INKQUBO YOKUQHUBEKA EMPHEKWENI

I-Reflow soldering iyindlela esetshenziswa kakhulu yokunamathisela izingxenye ze-surface mount kumabhodi wesekethe aphrintiwe (ama-PCB).Inhloso yale nqubo ukwakha amajoyinti amukelekayo e-solder ngokuqala ukushisa kuqala izingxenye / PCB/solder unama bese uncibilikisa i-solder ngaphandle kokudala umonakalo ngokushisa ngokweqile.

Izici ezibalulekile eziholela enqubweni esebenzayo yokuphinda i-reflow soldering yilezi ezilandelayo:

1. Umshini ofanelekayo
2. Iphrofayela eyamukelekile yokugeleza kabusha
3. I-PCB/ingxenye ye-footprint Design
4. I-PCB ephrintiwe ngokucophelela kusetshenziswa i-stencil eklanywe kahle
5. Ukubekwa okuphindaphindiwe kwezingxenye zokukhweza ngaphezulu
6. Ikhwalithi enhle ye-PCB, izingxenye kanye nokunamathisela kwe-solder

Umshini Ofanelekayo

Kunezinhlobo ezehlukene zomshini wokuphinda ugaywe we-solder otholakalayo kuye ngesivinini somugqa odingekayo kanye nomklamo/impahla yemihlangano ye-PCB ezocutshungulwa.Uhhavini okhethiwe udinga ukuba nosayizi ofanele ukuphatha izinga lokukhiqiza lempahla yokukhetha nendawo.

Isivinini somugqa singabalwa njengoba kukhonjisiwe ngezansi:-

Isivinini somugqa (ubuncane) =Amabhodi ngomzuzu x Ubude bebhodi ngalinye
Layisha Factor (isikhala phakathi kwamabhodi)

Kubalulekile ukucabangela ukuphindaphinda kwenqubo futhi ngakho 'Isici Somthwalo' ngokuvamile sicaciswa umkhiqizi womshini, isibalo esiboniswe ngezansi:

Ukuze ukwazi ukukhetha usayizi olungile wokugeleza kwehhavini isivinini senqubo (echazwe ngezansi) kufanele sibe sikhulu kunejubane elincane elibaliwe lomugqa.

Isivinini senqubo =Igumbi likahhavini ubude obushisiwe
Isikhathi sokuhlala senqubo

Ngezansi isibonelo sokubala ukuthola usayizi wehhavini olungile:-

Umhlanganisi we-SMT ufuna ukukhiqiza amabhodi angu-8-intshi ngenani elingu-180 ngehora.Umkhiqizi wokunamathisela we-solder uncoma imizuzu emi-4, iphrofayili yezinyathelo ezintathu.Ngidinga uhhavini isikhathi esingakanani ukuze ngicubungule amabhodi kulokhu kuphuma?

Amabhodi ngomzuzu = 3 (180/ihora)
Ubude bebhodi ngalinye = 8 amayintshi
Isici Somthwalo = 0.8 (isikhala esingu-2-intshi phakathi kwamabhodi)
Isikhathi Sokuhlala Kwenqubo = imizuzu emi-4

Bala isivinini somugqa:(3 amabhodi/min) x (8 amayintshi/ibhodi)
0.8

Isivinini somugqa = 30 amayintshi/ngomzuzu

Ngakho-ke, i-ovini yokugeleza kabusha kufanele ibe nesivinini senqubo okungenani amasentimitha angama-30 ngomzuzu.

Nquma ubude obushisiwe begumbi likahhavini ngesibalo sesivinini senqubo:

30 in/min =Igumbi likahhavini ubude obushisiwe
4 amaminithi

Ubude obushisiwe be-oven = 120 amayintshi (10 amafidi)

Qaphela ukuthi ubude behhavini buzodlula amafidi angu-10 kuhlanganise nesigaba sokupholisa kanye nezingxenye zokulayisha zokuthutha.Isibalo esobude be-HEATED - HHAYI UBUDE BUKAHHOVISI BONKE.

2. Ukulawulwa kwe-loop evaliwe yejubane labalandeli be-convection - Kunamaphakheji athile okufakwa phezulu okungaphezulu njenge-SOD323 (bheka ukufaka) anendawo encane yokuxhumana nesilinganiso sobuningi okungenzeka ukuthi siphazamiseke ngesikhathi senqubo yokugeleza kabusha.Ukulawulwa kwesivinini se-loop esivaliwe sabalandeli bomhlangano kuyindlela enconyiwe yemihlangano esebenzisa izingxenye ezinjalo.

