Ulawula njani PCB impedance?

Without impedance control, considerable signal reflection and distortion will be caused, resulting in design failure. Imiqondiso eqhelekileyo, enje ngebhasi ye-PCI, ibhasi ye-PCI-E, i-USB, i-Ethernet, inkumbulo ye-DDR, uphawu lwe-LVDS, njl. Ulawulo lwe-Impedance ekugqibeleni kufuneka luzalisekiswe kuyilo lwe-PCB, ekwabeka phambili iimfuno eziphezulu zetekhnoloji yebhodi ye-PCB. Emva kokunxibelelana nomzi-mveliso we-PCB kwaye kudityaniswe nokusetyenziswa kwesoftware ye-EDA, i-impedance ye-wiring ilawulwa ngokweemfuno zokunyaniseka komqondiso.

Iindlela ezahlukeneyo zokubamba zingabalwa ukufumana ixabiso le-impedance ehambelanayo.

Microstrip lines

• Inomtya wocingo kunye nomoya weplanethi kunye neelektri embindini. Ukuba i-dielectric engagungqiyo, ububanzi bomgca, kunye nomgama wayo ukusuka kumhlaba ojikelezayo uyalawuleka, impedance yempawu yayo iyalawuleka, kwaye ukuchaneka kuya kuba ngaphakathi kwe-5%.

What is impedance control how to perform impedance control on PCB

Umgca

Umgca weribhoni ngumtya wobhedu embindini we-dielectric phakathi kweenqwelomoya ezimbini zokuqhuba. If the thickness and width of the line, the dielectric constant of the medium, and the distance between the ground planes of the two layers are controllable, the characteristic impedance of the line is controllable, and the accuracy is within 10%.

What is impedance control how to perform impedance control on PCB

The structure of multi-layer board:

Ukulawula i-PCB ye-impedance kakuhle, kufuneka uqonde ubume be-PCB:

Ngokwesiqhelo le nto siyibiza ngokuba yibhodi ye-multilayer yenziwe ngeplate engundoqo kunye nephepha elomeleleyo eliqinileyo kunye nelinye. Ibhodi engumqobo lukhuni, ubukhulu obuthile, iipleyiti ezimbini zesonka sobhedu, ezizizinto ezisisiseko zebhodi eprintiweyo. And the semi-cured piece constitutes the so-called infiltration layer, plays the role of bonding the core plate, although there is a certain initial thickness, but in the process of pressing its thickness will occur some changes.

Ngokwesiqhelo amacala ombane e-dielectric amabini angaphandle e-multilayer a manzi manzi, kwaye izingqimba zeefoyile zobhedu ezahlukileyo zisetyenziswa ngaphandle kwala maleko mabini njengefoyile yangaphandle yobhedu. Ukucaciswa koqobo lokulinganisa kwefoyile yobhedu yangaphandle kunye nefoyile yangaphakathi yobhedu ngokubanzi yi-0.5oz, 1OZ, 2OZ (1OZ imalunga ne-35um okanye i-1.4mil), kodwa emva kothotho lonyango lomphezulu, ukutyeba kokugqibela kwefoyile yobhedu engaphandle kuya kunyuka ngokubanzi malunga 1OZ. Ifoyile yobhedu yangaphakathi sisigqubuthelo sobhedu kumacala omabini epleyiti engundoqo. Ubunzima bokugqibela bohluka kancinane kubungakanani bokuqala, kodwa ubukhulu becala buncitshiswa ngum ngenxa yeetching.

The outermost layer of the multilayer board is the welding resistance layer, which is what we often say “green oil”, of course, it can also be yellow or other colors. The thickness of the solder resistance layer is generally not easy to determine accurately. The area without copper foil on the surface is slightly thicker than the area with copper foil, but because of the lack of copper foil thickness, so the copper foil is still more prominent, when we touch the printed board surface with our fingers can feel.

