MLCC Cracking in PCBA: Ho Ikakhela ka botebo Lisosa, Thibelo, le Melao ea Moralo ea PCB

1. Selelekela: Hobaneng ha MLCC Cracking e le Kotsi e Bohlokoa ea ho Tšepahala

Ho qhetsoha ha MLCC ke e 'ngoe ea liphoso tse atisang ho etsahala khafetsa tlhahisong ea PCB. Liphoso tsena hangata li phonyoha tlhahlobo ea pele 'me li hlaha feela nakong ea potoloho ea mocheso, liteko tsa ho theoha, kapa tšebeliso ea tšimo, e leng se lebisang liphosong tse sa khaotseng, lerata la motlakase, phallo ea metsi a lutlang le meputso e turang.

Sengoliloeng sena se fana ka moralo o sebetsang oa ho khetholla le ho thibela ho phatloha ha MLCC. Ka ho utloisisa lisosa tsa eona le ho sebelisa taolo e netefalitsoeng ea moralo le ts'ebetso, baenjiniere ho pholletsa le moralo, tlhahiso le boleng ba ka ntlafatsa haholo ts'epahalo ea sehlahisoa le ho fokotsa litšenyehelo tse ka qojoang.

2. Tlhahlobo ea ho hloleha: MLCC Cracking ke Eng?

2.1 Flex Cracks (E Tlwaelehileng Haholo)

Flex cracks e theha ha PCB e kobeha e sebetsa khatello ea maikutlo ho MLCC. Hangata fractures tsena tse ka morao li qala ho fillet ea solder ebe li fetela 'meleng oa ceramic. Mabaka a tloaelehileng a kenyelletsa depanelization, ho ts'oaroa ka letsoho, deformation ea screw-mounting, kapa matla a ho kopanya a koaletsoeng.

2.2 Thermal Cracks (Reflow kapa CTE Mismatch)

Mapetso a mocheso a bakoa ke liphetoho tse potlakileng tsa mocheso kapa ho se lumellane ha CTE nakong ea phallo e ncha. Li hlaha e le mapetso a otlolohileng kapa a otlolohileng. Liprofaele tse sa nepahalang tsa phallo e ncha kapa ho futhumatsa sebakeng se itseng nakong ea ts'ebetso e ncha le tsona li ka baka mokhoa ona oa ho hloleha.

2.3 Mapetso a Bakoang ke ho sisinyeha (Mokhathala)

Ho thothomela ho ipheta-phetang ho ka baka mapetsong a mokhathala a tsoelang pele ho MLCC. Mokhoa ona o tloaelehile libakeng tsa likoloi, indastering le libakeng tse ling tse thothomelang haholo.

2.4 Matšoao a Motlakase a Li-MLCC tse Petsohileng

Mapetso a manyane a baka ho kheloha ha capacitance kapa keketseho ea ESR . Mapetso a mahareng a phahamisa phallo ea metsi a lutlang le ho fokotsa khanyetso ea ho thibela ho ruruha (IR). Mapetso a matla a ka baka lipotoloho tse khutšoane tse sa khaotseng kapa tse sa feleng, tse lebisang ho hloleheng ha sistimi kapa ts'ebetso e sa tsitsang.

3. Li-Vectors Tse Hlano tsa Khatello ea Maikutlo: Lisosa tsa Motso oa ho hloleha ha MLCC

Liphoso tsohle tsa MLCC tse qhekellang li bakoa ke ho feta mamello ea 'mele oa ceramic ho khatello ea mochini kapa ea mocheso. Ho utloisisa li-vectors tsena tsa khatello ea kelello ho thusa mekhoa ea thibelo e lebisitsoeng ho pholletsa le ketane ea tlhahiso.

3.1 PCB Flexing Nakong ea Tlhahiso

PCB flexing nakong ea depanelization e emela sesosa se ka sehloohong sa ho phatloha ha MLCC libakeng tsa tlhahiso. Karohano ea liphanele tsa V-cut le ts'ebetso ea ho pshatla matsoho e hlahisa ho kobeha ho feteletseng ha boto ho fetisang khatello ea maikutlo ka kotloloho 'meleng e thata ea ceramic. Teko e boima ea lisebelisoa ntle le tšehetso e lekaneng ea boto e eketsa kotsi ena, haholoholo ha lintlha tsa liteko li le hole le mapheo a liphanele.

