With the increasing speed of PCB Ukutshintsha kwemiqondiso, abaqulunqi bePCB banamhlanje kufuneka baqonde kwaye balawule ukungangqinelani komkhondo wePCB. Ngokuhambelana namaxesha amafutshane okuhambisa umqondiso kunye namaxabiso aphezulu eesekethe zale mihla, imikhondo yePCB ayisasebenzi kunxibelelwano olulula, kodwa yimigca yokuhambisa.

Ulawula njani i-impedance ye-PCB

Ukuziqhelanisa, kufuneka ulawule umkhondo we-impedance xa isantya esisezantsi sedijithali sidlula kwi-1ns okanye i-analog frequency ingaphezulu kwe-300Mhz. Enye yeeparameter eziphambili zokulandela umkhondo we-PCB kukungqubana kweempawu zayo (umyinge wevolthi ukuya kwangoku njengoko iliza lihamba ecaleni komgca wokuhambisa isiginali). The characteristic impedance of wire on printed circuit board is an important index of circuit board design, especially in PCB design of high frequency circuit, it must be considered whether the characteristic impedance of wire is consistent with the characteristic impedance required by device or signal. This involves two concepts: impedance control and impedance matching. This paper focuses on impedance control and lamination design.

Ulawulo lokungenelela

Ukulawulwa kwe-EImpedance, umqhubi kwibhodi yesekethe uya kuba nazo zonke iintlobo zokudluliselwa kwesiginali, ukuze kuphuculwe izinga lokuhambisa kwaye kufuneka kwandise ukuhamba kwayo, ukuba umgca ngokwawo ngenxa yokudinwa, ubukhulu be-stacking, ububanzi bocingo kunye nezinye izinto ezahlukeneyo, ziya kubangela Ukutshintsha kwexabiso le-impedance, ukugqwetha umqondiso. Ke ngoko, ixabiso le-impedance yomqhubi kwibhodi yesekethe ehamba ngesantya esiphezulu kufuneka ilawulwe ngaphakathi kuluhlu oluthile, olubizwa ngokuba yi “impedance control”.

The impedance of a PCB trace will be determined by its inductive and capacitive inductance, resistance, and conductivity coefficient. Izinto eziphambili ezichaphazela ukungavisisani kwe-PCB ye-wiring zezi: ububanzi bocingo lobhedu, ubukhulu becala lobhedu, i-dielectric engagungqiyo phakathi, ubukhulu be-medium, ubukhulu bephedi, indlela yocingo lomhlaba, i-wiring ejikeleze iintambo njl. Uluhlu lwe-PCB lwe-impedance ukusuka kwi-25 ukuya kwi-120 ohm.

Ukuziqhelanisa, umgca wokudluliselwa kwe-PCB uhlala uqukethe umkhondo, enye okanye ngaphezulu, kunye nezinto zokugquma. Imikhondo kunye namanqanaba enza i-impedance yolawulo. Ii-PCBS zihlala zihlala zinemigangatho emininzi, kwaye ulawulo lothintelo lunokwakhiwa ngeendlela ezahlukeneyo. However, whatever method is used, the impedance value will be determined by its physical structure and the electrical properties of the insulating material:

Width and thickness of signal trace

The height of the core or prefill material on either side of the trace

Uqwalaselo lomkhondo kunye nembasa

Insulation constants of core and prefilled materials

Imigca yokudlulisa i-PCB iza ngeendlela ezimbini eziphambili: iMicrostrip kunye neStripline.

Microstrip:

Umgca we-microstrip ngumqhubi womcu kunye nenqwelomoya yereferensi kwicala elinye kuphela, kunye nomphezulu kunye namacala abhencekile emoyeni (okanye agalelwe), ngaphezulu komphezulu wokugquma ibhodi yesekethe ye-Er, ngombane okanye isiseko njengesalathiso. Njengoko kubonisiwe ngezantsi:

Qaphela: Kwimveliso yePCB yokwenyani, umenzi webhodi uhlala egqume umphezulu wePCB ngothotho lweoyile eluhlaza, ke ngoko ekubaleni kwe-impedance, imodeli eboniswe ngezantsi ihlala isetyenziselwa ukubala komgca we-microstrip:

Umgca:

Umgca weribhoni yiribhoni yocingo ebekwe phakathi kweenqwelomoya ezimbini, njengoko kubonisiwe kulo mzobo ungezantsi. Ukuqina kwe-dielectric ye-dielectric emelwe yi-H1 kunye ne-H2 inokwahluka.

The above two examples are only a typical demonstration of microstrip lines and ribbon lines. There are many kinds of specific microstrip lines and ribbon lines, such as coated microstrip lines, which are related to the specific laminated structure of PCB.

The equations used to calculate the characteristic impedances require complex mathematical calculations, usually using field solving methods, including boundary element analysis, so using the specialized impedance calculation software SI9000, all we need to do is control the parameters of the characteristic impedances:

I-dielectric rhoqo Er, ububanzi bocingo lwe-W1, i-W2 (i-trapezoid), ubukhulu be-wiring T kunye nobunzima bokugquma H.

