Ahoana no mifehy PCB impedance?

Without impedance control, considerable signal reflection and distortion will be caused, resulting in design failure. Famantarana mahazatra, toy ny bus PCI, bus PCI-E, USB, Ethernet, fahatsiarovana DDR, famantarana LVDS, sns., Mila fanaraha-maso impedance daholo. 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.

Ny fomba fampitaovana samihafa dia azo isaina hahazoana ny sandan’ny impedance mifanaraka aminy.

Microstrip lines

• Izy io dia misy tariby tariby miaraka amin’ny fiaramanidina ambanin’ny tany sy diélectric eo afovoany. Raha tsy azo fehezina ny diélectrique tsy tapaka, ny sakan’ny tsipika ary ny elanelany amin’ny fiaramanidina dia azo fehezina ny impedance mampiavaka azy, ary ny marina dia ao anatin’ny 5%.

What is impedance control how to perform impedance control on PCB

Tsipika

Ny tsipika kofehy dia kofehy varahina eo afovoan’ny diélectrique eo anelanelan’ny fiaramanidina roa. 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:

Mba hifehezana ny impedance PCB tsara dia ilaina ny mahatakatra ny firafitry ny PCB:

Matetika ilay antsointsika hoe takelaka multilayer dia vita amin’ny takelaka fototra sy ny taratasy vita amin’ny semi-solidified izay mifono laminated. Ny takelaka fototra dia matevina matevina, voafaritra tsara, takelaka varahina roa mofo, izay akora fototra amin’ny tabilao vita pirinty. 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.

Matetika ny sosona diélectrique roa ivelany misy multilayer dia sosona mando, ary ny sosona varahina vita amin’ny varahina misaraka dia ampiasaina eo ivelan’ireo sosona roa ireo ho toy ny varahina varahina ivelany. Ny famaritana matevina amin’ny foil varahina ivelany sy foil varahina anatiny dia amin’ny ankapobeny 0.5oz, 1OZ, 2OZ (1OZ dia manodidina ny 35um na 1.4mil), fa aorian’ny andiam-pitsaboana eto an-tany dia hitombo matetika ny hatevin’ny varahina varahina ivelany 1OZ. Ny foil varahina anatiny dia ny varahina manarona amin’ny lafiny roa amin’ny lovia fototra. Ny hatevin’ny farany dia tsy mitovy kely amin’ny hatevin’ny tany am-boalohany, saingy amin’ny ankapobeny dia mihena amina um maromaro izy noho ny fametahana azy.

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.

Rehefa vita ny hatevin’ny takelaka vita pirinty, amin’ny lafiny iray, dia ilaina ny fisafidianana ireo masontsivana ara-materialy, etsy ankilany, ny hatevin’ny farany ravina semi-sitrana dia ho kely kokoa noho ny hatevin’ny voalohany. Ireto manaraka ireto dia rafitra laminated 6-layer mahazatra:

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:

Varavarana varahina ambonin’ny:

There are three thicknesses of copper foil that can be used: 12um, 18um and 35um. Ny hatevin’ny farany aorian’ny famaranana dia manodidina ny 44um, 50um ary 67um.

Takelaka lehibe: S1141A, FR-4 mahazatra, lovia varahina roa misy mofo ampiasaina matetika. Ny famaritana tsy azo atao dia azo faritana amin’ny alàlan’ny fifandraisany amin’ny mpanamboatra.

Semi-cured tablet:

Ny famaritana (ny hatevin’ny tany am-boalohany) dia 7628 (0.185mm), 2116 (0.105mm), 1080 (0.075mm), 3313 (0.095mm). Ny tena hateviny aorian’ny fanerena dia matetika manodidina ny 10-15um latsaky ny sanda voalohany. Ny takelaka faran’izay manasitrana 3 farafahakeliny dia azo ampiasaina amin’ny sosona fampidirana azy ihany, ary ny hatevin’ny takelaka semi-sitrana 3 dia tsy hitovy, farafahakeliny takelaka sitrana iray azo ampiasaina, fa ny mpanamboatra sasany dia tsy maintsy mampiasa roa farafaharatsiny . Raha tsy ampy ny hatevin’ny sombin-tapa-sitrana, dia azo soratana ny varahina amin’ny lafiny roa amin’ny lovia fototra, ary avy eo azo ampifamatotra amin’ny lafiny roa ny sombin-tsolika, mba hisy tratra.

Fanoherana welding welding:

Ny hatevin’ny sosona fanoherana solder amin’ny foil varahina dia C2≈8-10um. Ny hatevin’ny solder resist resist amin’ny ambonin’ny tsy misy foil varahina dia C1, izay miovaova arakaraka ny hatevin’ny varahina eo amboniny. Rehefa 45um ny hatevin’ny varahina ambonin’ny C1≈13-15um, ary rehefa 70um ny hatevin’ny varahina dia C1≈17-18um.

Fizarana mamakivaky:

Heverinay fa ny tsipika fiampitan’ny tariby dia mahitsizoro, fa tena trapezoid izany. Raiso ho ohatra ny sosona TOP, rehefa 1OZ ny hatevin’ny varahina varahina, dia ny 1MIL fohy kokoa noho ny sisiny ambany ambany. Ohatra, raha 5MIL ny sakan’ny tsipika, dia manodidina ny 4MIL ny lafiny ambony sy ambany ary 5MIL ny lafiny ambany sy ny farany ambany. Ny fahasamihafana misy eo amin’ny sisiny ambony sy ambany dia misy ifandraisany amin’ny hatevin’ny varahina. Ity tabilao manaraka ity dia mampiseho ny fifandraisana misy eo amin’ny trapezoid ambony sy ambany amin’ny toe-javatra samihafa.

