Binyuze ni kimwe mu bintu by'ingenzi bigize PCB igizwe n’ibice byinshi, kandi ikiguzi cyo gucukura gikunze kuba 30% kugeza 40% byikiguzi cyubuyobozi bwa PCB. Muri make, umwobo wose kuri PCB urashobora kwitwa unyuze.
Igitekerezo cyibanze cya:
Duhereye ku mikorere, imikorere irashobora kugabanywamo ibyiciro bibiri: kimwe gikoreshwa nkumuyagankuba uhuza ibice, ikindi kigakoreshwa mugukosora cyangwa guhagarara kubikoresho. Niba bivuye mubikorwa, ibyo byobo bigabanijwemo ibyiciro bitatu, aribyo umwobo uhumye, umwobo ushyinguwe kandi unyuze mu mwobo.
Ibyobo bihumye biherereye hejuru no hepfo yububiko bwumuzingo wacapwe kandi bifite ubujyakuzimu runaka kugirango uhuze uruziga rwumuzingi hamwe nizunguruka ryimbere hepfo, kandi ubujyakuzimu bwibyobo ntibushobora kurenza igipimo runaka (aperture).
Umwobo washyinguwe bivuga umwobo uhuza uherereye murwego rwimbere rwibibaho byacapwe byacapwe, bitagera hejuru yubuyobozi. Ubwoko bubiri bwibyobo byavuzwe haruguru biri murwego rwimbere rwikibaho cyumuzunguruko, cyuzuzwa nuburyo bwo kubumba umwobo mbere yo kumurika, kandi ibice byinshi byimbere bishobora gutwikirwa mugihe cyo gushinga umwobo.
Ubwoko bwa gatatu bwitwa binyuze mu mwobo, unyura mu kibaho cyose cy’umuzunguruko kandi urashobora gukoreshwa kugirango ugere ku mikoranire yimbere cyangwa nkibikoresho byo kwishyiriraho ibice. Kuberako kunyura mu mwobo byoroshye kubigeraho murwego kandi igiciro kiri hasi, ubwinshi bwibibaho byacapwe byifashishwa, aho kubindi bibiri binyuze mumyobo. Imyobo ikurikira, idafite amabwiriza yihariye, ifatwa nko mu mwobo.
Uhereye ku gishushanyo mbonera, kunyuramo bigizwe ahanini n'ibice bibiri, kimwe ni hagati yumwobo, naho ikindi ni agace ko gusudira gakikije umwobo. Ingano yibi bice byombi igena ubunini bwa.
Ikigaragara ni uko mu muvuduko mwinshi, mwinshi cyane wa PCB, abashushanya bahora bifuza umwobo muto muto bishoboka, kugirango umwanya wiring ushobora gusigara, wongeyeho, ntoya unyuze, ubushobozi bwa parasitike yacyo ni nto, birakwiriye kumashanyarazi yihuta.
Nyamara, kugabanuka kunyuze mubunini nabyo bizana kwiyongera kwibiciro, kandi ubunini bwumwobo ntibushobora kugabanuka ubuziraherezo, bugarukira kubuhanga bwo gucukura no gukoresha amashanyarazi: uko umwobo muto, niko umwobo ufata, niko byoroshye. ni gutandukana kuva hagati; Iyo ubujyakuzimu bw'umwobo burenze inshuro 6 z'umurambararo, ntibishoboka kwemeza ko urukuta rw'umwobo rushobora gushyirwaho umuringa umwe.
Kurugero, niba umubyimba (unyuze mu mwobo) wububiko busanzwe bwa 6-PCB ni 50Mil, noneho diameter ntoya yo gucukura inganda za PCB zishobora gutanga mubihe bisanzwe zishobora kugera kuri 8Mil gusa. Hamwe niterambere rya tekinoroji yo gucukura laser, ingano yo gucukura nayo irashobora kuba nto kandi ntoya, kandi diameter yumwobo muri rusange iri munsi cyangwa ingana na 6Mil, twitwa microholes.
Microholes ikoreshwa kenshi mugushushanya kwa HDI (imiterere yubucucike bwinshi) Binyuze kugaragara nkibice byo guhagarika inzitizi kumurongo wohereza, bitera kwerekana ibimenyetso. Mubisanzwe, impingance ihwanye nu mwobo iri munsi ya 12% munsi yumurongo wogukwirakwiza, kurugero, inzitizi yumurongo wa 50 wa ohms izagabanywa na 6 oms iyo inyuze mumwobo (byumwihariko nubunini bwanyuze, ubunini bw'isahani nabwo bufitanye isano, ntabwo kugabanuka rwose).
Nyamara, ibitekerezo byatewe no guhagarika inzitizi binyuze mubyukuri ni bito cyane, kandi coefficente yayo yo kwerekana ni:
(44-50) / (44 + 50) = 0.06
Ibibazo biva muri kunyuramo byibanda cyane ku ngaruka za parasitike capacitance na inductance.
Binyuze mu bushobozi bwa Parasitike na Inductance
Hano hari ubushobozi bwa parasitike yataye inzira binyuze muri yo ubwayo. Niba umurambararo wa zone yo kugurisha kugurisha kumurongo washyizweho ni D2, diameter ya padiri yagurishijwe ni D1, ubunini bwikibaho cya PCB ni T, naho dielectric ihoraho ya substrate ni ε, ubushobozi bwa parasitike yinyuze mu mwobo ni hafi:
C = 1.41εTD1 / (D2-D1)
Ingaruka nyamukuru yubushobozi bwa parasitike kumuzunguruko ni ukongera igihe cyo kuzamuka kwikimenyetso no kugabanya umuvuduko wumuzunguruko.
