Thermal Management ntawm High-Power PCBs
Cov neeg tsim qauv ntsib teeb meem nyuaj hauv kev sib ntsib lub zog, uas suav nrog kev tswj xyuas kom zoo, pib nrog PCB tsim.Txhua lub zog hluav taws xob, suav nrog cov ntawv thov RF thiab cov tshuab uas muaj cov teeb liab ceev, tab tom hloov mus rau cov kev daws teeb meem uas muaj kev ua haujlwm nyuaj ntxiv nyob rau hauv puas tau. - qhov chaw me me. Cov neeg tsim qauv ntsib cov teeb meem xav tau ntau ntxiv kom ua tau raws li qhov system loj, qhov hnyav, thiab lub zog xav tau, uas suav nrog kev tswj xyuas thermal zoo, pib nrog kev tsim cov ntawv luam tawm-circuit board.
High-kev sib koom ua ke-ceev cov cuab yeej siv hluav taws xob, xws li cov khoom siv kub thiab yog li yuav tsum tau hloov kho cua sov los yog ua haujlwm kub ua haujlwm, ua haujlwm tau zoo li sai tau. Thermal stress yog ib qho ntawm cov laj thawj tseem ceeb ntawm kev ua haujlwm tsis zoo ntawm cov khoom siv hluav taws xob, vim nws ua rau kev ua haujlwm tsis zoo lossis txawm tias muaj peev xwm ua tsis tau lossis tsis ua haujlwm ntawm lub cev. Kev loj hlob sai ntawm lub zog ceev ntawm cov khoom siv thiab qhov nce mus tas li hauv cov zaus yog cov laj thawj tseem ceeb uas ua rau muaj cua sov ntau dhau ntawm cov khoom siv hluav taws xob. Kev siv ntau zuj zus ntawm cov khoom siv semiconductors nrog txo lub zog poob thiab zoo dua thermal conductivity, xws li cov ntaub ntawv dav-bandgap, tsis nyob hauv nws tus kheej txaus los tshem tawm qhov xav tau rau kev tswj xyuas thermal zoo.
Cov khoom siv hluav taws xob silicon tam sim no ua tiav qhov sib txuas ntawm qhov kub ntawm li 125˚C thiab 200˚C. Txawm li cas los xij, nws yog qhov zoo dua los ua kom lub cuab yeej ua haujlwm qis dua qhov kev txwv no, vim qhov no yuav ua rau muaj kev puas tsuaj sai ntawm tib yam thiab txo qis ntawm nws lub neej seem. Qhov tseeb, nws tau kwv yees tias qhov nce ntawm 20˚C nyob rau hauv kev khiav hauj lwm kub, tshwm sim los ntawm kev tswj thermal tsis zoo, tuaj yeem txo qhov seem ntawm cov khoom seem mus txog 50 feem pua.
Txoj kev layout:
Ib txoj hauv kev rau kev tswj xyuas thermal feem ntau ua raws li hauv ntau txoj haujlwm yog siv cov khoom siv hluav taws xob nrog cov txheej txheem nplaim hluav taws kub 4 (FR-4), cov khoom pheej yig thiab yooj yim ua haujlwm, tsom rau thermal optimization ntawm Circuit Court layout.
Cov kev ntsuas tseem ceeb tau txais kev txhawj xeeb txog kev muab cov khoom siv tooj liab ntxiv, kev siv cov kab uas muaj cov thickness ntau dua, thiab kev tso cua sov los ntawm cov khoom hauv qab cov khoom uas ua kom muaj cua sov ntau tshaj plaws. Cov txheej txheem nruj dua, muaj peev xwm dissipating ntau dua ntawm cov cua sov, suav nrog kev ntxig rau hauv PCB lossis siv rau ntawm cov txheej txheej tooj liab tiag tiag, feem ntau yog nyob rau hauv cov duab ntawm lub npib (li no lub npe "tooj liab npib"). Cov npib tooj liab tau ua tiav nyias thiab tom qab ntawd soldered lossis txuas ncaj qha rau PCB, lossis lawv tuaj yeem muab tso rau hauv cov txheej txheem sab hauv thiab txuas nrog cov txheej txheej sab nraud los ntawm thermal vias. Daim duab 1 qhia txog PCB uas muaj kab noj hniav tshwj xeeb tau ua rau lub tsev ib lub npib tooj liab.
Tooj liab muaj cov thermal conductivity coefficient ntawm 380 W / mK, piv nrog 225 W / mK rau txhuas thiab rau 0.3 W / mK rau FR-4. Tooj liab yog cov hlau uas pheej yig thiab twb tau siv dav hauv kev tsim PCB; yog li ntawd, nws yog qhov kev xaiv zoo tshaj plaws rau kev ua cov npib tooj liab, thermal vias, thiab cov dav hlau hauv av, txhua qhov kev daws teeb meem muaj peev xwm txhim kho cov cua sov.
