PCB stacking is an important factor to determine EMC performance of products. Ukuhleleka okuhle kungasebenza kakhulu ekwehliseni imisebe evela kuluphu lwe-PCB (ukukhishwa kwemodi yokuhlukanisa), nakwizintambo ezixhunywe ebhodini (ukukhishwa kwemodi ejwayelekile).

Ngakolunye uhlangothi, i-cascade embi ingakhuphula kakhulu imisebe yazo zombili lezi zinqubo. Izici ezine zibalulekile ekucatshangweni kokufakwa kwepuleti:

1. Inani lezendlalelo;

2. Inombolo nohlobo lwezendlalelo ezisetshenzisiwe (amandla kanye / noma umhlabathi);

3. Ukuhleleka noma ukulandelana kwezendlalelo;

4. Isikhathi phakathi kwezendlalelo.

Imvamisa kubhekwa kuphela inani lezendlalelo. Ezimweni eziningi, ezinye izinto ezintathu zibaluleke ngokulinganayo, kanti eyesine kwesinye isikhathi ayaziwa nakumklami we-PCB. Lapho unquma inani lezendlalelo, cabanga ngokulandelayo:

1. Ubuningi besiginali nezindleko zezintambo;

2. Frequency;

3. Ngabe umkhiqizo kufanele uhlangabezane nezidingo zokwethulwa kweClass A noma iClass B?

4. I-PCB isezindlini ezivikelekile noma ezingenazinsimbi;

5. EMC engineering expertise of the design team.

Imvamisa kubhekwa kuphela igama lokuqala. Ngempela, zonke izinto zazibalulekile futhi kufanele zicatshangelwe ngokulinganayo. Le nto yokugcina ibaluleke kakhulu futhi akufanele inganakwa uma ukwakheka okuhle kuzotholakala ngesikhathi esincane nezindleko.

Ipuleti le-multilayer lisebenzisa umhlabathi kanye / noma indiza yamandla linikeza ukwehliswa okukhulu kokukhishwa kwemisebe uma kuqhathaniswa nocwecwe olunezingqimba ezimbili. Umthetho ojwayelekile wesithupha osetshenzisiwe ukuthi ipuleti ezine-ply likhiqiza imisebe engaphansi kwe-15dB kunepuleti elinamapayipi amabili, zonke ezinye izinto ziyalingana. A board with a flat surface is much better than a board without a flat surface for the following reasons:

1. Bavumela amasiginali ukuthi ahanjiswe njengemigqa ye-microstrip (noma imigqa yeribhoni). These structures are controlled impedance transmission lines with much less radiation than the random wiring used on two-layer boards;

2. Ibhanoyi lomhlaba liyayinciphisa kakhulu impedance yomhlabathi (ngakho-ke umsindo womhlabathi).

Yize amapuleti amabili esetshenziswe ngempumelelo ezindaweni ezingavikelekile ezingama-20-25mhz, lawa macala yiwona ahlukile kunalawo asetshenziswayo. Ngaphezulu kwe-10-15mhz, amaphaneli we-multilayer kufanele ngokuvamile acatshangelwe.

There are five goals you should try to achieve when using a multilayer board. Kunjalo:

1. Isendlalelo sesiginali kufanele ngaso sonke isikhathi siseduze nendiza;

2. Isendlalelo sesiginali kufanele sihlanganiswe ngokuqinile (eduze) endizeni yaso eseduze;

3, the power plane and the ground plane should be closely combined;

4, isignali yesivinini esiphezulu kufanele ingcwatshwe kulayini ophakathi kwezindiza ezimbili, indiza ingadlala indima yokuvikela, futhi ingavimbela imisebe yomugqa oprintwe ngesivinini esikhulu;

5. Multiple grounding planes have many advantages because they will reduce the grounding (reference plane) impedance of the board and reduce common-mode radiation.

Ngokuvamile, sibhekene nokukhetha phakathi kokuhlangana kwesiginali / indiza (Inhloso 2) namandla okuhlangana kwezindiza / komhlaba (inhloso 3). Ngamasu ajwayelekile okwakhiwa kwe-PCB, amandla weplate ayiplati phakathi kokuphakelwa kwamandla kagesi kanye nendiza yomhlabathi ayanele ukunikeza ukuhluma okwanele ngaphansi kwama-500 MHz.

