I-Common Capacitor Failure Modes ku-PCB Design kanye ne-Assembly

Isingeniso

Ama-capacitor enza imisebenzi ebalulekile kumasekethe e-PCB, kusukela ekuhlungeni umsindo kanye nokuhlukanisa izinsiza zamandla kuya ekugcineni amandla okusebenza kwe-pulse. Naphezu kobuchwepheshe obuvuthiwe kanye nokutholakala kabanzi, izindlela zokwehluleka kwe-capacitor zisalokhu ziyinkinga enkulu yokuthembeka ethinta ngqo ukusebenza komkhiqizo kanye nobude besikhathi sensimu.

Lesi sihloko sihlola izindlela eziyinhloko zokuhluleka kwe-capacitor, izimbangela zazo, kanye namasu okuvimbela afakazelwe athuthukisa ukwethembeka kwama-PCB capacitor kuwo wonke ukukhiqiza nokusatshalaliswa.

Ukuqonda Izindlela Zokwehluleka Kwe-Capacitor

Izinhlobo ze-Capacitor Degradation

Ukwehluleka kwe-Capacitor kwenzeka lapho izingxenye zingasahlangabezani namapharamitha kagesi acacisiwe, okubonisa ngamaphethini ahlukile adinga izindlela zokuxilonga ezihlukene. Ukwehluleka okuyinhlekelele kukhiqiza amasekhethi avulekile noma amafushane amisa ukusebenza kwesistimu. I-Parametric drift idala ukuchezuka kwezicaciso kancane kancane, kwehlisa isithunzi ngaphandle kokwehluleka okuphelele. Ukwehluleka ngezikhathi ezithile kubonakala kuphela ngaphansi kwezimo ezithile, okubenza kube inselele ikakhulukazi ukuxilonga ngesikhathi sokuhlolwa okujwayelekile.

Umthelela ekuthembekeni kwe-PCB Capacitors

Imodi yokwehluleka ngakunye idala imiphumela yesekethe eyingqayizivele. Amasekhethi avuliwe aphazamisa izindlela zesignali, kuyilapho amasekhethi amafushane alimaza izingxenye ezizungezile. Ukulahlekelwa amandla kancane kancane kwehlisa ukusebenza kwesihlungi nokunemba kwesikhathi. I-ESR ephakeme inciphisa ukusebenza kahle futhi ihlanganisa ukucindezeleka okushisayo kuma-capacitor. Ukuqonda le taxonomy kunika amandla ukuhlaziya ukwehluleka okusebenzayo ezinqubweni ze-PCBA kanye namaphrothokholi ahlosiwe wokuqinisekisa ikhwalithi.

I-Common Capacitor Failure Modes ngohlobo

Ukuhluleka kwe-Ceramic Capacitor

Ama-capacitor e-ceramic ahluleka kakhulu ngokwakhiwa kwemifantu yemishini okuphazamisa ubuqotho be-dielectric. Isakhiwo se-capacitor ye-ceramic enezingqimba eziningi (MLCC) sibonakala sisengozini enkulu yokulimala okubangelwa ukucindezeleka. Izindlela zokwehluleka zifaka:

• Ukushaqeka okushisayo ngesikhathi sokugeleza kabusha - Ukushintsha kwezinga lokushisa okusheshayo kudala ama-gradients engcindezi ngaphakathi kwezendlalelo ze-ceramic dielectric
• PCB flexure stress - Ukugoba kwebhodi ngesikhathi sokuphatha noma ukuhlukaniswa kudala ubunzima bemishini emizimbeni eqinile yobumba
• Ukusabalalisa kwe-Microcrack - Amaphutha okuqala akhula ngaphansi kwengcindezi kagesi eqhubekayo, ekugcineni abangele ukuwohloka noma amasekethe amafushane

Imifantu ingase ihlale ithule ekuqaleni kodwa isakazeke empilweni yokusebenza, ikakhulukazi uma ihlanganiswe nengcindezi kagesi kanye nokuhamba ngebhayisikili okushisayo.

Izinkinga Zokwethenjwa ze-Tantalum Capacitor

Ama-capacitor e-Tantalum abonisa ukwehluleka okungazelelwe kwe-short-circuit okuvame ukukhuphukela ekushiseni ngenxa yobuningi bamandla aphezulu. I-tantalum pentoxide dielectric yonakala ngokushesha ngaphansi kokusetshenziswa kabi kukagesi. Izinto ezibangela ukwehluleka okukhulu zifaka:

• Buyela emuva polarity - Ngisho ne-reverse voltage yesikhashana ibhubhisa ubuqotho bongqimba lwe-oxide unomphela
• Ama-voltage adlulayo - Izipikili ezidlula imikhawulo elinganiselwe zidala izindlela ezisebenzayo ngokusebenzisa i-dielectric esengozini
• Amaphutha okukhiqiza - Ukufakwa noma ama-voids esakhiweni se-tantalum pellet kunikeza amasayithi okuqalisa ukwehluleka

Uma kwenzeka ukwehluleka, ukukhululwa kwamandla agxilile kuvame ukubangela ukuthungela. Ukusebenza okuhle kwemboni kuncoma ukusebenza ku-50-60% wevoltheji elinganiselwe yokuthembeka kwe-tantalum capacitor.

