Otu esi ejikwa PCB ihe mgbochi?

Without impedance control, considerable signal reflection and distortion will be caused, resulting in design failure. Ihe mgbaàmà ndị a na-ahụkarị, dị ka bọs PCI, bọs PCI-E, USB, Ethernet, ebe nchekwa DDR, akara LVDS, wdg, ha niile chọrọ njikwa impedance. Ekwesịrị ka emezu njikwa impedance site na imebe PCB, nke na -ebutekwa ihe ndị dị elu maka teknụzụ bọọdụ PCB. Mgbe gị na ụlọ ọrụ PCB kwurịtasịrị yana yana iji sọftụwia EDA, a na -achịkwa impedance nke wiring dị ka ihe achọrọ si dị.

Enwere ike gbakọọ ụzọ wiring dị iche iche iji nweta uru impedance kwekọrọ.

Ahịrị Microstrip

• Ọ nwere eriri waya nwere ụgbọ elu ala na dielectric n’etiti. Ọ bụrụ na ọnụọgụ dielectric, obosara ahịrị, na anya ya site na ụgbọ elu ala, enwere ike ijikwa ya, mgbe ahụ njiri mara ya nwere ike ịchịkwa, na izi ezi ga -adị n’ime ± 5%.

Kedu ihe njikwa impedance ka esi eme njikwa impedance na PCB

Warara

Ahịrị rịbọn bụ eriri ọla kọpa n’etiti etiti ọkụ n’etiti ụgbọ elu abụọ na -eduzi. Ọ bụrụ na ọkpụrụkpụ na obosara nke ahịrị, a ga -ejikwa njikwa dielectric nke onye na -ajụ ase, na anya dị n’etiti ụgbọ elu ala nke akwa abụọ, njiri mara nke ahịrị nwere ike ịchịkwa, yana izi ezi dị n’ime 10%.

Kedu ihe njikwa impedance ka esi eme njikwa impedance na PCB

The structure of multi-layer board:

Iji chịkwaa impedance PCB nke ọma, ọ dị mkpa ịghọta usoro nke PCB:

Na-abụkarị ihe anyị na-akpọ bọọdụ multilayer bụ isi efere na mpempe akwụkwọ siri ike nke ejikọtara ọnụ. Ogwe isi bụ ihe siri ike, ọkpụrụkpụ, achịcha ọla kọpa abụọ, nke bụ ihe bụ isi nke bọọdụ e biri ebi. 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.

Usually the outermost two dielectric layers of a multilayer are wetted layers, and separate copper foil layers are used on the outside of these two layers as the outer copper foil. Nkọwapụta ọkpụrụkpụ izizi nke foil ọla kọpa na foil ọla kọpa bụ 0.5oz, 1OZ, 2OZ (1OZ bụ ihe dịka 35um ma ọ bụ 1.4mil), mana mgbe usoro ọgwụgwọ dị n’elu, ọkpụrụkpụ ikpeazụ nke foil ọla kọpa ga -abawanye n’ogologo 1ỌZ. Ihe mkpuchi ọla kọpa dị n’ime bụ mkpuchi ọla kọpa n’akụkụ abụọ nke isi efere. Ọkpụrụkpụ ikpeazụ dịtụ ntakịrị na ọkpụrụkpụ mbụ, mana ọtụtụ um na -ebelatakarị ya n’ihi etching.

Mpekere mpụta nke bọọdụ multilayer bụ oyi na -eguzogide ịgbado ọkụ, nke bụ ihe anyị na -ekwukarị “mmanụ na -acha akwụkwọ ndụ”, n’ezie, ọ nwekwara ike bụrụ odo ma ọ bụ agba ndị ọzọ. 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. Ndị na-esonụ bụ ụdịdị akwa akwa nwere akwa 6:

Kedu ihe njikwa impedance ka esi eme njikwa impedance na 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:

N’elu ọla kọpa foil:

There are three thicknesses of copper foil that can be used: 12um, 18um and 35um. Ọkpụkpụ ikpeazụ mgbe emechara bụ ihe dịka 44um, 50um na 67um.

