Mokhoa oa ho laola PCB impedance?

Without impedance control, considerable signal reflection and distortion will be caused, resulting in design failure. Lipontšo tse tloaelehileng, joalo ka bese ea PCI, bese ea PCI-E, USB, Ethernet, memori ea DDR, lets’oao la LVDS, jj, kaofela li hloka taolo ea impedance. Taolo Impedance qetellong lokela ho hlokomela ka moralo PCB, eo le eona e beha pele ditlhoko phahameng bakeng sa theknoloji PCB boto. Kamora ho buisana le fektheri ea PCB mme e kopantsoe le ts’ebeliso ea software ea EDA, khatello ea wiring e laoloa ho latela litlhoko tsa bots’epehi ba lets’oao.

Mekhoa e fapaneng ea wiring e ka baloa ho fumana boleng bo lekanang ba impedance.

Microstrip lines

• E na le mohala oa terata o nang le sefofane sa fatše le dielectric bohareng. Haeba khauta ea dielectric, bophara ba mola, le sebaka sa eona ho tloha sefofaneng se ka laoloa, joale tšebetso ea eona ea semelo e ea laoleha, ‘me ho nepahala ho tla ba ka hara ± 5%.

What is impedance control how to perform impedance control on PCB

Stripline

Mohala oa lente ke karolo ea koporo bohareng ba dielectric lipakeng tsa lifofane tse peli tse tsamaisang. 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:

E le hore ho laola PCB impedance hantle, ho ke ke ho hlokahala hore ho utloisisa sebopeho sa PCB:

Hangata seo re se bitsang boto multilayer e entsoe ka poleiti konokono le lakane seka-solidified laminated hammoho le mong ho e mong. Boto ea mantlha ke botenya bo thata, bo khethehileng, poleiti ea bohobe e ‘meli, e leng thepa ea mantlha ea boto e hatisitsoeng. 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.

Hangata likarolo tse peli tse ka ntle ka ho fetesisa tsa dielectric tsa multilayer li na le metsi, ‘me likarolo tse arohaneng tsa foil tsa koporo li sebelisoa kantle ho likarolo tsena tse peli e le koporo ea koporo e kantle. The botenya pele ga tlhaloso ea foil ntle koporo le foil hare koporo ka kakaretso 0.5oz, 1OZ, 2OZ (1OZ ke ka 35um kapa 1.4mil), empa ka mor’a letoto la kalafo holim, botenya ho qetela ea foil bokantle koporo tla kakaretso eketsa ka hoo e ka bang 1OZ. Sekoahelo sa koporo se kahare ke sekoaelo sa koporo mahlakore ka bobeli a poleiti ea mantlha. Botenya ba hoqetela bo fapana hanyane le botenya ba mantlha, empa ka kakaretso bo fokotsoa ke um tse ‘maloa ka lebaka la manonyeletso.

Lera le ka ntle ka ho fetesisa la board ea multilayer ke lera le hanyetsang tjheseletsa, e leng seo re atisang ho se bua “oli e tala”, ehlile, e ka ba bosehla kapa mebala e meng. 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. Se latelang ke sebopeho se tloahelehileng sa marulelo a 6:

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:

Bokaholimo foil koporo:

There are three thicknesses of copper foil that can be used: 12um, 18um and 35um. Botenya ba hoqetela kamora ho qeta bo ka ba 44um, 50um le 67um.

Poleiti ea mantlha: S1141A, standard FR-4, lipoleiti tse peli tse nang le bohobe li sebelisoa hangata. Lintlha tse ikhethileng li ka khethoa ka ho ikopanya le moetsi.

Semi-cured tablet:

Litlhaloso (botenya ba mantlha) ke 7628 (0.185mm), 2116 (0.105mm), 1080 (0.075mm), 3313 (0.095mm). Botenya ba ‘nete kamora ho tobetsa hangata bo ka tlase ho 10-15um ho feta boleng ba mantlha. Matlapa a 3 a sa foleng a ka sebelisoa bakeng sa lera le le leng la ho kenella, ‘me botenya ba matlapa a 3 a phekotsoeng ha a tšoane, bonyane matlapa a phekotsoeng a halofo a ka sebelisoa, empa baetsi ba bang ba tlameha ho sebelisa bonyane tse peli . Haeba botenya ba sengoathoana se phekotsoeng ha boa lekana, foil ea koporo ka mahlakore ka bobeli a poleiti ea mantlha e ka ts’oaroa, ebe sengoathoana se phekotsoeng se ka tlamahisoa ka mahlakore ka bobeli, e le hore mokelikeli o motenya oa ho kenella o ka finyeletse.

Khanyetso ho tjheseletsa lera:

Botenya ba solder hanela lera ho foil ea koporo ke C2≈-8-10um. The bokima ba solder hanela lera holim ntle foil koporo ke C1, eo fapana le botenya ba koporo holim. Ha botenya ba koporo holim’a metsi e le 45um, C1≈13-15um, mme ha botenya ba koporo holimo e le 70um, C1≈17-18um.

