Ukulawulwa Kokuvinjelwa Kwe-PCB Kwezingqimba Eziyi-10 kanye Nokuqinisekiswa Kwe-TDR

I-impedance elawulwayo itholakala ngokulawula isakhiwo somugqa wokudlulisela, hhayi ngokunikeza ububanzi obujwayelekile bokulandelela kuphrothokholi. Ithagethi efanayo engu-50 Ω ingadinga i-geometry ehlukene kakhulu kumabhodi amabili anezingqimba eziyishumi ngoba ukujiya kwe-dielectric, ukujiya kwethusi, ukwakhiwa kwezinto, imaski yokubopha kanye nethusi eliseduze kuhlukile. Ngakho-ke, umdwebo wokukhiqiza kufanele ucacise ithagethi kanye nesakhiwo sokubhekisela, kuyilapho ukubalwa kwe-stackup kanye ne-fabricator okukhishwe kuchaza ububanzi bokugcina kanye nesikhala.

Lo mhlahlandlela uchaza ukuthi yini okumele ibalwe, ukuthi ukubekezelelana kokwenziwa kusebenza kanjani ngempela, nokuthi ikhuphoni le-TDR kufanele limele kanjani isakhiwo esiqondisiwe. Ligwema ngamabomu ukushicilela imithetho yonke ethi “5 mil equals 50 Ω”, ngoba lezo zinombolo ziba yiphutha ngokushesha nje lapho ukwakhiwa kushintsha.

Impedance Elawulwayo Incazelo Ye-Stackup kanye Nenqubo

I-impedance ephawulekayo ye-trace ye-PCB isethwa ukusatshalaliswa kwamasimu kagesi namagnetic azungeze umqhubi. Okufakwayo okuyinhloko yi-cross-section yomqhubi oqediwe, ibanga eliya kwelinye noma ngaphezulu izindiza zokubhekisela, izakhiwo ze-dielectric, isikhala esiphakathi semigqa ehlanganisiwe, imaski ye-solder ezakhiweni zobuso kanye nokuba khona kwethusi eliseduze. Ubulukhuni bethusi kanye nokulahleka kwe-dielectric kuthinta ukusabalala kanye nempendulo elinganisiwe, ikakhulukazi njengoba izinga lomphetho likhuphuka.

I-oda lokulawula ukuvimba kufanele liphendule imibuzo emibili ehlukene. Okokuqala, yikuphi ukwakheka kwesimo okulindeleke ukuthi kuhlangabezane nomgomo ku-stackup ekhethiwe? Okwesibili, ukukhiqizwa kuzoqinisekiswa kanjani? Ukubalwa kwe-field-solver kubhekwana neyokuqala; ikhuphoni elimele kanye nenqubo ye-TDR kubhekwana neyesibili. Akukho okunye okuthatha indawo yokulingisa isiteshi lapho ukulahlekelwa kokufakwa, ngokunqamuka kanye nezixhumi kubalulekile.

I -stackup yezingqimba eziyi-10 kumele iqandiswe ngaphambi kokuba i-geometry eqondisiwe iqandiswe. Uma umenzi eshintsha i-core, i-prepreg, i-copper foil noma ubukhulu obucindezelwe, ukubalwa kwe-impedance kumele kubuyekezwe futhi noma yiluphi ushintsho lobuciko oluvelayo kumele lulandele inqubo yokuvunyelwa okuvunyelwene ngayo.

Okufakiwe Kuyadingeka Ngaphambi Kokuthi I-Trace Geometry Ikhishwe

Kuma-differential pairs, umenzi kufanele athole ububanzi nesikhala njengezinto eziguquguqukayo kunomthetho wobuciko obungaguquki lapho i-stackup isaqedwa. Umdwebo okhishwe ungagunyaza ukulungiswa kobubanzi obulawulwayo ngaphakathi kwemikhawulo ebekiwe, noma ungadinga imvume yamakhasimende ngaphambi kokushintsha kobuciko.

