Kuyini ukulawula impedance nokuthi ungakwenza kanjani ukulawula impedance kuma-PCB

Ekwakhiweni kwamadivayisi kagesi esimanje, ama-PCB adlala indima ebalulekile. Ukusebenza kwama-PCB kuthinta ngqo ukuzinza, ukuthembeka kanye nokusebenza kahle kokudlulisa uhlelo lonke lwe-elekthronikhi. Phakathi kwawo, ukulawulwa kwe-impedance kuyingxenye ebalulekile yokuklama kwe-PCB. Njengoba amasekethe edijithali esimanje anezikhathi ezimfushane zokudlulisa isignali kanye namazinga aphezulu ewashi, ama-trace e-PCB awaseyona ukuxhumana okulula, kodwa imigqa yokudlulisa ngokufanayo. Ukulawulwa kwe-impedance ye-PCB kubhekisela ekulawuleni ijubane lokudlulisa kanye nokuqhathaniswa kwe-impedance kwezimpawu ku-PCB ukuqinisekisa ikhwalithi kanye nokuqina kokudluliselwa kwesignali.

Ezimweni ezingokoqobo, kuyadingeka ukulawula i-trace impedance lapho ijubane ledijithali elingaphansi liphakeme kune-1ns noma imvamisa ye-analog idlula i-300MHz. Enye yamapharamitha abalulekile e-PCB trace yi-impedance yayo ephawulekayo (okungukuthi isilinganiso se-voltage kuya kumanje lapho igagasi lidluliselwa emgqeni wokudlulisa isignali). I-impedance ephawulekayo yezintambo kuma-PCB iyinkomba ebalulekile yomklamo we-PCB. Ikakhulukazi ekwakhiweni kwe-PCB evame kakhulu, kuyadingeka ukucabangela ukuthi i-impedance ephawulekayo yentambo iyahambisana noma iyafana ne-impedance edingekayo yedivayisi noma isignali. Lokhu kuhilela imiqondo emibili: ukulawula i-impedance kanye nokufanisa i-impedance. Lesi sihloko sigxile ezindabeni zokulawula i-impedance kanye nomklamo we-stack.

Kunezibonakaliso ezahlukahlukene ezidluliselwa kubaqhubi be-PCB. Ukuze kuthuthukiswe izinga lokudlulisa kwayo, imvamisa yayo kumele ikhuliswe. Inani le-impedance yesekethe ngokwayo liyahlukahluka ngenxa yezici ezifana nokusika, ukujiya kwesendlalelo kanye nobubanzi bentambo, njll., okubangela ukuphambuka kwesignali. Ngakho-ke, inani le-impedance labaqhubi kuma-PCB anesivinini esikhulu kufanele lilawulwe ngaphakathi kobubanzi obuthile, obubizwa ngokuthi "ukulawula i-impedance".

Ukuvinjelwa kwezimpawu ze-PCB kunqunywa yi-inductance yazo ekhuthazayo nenamandla, ukumelana kanye ne-coefficient yokuqhuba. Izici ezithinta ukuvinjelwa kwezintambo ze-PCB zifaka phakathi ububanzi kanye nobukhulu bentambo yethusi, ukungaguquguquki kwe-dielectric kanye nobukhulu be-medium, ukujiya kwephedi yokushintsha, indlela yentambo yomhlabathi, kanye nokuxhumana okuzungeze izintambo, njll. Ububanzi bokuxhumana kwe-PCB bungama-ohms angu-25 kuya kwangu-120.

