I-via lelinye lamacandelo abalulekileyo e-PCB ene-multi-layer, kwaye iindleko zokomba zidla ngokubalelwa kwi-30% ukuya kwi-40% yeendleko zebhodi yePCB. Ukubeka nje, wonke umngxuma kwi-PCB unokubizwa ngokuba yi-via.
Ingqikelelo esisiseko yendlela:
Ukusuka kwindawo yokujonga umsebenzi, i-via inokwahlulwa ibe ngamacandelo amabini: enye isetyenziselwa uxhulumaniso lombane phakathi kweengqimba, kwaye enye isetyenziselwa ukulungiswa okanye ukubeka isixhobo. Ukuba ukusuka kwinkqubo, le mingxunya yohlulwe ngokubanzi ngokweendidi ezintathu, ezizezi imingxuma eyimfama, imingxuma engcwatyiweyo kunye nemingxuma.
Imingxunya eyimfama ibekwe kwindawo ephezulu kunye nesezantsi kwibhodi yesekethe eprintiweyo kwaye inobunzulu obuthile bokudibanisa umphezulu wesekethe kunye nesekethe yangaphakathi engezantsi, kunye nobunzulu bemingxuma ngokuqhelekileyo ayidluli umlinganiselo othile (i-aperture).
Umngxuma ongcwatyiweyo ubhekisela kumngxuma wokudibanisa obekwe kwinqanaba elingaphakathi lebhodi yesekethe eprintiweyo, engagqithisi kumphezulu webhodi. Ezi ntlobo zimbini zingentla zemingxuma zibekwe kumaleko angaphakathi kwibhodi yesekethe, egqityezelwa yinkqubo yokubumba umngxuma phambi kokuba i-lamination, kunye nemigangatho emininzi yangaphakathi inokugqithelwa ngexesha lokusekwa komngxuma.
Uhlobo lwesithathu lubizwa ngokuba yimingxuma, edlula kuyo yonke ibhodi yesekethe kwaye ingasetyenziselwa ukuphumeza uqhagamshelo lwangaphakathi okanye njengemingxuma yokubeka indawo yamacandelo. Ngenxa yokuba umngxuma kulula ukufikelela kuwo kwinkqubo kwaye iindleko ziphantsi, uninzi lweebhodi zesekethe eziprintiweyo ziyayisebenzisa, kunokuba ezinye ezimbini zidlule ngemingxunya. Le mingxuma ilandelayo, ngaphandle kwemiyalelo ekhethekileyo, ithathwa njengemingxuma.
Ukusuka kwimbono yoyilo, i-via iqulunqwe ikakhulu ngamacandelo amabini, enye iphakathi komngxuma wokomba, kwaye enye yindawo yewelding ejikeleze umngxuma wokomba. Ubungakanani bala macandelo mabini bumisela ubungakanani be-via.
Ngokucacileyo, kwi-high-speed, i-PCB yoxinaniso oluphezulu, abaqulunqi bahlala befuna umngxuma ube mncinci kangangoko, ukuze kushiywe indawo yocingo engaphezulu, ukongeza, encinci i-via, i-parasitic capacitance incinci, ifaneleke ngakumbi. kwiisekethe ezinesantya esiphezulu.
Nangona kunjalo, ukucuthwa kwe-via size kuzisa ukunyuka kweendleko, kwaye ubungakanani bomngxuma abunakuncitshiswa ngokungenasiphelo, bukhawulelwe ngokugrumba kunye neteknoloji ye-electroplating: umngxuma omncinci, ixesha elide ukugrumba, kulula. kukutenxa embindini; Xa ubunzulu bomngxuma bungaphezu kwamaxesha ama-6 ububanzi bomngxuma, akunakwenzeka ukuqinisekisa ukuba udonga lomngxuma lunokufakwa ngokufanayo ngobhedu.