Ngakho-ke, ukuhlangana kabusha kufanele kubhekwe ngezinye izindlela, futhi kufanele ngokuvamile sikhethe ukuhlangana okuqinile phakathi kwesiginali nendiza ebuyayo yamanje. Izinzuzo zokuhlangana okuqinile phakathi kwesendlalelo sesiginali kanye nendiza ebuyayo yamanje zizodlula ubunzima obudalwe ukulahleka okuncane kwamandla phakathi kwezindiza.

Eight layers is the minimum number of layers that can be used to achieve all five of these goals. Eminye yalezi zinhloso kuzofanele ibekwe engozini emabhodini amane – nakuma-ply six board. Ngaphansi kwale mibandela, kufanele unqume ukuthi yimiphi imigomo ebaluleke kakhulu kumklamo osusondele.

Isigaba esingenhla akufanele sihunyushwe ngokuthi kusho ukuthi awukwazi ukwenza ukwakheka okuhle kwe-EMC ebhodini elinezinhlangothi ezine noma eziyisithupha, ngangokunokwenzeka. It just shows that not all objectives can be achieved at once and that some kind of compromise is required.

Since all desired EMC goals can be achieved with eight layers, there is no reason to use more than eight layers except to accommodate additional signal routing layers.

From a mechanical point of view, another ideal goal is to make the cross-section of the PCB board symmetrical (or balanced) to prevent warping.

Isibonelo, ebhodini lezingqimba eziyisishiyagalombili, uma ungqimba lwesibili luyindiza, khona-ke ungqimba lwesikhombisa kufanele futhi lube yindiza.

Ngakho-ke, konke ukucushwa okwethulwe lapha kusebenzisa izakhiwo ezilinganayo noma ezilinganiselayo. If asymmetrical or unbalanced structures are allowed, it is possible to build other cascading configurations.

Four layer board

Isakhiwo sepuleti esinezingqimba ezine esivame kakhulu siboniswa kuMdwebo 1 (indiza yamandla nendiza yaphansi iyashintshana). It consists of four evenly spaced layers with an internal power plane and a ground plane. These two external wiring layers usually have orthogonal wiring directions.

Yize lokhu kwakhiwa kungcono kakhulu kunamaphaneli aphindwe kabili, kunezici ezithile ezingathandeki kangako.

Ohlwini lwamatshegethi kuNgxenye 1, lesi sitaki sanelisa kuphela ithagethi (1). Uma izingqimba zihlukaniswe ngokulinganayo, kukhona igebe elikhulu phakathi kwesendlalelo sesiginali nendiza ebuyayo yamanje. Kukhona negebe elikhulu phakathi kwendiza yamandla nendiza yaphansi.

Ebhodini elinama-ply amane, asikwazi ukulungisa kokubili ukukhubazeka ngasikhathi sinye, ngakho-ke kufanele sinqume ukuthi yikuphi okubaluleke kakhulu kithi.

Njengoba kushiwo ngaphambili, amandla we-interlayer phakathi kwamandla kagesi aseduze kanye nendiza yasemhlabathini ayanele ukunikeza ukuhluma okwanele kusetshenziswa izindlela ezijwayelekile zokukhiqiza ze-PCB.

Ukudilizwa kufanele kuphathwe ngezinye izindlela, futhi kufanele sikhethe ukuhlangana okuqinile phakathi kwesiginali nendiza ebuyayo yamanje. The advantages of tight coupling between the signal layer and the current return plane will outweigh the disadvantages of a slight loss of interlayer capacitance.

Ngakho-ke, indlela elula yokwenza ngcono ukusebenza kwe-EMC kwepuleti elinezingqimba ezine ukuletha ungqimba lwesiginali eduze kwendiza ngangokunokwenzeka. 10mil), futhi isebenzisa umnyombo omkhulu we-dielectric phakathi komthombo wamandla nendiza yomhlaba (> 40mil), njengoba kukhonjisiwe kuMdwebo 2.

Lokhu kunezinzuzo ezintathu nezinkinga ezimbalwa. Indawo yeluphu yesiginali incane, ngakho-ke imisebe yemodi yokuhluka okuncane iyenziwa. For the case of a 5mil interval between the wiring layer and the plane layer, a loop radiation reduction of 10dB or more can be achieved relative to an equally spaced stacked structure.

Okwesibili, ukuhlanganiswa okuqinile kwentambo yesiginali emhlabathini kunciphisa i-planar impedance (inductance), ngaleyo ndlela kuncishiswe imisebe ejwayelekile yemodi yekhebuli exhunywe ebhodini.

