With the increasing speed of PCB switch switch, yanhasi PCB vagadziri vanofanirwa kunzwisisa uye kudzora iyo impedance yePCB zvisaririra. Inoenderana nepfupi chiratidzo chekufambisa nguva uye yakakwira wachi mareti emazuva ano maseketi edhijitari, pcb zvisaririra hazvisisiri nyore kubatana, asi mitsara yekufambisa.

Maitiro ekudzora pcb impedance

Mukuita, zvinodikanwa kudzora trace impedance kana dijita yekumahombekombe kumhanya ichidarika 1ns kana frequency analog inopfuura 300Mhz. Imwe yematanho akakosha ePCB trace ndeye impedance yayo (iyo reshiyo yemagetsi kusvika parizvino sezvo masaisai achifamba achitevedza mutsara wekutumira chiratidzo). Hunhu impedance yewaya pane yakadhindwa redunhu bhodhi yakakosha indekisi yedunhu bhodhi dhizaini, kunyanya muPCB dhizaini yeakakwira frequency dunhu, inofanirwa kutariswa kana hunhu impedance yetambo inoenderana nehunhu impedance inodiwa necheni kana chiratidzo. This involves two concepts: impedance control and impedance matching. This paper focuses on impedance control and lamination design.

Impedance kudzora

EImpedance Kudzora, conductor mubato redunhu ichave nemhando dzese dzekufambisa masaini, kuitira kuti ivandudze huwandu hwekutapurirana uye inofanirwa kuwedzera kuwanda kwayo, kana iyo tambo yacho pachayo nekuda kwekucheka, kuomesa ukobvu, upamhi hwetambo nezvimwe zvinhu zvakasiyana, zvinokonzeresa. impedance kukosha shanduko, chiratidzo chinokanganisa. Naizvozvo, iyo impedance kukosha kweiye conductor pane yepamusoro-yekumhanyisa wedunhu bhodhi inofanirwa kudzorwa mukati meimwe nhanho, inozivikanwa se “impedance control”.

The impedance of a PCB trace will be determined by its inductive and capacitive inductance, resistance, and conductivity coefficient. Izvo zvakakosha zvinhu zvinokanganisa iyo impedance yePCB wiring ndeiyi: iyo upamhi hwendarira waya, ukobvu hwendarira waya, iyo dielectric inogara pakati nepakati, ukobvu hwepakati, ukobvu hwepad, nzira yevhu tambo, iyo wiring yakatenderedza iyo wiring. , nezvimwe. Pcb impedance masosi kubva 25 kusvika 120 ohm.

Mukuita, pcb yekuparadzira tambo inowanzo kuve ne trace, imwe kana anopfuura mareferenzi matanda, uye zvigadzirwa zvekudzivirira. Zvisaririra uye zvidimbu zvinoumba iyo impedance yekudzora. PCBS inowanzo kuve yakawanda-yakaturikidzana, uye iyo impedance yekudzora inogona kuvakwa munzira dzakasiyana siyana. However, whatever method is used, the impedance value will be determined by its physical structure and the electrical properties of the insulating material:

Upamhi uye ukobvu hwechiratidzo chekutsvaga

Iko kukwirira kweiyo yepakati kana yekuisa zvinhu kune ese mativi eronda

Kugadziriswa kwekuteedzera uye ndiro

Insulation constants of core and prefilled materials

Pcb yekufambisa mitsara inouya nenzira mbiri huru: Microstrip uye Stripline.

Microstrip:

Mutsetse we microstrip mutsetse unoitisa ndege ine rezve ndege kudivi rimwe chete, iine kumusoro uye mativi akafumurwa nemhepo (kana kuti akafukidzwa), pamusoro pechiso chekuputira nguva dzese Er wedunhu bhodhi, iine magetsi kana pasi sechirevo. Sezvinoratidzwa pazasi:

Ongorora: Mukugadzira chaiko kwePBB, bhodhi rinogadzira kazhinji rinosungira pamusoro payo pcb ine dura remafuta akasvibira, saka mukuverenga chaiyo impedance, iyo modhi inoratidzwa pazasi inowanzo shandiswa pamusoro peiyo microstrip mutsara kuverenga:

Stripline:

Ribhoni mutsetse ribhoni rerwambo rwakaiswa pakati pematanho maviri enongedzo, sezvakaratidzwa mumufananidzo uri pazasi. Iyo dielectric inogadzikana yedhielectric inomiririrwa neH1 neH2 inogona kuve yakasiyana.

