INKQUBO YOKUFAKA UMBUSO

I-Reflow soldering yeyona ndlela isetyenziswa kakhulu yokuncamathelisa amacandelo omgangatho wentaba kwiibhodi zesekethe eziprintiweyo (PCBs).Injongo yale nkqubo kukwenza ii-solder ezamkelekileyo ngokufudumeza kuqala amacandelo / i-PCB / i-solder paste kwaye unyibilikise i-solder ngaphandle kokwenza umonakalo ngokufudumeza.

Imiba ephambili ekhokelela kwinkqubo esebenzayo ye-reflow soldering yile ilandelayo:

1. Umatshini ofanelekileyo
2. Iprofayile eyamkelekileyo yokubuyisela kwakhona
3. I-PCB/icandelo lophawu loYilo
4. I-PCB eprintwe ngononophelo kusetyenziswa istensile eyilwe kakuhle
5. Ukubekwa okuphindaphindiweyo kwamacandelo okunyuka komphezulu
6. Umgangatho olungileyo we-PCB, amacandelo kunye ne-solder paste

Umatshini ofanelekileyo

Kukho iintlobo ezahlukeneyo zomatshini wokuphinda uthengise i-reflow ekhoyo ngokuxhomekeke kwisantya somgca ofunekayo kunye noyilo / izinto zeendibano ze-PCB eziza kuqhutyelwa phambili.I-oven ekhethiweyo kufuneka ibe yisayizi efanelekileyo yokusingatha izinga lokuvelisa i-pick kunye nendawo yezixhobo.

Isantya somgca singabalwa njengoko kubonisiwe ngezantsi:-

Isantya somgca (ubuncinci) =Iibhodi ngomzuzu x Ubude kwibhodi nganye
Umthwalo weFactor (isithuba phakathi kweebhodi)

Kubalulekile ukuqwalasela ukuphinda-phinda kwenkqubo kwaye ke 'iFactor yomthwalo' idla ngokuchazwa ngumenzi womatshini, ubalo oluboniswe ngezantsi:

Ukuze ukwazi ukukhetha ubungakanani obuchanekileyo be-oveni yokubuyisela kwakhona isantya senkqubo (esichazwe ngezantsi) kufuneka sibe sikhulu kunesantya esincinci esibaliweyo somgca.

Isantya senkqubo =Igumbi le-oveni ubude obushushu
Ixesha lokuhlala kwinkqubo

Apha ngezantsi ngumzekelo wokubala ukuseka ubungakanani obuchanekileyo be-oveni: -

Umhlanganisi we-SMT ufuna ukuvelisa iibhodi ezi-8-intshi ngesantya se-180 ngeyure.Umenzi we-solder paste ucebisa umzuzu we-4, iprofayili yamanyathelo amathathu.I-oveni ifuna ixesha elingakanani ukwenza iibhodi kolu gqibo?

Iibhodi ngomzuzu = 3 (180/yure)
Ubude bebhodi nganye = 8 intshi
Umthwalo weFactor = 0.8 (2-inch space phakathi kweebhodi)
Inkqubo yokuHlala ixesha = imizuzu emi-4

Bala isantya somgca:(3 iibhodi/min) x (8 intshi/ibhodi)
0.8

Isantya somgca = 30 intshi/ngomzuzu

Ngoko ke, i-oven reflow kufuneka ibe nesantya senkqubo ubuncinane ubuncinane be-intshi ezingama-30 ngomzuzu.

Qinisekisa ubude begumbi le-oveni elishushu ngesantya seequation:

30 kwi/min =Igumbi le-oveni ubude obushushu
Imizuzu emi-4

Ubude be-oven eshushu = 120 intshi (10 feet)

Qaphela ukuba ubude obupheleleyo be-oven buya kudlula iinyawo ze-10 kubandakanywa necandelo lokupholisa kunye namacandelo okulayishwa kwe-conveyor.Isibalo sesobude be-Oveni OKUSHISAYO - AYIKHO UBUDE BOKUGQIBELA.

2. Ukulawulwa kwe-loop evaliweyo kwisantya sabalandeli be-convection - Kukho iipakethi ezithile zokunyuka kwendawo efana ne-SOD323 (jonga i-insert) enendawo encinci yokudibanisa kwi-mass ratio enokuthi iphazamiseke ngexesha lenkqubo yokubuyisela kwakhona.Ukulawulwa kwesantya se-loop esivaliweyo sabalandeli bendibano lukhetho olucetyiswayo kwiindibano ezisebenzisa iindawo ezinjalo.