Okwesithathu, ukuhlanganiswa okuqinile kwentambo endizeni kuzonciphisa i-crosstalk phakathi kwentambo. For fixed cable spacing, crosstalk is proportional to the square of cable height. Le ngenye yezindlela ezilula, ezingabizi kakhulu, futhi ezinganakwa kakhulu zokwehlisa imisebe evela kwi-PCB enezingqimba ezine.

Ngalesi sakhiwo se-cascade, sanelisa zombili izinhloso (1) no (2).

Yimaphi amanye amathuba akhona wesakhiwo esinamaminerali amane? Singasebenzisa okuncane kwesakhiwo esingajwayelekile, okungukuthi ukushintsha ungqimba lwesiginali kanye nongqimba lwendiza kuMfanekiso 2 ukukhiqiza i-cascade ekhonjiswe kuMdwebo 3A.

Inzuzo enkulu yalokhu kuklanywa ukuthi indiza yangaphandle ihlinzeka ngokuvikela ukuhanjiswa kwesiginali kungqimba lwangaphakathi. Okubi ukuthi indiza yasemhlabeni ingahle isikwe kakhulu ngamaphakethe wezinto eziphakeme kakhulu ku-PCB. Lokhu kungancishiswa ngezinga elithile ngokubuyisela emuva indiza, ukubeka indiza yamandla ohlangothini lwento, nokubeka indiza engaphansi kolunye uhlangothi lwebhodi.

Okwesibili, abanye abantu abathandi ukuba nendiza yamandla eveziwe, kanti okwesithathu, izingqimba zesiginali ezingcwatshiwe zikwenza kube nzima ukuphinda usebenze ibhodi. I-cascade yanelisa inhloso (1), (2), futhi yenelisa kancane inhloso (4).

Ezimbili zalezi zinkinga ezintathu zingancishiswa yi-cascade njengoba kukhonjisiwe ku-Figure 3B, lapho izindiza ezimbili zangaphandle ziyizindiza zomhlaba futhi amandla kagesi ehanjiswa endizeni yesiginali njenge-wiring.Amandla kagesi azohanjiswa raster kusetshenziswa umkhondo obanzi kusendlalelo sesiginali.

Izinzuzo ezimbili ezingeziwe zalesi sigameko yilezi:

(1) Amabhanoyi amabili aphansi ahlinzeka ngemishini engaphansi kakhulu, ngaleyo ndlela anciphise imisebe ejwayelekile yekhebula;

(2) The two ground planes can be sewn together at the periphery of the plate to seal all signal traces in a Faraday cage.

From an EMC point of view, this layering, if done well, may be the best layering of a four-layer PCB. Manje sesihlangabezane nezinhloso (1), (2), (4) kanye no (5) nebhodi elilodwa kuphela elinezingqimba ezine.

Figure 4 shows a fourth possibility, not the usual one, but one that can perform well. Lokhu kufana noMdwebo 2, kepha indiza yasemhlabeni iyasetshenziswa esikhundleni sendiza yamandla, futhi ukunikezwa kwamandla kusebenza njengomkhondo kusendlalelo sesiginali sezintambo.

Lokhu kudilika kwehlula le nkinga eshiwo ngenhla yokuphinda kusetshenziswe futhi kunikezela nangemithi ephansi ngenxa yezindiza ezimbili zomhlaba. Kodwa-ke, lezi zindiza azihlinzeki ngokuvikelwa. Lokhu kulungiselelwa kwanelisa imigomo (1), (2), kanye (5), kepha ayigculisi imigomo (3) noma (4).

Ngakho-ke, njengoba ubona kunezinketho eziningi zokubeka izingqimba ezine kunokuba ubungacabanga ekuqaleni, futhi kungenzeka ukuhlangabezana nezinhloso zethu ezinhlanu ezinama-PCBS anezingqimba ezine. Ngokombono we-EMC, ukuhlelwa kwamanani 2, 3b, no-4 konke kusebenza kahle.

6 ungqimba ibhodi

Amabhodi amaningi anezingqimba eziyisithupha aqukethe izingqimba ezine zezintambo zesiginali nezendlalelo ezimbili zezindiza, futhi amabhodi angongqimba abayisithupha ngokuvamile aphakeme kunamabhodi angongqimba abane ngombono we-EMC.

Umdwebo 5 ukhombisa isakhiwo se-cascading esingeke sisetshenziswe ebhodini lezingqimba eziyisithupha.

