With the increasing speed of PCB iyipada ifihan agbara, awọn apẹẹrẹ PCB oni nilo lati ni oye ati ṣakoso ikọjujasi ti awọn ipasẹ PCB. Ni ibamu si awọn akoko gbigbe ifihan ifihan kukuru ati awọn oṣuwọn aago ti o ga julọ ti awọn iyika oni -nọmba oni -nọmba, awọn ami PCB kii ṣe awọn asopọ ti o rọrun mọ, ṣugbọn awọn laini gbigbe.

Bii o ṣe le ṣakoso ikọlu PCB

Ni iṣe, o jẹ dandan lati ṣakoso ikọlu kakiri nigbati iyara ala -nọmba oni nọmba ti kọja 1ns tabi igbohunsafẹfẹ analog kọja 300Mhz. Ọkan ninu awọn ipilẹ bọtini ti kakiri PCB jẹ ikọlu abuda rẹ (ipin ti foliteji si lọwọlọwọ bi igbi ti nrin lẹgbẹ laini gbigbe ifihan). 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.

Iṣakoso ikọjujasi

Ṣiṣakoso EImpedance, adaorin ninu igbimọ Circuit yoo ni gbogbo iru gbigbe ifihan, lati le mu iwọn gbigbe pọ si ati pe o gbọdọ pọsi igbohunsafẹfẹ rẹ, ti laini funrararẹ nitori etching, sisanra tito, iwọn okun waya ati awọn ifosiwewe oriṣiriṣi miiran, yoo fa iyipada iye ikọjujasi, iparun ifihan. Nitorinaa, iye ikọja ti adaorin lori igbimọ Circuit giga yẹ ki o ṣakoso laarin sakani kan, ti a mọ ni “iṣakoso ikọlu”.

The impedance of a PCB trace will be determined by its inductive and capacitive inductance, resistance, and conductivity coefficient. Awọn ifosiwewe akọkọ ti o ni ipa ikọlu ti wiwọ PCB ni: iwọn ti okun waya idẹ, sisanra ti okun waya, ibakan aisi -itanna ti alabọde, sisanra ti alabọde, sisanra ti paadi, ọna ti okun waya ilẹ, wiwirin ni ayika okun , abbl. Idena PCB awọn sakani lati 25 si 120 ohm.

Ni iṣe, laini gbigbe PCB nigbagbogbo jẹ ti kakiri, ọkan tabi diẹ sii awọn fẹlẹfẹlẹ itọkasi, ati awọn ohun elo idabobo. Awọn kakiri ati awọn fẹlẹfẹlẹ ṣe agbekalẹ ikọlu iṣakoso. PCBS nigbagbogbo yoo jẹ ọpọlọpọ-fẹlẹfẹlẹ, ati ikọlu iṣakoso le ṣee ṣe ni awọn ọna oriṣiriṣi. However, whatever method is used, the impedance value will be determined by its physical structure and the electrical properties of the insulating material:

Iwọn ati sisanra ti kakiri ifihan

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

Iṣeto ni ti kakiri ati awo

Insulation constants of core and prefilled materials

Awọn laini gbigbe PCB wa ni awọn ọna akọkọ meji: Microstrip ati Stripline.

Microstrip:

Laini microstrip jẹ adaorin rinhoho pẹlu ọkọ ofurufu itọkasi ni ẹgbẹ kan nikan, pẹlu oke ati awọn ẹgbẹ ti o han si afẹfẹ (tabi ti a bo), loke dada ti igbimọ Circuit Er nigbagbogbo, pẹlu ipese agbara tabi ilẹ bi itọkasi. Bi a ṣe han ni isalẹ:

Akiyesi: Ni iṣelọpọ PCB gangan, olupese igbimọ nigbagbogbo n bo oju ti PCB pẹlu fẹlẹfẹlẹ ti epo alawọ ewe, nitorinaa ni iṣiro impedance gangan, awoṣe ti o han ni isalẹ nigbagbogbo lo fun iṣiro laini microstrip dada:

Ipele:

Laini tẹẹrẹ jẹ tẹẹrẹ ti okun waya ti a gbe laarin awọn ọkọ ofurufu itọkasi meji, bi o ti han ninu eeya ti o wa ni isalẹ. Awọn idiwọn aisi -itanna ti aisi -itanna ti o jẹ aṣoju nipasẹ H1 ati H2 le yatọ.

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:

Dielectric ibakan Er, wiwọn iwọn W1, W2 (trapezoid), wiwọn sisanra T ati idabobo Layer sisanra H.

W1, W2:

The calculated value must be within the red box. Ati bẹbẹ lọ.