3. Ulawulo oluzenzekelayo lwe-conveyor kunye ne-center-board-support wides - Abanye oomatshini banohlengahlengiso lobubanzi bemanuwali kodwa ukuba kukho iindibano ezininzi ezahlukeneyo eziza kucutshungulwa ngobubanzi obuhlukeneyo bePCB ngoko olu khetho luyacetyiswa ukuba kugcinwe inkqubo engaguqukiyo.

Iprofayile yeReflow eyamkelekileyo

Ukuze udale iprofayile ye-reflow thermocouples idityaniswe kwindibano yesampulu (idla ngokuba ne-solder yobushushu obuphezulu) kwiindawo ezininzi ukulinganisa uluhlu lwamaqondo obushushu kwiPCB.Kuyacetyiswa ukuba ubuncinci ube ne-thermocouple enye ebekwe kwiphedi ukuya kumda we-PCB kunye ne-thermocouple enye ebekwe kwiphedi ukuya kumbindi we-PCB.Ngokunqwenelekayo kufuneka kusetyenziswe iithermocouples ezininzi ukulinganisa uluhlu olupheleleyo lwamaqondo obushushu kwi-PCB yonke – eyaziwa ngokuba yi-'Delta T'.

Ngaphakathi kweprofayili ye-reflow soldering eqhelekileyo kukho izigaba ezine-Preheat, soak, reflow kunye nokupholisa.Eyona njongo iphambili kukudlulisa ubushushu obaneleyo kwindibano ukunyibilikisa i-solder kunye nokwenza i-solder joints ngaphandle kokwenza umonakalo kumacandelo okanye kwi-PCB.

Ukutshisa kwangaphambiliNgeli nqanaba amacandelo, i-PCB kunye ne-solder zonke zifudunyezwa kwi-soak ecacisiweyo okanye iqondo lokushisa elihlala liqaphela ukuba lingafudumeza ngokukhawuleza (ngokuqhelekileyo akukho ngaphezu kwe-2ºC / isibini - khangela i-solder paste yedatha).Ukufudumeza ngokukhawuleza kunokubangela iziphene ezifana nezixhobo zokuqhekeka kunye ne-solder paste kwi-splatter ebangela iibhola ze-solder ngexesha lokuhamba kwakhona.

Zimanzise– Injongo yesi sigaba kukuqinisekisa ukuba onke amacandelo afikelela kwiqondo lobushushu elifunekayo ngaphambi kokungena kwinqanaba lokuphinda liphume.I-Soak idla ngokuhlala phakathi kwemizuzwana engama-60 kunye ne-120 ngokuxhomekeke 'kumahluko wobunzima' wendibano kunye neendidi zamalungu akhoyo.Okusebenzayo ngakumbi ukuhanjiswa kobushushu ngexesha lesigaba sokufunxa ixesha elincinci elifunekayo.

Ukuba iprofayili yokuphinda iphinde ibe nobushushu obaneleyo obusetyenzisiweyo ngexesha lenqanaba lokubuyela kwakhona kuya kubakho amakhonkco e-solder abonwayo afana nale mifanekiso ingezantsi: -

i-solder ayenzekanga i-fillet enelothe

Ayizizo zonke iibhola ezinyibilikayo

Isiphene esiqhelekileyo sokuthengisa emva kokuhamba kwakhona kukubunjwa kweebhola ze-solder eziphakathi kwe-chip / amaso njengoko kunokubonwa ngezantsi.Isisombululo sesi siphene kukuguqula uyilo lwe-stencil -iinkcukacha ezingaphezulu zinokubonwa apha.

Ukusetyenziswa kwe-nitrogen ngexesha lenkqubo yokubuyisela kwakhona kufuneka kuthathelwe ingqalelo ngenxa yendlela yokuhamba ukusuka kwi-solder paste equlethe i-fluxes enamandla.Umcimbi ngokwenene awukho ukukwazi ukugeleza kwakhona kwi-nitrogen, kodwa kunoko ukukwazi ukugeleza kwakhona ngokungabikho kwe-oxygen.Ukufudumeza i-solder phambi kwe-oksijini kuya kudala ii-oxides, ezidla ngokuba yimihlaba engabonakaliyo.

Ukupholisa– Eli linqanaba nje apho indibano ipholiswa khona kodwa kubalulekile ukuba indibano ingapholi ngokukhawuleza kakhulu – ngokuqhelekileyo izinga lokupholisa elicetyiswayo alifanele libe ngaphezu kwe-3ºC/sesibini.

