PCB stacking is an important factor to determine EMC performance of products. Kyakkyawan shimfidawa na iya zama mai tasiri sosai wajen rage radadi daga madaidaicin PCB (watsi da yanayin banbanci), da kuma daga igiyoyin da aka haɗa da jirgi (fitowar yanayin gama gari).

A gefe guda, mummunan cascade na iya ƙara yawan radiyon hanyoyin biyu. Abubuwa huɗu suna da mahimmanci don la’akari da tara farantin:

1. Yawan yadudduka;

2. Yawan da nau’in yadudduka da aka yi amfani da su (iko da/ko ƙasa);

3. Umarni ko jerin yadudduka;

4. Tazara tsakanin yadudduka.

Yawancin lokaci kawai adadin yadudduka ne aka ɗauka. A yawancin lokuta, sauran abubuwan guda uku suna da mahimmanci daidai, kuma na huɗu wani lokacin ma ba a san mai zanen PCB ba. Lokacin ƙayyade adadin yadudduka, la’akari da waɗannan masu zuwa:

1. Yawan sigina da farashin wayoyi;

2. Frequency;

3. Dole ne samfurin ya cika buƙatun ƙaddamar da Class A ko Class B?

4. PCB yana cikin gidaje masu garkuwa ko garkuwa;

5. EMC engineering expertise of the design team.

Yawancin lokaci kalma ta farko ce kawai ake ɗauka. Tabbas, duk abubuwan suna da mahimmanci kuma yakamata a yi la’akari dasu daidai. Wannan abu na ƙarshe yana da mahimmanci musamman kuma bai kamata a manta da shi ba idan za a sami kyakkyawan tsari a cikin mafi ƙarancin lokaci da farashi.

Farantin multilayer ta amfani da jirgin ƙasa da/ko wutar lantarki yana ba da raguwa mai yawa a fitowar radiation idan aka kwatanta da farantin Layer biyu. Babban dokar babban yatsa da aka yi amfani da ita ita ce farantin fale-falen fale-falen faya-fayan yana samar da ƙarancin radiyo 15dB fiye da farantin fale-fale guda biyu, duk sauran abubuwan daidai suke. A board with a flat surface is much better than a board without a flat surface for the following reasons:

1. Suna ba da damar jujjuya sigina azaman layin microstrip (ko layin kintinkiri). These structures are controlled impedance transmission lines with much less radiation than the random wiring used on two-layer boards;

2. Jirgin ƙasa yana rage rage ƙarancin ƙasa (sabili da haka hayaniyar ƙasa).

Kodayake an yi nasarar amfani da faranti biyu a cikin garkuwar da ba ta da kariya ta 20-25mhz, waɗannan lamuran banda maimakon doka. Sama da 10-15mhz, yakamata a yi la’akari da bangarori da yawa.

Akwai manufofi guda biyar da yakamata kuyi ƙoƙarin cimmawa yayin amfani da allon multilayer. Su ne:

1. Layer siginar yakamata ya kasance kusa da jirgin sama;

2. Layer siginar yakamata a haɗe sosai (kusa da) da jirgin da ke kusa da shi;

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

4, yakamata a binne siginar sauri cikin layin tsakanin jirage biyu, jirgin sama na iya taka rawar kariya, kuma yana iya murƙushe hasken babban layin da aka buga;

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

Gabaɗaya, muna fuskantar zaɓi tsakanin siginar siginar/haɗin jirgin kusanci (Objective 2) da haɗin gwiwa na ƙasa/ƙasa (haƙiƙa 3). Tare da dabarun gine -gine na PCB na al’ada, farantin farantin filastik tsakanin ƙarfin wutar lantarki da ke kusa da jirgin ƙasa bai isa ba don samar da isasshen ƙyalli a ƙasa da 500 MHz.

Sabili da haka, dole ne a magance rarrabuwa ta wasu hanyoyi, kuma yakamata mu zaɓi gaba ɗaya zaɓi madaidaicin haɗin gwiwa tsakanin siginar da jirgin dawowa na yanzu. Fa’idodin matattarar madaidaiciya tsakanin layin siginar da jirgin dawowa na yanzu zai wuce hasarar da ke haifar da ƙarancin asarar ƙarfi tsakanin jirage.

Eight layers is the minimum number of layers that can be used to achieve all five of these goals. Wasu daga cikin waɗannan maƙasudan dole ne a daidaita su akan allon huɗu da shida. A ƙarƙashin waɗannan sharuɗɗan, dole ne ku ƙayyade waɗanne maƙasudai ne mafi mahimmanci ga ƙirar da ke hannunku.

Bai kamata a fassara sakin layi na sama don nufin cewa ba za ku iya yin kyakkyawan ƙirar EMC akan allon huɗu-ko shida ba, kamar yadda za ku iya. 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.

Misali, a kan allo mai hawa takwas, idan na biyun jirgin sama ne, to ya kamata na bakwai kuma ya zama jirgin sama.

Sabili da haka, duk saitin da aka gabatar anan suna amfani da sifofi ko daidaitattun sifofi. If asymmetrical or unbalanced structures are allowed, it is possible to build other cascading configurations.

