I-BGA Rework: Umhlahlandlela Wochwepheshe Wokulungisa Ingxenye ye-PCB

Isingeniso

Ziyini Izingxenye ze-BGA?

Amaphakheji e -Ball Grid Array (BGA) amelela obunye bobuchwepheshe obuphambili bokufaka ubuso kuma-elekthronikhi anamuhla. Ngokungafani namaphakheji endabuko ane-lead, ama-BGA asebenzisa uhla lwamabhola e-solder ngaphansi kwengxenye ukuze asungule ukuxhumana kukagesi nokwemishini ne-PCB. Lo mklamo uvumela ukubalwa kwamaphini aphezulu, ukusebenza okuphezulu kokushisa, kanye nosayizi wephakheji oncishisiwe—okwenza ama-BGA abaluleke kakhulu kuma-processor, ama-memory chip, kanye nama-IC ayinkimbinkimbi kuma-smartphone, amaseva, kanye nezinhlelo zezimoto.

Kungani Kubalulekile Ukulungisa I-BGA

Ukulungiswa kabusha kwe-BGA kubalulekile ekukhiqizweni nasekulungisweni kwe -PCB ngoba izingxenye ze-BGA ezinephutha noma ezihlulekile azikwazi ukuthungwa ngesandla njengezingxenye ezinezimbobo. Amajoyinti e-solder afihliwe ngaphansi kwephakheji adinga amasu akhethekile okususa, ukulungisa indawo, kanye nokufaka esikhundleni.

Izimo ezivamile ezidinga ukulungiswa kabusha kwe-BGA zifaka phakathi amaphutha okukhiqiza (ukubopha, izikhala, amalunga abandayo), ukwehluleka kwensimu ngenxa yokujikeleza kokushisa noma ukucindezeleka komshini, kanye nemiyalelo yokushintsha ubunjiniyela edinga ukuthuthukiswa kwezingxenye.

Amathuluzi Nemishini Yokuvuselela i-BGA

Iziteshi Zokulungisa

Ukulungiswa kabusha kwe-BGA yobungcweti kudinga iziteshi ezizinikele ezihlonyiswe ngezinhlelo zokushisa ezinembile.

• Iziteshi zokuvuselela umoya oshisayo – Ukushisa okugxilile okuqondiswayo ngokusebenzisa ama-nozzle ahlelekayo kunciphisa ukucindezeleka kokushisa ezingxenyeni ezizungezile.
• Izinhlelo zokuvuselela i-infrared (IR) – Ukushisa okufanayo ezindaweni ezinkulu kunciphisa i-oxidation futhi kuqinisekisa ukusatshalaliswa kwezinga lokushisa elilinganayo.

Izinhlelo ze-hybrid ezihlanganisa zombili lezi zobuchwepheshe zinikeza ukuguquguquka okuphezulu, okuvumela opharetha ukuthi bakhethe indlela yokushisa efanele ngokusekelwe ohlotsheni lwezingxenye kanye nokwakhiwa kwebhodi.

Amathuluzi Okugoqa Nokujikijela

Ngaphandle kwemishini yokushisa eyinhloko, ukulungiswa kabusha kwe-BGA kudinga amathuluzi awusizo:

• Ukwenza kahle hle izinsimbi zokunamathisela ngomsebenzi wokulungisa
• Amathuluzi okuthatha i-vacuum yokuphathwa kwezingxenye
• Izifaki ze-Flux (amapeni, amasirinji, noma izinhlelo zokukhipha indle)
• Ama-stencil noma ama-preforms e-solder paste ngemisebenzi yokuphinda ubhale ibhola

I-flux esezingeni eliphezulu engahlanzekile noma encibilikayo emanzini efanele i-solder alloy (enomthofu noma engenawo umthofu) iqinisekisa ukumanziswa okufanele futhi inciphisa izidingo zokuhlanza ngemva kokulungiswa kabusha.

Ukuhlolwa Izinsiza kusebenza

Amandla okuhlola aphelele awakwazi ukuxoxiswana ngawo ukuze kuqinisekiswe ukuvuselelwa kwe-BGA.

