Eyodwa. Umqondo oyisisekelo we-vias

I-Via ingenye yezingxenye ezibalulekile ze I-PCB ye-multilayer, futhi izindleko zokumba ngokuvamile zibalelwa ku-30% kuya ku-40% wezindleko zokukhiqiza ze-PCB. Kalula nje, yonke imbobo ku-PCB ingabizwa ngokuthi i-via.

Ngokombono wokusebenza, i-vias ingahlukaniswa ngezigaba ezimbili: eyodwa isetshenziselwa ukuxhumana kukagesi phakathi kwezingqimba; enye isetshenziselwa ukulungisa noma ukubeka izinto.

Ngokwenqubo, lawa ma-vias ngokuvamile ahlukaniswe izigaba ezintathu, okuyizimpumputhe, ama-vias angcwatshwa kanye nama-vias. Izimbobo eziyizimpumputhe zitholakala phezulu nangaphansi kwebhodi lesifunda eliphrintiwe futhi zinokujula okuthile. Zisetshenziselwa ukuxhuma umugqa ongaphezulu kanye nomugqa wangaphakathi ongaphansi. Ukujula komgodi ngokuvamile akudluli isilinganiso esithile (imbobo). Imbobo engcwatshiwe ibhekisela emgodini wokuxhuma otholakala kungqimba lwangaphakathi lwebhodi lesifunda eliphrintiwe, elingadluleli ebusweni bebhodi lesifunda. Lezi zinhlobo ezimbili zezimbobo ezibalwe ngenhla zitholakala kungqimba lwangaphakathi lwebhodi lesifunda, futhi ziqedwa ngenqubo yokwakhiwa kwe- through-hole ngaphambi kokuba lamination, futhi izingqimba eziningana kwangaphakathi kungase kudlulele ngesikhathi kumiswa via. Uhlobo lwesithathu lubizwa ngokuthi i- through hole , engena kulo lonke ibhodi lesifunda futhi ingasetshenziselwa ukuxhumana kwangaphakathi noma njengengxenye yokubeka imbobo. Ngenxa yokuthi i- through hole kulula ukuyisebenzisa kule nqubo futhi izindleko ziphansi, amabhodi esekethe amaningi aphrintiwe ayisebenzisa esikhundleni sezinye izinhlobo ezimbili zokusebenzisa izimbobo. Okulandelayo ngezimbobo, ngaphandle uma kuchazwe ngenye indlela, kuthathwa njengokudlula izimbobo.

Ngokombono wokuklama, i-via ngokuyinhloko yakhiwe izingxenye ezimbili, enye imbobo yokubhoboza phakathi, kanti enye iyindawo yephedi ezungeze umgodi wokubhoboza. Ubukhulu balezi zingxenye ezimbili bunquma ubukhulu be-via. Ngokusobala, ekwakhiweni kwe-PCB enesivinini esikhulu, enokuminyana okuphezulu, abaklami bahlala bethemba ukuthi i-via hole encane ingcono, ukuze kushiywe isikhala esiningi sezintambo ebhodini. Ngaphezu kwalokho, i-via hole encane, amandla e-parasitic ayo. Uma incane, ifaneleka kakhulu kumasekhethi anesivinini esikhulu. Kodwa-ke, ukuncishiswa kosayizi wembobo kuletha nokukhuphuka kwezindleko, futhi usayizi we-via awukwazi ukuncishiswa unomphela. Ivinjelwa ubuchwepheshe bezinqubo ezifana nokubhola nokucwenga: imbobo encane, i-drill Uma imbobo ithatha isikhathi eside, kuba lula ukuchezuka endaweni ephakathi; futhi lapho ukujula komgodi kudlula izikhathi ezingu-6 ububanzi bembobo ebhoboziwe, akunakuqinisekiswa ukuthi udonga lwembobo lungafakwa ngokufanayo ngethusi. Isibonelo, ukujiya (ngokujula kwembobo) kwebhodi le-PCB elinezingqimba ezi-6 ezivamile licishe libe ngu-50Mil, ngakho-ke ubukhulu obuncane bokubhoboza obunganikezwa abakhiqizi be-PCB bungafinyelela ku-8Mil kuphela.

Okwesibili, i-parasitic capacitance ye-via

I-via ngokwayo inamandla e-parasitic phansi. Uma kwaziwa ukuthi ububanzi bembobo ehlukanisiwe kungqimba lomhlabathi lwe-via yi-D2, ububanzi be-via pad ngu-D1, ubukhulu bebhodi le-PCB ngu-T, kanye ne-dielectric ye-substrate yebhodi ngu-ε, usayizi we-parasitic capacitance ye-via cishe: C=1.41εTD1/(D2-D1) Umthamo we-parasitic we-via uzobangela ukuthi isekethe yelule isikhathi sokukhuphuka kwesignali futhi yehlise isivinini sesekhethi. Isibonelo, ku-PCB enogqinsi oluyi-50Mil, uma kusetshenziswa i-via enobubanzi obungaphakathi obuyi-10Mil kanye nobubanzi bephedi obungu-20Mil, futhi ibanga phakathi kwephedi nendawo yethusi eliphansi lingama-32Mil, singase silinganisela usebenzisa ifomula engenhla Amandla e-parasitic cishe: C=1.41×4.4×0.050×0.020/(0.032-0.020)=0.517pF, ukushintsha kwesikhathi sokukhuphuka okubangelwa yile ngxenye yamandla yilokhu: T10-90=2.2C(Z0) /2)=2.2 x0.517x(55/2)=31.28ps. Kungabonakala kulawa manani ukuthi nakuba umthelela wokulibaziseka kokukhuphuka okubangelwa amandla e-parasitic wendlela eyodwa ungabonakali, uma i- via isetshenziswa izikhathi eziningi ekulandeleni ukushintsha phakathi kwezendlalelo, umklami kusafanele acabangele. ngokucophelela.

