Chifukwa chakuchepa kwake komanso kukula kwake, palibenso milingo yosindikizidwa yapamsika wa IoT womwe ukukulirakulira. Miyezo iyi isanatuluke, tidayenera kudalira chidziwitso ndi luso lopanga zomwe taphunzira pakukula kwamagulu a board ndikuganizira momwe tingawagwiritsire ntchito pamavuto omwe akubwera. Pali mbali zitatu zomwe zimafunikira chisamaliro chathu chapadera. Ndi: zida za boardboard pamwamba, kapangidwe ka RF/microwave ndi mizere yotumizira ma RF.

Zithunzi za PCB

"PCB" nthawi zambiri imakhala ndi laminates, omwe amatha kupangidwa ndi fiber-reinforced epoxy (FR4), polyimide kapena Rogers zipangizo kapena zipangizo zina. Zida zotetezera pakati pa zigawo zosiyana zimatchedwa prepreg.

zipangizo kuvala amafuna kudalirika mkulu, kotero pamene PCB okonza akukumana ndi kusankha kugwiritsa ntchito FR4 (zotsika mtengo kwambiri PCB kupanga zinthu) kapena zipangizo zapamwamba ndi zodula, izi zidzakhala vuto.

Ngati mapulogalamu a PCB ovala amafunikira zida zothamanga kwambiri, zothamanga kwambiri, FR4 singakhale chisankho chabwino kwambiri. Dielectric constant (Dk) ya FR4 ndi 4.5, dielectric constant of advanced Rogers 4003 series material is 3.55, and dielectric constant of the brother series Rogers 4350 ndi 3.66.

"Dielectric constant ya laminate imatanthawuza chiŵerengero cha capacitance kapena mphamvu pakati pa makondakitala pafupi ndi laminate ndi capacitance kapena mphamvu pakati pa awiri a kondakitala mu vacuum. Pamaulendo apamwamba, ndi bwino kukhala ndi kutaya pang'ono. Chifukwa chake, Roger 4350 yokhala ndi dielectric constant ya 3.66 ndiyoyenera kugwiritsa ntchito pafupipafupi kuposa FR4 yokhala ndi dielectric constant ya 4.5.

Nthawi zonse, chiwerengero cha zigawo za PCB pazida zovala zimayambira pa 4 mpaka 8. Mfundo yomanga wosanjikiza ndi yakuti ngati ili ndi PCB ya 8-wosanjikiza, iyenera kupereka malo okwanira ndi zigawo za mphamvu ndi sangweji ya waya wosanjikiza. Mwanjira iyi, mphamvu ya ripple mu crosstalk imatha kuchepetsedwa ndipo kusokoneza kwamagetsi (EMI) kumatha kuchepetsedwa kwambiri.

Mu gawo la mapangidwe a board board, dongosolo la masanjidwe nthawi zambiri limayika gawo lalikulu la pansi pafupi ndi gawo logawa mphamvu. Izi zitha kupanga phokoso lotsika kwambiri, ndipo phokoso la dongosolo limathanso kuchepetsedwa mpaka pafupifupi ziro. Izi ndizofunikira makamaka pamayendedwe a wailesi.

Poyerekeza ndi zinthu za Rogers, FR4 ili ndi gawo lalikulu la dissipation factor (Df), makamaka pafupipafupi. Pamawonekedwe apamwamba a FR4 laminates, mtengo wa Df ndi pafupifupi 0.002, womwe ndi dongosolo la kukula bwino kuposa FR4 wamba. Komabe, kuchuluka kwa Rogers ndi 0.001 kapena kuchepera. Zinthu za FR4 zikagwiritsidwa ntchito pafupipafupi kwambiri, padzakhala kusiyana kwakukulu pakutayika koyika. Kutayika kwa kulowetsa kumatanthauzidwa ngati kutaya mphamvu kwa chizindikiro kuchokera kumalo A kupita kumalo B pamene mukugwiritsa ntchito FR4, Rogers kapena zipangizo zina.

kulenga mavuto

PCB yovala imafunikira kuwongolera kolimba. Ichi ndi chinthu chofunikira pazida zovala. Kufananiza kwa Impedans kumatha kubweretsa kufalitsa koyera. M'mbuyomu, kulolerana kwanthawi zonse kwa zizindikiro zonyamula zizindikiro kunali ± 10%. Chizindikirochi mwachiwonekere sichili chokwanira kwa maulendo amasiku ano othamanga kwambiri komanso othamanga kwambiri. Zofunikira pano ndi ± 7%, ndipo nthawi zina ngakhale ± 5% kapena kuchepera. Izi ndi zosintha zina zidzakhudza kwambiri kupanga ma PCB ovalawa omwe ali ndi mphamvu zoletsa, potero kuchepetsa kuchuluka kwa mabizinesi omwe angawapange.