• Isibonakhulu se-stereo vumela ukuhlolwa okubonakalayo kokubekwa kwe-solder paste kanye nokuqondanisa.
• Izinhlelo zokuhlola i-X-ray kwembula amaphutha afihliwe ngaphansi kwe-BGA—izikhala, ukubopha, umcamelo ongaphakathi, kanye nomthamo onganele we-solder.
• Ukuhlola okuzenzakalelayo (AOI) inikeza ukuqinisekiswa okusheshayo kokunemba kokubekwa.

Ngaphandle kwamathuluzi okuhlola afanele, impumelelo yokulungisa kabusha i-BGA ayinakuqinisekiswa ngokuthembekile.

Inqubo Yokusebenza Kabusha ye-BGA Isinyathelo Ngesinyathelo

Ukulungiselela

Ukulungiselela kahle kunquma umphumela wokusebenza kabusha. Qala ngokuhlanza i-PCB ukuze ususe ukungcola okungaphazamisa ukushisa noma ukuhlolwa. Yenza ukuhlolwa okungenayo ukuze ubhale phansi izimo ezikhona bese uthola iphutha elidinga ukulungiswa. Faka i-masking tape yokushisa okuphezulu noma isivikelo se-aluminium ukuze uvikele izingxenye eziseduze—ikakhulukazi lezo ezinezilinganiso zokushisa eziphansi noma ukuzwela komswakama. Qinisekisa ukuqondiswa kwezingxenye bese uqinisekisa izidingo zokubhalisa i-pad-to-ball.

Ukususwa kwe-BGA Enephutha

Ukususwa kwengxenye kulandela iphrofayili yokushisa elawulwayo. Shisisa yonke i-PCB kusukela ngezansi ukuze unciphise ama-gradient okushisa futhi uvimbele ukugoba—ngokuvamile kuya ku-150-180°C kuye ngokuthi ibhodi lijiyile kangakanani. Faka ukushisa okuphezulu usebenzisa umoya oshisayo noma uhlelo lwe-IR, ulandela iphrofayili ekhombisa ijika lokuqala lokugeleza kabusha. Uma i-solder ifika ku-liquidus, sebenzisa i-vacuum pickup ukuze uphakamise i-BGA ngokuqondile. Ungalokothi ushelele noma ujike ingxenye, njengoba lokhu kungadabula amaphedi kusuka ku-substrate.

Ukuhlanza Ibhodi

Ngemva kokususwa kwengxenye, i-solder esele kumele isuswe kuma-pads. Sebenzisa i-copper braid (i-solder wick) ene-flux entsha ukuze ususe i-solder eyengeziwe ngenkathi indawo isafudumele. Uma ubeka i-soldering iqinile, i-soldering iron elawulwa ukushisa iyasiza ekuhlanganiseni i-solder esele. Hlanza indawo nge-isopropyl alcohol noma i-flux remover efanele. Hlola ngaphansi kokukhulisa ukuqinisekisa ukuthi wonke ama-pads ayisicaba, ahlanzekile, futhi awanazo izinsalela eziphakanyisiwe noma i-solder mask eyonakele.

Ukufaka esikhundleni kanye nokushisela

Faka i-flux noma i-solder paste endaweni elungisiwe usebenzisa ama-stencil noma i-dispensing elawulwayo. Beka i-BGA esikhundleni usebenzisa uhlelo lokuqondanisa umbono lwesiteshi sokuvuselela—ukunemba lapha kuthinta ngqo isivuno. Yenza iphrofayili yokugeleza kabusha elawulwayo: i-ramp kancane kancane ukuze ucwilise izinga lokushisa, ukuguquka ngokusebenzisa i-liquidus, ukubamba izinga lokushisa eliphakeme, kanye nokupholisa okulawulwayo. Gwema ukudlula imikhawulo yokushisa echazwe ngumkhiqizi. Vumela ukuhlanganiswa kuphole ngokwemvelo; ukupholisa okuphoqelelwe kungabangela ukushaqeka kokushisa kanye nokuqhekeka okuncane emajoyintini e-solder.