Empeleni, imigqa yokudlulisa ye-PCB ngokuvamile iqukethe umkhondo wentambo, izendlalelo ezibhekiselwe kuzo eyodwa noma ngaphezulu, kanye nezinto zokufaka umswakama. Umkhondo kanye nesendlalelo kwakha impedance yokulawula. Ama-PCB avame ukusebenzisa izakhiwo ezinezendlalelo eziningi, futhi ukulawula impedance nakho kungakhiwa ngezindlela ezahlukahlukene. Kodwa-ke, kungakhathaliseki ukuthi iyiphi indlela esetshenzisiwe, inani lempedance lizonqunywa yisakhiwo sayo esibonakalayo kanye nezakhiwo ze-elekthronikhi zezinto zokufaka umswakama:

I-microstrip iyisiqeshana sentambo esibhekisela entanjeni yokudlulisa enohlangothi olulodwa kuphela olunendiza yokubhekisela. Ingaphezulu nezinhlangothi zivezwa emoyeni (noma zimbozwe) futhi zitholakala ebusweni be-PCB ye-insulation engaguquki, ene-power noma ungqimba lomhlabathi njengereferensi. Njengoba kuboniswe esithombeni esilandelayo:

Qaphela: Ekwenziweni kwe-PCB yangempela, ifektri ye-PCB ivame ukumboza ungqimba lweyinki eluhlaza ebusweni be-PCB. Ngakho-ke, ekubalweni kwangempela kwe-impedance, imodeli eboniswe esithombeni esilandelayo ivame ukusetshenziselwa imigqa ye-microstrip engaphezulu.

Umugqa wentambo uwumugqa wentambo obekwe phakathi kwezindiza ezimbili zokubhekisela, njengoba kuboniswe esithombeni esilandelayo. Ama-dielectric constants e-dielectric amelwe yi-H1 ne-H2 angahluka.

Amacala amabili angenhla ayisibonelo esijwayelekile se-microstrip kanye ne-striplines, ngokuvamile esetshenziselwa ukufunda ihadiwe ehlakaniphile ye-IoT ehlanganisiwe kanye nezinye izinhlelo. Kunezinhlobo eziningi ezithile ze-microstrip kanye ne-striplines, njenge-microstrip ehlanganisiwe, ezihlobene nesakhiwo esithile sokufaka ama-PCB.

I-equation esetshenziselwa ukubala i-characteristic impedance idinga izibalo eziyinkimbinkimbi zezibalo, ngokuvamile kusetshenziswa izindlela zokuxazulula insimu, okuhlanganisa nokuhlaziywa kwezakhi zomngcele. Ngakho-ke, ngokusebenzisa isofthiwe yokubala i-impedance ekhethekile i-SI9000, okudingeka sikwenze ukulawula amapharamitha e-characteristic impedance:

I-dielectric constant Er yesendlalelo sokufaka ugesi, ububanzi bezintambo i-W1 ne-W2 (i-trapezoidal), ubukhulu bezintambo i-T, kanye nobukhulu bezintambo zokufaka ugesi i-H.

Ububanzi bomugqa obuklanywe ngu-W

Ukulahlekelwa yi-A - ukugqwala (bheka ithebula elingenhla)

Isizathu sobubanzi obungaguquguquki phakathi kwengxenye ephezulu nephansi yomugqa ukuthi ngesikhathi senqubo yokukhiqiza ama-PCB, ukugqwala kwenzeka kusukela phezulu kuya phansi, okuholela esimweni se-trapezoidal somugqa ogqwalile.

Kukhona ubudlelwano obuhambisanayo phakathi kobukhulu bomugqa u-T kanye nobukhulu bethusi balolu ngqimba, kanje:

* Ngenxa yethonya elincane lobukhulu bemaski ye-solder ku-impedance, kucatshangwa ukuthi iyinani elingaguquki elingu-0.5mil.

Singafinyelela ukulawulwa kwe-impedance ngokulawula la mapharamitha. Uma sithatha i-PCB engezansi ka-Anwei njengesibonelo, sizochaza izinyathelo zokulawulwa kwe-impedance kanye nokusetshenziswa kwe-SI9000:

Isendlalelo sesibili yindiza yomhlabathi, isendlalelo sesihlanu yindiza yamandla, kanti izingqimba ezisele ziyizingqimba zesignali.