Umzekelo, ukuba ubukhulu (ngokusebenzisa ubunzulu bomngxuma) kwibhodi yePCB ene-6-layer eqhelekileyo yi-50Mil, ngoko ke ubuncinci bedayamitha yokugrumba abavelisi be-PCB abanokubonelela ngayo phantsi kweemeko eziqhelekileyo inokufikelela kuphela kwi-8Mil. Ngophuhliso lwetekhnoloji yokomba i-laser, ubungakanani bokomba bunokuba buncinci kwaye buncinci, kwaye ububanzi bomngxuma ngokuqhelekileyo bungaphantsi okanye bulingana ne-6Mils, sibizwa ngokuba yi-microholes.
I-Microholes idla ngokusetyenziswa kwi-HDI (isakhiwo soqhagamshelwano oluphezulu) kunye neteknoloji ye-microhole inokuvumela ukuba umngxuma uqhutywe ngokuthe ngqo kwi-pad, ephucula kakhulu ukusebenza kwesekethe kwaye igcine indawo yocingo. I-Via ibonakala njengekhefu lokuyeka ukunyanzeliswa kumgca wothumelo, kubangela ukubonakaliswa komqondiso. Ngokuqhelekileyo, ukunyanzeliswa okulinganayo komngxuma malunga ne-12% ephantsi kunomgca wothumelo, umzekelo, ukunyanzeliswa komgca wokuhanjiswa kwe-ohms ye-50 kuya kuncitshiswa nge-6 ohms xa idlula emngxunyeni (ngokukodwa kunye nobukhulu be-via, ukutyeba kwepleyiti nako kunxulumene, hayi ukuncitshiswa ngokupheleleyo).
Nangona kunjalo, imbonakalo ebangelwe kukungaqhubeki kwe-impedance ngenene incinci kakhulu, kwaye i-coefficient yayo yokubonisa kuphela:
(44-50)/(44 + 50) = 0,06
Iingxaki ezivela kwi-via zigxile ngakumbi kwiziphumo ze-parasitic capacitance kunye ne-inductance.
Via's Parasitic capacitance kunye ne-Inductance
Kukho i-parasitic stray capacitance kwi-via ngokwayo. Ukuba i-diameter yendawo yokumelana ne-solder kumaleko abekiweyo yi-D2, i-diameter ye-solder pad yi-D1, ubukhulu bebhodi ye-PCB yi-T, kunye ne-dielectric engaguqukiyo ye-substrate ngu-ε, i-parasitic capacitance yomngxuma odlulayo. imalunga:
C=1.41εTD1/(D2-D1)
Impembelelo ephambili ye-parasitic capacitance kwisekethe kukwandisa ixesha lokunyuka komqondiso kunye nokunciphisa isantya sesiphaluka.
Umzekelo, kwi-PCB enobunzima obuyi-50Mil, ukuba i-diameter ye-pad yi-20Mil (ububanzi bomngxuma wokugrumba yi-10Mils) kunye nobubanzi bendawo yokumelana ne-solder yi-40Mil, ngoko sinokuqikelela amandla e-parasitic ngale fomula ingentla:
C=1.41x4.4x0.050x0.020/(0.040-0.020)=0.31pF
Isixa sokutshintsha kwexesha lokunyuka okubangelwa yile nxalenye yesakhono siqikelelwa:
T10-90=2.2C(Z0/2)=2.2x0.31x(50/2)=17.05ps
Inokubonwa kula maxabiso ukuba nangona ukusetyenziswa kokulibaziseka kokunyuka okubangelwa yi-parasitic capacitance yendlela enye ayicacanga kakhulu, ukuba i-via isetyenziswa amatyeli amaninzi kumgca ukutshintshela phakathi kweeleya, imingxuma emininzi iya kusetyenziswa, kwaye uyilo kufuneka luqwalaselwe ngononophelo. Kuyilo lwangempela, i-parasitic capacitance ingancitshiswa ngokunyusa umgama phakathi komngxuma kunye nommandla wethusi (i-Anti-pad) okanye ukunciphisa ububanzi bepadi.