I-Single-End, i-Odd-Mode kanye ne-Differential Impedance

Ithagethi enesiphelo esisodwa njenge-50 Ω ichaza umqhubi oyedwa uma kuqhathaniswa nesakhiwo sayo sokubuyisa. Ithagethi ehlukile njenge-85 Ω noma i-100 Ω ichaza umehluko we-voltage phakathi kwabaqhubi ababili abaqhutshwa ngezindlela eziphambene. Kumbhangqwana ohlangene ohambisanayo, i-differential impedance cishe iphindwe kabili kune-odd-mode impedance. Akuyona ngempela i-single-end impedance ephindwe kabili kunoma iyiphi i-trace uma enye i-trace ingekho.

Ukuxhuma okunamandla kuvumela isikhala esincane sebhangqa futhi kunganciphisa ukuvinjelwa komehluko, kodwa futhi kwenza umphumela ube bucayi kakhulu ekushintsheni kwesikhala kanye nokuhlukaniswa kwebhangqa lendawo. Amabhangqa ahlanganiswe kancane athonywa kakhulu yizindawo zawo zokubhekisela futhi ancishiswe yigebe eliqondile, kodwa angasebenzisa ububanzi obukhulu bendlela yokuqondisa. Ibhalansi efanele incike ekuxineni kwendlela, ukugoba, ukukhuluma ngeziteshi eziseduze kanye nekhono lomenzi wokwakha.

Ukuphazamiseka kwemodi evamile kanye nokuguqulwa kwemodi kungabaluleka ngisho noma inombolo ye-TDR ehlukile idlula. Ukuqhuma okungalingani, ukungalingani ngama-antipads, ukuguquka okuhlukile kokubhekisela kanye nokulungiswa kohlangothi olulodwa kungaguqula amandla okungafani abe yimodi evamile. Ngamazinga aphezulu edatha, imodeli yokuguquka kwe-3D inolwazi oluningi kunenombolo yekhuphoni eyodwa.

Izakhiwo zeMicrostrip, Stripline kanye neCoplanar

I-microstrip engaphandle

I-Microstrip kulula ukuyihlola nokuyiqondisa kodwa amasimu ayo anwebeka kokubili kumaskhi we-laminate kanye nomoya noma i-solder. Ngakho-ke, i-dielectric constant esebenzayo iphansi kune-bulk laminate Dk. Imaskhi ye-solder, ukuqeda kobuso, ukuthululwa kwethusi lendawo kanye nama-component pads konke kungaphazamisa umphumela. I-plating yangaphandle iphinde ishintshe ubukhulu be-conductor ngemva kokukhethwa kwe-base foil.

I-microstrip efakiwe kanye ne-stripline

I-microstrip efakiwe imbozwe yi-dielectric ezinhlangothini zombili kodwa ibhekiselwa kakhulu endizeni eyodwa. I-Stripline iphakathi kwezindiza ezimbili. I-Stripline ehambisanayo inesikhala se-dielectric esilinganayo noma esicishe silingane; i-stripline engafaniyo inereferensi eseduze kakhulu kodwa isasebenzisana nezindiza zombili. I-field solver kufanele ibonise imingcele kanye nendawo yangempela yokulandelela ngemva kwe-lamination.

Izakhiwo ze-Coplanar waveguide

Inhlabathi ye-Coplanar ingalawula ukusabalala kwensimu futhi ihlinzeke ngesivikelo, kodwa igebe eliya ethusini eliseceleni liba esinye isici esibalulekile. Iziqhingi zomhlaba kumele zixhunywe endizeni yokubhekisela ngephethini efanele noma zingasebenza njengeziqhubi eziphendulayo. Izakhiwo ze-Coplanar kufanele zenziwe imodeli nge-mask yangempela kanye ne-geometry yomhlabathi kunokuba zifakwe njengomthetho ojwayelekile "wokuthulula umhlabathi".

Ukwehlukahluka Kokukhiqiza kanye Nesabelomali Sokubekezelelana Esingokoqobo

I-impedance yokukhiqiza iyahamba ngoba ubukhulu obuningana buhamba ndawonye. Ukuqopha kushintsha ububanzi obuphezulu nobaphansi. I-lamination ishintsha ubukhulu be-dielectric obucindezelwe. Okuqukethwe kwe-resin kanye nokusatshalaliswa kwengilazi kuthinta i-Dk esebenzayo. I-plating yangaphandle kanye ne-solder mask yengeza ukwehluka okwengeziwe. Ukuhlaziywa kokubekezelelana okunesibopho kusebenzisa ikhono lenqubo lomhlinzeki lokwakha ngqo kunokucabanga ukuthi konke okufakwayo kungabanjwa ngenani lakho elijwayelekile.

