Me pehea te whakahaere PCB impedance?

Without impedance control, considerable signal reflection and distortion will be caused, resulting in design failure. Ko nga tohu noa, penei i te pahi PCI, pahi PCI-E, USB, Ethernet, maumahara DDR, tohu LVDS, me era atu, me mana katoa te aukati. Ko te tikanga mo te ngoikore me tino kitea ma te hoahoa PCB, e tuku ana i nga whakaritenga teitei ake mo te hangarau poari PCB. I muri i te korero ki te wheketere PCB me te hono ki te whakamahi i te raupaparorohiko EDA, ko te aukati o te waea hiko e whakahaerehia ana kia rite ki nga whakaritenga o te pono tohu.

Ka taea te tatau i nga tikanga waea rerekee kia whiwhi i te uara haangai e hono ana.

Microstrip lines

• Kei kona te aho waea me te papa rererangi whenua me te dielectric kei waenganui. Mena ka pumau tonu te hiko, te whanui o te raina, me tona tawhiti mai i te papa rererangi ka taea te whakahaere, ka taea te whakahaere i tana aarai, a ko te tika kei roto i te ± 5%.

What is impedance control how to perform impedance control on PCB

Raina

Ko te raina rīpene he taura parahi i waenga o te dielectric i waenga i nga rererangi whakahaere e rua. 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:

Kia pai ai te whakahaere i te PCB impedance, me maarama ki te hanga o te PCB:

Te nuinga o ta maatau e kiia nei ko te poari multilayer he papa paraharaha me te pepa haangai whakakotahi tetahi ki tetahi. Ko te poari matua he pakeke, he tino matotoru, e rua nga pereti parahi paraoa, he mea nui na te papa taarua. 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.

I te nuinga o nga wa e rua nga waahanga dielectric o te multilayer he papanga maroke, a ka whakamahia nga papa parahi parahi wehe i waho o enei papa e rua hei peera parahi o waho. Ko te whakatakotoranga matotoru taketake o te konumohe parahi o waho me te konumohe parahi o roto, ko te tikanga 0.5oz, 1OZ, 2OZ (Ko te 1OZ e pa ana ki te 35 me te 1.4mil ranei), engari i muri i te waahanga o te maimoatanga o te mata, ko te matotoru whakamutunga o te parahi parahi o waho ka nui ake 1OZ. Ko te papa parahi o roto ko te parahi e kapi ana i nga taha e rua o te pereti matua. Ko te matotoru whakamutunga he rereke te rereketanga mai i te matotoru taketake, engari ko te nuinga ka whakaitihia e te maha um na te tuhi.

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.

Ka hangaia ana te matotoru o te papa peita, i tetahi taha, ka hiahiatia he kowhiringa tika mo nga taapiri rauemi, i tetahi atu ringa, ko te matotoru whakamutunga o te pepa haurua-whakaora ka iti ake i te matotoru tuatahi. Ko te mea e whai ake nei ko te hanga 6-apa he mea whakarewaina:

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:

Te papa parahi parahi:

There are three thicknesses of copper foil that can be used: 12um, 18um and 35um. Ko te matotoru whakamutunga i muri i te otinga ko te 44um, 50um me te 67um.

Te pereti matua: S1141A, te paerewa FR-4, e rua nga pereti parahi paraoa e whakamahia ana. Ko nga whakaritenga taapiri ka taea te whakatau ma te whakapiri atu ki te kaihanga.

Semi-cured tablet:

Nga whakaritenga (matotoru taketake) 7628 (0.185mm), 2116 (0.105mm), 1080 (0.075mm), 3313 (0.095mm). Ko te matotoru tuturu i muri i te peehi i te nuinga o te waa 10-15um iti iho i te uara taketake. Ko te rahinga o te 3 papa whakaora-rongoa ka taea te whakamahi mo te paparanga whakauru ano, a ko te matotoru o te 3 papa whakaora kia kore e rite, kia kotahi pea te haurua papa whakaora ka taea te whakamahi, engari me whakamahi e etahi kaihanga kia rua pea . Mena kaore i te ranea te matotoru o te waahanga haumanu-whakaora, ka taea te tuhi i te pepa parahi i nga taha e rua o te pereti matua, katahi ka taea te hono i te waahanga haurua-whakaora i nga taha e rua, kia taea ai te hono kikii tutuki.

Paparanga fehokotaki’anga ātete:

Ko te matotoru o te paparanga whakahee i te papa parahi ko C2≈8-10um. Ko te matotoru o te rewa o te paparanga aukati i runga i te mata o te kore parahi parahi ko C1, ka rereke me te matotoru o te parahi i runga. A, no te matotoru o te parahi i te mata o te 45um, C1≈13-15um, ana ko te matotoru o te parahi i te mata 70um, C1≈17-18um.