3.2 SMT Khetha le ho Bea Khatello e Feteletseng

Mechini ea ho bea e sa sebetseng hantle kapa li-nozzles tse tsofetseng li sebelisa matla a mangata sebakeng sa heno nakong ea ho beoa ha likaroloana, haholo-holo tse bohlokoa bakeng sa boholo ba sephutheloana sa 0402 le 0201. Ho phatloha ha MLCC ho etsahala ha khatello ea nozzle e feta matla a ho hatella a ceramic, ho theha maqhetsoana a manyenyane a ata nakong ea liketsahalo tse latelang tsa mocheso kapa tsa mochini.

3.3 Reflow Soldering Thermal Stress

'Mele oa ceramic le substrate ea PCB li na le li-coefficients tse fapaneng tsa katoloso ea mocheso, li theha matla a ka hare a ho kuta nakong ea pholileng e potlakileng ea solder. Li-MLCC tse kholo (1206 le ka holimo) li na le khatello ea kelello e phahameng ka ho khetheha ka lebaka la boima ba tsona bo boholo ba mocheso le sebaka se seholoanyane sa solder, ho etsa hore ho phunyeha ha ceramic capacitor ho ka etsahala ha litekanyetso tsa ho pholisa li feta 3 ° C motsotsoana.

3.4 Ho sebetsa bocha ka letsoho le Solder e Feteletseng

Mocheso oa lehae, o sa laoleheng o sebelisoang nakong ea ts'ebetso ea ts'ebetso e fokolisa sebopeho sa ceramic ka ho ts'oha ha mocheso le mokhathala o bokelletsoeng. Bophahamo bo feteletseng ba solder bo baka likhokahano tse thata tse fetisang ho e-na le ho monya khatello ea maikutlo, ho felisa ts'ebetso ea ho imolla khatello ea maikutlo e fanang ka li-fillets tse entsoeng ka nepo khahlanong le ho phatloha ha MLCC.

3.5 Khatello ea Mosebelisi

Ho theoha ha sesebelisoa, ho tiisa ho feta tekano ka screw torque e feteletseng, le ho tenyetseha ha sehlahisoa nakong ea ts'ebeliso e tloaelehileng ea lebala ho emela vector ea ho qetela ea khatello. Lisebelisoa tsa elektroniki tsa bareki le lisebelisoa tse nkehang habonolo li tobane le kotsi e kholo haholo, kaha lipotoloho tse pheta-phetoang tsa mochini li potlakisa ho ata ha crack likarolong tse seng li ntse li imetsoe ho tloha tšebetsong ea tlhahiso.

4. Tšireletso ea Phato ea Kopano: Ts'ebetso le Litharollo tsa QA ho Felisa MLCC Cracking

Taolo ea ts'ebetso ea tlhahiso e fana ka mokhoa oa pele oa ts'ireletso khahlanong le ho phatloha ha ceramic capacitor. Ho kenya ts'ebetsong lintlafatso tsa ts'ebetso tse lebisitsoeng ho pholletsa le ts'ebetso ea depanelization, ho bea, le ts'ebetso ea phalliso ho fokotsa haholo sekhahla sa ho hloleha.

4.1 Mekhoa e Metle ea ho Hlabolla

Ho qoba li-V-cuts tse tebileng haufi le likarolo tse kholo le ho fetela ho karohano e thehiloeng ho router ho fokotsa ho fetoha ha boto nakong ea karohano ea liphanele. Li-routers li baka khatello e tlase haholo ho feta ho kuta kapa ho senya, ho fokotsa kotsi ea ho phatloha ha MLCC ka 80% lithutong tse laoloang. Ho ts'ehetsa likhahla tsa PCB tse nang le lisebelisoa tse hlophisitsoeng hantle nakong ea depanelization ho thibela ho kheloha ha setsi ho fetisang khatello ho likarolo.

4.2 SMT Placement Taolo ea Khatello

Ho etsa bonnete ba hore matla a matla a nozzle a lula a le ka har'a litlhaloso (hangata 1-3 Newtons) le ho kenya ts'ebetsong ts'ebetso ea ho netefatsa ho thibela khatello e feteletseng ea ho behoa. Sistimi ea ho lekanya bophahamo ba othomathike e lemoha li-nozzles tse tsofetseng mme e thibela ho phatloha ha MLCC ho tsoa moroalo o boima, ho bohlokoa haholo ha boholo ba sephutheloana bo fokotseha le 'mele ea ceramic e senyeha habonolo.