Okpokoro isi: S1141A, ọkọlọtọ FR-4, a na-ejikarị efere ọla kọpa abụọ eme achịcha. Enwere ike ikpebi nkọwapụta nhọrọ site na ịkpọtụrụ onye nrụpụta.

Semi-cured tablet:

Nkọwa (ọkpụrụkpụ mbụ) bụ 7628 (0.185mm), 2116 (0.105mm), 1080 (0.075mm), 3313 (0.095mm). Ọkpụrụkpụ n’ezie mgbe ịpị na-abụkarị ihe dị ka 10-15um erughị uru izizi. Enwere ike iji mbadamba mbadamba atọ gwọrọ nke ọma maka otu mkpuchi infiltration, na ọkpụrụkpụ nke mbadamba 3 gwọrọ nwere ike ọ gaghị abụ otu, enwere ike iji otu mbadamba ọkara gwọrọ, mana ụfọdụ ndị nrụpụta ga-eji opekata mpe abụọ. . Ọ bụrụ na ọkpụrụkpụ nke akụkụ ahụ gwọrọ nke ọma ezughi, enwere ike wepu foil ọla kọpa n’akụkụ abụọ nke isi efere, wee nwee ike kechie akụkụ ahụ gwọrọ ya n’akụkụ abụọ, nke mere na akwa mkpuchi infiltration buru ibu nwere ike ịbụ nweta.

Nguzogide ịgbado ọkụ oyi akwa:

Ọkpụrụkpụ nke onye na-ere ihe na-eguzogide oyi akwa na foil ọla bụ C2≈8-10um. Ọkpụrụkpụ nke solder na -eguzogide oyi akwa n’elu na -enweghị foil ọla bụ C1, nke na -agbanwe na ọkpụrụkpụ ọla kọpa n’elu. Mgbe ọkpụrụkpụ ọla kọpa n’elu bụ 45um, C1≈13-15um, na mgbe ọkpụrụkpụ ọla kọpa n’elu 70um, C1≈17-18um.

Akụkụ traverse:

Anyị ga -eche na akụkụ obe nke waya bụ akụkụ anọ, mana ọ bụ n’ezie trapezoid. N’iji akwa TOP dị ka ọmụmaatụ, mgbe ọkpụrụkpụ nke foil ọla kọpa bụ 1OZ, ọnụ elu ala trapezoid dị 1MIL dị mkpụmkpụ karịa ala ala. Dịka ọmụmaatụ, ọ bụrụ na obosara ahịrị bụ 5MIL, mgbe akụkụ elu na ala dị ihe dịka 4MIL na ala na ala dị ihe dị ka 5MIL. Ọdịiche dị n’etiti ọnụ elu na ala na -emetụta ọkpụrụkpụ ọla kọpa. Tebụl na -esote na -egosi njikọ dị n’etiti elu na ala nke trapezoid n’okpuru ọnọdụ dị iche iche.

Kedu ihe njikwa impedance ka esi eme njikwa impedance na PCB

Ikikere: Ikike nke mpempe akwụkwọ a gwọrọ ọkara nwere ọkpụrụkpụ. Tebụl na-esote na-egosi oke ọkpụrụkpụ na ikike ikike nke ụdị mpempe akwụkwọ gwọchara ọkara:

Kedu ihe njikwa impedance ka esi eme njikwa impedance na PCB

Ọnụnọ nke dielectric nke efere ahụ metụtara ihe ejiri resin mee. Ogwe dielectric nke efere FR4 bụ 4.2 – 4.7, na -agbada site na mmụba nke ugboro.

Ihe na -akpata ọnwụ dielectric: ihe ndị a na -akpọ dielectric n’okpuru ọrụ nke ịgbanye ọkụ eletrik ọzọ, n’ihi ọkụ na oriri ike ka a na -akpọ ọnwụ dielectric, nke Tan δ na -egosipụtakarị. Ụdị uru maka S1141A bụ 0.015.