Kulekerera kwa dielectric kosalekeza kwa laminate yopangidwa ndi zida za Rogers UHF nthawi zambiri kumasungidwa pa ± 2%, ndipo zinthu zina zimatha kufikira ± 1%. Mosiyana ndi izi, kulekerera kwa dielectric kosalekeza kwa laminate ya FR4 ndikokwera mpaka 10%. Choncho, yerekezerani Zida ziwirizi zingapezeke kuti kutayika kwa Rogers kumakhala kochepa kwambiri. Poyerekeza ndi zida zachikhalidwe za FR4, kutayika kwapatsiku ndi kutayika kwa stack ya Rogers ndizotsika theka.

Nthawi zambiri, mtengo ndi wofunikira kwambiri. Komabe, Rogers atha kupereka kutsika kochepa kwambiri kwa laminate pamtengo wovomerezeka. Pazamalonda, ma Rogers amatha kupangidwa kukhala PCB yosakanizidwa yokhala ndi epoxy-based FR4, zigawo zina zomwe zimagwiritsa ntchito Rogers, ndi zigawo zina zimagwiritsa ntchito FR4.

Posankha stack ya Rogers, pafupipafupi ndiye chinthu chofunikira kwambiri. Mafupipafupi akapitilira 500MHz, opanga ma PCB amakonda kusankha zida za Rogers, makamaka mabwalo a RF/microwave, chifukwa zidazi zimatha kupereka magwiridwe antchito apamwamba pomwe kumtunda kumayendetsedwa mosamalitsa ndi kusokoneza.

Poyerekeza ndi zinthu za FR4, zinthu za Rogers zimathanso kupereka kuchepa kwa dielectric, ndipo dielectric yake imakhala yokhazikika pama frequency osiyanasiyana. Kuphatikiza apo, zinthu za Rogers zitha kupereka magwiridwe antchito otsika otsika omwe amafunikira ndi magwiridwe antchito apamwamba.

Coefficient of thermal expansion (CTE) ya zida za Rogers 4000 zili ndi kukhazikika kwabwino kwambiri. Izi zikutanthauza kuti poyerekeza ndi FR4, pamene PCB imadutsa maulendo ozizira, otentha komanso otentha kwambiri, kuwonjezereka kwa kutentha ndi kutsika kwa bolodi la dera kumatha kusungidwa pamlingo wokhazikika pansi pa maulendo apamwamba komanso kutentha kwapamwamba.

Pankhani ya ma stacking osakanikirana, ndizosavuta kugwiritsa ntchito ukadaulo wamba wopangira kupanga kusakaniza Rogers ndi FR4 yogwira ntchito kwambiri palimodzi, kotero ndizosavuta kukwaniritsa zokolola zambiri. The Rogers stack safuna wapadera kudzera njira kukonzekera.

Common FR4 sichitha kugwira ntchito zamagetsi zodalirika, koma zida zogwira ntchito kwambiri za FR4 zimakhala ndi mawonekedwe odalirika, monga Tg apamwamba, akadali otsika mtengo, ndipo angagwiritsidwe ntchito m'mapulogalamu osiyanasiyana, kuyambira pamapangidwe osavuta omvera mpaka ma Complex microwave applications. .

RF/Microwave kapangidwe kake

Ukadaulo wam'manja ndi Bluetooth zatsegula njira yogwiritsira ntchito RF/microwave pazida zomveka. Masiku ano ma frequency osiyanasiyana akukhala amphamvu kwambiri. Zaka zingapo zapitazo, ma frequency apamwamba kwambiri (VHF) amatanthauzidwa kuti 2GHz ~ 3GHz. Koma tsopano titha kuwona mapulogalamu apamwamba kwambiri (UHF) kuyambira 10GHz mpaka 25GHz.

Chifukwa chake, kwa PCB yovala, gawo la RF limafunikira chidwi kwambiri pazovuta zamawaya, ndipo ma siginecha ayenera kulekanitsidwa padera, ndipo zowunikira zomwe zimapanga ma siginecha apamwamba ziyenera kusungidwa kutali ndi pansi. Zolinga zina ndi izi: kupereka zosefera zodutsa, ma capacitor okwanira, kuyika pansi, ndi kupanga chingwe chotumizira ndi chingwe chobwerera kuti chikhale chofanana.