Kuyilo lweesekethe zedijithali ezikhawulezayo, umonakalo obangelwa yi-parasitic inductance idla ngokuba mkhulu kunempembelelo ye-parasitic capacitance. I-series yayo ye-parasitic inductance iya kwenza buthathaka igalelo le-bypass capacitor kwaye yenza buthathaka ukusebenza kakuhle kokucoca kwayo yonke inkqubo yamandla.
Singasebenzisa le fomula ilandelayo yobungqina ukubala ngokulula inductance yeparasitic yoqikelelo lomngxuma womngxuma:
L=5.08y[ln(4h/d)+1]
Apho u-L ebhekisa kwi-inductance ye-via, u-h bubude be-via, kwaye u-d bububanzi bomngxuma osembindini. Inokubonwa kwifomyula yokuba ububanzi bendlela bunempembelelo encinci kwi-inductance, ngelixa ubude bendlela bunempembelelo enkulu kwi-inductance. Usasebenzisa lo mzekelo ungasentla, i-inductance yangaphandle komngxuma ingabalwa ngolu hlobo:
L=5.08x0.050[ln(4x0.050/0.010)+1]=1.015nH
Ukuba ixesha lokunyuka kwesiginali yi-1ns, ngoko ke ubungakanani bayo obulinganayo bokuphazamiseka bu:
XL=πL/T10-90=3.19Ω
I-impedance enjalo ayinakuhoywa phambi kobukho be-high-frequency current ngokusebenzisa, ngokukodwa, qaphela ukuba i-bypass capacitor idinga ukudlula imingxuma emibini xa idibanisa umbane wamandla kunye nokwakheka, ukwenzela ukuba i-parasitic inductance yomngxuma iya kwandiswa.
Uyisebenzisa njani i-via?
Ngokusebenzisa uhlalutyo olungentla lweempawu zeparasitic zomngxuma, siyabona ukuba kuyilo lwePCB olunesantya esiphezulu, imingxunya ebonakala ilula idla ngokuzisa iziphumo ezibi kakhulu kuyilo lwesekethe. Ukuze kuncitshiswe iziphumo ezibi ezibangelwa yimpembelelo yeparasitic yomngxuma, uyilo lunokuba kangangoko kunokwenzeka:
Ukusuka kwimiba emibini yeendleko kunye nomgangatho wophawu, khetha ubungakanani obufanelekileyo besayizi. Ukuba kuyimfuneko, unokuqwalasela ukusebenzisa ubungakanani obuhlukeneyo be-vias, njengamandla ombane okanye imingxuma yocingo yomhlaba, unokuqwalasela ukusebenzisa ubungakanani obukhulu ukunciphisa i-impedance, kunye ne-wiring yesignali, ungasebenzisa encinci nge. Ewe, njengoko ubungakanani be-via buncipha, iindleko ezihambelanayo nazo ziya kunyuka
Ezi fomula zimbini zixoxiwe ngasentla zinokugqitywa ukuba ukusetyenziswa kwebhodi yePCB ebhityileyo kuyanceda ekunciphiseni iiparamitha ezimbini zeparasitic
Iingcingo zomqondiso kwibhodi yePCB akufuneki zitshintshwe kangangoko kunokwenzeka, oko kukuthi, zama ukungasebenzisi ii-vias ezingeyomfuneko.
I-Vias kufuneka igrunjwe kwizikhonkwane zobonelelo lwamandla kunye nomhlaba. Imfutshane isikhokelo phakathi kwezikhonkwane kunye ne-vias, ingcono. Imingxuma emininzi inokugrunjwa ngokuhambelanayo ukunciphisa inductance elinganayo.
Beka eminye imingxunya ebekwe kufutshane nemingxunya yokutshintsha komqondiso ukubonelela ngelophu ekufutshane yomqondiso. Ungade ubeke imingxuma engaphezulu komhlaba kwibhodi yePCB.
Kwiibhodi zePCB ezinesantya esiphezulu ezinoxinano oluphezulu, ungaqwalasela ukusebenzisa imingxunya emincinci.