Yuqori chastotali/mikroto’lqinli radio chastotali signal uzatilganda PCB kontaktlarning zanglashiga olib kelishi, kontaktlarning zanglashiga olib keladigan yo’qolishi va kontaktlarning zanglashiga olib keladigan materiali muqarrar ravishda ma’lum miqdorda issiqlik hosil qiladi. Yo’qotish qanchalik katta bo’lsa, PCB materialidan o’tadigan quvvat shunchalik yuqori bo’ladi va issiqlik hosil bo’ladi. Devrenning ish harorati nominal qiymatdan oshib ketganda, kontaktlarning zanglashiga olib kelishi mumkin. Masalan, PCBlarda yaxshi ma’lum bo’lgan MOT tipik ish parametri maksimal ish haroratidir. Ishlash harorati MOT dan oshib ketganda, PCB sxemasining ishlashi va ishonchliligi tahdid ostida bo’ladi. Elektromagnit modellashtirish va eksperimental o’lchovlarning kombinatsiyasi orqali RF mikroto’lqinli PCBlarning termal xususiyatlarini tushunish yuqori haroratlar tufayli kontaktlarning zanglashiga olib kelishi va ishonchliligining yomonlashishini oldini olishga yordam beradi.

O’chirish materiallarida kiritish yo’qotilishi qanday sodir bo’lishini tushunish yuqori chastotali PCB davrlarining termal ishlashi bilan bog’liq muhim omillarni yaxshiroq ta’riflashga yordam beradi. Ushbu maqola sxemaning termal ko’rsatkichlari bilan bog’liq bo’lgan kelishuvlarni muhokama qilish uchun misol sifatida mikrostripli uzatish liniyasi sxemasini oladi. Ikki tomonlama PCB tuzilishiga ega bo’lgan mikrostripli sxemada yo’qotishlar dielektrik yo’qotish, o’tkazgichning yo’qolishi, radiatsiya yo’qolishi va qochqinning yo’qolishini o’z ichiga oladi. Turli xil yo’qotish komponentlari orasidagi farq katta. Bir nechta istisnolardan tashqari, yuqori chastotali PCB davrlarining oqish yo’qolishi odatda juda past. Ushbu maqolada, qochqinning yo’qotish qiymati juda past bo’lgani uchun, u hozircha e’tiborga olinmaydi.

Radiatsiyani yo’qotish

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.

Radiatsiyani yo’qotish bilan bog’liq elektron materiallarning parametrlari asosan dielektrik o’tkazuvchanlik va PCB materialining qalinligi. O’chirish substrati qanchalik qalinroq bo’lsa, radiatsiya yo’qotilishiga olib kelishi ehtimoli shunchalik katta bo’ladi; PCB materialining er darajasi qanchalik past bo’lsa, kontaktlarning zanglashiga olib keladigan nurlanish yo’qolishi shunchalik katta bo’ladi. Moddiy xususiyatlarni har tomonlama tortish, nozik elektron tagliklardan foydalanish past ir zanjirli materiallardan kelib chiqadigan radiatsiya yo’qotilishini qoplash usuli sifatida ishlatilishi mumkin. O’chirish substratining qalinligi va erning kontaktlarning zanglashiga olib keladigan nurlanish yo’qolishiga ta’siri, chunki u chastotaga bog’liq funktsiyadir. O’chirish substratining qalinligi 20mil dan oshmasa va ish chastotasi 20 gigagertsdan past bo’lsa, kontaktlarning zanglashiga olib keladigan radiatsiya yo’qolishi juda past bo’ladi. Ushbu maqoladagi elektron modellashtirish va o’lchash chastotalarining aksariyati 20 gigagertsdan past bo’lganligi sababli, ushbu maqoladagi muhokama radiatsiya yo’qolishining kontaktlarning zanglashiga olib ta’sirini e’tiborsiz qoldiradi.

20 gigagertsdan past bo’lgan nurlanish yo’qotilishini e’tiborsiz qoldirgandan so’ng, mikrostripli uzatish liniyasi zanjirining kiritish yo’qolishi asosan ikkita qismni o’z ichiga oladi: dielektrik yo’qotish va o’tkazgich yo’qolishi. Ikkalasining nisbati asosan sxema substratining qalinligiga bog’liq. Yupqaroq substratlar uchun o’tkazgichning yo’qolishi asosiy komponent hisoblanadi. Ko’pgina sabablarga ko’ra, odatda o’tkazgichning yo’qolishini aniq taxmin qilish qiyin. Masalan, o’tkazgichning sirt pürüzlülüğü elektromagnit to’lqinlarning uzatish xususiyatlariga katta ta’sir ko’rsatadi. Mis folga sirtining pürüzlülüğü nafaqat mikrotasma zanjirining elektromagnit to’lqin tarqalish konstantasini o’zgartiribgina qolmay, balki kontaktlarning zanglashiga olib keladigan o’tkazgich yo’qotilishini ham oshiradi. Teri ta’siridan kelib chiqqan holda, mis folga pürüzlülüğünün o’tkazgichning yo’qolishiga ta’siri ham chastotaga bog’liq. 1-rasmda mos ravishda 50 milya va 6.6 milya teng bo’lgan turli xil PCB qalinligiga asoslangan 10 ohm mikrotasmali uzatish liniyasi zanjirlarining kiritish yo’qotilishi solishtiriladi.

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.

Sxemaning isitish muammosini hal qilish uchun ideal nozik sxema quyidagi xususiyatlarga ega bo’lishi kerak: sxema materialining past yo’qotish koeffitsienti, silliq mis yupqa yuzasi, past er va yuqori issiqlik o’tkazuvchanligi. Yuqori er o’tkazgich materiali bilan solishtirganda, past er sharoitida olingan bir xil empedansning o’tkazgich kengligi kattaroq bo’lishi mumkin, bu kontaktlarning zanglashiga olib keladigan yo’qotilishini kamaytirish uchun foydalidir. O’chirish issiqlik tarqalishi nuqtai nazaridan, ko’pchilik yuqori chastotali PCB sxemasi tagliklari o’tkazgichlarga nisbatan juda yomon issiqlik o’tkazuvchanligiga ega bo’lsa-da, elektron materiallarning issiqlik o’tkazuvchanligi hali ham juda muhim parametrdir.

O’chirish substratlarining issiqlik o’tkazuvchanligi haqida ko’plab munozaralar oldingi maqolalarda ishlab chiqilgan va ushbu maqolada oldingi maqolalardagi ba’zi natijalar va ma’lumotlar keltirilgan. Masalan, quyidagi tenglama va 3-rasm PCB sxemasi materiallarining termal ishlashi bilan bog’liq omillarni tushunishga yordam beradi. Tenglamada k – issiqlik o’tkazuvchanligi (Vt/m/K), A – maydon, TH – issiqlik manbasining harorati, TC – sovuq manbaning harorati, L – issiqlik manbai va issiqlik manbai orasidagi masofa. sovuq manba.