Ngaphandle kokulawulwa kwe-impedance, ukubonakaliswa kwesiginali okukhulu nokuphazamiseka kuzobangelwa, okuholele ekwehlulekeni komklamo. Izimpawu ezijwayelekile, njengebhasi le-PCI, ibhasi le-PCI-E, i-USB, i-Ethernet, inkumbulo ye-DDR, isiginali ye-LVDS, njll., Konke kudinga ukulawulwa kwe-impedance. Ukulawulwa kokuphazamiseka ekugcineni kudinga ukwenziwa ngedizayini ye-PCB, nayo ebeka phambili izidingo eziphakeme PCB ibhodi ubuchwepheshe. Ngemva kokuxhumana nefekthri ye-PCB futhi kuhlanganiswe nokusetshenziswa kwesofthiwe ye-EDA, ukuvinjelwa kwezintambo kulawulwa ngokuvumelana nezidingo zobuqotho besignali.

Izindlela ezahlukahlukene zokufaka izintambo zingabalwa ukuthola inani le-impedance elihambelanayo.

Imigqa ye-Microstrip

Iqukethe umucu wocingo onendiza yaphansi kanye ne-dielectric phakathi. Uma i-dielectric engaguquki, ububanzi bomugqa, nebanga layo ukusuka endizeni yasemhlabeni kuyalawuleka, impedance yayo yesici iyalawuleka, futhi ukunemba kuzoba ngaphakathi kwe- ± 5%.

Ungayilawula kanjani i-PCB wiring impedance

I-Stripline

Umugqa weribhoni umucu wethusi phakathi kwe-dielectric phakathi kwezindiza ezimbili eziqhuba. Uma ukushuba nobubanzi bolayini, i-dielectric eqhubekayo yesilinganiso, nebanga eliphakathi kwezindiza zomhlaba zalezi zingqimba ezimbili ziyalawuleka, i-impedance yesici yomugqa iyalawuleka, futhi ukunemba kungaphakathi kwe-10%.

Ungayilawula kanjani i-PCB wiring impedance

Ukwakheka kwebhodi enezingqimba eziningi:

Ukuze ulawule kahle i-PCB impedance, kubalulekile ukuqonda ukwakheka kwe-PCB:

Imvamisa lokho esikubiza ngokuthi ibhodi ye-multilayer yakhiwa yipuleti eliyisisekelo neshidi eliqinile elihlanganiswe ndawonye. Ibhodi eliyinhloko liwubulukhuni obunzima, obucacile, ipuleti lethusi lesinkwa, okuyisisekelo sebhodi eliphrintiwe. Futhi isiqeshana eselaphekiwe sakha lokho okubizwa ngokuthi ukungena kokungena, kudlala indima yokubopha ipuleti eliyisisekelo, yize kukhona ukushuba kokuqala, kepha ngenkathi kucindezelwa ukushuba kwalo kuzokwenzeka izinguquko ezithile.

Imvamisa izingqimba zombili zedielectric ezingaphandle kakhulu zemigqa eminingana ziyizingqimba ezimanzi, bese kusetshenziswa izingqimba zefreyili ezihlukile ngaphandle kwalezi zingqimba ezimbili njengefreyimu yangaphandle yethusi. Ubuningi bokuqala bokucaciswa kwe-foil yangaphandle yethusi kanye ne-foil yangaphakathi yethusi imvamisa i-0.5oz, i-1OZ, i-2OZ (i-1OZ icishe ibe yi-35um noma i-1.4mil), kepha ngemuva kochungechunge lokwelashwa kwendawo, ubukhulu bokugcina bocingo lwethusi lwangaphandle luzokwanda cishe 1OZ. Ucwecwe lwangaphakathi lwethusi luyimbozo yethusi ezinhlangothini zombili zepuleti eliyisisekelo. Ubukhulu bokugcina buhlukile kancane kubukhulu bokuqala, kepha ngokujwayelekile bancishiswa ngo-um abaningana ngenxa yokudonswa.

Isendlalelo sangaphandle sebhodi le-multilayer ungqimba lokumelana nokushisela, okuyilokho esivame ukuthi “uwoyela oluhlaza”, kunjalo, lungaba luphuzi noma eminye imibala. Ubukhulu besendlalelo sokumelana ne-solder ngokuvamile akulula ukucacisa ngokunembile. Indawo engenalo ucwecwe lwethusi ebusweni incane ukujiya kunendawo enefoyili yethusi, kepha ngenxa yokushoda kobukhulu bethusi, ngakho-ke ucwecwe lwethusi lusabonakala kakhulu, lapho sithinta indawo yebhodi ephrintiwe ngeminwe yethu.