I-+/-10% iyisivumelwano esivamile sokuthengwa, kodwa akuyona into ezenzakalelayo ebekwe yidokhumenti ye-IPC. Amabhande aqinile angase asebenze ezakhiweni ezikhethiwe kanye nosayizi wephaneli, kuyilapho ezinye izakhiwo ezine-impedance ephezulu, ezincane kakhulu noma ezifakwe kakhulu zingase zingabi namandla anele. Ngaphambi kokucacisa i-+/-5% noma eziqinile, qinisekisa i-geometry margin etholakalayo, indlela yekhuphoni, isampula yelothi nokuthi ukubekezelelana kulinganiswa kukhuphoni noma kuqinisekisiwe kuyo yonke indawo ehanjiswayo.

Ukuqinisa i-impedance ngaphandle kwesizathu sezinga lesiteshi kungandisa ukulahlwa noma kuphoqe i-trace/space geometry ebanzi elimaza ubuningi be-routing. Ngakolunye uhlangothi, ikhuphoni elijwayelekile le-+/-10% lingase linganeli lapho isixhumi, iphakheji kanye nokungaqhubeki kushiya umkhawulo omncane wesistimu. Ukubekezelelana kufanele kuvele kwisabelomali sikagesi kanye nocwaningo lwamandla okukhiqiza.

Umklamo Wekhuphoni Nokuqinisekiswa Kwe-TDR

I-IPC-2141 iyisiqondiso sokuklama samasekethe alawulwayo okuvinjelwa; akuyona indlela yokuhlola ye-TDR. Ukulinganiswa kwe-impedance yesici nge-reflectometry yesizinda sesikhathi kuhlanganiswa yi-IPC-TM-650 Indlela 2.5.5.7A. I-oda lokuthenga kufanele lisho indlela efanele noma inqubo yamakhasimende evunyelwene ngayo bese lichaza ikhuphoni kanye nemininingwane yokwamukela enganqunywa yindlela yodwa.

Ikhuphoni elimele

Ikhuphoni kufanele isebenzise ungqimba olufanayo, isakhiwo sokubhekisela, ukucubungula ithusi, ukwakhiwa kwe-dielectric kanye nesimo se-solder-mask njengendlela elawulwayo. Amakhuphoni ahlukene kufanele akhiqize ububanzi kanye nesikhala esiphindwe kabili. Uma kunezakhiwo eziningi, umkhondo owodwa wekhuphoni awukwazi ukuwamela wonke. Indawo yekhuphoni kuphaneli yokukhiqiza ibalulekile ngoba i-plating kanye ne-etch kungahluka kulo lonke iphaneli.

Iwindi lokulinganisa kanye nokuqaliswa

Ukuqaliswa, ama-probe pads kanye nokungaqhubeki kokuqala kumele kuhlukaniswe nesigaba esifanayo esisetshenziselwa ukufundwa kwe-impedance. Isikhathi sokukhuphuka kwe-TDR kufanele sifanele isici esilinganiswayo; umphetho oshesha kakhulu ungagcizelela ukungaqhubeki okuncane, kuyilapho umphetho ohamba kancane ungawenza ube ngokwesilinganiso. Ukulahlekelwa nokuhlakazeka kungadala umkhondo othambekile, ngakho-ke iwindi lokwamukela kanye nendlela yokubika kufanele kuvunyelwane.

Ukuthatha amasampula namarekhodi

“Ngephaneli ngayinye,” “ngenqwaba ngayinye” kanye “nesihloko sokuqala kuphela” kuyizinketho zohlelo lwezentengiselwano kanye nolwekhwalithi, hhayi imiphumela ezenzakalelayo yenani lokubekezelelana. Cacisa inani nendawo yamakhuphoni, isimo esibhubhisayo noma esigciniwe, incazelo yenqwaba, umthetho wokuhlola kabusha nokuthi ngabe iziza noma imiphumela yesifinyezo iyadingeka yini. Ngezinhlelo ezinokwethenjelwa kakhulu, gcina ukulandeleka phakathi kwekhuphoni, iphaneli namabhodi athunyelwe.

