Vim qhov me me thiab qhov loj me, yuav luag tsis muaj cov qauv luam tawm Circuit Board uas twb muaj lawm rau kev lag luam IoT loj hlob tuaj. Ua ntej cov qauv no tawm los, peb yuav tsum tau tso siab rau cov kev paub thiab kev tsim khoom uas tau kawm hauv pawg thawj coj hauv theem kev txhim kho thiab xav txog yuav ua li cas siv lawv rau cov kev sib tw tshwj xeeb. Muaj peb qhov chaw uas yuav tsum tau saib xyuas tshwj xeeb. Lawv yog: Circuit Court board cov ntaub ntawv nto, RF / microwave tsim thiab RF kis kab.

Cov khoom siv PCB

"PCB" feem ntau muaj cov laminates, uas tej zaum yuav ua los ntawm fiber ntau epoxy (FR4), polyimide los yog Rogers cov ntaub ntawv los yog lwm yam ntaub ntawv laminate. Cov khoom siv insulating ntawm cov txheej txheem sib txawv yog hu ua prepreg.

cov khoom siv hnav yuav tsum muaj kev ntseeg siab, yog li thaum cov neeg tsim qauv PCB ntsib kev xaiv siv FR4 (cov khoom siv PCB raug nqi tshaj) lossis cov khoom siv siab tshaj thiab kim dua, qhov no yuav dhau los ua teeb meem.

Yog tias daim ntawv thov PCB hnav tau xav tau cov khoom siv ceev ceev, cov khoom siv zaus, FR4 yuav tsis yog qhov kev xaiv zoo tshaj plaws. Lub dielectric qhov tsis tu ncua (Dk) ntawm FR4 yog 4.5, qhov dielectric qhov tsis tu ncua ntawm cov khoom siv ntau tshaj Rogers 4003 series yog 3.55, thiab qhov dielectric tas li ntawm cov kwv tij Rogers 4350 yog 3.66.

"Lub dielectric qhov tsis tu ncua ntawm lub laminate yog hais txog qhov sib piv ntawm lub peev xwm lossis lub zog ntawm ib khub ntawm cov conductors nyob ze ntawm lub laminate mus rau lub peev xwm lossis lub zog ntawm ob khub ntawm cov khoom siv hauv lub tshuab nqus tsev. Ntawm cov frequencies siab, nws yog qhov zoo tshaj kom muaj qhov poob me me. Yog li ntawd, Roger 4350 nrog lub dielectric tas li ntawm 3.66 yog qhov tsim nyog rau kev siv zaus ntau dua li FR4 nrog lub dielectric tas li ntawm 4.5.

Raws li ib txwm muaj, tus naj npawb ntawm PCB txheej rau cov khoom siv coj los siv tau yog li ntawm 4 txog 8 txheej. Lub hauv paus ntsiab lus ntawm kev tsim txheej txheej yog tias nws yog 8-txheej PCB, nws yuav tsum muaj peev xwm muab cov av txaus thiab cov txheej txheem hluav taws xob thiab xaim txheej txheej. Ua li no, cov nyhuv ripple hauv crosstalk tuaj yeem khaws cia rau qhov tsawg kawg nkaus thiab kev cuam tshuam hluav taws xob (EMI) tuaj yeem txo qis.

Nyob rau hauv lub Circuit Court board layout tsim theem, lub layout txoj kev npaj yog feem ntau muab ib tug loj av txheej ze rau lub hwj chim faib txheej. Qhov no tuaj yeem tsim cov nyhuv ripple tsawg heev, thiab lub suab nrov ntawm lub kaw lus kuj tuaj yeem txo qis rau yuav luag xoom. Qhov no tseem ceeb tshwj xeeb tshaj yog rau lub xov tooj cua zaus subsystem.

Piv nrog rau cov khoom siv Rogers, FR4 muaj ntau dua dissipation factor (Df), tshwj xeeb tshaj yog nyob rau hauv high zaus. Rau kev ua tau zoo dua FR4 laminates, tus nqi Df yog kwv yees li 0.002, uas yog qhov kev txiav txim siab zoo dua li FR4 zoo tib yam. Txawm li cas los xij, Rogers pawg tsuas yog 0.001 lossis tsawg dua. Thaum FR4 cov khoom siv rau kev siv ntau zaus, yuav muaj qhov sib txawv tseem ceeb hauv kev poob. Insertion poob yog txhais raws li lub zog poob ntawm lub teeb liab los ntawm point A mus rau point B thaum siv FR4, Rogers los yog lwm yam ntaub ntawv.

tsim teeb meem

Wearable PCB xav tau kev tswj hwm impedance. Qhov no yog ib qho tseem ceeb rau cov khoom siv hnav. Kev sib txuam impedance tuaj yeem tsim cov teeb liab huv dua. Yav dhau los, tus qauv kam rau ua rau cov teeb liab nqa cov cim yog ± 10%. Qhov ntsuas no yog pom tseeb tsis zoo txaus rau niaj hnub no high-frequency thiab high-ceev circuits. Qhov kev xav tau tam sim no yog ± 7%, thiab qee zaum txawm tias ± 5% lossis tsawg dua. Qhov kev ntsuas no thiab lwm yam kev hloov pauv yuav cuam tshuam rau kev tsim cov khoom siv PCBs nrog kev tswj hwm nruj tshwj xeeb, yog li txwv cov lag luam uas tuaj yeem tsim lawv.

