Kodi kulamulira impedance ndi chiyani komanso momwe mungachitire kulamulira impedance pa ma PCB

Pakupanga zipangizo zamagetsi zamakono, ma PCB amachita gawo lofunika kwambiri. Kugwira ntchito kwa ma PCB kumakhudza mwachindunji kukhazikika, kudalirika, komanso kugwira ntchito bwino kwa makina onse amagetsi. Pakati pawo, kulamulira kwa impedance ndi gawo lofunika kwambiri pakupanga ma PCB. Popeza ma digito amakono ali ndi nthawi yochepa yotumizira ma signal komanso kuchuluka kwa mawotchi, ma PCB trace si maulumikizidwe osavuta, koma mizere yotumizira motsatana. Kulamulira kwa impedance ya PCB kumatanthauza kuwongolera liwiro lotumizira ndi kufananiza kwa impedance kwa ma signal pa PCB kuti zitsimikizire kuti kutumiza ma signal kuli bwino komanso kokhazikika.

Muzochitika zenizeni, ndikofunikira kuwongolera trace impedance pamene liwiro la digito la marginal lili pamwamba kuposa 1ns kapena ma frequency a analog akuposa 300MHz. Chimodzi mwazinthu zofunika kwambiri za PCB trace ndi kuletsa kwake kwapadera (monga chiŵerengero cha voltage ndi current pamene mafunde akutumizidwa pamzere wotumizira chizindikiro). Kuletsa kwapadera kwa mawaya pa ma PCB ndi chizindikiro chofunikira cha kapangidwe ka PCB. Makamaka pakupanga PCB ya ma frequency apamwamba, ndikofunikira kuganizira ngati kuletsa kwapadera kwa waya kukugwirizana kapena kukugwirizana ndi kuletsa kwapadera kwa chipangizo kapena chizindikiro. Izi zikuphatikizapo mfundo ziwiri: kulamulira kwa impedance ndi kufananiza kwa impedance. Nkhaniyi ikuyang'ana kwambiri nkhani za kulamulira kwa impedance ndi kapangidwe ka stack.

Pali zizindikiro zosiyanasiyana zomwe zimatumizidwa mu ma conductor a PCB. Kuti muwongolere kuchuluka kwa ma transmission ake, ma frequency ake ayenera kuwonjezeredwa. Mtengo wa impedance wa dera lokha umasiyana chifukwa cha zinthu monga kuchekeka, makulidwe a zigawo ndi m'lifupi mwa waya, ndi zina zotero, zomwe zimapangitsa kuti chizindikirocho chisokonezeke. Chifukwa chake, mtengo wa impedance wa ma conductor pa ma PCB othamanga kwambiri uyenera kulamulidwa mkati mwa mtundu winawake, womwe umatchedwa "impedance control".

Kulephera kwa ma PCB traces kumatsimikiziridwa ndi kutsika kwawo kwa inductive ndi capacitive, resistance ndi coefficient ya conductivity. Zinthu zomwe zimakhudza kulephera kwa mawaya a PCB makamaka zimaphatikizapo m'lifupi ndi makulidwe a waya wamkuwa, dielectric constant ndi makulidwe a medium, makulidwe a solder pad, njira ya waya wapansi, ndi mawaya ozungulira mawaya, ndi zina zotero. Mtundu wa kulephera kwa PCB ndi 25 mpaka 120 ohms.

Mwachizolowezi, mizere yotumizira ya PCB nthawi zambiri imakhala ndi waya, gawo limodzi kapena angapo ofunikira, ndi zipangizo zotetezera. Gawo ndi gawoli ndi zomwe zimapangitsa kuti pakhale kuletsa kolamulira. Ma PCB nthawi zambiri amagwiritsa ntchito mapangidwe amitundu yambiri, ndipo kuletsa kuletsa kungathenso kupangidwa m'njira zosiyanasiyana. Komabe, mosasamala kanthu za njira yomwe yagwiritsidwa ntchito, mtengo wa kuletsa kutsimikizika udzatsimikiziridwa ndi kapangidwe kake ka thupi ndi mphamvu zamagetsi za zinthu zotetezera:

Chingwe cha microstrip ndi chingwe cha waya chomwe chimatanthauza chingwe chotumizira chomwe mbali imodzi yokha ili ndi malo ofotokozera. Kumwamba ndi mbali zimawululidwa ndi mpweya (kapena zimakutidwa) ndipo zimakhala pamwamba pa Er PCB yokhazikika yotetezera kutentha, yokhala ndi mphamvu kapena gawo la pansi ngati chizindikiro. Monga momwe chithunzichi chikusonyezera:

Dziwani: Pakupanga PCB yeniyeni, fakitale ya PCB nthawi zambiri imaphimba inki yobiriwira pamwamba pa PCB. Chifukwa chake, pakuwerengera zenizeni za impedance, chitsanzo chomwe chawonetsedwa pachithunzi chotsatirachi nthawi zambiri chimagwiritsidwa ntchito pa mizere ya microstrip pamwamba.

Mzere wozungulira ndi mzere wa waya womwe umayikidwa pakati pa mizere iwiri yowunikira, monga momwe chithunzichi chikusonyezera. Zosasinthika za dielectric za dielectric zomwe zikuyimiridwa ndi H1 ndi H2 zitha kukhala zosiyana.

Milandu iwiri yomwe ili pamwambapa ndi chitsanzo cha microstrip ndi striplines, zomwe nthawi zambiri zimagwiritsidwa ntchito pophunzira zida zanzeru za IoT ndi machitidwe ena. Pali mitundu yambiri ya microstrip ndi striplines, monga coated microstrip, zomwe zimagwirizana ndi kapangidwe kake ka ma PCB.

