Thaum lub siab zaus/microwave xov tooj cua zaus teeb liab yog pub rau hauv PCB Circuit Court, qhov poob tshwm sim los ntawm Circuit Court nws tus kheej thiab cov khoom siv hauv Circuit Court yuav inevitably tsim ib qho nqi ntawm cov cua sov. Qhov poob ntau dua, lub zog ntau dua dhau los ntawm cov khoom siv PCB, thiab qhov ntau dua cov cua sov tsim. Thaum qhov ntsuas kub ntawm lub voj voog ua haujlwm tshaj qhov ntsuas tus nqi, lub voj voog yuav ua rau qee qhov teeb meem. Piv txwv li, qhov kev khiav hauj lwm tsis zoo MOT, uas paub zoo hauv PCBs, yog qhov siab tshaj plaws kev khiav hauj lwm kub. Thaum qhov kub ntawm kev khiav hauj lwm tshaj qhov MOT, qhov kev ua tau zoo thiab kev ntseeg siab ntawm PCB Circuit Court yuav raug hem. Los ntawm kev sib xyaw ua ke ntawm cov qauv siv hluav taws xob thiab kev sim ntsuas, kev nkag siab txog cov yam ntxwv thermal ntawm RF microwave PCBs tuaj yeem pab kom tsis txhob muaj kev cuam tshuam ntawm Circuit Court degradation thiab kev ntseeg siab degradation los ntawm qhov kub thiab txias.

Kev nkag siab yuav ua li cas qhov kev puas tsuaj tshwm sim hauv cov khoom siv hauv Circuit Court yuav pab tau zoo dua piav qhia txog qhov tseem ceeb ntsig txog kev ua haujlwm thermal ntawm high-frequency PCB circuits. Kab lus no yuav coj cov microstrip kis kab hluav taws xob los ua piv txwv los tham txog kev lag luam tawm cuam tshuam txog kev ua haujlwm thermal ntawm Circuit Court. Nyob rau hauv ib lub microstrip Circuit Court nrog ob-sided PCB qauv, kev poob muaj xws li dielectric poob, conductor poob, hluav taws xob poob, thiab leakage poob. Qhov sib txawv ntawm qhov sib txawv ntawm cov khoom poob yog qhov loj. Nrog qee qhov kev zam, qhov xau poob ntawm high-frequency PCB circuits feem ntau qis heev. Nyob rau hauv tsab xov xwm no, txij li thaum tus nqi poob qis heev, nws yuav tsis quav ntsej rau lub sijhawm.

Cov hluav taws xob poob

Radiation loss depends on many circuit parameters such as operating frequency, circuit substrate thickness, PCB dielectric constant (relative dielectric constant or εr) and design plan. As far as design schemes are concerned, radiation loss often stems from poor impedance transformation in the circuit or electromagnetic waves in the circuit. The difference in transmission. Circuit impedance transformation area usually includes signal feed-in area, step impedance point, stub and matching network. Reasonable circuit design can realize smooth impedance transformation, thereby reducing the radiation loss of the circuit. Of course, it should be realized that there is the possibility of impedance mismatch leading to radiation loss at any interface of the circuit. From the point of view of operating frequency, usually the higher the frequency, the greater the radiation loss of the circuit.

Cov khoom tsis sib xws ntawm cov khoom siv hluav taws xob ntsig txog hluav taws xob poob yog feem ntau dielectric tas li thiab cov khoom siv PCB thickness. Lub thicker lub Circuit Court substrate, qhov ntau dua qhov ua rau hluav taws xob poob; qhov qis dua εr ntawm cov khoom siv PCB, qhov ntau dua qhov hluav taws xob poob ntawm lub voj voog. Comprehensively hnyav cov yam ntxwv, kev siv ntawm nyias Circuit Court substrates yuav siv tau raws li ib txoj kev los offset lub hluav taws xob poob los ntawm tsawg εr Circuit Court cov ntaub ntawv. Kev cuam tshuam ntawm Circuit Court substrate thickness thiab εr ntawm hluav taws xob hluav taws xob poob yog vim nws yog ib qho kev ua haujlwm ntau zaus. Thaum lub thickness ntawm Circuit Court substrate tsis tshaj 20mil thiab kev khiav hauj lwm zaus yog qis dua 20GHz, qhov hluav taws xob poob ntawm lub Circuit Court yog tsawg heev. Txij li feem ntau ntawm cov qauv hauv Circuit Court thiab ntsuas zaus hauv kab lus no yog qis dua 20GHz, kev sib tham hauv kab lus no yuav tsis quav ntsej txog kev cuam tshuam ntawm hluav taws xob poob ntawm hluav taws xob hluav taws xob.

