Kudzora sei PCB impedance?

Without impedance control, considerable signal reflection and distortion will be caused, resulting in design failure. Zviratidzo zvakajairika, senge PCI bhazi, PCI-E bhazi, USB, Ethernet, DDR ndangariro, LVDS chiratidzo, nezvimwe, zvese zvinoda impedance kudzora. Impedance control ultimately needs to be realized through PCB design, which also puts forward higher requirements for PCB board technology. After communication with PCB factory and combined with the use of EDA software, the impedance of wiring is controlled according to the requirements of signal integrity.

Nzira dzakasiyana dzewiring dzinogona kuverengerwa kuti uwane iyo inoenderana impedance kukosha.

Microstrip lines

• Inosanganisira tambo yetambo ine pasi ndege uye dielectric iri pakati. Kana iyo dielectric inogara iripo, hupamhi hwemutsara, uye nhambwe yayo kubva pasi pevhu inodzora, saka hunhu hwayo impedance inodzora, uye iko kurongeka kunenge kuri mukati me ± 5%.

What is impedance control how to perform impedance control on PCB

Stripline

Ribhoni mutsetse tambo yemhangura iri pakati pe dielectric pakati pendege mbiri dzinoitisa. 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:

Kuti udzore pcb impedance mushe, zvinodikanwa kuti unzwisise chimiro chePCB:

Kazhinji zvatinodaidza multilayer bhodhi inoumbwa nepakati ndiro uye semi-yakasimbiswa pepa rakamisikidzwa pamwe neumwe neumwe. Core board yakaoma, yakatarwa ukobvu, maviri chingwa chendarira ndiro, chinova chinhu chekutanga chebhodhi rakadhindwa. 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.

Kazhinji iwo ekupedzisira maviri ma dielectric akaturikidzana e multilayer akanyorova matete, uye akapatsanurwa emhangura mafirita matanda anoshandiswa kunze kwemaviri aya materu sekunze mhangura foil. Iyo yepakutanga ukobvu kutaurwa kwekunze mhangura foil uye yemukati mhangura foil inowanzo kuve 0.5oz, 1OZ, 2OZ (1OZ inenge 35um kana 1.4mil), asi mushure mekuteedzana kwekurapwa kwepasirese, iyo yekupedzisira ukobvu hwekunze mhangura foil inowanzo kuwedzera ne 1OZ. Iyo yemukati yemhangura foil ndiyo yemhangura inovhara pamativi ese eplate ndiro. Kukora kwekupedzisira kwakasiyana zvishoma kubva pakukora kwepakutanga, asi kazhinji kunodzikiswa neuverengeka um nekuda kwekucheka.

Rwunze rwekunze rwe multilayer board ndeye welding resistance layer, zvinova ndizvo zvatinogara tichiti “girini mafuta”, hongu, inogona zvakare kuve yero kana mamwe mavara. 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.

When a particular thickness of the printed board is made, on the one hand, reasonable choice of material parameters is required, on the other hand, the final thickness of the semi-cured sheet will be smaller than the initial thickness. Izvi zvinotevera zvakajairwa 6-dura rakamisikidzwa chimiro:

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:

Pamusoro mhangura foil:

There are three thicknesses of copper foil that can be used: 12um, 18um and 35um. Iyo yekupedzisira ukobvu mushure mekupedza ingangoita 44um, 50um uye 67um.

Core ndiro: S1141A, yakajairwa FR-4, mahwendefa maviri emhangura ane chingwa anowanzo shandiswa. Idzo sarudzo dzekuda dzinogona kutemwa nekubata mugadziri.

Semi-cured tablet:

Magadzirirwo (epakutanga ukobvu) ari 7628 (0.185mm), 2116 (0.105mm), 1080 (0.075mm), 3313 (0.095mm). Ukobvu chaihwo mushure mekutsimbirira kazhinji hunowanzo kuita 10-15um pasi peiyo yekutanga kukosha. Mahwendefa matatu anokwaniswa kuita matatu anokwanisa kushandiswa kune imwechete yekupinda mukati, uye ukobvu hwemapiritsi matatu akasimbiswa haugone kufanana, chero mapiritsi akapora hafu anogona kushandiswa, asi vamwe vagadziri vanofanirwa kushandisa kanenge maviri. . If the thickness of the semi-cured piece is not enough, the copper foil on both sides of the core plate can be etched off, and then the semi-cured piece can be bonded on both sides, so that a thicker infiltration layer can be achieved.

Nemishonga nomoto rukoko:

The thickness of the solder resist layer on the copper foil is C2≈8-10um. The thickness of the solder resist layer on the surface without copper foil is C1, which varies with the thickness of copper on the surface. When the thickness of copper on the surface is 45um, C1≈13-15um, and when the thickness of copper on the surface is 70um, C1≈17-18um.