Four layer board

An nuna tsarin farantin farantin huɗu na yau da kullun a cikin Hoto 1 (jirgi mai ƙarfi da jirgin ƙasa suna musanyawa). 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.

Kodayake wannan ginin yafi kyau fiye da bangarori biyu, yana da wasu abubuwan da ba a so.

Ga jerin makasudi a Sashe na 1, wannan tari yana gamsar da manufa kawai (1). Idan yadudduka daidai suke, akwai babban rata tsakanin layin siginar da jirgin dawowa na yanzu. Hakanan akwai babban tazara tsakanin jirgin wutar lantarki da jirgin ƙasa.

Don allon mai hawa huɗu, ba za mu iya gyara lahani duka a lokaci guda ba, don haka dole ne mu yanke shawarar wanda ya fi mahimmanci a gare mu.

Kamar yadda aka ambata a baya, ƙarfin interlayer tsakanin ƙarfin wutar lantarki da ke kusa da jirgin ƙasa bai isa ba don samar da isasshen kayan datti ta amfani da dabarun sarrafa PCB na al’ada.

Dole ne ayi amfani da haɗin gwiwa ta wasu hanyoyi, kuma yakamata mu zaɓi madaidaicin haɗin gwiwa tsakanin siginar da jirgin dawowa na yanzu. 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.

Sabili da haka, hanya mafi sauƙi don haɓaka aikin EMC na farantin farantin huɗu shine kawo siginar siginar kusa da jirgin sama. 10mil), kuma yana amfani da babban mahimmin wutar lantarki tsakanin tushen wutar lantarki da jirgin ƙasa (> 40mil), kamar yadda aka nuna a Hoto 2.

Wannan yana da fa’idodi guda uku kuma kaɗan kaɗan. Yankin madaidaicin siginar ya yi ƙanƙanta, don haka ana haifar da ƙarancin yanayin yanayin rarrabewa. 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.

Na biyu, matattara haɗe-haɗe na siginar siginar zuwa ƙasa yana rage ƙarancin shirin (inductance), don haka rage yawan yanayin yanayin kebul da aka haɗa da jirgin.

Na uku, matattara mai haɗe da wayoyin da ke cikin jirgin zai rage rata tsakanin hanyoyin waya. For fixed cable spacing, crosstalk is proportional to the square of cable height. Wannan ita ce ɗayan mafi sauƙi, mafi arha, kuma mafi yawan hanyoyin da ba a kula da su don rage radadi daga PCB mai fa’ida huɗu.

Ta wannan tsarin cascade, muna gamsar da duka manufofin (1) da (2).

Wadanne hanyoyi ne akwai don tsarin laminated huɗu? Da kyau, za mu iya amfani da ɗan tsarin da ba a saba ba, wato canza layin siginar da layin jirgin sama a cikin Hoto na 2 don samar da jigon da aka nuna a Figure 3A.

Babban fa’idar wannan lamination shine cewa jirgin sama na waje yana ba da garkuwa don zirga -zirgar siginar akan layin ciki. Rashin hasara shine cewa jirgin saman ƙasa na iya yankewa da ƙarfi ta manyan abubuwan da ke cikin PCB. Ana iya rage wannan zuwa wani matakin ta hanyar juyar da jirgin, sanya jirgin wutar lantarki a gefen sinadarin, da sanya jirgin ƙasa a ɗaya gefen jirgin.

Na biyu, wasu mutane ba sa son samun jirgin sama da aka fallasa, kuma na uku, yadudduka siginar da ke binne yana da wahala a sake yin aikin jirgin. Jigon yana gamsar da haƙiƙa (1), (2), kuma yana ɗan gamsar da haƙiƙa (4).

Biyu daga cikin waɗannan matsalolin guda uku ana iya rage su ta hanyar rudani kamar yadda aka nuna a Figure 3B, inda jirage biyu na waje jirage ne na ƙasa kuma ana karkatar da wutar lantarki akan jirgin siginar azaman wayoyi.Za a karkatar da wutan lantarki ta hanyar amfani da manyan alamomi a cikin siginar siginar.

Ƙarin fa’idodi guda biyu na wannan cascade sune:

(1) Jiragen saman ƙasa guda biyu suna ba da ƙarancin ƙarancin ƙasa, don haka rage radadin kebul na al’ada;

(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. Yanzu mun cika maƙasudai (1), (2), (4) da (5) tare da jirgi huɗu kawai.

Figure 4 shows a fourth possibility, not the usual one, but one that can perform well. Wannan yayi kama da Hoto na 2, amma ana amfani da jirgin ƙasa maimakon jirgin wutar lantarki, kuma wutar lantarki tana aiki azaman alama akan layin siginar waya.

Wannan cascade ya shawo kan matsalar sake aikin da aka ambata kuma yana ba da ƙarancin ƙarancin ƙasa saboda jiragen ƙasa biyu. Duk da haka, waɗannan jiragen ba su ba da wata kariya. Wannan tsari yana gamsar da manufofi (1), (2), da (5), amma baya gamsar da buri (3) ko (4).

