Ekwakhiweni kwe-PCB, ukuhambisana kwe-electromagnetic (EMC) kanye nokuphazamiseka kazibuthe kagesi okuhlobene (EMI) bekulokhu kuyizinkinga ezimbili ezinkulu ezibangele onjiniyela baphathwe yikhanda, ikakhulukazi ekwakhiweni kwebhodi lesifunda lanamuhla kanye nokupakishwa kwezingxenye kuyancipha, kanti ama-OEM adinga Isimo sezinhlelo zesivinini esiphezulu.
1. I-Crosstalk ne-wiring amaphuzu abalulekile
I-wiring ibaluleke kakhulu ukuqinisekisa ukugeleza okujwayelekile kwamandla. Uma i-current ivela ku-oscillator noma enye idivayisi efanayo, kubaluleke kakhulu ukugcina okwamanje ihlukile endizeni yaphansi, noma ukungavumeli ukusebenza kwamanje kuhambisane nomunye umkhondo. Amasiginali amabili ahambisanayo anesivinini esikhulu azokhiqiza i-EMC ne-EMI, ikakhulukazi i-crosstalk. Indlela yokumelana kufanele ibe mfushane kakhulu, futhi indlela yamanje yokubuya kufanele ibe mfushane ngangokunokwenzeka. Ubude bomzila wokulandela umkhondo kufanele bufane nobude bokulandelela okuthunyelwe.
Ku-EMI, enye ibizwa ngokuthi "izintambo ezeqiwe" kanti enye "izintambo ezihlukumezekile". Ukuhlanganiswa kwe-inductance namandla kuzothinta umkhondo "oyisisulu" ngenxa yokuba khona kwezinkundla zikazibuthe, ngaleyo ndlela kukhiqize imisinga eya phambili futhi ehlehlayo "ku-trace yesisulu". Kulesi simo, ama-ripples azokhiqizwa endaweni ezinzile lapho ubude bokudlulisela kanye nobude bokwamukela kwesiginali kucishe kulingane.
Endaweni yezintambo ezilinganiswe kahle futhi ezinzile, imisinga ebangelwe kufanele ikhansele ngaphandle ukuze kuqedwe i-crosstalk. Nokho, siphila ezweni elingaphelele, futhi izinto ezinjalo ngeke zenzeke. Ngakho-ke, umgomo wethu uwukugcina i-crosstalk yawo wonke ama-trace incane. Uma ububanzi phakathi kwemigqa ehambisanayo buphindwe kabili ububanzi bemigqa, umphumela we-crosstalk ungancishiswa. Isibonelo, uma ububanzi bokulandelela bungama-mils angu-5, ibanga elincane phakathi kokulandela umkhondo okubili okuhambisanayo kufanele libe ama-mils angu-10 noma ngaphezulu.
Njengoba izinto ezintsha nezinto ezintsha ziqhubeka nokuvela, abaklami be-PCB kufanele baqhubeke nokubhekana nezinkinga zokuhambisana nozibuthe kagesi kanye nokuphazamiseka.
2. I-Decoupling capacitor
I-Decoupling capacitor inganciphisa imiphumela emibi ye-crosstalk. Kufanele abekwe phakathi kwephinikhodi yokunikeza amandla kanye nephinikhodi yaphansi yedivayisi ukuze kuqinisekiswe ukuthikamezeka kwe-AC okuphansi futhi kunciphise umsindo ne-crosstalk. Ukuze uthole i-impedance ephansi phezu kwebanga elibanzi, ama-decoupling capacitor amaningi kufanele asetshenziswe.
Isimiso esibalulekile sokubeka ama-decoupling capacitor ukuthi i-capacitor enevelu ye-capacitance encane kakhulu kufanele ibe seduze ngangokunokwenzeka kudivayisi ukuze kuncishiswe umphumela we-inductance kumkhondo. Le capacitor ethile iseduze kakhulu nephinikhodi yamandla noma umkhondo wamandla wedivayisi, futhi ixhuma iphedi ye-capacitor ngqo endizeni edlula noma ephansi. Uma umkhondo umude, sebenzisa izindlela eziningi ukuze unciphise ukuvinjelwa komhlaba.
3. Gcoba i-PCB
Indlela ebalulekile yokunciphisa i-EMI ukuklama indiza ephansi ye-PCB. Isinyathelo sokuqala ukwenza indawo ephansi ibe yinkulu ngangokunokwenzeka phakathi nendawo ephelele yebhodi lesifunda le-PCB, elinganciphisa ukukhishwa, ukungqubuzana nomsindo. Kufanele kuqashelwe ngokukhethekile lapho kuxhunywa ingxenye ngayinye endaweni ephansi noma endizeni ephansi. Uma lokhu kungenziwanga, umphumela wokunciphisa indiza yaphansi ethembekile ngeke usetshenziswe ngokugcwele.