Indlela Yokucacisa Impedance Emdwebweni Wokwenza

Ithebula le-impedance kufanele licace ngokwanele ukuthi amaqembu obunjiniyela, ama-CAM kanye nokuhlola alihumushe ngendlela efanayo.

Gcina imithetho yokuqondisa yephrothokholi kusakhiwo noma incazelo yomklamo futhi ugcine ukwamukelwa kwe-impedance kumdwebo wokwenziwa. Lokhu kuhlukaniswa kuvimbela umhlinzeki ekuchazeni i-"PCIe" njengemfuneko ephelele kagesi.

Ukuze ubukeze umsebenzi wobuciko, sebenzisa umhlahlandlela wokuqondisa wezendlalelo eziyi-10 ; ukuze uthole iziguquguquko zokukhiqiza kanye nemibhalo, bheka umhlahlandlela wenqubo yokukhiqiza.

Ukuthola Umphumela Wokungaphephi Ongaphumeleli Ithagethi

Ikhuphoni ehlulekile kufanele ibangele uphenyo oluhlelekile kunokushintsha ububanzi bomugqa ngokushesha. Qinisekisa ukuthi ikhuphoni lihambisana nesakhiwo sebhodi, kusetshenziswe ukubuyekezwa kwe-stackup efanele, iwindi lokuqalisa nelokulinganisa le-TDR liyasebenza, futhi umphumela obikiwe awulawulwa ukulahleka okukhulu noma ukungaqhubeki kwe-probe. Bese uqhathanisa ubukhulu be-trace cross-section kanye ne-dielectric model nemodeli ye-solver.

Impedance elinganiswe kancane ingabangelwa umkhondo obanzi, i-dielectric encane, i-Dk esebenza kahle kakhulu, ithusi elijiyile, umhlabathi oseduze we-coplanar noma imaski eyengeziwe ye-solder. Impedance ephezulu ingabangelwa yizimo eziphambene. Imiphumela ehlukene ingahamba ngenxa yesikhala sezinhlangothi ezimbili noma ngabe ububanzi be-trace bulungile. Idatha ye-microsection kanye nemodeli ebalwe kabusha iwusizo kakhulu kunokushintsha okokufaka okukodwa ngokuqagela.

Uma iphutha lihlelekile, buyekeza imodeli elinganiswe ngenqubo kanye nesinxephezelo sobuciko. Uma litholakala ngokwesikhundla sephaneli, hlola ukufana kwe-etch, i-plating noma i-lamination. Noma yikuphi ukulungiswa kabusha noma ukusetshenziswa njengoba kunjalo kufanele kucabangele umkhawulo wesistimu, hhayi iphesenti lekhuphoni kuphela.

Thumela Ithebula Le-Stackup kanye ne-Impedance ukuze Libuyekezwe

Imvamisa, Ukulahlekelwa kanye Nencazelo Yenombolo ye-TDR

I-impedance yesici ivame ukwethulwa njengenombolo eyodwa, kodwa ukuxhumana kwangempela kuyahlakazeka futhi kuyalahleka. Izakhiwo ze-dielectric, ubulukhuni bethusi kanye nomphumela wesikhumba kuyashintsha ngokuvama, ngakho-ke umkhondo we-TDR obonakalayo ungathambeka kukhuphoni ende. Ingxenye emfushane efanayo ingafunda ngendlela ehlukile uma ilinganiswa ngesilinganiso somphetho ohlukile noma indlela yokususa ukushumeka. Ngakho-ke inqubo yokwamukela kufanele ichaze ukuthi inani lifundwa kuphi futhi kanjani kunokuthembela esithombeni-skrini sodwa.

Ikhuphoni le-impedance elidlulayo alibonisi ukulahlekelwa okuphansi kokufakwa. Izimpawu ezimbili zingalinganisa ama-50 Ω kuyilapho enye isebenzisa ithusi elibi kanye ne-dielectric elahlekelwa kakhulu. Ngokuphambene nalokho, izinkomba ezilahlekile zingenza ukuphela kwesimo se-waveform ye-TDR kubonakale kuhlukile ngisho noma i-geometry yayo ebonakalayo ifana. Uma ukulahlekelwa kwesiteshi kubalulekile, sebenzisa ikhuphoni yokulahlekelwa kwesignali noma isilinganiso se-S-parameter esifanele ngaphezu kwe-TDR.