Karolo e haolang:

Re ka nahana hore karolo ea sefapano sa terata ke khutlonne, empa ha e le hantle ke trapezoid. Ho nka lera la TOP e le mohlala, ha botenya ba foil ea koporo e le 1OZ, bohale bo kaholimo bo ka tlase ba trapezoid ke 1MIL e khuts’oane ho feta bohale bo tlase bo tlase. Mohlala, haeba bophara ba mola ke 5MIL, mahlakore a holimo le a tlase a ka ba 4MIL mme mahlakore a tlase le a tlase a ka ba 5MIL. Phapang lipakeng tsa mabota a holimo le a tlase e amana le botenya ba koporo. Tafole e latelang e bonts’a kamano lipakeng tsa holimo le tlase ha trapezoid tlasa maemo a fapaneng.

What is impedance control how to perform impedance control on PCB

Ho lumelloa: Ho lumelloa ha maqephe a sa phekolehang ho amana le botenya. Tafole e latelang e bonts’a mekhahlelo ea botenya le tumello ea mefuta e fapaneng ea maqephe a phekotsoeng:

What is impedance control how to perform impedance control on PCB

Khafetsa ea dielectric ea poleiti e amana le lehoakhoa le sebelisitsoeng. Khala ea dielectric ea poleiti ea FR4 ke 4.2 – 4.7, mme ea fokotseha ka keketseho ea makhetlo.

Tahlehelo ea dielectric: lisebelisoa tsa dielectric tlasa ts’ebetso ea ho chencha tšimo ea motlakase, ka lebaka la mocheso le ts’ebeliso ea matla e bitsoa tahlehelo ea dielectric, hangata e hlahisoang ke tahlehelo ea dielectric factor Tan δ. Boleng bo tloaelehileng ba S1141A ke 0.015.

Bonyane ba mohala bophara le sebaka sa mela ho netefatsa machining: 4mil / 4mil.

Sesebelisoa sa ho bala sa Impedance selelekela:

Ha re utloisisa sebopeho sa boto ea multilayer mme re tseba mekhahlelo e hlokahalang, re ka bala impedance ka software ea EDA. U ka sebelisa Allegro ho etsa sena, empa ke khothaletsa Polar SI9000, e leng sesebelisoa se setle sa ho bala tšebetso ea semelo sa ‘mele’ me joale se sebelisoa ke lifeme tse ngata tsa PCB.

Ha o bala tšobotsi e khutsitseng ea lets’oao le kahare la mola oa phapang le mola o le mong oa terminal, o tla fumana phapang e nyane feela lipakeng tsa Polar SI9000 le Allegro ka lebaka la lintlha tse ling, joalo ka sebopeho sa karolo ea sefapano sa terata. Leha ho le joalo, haeba e le ho bala tšebetso ea tšebetso ea lets’oao la bokaholimo, ke khothaletsa hore o khethe mofuta o koahetsoeng ho fapana le mofuta oa bokaholimo, hobane meetso e joalo e nahanela boteng ba lera la ho hanyetsa la solder, ka hona liphetho li tla nepahala haholoanyane. Se latelang ke skrini sa karolo sa “impedance” ea phapang ea bokaholimo se baloang le Polar SI9000 ho latela lera la ho hanyetsa la solder:

What is impedance control how to perform impedance control on PCB

Kaha botenya ba lehare la solder ha bo laoloe habonolo, mokhoa o batlang o sebelisoa o ka sebelisoa, joalo ka ha ho khothaletsoa ke moetsi oa boto: tlosa boleng bo itseng ho palo ea mohlala oa Surface. Ho kgothaletswa hore phokotso ea phapang e be minus 8 ohms le impedance ea pheletso e le ‘ngoe e be minus 2 ohms.

Litlhoko tse fapaneng tsa PCB bakeng sa wiring

(1) Fumana mofuta oa wiring, litekanyo le lipalo tsa impedance. Ho na le mefuta e ‘meli ea mefuta ea phapang ea ho tsamaisa line: kantle ho mokelikeli oa microstrip phapang ea mohala le mofuta oa kahare oa mola oa phapang ea mola. Impedance e ka baloa ka software e amanang le impedance calculation (joalo ka POLAR-SI9000) kapa foromo ea lipalo tsa impedance ka ho beha maemo a utloahalang.

(2) Litsela tse tšoanang tsa isometric. Etsa qeto ea bophara ba mola le sebaka, ‘me u latele ka botebo bophara ba mola le sebaka ha ho tsamaisoa. Sebaka se lipakeng tsa mela e ‘meli se tlameha ho lula se sa fetohe, ke hore, ho lula se ts’oana. 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. Ka kakaretso leka ho qoba ho sebelisa phapang pontšo pakeng tsa le dikarolo, e leng hobane ka ho e lokisa ea sebele ea PCB ka tshebetso, ka lebaka la ho cascading laminated lolamisiwa nepahala e tlaase haholo ho feta feela pakeng tsa sebetsa ka ho nepahetseng mananose, ‘me ka tshebetso ya ho laminated tahlehelo dielectric, ha e khone ho netefatsa phapang ea mohala o lekanang le botenya ba dielectric e kenang, e tla baka phapang lipakeng tsa likarolo tsa phapang ea phetoho ea impedance. Ho kgothaletswa ho sebelisa phapang kahare ho lera le le leng kamoo ho ka khonehang.