4.3 Reflow Profile Optimization

Ho ntlafatsa sekhahla sa ho pholisa ho lumella ho lokolloa ha khatello butle butle ha kopano e khutlela mochesong oa tikoloho, ho fokotsa ho phatloha ho bakoang ke mocheso oa ceramic capacitor. Likarolo tse kholo (1210 le tse kholoanyane) li rua molemo mehatong e atolositsoeng ea ho futhumatsa pele e fokotsang li-gradients tsa mocheso ho pholletsa le 'mele oa ceramic, ho boloka khatello e phahameng ka tlase ho menyako ea fracture.

4.4 Litaelo tsa ho sebetsana le ho sebetsa bocha

Ho fokotsa sekhahla sa rework ka ho ntlafatsa chai ea pele ho felisa lipotoloho tse bokelletsoeng tsa khatello ea maikutlo. Ha rework e ba ho hlokahala, preheating lipoleiti fokotsa mogote gradients pele ho kopo soldering tšepe mocheso, ho thibela localized makala mogote e bakang MLCC cracking likarolong tse ling bophelo bo botle.

5. Sehlomathiso sa Moqapi: Litaelo tsa Moralo bakeng sa Phomolo ea Khatello

Liqeto tsa sebopeho sa PCB li etsa qeto ea mantlha ea hore MLCC e ka ba le ts'oaetso. Ho kenya ts'ebetsong melao ea moralo oa ho imolla khatello ea maikutlo nakong ea mohato oa moralo ho thibela ho hloleha ka katleho ho feta taolo efe kapa efe ea ts'ebetso e tlase.

5.1 Beha MLCC Perpendicular to Board Flex Direction

Ho hokahanya bolelele ba 'mele oa capacitor ka ho otloloha ho ea ka lehlakoreng le lelelele la boto kapa tataiso e tsebahalang ea ho thekesela ho tsamaisa khatello ho latela boholo bo bokhutšoanyane le bo matla ba karolo. Molao ona o bonolo oa ho shebana o fokotsa kotsi ea ho petsoha ha capacitor ea ceramic ka 60% ha ho bapisoa le ho hokahanya ho tsamaellanang, kaha karolelano ea 'mele oa ceramic e hlahisa litšobotsi tsa matla a fapaneng.

5.2 Sebelisa Parallel Arrays sebakeng sa Single Large MLCCs

Ho fetola capacitor e le 'ngoe e kholo (joalo ka 1 × 22µF, 1206) ka tse nyane tse ngata (tse kang 2 × 10µF, 0603) e aba khatello ea mocheso le ea mechine likarolong tse ngata ha e ntse e ntlafatsa ts'ebetso ea DC-bias. Mekhatlo e menyenyane ea ceramic e na le mamello e phahameng ea khatello ea maikutlo ho latela bophahamo ba eona, e leng se etsang hore ho phatloha ha MLCC ho fokotsehe tlas'a maemo a tšoanang a ho palamisa.

5.3 Beha MLCC hole le Lintlha tsa Khatello ea Maikutlo

Ho boloka tumello ea bonyane ba 5mm ho tloha ho V-cuts, likoti tsa screw, li-slots tse ntseng li hola, le likarolo tsa boto ho thibela phetiso ea khatello ea maikutlo ho 'mele ea ceramic. Li-tab tse khaotsoeng le likanale tsa ho tsamaisa liphanele li theha libaka tse phahameng haholo tsa khatello ea maikutlo tse netefatsang ho phatloha ha MLCC ha likarolo li behiloe haufi.

5.4 Eketsa Sebaka sa Naha le Taolo ea Fillet ea Solder

Ho rala lipaterone tse kholoanyane tsa mobu ho etsa hore likhoele tsa solder tse matla, tse bopehileng joaloka cove tse sebetsang joalo ka litšitiso tsa khatello lipakeng tsa 'mele o thata oa ceramic le PCB e feto-fetohang. Geometry e nepahetseng ea fillet e monya khatello ea kelello ka mokhoa o laoloang, ho thibela phetiso ea khatello e tobileng e bakang ho phatloha ha ceramic capacitor.

5.5 Nahana ka Soft Termination MLCCs

Bakeng sa lits'ebetso tse ts'eptjoang haholo kapa tse nang le khatello e phahameng ea maikutlo ho kenyelletsa likoloi le sefofane, ho hlakisa li-MLCC tse nang le likarolo tsa polymer nakong ea ho felisoa ho fana ka monyetla o eketsehileng oa khatello ea maikutlo. Likarolo tse bonolo tsa ho emisa li fokotsa kotsi ea ho phatloha ha MLCC ka 70% tlhahlobong ea boto ea flex ha e bapisoa le ho felisoa ka thata, ho lokafatsa litšenyehelo tsa bona tsa premium lits'ebetsong tsa bohlokoa.