Wahanga huringa:

Ki ta maatau ko te waahanga whakawhiti o te waea he tapawhawhara, engari he trapezoid tena. Ko te tango i te paparanga TOP hei tauira, ina ko te matotoru o te parahi parahi, ko te 1OZ, ko te taha o raro o te trapezoid he 1MIL poto atu i te taha o raro o raro. Hei tauira, mena ko te whanui raina he 5MIL, na ko nga taha o runga me o raro e pa ana ki te 4MIL a ko nga taha o raro me o raro e pa ana ki te 5MIL. Ko te rereketanga i waenga o runga me o raro e pa ana ki te matotoru parahi. Ko te ripanga e whai ake nei e whakaatu ana i te hononga i waenga o runga me o raro o te trapezoid i raro i nga ahuatanga rereke.

What is impedance control how to perform impedance control on PCB

Whakaaetanga: Ko te whakaaetanga o nga pepa haurua-whakaora e pa ana ki te matotoru. Ko te ripanga e whai ake nei e whakaatu ana i te matotoru me nga waahanga whakaaetanga o nga momo pepa reanga wha-rongoa:

What is impedance control how to perform impedance control on PCB

Ko te pumau dielectric o te pereti e pa ana ki nga taonga kapia e whakamahia ana. Ko te pumau dielectric o te pereti FR4 he 4.2 – 4.7, ka heke me te piki haere o te auau.

Tauwehenga ngaronga Dielectric: ko nga rauemi hiko i raro i nga mahi o te huri hiko, na te wera me te kohi kaha e kiia ana ko te ngarara hiko, i te nuinga o te waa e kiia ana na te ngarara ngarara kua mate Tan δ. Ko te uara angamaheni mo te S1141A ko te 0.015.

Te whanui raina iti me te mokowhiti raina kia pai ai te miihini: 4mil / 4mil.

Whakataki taputapu taapiri Impedance:

Ka mohio ana maatau ki te hanganga o te papa multilayer me te mohio ki nga waahanga e hiahiatia ana, ka taea e taatau te tatau i te aukati ma te raupaparorohiko EDA. Ka taea e koe te whakamahi i a Allegro ki te mahi i tenei, engari ko taku kupu ki a Polar SI9000, he taputapu pai mo te tatau i nga aukati motuhake ka whakamahia e nga wheketere PCB maha.

Ka tatau ana koe i te koretake o te tohu o roto o te raarangi rerekee me te raina kati kotahi, ka kitea he rereketanga iti i waenga i te Polar SI9000 me te Allegro na etahi korero, penei i te ahua o te waahanga whiti o te waea. Heoi, mena kei te tatau i te koretake o te tohu Mata, e mea atu ana ahau ko koe me kowhiri i te tauira Uwhi hei utu mo te tauira Mata, na te mea ko nga tauira e whai whakaaro ana ki te reanga o te reanga parenga, no reira ka tika ake nga hua. Ko te mea e whai ake nei ko te Whakaahuamata waahanga o te raina rerekee raarangi mataaahia me te Polar SI9000 e whakaaro ana ki te paparanga aukati rewa:

What is impedance control how to perform impedance control on PCB

I te mea kaore i te ngawari te whakahaere i te matotoru o te reanga rewa, ka taea hoki te whakamahi i tetahi huarahi whakatau tata, me te taunaki a te kaihanga poari: tangohia tetahi uara motuhake mai i te taatau tauira Mata. E taunaki ana ko te rereketanga rerekee kia heke te 8 ohm me te whakaheke-kia-haurua kia heke te 2 ohm.

Nga whakaritenga PCB rerekee mo nga waea waea

(1) Whakatauhia te aratau waea waea, nga taapiri me te taatau impedance. E rua nga momo tuumomo rerekee mo te raina raina: aratau rerekee raina microstrip paparanga o waho me te aratau rerekee raina reini peera o roto. Ka taea te tatau i te ngoikoretanga ma te raupaparorohiko tatauranga tuturu (penei i te POLAR-SI9000), te taatai ​​taatai ​​raupaparorohiko ranei ma te tautuhinga paranga whaitake.

(2) Raina initerite whakarara. Whakatauhia te whanui raina me te mokowhiti, me tino whai i te whanui raina tatau me te mokowhiti i te waa e huri ana. Ko te mokowhiti i waenga i nga raina e rua me noho tonu kaore i whakarereke, ara kia noho taurite. 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. Ko te tikanga ngana ki te karo i te whakamahi i te tohu rereke i waenga i nga paparanga, na te mea ko te tukatuka pono o te PCB i roto i te waahanga, na te tika o te raina whakarakei o te raina he iti iho i te waa e waatea ana i waenga i te kiko o te riu, me te mahinga o te ngarara hiko i whakamutua. kaore e taea te kii he rereke te mokowhiti raina ki te matotoru o te dielektric interlayer, ka rereke te rereketanga i waenga i nga papa o te rereketanga rereke rereke. E taunaki ana kia whakamahia te rereketanga i roto i taua paparanga kia taea.