Idizayini eyinkimbinkimbi ye-PCB inama-voltage amaningana azinzile. Ngokufanelekile, i-voltage ngayinye yereferensi inendiza yayo yaphansi ehambelana nayo. Kodwa-ke, uma ungqimba lomhlabathi luningi kakhulu, luzonyusa izindleko zokukhiqiza ze-PCB futhi lenze intengo ibe phezulu kakhulu. Isivumelwano siwukusebenzisa izindiza ezingaphansi ezindaweni ezintathu kuya kweziyisihlanu ezihlukene, futhi indiza ephansi ngayinye ingaba nezingxenye eziningi eziphansi. Lokhu akulawuli kuphela izindleko zokukhiqiza zebhodi lesifunda, kodwa futhi kunciphisa i-EMI ne-EMC.
Uma ufuna ukunciphisa i-EMC, uhlelo oluphansi lwe-impedance grounding lubaluleke kakhulu. Ku-PCB enezingqimba eziningi, kungcono kakhulu ukuba nendiza yaphansi enokwethenjelwa, kunokuba intshontshe ithusi noma indiza yaphansi ehlakazekile, ngoba ine-impedance ephansi, inganikeza indlela yamanje, iwumthombo wesignali ohlanekezelayo.
Ubude besikhathi lapho isignali ibuyela phansi nayo ibaluleke kakhulu. Isikhathi esiphakathi kwesignali nomthombo wesiginali kufanele silingane, ngaphandle kwalokho izokhiqiza into efana ne-antenna, yenze amandla akhazimulayo abe yingxenye ye-EMI. Ngokufanayo, ukulandelelwa okudlulisa okwamanje kuya/kusuka kumthombo wesignali kufanele kube kufushane ngangokunokwenzeka. Uma ubude bomzila womthombo nendlela yokubuya kungalingani, kuzokwenzeka ukugxuma komhlaba, okuzokwenza futhi i-EMI.
4. Gwema i-engeli engu-90°
Ukuze wehlise i-EMI, gwema izintambo, i-vias nezinye izingxenye ezenza i-engeli engu-90°, ngoba ama-engeli angakwesokudla azokhipha imisebe. Kulelikhona, amandla azokhuphuka, futhi i-impedance yesici nayo izoshintsha, okuholela ekuboniseni bese kuba yi-EMI. Ukuze ugweme ama-engeli angu-90°, imikhondo kufanele ihanjiswe emakhoneni okungenani ngama-engeli amabili angu-45°.
5. Sebenzisa ngokuqaphela
Cishe kuzo zonke izakhiwo ze-PCB, i-vias kufanele isetshenziselwe ukuhlinzeka ngoxhumano oluqhuba phakathi kwezendlalelo ezihlukene. Onjiniyela besakhiwo se-PCB badinga ukuqaphela ikakhulukazi ngoba i-vias izokhiqiza i-inductance namandla. Kwezinye izimo, zizophinde zikhiqize ukuboniswa, ngoba isici sizoshintsha lapho i-via yenziwa ngomkhondo.
Futhi khumbula ukuthi i-vias izokwandisa ubude bokulandelela futhi idinga ukufaniswa. Uma kuwumkhondo ohlukile, i-vias kufanele igwenywe ngangokunokwenzeka. Uma ingenakugwenywa, sebenzisa i-vias kukho kokubili ukulandelelwa ukuze unxephezele ukubambezeleka kwesignali nendlela yokubuya.
6. Ikhebula nokuvikela ngokomzimba
Amakhebuli aphethe amasekhethi edijithali namaza e-analog azokhiqiza amandla e-parasitic kanye ne-inductance, okubangela izinkinga eziningi ezihlobene ne-EMC. Uma kusetshenziswa ikhebula elisontekile, izinga lokuhlanganisa lizogcinwa liphansi futhi inkambu kazibuthe ekhiqiziwe izosuswa. Ukuze uthole amasignali amaza aphezulu, ikhebula elivikelekile kufanele lisetshenziswe, futhi intambo yangaphambili nangemuva kufanele ibekwe phansi ukuze kuqedwe ukuphazamiseka kwe-EMI.
Ukuvikela okungokoqobo ukusonga yonke noma ingxenye yesistimu ngephakheji yensimbi ukuvimbela i-EMI ukuthi ingangeni kumjikelezo we-PCB. Lolu hlobo lokuvikela lufana nesiqukathi sokuhambisa esivaliwe, esinciphisa usayizi weluphu ye-antenna futhi sibambe i-EMI.