Lapho ukwenziwa kwebhodi ephrintiwe kwenziwa, ngakolunye uhlangothi, ukukhetha okunengqondo kwamapharamitha wezinto ezibonakalayo, ngakolunye uhlangothi, ukushuba kokugcina kweshidi elelapheke kancane kuzoba kuncane kunokuqina kokuqala. Okulandelayo isakhiwo esijwayelekile esinezingqimba eziyi-6:

Ungayilawula kanjani i-PCB wiring impedance

Nemingcele PCB:

Izitshalo ezihlukile ze-PCB zinomehluko omncane kumapharamitha we-PCB. Ngokuxhumana nokusekelwa kwezobuchwepheshe bebhodi lesifunda, sithole imininingwane ethile yepharamitha yesitshalo:

Surface ucwecwe zethusi:

Kunobukhulu obuthathu befoyili yethusi engasetshenziswa: i-12um, i-18um ne-35um. Ubukhulu bokugcina ngemuva kokuqeda cishe buba ngu-44um, 50um no-67um.

Ipuleti elingumongo: I-S1141A, i-FR-4 ejwayelekile, amapuleti amabili wethusi ayisinkwa asetshenziswa kakhulu. Ukucaciswa kokuzikhethela kunganqunywa ngokuxhumana nomkhiqizi.

Ithebhulethi ephulukiswe kancane:

Imininingwane (ubukhulu bangempela) ingu-7628 (0.185mm), 2116 (0.105mm), 1080 (0.075mm), 3313 (0.095mm). Ubukhulu bangempela ngemuva kokucindezela imvamisa cishe bube ngu-10-15um ngaphansi kwenani langempela. Kungasetshenziswa amaphilisi ama-3 aphulukisiwe angaphansi kwesendlalelo esifanayo sokungena, futhi ukushuba kwamaphilisi amathathu aphulukisiwe akunakufana, okungenani kungasetshenziswa amaphilisi ayisithupha aphulukisiwe, kepha abanye abakhiqizi kufanele basebenzise okungenani amabili . Uma ukushuba kwesiqeshana eselaphekiwe kunganele, ucwecwe lwethusi ezinhlangothini zombili zepuleti lomgogodla lungasuswa, bese kuthi isiqeshana eselapheke kancane singahlanganiswa ezinhlangothini zombili, ukuze ungqimba lokungena olunamandla lube kufinyelelwe.

Ukumelana Welding ungqimba:

Ubukhulu besendlalelo se-solder resist on the foil yethusi ngu-C2≈-8-10um. Ubukhulu besendlalelo sokumelana ne-solder ebusweni ngaphandle kocwecwe lwethusi yi-C1, ehluka ngobukhulu bethusi ebusweni. Lapho ukushuba kwethusi ebusweni kungu-45um, C1≈13-15um, futhi lapho ukushuba kwethusi ebusweni kungu-70um, C1-17-18um.

Isigaba sokunqamula:

Singacabanga ukuthi ingxenye yesiphambano yocingo ingunxande, kepha empeleni iyi-trapezoid. Ukuthatha ungqimba we-TOP njengesibonelo, lapho ukushuba kocwecwe lwethusi kuyi-1OZ, umphetho ongaphezulu ongezansi we-trapezoid ngu-1MIL mfushane kunomphetho ongezansi ongezansi. Isibonelo, uma ububanzi bomugqa bungu-5MIL, khona-ke izinhlangothi eziphezulu nezingezansi zimayelana ne-4MIL kanti izinhlangothi ezingezansi nezingezansi zingaba ngu-5MIL. Umehluko phakathi kwemiphetho ephezulu neyaphansi uhlobene nokujiya kwethusi. Ithebula elilandelayo likhombisa ubudlelwane obuphakathi phezulu nangaphansi kwe-trapezoid ngaphansi kwezimo ezihlukile.

Ungayilawula kanjani i-PCB wiring impedance

Ukuvunyelwa: Ukuvunyelwa kwamashidi aphulukiswe kancane kuhlobene nokushuba. Ithebula elilandelayo likhombisa ukushuba nokuvunyelwa kwemingcele yezinhlobo ezahlukahlukene zamashidi aphulukisiwe:

Ungayilawula kanjani i-PCB wiring impedance

Ukuhlala kwe-dielectric kwepuleti kuhlobene nezinto ze-resin ezisetshenzisiwe. Ukuguquguquka kwedielectri kwepuleti le-FR4 kungu-4.2 – 4.7, futhi kuncipha ngokwanda kwemvamisa.