Lub dielectric qhov ua siab ntev ntawm lub laminate ua los ntawm Rogers UHF cov ntaub ntawv feem ntau khaws cia ntawm ± 2%, thiab qee cov khoom tuaj yeem ncav cuag ± 1%. Nyob rau hauv sib piv, lub dielectric tas li kam rau ua ntawm FR4 laminate yog siab li 10%. Yog li ntawd, sib piv ob cov ntaub ntawv no tuaj yeem pom tias Rogers 'kev tso quav tsis tshua muaj tshwj xeeb. Piv nrog rau cov khoom siv FR4 ib txwm muaj, qhov kev sib kis tsis zoo thiab qhov poob ntawm Rogers pawg yog ib nrab qis.

Feem ntau, tus nqi yog qhov tseem ceeb tshaj plaws. Txawm li cas los xij, Rogers tuaj yeem muab qhov tsawg-tsawg-tsawg zaus laminate ua haujlwm ntawm tus nqi tsim nyog. Rau kev lag luam kev lag luam, Rogers tuaj yeem ua rau hauv hybrid PCB nrog epoxy-raws li FR4, qee cov txheej uas siv Rogers cov khoom, thiab lwm cov txheej siv FR4.

Thaum xaiv Rogers pawg, zaus yog thawj qhov kev txiav txim siab. Thaum lub zaus ntau tshaj 500MHz, PCB cov neeg tsim qauv nyiam xaiv Rogers cov ntaub ntawv, tshwj xeeb tshaj yog rau RF / microwave circuits, vim tias cov ntaub ntawv no tuaj yeem muab kev ua tau zoo dua thaum cov kab mob sab saud raug tswj nruj heev los ntawm impedance.

Piv nrog rau cov khoom siv FR4, Rogers cov khoom tseem tuaj yeem muab cov dielectric poob qis, thiab nws cov dielectric tsis tu ncua yog ruaj khov nyob rau hauv ntau zaus. Tsis tas li ntawd, cov khoom siv Rogers tuaj yeem muab qhov zoo tshaj plaws uas tsis muaj qhov tsis zoo uas yuav tsum tau ua los ntawm kev ua haujlwm siab.

Cov coefficient ntawm thermal expansion (CTE) ntawm Rogers 4000 series cov ntaub ntawv muaj qhov zoo ntawm qhov ntev. Qhov no txhais tau hais tias piv nrog FR4, thaum lub PCB raug mob khaub thuas, kub thiab kub heev reflow soldering cycles, lub thermal expansion thiab contraction ntawm lub Circuit Court board yuav tsum tau khaws cia nyob rau hauv ib tug ruaj khov txwv nyob rau hauv ntau zaus thiab siab dua kub mus.

Nyob rau hauv cov ntaub ntawv ntawm kev sib xyaw stacking, nws yog ib qho yooj yim los siv cov txheej txheem tsim khoom siv los sib xyaw Rogers thiab kev ua haujlwm siab FR4 ua ke, yog li nws yooj yim heev kom ua tiav cov khoom lag luam siab. Rogers pawg tsis tas yuav muaj kev tshwj xeeb ntawm kev npaj.

Feem ntau FR4 tsis tuaj yeem ua tiav cov khoom siv hluav taws xob muaj txiaj ntsig zoo, tab sis cov khoom siv FR4 muaj kev ntseeg tau zoo, xws li siab dua Tg, tseem tsis tshua muaj nqi, thiab tuaj yeem siv rau ntau yam kev siv, los ntawm kev tsim suab yooj yim mus rau kev siv microwave nyuaj. .

RF / Microwave tsim kev txiav txim siab

Portable thev naus laus zis thiab Bluetooth tau ua txoj hauv kev rau RF/microwave daim ntawv thov hauv cov khoom siv coj los siv. Niaj hnub no qhov ntau zaus tau dhau los ua dynamic. Ob peb xyoos dhau los, ntau zaus (VHF) tau txhais tias yog 2GHz ~ 3GHz. Tab sis tam sim no peb tuaj yeem pom cov ntawv thov ultra-high zaus (UHF) xws li 10GHz txog 25GHz.

Yog li ntawd, rau cov khoom siv PCB, RF ib feem yuav tsum tau ua tib zoo saib xyuas cov teeb meem ntawm kev xaim, thiab cov teeb liab yuav tsum tau muab cais tawm, thiab cov kab uas tsim cov teeb liab zaus yuav tsum tau khaws cia deb ntawm hauv av. Lwm qhov kev txiav txim siab muaj xws li: muab lub lim dej bypass, txaus decoupling capacitors, grounding, thiab tsim cov kab sib kis thiab kab rov qab yuav luag sib npaug.

