Pamapangidwe a PCB, kuyanjana kwa ma elekitiromu (EMC) ndi kusokoneza kokhudzana ndi ma elekitiroma (EMI) nthawi zonse zakhala zovuta ziwiri zazikulu zomwe zapangitsa akatswiri kupwetekedwa mutu, makamaka pamapangidwe a board ozungulira masiku ano komanso kuyika kwa zigawo zikucheperachepera, ndipo ma OEM amafunikira masinthidwe othamanga kwambiri.
1. Crosstalk ndi mawaya ndi mfundo zazikuluzikulu
Mawaya ndi ofunikira kwambiri kuti atsimikizire kuti madzi akuyenda bwino. Ngati mphamvuyi imachokera ku oscillator kapena chipangizo china chofananira, ndikofunikira kwambiri kuti pakali pano ikhale yosiyana ndi ndege yapansi, kapena kuti musalole kuti yapano ifanane ndi njira ina. Zizindikiro ziwiri zofananira zothamanga kwambiri zidzatulutsa EMC ndi EMI, makamaka crosstalk. Njira yotsutsa iyenera kukhala yayifupi kwambiri, ndipo njira yobwereranso iyenera kukhala yayifupi momwe mungathere. Kutalika kwa njira yobwerera kumayenera kukhala yofanana ndi kutalika kwa njira yotumizira.
Kwa EMI, imodzi imatchedwa "wiring yophwanyidwa" ndipo ina ndi "wiring wozunzidwa". Kulumikizana kwa inductance ndi capacitance kudzakhudza kufufuza kwa "wozunzidwa" chifukwa cha kukhalapo kwa ma electromagnetic fields, potero kumapanga kutsogolo ndi kubwezera mafunde pa "victim trace". Pankhaniyi, ma ripples adzapangidwa m'malo okhazikika pomwe kutalika kwa kufalikira ndi kutalika kwa chizindikirocho kumakhala kofanana.
Pamalo olumikizana bwino komanso okhazikika mawaya, mafunde omwe apangitsidwa ayenera kusokonezana kuti athetse crosstalk. Komabe, tili m’dziko lopanda ungwiro, ndipo zimenezi sizidzachitika. Chifukwa chake, cholinga chathu ndikuchepetsa mikangano yamitundu yonse. Ngati m'lifupi pakati pa mizere yofanana ndi yowirikiza kawiri m'lifupi mwake, zotsatira za crosstalk zitha kuchepetsedwa. Mwachitsanzo, ngati m'lifupi mwake ndi 5 mils, mtunda wochepera pakati pa njira ziwiri zofananira uyenera kukhala 10 mils kapena kupitilira apo.
Pomwe zida zatsopano ndi zida zatsopano zikupitilira kuwonekera, opanga PCB akuyenera kupitiliza kuthana ndi zovuta zamaginito ndi kusokoneza.
2. Decoupling capacitor
Decoupling capacitors amatha kuchepetsa zotsatira zoyipa za crosstalk. Ayenera kukhala pakati pa pini yamagetsi ndi pini yapansi ya chipangizocho kuti atsimikizire kutsika kwa AC ndikuchepetsa phokoso ndi crosstalk. Kuti mukwaniritse kutsika kwapang'onopang'ono pama frequency angapo, ma decoupling capacitor angapo ayenera kugwiritsidwa ntchito.
Mfundo yofunikira pakuyika ma capacitor ophatikizika ndikuti capacitor yokhala ndi mtengo wocheperako iyenera kukhala pafupi kwambiri ndi chipangizocho kuti muchepetse zotsatira za inductance pakufufuza. Capacitor iyi ili pafupi kwambiri ndi pini yamagetsi kapena kufufuza mphamvu kwa chipangizocho, ndikugwirizanitsa pad ya capacitor molunjika ku ndege kapena pansi. Ngati njirayo ndi yayitali, gwiritsani ntchito njira zingapo kuti muchepetse kutsekeka kwa nthaka.
3. Gwirani PCB
Njira yofunikira yochepetsera EMI ndikupanga ndege yapansi ya PCB. Gawo loyamba ndikupangitsa malo oyambira kukhala akulu momwe angathere mkati mwa gulu lonse la PCB, zomwe zitha kuchepetsa kutulutsa, kuphatikizika ndi phokoso. Chisamaliro chapadera chiyenera kutengedwa pamene mukugwirizanitsa chigawo chilichonse kumalo apansi kapena pansi. Ngati izi sizichitika, zotsatira zowononga za ndege yodalirika sizidzagwiritsidwa ntchito mokwanira.
