Nuair a chuirtear an comhartha minicíochta raidió ardmhinicíochta / micreathonn isteach sa PCB ciorcad, is cinnte go nginfidh an caillteanas de bharr an chiorcaid féin agus an ábhair chiorcaid méid áirithe teasa. Is mó an caillteanas, is airde an chumhacht a théann tríd an ábhar PCB, agus is mó an teas a ghintear. Nuair a sháraíonn teocht oibriúcháin an chiorcaid an luach rátáilte, féadfaidh an ciorcad roinnt fadhbanna a chruthú. Mar shampla, is é an paraiméadar oibriúcháin tipiciúil MOT, atá ar eolas go maith i PCBanna, an teocht oibriúcháin uasta. Nuair a sháraíonn an teocht oibriúcháin an MOT, bagairtfear feidhmíocht agus iontaofacht an chiorcaid PCB. Trí theaglaim de shamhaltú leictreamaighnéadach agus tomhais thurgnamhacha, is féidir le tuiscint a fháil ar shaintréithe teirmeacha PCBanna micreathonn RF cuidiú le díghrádú feidhmíochta ciorcad agus díghrádú iontaofachta de bharr teochtaí arda a sheachaint.

Cuidíonn tuiscint ar an gcaoi a dtarlaíonn caillteanas isteach in ábhair chiorcaid le cur síos níos fearr a dhéanamh ar na tosca tábhachtacha a bhaineann le feidhmíocht theirmeach ciorcaid PCB ardmhinicíochta. Tógfaidh an t-alt seo ciorcad na líne tarchuir micreastruchtúir mar shampla chun na comhbhabhtálacha a bhaineann le feidhmíocht theirmeach an chiorcaid a phlé. I gciorcad micreastruchtúr le struchtúr PCB dhá thaobh, cuimsíonn caillteanais caillteanas tréleictreach, caillteanas seoltóra, caillteanas radaíochta, agus caillteanas sceite. Tá an difríocht idir na comhpháirteanna caillteanais éagsúla mór. Le cúpla eisceacht, is gnách go mbíonn caillteanas sceite ciorcaid PCB ardmhinicíochta an-íseal. San Airteagal seo, ós rud é go bhfuil luach an chaillteanais sceite an-íseal, tabharfar neamhaird air de thuras na huaire.

Caillteanas radaíochta

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.

Is iad paraiméadair na n-ábhar ciorcad a bhaineann le caillteanas radaíochta tairiseach tréleictreach agus tiús ábhar PCB den chuid is mó. An tiús an tsubstráit chiorcaid, is mó an fhéidearthacht go gcaillfidh sé radaíocht; is ísle εr an ábhair PCB, is mó an caillteanas radaíochta sa chiorcad. Saintréithe ábhair a mheá go cuimsitheach, is féidir foshraitheanna ciorcad tanaí a úsáid mar bhealach chun an caillteanas radaíochta de bharr ábhair chiorcaid íseal rr a fhritháireamh. Tá tionchar thiús an tsubstráit chiorcaid agus εr ar chaillteanas radaíochta ciorcaid toisc gur feidhm atá ag brath ar mhinicíocht í. Nuair nach sáraíonn tiús an tsubstráit chiorcaid 20mil agus go bhfuil an mhinicíocht oibriúcháin níos ísle ná 20GHz, tá caillteanas radaíochta an chiorcaid an-íseal. Ó tharla go bhfuil an chuid is mó de na minicíochtaí samhaltaithe agus tomhais ciorcaid san alt seo níos ísle ná 20GHz, tabharfaidh an plé san alt seo neamhaird ar thionchar chaillteanas radaíochta ar théamh ciorcad.

Tar éis neamhaird a dhéanamh den chaillteanas radaíochta faoi bhun 20GHz, tá dhá chuid den chuid is mó den chaillteanas isteach ar chiorcad líne tarchuir micreastruchtúir: caillteanas tréleictreach agus caillteanas seoltóra. Braitheann cion na beirte go príomha ar thiús an tsubstráit chiorcaid. Maidir le foshraitheanna níos tanaí, is é caillteanas seoltóra an phríomh-chomhpháirt. Ar go leor cúiseanna, bíonn sé deacair go ginearálta caillteanas seoltóra a thuar go cruinn. Mar shampla, tá tionchar mór ag garbhús dromchla seoltóra ar shaintréithe tarchuir tonnta leictreamaighnéadacha. Ní amháin go n-athróidh garbh dromchla scragall copair tairiseach iomadú tonn leictreamaighnéadach an chiorcaid mhicreastruchtúir, ach méadóidh sé caillteanas seoltóra an chiorcaid freisin. Mar gheall ar éifeacht an chraiceann, tá tionchar garbh na scragall copair ar chaillteanas seoltóra ag brath ar mhinicíocht freisin. Déanann Figiúr 1 comparáid idir an caillteanas isteach de chiorcaid líne tarchuir micreastruip 50 ohm bunaithe ar thiúis éagsúla PCB, arb iad 6.6 mils agus 10 mils, faoi seach.

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.

D’fhonn fadhb téimh an chiorcaid a réiteach, ba cheart go mbeadh na tréithe seo a leanas ag an gciorcad tanaí idéalach: fachtóir caillteanais íseal an ábhair chiorcaid, dromchla tanaí copair mín, íseal εr agus seoltacht ard theirmeach. I gcomparáid leis an ábhar ciorcaid ard εr, is féidir le leithead seoltóra an impedance céanna a fhaightear faoi choinníoll íseal εr a bheith níos mó, rud atá tairbheach chun caillteanas seoltóra an chiorcaid a laghdú. Ó thaobh diomailt teasa ciorcaid de, cé go bhfuil seoltacht theirmeach an-lag ag an gcuid is mó de na foshraitheanna ciorcad PCB ardmhinicíochta i gcoibhneas le seoltóirí, is paraiméadar an-tábhachtach fós seoltacht theirmeach na n-ábhar ciorcad.

Míníodh go leor plé faoi sheoltacht theirmeach foshraitheanna ciorcad in ailt roimhe seo, agus luafaidh an t-alt seo roinnt torthaí agus faisnéise ó ailt níos luaithe. Mar shampla, tá an chothromóid seo a leanas agus Fíor 3 ina gcuidiú chun na tosca a bhaineann le feidhmíocht theirmeach ábhar ciorcad PCB a thuiscint. Sa chothromóid, is é k an seoltacht theirmeach (W / m / K), is é A an t-achar, is é TH teocht na foinse teasa, is é TC teocht na foinse fuar, agus is é L an fad idir an fhoinse teasa agus an foinse fuar.