{"id":4722,"date":"2026-02-25T06:02:44","date_gmt":"2026-02-25T06:02:44","guid":{"rendered":"https:\/\/flj-pcb.com\/?p=4722"},"modified":"2026-02-25T06:02:48","modified_gmt":"2026-02-25T06:02:48","slug":"why-via-impedance-is-hard-to-control","status":"publish","type":"post","link":"https:\/\/flj-pcb.com\/cs\/why-via-impedance-is-hard-to-control\/","title":{"rendered":"Pro\u010d je obt\u00ed\u017en\u00e9 kontrolovat impedanci Via"},"content":{"rendered":"

\u0160li jsme do obchodu s deskami plo\u0161n\u00fdch spoj\u016f a zeptali se jich: \u201cDok\u00e1\u017eete kontrolovat impedanci stopy v rozmez\u00ed 10%?\u201d Odpov\u011bd\u011bli by v\u00e1m s plnou d\u016fv\u011brou: \u201c\u017d\u00e1dn\u00fd probl\u00e9m!\u201d Kdy\u017e trochu p\u0159itla\u010d\u00edte a zept\u00e1te se na 8%, mo\u017en\u00e1 se na chv\u00edli zamysl\u00ed a pak \u0159eknou: \u201cDob\u0159e (pro vnit\u0159n\u00ed vrstvy)!\u201d Pokud se pak zept\u00e1te: \u201cLze \u0159\u00eddit via na 10%?\u201d, mal\u00e1 lo\u010fka p\u0159\u00e1telstv\u00ed by se mohla... p\u0159evr\u00e1tit!<\/p>\n\n\n\n

Z\u00e1kladn\u00ed ot\u00e1zka: Impedan\u010dn\u00ed tolerance: stopy vs. vodi\u010de<\/h2>\n\n\n\n

Trasy i pr\u016fchodky propojuj\u00ed \u010dipy vys\u00edla\u010de. Pro\u010d lze tedy stopy udr\u017eet na 10%, zat\u00edmco pr\u016fchodky nikoli? V\u00edme, \u017ee ani stopy nen\u00ed snadn\u00e9 kontrolovat. Mezi faktory, kter\u00e9 ovliv\u0148uj\u00ed impedanci stop, pat\u0159\u00ed leptac\u00ed faktor, posun vrstev a drsnost povrchu. U mikrop\u00e1skov\u00fdch veden\u00ed z\u00e1le\u017e\u00ed tak\u00e9 na p\u00e1jec\u00ed masce a tlou\u0161\u0165ce m\u011bdi. P\u0159esto mnoho b\u011b\u017en\u00fdch obchod\u016f s deskami m\u016f\u017ee zaru\u010dit toleranci impedance 10% nebo dokonce 8% pro stopy. Co v\u00edm o obchodech s deskami, \u017e\u00e1dn\u00fd z nich neslibuje kontrolu impedance pr\u016fchodek v r\u00e1mci 10%. To znamen\u00e1, \u017ee u pr\u016fchodek existuje mnoho faktor\u016f, kter\u00e9 obchody s deskami nemohou kontrolovat, tak\u017ee je nemohou zaru\u010dit.<\/p>\n\n\n\n

Co zahrnuje tento \u010dl\u00e1nek<\/h2>\n\n\n\n

V tomto \u010dl\u00e1nku nejprve p\u0159edstav\u00edm dva procesy via: vrt\u00e1n\u00ed a pln\u011bn\u00ed via. Mnoho lid\u00ed v\u00ed, \u017ee na vrt\u00e1n\u00ed z\u00e1le\u017e\u00ed, ale jak moc ovliv\u0148uje tolerance vrt\u00e1n\u00ed v\u00fdkonnost via? Pokud jde o pln\u011bn\u00ed, mnoz\u00ed si mysl\u00ed, \u017ee vypln\u011bn\u00ed pr\u016fchodky prysky\u0159ic\u00ed nebo p\u00e1jec\u00ed maskou zm\u011bn\u00ed v\u00fdkon pr\u016fchodky. Tyto vlivy testujeme pomoc\u00ed simulace.<\/p>\n\n\n\n