Equation yomwe imagwiritsidwa ntchito kuwerengera characteristic impedance imafuna kuwerengera kwa masamu kovuta, nthawi zambiri pogwiritsa ntchito njira zothetsera mavuto m'munda, kuphatikizapo kusanthula kwa malire a zinthu. Chifukwa chake, pogwiritsa ntchito pulogalamu yapadera yowerengera impedance SI9000, chomwe tiyenera kuchita ndikulamulira magawo a characteristic impedance:

Chokhazikika cha dielectric Er cha insulation layer, wiring wiring m'lifupi W1 ndi W2 (trapezoidal), wiring thickness T, ndi insulation layer thickness H.

W - m'lifupi mwa mzere wopangidwa

Kutayika kwa etch (onani tebulo pamwambapa)

Chifukwa cha kusiyana kwa m'lifupi pakati pa pamwamba ndi pansi pa mzerewu ndichakuti panthawi yopanga ma PCB, dzimbiri limachitika kuchokera pamwamba mpaka pansi, zomwe zimapangitsa kuti mzere wozimiririka ukhale ngati trapezoidal.

Pali ubale wofanana pakati pa makulidwe a mzere T ndi makulidwe a mkuwa a wosanjikiza uwu, motere:

* Chifukwa cha kuchuluka kochepa kwa chigoba cha solder pa impedance, chimaganiziridwa kuti ndi mtengo wokhazikika wa 0.5mil.

Tikhoza kukwaniritsa kulamulira kwa impedance mwa kulamulira magawo awa. Potengera chitsanzo cha PCB ya Anwei, tifotokoza njira zowongolera impedance ndi kugwiritsa ntchito SI9000:

Gawo lachiwiri ndi gawo la pansi, gawo lachisanu ndi gawo la mphamvu, ndipo magawo otsala ndi magawo a chizindikiro.

Kufotokozera: Dielectric pakati pa zigawo zapakati ndi FR-4, yokhala ndi dielectric constant ya 4.2; Zigawo zapamwamba ndi zapansi ndi zigawo zopanda kanthu zomwe zimakumana mwachindunji ndi mpweya, ndipo dielectric constant ya mpweya ndi 1.

Opanga ma PCB amatha kugwiritsa ntchito bwino kapangidwe ka ma PCB kuti akwaniritse kulamulira kwa impedance. Mwa kuyika zigawo zosiyanasiyana za chizindikiro m'malo osiyanasiyana a zigawo, mphamvu ya interlayer ndi inductance zitha kuyendetsedwa bwino. Kawirikawiri, gawo lamkati limagwiritsa ntchito zipangizo zapamwamba za impedance ndipo gawo lakunja limagwiritsa ntchito zipangizo zochepa za impedance kuti lichepetse mphamvu ya kuwunikira ndi kulankhulana.

Mizere yotumizira ma signal osiyanasiyana ingapereke mphamvu yabwino yoletsa kusokoneza komanso kuchepetsa chiopsezo cholankhulana. Mizere yotumizira ma signal osiyanasiyana ndi mawaya awiri ofanana okhala ndi ma voltage osiyana koma kukula kofanana, komwe kungapereke umphumphu wabwino wa ma signal komanso mphamvu yoletsa kusokoneza. Kuletsa kwa mizere yotumizira ma signal osiyanasiyana nthawi zambiri kumayendetsedwa ndi kusankha malo a mzere, m'lifupi ndi pansi.

Magawo a geometri monga m'lifupi mwa mzere wa PCB, malo otalikirana ndi kapangidwe kake angagwiritsidwenso ntchito kuwongolera impedance. Pa mizere yodziwika bwino ya microstrip, m'lifupi mwa mzere wokhuthala ndi malo okulirapo zimatha kuchepetsa impedance. Pa mizere ya coaxial, mainchesi ang'onoang'ono amkati ndi ma radii akuluakulu akunja amatha kuwonjezera impedance. Kusankha ma wiring geometry kumafuna kukonzedwa kutengera zofunikira zenizeni za impedance ndi pafupipafupi ya chizindikiro.

Kukhazikika kwa dielectric kwa zinthu za PCB kumakhudzanso impedance. Kusankha zipangizo zomwe zili ndi mphamvu zokhazikika za dielectric ndi gawo la kulamulira impedance. Mu ntchito zama frequency apamwamba komanso othamanga kwambiri, zinthu zomwe zimagwiritsidwa ntchito nthawi zambiri zimaphatikizapo FR-4 (galasi fiber reinforced board), PTFE (polytetrafluoroethylene), ndi RF (radio frequency) laminates.

Asanapange PCB, kugwiritsa ntchito zida zoyeserera ndi mapangidwe kungathandize opanga kutsimikizira mwachangu komanso molondola ndikukonza impedance. Zida izi zimatha kutsanzira momwe dera limayendera, kutayika kwa ma signal transmission ndi kuyanjana kwa ma electromagnetic kuti adziwe magawo abwino kwambiri a kapangidwe ka PCB. Zida zina zodziwika bwino zoyeserera zimaphatikizapo CST Studio Suite, HyperLynx ndi ADS.

Kuwongolera impedance ya PCB kumachita gawo lofunikira kwambiri pama circuits a digito ndi analog othamanga kwambiri. Kudzera mu kapangidwe koyenera ka hierarchical, kugwiritsa ntchito mizere yolumikizira ma signal, kuwongolera mawaya, kusankha zida zoyenera za PCB, komanso kugwiritsa ntchito zida zoyeserera ndi kapangidwe, kuwongolera impedance molondola kumatha kuchitika, motero kukonza magwiridwe antchito a circuit ndi umphumphu wa ma signal.