Kodi mukudziwa momwe mungathetsere vuto la EMI mukapanga ma PCB amitundu yambiri?
Ndikuuzeni!
Pali njira zambiri zothetsera mavuto a EMI.Njira zamakono za EMI kupondereza zikuphatikizapo: kugwiritsa ntchito EMI kupondereza ❖ kuyanika, kusankha zoyenera EMI kupondereza mbali ndi EMI kayeseleledwe kayeseleledwe.Kutengera masanjidwe ofunikira kwambiri a PCB, pepalali likukambirana za ntchito ya PCB powongolera ma radiation a EMI ndi luso la mapangidwe a PCB.
basi yamagetsi
Kudumpha kwamagetsi a IC kumatha kufulumizitsidwa poyika mphamvu yoyenera pafupi ndi pini yamagetsi ya IC.Komabe, awa si mapeto a vuto.Chifukwa cha kuyankha kwafupipafupi kwa capacitor, ndizosatheka kuti capacitor ipange mphamvu ya harmonic yofunikira kuyendetsa kutulutsa kwa IC moyera mu gulu lonse la frequency.Kuphatikiza apo, voteji yosakhalitsa yomwe imapangidwa pabasi yamagetsi imapangitsa kutsika kwamagetsi kumapeto onse a inductance ya njira yolumikizira.Ma voltages osakhalitsa awa ndiye njira yayikulu yolumikizira EMI.Nanga tingathetse bwanji mavuto amenewa?
Pankhani ya IC pa bolodi yathu yozungulira, mphamvu yosanjikiza yozungulira IC imatha kuonedwa ngati yabwino kwambiri yamagetsi, yomwe imatha kusonkhanitsa mphamvu zomwe zimatulutsidwa ndi discrete capacitor yomwe imapereka mphamvu zambiri zotulutsa zoyera.Kuonjezera apo, inductance ya mphamvu yosanjikiza bwino ndi yaying'ono, kotero chizindikiro chosakhalitsa chopangidwa ndi inductor chimakhalanso chaching'ono, motero kuchepetsa wamba mode EMI.
Zoonadi, kugwirizana pakati pa gawo lamagetsi ndi pini yamagetsi ya IC iyenera kukhala yayifupi momwe zingathere, chifukwa kukwera m'mphepete mwa chizindikiro cha digito ndi mofulumira komanso mofulumira.Ndibwino kuti mulumikize mwachindunji ku pad komwe kuli pini ya mphamvu ya IC, yomwe iyenera kukambidwa mosiyana.
Kuti muwongolere EMI wamba, gawo lamagetsi liyenera kukhala lopangidwa bwino la zigawo zamphamvu kuti zithandizire kuphatikizika ndikukhala ndi inductance yotsika mokwanira.Anthu ena angafunse kuti, ndi zabwino bwanji?Yankho limadalira gawo la mphamvu, zinthu zomwe zili pakati pa zigawozo, ndi mafupipafupi ogwiritsira ntchito (ie, ntchito ya IC kukwera nthawi).Nthawi zambiri, masinthidwe a magawo amagetsi ndi 6mil, ndipo cholumikizira ndi zinthu za FR4, kotero mphamvu yofananira pa inchi imodzi ya mphamvu ndi pafupifupi 75pF.Mwachiwonekere, malo ang'onoang'ono a magawo ang'onoang'ono amakula kwambiri.
Palibe zida zambiri zokhala ndi nthawi yokwera ya 100-300ps, koma malinga ndi momwe IC ikukulirakulira, zida zokhala ndi nthawi yokwera mu 100-300ps zitenga gawo lalikulu.Kwa mabwalo okhala ndi 100 mpaka 300 PS nthawi yokwera, 3 mil wosanjikiza masitayilo sakugwiranso ntchito pamapulogalamu ambiri.Panthawiyo, ndikofunikira kutengera ukadaulo wa delamination wokhala ndi masitayilo apakati osakwana 1mil, ndikusintha ma dielectric a FR4 ndi zinthu zokhala ndi dielectric pafupipafupi.Tsopano, zoumba ndi mapulasitiki potted akhoza kukwaniritsa zofunika mapangidwe 100 mpaka 300ps kukwera nthawi maulendo.
Ngakhale zida zatsopano ndi njira zingagwiritsidwe ntchito m'tsogolomu, 1 mpaka 3 ns kukwera maulendo okwera nthawi, 3 mpaka 6 mil wosanjikiza malo, ndi zipangizo za dielectric FR4 nthawi zambiri zimakhala zokwanira kugwiritsira ntchito ma harmonics apamwamba ndi kupanga zizindikiro zosakhalitsa kukhala zochepa mokwanira, ndiko kuti. , wamba mode EMI akhoza kuchepetsedwa otsika kwambiri.Papepalali, chitsanzo cha mapangidwe a PCB wosanjikiza amaperekedwa, ndipo kusiyana kwapakati kumaganiziridwa kuti ndi 3 mpaka 6 mil.
electromagnetic chitetezo
Kuchokera pamawonedwe owonetserako, njira yabwino yosanjirira iyenera kukhala yoyika zizindikiro zonse mumagulu amodzi kapena angapo, omwe ali pafupi ndi mphamvu yamagetsi kapena ndege yapansi.Kwa magetsi, njira yabwino yosanjikiza iyenera kukhala kuti gawo la mphamvu liri pafupi ndi ndege yapansi, ndipo mtunda pakati pa mphamvu ya mphamvu ndi ndege yapansi iyenera kukhala yaying'ono momwe tingathere, zomwe timatcha njira "yosanjikiza".
