Nalika sinyal frekuensi radio frekuensi dhuwur / gelombang mikro dipakani menyang PCB sirkuit, mundhut disebabake sirkuit dhewe lan materi sirkuit mesthi bakal generate jumlah tartamtu saka panas. Sing luwih gedhe mundhut, sing luwih dhuwur daya liwat materi PCB, lan luwih panas kui. Nalika suhu operasi sirkuit ngluwihi nilai dirating, sirkuit bisa nimbulaké sawetara masalah. Contone, MOT parameter operasi khas, kang uga dikenal ing PCBs, suhu operasi maksimum. Nalika suhu operasi ngluwihi MOT, kinerja lan linuwih sirkuit PCB bakal kaancam. Liwat kombinasi modeling elektromagnetik lan pangukuran eksperimen, ngerteni karakteristik termal PCB gelombang mikro RF bisa mbantu ngindhari degradasi kinerja sirkuit lan degradasi linuwih sing disebabake dening suhu dhuwur.

Ngerti carane mundhut selipan ana ing bahan sirkuit mbantu kanggo njlèntrèhaké luwih apik faktor penting related kanggo kinerja termal saka sirkuit PCB frekuensi dhuwur. Artikel iki bakal njupuk sirkuit garis transmisi microstrip minangka conto kanggo ngrembug trade-offs related kanggo kinerja termal saka sirkuit. Ing sirkuit microstrip karo struktur PCB pindho sisi, mundhut kalebu mundhut dielektrik, mundhut konduktor, mundhut radiation, lan mundhut bocor. Bentenipun antarane komponen mundhut beda gedhe. Kanthi sawetara pangecualian, mundhut bocor sirkuit PCB frekuensi dhuwur umume kurang. Ing artikel iki, wiwit nilai mundhut bocor banget kurang, iku bakal digatèkaké kanggo wektu.

mundhut radiasi

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.

Parameter bahan sirkuit sing ana gandhengane karo mundhut radiasi utamane dielektrik konstan lan kekandelan materi PCB. Sing luwih kenthel ing landasan sirkuit, luwih gedhe kemungkinan nyebabake mundhut radiasi; luwih murah εr saka materi PCB, sing luwih mundhut radiation saka sirkuit. Karakteristik materi sing ditimbang kanthi lengkap, panggunaan substrat sirkuit tipis bisa digunakake minangka cara kanggo ngimbangi kerugian radiasi sing disebabake dening bahan sirkuit εr sing kurang. Pengaruh kekandelan substrat sirkuit lan εr ing mundhut radiasi sirkuit amarga iku fungsi gumantung frekuensi. Nalika kekandelan saka landasan sirkuit ora ngluwihi 20mil lan frekuensi operasi luwih murah tinimbang 20GHz, mundhut radiation saka sirkuit banget kurang. Amarga umume modeling sirkuit lan frekuensi pangukuran ing artikel iki luwih murah tinimbang 20GHz, diskusi ing artikel iki bakal nglirwakake pengaruh mundhut radiasi ing pemanasan sirkuit.

Sawise ora nggatekake mundhut radiasi ing ngisor 20GHz, mundhut selipan sirkuit jalur transmisi microstrip utamane kalebu rong bagean: mundhut dielektrik lan mundhut konduktor. Proporsi saka loro utamané gumantung ing kekandelan saka landasan sirkuit. Kanggo substrat sing luwih tipis, mundhut konduktor minangka komponen utama. Amarga akeh alasan, umume angel prédhiksi kerugian konduktor kanthi akurat. Contone, kekasaran permukaan konduktor duweni pengaruh gedhe marang karakteristik transmisi gelombang elektromagnetik. Kekasaran permukaan foil tembaga ora mung ngganti konstanta panyebaran gelombang elektromagnetik saka sirkuit microstrip, nanging uga nambah kerugian konduktor sirkuit. Amarga efek kulit, pengaruh kekasaran foil tembaga ing mundhut konduktor uga gumantung marang frekuensi. Figure 1 mbandhingaké mundhut selipan saka 50 ohm microstrip sirkuit transmisi line adhedhasar kekandelan PCB beda, sing mungguh 6.6 mil lan 10 mil.

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.

Supaya kanggo ngatasi masalah dadi panas saka sirkuit, sirkuit lancip becik kudu duwe ciri ing ngisor iki: faktor mundhut kurang saka materi sirkuit, lumahing lancip tembaga Gamelan, εr kurang lan konduktivitas termal dhuwur. Dibandhingake karo materi sirkuit saka εr dhuwur, jembaré konduktor saka impedansi padha dijupuk ing kondisi εr kurang bisa luwih gedhe, kang ono gunane kanggo ngurangi mundhut konduktor sirkuit. Saka perspektif boros panas sirkuit, sanajan paling landasan sirkuit PCB frekuensi dhuwur duwe konduktivitas termal banget miskin relatif kanggo konduktor, konduktivitas termal bahan sirkuit isih parameter penting banget.

Akeh diskusi babagan konduktivitas termal substrat sirkuit wis dijlentrehake ing artikel sadurunge, lan artikel iki bakal ngutip sawetara asil lan informasi saka artikel sadurunge. Contone, persamaan ing ngisor iki lan Gambar 3 mbiyantu kanggo mangerteni faktor-faktor sing ana gandhengane karo kinerja termal bahan sirkuit PCB. Ing persamaan kasebut, k yaiku konduktivitas termal (W/m/K), A yaiku area, TH yaiku suhu sumber panas, TC yaiku suhu sumber kadhemen, lan L yaiku jarak antarane sumber panas lan sumber kadhemen.