Izingibe zekhuphoni ezihlukile

I-TDR ehlukile idinga ukuqaliswa okulinganiselayo kanye nobude obulinganayo bukagesi esigabeni sokulinganisa. I-asymmetry ye-probe-pad, i-fanout engalingani noma ukuvulwa kwendiza yereferensi kungadala ukuguqulwa kwemodi okubukeka njengenkinga ye-pair-impedance. Ikhuphoni kufanele ifake ubude obufanayo obanele ukuhlukanisa ukuqaliswa nefasitela lokuhlola futhi kufanele ikhiqize kabusha imaski yangempela kanye nesakhiwo sereferensi. Ukubika kokubili umehluko kanye, lapho kuwusizo khona, ukuziphatha kwemodi evamile kungaveza i-asymmetry efihliwe yinani elilodwa elimaphakathi.

Ukuhambisana kokukhiqiza

Uma kungeniswa i-stackup entsha, hlanganisa imiphumela ye-TDR nobubanzi be-trace obuhlukaniswe nge-microsectioned, ukujiya kwethusi kanye nesikhala se-dielectric. Lokho kuhlangana kudala imodeli yenqubo ethembeke kakhulu yezindawo zakamuva. Uma umhlinzeki eshintsha ukwakhiwa kwezinto, i-foil noma umjikelezo wokucindezela, ukuhlangana kufanele kubuyekezwe kunokuba kucatshangwe ukuthi isinxephezelo sangaphambilini sisasebenza.

Ukubekezela Okuqinile kanye Negunya Lomsebenzi Wobuciko

Inombolo eqinile akuyona njalo incazelo engcono. Ukusatshalaliswa okufinyelelekayo kuncike ebubanzini bokulandelela, ukuphakama kwe-dielectric, ukujiya kwethusi, indawo yephaneli, inqubo ye-etch nokuthi isakhiwo sifakwe yini ebusweni. Imikhondo emincane kakhulu ingabonisa ushintsho olukhulu lwephesenti kusuka ekushintsheni okuncane kwe-etch okuphelele; imigqa ye-impedance ephezulu kakhulu ingadinga ububanzi noma izikhala ze-dielectric ezingasebenzi. Umenzi kufanele abukeze ukubekezelelana njengombuzo wekhono lenqubo, hhayi nje ukukwamukela njengenketho yokuthengisa.

Ngaphambi kokukhishwa, vumelanani ngokuthi ubani olawula umsebenzi wobuciko. Enye indlela iwukuba ikhasimende linikeze i-geometry ejwayelekile futhi ligunyaze umenzi ukuthi abuyisele ububanzi kanye negebe elihlanganisiwe ku-stackup ekhishwe. Enye iwukumisa i-geometry bese lidinga ukuthi umhlinzeki afane nokwakhiwa ncamashi. Ukuxuba lezi zindlela ezimbili kudala izingxabano lapho umhlinzeki elungisa ububanzi bomugqa kodwa i-layout clearance, skew noma i-crosstalk model ithathe i-geometry yokuqala.

Ngokwakhiwa okusha, cabanga ngekhono lesihloko sokuqala eliqhutshwa ngamakhuphoni kuzo zonke izindawo zamaphaneli ezimele. Sebenzisa ukusatshalaliswa okulinganisiwe ukuze usethe uhlelo lokulawula ukukhiqiza olungokoqobo. Ikhuphoni elilodwa elidlulayo alikwazi ukusungula ikhono lesikhathi eside, kuyilapho inqubo evunyelwe ngokwezibalo ingasekela ibhendi eqinile ngaphandle kokuhlolwa ngokweqile.

Uhlu Lokuhlola Lokukhishwa Kwe-Impedance

Isidingo se-impedance siphelele kuphela uma inhloso, isakhiwo somugqa wokudlulisela, igunya lokukhiqiza kanye nohlelo lokuqinisekisa konke kuchaziwe. Umdwebo obala "50 Ω" noma "100 Ω umehluko" ngaphandle kwesendlalelo, ireferensi, ukubekezelelana kanye nesimo semaski ushiya umhlinzeki ukuba enze izibikezelo.