W1, W2:

The calculated value must be within the red box. Kwaye njalo.

I-SI9000 isetyenziselwa ukubala ukuba iimfuno zolawulo lwe-impedance ziyahlangatyezwa:

Kuqala ukubala ukulawulwa kokuphela kwesiphelo kwendlela yedatha yeDDR:

TOP layer: 0.5oz copper thickness, 5MIL wire width, 3.8mil distance from the reference plane, dielectric constant 4.2. Khetha imodeli, endaweni yeeparameter, kwaye ukhethe ukubala okungasasebenziyo, njengoko kubonisiwe kumzobo:

I-CoaTIng ithetha i-coaTIng, kwaye ukuba akukho coaTIng, gcwalisa u-0 kubukhulu kunye no-1 kwidayelectric (i-dielectric rhoqo) (umoya).

I-substrate imele umaleko we-substrate, oko kukuthi, umaleko we-dielectric, ngokubanzi usebenzisa i-fr-4, ubukhulu obubalwe yisoftware yokubala ye-impedance, i-dielectric rhoqo ye-4.2 (frequency engaphantsi kwe-1GHz).

Click on Weight (oz) to set the thickness of the copper layer, which determines the thickness of the cable.

9. Ingcamango ye-Prepreg / ye-Core yomaleko wokugquma:

PP (Prepreg) luhlobo lwezixhobo ze-dielectric, ezenziwe ngefayili yeglasi kunye ne-epoxy resin. I-Core inyani i-TYPE ye-PP ephakathi, kodwa amacala ayo amabini agqunywe ngefoyile yobhedu, ngelixa i-PP ingekho. Xa kusenziwa iibhodi ze-multilayer, isiseko kunye ne-PP zihlala zisetyenziswa kunye, kwaye i-PP isetyenziselwa ukudibanisa phakathi kwentloko kunye nomongo.

10. Imiba efuna ingqalelo kuyilo lamination PCB

(1) Ingxaki yephepha lemfazwe

Uyilo maleko PCB kufuneka macala, oko kukuthi, Ebubanzini umaleko eliphakathi kunye ubhedu maleko maleko nganye kufuneka macala. Thatha iileya ezintandathu umzekelo, ubukhulu be-top-GND kunye ne-low-power medium kufuneka ihambelane nobungqingili bobhedu, KUNYE ne-GND-L2 kunye ne-L3-AMANDLA aphakathi kufuneka ahambelane nobunzima bobhedu. Oku akuyi kulunga xa kulaminishwa.

(2) Umaleko wophawu kufuneka uqiniswe ngokudityaniswa nenqwelo moya ekubhekiswa kuyo (oko kukuthi, ubukhulu obuphakathi phakathi komaleko wesiginali kunye nocingo olufutshane lobhedu kufuneka lubencinci kakhulu); Ukunxiba ubhedu olunamandla kunye nokunxiba ubhedu emhlabeni kufuneka kuhlanganiswe ngokuqinileyo.

(3) Kwimeko yesantya esiphezulu kakhulu, kungongezwa amacandelo ongezelelweyo ukwahlula umaleko womqondiso, kodwa kuyacetyiswa ukuba ungawahlukanisi amandla ombane, anokubangela ukuphazamiseka kwengxolo ngokungeyomfuneko.

(4) Ukuhanjiswa kocwecwe loyilo oluhleliweyo kubonisiwe kule theyibhile ilandelayo:

(5) Imigaqo ngokubanzi yolungiselelo lomaleko:

Apha ngezantsi komphezulu wecandelo (umaleko wesibini) yiplanethi yomhlaba, ebonelela ngesixhobo sokukhusela isixhobo kunye nenqwelomoya yesalathiso kwintambo ephezulu;

Zonke iileya zomqondiso zikufuphi nenqwelomoya yomhlaba kangangoko kunokwenzeka.

Kuphephe ukusondelelana ngokuthe ngqo phakathi kweendlela ezimbini zomqondiso kangangoko kunokwenzeka;

Unikezelo lwamandla oluphambili kufuneka lube kufutshane kangangoko kunokwenzeka;

I-symmetry yesakhiwo se-laminate ithathwa.

For the layer layout of the motherboard, it is difficult for the existing motherboard to control the parallel long-distance wiring, and the working frequency of the board level is above 50MHZ

(Ngeemeko ezingaphantsi kwe-50MHZ, nceda ubhekise kuyo kwaye uyiphumze ngokufanelekileyo), umgaqo wobeko uyacetyiswa:

Umphezulu wecandelo kunye nomphezulu wokuwelda zizinto zomhlaba ogcweleyo (ikhaka);

Akukho maleko we-wiring uhambelanayo

Zonke iileya zomqondiso zikufuphi nenqwelomoya yomhlaba kangangoko kunokwenzeka.

Umqondiso ophambili ukufutshane nokwakheka kwaye awuweleli indawo yokwahlulahlula.