6. Ho netefatsa le ho Vetting: Liteko Protocols bakeng sa Crack-Free Reliability

Liteko tse felletseng tsa liteko li netefatsa khanyetso ea MLCC pele lihlahisoa li fihla ho bareki. Ho kenya ts'ebetsong tlhahlobo ea mekhahlelo e mengata le tlhahlobo ea khatello ea maikutlo ho fumana ho hloleha nakong ea netefatso e laoloang ho fapana le ho khutlisa masimo a theko e boima.

6.1 Tlhahlobo e sa Senyeheng

Tlhahlobo ea X-ray e fana ka netefatso ea bohlokoa ea botšepehi ba sebopeho bakeng sa manonyeletso a solder le ho lemoha mapetso a ka hare, haholo-holo e tlamang bakeng sa merero e tšepahalang haholo moo ho hloleha ha ho petsoha ha capacitor ea ceramic ho nang le liphello tse mpe. Tlhahlobo ea pono e tlatsa X-ray ka ho hlahloba sebopeho sa fillet le ho khetholla solder e feteletseng e hlahisang litsela tse thata tsa phetisetso ea khatello.

6.2 Mekhoa ea Teko ea Motlakase

Ho beha leihlo khanyetso ea insulation (IR) le ho lutla ha hona joale ho senola ho phatloha ho honyane ha MLCC pele ho hloleha ha koluoa. Ho fokotseha ho honyenyane ha IR kapa ho lutla ha metsi ho bontša hore crack e ntse e ata, e leng se nolofalletsang ho kena lipakeng ka ho fetola likaroloana nakong ea tlhahiso ho e-na le ho ba tšebeletsong ea tšimo.

6.3 Boto ea Flex Stress Testing

Ho kenya ts'ebetsong litekanyetso tsa tlhahlobo tsa IPC-9702 board flex ho netefatsa moralo le ho beoa ha likarolo tlas'a maemo a laoloang a khatello. Teko e nang le lintlha tse tharo e tiisa hore ho phatloha ha ceramic capacitor bakeng sa meralo e itseng ea boto, e nolofalletsang moralo pele o itlama ho hlahisa molumo.

7. Kakaretso le Likhothaletso tse Sebetsang

Boiphihlelong ba ka, sesosa se ka sehloohong sa ho phatloha ho hoholo ha MLCC ke khatello e sa laoleheng ea mochini kapa mocheso. Ho thibela mefokolo ena ho hloka ho ts'oara ts'epo ea MLCC e le taba ea boemo ba sistimi-e laoloang ka khetho ea moralo, mekhoa ea kopano, le taeo ea tlhahlobo.

• Orient MLCCs perpendicular to the primary flex direction ea PCB. Ke bone phetoho ena e bonolo ea ho bea e fokotsa haholo mapetsong a flex-induced, haholo-holo libotong tse nang le lisebelisoa tsa mochini kapa tse sebetsanang ka letsoho.
• Sebelisa lihlopha tse bapileng tsa li-MLCC tse nyane ho fapana le capacitor e le 'ngoe e kholo. Ho ipapisitsoe le litlhahlobo tse ngata tsa ho hloleha tseo ke sebelitseng ho tsona, li-capacitor tse nyane li tsamaisa khatello ea maikutlo hamolemo ho feta 'me li mamella ho kobeha.
• Qoba V-cut depanelization haufi le likarolo tse bobebe. Ho tsoa ho seo ke se boneng mokatong oa tlhahiso, V-cuts e lula e hlahisa khatello e phahameng ka ho fetisisa nakong ea ho bina. Depanelization e thehiloeng ho router e hlahisa linyeoe tse fokolang haholo.
• Boloka liprofaele tse laoloang tsa mocheso oa phalliso. Ho futhumatsa ka potlako kapa ho pholile ke selelekela se tloaelehileng sa mapetsong a mocheso. Boemo bo tsitsitseng, bo nang le litšobotsi tse ntle bo fokotsa kotsi ena haholo.
• Fokotsa ho sebetsana le boto le ho kobeha ho sa laoleheng nakong ea kopano. Ho theosa le lilemo, ke fumane hore meroalo e menyenyane, e pheta-phetoang hangata e etsa li-microcracks tse hlahang feela nakong ea tlhahlobo ea ho tšepahala.

Ho sebelisa mehato ena khafetsa ho pholletsa le moralo, tlhahiso, le taolo ea boleng ho ipakile e le mokhoa o tšepahalang ka ho fetesisa oa ho fokotsa ho phatloha ha MLCC le ho thibela litaba tsa ts'epo.