Xa ubungakanani bebhodi eprintiweyo benziwe, kwelinye icala, ukhetho olufanelekileyo lweeparitha zezinto ezifunekayo, kwelinye icala, ubukhulu bokugqibela bephepha eliphilisiweyo liya kuba lincinci kunobunzima bokuqala. Oku kulandelayo sisakhiwo esi-laminated se-6-layer:

What is impedance control how to perform impedance control on PCB

PCB parameters:

Different PCB plants have slight differences in PCB parameters. Through communication with circuit board plant technical support, we obtained some parameter data of the plant:

Umphezulu ngefoyile ye yobhedu:

There are three thicknesses of copper foil that can be used: 12um, 18um and 35um. Ubunzima bokugqibela emva kokugqiba malunga ne-44um, 50um kunye ne-67um.

Ipleyiti engundoqo: I-S1141A, i-standard standard ye-FR-4, iipleyiti ezimbini zesonka ezinezonka zihlala zisetyenziswa. Ukucaciswa kokukhetha kunokuchongwa ngokunxibelelana nomenzi.

Semi-cured tablet:

Ukucaciswa (ubukhulu bokuqala) ngama-7628 (0.185mm), 2116 (0.105mm), 1080 (0.075mm), 3313 (0.095mm). Ubunzima bokwenyani emva kokucinezela kuhlala malunga ne-10-15um ngaphantsi kwexabiso lokuqala. Amacwecwe amathathu anyangiweyo ubuninzi anokusetyenziselwa umaleko ofanayo wokungena, kwaye ubukhulu beepilisi ezintathu eziphilisiweyo azinakufana, ubuncinci iipilisi ezinokusetyenziswa ezinesiqingatha zinokusetyenziswa, kodwa abanye abavelisi kufuneka basebenzise ubuncinci ezimbini . Ukuba ukutyeba kwesiqwenga esinganyangekiyo akwanelanga, ifoyile yobhedu kumacala omabini epleyiti esisiseko inokuxhonywa, emva koko isiqwenga esiphilisiweyo singadityaniswa macala omabini, ukuze umaleko wokungena ngaphakathi kufezekisiwe.

Umaleko welding umaleko:

Ubungakanani be-solder yokumelana nocwecwe kwi-foil foil yi-C2≈-8-10um. Ubungakanani be-solder yokumelana nocwecwe kumphezulu ngaphandle kwefoyile yobhedu yi-C1, eyahluka ngokobunzima bobhedu ngaphezulu. Xa ubukhulu bobhedu phezu komhlaba bungu-45um, C1≈13-15um, kwaye xa ubukhulu bobhedu phezu komhlaba bungu-70um, C1-17-18um.

Icandelo lokuhamba:

Singacinga ukuba icandelo lomnqamlezo wocingo luxande, kodwa eneneni yitrapezoid. Ukuthatha umaleko we-TOP njengomzekelo, xa ubukhulu befoyile yobhedu yi-1OZ, umphetho ongezantsi we-trapezoid yi-1MIL mfutshane kunomphetho ongezantsi. Umzekelo, ukuba ububanzi bomgca bungu-5MIL, ke amacala aphezulu nasezantsi amalunga ne-4MIL kwaye amacala asezantsi nangaphantsi amalunga ne-5MIL. Umahluko phakathi kwemiphetho ephezulu neyasezantsi inxulumene nobhedu. Itheyibhile elandelayo ibonisa ubudlelwane phakathi kwephezulu kunye nezantsi kwetrapezoid phantsi kweemeko ezahlukeneyo.

What is impedance control how to perform impedance control on PCB

Ukuvunyelwa: Ukuvunyelwa kwamashiti anyangekiweyo ahambelana nobukhulu. Le tafile ilandelayo ibonisa ubukhulu kunye neeparamitha zokuvumeleka zeentlobo ezahlukeneyo zamashiti anyangiweyo:

What is impedance control how to perform impedance control on PCB

Ukuhlala kwe-dielectric yeplate inxulumene nezinto ezisetyenzisiweyo. Ukuqhubeka kwe-dielectric yeplate ye-FR4 yi-4.2 – 4.7, kwaye iyancipha ngokwanda kwamaxesha.

Ilahleko le-dielectric factor: izixhobo zedelectric eziphantsi kwentshukumo yokutshintsha kwendawo yombane, ngenxa yobushushu kunye nokusetyenziswa kwamandla kuthiwa kukulahleka kwe-dielectric, kuhlala kuchazwa yilahleko ye-dielectric factor Tan δ. Ixabiso eliqhelekileyo le-S1141A ngu-0.015.