Kurugero, kuri PCB ifite umubyimba wa 50Mil, niba diameter ya kunyura kuri padi ari 20Mil (diameter yumwobo wacukuwe ni 10Mils) na diameter ya zone yo kugurisha ni 40Mil, noneho dushobora kugereranya ubushobozi bwa parasitike ya i Binyuze kuri formula yavuzwe haruguru:
C = 1.41x4.4x0.050x0.020 / (0.040-0.020) = 0.31pF
Ingano yo kuzamuka kwigihe cyatewe niki gice cyubushobozi ni hafi:
T10-90 = 2.2C (Z0 / 2) = 2.2x0.31x (50/2) = 17.05ps
Birashobora kugaragara uhereye kuri izi ndangagaciro ko nubwo akamaro ko gutinda kuzamuka guterwa na parasitike capacitance yumuntu umwe unyuze ntabwo bigaragara cyane, niba unyuze ukoreshwa inshuro nyinshi kumurongo kugirango uhindure ibice, imyobo myinshi izakoreshwa, kandi igishushanyo kigomba gusuzumwa neza. Mu gishushanyo nyirizina, ubushobozi bwa parasitike burashobora kugabanuka mukongera intera iri hagati yumwobo nu gice cyumuringa (Anti-pad) cyangwa kugabanya diameter ya padi.
Mugushushanya imiyoboro yihuta yihuta ya digitale, ingaruka ziterwa na inductance ya parasitike akenshi iba myinshi kuruta imbaraga za parasitike. Inductance ya parasitike yayo izagabanya uruhare rwa capacitor ya bypass kandi igabanye imbaraga zo kuyungurura imikorere ya sisitemu yose.
Turashobora gukoresha formulaire yingirakamaro kugirango tubare gusa inductance ya parasitike yo kugereranya umwobo:
L = 5.08h [ln (4h / d) +1]
Aho L bivuga inductance yo kunyura, h nuburebure bwanyuze, na d ni diameter yumwobo wo hagati. Birashobora kugaragara uhereye kuri formula ko diameter ya kunyura idafite ingaruka nke kuri inductance, mugihe uburebure bwanyuze bugira uruhare runini kuri inductance. Ukoresheje urugero rwavuzwe haruguru, inductance yo mu mwobo irashobora kubarwa nka:
L = 5.08x0.050 [ln (4x0.050 / 0.010) +1] = 1.015nH
Niba igihe cyo kuzamuka kwikimenyetso ari 1ns, noneho ingano yacyo ihwanye ni:
XL = πL / T10-90 = 3.19Ω
Inzitizi nkiyi ntishobora kwirengagizwa imbere yumurongo wumuvuduko mwinshi unyuze, byumwihariko, menya ko capacitor ya bypass igomba kunyura mumyobo ibiri mugihe uhuza urwego rwamashanyarazi no gushingwa, kugirango inditike ya parasitike yu mwobo izagwira.
Nigute ushobora gukoresha?
Binyuze mu isesengura ryavuzwe haruguru ryerekana parasitike iranga umwobo, turashobora kubona ko muburyo bwihuse bwa PCB, ibyobo bisa nkibyoroshye akenshi bizana ingaruka mbi mubishushanyo mbonera. Kugirango ugabanye ingaruka mbi ziterwa na parasitike yumwobo, igishushanyo gishobora kuba kure cyane:
Uhereye kubintu bibiri byigiciro nubuziranenge bwibimenyetso, hitamo ingano yuzuye yubunini ukoresheje ubunini. Nibiba ngombwa, urashobora gutekereza gukoresha ubunini butandukanye bwa vias, nko gutanga amashanyarazi cyangwa umwobo wubutaka, urashobora gutekereza gukoresha ubunini bunini kugirango ugabanye inzitizi, kandi kubikoresho byo gukoresha ibimenyetso, urashobora gukoresha bito ukoresheje. Byumvikane ko, uko ubunini bwanyuze bugabanuka, igiciro kijyanye nacyo kiziyongera
Inzira ebyiri zaganiriweho hejuru zirashobora kwemezwa ko gukoresha ikibaho cyoroshye PCB bifasha kugabanya ibipimo bibiri bya parasitike byanyuze
Ikimenyetso cya signal ku kibaho cya PCB ntigomba guhinduka uko bishoboka kwose, nukuvuga, gerageza kudakoresha vias bitari ngombwa.
Vias igomba gucukurwa mumapine yumuriro nubutaka. Mugihe kigufi kiyobora hagati ya pin na vias, nibyiza. Imyobo myinshi irashobora gucukurwa murwego rwo kugabanya inductance ihwanye.
Shira bimwe byanyuze mu mwobo hafi yo kunyura mu bimenyetso byerekana ibimenyetso kugirango utange icyerekezo cyegereye ibimenyetso. Urashobora no gushyira ibyobo birenze urugero kubibaho bya PCB.
Kubuvuduko bwihuse bwa PCB hamwe nubucucike bwinshi, urashobora gutekereza gukoresha micro-umwobo.