What is impedance control how to perform impedance control on PCB

Fahazoan-dàlana: ny fahazoan-dàlana amin’ny ravina semi-cured dia mifandraika amin’ny hateviny. Ity tabilao manaraka ity dia mampiseho ny hateviny sy ny fari-pahalalana azo avy amin’ny karazana lambam-panasitranana semi-cured:

What is impedance control how to perform impedance control on PCB

Ny tsy fetezan’ny diélectrique an’ny takelaka dia mifandraika amin’ny fitaovana resina ampiasaina. Ny tsy fetezan’ny diélectrique an’ny takelaka FR4 dia 4.2 – 4.7, ary mihena miaraka amin’ny fitomboan’ny fahita matetika.

Antony fatiantoka diélectrique: ireo fitaovana diélectrika eo ambanin’ny asan’ny elatra elektrika mifandimby, noho ny hafanana sy ny fanjifana angovo dia antsoina hoe fatiantoka diélectrique, izay matetika no ambaran’ny entona very diélectrika Tan δ. Ny sanda mahazatra ho an’ny S1141A dia 0.015.

Ny sakan’ny tsipika farafahakeliny sy ny elanelan’ny tsipika mba hiantohana ny milina: 4mil / 4mil.

Fampidirana fitaovana fanisana impedance:

Rehefa fantatsika ny firafitry ny tabilao multilayer ary mahafehy ireo masontsivana ilaina dia afaka manisa ny impedance amin’ny alàlan’ny rindrambaiko EDA isika. Azonao atao ny mampiasa Allegro hanaovana an’io, saingy mamporisika an’i Polar SI9000 aho, izay fitaovana tsara hikajiana ny impedance mampiavaka azy ary ampiasain’ny orinasa PCB maro izao.

Rehefa manisa ny impedance mampiavaka ny mari-pamantarana anatiny misy ny tsipika miavaka sy ny tsipika tokana tokana dia tsy hitanao afa-tsy ny fahasamihafana kely eo amin’ny Polar SI9000 sy Allegro noho ny antsipiriany sasantsasany, toy ny endrika ny ampahan’ny hazo fijaliana. Na izany aza, raha te hikajiana ny impedance mampiavaka ny fambara Surface, dia manoro hevitra anao aho ny hisafidiananao ny maodely mifono fa tsy ny maodely Surface, satria ny maodely toy izany dia mihevitra ny fisian’ny sosona fanoherana solder, ka ho marina kokoa ny valiny. Ity manaraka ity dia pikantsary ampahany amin’ny tsimok’aretin’ny fahasamihafana an-tampony kajy amin’ny Polar SI9000 mandinika ny sosona fanoherana solder:

What is impedance control how to perform impedance control on PCB

Satria tsy voafehy mora ny hatevin’ny sosona fanoherana solder, dia azo atao koa ny mampiasa fomba manakaiky, araka ny atolotry ny mpanamboatra birao: esory ny sandany manokana amin’ny fikajiana modely Surface. Soso-kevitra ny mihena 8 ohm ny impedance samihafa ary ny impedance tokana dia avela 2 ohm.

Fepetra takiana PCB tsy mitovy amin’ny tariby

(1) Fantaro ny maodelin’ny tariby, ny masontsivana ary ny kajy impedance. Misy karazany roa ny maody fihasamihafana amin’ny fivezivezena amin’ny tsipika: maodely fahasamihafana eo amin’ny tsipika mikrostrip ivelany ary ny fomba fitoviana tsipika sosona anatiny. Ny imppedance dia azo isaina amin’ny alàlan’ny rindrambaiko fanaovana kajy impedance mifandraika (toy ny POLAR-SI9000) na ny pika fanisana impedance amin’ny alàlan’ny fametrahana parameter mety.

(2) Tsipika isometrika mitovy. Fantaro ny sakan’ny tsipika sy ny elanelam-potoana, ary araho tsara ny sakan’ny tsipika nisaina sy ny elanelana rehefa mandeha. Ny elanelana misy eo amin’ny tsipika roa dia tsy maintsy mijanona tsy miova, izany hoe hitazomana hatrany. 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. Amin’ny ankapobeny dia andramo ny tsy fampiasana ny mari-pamantarana tsy fitoviana eo amin’ny sosona, izany hoe satria amin’ny fanodinana PCB tena izy ao anaty ny dingana, noho ny fahamendrehan’ny laminated laminated dia ambany kokoa noho ny teo anelanelan’ny marimaritra iraisana, sy ny fizotry ny fahaverezan’ny diélectrique laminated, Tsy afaka manome antoka ny elanelam-potoana misy elanelam-potoana dia mitovy amin’ny hatevin’ny diélectric interlayer, dia hiteraka ny fahasamihafana eo amin’ny sosona ny fahasamihafan’ny fiovan’ny impedance. Manolo-kevitra ny hampiasa ny fahasamihafana ao anatin’ny sosona mitovy betsaka araka izay tratra.