Kev ua kom zoo ntawm cov khoom ua haujlwm ntawm lub rooj tsavxwm yog qhov tseem ceeb hauv kev tiv thaiv kev tsim ntawm cov chaw kub, yog li xyuas kom meej tias cov cua sov tau muab faib ua qhov sib npaug li sai tau raws li tag nrho pawg thawj coj saib. Hauv qhov no, cov khoom siv hluav taws xob yuav tsum tau muab faib rau hauv tsis muaj kev txiav txim tshwj xeeb nyob ib puag ncig PCB kom tsis txhob tsim cov chaw kub hauv ib cheeb tsam. Txawm li cas los xij, nws yog qhov zoo dua kom tsis txhob tso cov khoom siv hluav taws xob uas tsim kom muaj cua sov nyob ze ntawm cov npoo ntawm lub rooj tsavxwm. Hloov pauv, lawv yuav tsum tau muab tso rau ze li sai tau rau qhov chaw nruab nrab ntawm lub rooj tsavxwm, nyiam qhov sib faib hluav taws xob. Yog tias lub tshuab hluav taws xob muaj hluav taws xob tau teeb tsa nyob ze ntawm ntug ntawm lub rooj tsavxwm, nws yuav tsim kom muaj cua sov ntawm ntug, ua rau qhov kub thiab txias. Yog hais tias, ntawm qhov tod tes, nws muab tso rau ze ntawm qhov chaw ntawm lub rooj tsavxwm, cov cua sov yuav dissipate rau saum npoo nyob rau hauv tag nrho cov lus qhia, txo qhov kub thiab dissipating lub tshav kub yooj yim dua. Cov cuab yeej hluav taws xob yuav tsum tsis txhob muab tso rau ze rau cov khoom rhiab thiab yuav tsum tau muab tso rau ntawm ib leeg.
PCB substrate xaiv:
Vim nws cov thermal conductivity tsawg - nruab nrab ntawm {{0}}.2 thiab 0.5 W/mK - FR-4 feem ntau tsis haum rau cov ntawv thov uas yuav tsum tau ua kom muaj cua sov ntau. Cov cua sov uas tuaj yeem tsim nyob rau hauv high-power circuits yog qhov tseem ceeb, sib xyaw ua ke los ntawm qhov tseeb tias cov tshuab no feem ntau ua haujlwm nyob rau hauv ib puag ncig hnyav thiab kub heev. Kev siv lwm cov khoom siv substrate nrog cov thermal conductivity ntau dua yuav yog qhov kev xaiv zoo dua li kev siv cov tsoos FR -4.
Cov ntaub ntawv ceramic, piv txwv li, muab cov txiaj ntsig tseem ceeb rau kev tswj xyuas thermal ntawm lub zog siab PCBs. Ntxiv nrog rau kev txhim kho thermal conductivity, cov ntaub ntawv no muaj cov khoom siv zoo heev uas pab txhawb kev ntxhov siab thaum rov ua dua thermal cycling. Tsis tas li ntawd, cov ntaub ntawv ceramic muaj qis dielectric poob ua haujlwm ntawm zaus mus txog 10 GHz. Rau ntau zaus, nws yog ib txwm muaj peev xwm xaiv rau hybrid cov ntaub ntawv (xws li PTFE), uas muab sib npaug zos poob nrog ib tug me ntsis txo nyob rau hauv thermal conductivity.
Qhov siab dua qhov thermal conductivity ntawm cov khoom, qhov hloov hluav taws xob sai dua. Nws ua raws li cov hlau xws li txhuas, ntxiv rau qhov sib zog dua li ceramic, muab cov kev daws teeb meem zoo tshaj plaws rau kev hloov cua sov ntawm cov khoom. Aluminium tshwj xeeb yog tus neeg xyuas pib zoo heev, muaj lub zog zoo, rov ua dua tshiab, thiab tsis muaj tshuaj lom. Ua tsaug rau lawv cov thermal conductivity siab, cov hlau txheej pab kom sai sai hloov cov cua sov thoob plaws hauv lub rooj tsavxwm. Qee cov tuam txhab lag luam kuj tseem muaj cov hlau-clad PCBs, nyob rau hauv ob txheej txheej yog hlau-clad, feem ntau yog txhuas los yog galvanized tooj liab. Los ntawm tus nqi-ib-nruab-qhov hnyav ntawm qhov pom, aluminium yog qhov kev xaiv zoo tshaj plaws, thaum tooj liab muaj ntau dua thermal conductivity. Aluminium yog dav siv rau kev tsim kho ntawm PCBs uas txhawb nqa high-power LEDs (ib qho piv txwv yog pom nyob rau hauv daim duab 2), uas nws kuj tseem ceeb heev rau nws lub peev xwm los cuam tshuam lub teeb deb ntawm lub substrate.
Hlau PCBs, tseem hu ua insulating hlau substrates (IMS), tuaj yeem laminated ncaj qha rau hauv PCB, ua rau lub rooj tsavxwm nrog FR-4 substrates thiab hlau core nrog ib txheej thiab ob txheej tshuab nrog kev tswj qhov tob, uas ua haujlwm kom hloov cov cua sov tawm ntawm cov khoom siv hauv lub nkoj thiab mus rau qhov chaw tsis tshua muaj teeb meem. Hauv IMS PCBs, ib txheej nyias ntawm thermally conductive tab sis hluav taws xob insulating dielectric yog laminated ntawm ib lub hauv paus hlau thiab tooj liab ntawv ci. Cov ntawv ci tooj liab yog etched rau hauv cov qauv uas xav tau thiab cov hlau puag absorbs cua sov los ntawm qhov Circuit Court los ntawm nyias dielectric.
Cov txiaj ntsig tseem ceeb muab los ntawm IMS PCBs yog cov hauv qab no:
1. Thaum tshav kub kub dissipation yog siab dua tus qauv FR-4 kev tsim kho.
2. Cov dielectrics feem ntau yog 5 × mus rau 10 × ntau thermally conductive tshaj li qub epoxy iav.
3. Thermal hloov yog exponentially ntau npaum li nyob rau hauv ib tug pa PCB.
4. Dhau li ntawm LED thev naus laus zis (cov cim teeb pom kev zoo, cov lus qhia, thiab teeb pom kev zoo), IMS Circuit Court boards tau siv dav hauv kev lag luam tsheb (lub teeb taub hau, lub cav tswj, thiab lub zog hluav taws xob), hauv hluav taws xob hluav taws xob (DC fais fab mov, inverters, thiab cav tswj) , nyob rau hauv keyboards, thiab nyob rau hauv semiconductor relays.