Tom qab tsis quav ntsej cov hluav taws xob poob qis dua 20GHz, qhov kev tso tawm ntawm microstrip kis kab hluav taws xob feem ntau suav nrog ob ntu: dielectric poob thiab tus neeg xyuas pib poob. Qhov kev faib ua feem ntawm ob feem ntau yog nyob ntawm lub thickness ntawm Circuit Court substrate. Rau thinner substrates, tus neeg xyuas pib poob yog qhov tseem ceeb. Rau ntau qhov laj thawj, feem ntau nyuaj rau kev kwv yees kom raug tus neeg xyuas pib poob. Piv txwv li, qhov roughness ntawm tus neeg xyuas pib muaj kev cuam tshuam loj heev rau cov yam ntxwv ntawm kev sib kis ntawm electromagnetic tsis. Qhov saum npoo roughness ntawm tooj liab ntawv yuav tsis tsuas yog hloov cov electromagnetic yoj propagation tas li ntawm microstrip Circuit Court, tab sis kuj ua rau kom cov neeg xyuas pib poob ntawm Circuit Court. Vim cov nyhuv ntawm daim tawv nqaij, qhov cuam tshuam ntawm tooj liab ntawv ci roughness ntawm tus neeg xyuas pib poob kuj yog nyob ntawm zaus. Daim duab 1 muab piv rau qhov poob ntawm 50 ohm microstrip kis kab hluav taws xob raws li qhov sib txawv PCB thicknesses, uas yog 6.6 mils thiab 10 mils, feem.

The simulation results are obtained using Rogers Corporation’s MWI-2010 microwave impedance calculation software. The MWI-2010 software quotes the analytical equations in the classic papers in the field of microstrip line modeling. The test data in Figure 1 is obtained by the differential length measurement method of a vector network analyzer. It can be seen from Fig. 1 that the simulation results of the total loss curve are basically consistent with the measured results. It can be seen from the figure that the conductor loss of the thinner circuit (the curve on the left corresponds to a thickness of 6.6 mil) is the main component of the total insertion loss. As the circuit thickness increases (the thickness corresponding to the curve on the right is 10mil), the dielectric loss and the conductor loss tend to approach, and the two together constitute the total insertion loss.

The circuit material parameters used in the simulation model and the actual circuit are: dielectric constant 3.66, loss factor 0.0037, and copper conductor surface roughness 2.8 um RMS. When the surface roughness of the copper foil under the same circuit material is reduced, the conductor loss of the 6.6 mil and 10 mil circuits in Figure 1 will be significantly reduced; however, the effect is not obvious for the 20 mil circuit. Figure 2 shows the test results of two circuit materials with different roughness, namely Rogers RO4350B™ standard circuit material with high roughness and Rogers RO4350B LoPro™ circuit material with low roughness.

For thinner substrates, the use of smooth copper foil can significantly reduce the insertion loss. For the 6.6mil substrate, the insertion loss is reduced by 0.3 dB due to the use of smooth copper foil at 20GHz; the 10mil substrate is reduced by 0.22 dB at 20GHz; and the 20mil substrate, the insertion loss is only reduced by 0.11 dB.

This means that when the circuit is fed with a certain amount of RF microwave power, the thinner the circuit will generate more heat. When comprehensively weighing the issue of circuit heating, on the one hand, a thinner circuit generates more heat than a thick circuit at high power levels, but on the other hand, a thinner circuit can obtain more effective heat flow through the heat sink. Keep the temperature relatively low.

Yuav kom daws tau qhov teeb meem cua sov ntawm lub voj voog, qhov zoo tshaj plaws nyias Circuit Court yuav tsum muaj cov yam ntxwv hauv qab no: qhov poob qis ntawm cov khoom siv hauv Circuit Court, du tooj liab nyias nto, qis εr thiab siab thermal conductivity. Piv nrog rau cov khoom siv hauv Circuit Court ntawm siab εr, tus neeg xyuas pib dav ntawm tib lub impedance tau txais nyob rau hauv cov xwm txheej ntawm qis εr tuaj yeem loj dua, uas yog qhov zoo los txo cov neeg xyuas pib poob ntawm Circuit Court. Los ntawm kev xav ntawm Circuit Court kub dissipation, txawm hais tias feem ntau high-frequency PCB Circuit Court substrates muaj cov thermal conductivity tsis zoo rau cov conductors, thermal conductivity ntawm cov khoom siv hluav taws xob tseem yog qhov tseem ceeb heev.

Muaj ntau qhov kev sib tham txog cov thermal conductivity ntawm cov hluav taws xob hluav taws xob hauv hluav taws xob tau piav qhia hauv cov khoom ua ntej, thiab tsab xov xwm no yuav hais txog qee qhov txiaj ntsig thiab cov ntaub ntawv los ntawm cov ntawv dhau los. Piv txwv li, cov kab zauv hauv qab no thiab daim duab 3 yuav pab tau kom nkag siab txog cov yam tseem ceeb uas cuam tshuam txog kev ua haujlwm thermal ntawm PCB cov khoom siv hluav taws xob. Hauv qhov sib npaug, k yog qhov thermal conductivity (W / m / K), A yog thaj tsam, TH yog qhov kub ntawm qhov chaw tshav kub, TC yog qhov kub ntawm qhov txias, thiab L yog qhov kev ncua deb ntawm qhov kub thiab txias. qhov chaw txias.