Poshi. Pfungwa yekutanga ye vias

Via ndechimwe chezvinhu zvakakosha zve multilayer pcb, uye mari yekuchera inowanzoita 30% kusvika 40% yePCB yekugadzira mutengo. Zvichitaurwa zviri nyore, gomba rega rega paPCB rinogona kunzi via.

Kubva pakuona kwebasa, vias inogona kugoverwa muzvikamu zviviri: imwe inoshandiswa pakubatanidza magetsi pakati pezvikamu; imwe yacho inoshandiswa kugadzirisa kana kuisa midziyo.

Panyaya muitiro, vias izvi kazhinji akakamurwa muzvikamu zvitatu, kureva bofu vias, akavigwa vias uye kuburikidza vias. Mabofu maburi anowanikwa pamusoro uye pasi pepamusoro pebhodhi redunhu rakadhindwa uye ane humwe hudzamu. Izvo zvinoshandiswa kubatanidza mutsara wepamusoro uye mutsara uri pasi wemukati. Kudzika kwegomba kazhinji hakupfuuri imwe chiyero (aperture). Gomba rakavigwa rinoreva gomba rekubatanidza riri muchikamu chemukati chebhodhi redunhu rakadhindwa, risingapfuuri kumusoro kwebhodhi redunhu. Mhando mbiri dzataurwa pamusoro apa dzemaburi dziri muchikamu chemukati chebhodhi redunhu, uye dzinopedzwa neburi-gomba rekugadzira nzira isati yave lamination, uye akati wandei emukati akaturikidzana anogona kupindirana panguva yekuumbwa kweiyo via. Rudzi rwechitatu runodanwa kuburikidza negomba, iro rinopinda mukati mese redunhu bhodhi uye rinogona kushandiswa mukati mekubatana kana sechikamu chinomisikidza gomba. Nekuti iyo kuburikidza neburi iri nyore kushandisa mukuita uye mutengo wakaderera, mazhinji akadhindwa edunhu mabhodhi anoishandisa pachinzvimbo chemamwe marudzi maviri epamaburi. Zvinotevera nemaburi, kunze kwekunge zvatsanangurwa neimwe nzira, zvinotorwa semaburi.

Kubva padhizaini yekuona, via via inonyanya kuumbwa nezvikamu zviviri, imwe igomba rekuboora pakati, uye imwe inzvimbo yepadhi yakatenderedza gomba rekuchera. Saizi yezvikamu zviviri izvi inosarudza saizi yevia. Zviripachena, mune yakakwirira-kumhanya, yakakwirira-density PCB dhizaini, vagadziri vanogara vachitarisira kuti iyo diki kuburikidza negomba iri, zviri nani, kuitira kuti yakawanda wiring nzvimbo inogona kusiiwa pabhodhi. Mukuwedzera, iyo diki iyo via gomba, iyo parasitic capacitance yayo. Iyo diki iyo, iyo inonyanya kukodzera kune yakakwirira-speed circuits. Nekudaro, kudzikiswa kwegomba saizi kunounzawo kuwedzera kwemutengo, uye saizi yeVia haigone kudzikiswa nekusingaperi. Inodziviswa nehunyanzvi hwekuita senge kuchera uye plating: diki gomba, drill Iyo yakareba gomba inotora, zviri nyore kutsauka kubva panzvimbo yepakati; uye kana kudzika kwegomba kuchipfuura 6 nguva yehupamhi hwegomba rakacherwa, haigoni kuvimbiswa kuti rusvingo rwegomba runogona kuiswa zvakafanana nemhangura. Semuyenzaniso, ukobvu (kuburikidza negomba kudzika) kweyakajairwa 6-layer PCB board inenge 50Mil, saka dhayamita diki yekuchera iyo PCB vanogadzira inogona kungosvika 8Mil.

Chechipiri, iyo parasitic capacitance yeiyo via

Iyo via pachayo ine parasitic capacitance pasi. Kana zvichizivikanwa kuti dhayamita yegomba rekuzviparadzanisa riri pazasi pedhiza iri D2, iyo dhayamita yepadhi iri D1, ukobvu hwePCB board ndiT, uye dielectric kugara kwebhodhi substrate iri ε, saizi yeparasitic capacitance yeVia inenge: C = 1.41εTD1 / (D2-D1) Iyo parasitic capacitance ye via ichaita kuti dunhu riwedzere nguva yekusimuka kwechiratidzo uye kuderedza kumhanya kwedunhu. Semuenzaniso, yePCB ine hukobvu hwe50Mil, kana via ine dhayamita yemukati ye10Mil uye padhi dhayamita ye20Mil yakashandiswa, uye chinhambwe chiri pakati pepadhi nenzvimbo yemhangura yepasi i32Mil, ipapo tinogona kufungidzira. uchishandisa iyo fomula iri pamusoro Iyo parasitic capacitance inokwana: C = 1.41 × 4.4 × 0.050 × 0.020/ (0.032-0.020) = 0.517pF, kusimuka kwenguva kushanduka kunokonzerwa nechikamu ichi che capacitance: T10-90 = 2.2C (Z0) /2)=2.2 x0.517x(55/2)=31.28ps. Zvinogona kuonekwa kubva pane izvi zvakakosha kuti kunyangwe mhedzisiro yekunonoka kusimuka kunokonzerwa neiyo parasitic capacitance yeimwe chete isiri pachena, kana iyo via yakashandiswa kakawanda mukutsvaga kuchinja pakati pezvikamu, mugadziri anofanira kuramba achifunga. nokungwarira.