Isici sokulahleka kwe-dielectric: izinto zedielectric ngaphansi kwesenzo sokushintsha inkambu kagesi, ngenxa yokushisa namandla okusetshenziswa kubizwa ngokuthi ukulahleka kwe-dielectric, okuvame ukuvezwa nge-dielectric loss factor Tan δ. Inani elijwayelekile le-S1141A lingu-0.015.

Ubuncane bomugqa wobubanzi nokuhlukaniswa kwemigqa ukuqinisekisa ukusetshenziswa: 4mil / 4mil.

Isingeniso sethuluzi lokubala le-impedance:

Lapho siqonda ukwakheka kwebhodi le-multilayer futhi sazi imingcele edingekayo, singabala impedance nge-software ye-EDA. Ungasebenzisa i-Allegro ukwenza lokhu, kepha ngincoma iPolar SI9000, okuyithuluzi elihle lokubala impedance yesici futhi manje isetshenziswa amafemu amaningi e-PCB.

Lapho kubalwa impedance yesici sesiginali yangaphakathi yomugqa wokuhlukanisa nolayini owodwa wokugcina, uzothola umehluko omncane kuphela phakathi kwePolar SI9000 ne-Allegro ngenxa yeminye imininingwane, njengokuma kwengxenye yesiphambano setambo. Kodwa-ke, uma kuzobalwa i-impedance yesici sesiginali ye-Surface, ngiphakamisa ukuthi ukhethe imodeli Eboshwe esikhundleni semodeli ye-Surface, ngoba amamodeli anjalo abhekela ubukhona besendlalelo sokumelana nesoder, ngakho-ke imiphumela izoba nenembile. Okulandelayo isithombe-skrini esinqunyelwe se-impedance yomugqa wokwahlukaniswa komhlaba obalwe nePolar SI9000 kubhekwa ungqimba lokumelana ne-solder:

Ungayilawula kanjani i-PCB wiring impedance

Njengoba ukushuba kwesendlalelo se-solder resist kungalawulwa kalula, indlela eseduze nayo ingasetshenziswa, njengoba kunconyiwe ngumkhiqizi webhodi: khipha inani elithile kusibalo semodeli ye-Surface. Kunconywa ukuthi i-impedance umehluko ibe ngu-8 ohms kanye ne-single-end impedance ibe ngu-2 ohms.

Izidingo ezihlukile ze-PCB zezintambo

(1) Thola imodi yezintambo, amapharamitha nokubalwa kwe-impedance. Kunezinhlobo ezimbili zezindlela zokwehluka komugqa womzila: imodi yongqimba lwangaphandle lwe-microstrip mode kanye nemodi yomehluko womugqa wesendlalelo sangaphakathi. Impedance ingabalwa ngesoftware yokubala ehlobene ye-impedance (efana ne-POLAR-SI9000) noma ifomula yokubalwa kwe-impedance ngokuhlelwa kwepharamitha okufanelekile.

(2) Imigqa ehambisanayo ye-isometric. Thola ububanzi bomugqa nezikhala, bese ulandela ngokuqinile ububanzi bomugqa obaliwe nezikhala lapho kuhanjiswa umzila. Isikhala phakathi kwemigqa emibili kufanele sihlale singashintshi, okungukuthi, ukugcina ukufana. Kunezindlela ezimbili zokufana: enye ukuthi imigqa emibili ihamba ngohlaka olufanayo ngohlangothi, kanti enye ukuthi imigqa emibili ihamba kusendlalelo olungaphezulu. Ngokuvamile zama ukugwema ukusebenzisa isignali yomehluko phakathi kwezendlalelo, okungukuthi ngoba ekucutshungweni kwangempela kwe-PCB kunqubo, ngenxa yokunemba kokulungiswa kokulungiswa okune-laminated kuncane kakhulu kunalokho okuhlinzekwe phakathi kokunemba kwe-etching, nasenqubeni yokulahleka kuketshezi okunamathiselwe, akunakuqinisekisa ukuthi ukwehlukaniswa komugqa kuyalingana nobukhulu be-dielectric ye-interlayer, kuzodala umehluko phakathi kwezendlalelo zokwehluka koshintsho lwe-impedance. Kunconywa ukusebenzisa umehluko ngaphakathi kwesendlalelo esifanayo ngangokunokwenzeka.