1. Proces vrt\u00e1n\u00ed a jeho vliv na v\u00fdkonnost Via<\/h2>\n\n\n\n

Nejprve vrt\u00e1n\u00ed. \u010casto sl\u00fdch\u00e1me dva n\u00e1zvy: velikost vrt\u00e1ku a velikost hotov\u00e9ho otvoru. Pokud v souboru s deskou plo\u0161n\u00fdch spoj\u016f navrhneme otvor o velikosti 8 milimetr\u016f, mysl\u00edte si, \u017ee tov\u00e1rna pou\u017eije vrt\u00e1k o velikosti 8 milimetr\u016f? Samoz\u0159ejm\u011b \u017ee ne. Pr\u016fchodka mus\u00ed spojovat stopy na r\u016fzn\u00fdch vrstv\u00e1ch. Otvor mus\u00ed b\u00fdt pokoven tak, aby j\u00edm svisle proch\u00e1zela m\u011b\u010f. To je pokoven\u00e1 pr\u016fchoz\u00ed m\u011b\u010f. Podle normy IPC m\u00e1 tlou\u0161\u0165ka pokoven\u00e9 pr\u016fchoz\u00ed m\u011bdi stanoven\u00e9 po\u017eadavky, p\u0159ibli\u017en\u011b 18 \u00b5m a\u017e 20 \u00b5m. Tov\u00e1rny tedy zaru\u010duj\u00ed, \u017ee po pokoven\u00ed bude m\u00edt otvor velikost 8 milimetr\u016f. Tato kone\u010dn\u00e1 velikost je hotov\u00fd otvor. To znamen\u00e1, \u017ee p\u016fvodn\u00ed velikost vrt\u00e1ku mus\u00ed b\u00fdt v\u011bt\u0161\u00ed ne\u017e 8 mil. O kolik v\u011bt\u0161\u00ed? 10 mil? 12 mil? Tento rozd\u00edl ve velikosti m\u00e1 velk\u00fd vliv na v\u00fdkonnost vrt\u00e1ku.<\/p>\n\n\n\n

Podle tov\u00e1rn\u00edch pravidel pro tolerance vrt\u00e1n\u00ed se pro hotov\u00fd otvor o pr\u016fm\u011bru 0,2 mm (8 mil) pou\u017eije vrt\u00e1k o pr\u016fm\u011bru nejm\u00e9n\u011b 0,25 mm (10 mil). Pokud nezad\u00e1te p\u0159\u00edsn\u011bj\u0161\u00ed kontrolu, m\u016f\u017ee tov\u00e1rna pou\u017e\u00edt vrt\u00e1k o pr\u016fm\u011bru 0,3 mm (12 mil). Ka\u017ed\u00fd v\u00ed, \u017ee v\u011bt\u0161\u00ed vrt\u00e1k d\u011bl\u00e1 ni\u017e\u0161\u00ed impedanci. Ale o kolik ni\u017e\u0161\u00ed? To v\u00e1m mohou uk\u00e1zat na\u0161e v\u00fdsledky simulac\u00ed.<\/p>\n\n\n\n

Simulace ukazuje, \u017ee pr\u016fchodky od 0,2 mm do 0,3 mm maj\u00ed impedan\u010dn\u00ed rozd\u00edl v\u011bt\u0161\u00ed ne\u017e 5 ohm\u016f.<\/p>\n\n\n\n

Pokud se pod\u00edv\u00e1me na ztr\u00e1ty zp\u016fsoben\u00e9 via, m\u016f\u017eeme tak\u00e9 vid\u011bt jasn\u00e9 rozd\u00edly.<\/p>\n\n\n\n

U tohoto jedin\u00e9ho procesu vrt\u00e1n\u00ed m\u016f\u017ee samotn\u00e1 tolerance obr\u00e1b\u011bn\u00ed zp\u016fsobit v\u00fdkyv v\u011bt\u0161\u00ed ne\u017e 10%.<\/p>\n\n\n\n