Bypass lim tuaj yeem cuam tshuam cov nyhuv ripple ntawm lub suab nrov thiab crosstalk. Decoupling capacitors yuav tsum tau muab tso rau ze dua rau cov cuab yeej pins nqa lub zog teeb liab.

High-speed kis tau tus mob thiab cov teeb liab circuits yuav tsum tau ib txheej hauv av yuav tsum tau muab tso rau nruab nrab ntawm lub hwj chim txheej teeb liab kom du lub jitter generated los ntawm lub suab nrov teeb liab. Thaum lub teeb liab siab dua, qhov me me impedance mismatches yuav ua rau tsis muaj kev sib kis thiab txais cov teeb liab, ua rau muaj kev cuam tshuam. Yog li ntawd, tshwj xeeb yuav tsum tau them rau qhov impedance txuam teeb meem cuam tshuam nrog lub xov tooj cua zaus teeb liab, vim hais tias lub xov tooj cua zaus teeb liab muaj kev kub ceev thiab ib tug tshwj xeeb kam rau ua.

RF kis tau tus mob yuav tsum tau tswj impedance thiaj li yuav kis tau RF signals los ntawm ib tug tshwj xeeb IC substrate rau PCB. Cov kab sib kis no tuaj yeem siv rau ntawm txheej txheej, txheej sab saum toj, thiab hauv qab txheej, lossis tuaj yeem tsim hauv nruab nrab txheej.

Cov txheej txheem siv thaum lub sij hawm PCB RF tsim layout yog microstrip kab, floating strip kab, coplanar waveguide los yog hauv av. Cov kab microstrip muaj qhov ntev ntawm cov hlau los yog cov kab nrib pleb thiab tag nrho cov dav hlau hauv av los yog ib feem ntawm lub dav hlau hauv av ncaj qha hauv qab nws. Cov yam ntxwv impedance nyob rau hauv cov qauv microstrip kab ntau yam ntawm 50Ω txog 75Ω.

Floating stripline yog lwm txoj kev ntawm kev xaim thiab suab nrov. Cov kab no muaj kev ruaj khov-dav thaiv ntawm txheej sab hauv thiab lub dav hlau loj hauv av saum toj thiab hauv qab ntawm tus neeg xyuas pib. Lub dav hlau hauv av yog sandwiched ntawm lub dav hlau fais fab, yog li nws tuaj yeem muab cov nyhuv hauv av zoo heev. Qhov no yog txoj kev nyiam tshaj plaws rau kev siv PCB RF teeb liab thaiv.

Coplanar waveguide tuaj yeem muab kev sib cais zoo dua nyob ze ntawm RF Circuit Court thiab Circuit Court uas yuav tsum tau txav ze dua. Qhov nruab nrab no muaj cov neeg xyuas pib hauv nruab nrab thiab cov dav hlau hauv av ntawm ob sab lossis hauv qab. Txoj hauv kev zoo tshaj plaws los xa xov tooj cua zaus yog tshem tawm cov kab strips lossis coplanar waveguides. Ob txoj kev no tuaj yeem muab kev sib cais zoo dua ntawm cov teeb liab thiab RF kab.

Nws raug nquahu kom siv qhov hu ua "ntawm laj kab" ntawm ob sab ntawm coplanar waveguide. Txoj kev no tuaj yeem muab cov kab hauv av vias ntawm txhua lub dav hlau hauv av ntawm qhov chaw neeg xyuas pib. Lub ntsiab kab khiav hauv nruab nrab muaj laj kab ntawm txhua sab, yog li muab ib qho luv luv rau qhov rov qab los rau hauv av hauv qab no. Txoj kev no tuaj yeem txo cov suab nrov cuam tshuam nrog cov nyhuv ripple siab ntawm RF teeb liab. Lub dielectric tas li ntawm 4.5 tseem zoo ib yam li cov khoom siv FR4 ntawm prepreg, thaum lub dielectric tas li ntawm prepreg - los ntawm microstrip, stripline lossis offset stripline - yog li ntawm 3.8 txog 3.9.

Hauv qee cov khoom siv uas siv lub dav hlau hauv av, qhov muag tsis pom kev tuaj yeem siv los txhim kho qhov kev sib txuas ntawm lub hwj chim capacitor thiab muab txoj hauv kev shunt los ntawm cov cuab yeej mus rau hauv av. Txoj kev shunt mus rau hauv av tuaj yeem txo qhov ntev ntawm txoj kev. Qhov no tuaj yeem ua tiav ob lub hom phiaj: koj tsis tsuas yog tsim lub shunt lossis hauv av, tab sis kuj txo qis kev sib kis ntawm cov khoom siv nrog thaj chaw me me, uas yog ib qho tseem ceeb ntawm kev tsim RF.