Ukuhlolwa Kwangemva Komsebenzi Obusha

Qinisekisa yonke i-BGA ephinde yasebenza ngokuhlola okuhlelekile. Ukuhlolwa okubonakalayo ngaphansi kokukhulisa kuqinisekisa ukuhambisana okufanele kanye nokungabikho kweziphambeko zangaphandle. Ukuhlolwa kwe-X-ray kuyimpoqo ukuhlola ikhwalithi yamalunga efihliwe—ukuhlola izimbobo ezidlula imikhawulo yencazelo, ukuvala phakathi kwamabhola, iziphambeko zekhanda elisecaleni, kanye nokuwa kwebhola okufanele. Phetha ngokuhlolwa kukagesi (i-ICT noma ukuhlolwa kokusebenza) ukuqinisekisa ukuthi konke ukuxhumana kusebenza ngaphakathi kwencazelo.

Izinselele Ezivamile Ekusebenzeni Kabusha Kwe-BGA

I-Solder Joint Defects

Ukuhlanganisa i-solder kwenzeka lapho amabhola aseduze ehlangana, okudala amafushane—ngokuvamile okubangelwa ukunamathisela ngokweqile kwe-solder, ukungalungi kahle, noma ukuphakama okunganele kokuma. Amalunga abandayo avela ekushiseni okunganele noma isikhathi sokuhlala isikhathi eside, okukhiqiza ukuxhumana okubuthakathaka, okukristalu okunamandla amancane okusebenza. Amaphutha ekhanda-emcamelweni avela lapho i-solder yengxenye nebhodi yehluleka ukuhlangana kahle ngesikhathi sokugeleza kabusha, ngokuvamile ngenxa ye-oxidation noma i-warpage.

Izinkinga Zokuphatha Okushisayo

Ukuqhekeka kwe-PCB ngesikhathi sokulungiswa kabusha kwe-BGA kuvela ekushiseni okungalingani noma ekushiseni ngokweqile kulo lonke ilungiselelo. Amabhodi anezingqimba eziningi kanye nalawo anezingqimba zethusi ezisindayo adinga izigaba ezinde zokushisa kusengaphambili kanye nokuphrofayilishwa ngokucophelela. Umonakalo wezingxenye ezivela ekushiseni ngokweqile ubonakala njengokwehlukaniswa kwephakheji, ukuqhekeka kokufa, noma amapharamitha kagesi awonakele. Ukugeleza kabusha noma ukukhumuka kwezingxenye eziseduze kwenzeka lapho ukuvikela kukhombisa ukunganele noma ukukhetha i-nozzle kuvumela ukushisa ukuthi kusabalale ngale kwendawo okuqondiwe kuyo.

Ukulungiswa kanye nomonakalo wephedi

Ukungalingani phakathi kwamabhola e-BGA nama-PCB pads kubangela amasekethe avulekile noma ukuxhumana okungenazikhawu. Ama-BGA acwebezelayo (0.4mm nangaphansi) adinga ukunemba okumangalisayo kokubekwa—ngokuvamile okungaphezu kwamandla esandla. Ukuphakamisa ama-pad noma ukugoqa ngesikhathi sokususwa kwezingxenye kubangelwa amandla okususa ngokweqile, ukuncibilika kwe-solder okunganele, noma izinkinga zokunamathela ezikhona kakade. Ama-pad alimele angadinga ukulungiswa kokuhlinzwa okuncane noma enze ibhodi lingalungiseki.

Imikhuba Emihle Yokusebenza Kabusha Kwe-BGA Okuphumelelayo

Ukuthuthukiswa Kwephrofayili Yokushisa

Thuthukisa futhi ubhale phansi amaphrofayili okushisa aqondene nohlobo ngalunye lokuhlanganiswa kwe-PCB . Izinto ezihlukene ze-substrate (FR-4, high-Tg, polyimide, ceramic) zidinga izindlela ezihlukile zokushisa. Iphrofayili enama-thermocouple anamathiselwe kokubili phezulu kwe-BGA kanye nephansi le-PCB ukuqinisekisa umehluko ofanele wokushisa. Lawula amazinga okushisa nokupholisa ngaphakathi kuka-2-4°C/umzuzwana ukuze unciphise ukucindezeleka kokushisa. Qinisekisa amaphrofayili kuma-assembly ascrap ngaphambi kokuphinda ukhiqize.