Zosefera za Bypass zitha kupondereza mayendedwe a phokoso ndi crosstalk. Decoupling capacitors ayenera kuikidwa pafupi ndi zikhomo za chipangizo zonyamula zizindikiro za mphamvu.

Mizere yothamanga kwambiri komanso maulendo azizindikiro amafunikira malo oti akhazikike pakati pa ma sign amphamvu kuti azitha kusalaza jitter yopangidwa ndi zizindikiro zaphokoso. Pa liwiro lapamwamba la ma siginecha, kusagwirizana pang'ono kwa impedance kumayambitsa kufalikira kosagwirizana ndi kulandira ma siginecha, zomwe zimapangitsa kupotoza. Chifukwa chake, chidwi chapadera chiyenera kuperekedwa ku vuto lofananira ndi impedance yokhudzana ndi ma frequency a radio, chifukwa ma frequency a wailesi ali ndi liwiro lalikulu komanso kulolerana kwapadera.

Mizere yotumizira ma RF imafuna kutsekeka koyendetsedwa kuti itumize ma siginecha a RF kuchokera pagawo linalake la IC kupita ku PCB. Mizere yopatsirayi imatha kukhazikitsidwa pamtunda wakunja, pamwamba, ndi pansi, kapena kupangidwira pakati.

Njira zomwe zimagwiritsidwa ntchito pamapangidwe a PCB RF ndi mzere wa microstrip, mzere woyandama, coplanar waveguide kapena maziko. Mzere wa microstrip uli ndi kutalika kokhazikika kwazitsulo kapena zotsatizana ndi ndege yonse yapansi kapena gawo la ndege pansi pamunsi pake. Kulepheretsa kwamtundu wamtundu wa microstrip kumayambira 50Ω mpaka 75Ω.

Mzere woyandama woyandama ndi njira inanso yolumikizira mawaya ndi kupondereza phokoso. Mzerewu uli ndi mawaya osasunthika m'lifupi mwake pamtunda wamkati ndi ndege yaikulu yapansi pamwamba ndi pansi pa woyendetsa pakati. Ndege yapansi imayikidwa pakati pa ndege yamagetsi, kotero imatha kupereka zotsatira zogwira mtima kwambiri. Iyi ndiye njira yomwe imakonda kuvala ma waya amtundu wa PCB RF.

Coplanar waveguide imatha kupereka kudzipatula kwabwinoko pafupi ndi dera la RF ndi dera lomwe likufunika kuyenderera pafupi. Sing'anga iyi imakhala ndi kondakita wapakati ndi ndege zapansi mbali zonse kapena pansi. Njira yabwino yotumizira ma siginecha a wailesi ndikuyimitsa mizere kapena ma coplanar waveguide. Njira ziwirizi zitha kupereka kudzipatula kwabwino pakati pa ma siginecha ndi ma RF.

Ndibwino kugwiritsa ntchito zomwe zimatchedwa "kudzera mpanda" kumbali zonse za coplanar waveguide. Njira imeneyi angapereke mzere wa vias pansi pa aliyense zitsulo pansi ndege wa kondakitala pakati. Njira yayikulu yomwe ikuyenda pakati imakhala ndi mipanda kumbali iliyonse, motero imapereka njira yachidule yobwereranso pansi. Njirayi imatha kuchepetsa kuchuluka kwaphokoso komwe kumalumikizidwa ndi kutulutsa kwamphamvu kwa siginecha ya RF. Dielectric constant ya 4.5 imakhalabe yofanana ndi FR4 zinthu za prepreg, pomwe dielectric constant ya prepreg-kuchokera ku microstrip, stripline kapena offset stripline-ndi pafupi 3.8 mpaka 3.9.

Pazida zina zomwe zimagwiritsa ntchito ndege yapansi, ma vias akhungu angagwiritsidwe ntchito kuwongolera magwiridwe antchito a capacitor yamagetsi ndikupereka njira ya shunt kuchokera ku chipangizocho kupita pansi. The shunt njira pansi akhoza kufupikitsa kutalika kwa via. Izi zitha kukwaniritsa zolinga ziwiri: simumangopanga shunt kapena nthaka, komanso muchepetse mtunda wotumizira zida zomwe zili ndi madera ang'onoang'ono, zomwe ndizofunikira kwambiri pakupanga kwa RF.