pamusoro anogona kugumiswa kuti kushandiswa kweakatetepa PCB board kunobatsira kudzikisa maviri parasitic paramita ye.
Iyo yechiratidzo wiring paPCB board haifanirwe kuchinjwa sezvingabvira, kureva kuti, edza kusashandisa zvisina kufanira vias.
Vias inofanira kurovererwa mumapini emagetsi uye pasi.Iyo ipfupi inotungamira pakati pepini uye vias, zviri nani.Makomba akawanda anogona kudhiriwa anoenderana kudzikisa yakaenzana inductance.
Isa mamwe maburi pedyo nemaburi echiratidzo chekuchinja kuti upe loop iri pedyo yechiratidzo.Iwe unogona kutoisa mamwe maburi epasi akawandisa paPCB board.
Kune yakakwirira kumhanya PCB mabhodhi ane yakakwirira density, unogona kufunga kushandisa micro-maburi.