Ukulawulwa Kwenqubo kanye Nobuchwepheshe

Sebenzisa ikhemikhali efanele yokuxuba ehambisana ne-solder alloy—ukuxuba okungahlanzekile kwezicelo eziningi, okungancibiliki emanzini lapho kuhlelwa ukuhlanza ngamandla. Faka i-solder paste noma ukuxuba ngokulinganayo; ukumbozwa okungaguquki kubangela ukumanzisa okungalingani. Gcina ubukhulu be-nozzle obufanele—ama-nozzle kufanele abe makhulu ngo-2-5mm kunengxenye ohlangothini ngalunye. Hlanza imishini yokushintsha njalo ukuze uvimbele ukungcola. Abasebenzi abanekhono abanokuqeqeshwa okubhaliwe bathuthukisa kakhulu amazinga okukhiqiza okuqala ekusebenzeni kabusha kwe-BGA.

Izinto Okufanele Uzicabangele Ngokuphepha Ngokuvuselelwa Kwe-BGA

Ukuphepha kwe-Solder kanye neKhemikhali

I-solder ene-lead (SnPb) idinga ukuphathwa ngokucophelela ukuze kuvinjelwe ukuchayeka kwe-lead—geza izandla kahle ngemva kokuthintana, gwema ukudla ezindaweni zokusebenza, futhi usebenzise i-PPE efanele. Ama-alloy angenalo i-lead (SAC305, njll.) adinga amazinga okushisa aphezulu enqubo, okwandisa ingozi yokusha. Intuthu ephumayo kanye nezinyibilikisi zokuhlanza zidinga umoya owanele; ukukhishwa kwentuthu endaweni esiteshini sokuvuselela kubamba intuthu emthonjeni. Landela amaphepha edatha okuphepha kwezinto ezibonakalayo kuwo wonke amakhemikhali asetshenziswa enqubweni yokuvuselela.

Ukuphepha kwe-ESD kanye nemishini

Ukuvikelwa kokukhishwa kwe-electrostatic kubalulekile kulo lonke umsebenzi wokuvuselela i-BGA. Gcina izindawo zokusebenza eziphephile ze-ESD ngama-mat asekelwe phansi, izintambo zesandla, kanye ne-ionization lapho kufanele khona. Phatha ama-BGA kuphela ezindaweni ezivikelwe yi-ESD. Ukuphepha kwemishini kuhlanganisa ukuphathwa kahle kwe-nozzle yomoya oshisayo (amazinga okushisa adlula ama-350°C ngesikhathi sokusebenza), ukuqinisa i-PCB ukuze kuvinjelwe ukuwa kwebhodi, kanye nokugcinwa njalo kwezinhlelo zokushisa ukuqinisekisa ukunemba kokulinganisa.

Isiphetho

Ukulungiswa kabusha kwe-BGA kuyikhono elibalulekile ekukhiqizweni nasekulungisweni kwe-PCB yesimanje. Uhlobo olufihliwe lwamajoyinti e-BGA solder ludinga imishini ekhethekile, ukulawulwa kwenqubo okuqinile, kanye nokuhlolwa okuphelele kuzo zonke izigaba. Impumelelo idinga ukuqonda ukusebenzisana phakathi kwamaphrofayili okushisa, i-flux chemistry, kanye nokuphathwa kwemishini.

Ngokulandela imikhuba emihle kakhulu esekiwe—ukulungiselela okufanele, ukushisa okulawulwayo, ukuqondanisa okunembile, kanye nokuqinisekiswa okuphelele ngemva kokulungiswa kabusha—abakhiqizi bathola imiphumela ethembekile ehlangabezana nezimfuneko zekhwalithi yokuqala.