Incazelo: I-dielectric ephakathi kwezingqimba eziphakathi yi-FR-4, ene-dielectric constant engu-4.2; Izingqimba eziphezulu nezingezansi ziyizingqimba ezingenalutho ezihlangana ngqo nomoya, kanti i-dielectric constant yomoya ingu-1.

Abaklami be-PCB bangasebenzisa ngokugcwele isakhiwo esisezingeni sama-PCB ukuze bafinyelele ukulawulwa kwe-impedance. Ngokubeka izendlalelo zesignali ezahlukene ezindaweni ezahlukene zezendlalelo, amandla okusebenza kanye ne-inductance phakathi kwezendlalelo kungalawulwa ngempumelelo. Ngokuvamile, ungqimba lwangaphakathi lusebenzisa izinto ze-impedance ephezulu kanti ungqimba lwangaphandle lusebenzisa izinto ze-impedance ephansi ukunciphisa umthelela wokuzindla kanye nokuxoxa nge-crosstalk.

Imigqa yokudlulisa isignali ehlukile inganikeza ikhono elingcono lokulwa nokuphazamiseka kanye nengozi ephansi yokukhuluma. Imigqa yokudlulisa isignali ehlukile iyizintambo ezimbili ezihambisanayo ezinama-voltage aphambene kodwa ezinobukhulu obulinganayo, ezinganikeza ubuqotho besignali obungcono kanye nekhono lokulwa nokuphazamiseka. Ukuvinjelwa kwemigqa yokudlulisa isignali ehlukile kuvame ukulawulwa ukukhethwa kwesikhala somugqa, ububanzi kanye nendiza yomhlabathi.

Amapharamitha ejiyomethri njengobubanzi bomugqa we-PCB, isikhala kanye nokwakheka kwawo angasetshenziswa futhi ukulawula impedance. Emigqeni evamile ye-microstrip, ububanzi bomugqa obukhulu kanye nesikhala esikhulu kunganciphisa impedance. Emigqeni ye-coaxial, ububanzi bomugqa wangaphakathi obuncane kanye ne-radii yomugqa wangaphandle emikhulu kungandisa impedance. Ukukhethwa kwe-geometry yezintambo kudinga ukwenziwa ngcono ngokusekelwe ezidingweni ezithile ze-impedance kanye nemvamisa yesignali.

I-dielectric constant yezinto ze-PCB nayo ithinta i-impedance. Ukukhetha izinto ezinezakhiwo ze-dielectric ezizinzile kuyingxenye yokulawula i-impedance. Ezisetshenzisweni zemvamisa ephezulu kanye nesivinini esikhulu, izinto ezisetshenziswa kakhulu zifaka phakathi i-FR-4 (ibhodi eliqinisiwe le-fiber yengilazi), i-PTFE (i-polytetrafluoroethylene), kanye ne-RF (imvamisa yomsakazo).

Ngaphambi kokuklama i-PCB, ukusebenzisa amathuluzi okulingisa nawokuklama kungasiza abaklami ukuqinisekisa ngokushesha nangokunembile nokuthuthukisa i-impedance. Lawa mathuluzi angalingisa ukuziphatha kwesekethe, ukulahlekelwa kokudluliselwa kwesignali kanye nokusebenzisana kwe-electromagnetic ukunquma amapharamitha okuklama i-PCB afanele. Amanye amathuluzi okulingisa avamile afaka i-CST Studio Suite, i-HyperLynx kanye ne-ADS.

Ukulawulwa kwe-PCB impedance kudlala indima ebalulekile kumasekethe edijithali nawe-analog asheshayo. Ngokuklanywa okunengqondo kokulandelana, ukusetshenziswa kwemigqa yokudlulisa isignali ehlukile, ukulawulwa kwe-geometry yezintambo, ukukhethwa kwezinto ezifanele ze-PCB, kanye nokusetshenziswa kwamathuluzi okulingisa nawokuklama, ukulawulwa kwe-impedance okunembile kungafinyelelwa, ngaleyo ndlela kuthuthukiswe ukusebenza kwesekethe kanye nobuqotho besignali.