Mapangidwe ovuta kwambiri a PCB ali ndi ma voltages angapo okhazikika. Momwemo, voteji iliyonse yowunikira imakhala ndi ndege yake yofananira. Komabe, ngati nthaka wosanjikiza kwambiri, izo kuonjezera kupanga mtengo wa PCB ndi kupanga mtengo kwambiri. Kugwirizana ndiko kugwiritsa ntchito ndege zapansi m'malo atatu kapena asanu, ndipo ndege iliyonse yapansi imatha kukhala ndi magawo angapo apansi. Izi sizimangoyang'anira mtengo wopanga bwalo lozungulira, komanso zimachepetsa EMI ndi EMC.
Ngati mukufuna kuchepetsa EMC, njira yochepetsera yotsika ndiyofunikira kwambiri. Mu PCB yamitundu yambiri, ndi bwino kukhala ndi ndege yapansi yodalirika, m'malo moba mkuwa kapena ndege yamwazikana, chifukwa ili ndi impedance yochepa, ikhoza kupereka njira yamakono, ndiye gwero labwino kwambiri la reverse signal .
Kutalika kwa nthawi yomwe chizindikirocho chikubwerera pansi ndikofunikanso kwambiri. Nthawi pakati pa chizindikiro ndi gwero la chizindikirocho iyenera kukhala yofanana, mwinamwake idzatulutsa chodabwitsa chofanana ndi mlongoti, kupanga mphamvu yowunikira kukhala gawo la EMI. Mofananamo, zizindikiro zomwe zimatumiza panopa kupita / kuchokera kugwero lazizindikiro ziyenera kukhala zazifupi momwe zingathere. Ngati kutalika kwa njira yoyambira ndi njira yobwerera sikufanana, kuphulika kwapansi kudzachitika, komwe kudzapanganso EMI.
4. Pewani ngodya ya 90 °
Kuti muchepetse EMI, pewani waya, vias ndi zigawo zina zomwe zimapanga ngodya ya 90 °, chifukwa ngodya zolondola zidzatulutsa ma radiation. Pa ngodya iyi, mphamvu idzawonjezeka, ndipo mawonekedwe amtunduwu adzasinthanso, zomwe zimatsogolera ku ziwonetsero kenako EMI. Kuti mupewe ma angles a 90 °, mipata iyenera kuyendetsedwa kumakona osachepera awiri a 45 °.
5. Gwiritsani ntchito kudzera mosamala
Pafupifupi masanjidwe onse PCB, vias ayenera kugwiritsidwa ntchito kupereka kugwirizana conductive pakati zigawo zosiyanasiyana. Opanga masanjidwe a PCB akuyenera kukhala osamala kwambiri chifukwa vias amatulutsa inductance ndi capacitance. Nthawi zina, amatulutsanso zowunikira, chifukwa mawonekedwe amtunduwu amatha kusintha pomwe njira ikapangidwa motsatira.
Komanso kumbukirani kuti vias adzawonjezera kutalika kwa kufufuza ndi ayenera zikugwirizana. Ngati ndi njira yosiyana, ma vias ayenera kupewedwa momwe angathere. Ngati sichingapewedwe, gwiritsani ntchito vias muzotsatira zonse ziwiri kuti mubwezere kuchedwa kwa chizindikiro ndi njira yobwerera.
6. Chingwe ndi chitetezo chakuthupi
Zingwe zonyamula mabwalo a digito ndi mafunde a analogi zimatulutsa mphamvu ya parasitic ndi inductance, zomwe zimayambitsa zovuta zambiri zokhudzana ndi EMC. Ngati chingwe chopotoka chikugwiritsidwa ntchito, mulingo wolumikizira umakhala wotsika ndipo mphamvu ya maginito yopangidwa idzathetsedwa. Pazidziwitso zothamanga kwambiri, chingwe chotetezedwa chiyenera kugwiritsidwa ntchito, ndipo kutsogolo ndi kumbuyo kwa chingwecho ziyenera kukhazikitsidwa kuti zithetse kusokoneza kwa EMI.
Kuteteza thupi ndikukulunga zonse kapena gawo la dongosolo ndi phukusi lachitsulo kuti EMI isalowe mudera la PCB. Kutchinjiriza kotereku kuli ngati chidebe chotsekeka chotsekeka, chomwe chimachepetsa kukula kwa mlongoti ndikutenga EMI.