With the increasing speed of PCB te huri tohu, me mohio nga kaihoahoa PCB o tenei ra ki te whakahaere me te whakahaere i te aukati o nga tohu PCB. E pa ana ki nga wa poto o te tuku tohu me te nui o nga karaka o te huringa matihiko hou, ko nga tohu PCB kua kore he hononga ngawari, engari ko nga raina tuku.

Me pehea te whakahaere PCB impedance

I roto i te mahi, me matua whakahaere i te aukati i te wa ka nui atu te tere o te taha tihi i te 1n, neke atu ranei te auau tairitenga i te 300Mhz. Ko tetahi o nga waahanga matua o te tohu PCB ko tana aukati tuuturu (te ōwehenga o te ngaohiko ki te au e haere ana te ngaru i te raina tuku tohu). Ko te koretake o te waea i runga i te poari ara iahiko he taurangi nui mo te hoahoa poari araahiko, ina koa i te hoahoa PCB mo te ara iahiko tino nui, me whakaaro mena ko te ahuatanga o te waea waea e rite ana ki nga ahuatanga e hiahiatia ana e te taputapu, tohu ranei. This involves two concepts: impedance control and impedance matching. This paper focuses on impedance control and lamination design.

Whakahaeretanga

Te Whakahautanga EImpedance, ko te kaiarahi i te poari taiawhio te katoa o nga tohu whakawhiti, kia pai ake ai te tere whakawhiti me te whakanui i tona auau, mena ko te raina na te haangai, te putu matotoru, te whanui waea me etahi atu momo rereke, ka tau huringa uara impedance, te rereketanga tohu. Na reira, ko te uara aukati o te kaiarahi i runga i te papa tereina tere, me whakahaere i roto i etahi waahanga, e mohiotia ana ko te “mana impedance”.

The impedance of a PCB trace will be determined by its inductive and capacitive inductance, resistance, and conductivity coefficient. Ko nga mea nui e awe ana i te aukati o te waea PCB ko: te whanui o te waea parahi, te matotoru o te waea parahi, te pumau tonu o te reo, te matotoru o te reo, te matotoru o te papa, te ara o te waea whenua, nga waea huri noa i nga waea waea. , etc. Ko te PCB impedance mai i te 25 ki te 120 ohm.

I roto i nga mahi, ko te raina whakawhiti PCB i te nuinga o te waa he tohu, kotahi, neke atu ranei nga papa tohutoro, me nga rauemi warahi. Ko nga tohu me nga papa te aukati i te aukati. Ka maha nga waahanga o te PCBS, ka taea te hanga i te aukati ki nga momo momo huarahi. However, whatever method is used, the impedance value will be determined by its physical structure and the electrical properties of the insulating material:

Te whanui me te matotoru o te tohu tohu

Te teitei o te matua, o nga mea kapi ranei i nga taha e rua o te tohu

Te whirihoranga o te tohu me te pereti

Insulation constants of core and prefilled materials

Ko nga raina whakawhiti PCB e rua nga waahanga matua: Mikopiko me te Raina.

Microstrip:

Ko te raina miihini ko te miihini Unuhia me te rererangi toharite i te taha kotahi, me te taha o runga me nga taha e whakaatuhia ana ki te hau (ka pania ranei), i runga ake i te papa o te raima hikoi hikoi hiko Er, me te mana hiko, te taunga ranei hei tohu. Ka rite ki te whakaatu i raro nei:

Panui: I te mahinga PCB pono, ko te kaiwhakanao poari te koti i te mata o te PCB me te papa hinu matomato, na, i te tatauranga impedance pono, ko te tauira e whakaatuhia ana i raro ake nei ka whakamahia mo te taatai ​​raina miihini papa.

Raina:

Ko te raina rīpene he rīpene waea i waenga i nga rererangi tohutoro e rua, e whakaaturia ana i te ahua i raro iho nei. Ko nga waatea dielectric o te dielectric e whakaatuhia ana e H1 me H2 ka taea te rereke.

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. A pera tonu.