PCB/Component Footprint Design

Kukho inani lemiba yoyilo lwePCB enefuthe kwindlela indibano eya kuphinda iphinde ihambe ngayo.Umzekelo ubunganga beengoma eziqhagamshelana necandelo lonyawo - ukuba umzila odibanisa kwelinye icala lecandelo lonyawo mkhulu kunomnye oku kunokukhokelela kukungalingani kwe-thermal okubangela ukuba indawo ibe 'kwilitye lengcwaba' njengoko kunokubonwa ngezantsi:-

Omnye umzekelo 'yi-copper balancing' - uninzi loyilo lwePCB lusebenzisa iindawo ezinkulu zobhedu kwaye ukuba i-pcb ifakwe kwiphaneli ukunceda inkqubo yokuvelisa inokukhokelela kukungalingani kubhedu.Oku kunokubangela ukuba indawo yolawulo ijike ngexesha lokuqukuqela kwakhona kwaye ke isisombululo esicetyiswayo kukongeza 'ukulinganisa ubhedu' kwiindawo zenkunkuma zephaneli njengoko kunokubonwa ngezantsi:-

'Yabona'Uyilo lokuVelisa'kwezinye izinto eziqwalaselwayo.

I-PCB eprintwe ngononophelo kusetyenziswa istensile eyilwe kakuhle

Amanyathelo enkqubo yangaphambili ngaphakathi kwendibano yokunyuka komphezulu abaluleke kakhulu kwinkqubo esebenzayo yokuphinda iphinde ithengise.Iinkqubo yoshicilelo lwe-solder pastengundoqo wokuqinisekisa idiphozithi engaguqukiyo ye-solder paste kwi-PCB.Nayiphi na impazamo kweli nqanaba iya kukhokelela kwiziphumo ezingafunekiyo kwaye ke ulawulo olupheleleyo lwale nkqubo kunyeuyilo lwe-stencil olusebenzayoiyafuneka.

Ukubekwa okuphindaphindiweyo kwamacandelo okunyuka komphezulu

Ukwahluka kokubekwa kwecandelo

Ukubekwa kwezixhobo zokuxhoma umphezulu kufuneka kuphindaphindwe kwaye ke umatshini othembekileyo, ogcinwe kakuhle kunye nokubeka uyimfuneko.Ukuba iipakethe zamacandelo azifundiswanga ngendlela echanekileyo kunokubangela ukuba inkqubo yombono koomatshini ingaboni inxalenye nganye ngendlela efanayo kwaye kuya kujongwa ukwahluka ekubekweni kwayo.Oku kuya kukhokelela kwiziphumo ezingahambelaniyo emva kwenkqubo ye-reflow soldering.

Iinkqubo zokubekwa kwecandelo zinokudalwa kusetyenziswa oomatshini bokuchola kunye nendawo kodwa le nkqubo ayichanekanga njengokuthatha ulwazi lwecentroid ngqo kwidatha yePCB Gerber.Rhoqo le datha ye-centroid ithunyelwa ngaphandle kwisoftware yoyilo yePCB kodwa ngamanye amaxesha ayifumaneki kwaye keinkonzo yokuvelisa ifayile ye-centroid evela kwidatha yeGerber inikezelwa yiNkqubo yeMount Mount.

Bonke oomatshini bokubekwa kwamacandelo baya kuba 'nokuChaneka kokuBeka' okucaciswe ngolu hlobo:-

35um (QFPs) ukuya 60um (iitshiphusi) @ 3 sigma

Kukwabalulekile ukuba umlomo wombhobho ochanekileyo ukhethelwe uhlobo lwecandelo eliza kubekwa - uluhlu lwemilomo yamacandelo ahlukeneyo anokubonwa apha ngezantsi:-

Umgangatho olungileyo we-PCB, amacandelo kunye ne-solder paste

Umgangatho wazo zonke izinto ezisetyenzisiweyo ngexesha lenkqubo kufuneka ube phezulu kuba nantoni na ekumgangatho ophantsi iya kukhokelela kwiziphumo ezingathandekiyo.Ngokuxhomekeke kwinkqubo yokwenziwa kwe-PCB kunye nendlela ezigcinwe ngayo ukugqitywa kwee-PCB kunokukhokelela kwi-solderabilty engalunganga ngexesha lenkqubo yokuphinda ithengise.Apha ngezantsi kukho umzekelo wento enokubonwa xa ukugqiba komphezulu kwi-PCB kungalunganga kukhokelela kwisiphene esaziwa ngokuba yi-'Black Pad':-

UMGANGATHO OLUNGILEYO PCB Gqiba

I-PCB EQHELEKILEYO

I-Solder iqukuqela ukuya kwicandelo hayi iPCB

Ngendlela efanayo umgangatho wecandelo lokunyuka komphezulu unokuba buthathaka ngokuxhomekeke kwinkqubo yokuvelisa kunye nendlela yokugcina.

Umgangatho we-solder paste uchaphazeleka kakhulu yiukugcinwa kunye nokuphatha.Intlama yesolder ekumgangatho ophantsi ukuba isetyenzisiwe inokunika iziphumo njengoko kunokubonwa ngezantsi:-