Mtengo wa PCB
Ndi njira yanji ya stacking yomwe ingathandize kuteteza ndi kupondereza EMI?Chiwembu chotsatira cha stacking chimaganiza kuti mphamvu zamagetsi zimayenda pamtundu umodzi komanso kuti magetsi amodzi kapena ma voltages angapo amagawidwa m'madera osiyanasiyana a gawo limodzi.Nkhani ya magawo angapo amphamvu idzakambidwa pambuyo pake.
4-ply mbale
Pali zovuta zina zomwe zingatheke popanga 4-ply laminates.Choyamba, ngakhale chizindikiro cha chizindikirocho chili pamtunda wakunja ndipo mphamvu ndi ndege yapansi ili mkati, mtunda wapakati pa mphamvu ndi ndege yapansi udakali waukulu kwambiri.
Ngati mtengo wofunikira ndi woyamba, njira ziwiri zotsatirazi za bolodi zachikhalidwe za 4-ply zitha kuganiziridwa.Onse a iwo akhoza kusintha EMI kupondereza ntchito, koma ndi oyenera nkhani pamene kachulukidwe zigawo zikuluzikulu pa bolodi ndi otsika mokwanira ndipo pali malo okwanira kuzungulira zigawo zikuluzikulu (kuyika ❖ kuyanika mkuwa chofunika kwa magetsi).
Choyamba ndi chiwembu chokondedwa.Zigawo zakunja za PCB ndi zigawo zonse, ndipo zigawo ziwiri zapakati ndi zigawo za chizindikiro / mphamvu.Mphamvu yamagetsi pagawo la siginecha imayendetsedwa ndi mizere yotakata, zomwe zimapangitsa kuti kutsekeka kwa magetsi kutsika komanso kutsika kwa njira ya microstrip.Kuchokera pakuwona kuwongolera kwa EMI, iyi ndiye mawonekedwe abwino kwambiri a 4-wosanjikiza PCB omwe alipo.Pachiwembu chachiwiri, gawo lakunja limanyamula mphamvu ndi nthaka, ndipo gawo lapakati limanyamula chizindikiro.Poyerekeza ndi bolodi lachikale la 4-wosanjikiza, kukonza kwachiwembuchi ndikocheperako, ndipo interlayer impedance si yabwino ngati ya board 4-layer board.
Ngati wiring impedance iyenera kuwongoleredwa, dongosolo la stacking lomwe lili pamwambapa liyenera kusamala kwambiri kuti liyike mawaya pansi pa chilumba chamkuwa chamagetsi ndi kukhazikika.Kuphatikiza apo, chilumba chamkuwa pamagetsi kapena stratum chiyenera kulumikizidwa momwe zingathere kuti zitsimikizire kulumikizana pakati pa DC ndi ma frequency otsika.
6-ply mbale
Ngati kachulukidwe wa zigawo pa bolodi 4-wosanjikiza ndi lalikulu, mbale 6 wosanjikiza bwino.Komabe, kutchinga kwa ziwembu zina za stacking mu kapangidwe ka bolodi la 6-wosanjikiza sikuli kokwanira, ndipo chizindikiro chosakhalitsa cha basi yamagetsi sichimachepetsedwa.Zitsanzo ziwiri zikukambidwa pansipa.
Pachiyambi choyamba, magetsi ndi nthaka zimayikidwa mu gawo lachiwiri ndi lachisanu motsatira.Chifukwa mkulu impedance mkuwa atavala magetsi, ndi zoipa kwambiri kulamulira wamba mode EMI cheza.Komabe, pakuwona kuwongolera kwamphamvu kwa chizindikiro, njira iyi ndi yolondola kwambiri.
Mu chitsanzo chachiwiri, magetsi ndi nthaka zimayikidwa mu gawo lachitatu ndi lachinayi motsatira.Mapangidwe awa amathetsa vuto la copper clad impedance ya magetsi.Chifukwa cha kuchepa kwa chitetezo chamagetsi chamagetsi cha wosanjikiza 1 ndi wosanjikiza 6, njira yosiyanitsira EMI imawonjezeka.Ngati chiwerengero cha mizere chizindikiro pa zigawo ziwiri zakunja ndi wamng'ono ndi kutalika kwa mizere ndi lalifupi kwambiri (zosakwana 1/20 wa lalitali harmonic wavelength chizindikiro), kapangidwe angathe kuthetsa vuto la kusiyana mode EMI.Zotsatira zikuwonetsa kuti kuponderezedwa kwa njira yosiyanitsira EMI ndikwabwino makamaka pamene wosanjikiza wakunja wadzazidwa ndi mkuwa ndipo malo ovala zamkuwa amakhazikika (nthawi iliyonse ya 1 / 20 wavelength).Monga tafotokozera pamwambapa, mkuwa udzayikidwa
Nthawi yotumiza: Jul-29-2020