Whakamahia te SI9000 hei whakatau mena kua tutuki nga whakaritenga whakahaere aukati:

Tuatahi te taatai ​​i te mana aukati kotahi o te raina raraunga DDR:

Paparanga TOP: 0.5oz matotoru parahi, 5MIL waea whanui, 3.8mil te tawhiti mai i te rererangi tohutoro, dielectric tamau 4.2. Tohua te tauira, whakakapi i nga taapiri, ka tohu i te Tatau Kore Ngarokore, e whakaaturia ana i te ahua:

Ko te tikanga o te CoaTIng ko te coaTIng, ana ki te kore he coaTIng, whakakiihia te 0 ki te matotoru me te 1 ki te dielectric (hiko hiko) (rangi).

Ko te Substrate e tohu ana i te paparanga paparanga, ara, te paparanga hiko, me te whakamahi i te fr-4, te matotoru e tatau ana ma te raupaparorohiko tatauranga, te hiko hikoi 4.2 (auau iti iho i te 1GHz).

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

9. Te whakaaro o te prepreg / Core o te paparanga kiriweti:

Ko te PP (Prepreg) he momo taonga hiko, he mea hanga ki te muka karaihe me te kara epoxy. Ko te Core he TYPE o te reo PP, engari ko ona taha e rua kua kapi ki te ipu parahi, i te mea kaore a PP. I te wa e mahi ngatahi ana nga papa multilayer, ka whakamahia ngatahi te PP me te PP, ka whakamahia te PP ki te hono i waenga i te matua me te matua.

10. Nga mea e tika ana kia whai whakaaro ki te hoahoa whakamaarama PCB

(1) Raru o te Pakanga

Ko te hoahoa paparanga o PCB kia hangarite, ara, te matotoru o te paparanga reo me te apa parahi o ia paparanga kia hangarite. Tangohia kia ono nga papanga hei tauira, ko te matotoru o te tihi-GND me te reo kaha o raro-kia rite ki te matotoru o te parahi, ME ko te GND-L2 me te reo L3-POWER kia rite ki te matotoru o te parahi. Kaore tenei e pakaru i te wa e whakamaroke ana te kiri.

(2) Ko te paparanga tohu kia tino honoa me te rererangi tohutoro pātata (ara, te matotoru reo i waenga i te papa tohu me te papa parahi kapi parahi kia iti rawa); Ko te whakakakahu parahi me te whakakakahu parahi kia whakakotahi.

(3) I te mea he tino tere te tere, ka taea te taapiri i etahi papa taapiri hei wehe i te papa tohu, engari e taunaki ana kia kaua e wehea nga papa hiko maha, kia kore ai e uru te haruru o te haruru.

(4) Ko te tohatoha o nga paparanga hoahoa whaitira whai raina e whakaaturia ana i te ripanga e whai ake nei:

(5) Nga kaupapa whanui mo te whakaritenga paparanga:

Kei raro ake o te waahanga o te waahanga (te waahanga tuarua) te papa rererangi whenua, e whakarato ana i te paparanga whakangungu o te taputapu me te papa rererangi toharite mo nga waea paparanga o runga;

Katoa nga tohu tohu e piri ana ki te papa rererangi whenua tae noa ki te waa ka taea.

Aukati i te taapiri tika i waenga i nga papa tohu e rua tae atu ki te waa e taea ana;

Ko te kohinga mana matua kia tata ki te taha e taea ana;

Ko te hangarite o te hanganga laminate ka whakaarohia.

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

(Mo nga tikanga i raro iho o te 50MHZ, tirohia ki konei ka waatea tika), e kii ana te kaupapa whakatakotoranga.

Te papa o te waahanga me te papa maitai he papa rererangi katoa (whakangungu rakau);

Kaore he paparanga waea taapiri e tata ana;

Katoa nga tohu tohu e piri ana ki te papa rererangi whenua tae noa ki te waa ka taea.

Ko te tohu matua e tata ana ki te hanganga, kaore hoki e whiti i te rohe wehe.