3. Ukulawula okuzenzakalelayo kwe-conveyor kanye nobubanzi bokusekelwa kwebhodi eliphakathi - Eminye imishini inokulungiswa kobubanzi okwenziwa ngesandla kodwa uma kukhona amaqoqo amaningi ahlukene okufanele acutshungulwe ngobubanzi obuhlukahlukene be-PCB khona-ke le nketho iyanconywa ukugcina inqubo engashintshi.

Iphrofayela Yokugeleza Kabusha eyamukelekile

Ukuze udale iphrofayela egeleza kabusha ama-thermocouples axhunywe kumhlangano wesampula (ngokuvamile nge-solder yokushisa okuphezulu) ezindaweni eziningi ukuze kulinganiswe ububanzi bamazinga okushisa ku-PCB yonkana.Kunconywa ukuthi okungenani kube ne-thermocouple eyodwa ebekwe phezu kwephedi ngasemaphethelweni e-PCB kanye ne-thermocouple eyodwa ebekwe phezu kwephedi maphakathi ne-PCB.Ngokufanelekile ama-thermocouples engeziwe kufanele asetshenziselwe ukukala ububanzi obugcwele bamazinga okushisa kuyo yonke i-PCB - eyaziwa ngokuthi 'i-Delta T'.

Ngaphakathi kwephrofayili ye-reflow soldering evamile ngokuvamile kunezigaba ezine - Ukushisa, ukucwilisa, ukugeleza kabusha nokupholisa.Inhloso eyinhloko ukudlulisa ukushisa okwanele emhlanganweni ukuze kuncibilike i-solder futhi yakhe amalunga e-solder ngaphandle kokudala umonakalo ezingxenyeni noma kwi-PCB.

Shisisa ngaphambili– Phakathi nalesi sigaba izingxenye, i-PCB kanye ne-solder konke kushisiswe endaweni ethile noma kumazinga okushisa okuhlala ngokuqaphela ukuthi angashisi ngokushesha (imvamisa angabi ngaphezu kuka-2ºC/sesekhondi – hlola imininingwane yedatha ye-solder).Ukushisa ngokushesha kungabangela ukukhubazeka okufana nezingxenye ukuthi ziqhekeke futhi i-solder inamathisele i-splatter ibangele amabhola e-solder ngesikhathi sokugeleza kabusha.

Cwilisa- Inhloso yalesi sigaba ukuqinisekisa ukuthi zonke izingxenye zifinyelela ezingeni lokushisa elidingekayo ngaphambi kokungena esigabeni sokugeleza kabusha.I-Soak ngokuvamile ihlala phakathi kwamasekhondi angu-60 kanye ne-120 kuye ngokuthi 'umehluko omkhulu' wenhlangano kanye nezinhlobo zezingxenye ezikhona.Uma ukudlulisa ukushisa kuphumelela kakhulu phakathi nesigaba sokucwilisa kudingeka isikhathi esincane.

Uma iphrofayili yokugeleza kabusha inokushisa okwanele okusetshenziswe ngesikhathi sokugeleza kabusha kuzoba namajoyinti e-solder abonakala afana nezithombe ezingezansi: -

i-solder engakhiwenga i-fillet ngomthofu

Akuwona wonke amabhola e-solder ancibilikile

Isici esivamile sokudambisa ngemva kokugeleza kabusha ukwakheka kwamabhola/ubuhlalu obuphakathi kwe-chip njengoba kungabonakala ngezansi.Isixazululo salesi sici ukuguqula ukwakheka kwe-stencil -eminye imininingwane ingabonwa lapha.

Ukusetshenziswa kwe-nitrogen ngesikhathi senqubo yokugeleza kabusha kufanele kucatshangelwe ngenxa yomkhuba wokusuka kude ne-solder paste equkethe ama-fluxes aqinile.Inkinga empeleni akulona ikhono lokugeleza kabusha ku-nitrogen, kodwa kunalokho ikhono lokugeleza kabusha lapho ungekho umoya-mpilo.I-solder yokushisisa lapho kukhona umoya-mpilo izodala ama-oxide, ngokuvamile okuyizindawo ezingadayisi.

Ukupholisa– Lesi yisigaba lapho ukuhlangana kupholiswa khona kodwa kubalulekile ukuthi ungapholisi ukuhlanganiswa ngokushesha okukhulu – ngokuvamile izinga lokupholisa elinconywayo akufanele lidlule ku-3ºC/ngesekhondi.