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 constant Er, wiring width W1, W2 (trapezoid), wiring thickness T and insulation layer thickness H.

W1, W2:

The calculated value must be within the red box. Uye zvakadaro.

SI9000 inoshandiswa kuverenga kana iyo impedance control zvinodiwa zvasangana:

Kutanga kuverenga iyo yekupedzisira-yekupedzisira impedance kudzora kweDDR data mutsara:

TOP rukoko: 0.5oz mhangura ukobvu, 5MIL waya upamhi, 3.8mil chinhambwe kubva panotaurwa ndege, dielectric inogara 4.2. Sarudza iyo modhi, chinja mune ma parameter, uye sarudza Lossless Kukarukureta, sezvakaratidzwa mumufananidzo:

CoaTIng zvinoreva coaTIng, uye kana pasina coaTIng, zadza 0 muukobvu uye 1 mu dielectric (dielectric kugara) (mhepo).

Substrate inomiririra substrate layer, ndiko kuti, dielectric layer, kazhinji ichishandisa fr-4, ukobvu hunowanikwa neimedance kukarukureta software, dielectric inogara iri 4.2 (frequency isingasviki 1GHz).

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

9.Prepreg / Core pfungwa yekuvhara dura:

PP (Prepreg) rudzi rwe dielectric zvinhu, rakagadzirwa negirazi fiber uye epoxy resin. Core iri chaizvo TYPE yePP yepakati, asi mativi ayo maviri akafukidzwa nendarira foil, nepo PP isiri. Paunenge uchigadzira mabhodhi akawanda, musimboti nePP zvinowanzoshandiswa pamwechete, uye PP inoshandiswa kusunga pakati penzvimbo nepakati.

10. Nyaya dzinoda kutariswa muPCB lamination dhizaini

(1) Dambudziko reWarpage

Iyo dhizaini dhizaini yePBB inofanira kuenzana, ndiko kuti, ukobvu hwesvikiro nhurikidzwa uye mhangura denderedzwa rega rega rinofanirwa kunge rakaenzana. Tora zvidimbu zvitanhatu semuenzaniso, ukobvu hwepamusoro-GND uye yepasi-simba svikiro inofanirwa kuenderana nehupamhi hwemhangura, Uye iyo yeGND-L2 uye L3-SIMBA yepakati inofanirwa kuenderana nehupamhi hwemhangura. Izvi hazvingaruki pakumomesa.

(2) Chidimbu chemasaini chinofanira kunge chakabatanidzwa pamwe chete neiyo ndege yekumberi (kureva kuti, iyo yepakati ukobvu pakati pechiratidzo cheyadhi uye padyo neyakafukidza mhangura yekumonera inofanira kunge iri diki kwazvo); Simba remhangura kupfeka uye yepasi kupfeka kupfeka kunofanirwa kuve kwakabatanidzwa.

(3) Panyaya yekumhanya kwazvo, mamwe maratidziro anogona kuwedzerwa kupatsanura rukoko rwechiratidzo, asi zvinokurudzirwa kusaparadzanisa matinji emagetsi akawanda, anogona kukonzeresa kupesana kweruzha.

(4) Kugovaniswa kweyakajairwa marara dhizaini inoratidzwa mune inotevera tafura:

(5) Mazano akajairika ekurongedzwa kwehurongwa:

Pazasi pechinhu chepamusoro (chikamu chechipiri) ndiyo ndege yepasi, iyo inopa dziviriro yechigadzirwa uye nendege yekurevera yeiyo yepamusoro wiring wiring;

Matanho ese emasaini ari padhuze nepasi pepasi sezvinobvira.

Dzivisa kuenderana kwakananga pakati pezvikamu zviviri zvemasaini kure sezvinobvira;

Iyo huru magetsi inofanirwa kunge iri padhuze sezvinobvira;

Symmetry ye laminate chimiro inofungidzirwa.

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

(Nezve mamiriro ari pazasi 50MHZ, ndokumbira utarise kwariri uye uzorodze nenzira kwayo), iyo mamiriro ekuraira inokurudzirwa.

Chinoumbwa pamusoro uye pamusoro pechiso chakazara pasi ndege (nhovo);

Hapana padyo neparutivi wiring dura;

Matanho ese emasaini ari padhuze nepasi pepasi sezvinobvira.

Chiratidzo chakakosha chiri padhuze nekuumbwa uye hachiyambuke nzvimbo yekuparadzanisa.