Ubuncinci bomgca wobubanzi kunye nokushiyana komgca wokuqinisekisa ukuqinisekisa ngomatshini: 4mil / 4mil.

Isixhobo sokubala sokulinganisa sokungenisa:

Xa siqonda ubume bebhodi ye-multilayer kunye nokuqonda iiparameter ezifunekayo, sinokubala i-impedance ngokusebenzisa isoftware ye-EDA. Ungasebenzisa iAllegro ukwenza oku, kodwa ndincoma iPolar SI9000, sisixhobo esihle sokubala impedance yempawu kwaye ngoku isetyenziswa yimizi mveliso emininzi yePCB.

Xa ubala ukungahambelani kweempawu zangaphakathi kwempawu zombini kunye nomgca wesiphelo esinye, uya kufumana kuphela umahluko omncinci phakathi kwePolar SI9000 kunye neAllegro ngenxa yeenkcukacha ezithile, ezinje ngemilo yecandelo lomnqamlezo wocingo. Nangona kunjalo, ukuba kubalwa impedance yesimpawu somqondiso ongaphezulu, ndicebisa ukuba ukhethe umfuziselo odityanisiweyo endaweni yemodeli yomphezulu, kuba iimodeli ezinjalo zithathela ingqalelo ubukho bokumelana ne-solder, ke iziphumo ziya kuchaneka ngakumbi. Oku kulandelayo sisikrini esisecaleni somda womhlaba owahlulwe ngokungafaniyo obalwe ngePolar SI9000 ithathela ingqalelo umaleko wokumelana nesoder:

What is impedance control how to perform impedance control on PCB

Kuba ubukhulu be-solder yokumelana nolawulo abulawulwa ngokulula, indlela enokusetyenziswa nayo inokusetyenziswa, njengoko kucetyisiwe ngumvelisi webhodi: thabatha ixabiso elithile kwimodeli yokubala yeSurface. Kuyacetyiswa ukuba ukungangqinelani kwe-impedance ibe ngu-8 ohms kunye nesiphelo esisiphelo esinye sibe ngu-2 ohms.

Umahluko weemfuno zePCB zewiring

(1) Chonga imowudi ye-wiring, iiparameter kunye nokubala kwe-impedance. Zimbini iintlobo zomahluko weendlela zendlela yomgaqo: umaleko wangaphandle imo yokwahlula imo yendlela kunye nolwahlulo lwangaphakathi lwendlela yokwahlula imo. Ukuthintela kungabalwa ngesoftware yokubala ye-impedance (efana ne-POLAR-SI9000) okanye ifomula yokubala ye-impedance ngokuseta okufanelekileyo kweparameter.

(2) Imigca ye-isometric efanayo. Chonga ububanzi bomgca kunye nokushiya izithuba, kwaye ulandele ngokungqongqo ububanzi bomgca obaliweyo kunye nezithuba xa uhamba. Isithuba phakathi kwemigca emibini kufuneka sihlale singatshintshanga, Oko kukuthi, ukugcina ukufana. There are two ways of parallelism: one is that the two lines walk in the same side-by-side layer, and the other is that the two lines walk in the over-under layer. Ngokubanzi zama ukunqanda ukusebenzisa umqondiso umahluko phakathi kweengqimba, oko kukuthi kuba kulungiso lwangempela lwe-PCB kwinkqubo, ngenxa yokuchaneka kokulungelelaniswa kokulungelelaniswa okuthe tye kuncinci kakhulu kunokuba kubonelelwe phakathi kokuchaneka kokuchaphazeleka, nakwinkqubo yokulahleka kwelemitha elaminethiweyo, awunakuqinisekisa ukuba umahluko phakathi komgca olinganayo ulingana nobukhulu be-dielectric ye-interlayer, iya kubangela umahluko phakathi kwamanqanaba okwahluka kotshintsho lwe-impedance. Kuyacetyiswa ukuba usebenzise umahluko ngaphakathi koluhlu olufanayo kangangoko.