Chechitatu, iyo parasitic inductance yeiyo via

Saizvozvo, pane parasitic inductances pamwe parasitic capacitance we vias. Mukugadzirwa kwepamusoro-kumhanya dhijitari maseketi, kukuvadzwa kunokonzerwa neparasitic inductance ye vias kazhinji kunopfuura kukanganisa kweparasitic capacitance. Yayo parasitic series inductance inoderedza mupiro weiyo bypass capacitor uye inonetesa kusefa kweiyo yese simba system. Tinogona kungoverenga fungidziro yeparasitic inductance ye via neinotevera fomula: L=5.08h[ln(4h/d)+1] apo L inoreva kudhonzwa kwenzira, h kureba kwenzira, uye d. ndiro pakati The dhayamita yegomba. Iyo inogona kuoneka kubva kuformula kuti dhayamita yeVia ine diki pesvedzero pane inductance, uye kureba kweiyo via kune pesvedzero huru pane inductance. Uchiri kushandisa muenzaniso wepamusoro, inductance yeiyo via inogona kuverengerwa se: L=5.08×0.050 [ln(4×0.050/0.010)+1]=1.015nH. Kana nguva yekusimuka kwechiratidzo iri 1ns, saka yakaenzana impedance ndeye: XL=πL/T10-90=3.19Ω. Impedance yakadaro haichagone kufuratirwa kana ma-high-frequency currents anopfuura. Kunyanya kucherechedzwa kunofanira kubhadharwa kune chokwadi chekuti bypass capacitor inoda kupfuura nepakati peviri kana ichibatanidza simba rendege uye ndege yepasi, kuitira kuti parasitic inductance ye vias iwedzere exponentially.

Chechina, kuburikidza nedhizaini mune yakakwirira-kumhanya PCB

Kuburikidza pamusoro ongororo pamusoro parasitic unhu vias, tinogona kuona kuti mukuru-nokukurumidza PCB dhizaini, zvinoita sokuti nyore vias kazhinji kuunza guru migumisiro yakaipa kuti redunhu magadzirirwo. Kuti uderedze mhedzisiro inokonzerwa neparasitic mhedzisiro yevias, zvinotevera zvinogona kuitwa mukugadzira:

1. Kubva pamaonero emutengo uye chiratidzo chemhando, sarudza saizi inonzwisisika kuburikidza. Semuenzaniso, ye6-10 layer memory module PCB dhizaini, zviri nani kushandisa 10/20Mil (yakadhirowa/pedhi) vias. Kune mamwe akakwira-density madiki-saizi mabhodhi, unogona zvakare kuedza kushandisa 8/18Mil. gomba. Pasi pezvino tekinoroji mamiriro, zvakaoma kushandisa diki vias. Nokuti simba kana pasi vias, unogona kufunga kushandisa hombe saizi kuderedza impedance.

2. Mafomu maviri akakurukurwa pamusoro apa anogona kugumiswa kuti kushandiswa kwePCB yakaonda kunobatsira kuderedza maparasitic parameters maviri e via.

3. Edza kusachinja zvidimbu zvechiratidzo chechiratidzo paPCB board, kureva kuti, edza kusashandisa vias zvisingakoshi.

4. Simba uye mapini epasi anofanira kudonhedzwa pedyo, uye mutungamiri pakati pe via nepini anofanira kunge akapfupika sezvinobvira, nokuti achawedzera inductance. Panguva imwecheteyo, simba uye pasi rinotungamira rinofanira kunge rakakora sezvinobvira kuderedza impedance.

5. Isa dzimwe vias pasi pedyo vias pamusoro chiratidzo layer kuti ape pedyo loop nokuda chiratidzo. Izvo zvinotogoneka kuisa nhamba huru yepasi rese vias paPCB board. Zvechokwadi, dhizaini inoda kuchinjika. Iyo via modhi yakakurukurwa pakutanga ndiyo nyaya uko kune mapedhi pane imwe neimwe layer. Dzimwe nguva, isu tinokwanisa kuderedza kana kubvisa mapadhi emamwe maseru. Kunyanya kana density ye vias yakakwira kwazvo, inogona kutungamirira kukugadzirwa kwegororo rinoparadzanisa chiuno mumhangura yemhangura. Kugadzirisa dambudziko iri, pamusoro pekufambisa chinzvimbo cheiyo via, isu tinogona zvakare kufunga nezvekuisa iyo via pane yemhangura layer. Saizi yepadhi yakaderedzwa.