Obere ahịrị ahịrị na ahịrị ahịrị iji hụ na igwe na -arụ ọrụ: 4mil/4mil.

Okwu mmeghe nke impedance:

Mgbe anyị ghọtara usoro nke bọọdụ multilayer ma mara oke achọrọ, anyị nwere ike gbakọọ impedance site na ngwanrọ EDA. Ị nwere ike iji Allegro mee nke a, mana m na -akwado Polar SI9000, nke bụ ezigbo ngwa maka ịgbakọ impedance njirimara nke ọtụtụ ụlọ nrụpụta PCB na -eji ugbu a.

Mgbe ị na -agbakọ njiri mara njiri mara nke akara nke dị n’ime ma ahịrị dị iche na otu ahịrị ọnụ, ị ga -ahụ naanị ntakịrị ọdịiche n’etiti Polar SI9000 na Allegro n’ihi ụfọdụ nkọwa, dị ka ọdịdị nke akụkụ obe. Agbanyeghị, ọ bụrụ na ọ ga -agbakọ njiri mara njiri mara nke akara dị n’elu, ana m atụ aro ka ị họrọ ihe mkpuchi kpuchie kama ụdị elu ahụ, n’ihi na ụdị ndị a na -eburu n’uche ịdị adị nke mkpuchi mkpuchi, yabụ nsonaazụ ya ga -adị mma karịa. Ihe na -esonụ bụ nseta ihuenyo ele mmadụ anya n’ihu nke impedance ahịrị dị iche iche nke agbakọtara na Polar SI9000 na -atụle akwa oyi akwa:

Kedu ihe njikwa impedance ka esi eme njikwa impedance na PCB

Ebe ọ bụ na ọkpụrụkpụ nke oyi akwa na -anaghị ejikwa ngwa ngwa ejikwa ya, enwere ike iji usoro dị nso, dị ka onye nrụpụta bọọdụ tụrụ aro ya: wepu otu uru site na ngụkọ ihe nlereanya dị n’elu. A na-atụ aro ka impedance dị iche belata mwepu 8 ohms na impedance nke nwere njedebe ga-ewepu 2 ohms.

Ihe PCB dị iche iche chọrọ maka wiring

(1) Kpebie ọnọdụ wiring, paramita na mgbako impedance. E nwere ụdị ụzọ abụọ dị iche iche maka ịgagharị ahịrị: ọnọdụ ọdịiche microstrip dị na mpụga na ọnọdụ ọdịiche eriri warara dị n’ime. Enwere ike ịgbakọ impedance site na ngụkọta ngụkọta ngụkọta ngwanrọ metụtara (dị ka POLAR-SI9000) ma ọ bụ usoro ngụkọ ngọngọ site na ntọala oke ezi uche.

(2) ahịrị isometric yiri. Kpebie obosara na ahịrị ahịrị, wee na -esochi obosara ahịrị na oghere gbakọrọ agbazi mgbe ị na -agagharị. Oghere dị n’etiti ahịrị abụọ ga -anọgide na -agbanweghi agbanwe, ya bụ, ka ịha nhata. 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. Gbalịa zere iji akara mgbaàmà dị iche n’etiti akwa, ya bụ n’ihi na nhazi PCB n’ezie na usoro a, n’ihi ịhazigharị nhazi ziri ezi dị ala karịa nke enyere n’etiti nkenke etching, yana na usoro nke mfu ọkụ dielectric, enweghị ike ikwe nkwa ịdị iche ahịrị ahịrị dị ka ọkpụrụkpụ nke dielectric interlayer, ga -ebute ọdịiche dị n’etiti akwa nke ọdịiche nke mgbanwe impedance. A na -atụ aro ka ị jiri ọdịiche dị n’ime otu oyi akwa ka o kwere mee.