2. Prost\u0159ednictv\u00edm n\u00e1pln\u011b: Simulace a v\u00fdsledky<\/h2>\n\n\n\n

Nyn\u00ed o pln\u011bn\u00ed. Mnoho p\u0159\u00e1tel se ptalo, zda m\u00e1 pln\u011bn\u00ed via vliv na v\u00fdkon via. Po\u0159\u00e1d jsem jim \u0159\u00edkal: \u201c\u017d\u00e1dn\u00fd vliv! \u017d\u00e1dn\u00fd vliv!\u201d V\u011b\u0159ili mi, ale st\u00e1le m\u011bli ur\u010dit\u00e9 pochybnosti. Provedl jsem tedy simulace, abych si to ov\u011b\u0159il.<\/p>\n\n\n\n

Obr\u00e1zek n\u00ed\u017ee ukazuje modely pro nevypln\u011bn\u00e9 a vypln\u011bn\u00e9 pr\u016fchodky. \u010cerven\u00e1 barva znamen\u00e1, \u017ee pr\u016fchodka je vypln\u011bna prysky\u0159ic\u00ed nebo p\u00e1jec\u00ed maskou.<\/p>\n\n\n\n

\"Return<\/figure>\n\n\n\n

Pro oba p\u0159\u00edpady jsme porovnali zp\u011btn\u00fd \u00fatlum a vlo\u017en\u00fd \u00fatlum. Pro\u010d je zde pouze jedno veden\u00ed? Proto\u017ee se veden\u00ed p\u0159ekr\u00fdvaj\u00ed. Pro\u010d se p\u0159ekr\u00fdvaj\u00ed? Proto\u017ee to nem\u00e1 \u017e\u00e1dn\u00fd vliv. V\u00fdsledky jsou stejn\u00e9.<\/p>\n\n\n\n

Teoretick\u00fd d\u016fvod: Pro\u010d na napln\u011bn\u00ed nez\u00e1le\u017e\u00ed<\/h2>\n\n\n\n

Ka\u017ed\u00fd, kdo se trochu vyzn\u00e1 v teorii vysok\u00fdch rychlost\u00ed, v\u00ed, \u017ee p\u0159i vy\u0161\u0161\u00edch rychlostech se u sign\u00e1lu projevuje skin efekt. Sign\u00e1l proud\u00ed v bl\u00edzkosti vn\u011bj\u0161\u00ed st\u011bny pr\u016fchodu. Tak\u017ee bez ohledu na to, jak\u00e9 dielektrikum je uvnit\u0159 pr\u016fchodky, elektromagnetick\u00e9 pole mezi sign\u00e1lem a referenc\u00ed se dovnit\u0159 nezavine. Pokud uvnit\u0159 nen\u00ed \u017e\u00e1dn\u00e9 pole, pak materi\u00e1l uvnit\u0159 pr\u016fchodky nebude m\u00edt \u017e\u00e1dn\u00fd \u00fa\u010dinek.<\/p>","protected":false},"excerpt":{"rendered":"

We went to a PCB shop and asked them: \u201cCan you control trace impedance to within 10%?\u201d They would answer 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went to a PCB shop and asked them: \u201cCan you control trace impedance to within 10%?\u201d They would answer […]","_links":{"self":[{"href":"https:\/\/flj-pcb.com\/cs\/wp-json\/wp\/v2\/posts\/4722","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/flj-pcb.com\/cs\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/flj-pcb.com\/cs\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/flj-pcb.com\/cs\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/flj-pcb.com\/cs\/wp-json\/wp\/v2\/comments?post=4722"}],"version-history":[{"count":1,"href":"https:\/\/flj-pcb.com\/cs\/wp-json\/wp\/v2\/posts\/4722\/revisions"}],"predecessor-version":[{"id":4725,"href":"https:\/\/flj-pcb.com\/cs\/wp-json\/wp\/v2\/posts\/4722\/revisions\/4725"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/flj-pcb.com\/cs\/wp-json\/wp\/v2\/media\/4723"}],"wp:attachment":[{"href":"https:\/\/flj-pcb.com\/cs\/wp-json\/wp\/v2\/media?parent=4722"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/flj-pcb.com\/cs\/wp-json\/wp\/v2\/categories?post=4722"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/flj-pcb.com\/cs\/wp-json\/wp\/v2\/tags?post=4722"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}