Lezi zindiza azihlinzeki ngokuvikela ungqimba lwesiginali, futhi izingqimba ezimbili zamasiginali (1 no-6) azikho eduze kwendiza. Leli lungiselelo lisebenza kuphela uma wonke amasiginali wemvamisa ephezulu ehanjiswa kumaleyishini 2 no-5, futhi kuphela amasiginali aphansi kakhulu, noma okungcono okwamanje, azikho izintambo zesiginali nhlobo (nje ama-pads e-solder) ahanjiswa kumaleyisi 1 no-6.

Uma isetshenzisiwe, noma yiziphi izindawo ezingasetshenziswanga phansi kuka-1 no-6 kufanele zigandaywe futhi i-viAS inamathiselwe esitezi esikhulu ezindaweni eziningi ngangokunokwenzeka.

Lokhu kulungiselelwa kwanelisa eyodwa kuphela yezinjongo zethu zoqobo (Igoli 3).

Njengoba kunezendlalelo eziyisithupha ezitholakalayo, umgomo wokuhlinzeka ngezendlalelo ezimbili ezingcwatshiwe zamasiginali asheshayo (njengoba kukhonjisiwe kuMdwebo 3) usetshenziswa kalula, njengoba kukhonjisiwe kuMdwebo 6. Lokhu kulungiswa kunikezela nangezingqimba ezimbili zomhlaba zamasiginali anejubane eliphansi.

Cishe lesi yisakhiwo esinezingqimba ezivame kakhulu eziyisithupha futhi singasebenza kakhulu ekulawuleni ukuphuma kwe-electromagnetic uma kwenziwe kahle. Lokhu kumiswa kwanelisa umgomo 1,2,4, kepha hhayi umgomo 3,5. Its main disadvantage is the separation of power plane and ground plane.

Ngenxa yalokhu kwehlukana, akunamandla amaningi okusebenzisana phakathi kwendiza yamandla nendiza yaphansi, ngakho-ke ukwakhiwa kokuqothula ngokucophelela kufanele kwenziwe ukubhekana nalesi simo. Ngemininingwane engaphezulu ngokuqedwa, bheka amathiphu wethu wezinqubo zokunciphisa.

Isakhiwo esincamathelisiwe esinezingqimba eziyisithupha esicishe sifanane sikhonjiswe kuMdwebo 7.

I-H1 imele isendlalelo somugqa ovundlile wesiginali 1, i-V1 imele ungqimba lomugqa oqondile wesiginali 1, i-H2 ne-V2 imele incazelo efanayo yesiginali 2, futhi inzuzo yalesi sakhiwo ukuthi amasiginali womzila we-orthogonal ahlala ebhekisa endizeni efanayo.

Ukuze uqonde ukuthi kungani lokhu kubalulekile, bheka isigaba ezindizeni zesiginali-to-reference kuNgxenye 6. Okubi ukuthi amasendali wesendlalelo 1 no-layer 6 awavikelwe.

Ngakho-ke, ungqimba lwesiginali kufanele lusondele kakhulu endizeni yalo eseduze futhi ungqimba lomgogodla ophakathi nendawo oshubile kufanele lusetshenziselwe ukwakha ukujiya kwepuleti okudingekayo. Isikhala esivamile sepuleti eliwu-0.060 amayintshi kungenzeka sibe ngu-0.005 “/ 0.005” / 0.040 “/ 0.005” / 0.005 “/ 0.005”. Lesi sakhiwo sanelisa imigomo 1 no 2, kepha hhayi imigomo 3, 4 noma 5.

Enye ipuleti enezingqimba eziyisithupha esebenza kahle kakhulu iboniswa kuMdwebo 8. Inikezela ngezendlalelo ezimbili zokungcwatshwa kwesiginali namandla endiza nezindiza zomhlaba ukuhlangabezana nazo zonke izinhloso ezinhlanu. Kodwa-ke, inkinga enkulu ukuthi inezingqimba ezimbili kuphela zezintambo, ngakho-ke ayisetshenziswa kaningi.

Ipuleti lesithupha – kulula ukuthola ukuhambisana okuhle kwe-electromagnet kune-plate – ungqimba ezine. Futhi sinenzuzo yezendlalelo ezine zomzila wesiginali esikhundleni sokukhawulelwa ezimbili.

Njengoba bekunjalo ngebhodi lesifunda lesendlalelo esine, i-PCB enezingqimba eziyisithupha ihlangabezane nezinhloso zethu ezinhlanu kwezinhlanu. Yonke imigomo emihlanu ingahlangatshezwa uma sizikhawulela kuzingqimba ezimbili zomzila wesiginali. Izakhiwo ezikumdwebo 6, umdwebo 7, nomdwebo 8 zonke zisebenza kahle ngombono we-EMC.