Don haka, kamar yadda zaku iya gani akwai ƙarin zaɓuɓɓuka don shimfidar Layer huɗu fiye da yadda kuke tsammani da farko, kuma yana yiwuwa mu hadu da huɗu daga cikin burin mu biyar tare da PCBS mai Layu huɗu. Daga mahangar EMC, shimfidar lambobi 2, 3b, da 4 duk suna aiki da kyau.

6 Layer jirgin

Yawancin allon allo mai fa’ida guda shida sun ƙunshi yadudduka na siginar siginar huɗu da yadudduka biyu na jirgin sama, kuma allunan masu fa’ida guda shida galibi sun fi allon allo huɗu daga hangen nesa na EMC.

Hoto na 5 yana nuna tsarin cascading wanda ba za a iya amfani da shi ba a kan jirgi mai layi shida.

Waɗannan jirage ba su ba da garkuwa don siginar siginar ba, kuma biyu daga cikin siginar siginar (1 da 6) ba su kusa da jirgin sama. Wannan tsarin yana aiki ne kawai idan an murƙushe dukkan siginar mitar a yadudduka 2 da 5, kuma siginar mitar muguwar ƙima ce kawai, ko mafi kyau duk da haka, babu wayoyin siginar kwata -kwata (kawai gammaye mai siyarwa) ana karkatar da su a yadudduka 1 da 6.

Idan an yi amfani da shi, duk wuraren da ba a amfani da su a kan benaye 1 da 6 ya kamata a shimfida su kuma a haɗe da babban bene a wurare da yawa.

Wannan saitin yana gamsar da ɗaya daga cikin manufofin mu na asali (Goal 3).

Tare da yadudduka shida, ƙa’idar samar da yadudduka biyu da aka binne don siginar sauri (kamar yadda aka nuna a hoto 3) ana aiwatar da ita cikin sauƙi, kamar yadda aka nuna a hoto 6. Wannan tsarin kuma yana ba da yadudduka biyu na ƙasa don siginar ƙaramin gudu.

Wataƙila wannan shine tsarin da aka fi amfani da shi sau shida kuma yana iya zama mai tasiri sosai wajen sarrafa fitar da wutar lantarki idan an yi shi da kyau. Wannan saitin yana gamsar da burin 1,2,4, amma ba manufa 3,5 ba. Its main disadvantage is the separation of power plane and ground plane.

Saboda wannan rarrabuwar kawunan, babu ƙarfin haɓakawa tsakanin jirgi mai ƙarfi da jirgin ƙasa, don haka dole ne a aiwatar da ƙira mai kyau don shawo kan wannan yanayin. Don ƙarin bayani game da datsewa, duba nasihun dabarunmu na Decoupling.

An nuna kusan iri ɗaya, mai ɗabi’a mai tsari mai ƙyalli shida a cikin Hoto 7.

H1 yana wakiltar layin siginar a kwance na siginar 1, V1 tana wakiltar madaidaiciyar hanyar siginar siginar 1, H2 da V2 suna wakiltar ma’anar guda ɗaya don siginar 2, kuma fa’idar wannan tsarin ita ce siginar zirga -zirgar orthogonal koyaushe tana nufin jirgin sama ɗaya.

Don fahimtar dalilin da yasa wannan yake da mahimmanci, duba sashe akan jirage masu nuna sigina a cikin Sashe na 6. Rashin hasara shine cewa siginar Layer 1 da Layer 6 ba a kare su ba.

Sabili da haka, layin siginar yakamata ya kasance kusa da jirgin da ke kusa da shi kuma yakamata a yi amfani da babban kaurin tsakiyar don yin kaurin farantin da ake buƙata. Halin 0.060 inci mai kauri mai fa’ida yana iya zama 0.005 “/ 0.005″/ 0.040 “/ 0.005″/ 0.005 “/ 0.005”. Wannan tsarin ya gamsar da Manufofin 1 da 2, amma ba burin 3, 4 ko 5 ba.

An nuna wani farantin Layer guda shida tare da kyakkyawan aiki a cikin hoto 8. Yana ba da siginar binne sigina biyu da madafan iko da jiragen ƙasa don saduwa da dukkan manufofi guda biyar. Koyaya, babban koma -baya shine kawai yana da yadudduka wayoyi guda biyu, don haka ba a amfani dashi sosai.

Farantin Layer guda shida ya fi sauƙi don samun jituwa mai kyau na electromagnetic fiye da farantin Layer huɗu. Hakanan muna da fa’idar huɗu na jujjuyawar sigina huɗu maimakon iyakance zuwa biyu.

Kamar yadda ya kasance tare da allon da’irar huɗu, PCB mai fa’ida shida ya sadu da maƙasudanmu guda biyar. Za a iya cika dukkan maƙasudai guda biyar idan muka takaita kanmu zuwa yadudduka masu sigina biyu. Tsarin a cikin Hoto 6, Hoto 7, da Hoto 8 duk suna aiki da kyau daga hangen EMC.