Menene tsarin sarrafa impedance da kuma yadda ake sarrafa impedance akan PCBs

A cikin ƙirar na'urorin lantarki na zamani, PCBs suna taka muhimmiyar rawa. Aikin PCBs kai tsaye yana shafar kwanciyar hankali, aminci da ingancin watsawa na tsarin lantarki gaba ɗaya. Daga cikinsu, sarrafa impedance muhimmin ɓangare ne na ƙirar PCB. Tunda da'irori na dijital na zamani suna da gajerun lokutan watsa sigina da ƙimar agogo mafi girma, alamun PCB ba su zama haɗin kai mai sauƙi ba, amma layukan watsawa daidai gwargwado. Kula da impedance na PCB yana nufin sarrafa saurin watsawa da daidaita impedance na sigina akan PCB don tabbatar da inganci da kwanciyar hankali na watsa sigina.

A cikin yanayi na aiki, ya zama dole a sarrafa juriyar bin diddigin lokacin da saurin gefen dijital ya fi 1ns ko kuma mitar analog ya wuce 300MHz. Ɗaya daga cikin mahimman sigogi na alamar PCB shine juriyar halayyarsa (watau rabon ƙarfin lantarki zuwa halin yanzu lokacin da aka watsa raƙuman ruwa ta hanyar layin watsa sigina). Halayen juriyar wayoyi akan PCBs muhimmin alama ne na ƙirar PCB. Musamman a cikin ƙirar PCB mai yawan mita, ya zama dole a yi la'akari da ko juriyar halayyar wayar ta yi daidai da ko ta dace da juriyar halayyar da ake buƙata ta na'urar ko siginar. Wannan ya ƙunshi ra'ayoyi 2: sarrafa juriya da daidaita juriya. Wannan labarin ya mayar da hankali kan batutuwan sarrafa juriya da ƙirar tari.

Akwai sigina daban-daban da ake watsawa a cikin masu sarrafa PCB. Domin inganta saurin watsa shi, dole ne a ƙara mitarsa. Ƙimar hana motsi na da'irar kanta ta bambanta saboda abubuwa kamar etching, kauri na Layer da faɗin waya, da sauransu, wanda ke haifar da karkacewar sigina. Saboda haka, ya kamata a sarrafa ƙimar hana motsi na masu sarrafa PCB masu sauri a cikin wani takamaiman iyaka, wanda ake kira "ikon sarrafa impedance".

Ana tantance tasirin tasirin PCB ta hanyar inductive da capacitive inductance, juriya da kuma coefficient conductivity. Abubuwan da ke shafar tasirin tasirin PCB sun haɗa da faɗi da kauri na wayar jan ƙarfe, ma'aunin dielectric da kauri na matsakaici, kauri na solder pad, hanyar wayar ƙasa, da wayoyi a kusa da wayoyi, da sauransu. Kewayon tasirin PCB shine 25 zuwa 120 ohms.

A aikace, layukan watsawa na PCB galibi suna ƙunshe da hanyar waya, layuka ɗaya ko fiye na tunani, da kayan rufi. Alamun da layin suna samar da tasirin sarrafawa. PCBs galibi suna ɗaukar tsarin layuka da yawa, kuma ana iya gina ikon sarrafa impedance ta hanyoyi daban-daban. Duk da haka, ba tare da la'akari da hanyar da aka yi amfani da ita ba, ƙimar impedance za a ƙayyade ta tsarin zahiri da halayen lantarki na kayan rufi:

Microstrip wani tsiri ne na waya wanda ke nufin layin watsawa wanda gefe ɗaya kawai ke da jirgin tunani. Sama da gefen suna fuskantar iska (ko kuma an rufe su) kuma suna kan saman wani ma'aunin rufi na Er PCB, tare da wutar lantarki ko layin ƙasa a matsayin nuni. Kamar yadda aka nuna a cikin hoton da ke ƙasa:

Lura: A cikin ainihin masana'antar PCB, masana'antar PCB yawanci tana shafa wani tawada kore a saman PCB. Saboda haka, a cikin ainihin lissafin impedance, samfurin da aka nuna a cikin hoto mai zuwa yawanci ana amfani da shi don layukan microstrip na saman.

Layin layi wani tsiri ne na waya da aka sanya tsakanin jiragen sama guda biyu masu ma'ana, kamar yadda aka nuna a cikin hoton da ke ƙasa. Ma'aunin dielectric na dielectric da H1 da H2 suka wakilta na iya bambanta.

Lambobin da ke sama guda biyu kawai misali ne na microstrip da striplines, waɗanda galibi ake amfani da su don koyon kayan aikin IoT masu hankali da sauran tsarin. Akwai nau'ikan microstrip da striplines da yawa, kamar microstrip mai rufi, waɗanda ke da alaƙa da takamaiman tsarin tara PCBs.