Chikamu chakayambuka:

Isu taizofunga kuti chikamu chemuchinjikwa tambo tambo, asi ichokwadi trapezoid. Kutora iyo yepamusoro TOP semuenzaniso, kana iwo hukobvu hwemhangura foil iri 1OZ, iyo yekumusoro yepasi kumucheto kwetrapezoid ndeye 1MIL ipfupi pane yepasi yepazasi kumucheto. Semuenzaniso, kana hupamhi hwehupamhi hwave 5MIL, ipapo kumusoro uye kuzasi mativi anenge 4MIL uye ezasi uye ezasi mativi anenge 5MIL. The difference between top and bottom edges is related to copper thickness. The following table shows the relationship between top and bottom of trapezoid under different conditions.

What is impedance control how to perform impedance control on PCB

Kubvumirwa: Iko kubvumidzwa kwemashizha akasimba-akapora anoenderana nehukuru. Iyi tafura inotevera inoratidza ukobvu uye mvumo paramita yemhando dzakasiyana dzemashizha akapora.

What is impedance control how to perform impedance control on PCB

The dielectric constant of the plate is related to the resin material used. The dielectric constant of FR4 plate is 4.2 — 4.7, and decreases with the increase of frequency.

Dhizimusi kurasikirwa chinhu: dielectric zvinhu pasi pechiito chekuchinjisa magetsi munda, nekuda kwekupisa uye simba rekushandisa kunodaidzwa kuti dielectric kurasikirwa, kazhinji kunoratidzwa ne dielectric kurasikirwa chinhu Tan δ. Iyo chaiyo kukosha kweS1141A ndeye 0.015.

Minimum mutsetse upamhi uye mutsetse spacing kuona machine: 4mil / 4mil.

Impedance kukarukureta chishandiso sumo:

Kana isu tikanzwisisa chimiro che multilayer bhodhi uye nekugona zvinodiwa parameter, tinogona kuverenga iyo impedance kuburikidza neESDA software. Unogona kushandisa Allegro kuita izvi, asi ini ndinokurudzira Polar SI9000, chinova chishandiso chakanaka chekuverenga hunhu impedance uye iko zvino inoshandiswa nemafekitori mazhinji ePBB.

Kana uchiverenga hunhu impedance yechiratidzo chemukati chese musiyano mutsetse uye imwechete terminal tambo, iwe unowana chete musiyano mudiki pakati pePolar SI9000 neAllegro nekuda kwemamwe ruzivo, senge chimiro chechikamu chemuchinjikwa chetambo. Nekudaro, kana iri yekuverenga hunhu impedance yeiyo Surface chiratidzo, ini ndinokurudzira kuti usarudze iyo Yakavharwa modhi pachinzvimbo cheiyo Surface modhi, nekuti mhando dzakadai dzinofunga nezve kuvepo kweiyo solder kuramba rukoko, saka mhedzisiro yacho ichave yakanyatsojeka. The following is a partial screenshot of the surface differential line impedance calculated with Polar SI9000 considering the solder resistance layer:

What is impedance control how to perform impedance control on PCB

Sezvo iyo hukobvu hweiyo solder yekumisikidza rukoko isiri nyore kudzorwa, nzira yekufungidzira inogona zvakare kushandiswa, sekurudzirwa nemugadziri webhodhi: bvisa yakatarwa kukosha kubva kuSurface modhi kuverenga. Zvinokurudzirwa kuti iyo kusiyanisa impedance ive minus 8 ohms uye imwechete-yekupedzisira impedance ive minus 2 ohms.

Musiyano pcb zvinodiwa wiring

(1) Sarudza iyo wiring modhi, parameter uye impedance kuverenga. Kune maviri marudzi emisiyano modhi yemutsetse nzira: yekunze rukoko microstrip mutsara musiyano modhi uye yemukati rukoko tambo mutsara musiyano maitiro. Impedance inogona kuverengerwa neyakaenderana impedance kuverenga software (senge POLAR-SI9000) kana impedance kukaromura fomula kuburikidza zvine musoro paramende marongero.

(2) Mitsara yakafanana isometric. Sarudza upamhi hwemutsara uye nzvimbo, uye nyatsoteedzera yakaverengwa mutsetse upamhi uye nzvimbo pakati pekutenderera. Iyo nzvimbo pakati pemitsetse miviri inofanira kugara isina kuchinjika, ndiko kuti, kuti irambe yakafanana. 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. Kazhinji edza kudzivisa kushandisa musiyano chiratidzo pakati pezvikamu, zvinodaro nekuti mukugadzirisa chaiko kwePBB mukuita, nekuda kwekukanzura kwekururamisa kwakaringana kwakaderera zvakanyanya kupfuura kupihwa pakati peiyo chaiyo, uye mukuita kwekurasikirwa dielectric yekuparara, haikwanise kuvimbisa musiyano wemutsetse spacing yakaenzana nehupamhi hweiyo interlayer dielectric, inokonzeresa musiyano uripo pakati pezvikamu zve mutsauko we impedance shanduko. Inokurudzirwa kushandisa musiyano uri mukati meiyo imwecheteyo napo napo.