PCB/Component Footprint Design

Kunezici ezimbalwa zokwakheka kwe-PCB ezinethonya lokuthi umhlangano uzogeleza kahle kanjani.Isibonelo esiwusayizi wamathrekhi axhumeka endaweni yokunyathelisa - uma ithrekhi exhumeka ohlangothini olulodwa lwengxenye yonyawo inkulu kunolunye lokhu kungaholela ekungalinganini kwe-thermal okubangela ukuthi ingxenye 'itshe lethuna' njengoba kungabonakala ngezansi:-

Esinye isibonelo 'i-copper balancing' - imiklamo eminingi ye-PCB isebenzisa izindawo ezinkulu zethusi futhi uma i-pcb ifakwa kuphaneli ukusiza inqubo yokukhiqiza ingaholela ekungalinganini kwethusi.Lokhu kungabangela iphaneli ukuthi iguqe ngesikhathi sokugeleza futhi ngakho-ke isixazululo esinconyiwe ukufaka 'i-copper balancing' ezindaweni ezingcolile zephaneli njengoba kungabonakala ngezansi:-

Bheka'Idizayini Yokukhiqiza'kokunye ukucatshangelwa.

I-PCB ephrintiwe ngokucophelela kusetshenziswa i-stencil eklanywe kahle

Izinyathelo zenqubo yangaphambilini ngaphakathi komhlangano wokukhweza ongaphezulu zibalulekile enqubweni esebenzayo yokugeleza kwe-solder.Isolder unama ukuphrinta inqubokuyisihluthulelo sokuqinisekisa idiphozi engaguquki yokunamathisela kwe-solder ku-PCB.Noma yiliphi iphutha kulesi sigaba lizoholela emiphumeleni engathandeki futhi kanjalo nokulawula okuphelele kwale nqubo kanyei-stencil design ephumelelayoiyadingeka.

Ukubekwa okuphindaphindiwe kwezingxenye zokukhweza ngaphezulu

Ukuhluka kokubekwa kwengxenye

Ukubekwa kwezingxenye zokukhweza ngaphezulu kufanele kuphindaphindeke ngakho-ke umshini wokukhetha nendawo othembekile, ogcinwe kahle uyadingeka.Uma amaphakheji ezingxenye engafundiswanga ngendlela efanele angabangela ukuthi uhlelo lokubona kwemishini lungaboni ingxenye ngayinye ngendlela efanayo ngakho-ke ukuhlukahluka kokubekwa kuzobonwa.Lokhu kuzoholela emiphumeleni engahambisani ngemva kwenqubo yokuphinda kufakwe i-solder.

Izinhlelo zokubeka izingxenye zingadalwa kusetshenziswa imishini yokukhetha nendawo kodwa le nqubo ayinembile njengokuthatha ulwazi lwe-centroid ngokuqondile kudatha ye-PCB Gerber.Imvamisa le datha ye-centroid ithunyelwa isuka ku-PCB design software kodwa ngesinye isikhathi ayitholakali ngakho-keservice ukukhiqiza ifayela centroid kusuka idatha Gerber inikezwa Surface Mount Process.

Yonke imishini yokubeka izingxenye izoba 'nokunemba kokubekwa' okucaciswe njengokuthi:-

35um (QFPs) kuya ku-60um (ama-chips) @ 3 sigma

Kubalulekile futhi ukuthi kukhethwe umlomo wombhobho ofanele ohlotsheni lwengxenye ezobekwa - uhla lwezimbobo zokubeka izingxenye ezahlukene lungabonakala ngezansi:-

Ikhwalithi enhle ye-PCB, izingxenye kanye nokunamathisela kwe-solder

Izinga lazo zonke izinto ezisetshenziswa ngesikhathi senqubo kumele libe phezulu ngoba noma yini engeyinhle izoholela emiphumeleni engathandeki.Kuye ngenqubo yokukhiqiza yama-PCB kanye nendlela agcinwe ngayo ukuphela kwama-PCB kungaholela ekuqineni kahle kwe-solderabilty ngesikhathi senqubo yokuphinda i-solder.Ngezansi isibonelo salokho okungabonwa lapho ukuphela kwe-PCB kungalungile okuholela ekulimaleni okwaziwa nge-'Black Pad':-

IQINISO ELIHLE PCB QEDA

I-PCB ishibhile

I-Solder igeleza engxenyeni hhayi i-PCB

Ngendlela efanayo ikhwalithi yengxenye ye-surface mount lead ingaba mpofu kuye ngenqubo yokukhiqiza kanye nendlela yokugcina.

Izinga le-solder paste lithinteka kakhulu yi-ukugcinwa nokuphatha.Ikhwalithi embi yokunamathisela i-solder uma isetshenziswa ingase inikeze imiphumela njengoba ingabonakala ngezansi: -