Lissafin da ake amfani da shi don ƙididdige impedance na halaye yana buƙatar lissafin lissafi mai rikitarwa, yawanci yana amfani da hanyoyin warware filin, gami da nazarin abubuwan iyaka. Saboda haka, tare da amfani da software na ƙididdige impedance na musamman SI9000, abin da kawai muke buƙatar yi shine sarrafa sigogin impedance na halaye:

Er mai ƙarfi na dielectric na layin rufi, faɗin wayoyi W1 da W2 (trapezoidal), kauri na wayoyi T, da kauri na layin rufi H.

Faɗin layin da aka tsara na W

A - asarar etch (duba tebur a sama)

Dalilin da ya sa faɗin da bai dace ba tsakanin saman da ƙasan layin shine cewa yayin da ake kera PCBs, tsatsa tana faruwa daga sama zuwa ƙasa, wanda ke haifar da siffar trapezoidal ta layin da ya lalace.

Akwai dangantaka mai dacewa tsakanin kauri layin T da kauri na jan ƙarfe na wannan Layer, kamar haka:

* Saboda ƙaramin tasirin kauri abin rufe fuska na solder akan impedance, ana ɗauka cewa ƙimarsa koyaushe ita ce mil 0.5.

Za mu iya cimma ikon sarrafa impedance ta hanyar sarrafa waɗannan sigogi. Idan muka ɗauki PCB na ƙasa na Anwei a matsayin misali, za mu yi bayanin matakan sarrafa impedance da amfani da SI9000:

Layi na biyu shine ƙasa, layi na biyar shine wutar lantarki, sauran layi kuma sune layi na sigina.

Bayani: Dielectric tsakanin matakan tsakiya shine FR-4, tare da dielectric constant na 4.2; saman da ƙasan layukan sune yadudduka marasa komai waɗanda ke haɗuwa kai tsaye da iska, kuma dielectric constant na iska shine 1.

Masu ƙira na PCB za su iya amfani da tsarin tsari na PCB gaba ɗaya don cimma ikon sarrafa impedance. Ta hanyar sanya layukan sigina daban-daban a wurare daban-daban na yadudduka, ana iya sarrafa capacitance da inductance na tsakanin layukan. Gabaɗaya, Layer na ciki yana amfani da kayan impedance masu ƙarfi kuma Layer na waje yana amfani da kayan impedance masu ƙarancin ƙarfi don rage tasirin tunani da magana ta hanyar haɗin gwiwa.

Layukan watsa siginar bambance-bambance na iya samar da ingantaccen ikon hana tsangwama da kuma ƙarancin haɗarin yin magana a tsakanin mutane. Layukan watsa siginar bambance-bambancen wayoyi ne masu layi ɗaya waɗanda ke da ƙarfin lantarki daban-daban amma suna da girma iri ɗaya, waɗanda zasu iya samar da ingantaccen sigina da ikon hana tsangwama. Yawancin lokaci ana sarrafa juriyar layukan watsa siginar bambance-bambance ta hanyar zaɓar tazara tsakanin layi, faɗi da kuma ƙasa.

Haka kuma ana iya amfani da sigogin geometric kamar faɗin layin PCB, tazara da tsari don sarrafa impedance. Ga layukan microstrip na gama gari, faɗin layi mai kauri da babban tazara na iya rage impedance. Ga layukan coaxial, ƙananan diamita na layin ciki da manyan radius na layin waje na iya ƙara impedance. Zaɓin tsarin wayoyi yana buƙatar haɓakawa bisa ga takamaiman buƙatun impedance da mitar sigina.

Tsarin dielectric na kayan PCB shima yana shafar impedance. Zaɓin kayan da ke da kaddarorin dielectric mai karko wani ɓangare ne na sarrafa impedance. A cikin aikace-aikacen mita mai yawa da sauri, kayan da aka fi amfani da su sun haɗa da FR-4 (allon fiber gilashi mai ƙarfafawa), PTFE (polytetrafluoroethylene), da laminates RF (mitar rediyo).

Kafin a tsara PCB, amfani da kayan aikin kwaikwayo da ƙira na iya taimaka wa masu zane su tabbatar da inganci da sauri. Waɗannan kayan aikin na iya kwaikwayon halayen da'ira, asarar watsa sigina da hulɗar lantarki don tantance mafi kyawun sigogin ƙirar PCB. Wasu kayan aikin kwaikwayo na yau da kullun sun haɗa da CST Studio Suite, HyperLynx da ADS.

Kula da impedance na PCB yana taka muhimmiyar rawa a cikin da'irorin dijital da analog masu sauri. Ta hanyar ƙira mai ma'ana, amfani da layukan watsa siginar daban-daban, sarrafa tsarin wayoyi, zaɓar kayan PCB masu dacewa, da kuma amfani da kayan aikin kwaikwayo da ƙira, ana iya cimma daidaitaccen ikon sarrafa impedance, ta haka ne za a inganta aikin da'irar da amincin sigina.