• Khomba isigaba ngasinye se-impedance ngesendlalelo sesiginali, indiza yokubhekisela noma izindiza, ithagethi, ukubekezelelana kanye nohlobo lwesakhiwo.
• Nikeza i-geometry ejwayelekile njengenhloso yokuklama bese usho ukuthi umhlinzeki angalungisa ububanzi noma isikhala esiphindwe kabili.
• Imodeli ecindezelwe nge-dielectric, ithusi eliqediwe le-trapezoidal, imaski yokwelula kanye nethusi eliseduze.
• Sebenzisa idatha yezinto zokwakha ezithile noma imodeli yomklamo womenzi wezinto ezibhaliwe-Dk.
• Dala amakhuphoni amele isakhiwo sangempela sokukhiqiza futhi achaze indlela ye-TDR, imvamisa yesampula kanye nokuqukethwe kombiko.
• Gcina ukuqinisekiswa kwe-impedance yekhuphoni kuhlukile ekulahlekelweni kokufakwa kwesiteshi, ukuhambisana nokuhambisana nesixhumi kanye nokulahlekelwa yisiteshi.

Ukubekezelelana okuqinile kufanele kuqinisekiswe ukuzwela kwesiteshi kanye nekhono lenqubo elibonisiwe. Akuyona indawo yendlela yokubuya eqhubekayo, indlela enhle yokuguquka noma imodeli yokulahlekelwa okuphelele.

Ukungaqiniseki Kokulinganisa kanye Nokuxhumana Kwekhuphoni Nomkhiqizo

Umphumela we-TDR uthintwa yikhuphoni, ukuqaliswa, ukufakwa, umkhawulokudonsa wethuluzi, ikhwalithi yendiza yokubhekisela, ukulinganiswa kanye nendlela esetshenziswayo ukukhetha isifunda se-impedance esibikiwe. Amalabhorethri amabili angalinganisa ikhuphoni elifanayo ngendlela ehlukile uma lezi zimo zingahambisani. Ngakho-ke inqubo yokwamukela kufanele ichaze okungaphezu kwenhloso kanye nokubekezelelana.

• Khomba indlela yokuhlola noma inqubo yamakhasimende kanye nokulindela kwethuluzi/ukulinganisa.
• Chaza ubude bekhuphoni, indlela yokususa ukuqalisa noma indlela yokuvala kanye nesifunda esisetshenziswe enanini elibikiwe.
• Gcina ikhuphoni kusakhiwo sephaneli esifanayo, ungqimba, ithusi kanye nohlelo lokubhekisela njengesakhiwo somkhiqizo.
• Qopha ukuthi inani elibikiwe liyisilinganiso, isilinganiso, umphumela ovaliwe noma esinye isibalo esivunyelwene ngaso.
• Chaza ukuthi izinto ezingaphandle, ukuqaliswa kwekhuphoni elonakele kanye nokuhlolwa kabusha kuphathwa kanjani.

Ukuxhumana kwekhuphoni nakho kunemingcele. Ikhuphoni elide eliqondile alifaki yonke iphedi, intamo-phansi, i-via, ukuqaliswa kwesixhumi noma ukuvulwa kwendiza kumkhiqizo. Lokho kuphazamiseka kungokwemodeli yesiteshi noma isakhiwo sokuhlola esizinikele. Ngokuphambene nalokho, ukwengeza izici zomkhiqizo eziyinkimbinkimbi kukhuphoni ye-impedance kungenza kube nzima ukuhlukanisa i-impedance yenqubo nokungaqhubeki ngamabomu.

Ngezinhlelo zokubekezelelana okuqinile, ukuhlangana kufanele kuqhathaniswe i-geometry yekhuphoni elilinganisiwe kanye nedatha ye-microsection nemodeli ye-field-solver. Uma i-impedance iphezulu noma iphansi, ukubuyekezwa kufanele kucabangele i-dielectric ecindezelwe, ububanzi be-conductor obuphezulu/bozansi, ukujiya kwethusi kanye nokwakhiwa kwezinto ngaphambi kokushintsha umsebenzi wobuciko. Ukulungisa ububanzi be-trace ngaphandle kokuthola imbangela yangempela kungenza inqwaba eyodwa idlule ngenkathi kunciphisa ukuphindaphindeka.