A lo SI9000 lati ṣe iṣiro boya awọn ibeere iṣakoso ikọlu ti pade:

Ni akọkọ ṣe iṣiro iṣakoso ikọlu ọkan-opin ti laini data DDR:

Ipele TOP: sisanra idẹ 0.5oz, iwọn okun waya 5MIL, ijinna 3.8mil lati ọkọ ofurufu itọkasi, igbagbogbo aisi -itanna 4.2. Yan awoṣe, aropo ninu awọn paramita, ki o yan Iṣiro Lossless, bi o ṣe han ninu aworan:

CoaTIng tumọ si coaTIng, ati ti ko ba si idapo, fọwọsi 0 ni sisanra ati 1 ni aisi -itanna (aisi -itanna nigbagbogbo) (afẹfẹ).

Sobusitireti duro fun fẹlẹfẹlẹ fẹlẹfẹlẹ, iyẹn ni, fẹlẹfẹlẹ aisi-itanna, ni gbogbogbo lilo fr-4, sisanra ti a ṣe iṣiro nipasẹ sọfitiwia iṣiro ikọlu, igbagbogbo aisi-itanna 4.2 (igbohunsafẹfẹ kere ju 1GHz).

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

9. Prepreg/Erongba ipilẹ ti fẹlẹfẹlẹ idabobo:

PP (Prepreg) jẹ iru ohun elo aisi -itanna, ti o ni okun gilasi ati resini epoxy. Mojuto jẹ kosi TYPE ti alabọde PP, ṣugbọn awọn ẹgbẹ rẹ mejeji ni a bo pelu bankanje idẹ, lakoko ti PP kii ṣe. Nigbati o ba n ṣe awọn igbimọ lọpọlọpọ, mojuto ati PP ni a maa n lo papọ, ati pe PP lo lati ṣe asopọ laarin mojuto ati mojuto.

10. Awọn nkan ti o nilo akiyesi ni apẹrẹ lamination PCB

(1) Iṣoro oju -iwe

Apẹrẹ fẹlẹfẹlẹ ti PCB yẹ ki o jẹ iwọn, iyẹn ni, sisanra ti alabọde fẹlẹfẹlẹ ati fẹlẹfẹlẹ idẹ ti fẹlẹfẹlẹ kọọkan yẹ ki o jẹ iwọn. Mu awọn fẹlẹfẹlẹ mẹfa fun apẹẹrẹ, sisanra ti oke-GND ati alabọde agbara isalẹ yẹ ki o wa ni ibamu pẹlu sisanra ti idẹ, ATI ti GND-L2 ati L3-POWER alabọde yẹ ki o wa ni ibamu pẹlu sisanra ti idẹ. Eyi kii yoo wọ nigbati o ba laminating.

(2) Ipele ifihan yẹ ki o wa ni wiwọ pọ pẹlu ọkọ ofurufu itọkasi ti o wa nitosi (iyẹn ni, sisanra alabọde laarin fẹẹrẹ ifihan ati fẹlẹfẹlẹ ti o bo lẹgbẹ idẹ yẹ ki o kere pupọ); Wíwọ bàbà agbara ati wiwọ bàbà ilẹ yẹ ki o wa ni isunmọ pọ.

(3) Ninu ọran ti iyara to ga pupọ, awọn fẹlẹfẹlẹ afikun ni a le ṣafikun lati ya sọtọ Layer ifihan, ṣugbọn o gba ọ niyanju lati ma ṣe sọtọ awọn fẹlẹfẹlẹ agbara pupọ, eyiti o le fa kikọlu ariwo ti ko wulo.

(4) Pinpin awọn fẹlẹfẹlẹ apẹrẹ laminated aṣoju ni a fihan ni tabili atẹle:

(5) Awọn ipilẹ gbogbogbo ti eto fẹlẹfẹlẹ:

Ni isalẹ dada paati (fẹlẹfẹlẹ keji) jẹ ọkọ ofurufu ilẹ, eyiti o pese aaye aabo ẹrọ ati ọkọ ofurufu itọkasi fun wiwọ oke ti oke;

Gbogbo awọn fẹlẹfẹlẹ ifihan wa nitosi ọkọ ofurufu ilẹ bi o ti ṣee ṣe.

Yago fun isunmọ taara laarin awọn fẹlẹfẹlẹ ifihan meji bi o ti ṣee;

Ipese agbara akọkọ yẹ ki o wa nitosi bi o ti ṣee;

Symmetry ti laminate be ti wa ni ya sinu iroyin.

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

(Fun awọn ipo ti o wa ni isalẹ 50MHZ, jọwọ tọka si ki o sinmi ni deede), ipilẹ imọran ni imọran:

Ilẹ paati ati ilẹ alurinmorin jẹ ọkọ ofurufu ilẹ pipe (asà);

Ko si ẹgbẹ ti o ni afiwe ti o ni afiwe;

Gbogbo awọn fẹlẹfẹlẹ ifihan wa nitosi ọkọ ofurufu ilẹ bi o ti ṣee ṣe.

Ifihan agbara bọtini wa nitosi dida ati pe ko kọja agbegbe ipin.