Okwesithathu, i-parasitic inductance ye-via

Ngokufanayo, kukhona ama-parasitic inductances kanye ne-parasitic capacitance ye-vias. Ekuklanyweni kwamasekhethi edijithali anesivinini esikhulu, umonakalo obangelwa i-parasitic inductance ye-vias ngokuvamile mkhulu kunomthelela we-parasitic capacitance. Uchungechunge lwayo lwe-parasitic inductance luzokwenza buthaka umnikelo we-bypass capacitor futhi lwenze buthaka umphumela wokuhlunga walo lonke uhlelo lwamandla. Singamane sibale isilinganiso sokungena kwe-a via ngefomula elandelayo: L=5.08h[ln(4h/d)+1] lapho u-L ebhekisela ekungeneni kwe-via, h ubude be-via, futhi d iyisikhungo Ububanzi bomgodi. Kungabonakala kufomula ukuthi ububanzi be-via bunomthelela omncane ku-inductance, futhi ubude be-via bunomthelela omkhulu kakhulu ku-inductance. Usasebenzisa isibonelo esingenhla, inductance ye-via ingabalwa ngokuthi: L=5.08×0.050 [ln(4×0.050/0.010)+1]=1.015nH. Uma isikhathi sokukhuphuka kwesignali singu-1ns, i-impedance yayo efanayo ithi: XL=πL/T10-90=3.19Ω. I-impedance enjalo ngeke isakwazi ukushaywa indiva lapho ama-high-frequency currents edlula. Ukunakwa okukhethekile kufanele kukhokhwe eqinisweni lokuthi i-bypass capacitor idinga ukudlula ama-vias amabili lapho ixhuma indiza yamandla kanye nendiza yaphansi, ukuze inductance ye-parasitic ye-vias izokwanda ngokuqhubekayo.

Okwesine, ngokuklama ku-PCB enesivinini esikhulu

Ngokuhlaziywa okungenhla kwezici ze-vias, singabona ukuthi ekwakhiweni kwe-PCB enesivinini esikhulu, ama-vias abonakala elula ngokuvamile aletha imiphumela emibi kakhulu ekwakhiweni kwesekethe. Ukuze unciphise imiphumela emibi ebangelwa imiphumela ye-parasitic ye-vias, okulandelayo kungenziwa ekwakhiweni:

1. Ngokombono wezindleko nekhwalithi yesiginali, khetha usayizi ozwakalayo usebenzisa. Isibonelo, ngomklamo we-PCB wemojula ye-6-10, kungcono ukusebenzisa i-10/20Mil (i-drilled/pad) vias. Kwamanye amabhodi anosayizi omncane anobukhulu obukhulu, ungaphinda uzame ukusebenzisa u-8/18Mil. umgodi. Ngaphansi kwezimo zamanje zobuchwepheshe, kunzima ukusebenzisa ama-vias amancane. Ukuze uthole amandla noma i-vias yomhlabathi, ungacabangela ukusebenzisa usayizi omkhulu ukuze unciphise i-impedance.

2. Amafomula amabili okukhulunywe ngawo ngenhla angaphethwa ngokuthi ukusetshenziswa kwe-PCB ezacile kusiza ekwehliseni amapharamitha amabili we-via.

3. Zama ukungashintshi izendlalelo zezimpawu zezimpawu ebhodini le-PCB, okusho ukuthi, zama ukungasebenzisi ama-vias angadingekile.

4. Amandla nezikhonkwane zomhlabathi kufanele zibhojwe eduze, futhi ukuhola phakathi kwe-via nephini kufanele kube kufushane ngangokunokwenzeka, ngoba kuzokwandisa i-inductance. Ngesikhathi esifanayo, amandla kanye nemikhondo yomhlabathi kufanele ibe mkhulu ngangokunokwenzeka ukuze kuncishiswe i-impedance.

5. Beka i-vias ethile eduze kwe-vias yongqimba lwesignali ukuze unikeze iluphu eseduze yesiginali. Kungenzeka ngisho nokubeka inombolo enkulu yezindawo ezingasasebenzi ebhodini le-PCB. Yiqiniso, umklamo udinga ukuguquguquka. Imodeli okuxoxwe ngayo ngaphambili yisimo lapho kukhona amaphedi kusendlalelo ngasinye. Ngezinye izikhathi, singanciphisa noma sisuse ngisho namaphedi kwezinye izendlalelo. Ikakhulukazi lapho ukuminyana kwe-vias kuphezulu kakhulu, kungase kuholele ekwakhekeni kwe-break groove ehlukanisa iluphu kungqimba lwethusi. Ukuxazulula le nkinga, ngaphezu kokuhambisa isikhundla se-via, singacabanga nokubeka i-via kungqimba lwethusi. Usayizi wephedi uncishisiwe.