Nalika sinyal frekuensi radio frekuensi luhur / gelombang mikro diasupkeun kana PCB sirkuit, leungitna disababkeun ku sirkuit sorangan jeung bahan sirkuit inevitably bakal ngahasilkeun jumlah nu tangtu panas. Nu leuwih gede leungitna, nu leuwih luhur kakuatan ngaliwatan bahan PCB, jeung gede panas dihasilkeun. Nalika suhu operasi sirkuit ngaleuwihan nilai dipeunteun, sirkuit bisa ngabalukarkeun sababaraha masalah. Contona, parameter operasi has MOT, nu ogé dipikawanoh dina PCBs, suhu operasi maksimum. Nalika suhu operasi ngaleuwihan MOT, kinerja jeung reliabilitas sirkuit PCB bakal kaancam. Ngaliwatan kombinasi modeling éléktromagnétik jeung pangukuran ékspérimén, pamahaman ciri termal tina RF microwave PCBs bisa mantuan nyegah degradasi kinerja circuit sarta degradasi reliabilitas disababkeun ku suhu luhur.

Ngartos kumaha leungitna sisipan lumangsung dina bahan sirkuit mantuan pikeun ngajelaskeun hadé faktor penting patali kinerja termal sirkuit PCB frékuénsi luhur. Artikel ieu bakal nyandak sirkuit jalur transmisi microstrip salaku conto pikeun ngabahas trade-offs patali kinerja termal tina sirkuit. Dina sirkuit microstrip kalawan struktur PCB dua sisi, karugian kaasup leungitna diéléktrik, leungitna konduktor, leungitna radiasi, sarta leungitna leakage. Beda antara komponén leungitna béda téh badag. Kalawan sababaraha iwal, leungitna leakage sirkuit PCB frékuénsi luhur umumna pisan low. Dina artikel ieu, saprak nilai leungitna leakage pisan low, éta bakal dipaliré saheulaanan.

Kaleungitan 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 patali leungitna radiasi utamana diéléktrik konstanta sarta ketebalan bahan PCB. The kandel substrat circuit, nu gede kamungkinan ngabalukarkeun leungitna radiasi; nu handap εr tina bahan PCB, nu gede leungitna radiasi sirkuit. Komprehensif timbangan ciri bahan, pamakéan substrat circuit ipis bisa dipaké salaku cara pikeun offset leungitna radiasi disababkeun ku bahan circuit εr low. Pangaruh ketebalan substrat sirkuit sareng εr kana leungitna radiasi sirkuit kusabab fungsina gumantung kana frékuénsi. Nalika ketebalan substrat circuit teu ngaleuwihan 20mil jeung frékuénsi operasi leuwih handap 20GHz, leungitna radiasi sirkuit pisan low. Kusabab sabagéan ageung modél sirkuit sareng frékuénsi pangukuran dina tulisan ieu langkung handap tina 20GHz, diskusi dina tulisan ieu bakal malire pangaruh leungitna radiasi dina pemanasan sirkuit.

Saatos teu malire leungitna radiasi handap 20GHz, leungitna sisipan sirkuit jalur transmisi microstrip utamana ngawengku dua bagian: leungitna diéléktrik jeung leungitna konduktor. Proporsi dua utamana gumantung kana ketebalan substrat circuit. Pikeun substrat thinner, leungitna konduktor mangrupakeun komponén utama. Pikeun seueur alesan, umumna hésé pikeun ngaduga kaleungitan konduktor sacara akurat. Contona, roughness permukaan konduktor boga pangaruh badag dina ciri transmisi gelombang éléktromagnétik. Kakasaran permukaan foil tambaga henteu ngan ukur ngarobih konstanta rambatan gelombang éléktromagnétik tina sirkuit microstrip, tapi ogé ningkatkeun leungitna konduktor sirkuit. Kusabab pangaruh kulit, pangaruh kakasaran foil tambaga dina leungitna konduktor ogé gumantung kana frékuénsi. angka 1 compares leungitna sisipan 50 ohm microstrip jalur transmisi sirkuit dumasar kana ketebalan PCB béda, nu 6.6 mils na 10 mils, mungguh.

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.

Pikeun ngabéréskeun masalah pemanasan sirkuit, sirkuit ipis idéal kedah gaduh ciri-ciri ieu: faktor leungitna bahan sirkuit, permukaan ipis tambaga lemes, εr rendah sareng konduktivitas termal anu luhur. Dibandingkeun sareng bahan sirkuit εr anu luhur, lebar konduktor tina impedansi anu sami anu dicandak dina kaayaan εr rendah tiasa langkung ageung, anu mangpaat pikeun ngirangan leungitna konduktor sirkuit. Tina sudut pandang dissipation panas sirkuit, sanajan lolobana substrat sirkuit PCB frékuénsi luhur boga konduktivitas termal pisan goréng relatif ka konduktor, konduktivitas termal bahan circuit masih parameter pohara penting.

Loba diskusi ngeunaan konduktivitas termal substrat circuit geus elaborated dina artikel saméméhna, jeung artikel ieu bakal cutatan sababaraha hasil jeung informasi ti artikel saméméhna. Salaku conto, persamaan di handap ieu sareng Gambar 3 ngabantosan ngartos faktor anu aya hubunganana sareng kinerja termal bahan sirkuit PCB. Dina persamaan, k nyaéta konduktivitas termal (W/m/K), A nyaéta wewengkon, TH nyaéta suhu sumber panas, TC nyaéta suhu sumber tiis, sarta L nyaéta jarak antara sumber panas jeung sumber tiis.