I-Electrolytic Capacitor Failure Mechanisms

Ama-electrolytic capacitor ehlisa ngokuyinhloko ngokuhwamuka kwe-electrolyte, ashesha kakhulu ngezinga lokushisa elilandela ubuhlobo be-Arrhenius. Ukwenyuka kwezinga lokushisa elingu-10°C kuvamise ukuba yingxenye yokuphila okulindelekile. Izindlela eziyinhloko zokunciphisa zihlanganisa:

• I-Electrolyte yomile - Ukuhwamuka ngokusebenzisa izimpawu kunciphisa ionic conductivity futhi kwandisa ukumelana
• Ukuwohloka kwesendlalelo se-oxide - I-ripple yamanje noma i-reverse voltage ilimaza i-aluminium oxide dielectric
• Ukwehliswa kwesithunzi - Ukulahlekelwa uphawu lwe-hermetic kuvumela ukungena komswakama, kusheshise ukugqwala kwangaphakathi

Ukuqunjelwa okubonakalayo, ukuvuza kwe-electrolyte, noma ukukhishwa kwe-vent cap kubonisa ukwehluleka okuthuthukisiwe kwe-electrolytic capacitor.

Izimbangela Zokuhluleka Kwe-Capacitor

I-Electrics Stress Factors

I-voltage esebenzayo uma iqhathaniswa nezilinganiso ibusa izimbangela zokuhluleka kukagesi. Ukusebenza okuqhubekayo ngaphezu kwama-80% wamandla kagesi alinganisiwe kusheshisa ukuwohloka kwe-dielectric. I-Ripple current ikhiqiza ukushisa kwangaphakathi ngokulahleka kwe-ESR, ikakhulukazi izinhlobo ze-electrolytic ezilimazayo lapho imiphumela eshisayo i-evaporation ehlanganisiwe. Ukwehla kwamandla kagesi okuphumelelayo ku-50-70% wezicaciso ezilinganiselwe kwandisa impilo yengxenye ngezici ze-3-10× kuye ngobuchwepheshe namazinga okucindezeleka.

I-Thermal Stress kuma-Capacitors

Izinga lokushisa lisheshisa ngokuqondile ukuwohloka kwamakhemikhali futhi andise imisinga yokuvuza. Izimo eziphakeme ze-ambient zicindezela kakhulu izinhlobo ze-electrolytic, kuyilapho ukuhamba ngebhayisikili okushisayo kulimaza ama-capacitor e-ceramic ngokunwetshwa okuhlukile. Ukuphathwa okushisayo kwe-PCB okunganele kudala izindawo ezishisayo zendawo, kunciphisa kakhulu isikhathi sokuphila. Ukwehliswa ngakunye ngo-10°C kwezinga lokushisa lokusebenza cishe kuliphinda kabili ubude bempilo ye-electrolytic capacitor.

Izinto Zemishini Nezemvelo

Ukucindezelwa kwemishini ngesikhathi sokuhlanganiswa, ikakhulukazi kusuka ekuhlukaniseni nasekuhlanganisweni kwamagagasi, kubangela ukuguquguquka okuqhekeza amaphakheji e-ceramic. Ukudlidliza ezindaweni zezimoto noma zezimboni kudala ukulayisha okujikelezayo okuholela ekuhlulekeni kokukhathala. Umswakama ophezulu ukhuthaza ukuvuza kwe-electrolyte kanye nokugqwala kwe-terminal. Izingcindezi zomshini nezemvelo ezihlanganisiwe zivame ukukhiqiza ukuwohloka okusheshayo kunokubikezela izici zomuntu ngamunye.

Ukuvimbela Izindlela Zokuhluleka kwe-Capacitor ku-PCB Design

I-Design Phase Prevention Strategies

Ukukhethwa kwezingxenye ngokusekelwe ezimweni zokusebenza zangempela kwakha isisekelo sokuthembeka. Ukusebenzisa iziqondiso zokunciphisa i-voltage kunikeza imingcele yokuphepha ngokumelene nokuguquguquka kanye nokubekezelelana. Ukuhlelwa kwe-PCB kuthinta ukuphathwa kokushisa ngokubekwa kwethusi, izikhala zezingxenye ezivela emithonjeni yokushisa, kanye nokwenza ngcono ukuhamba komoya. Ukubekwa okufanele kokuhlukanisa kanye nomklamo wendiza yomhlabathi kunciphisa ukucindezeleka kukagesi ngokulawula izindlela zamanje.

Izilawuli Zenqubo Yokukhiqiza

Ukuthuthukiswa kwephrofayela yokugeleza kabusha kuvimbela ukushaqeka okushisayo ngokulawula amazinga okushisa ngaphakathi kwezicaciso zomkhiqizi, ngokuvamile kukhawula amarempu abe ngu-2-3°C/ngesekhondi ezinhlotsheni zobumba ezibucayi. Izinqubo zokuphatha ze-PCB zinciphisa ukuguquguquka ngesikhathi sokuhlangana. I-conformal coating ivikela umswakama kanye nokungcola. Ukuhlola okungenayo, ukuqinisekiswa kwesifunda, nokuhlola ukuphila okusheshisiwe kusungula izisekelo zekhwalithi futhi kuhlonze ukukhukhuleka kwenqubo ngaphambi kokuthunyelwa kwenkambu.

Ukuhlonza Izimpawu Zokuhluleka Kwe-Capacitor

Izindlela Zokuhlola Okubonakalayo Nezikagesi

Ukuhlolwa ngokomzimba kuveza izinkomba zokwehluleka ngaphambi kokuhlukana okuphelele. Bheka ukushintsha kombala kumatheminali aphakamisa ukushisa ngokweqile, ukugcwala kwekesi ngezinhlobo ze-electrolytic, kanye nokuqhekeka okubonakalayo kumaphakheji e-ceramic. Isilinganiso se-ESR esingaphakathi kwesifunda sisebenzisa abahlaziyi be-impedance sibonisa ukucekelwa phansi ukuhlolwa okumile okugejayo. Ukuchezuka okungaphezu kuka-±20% kusuka kumanani e-ESR okuzisholo ngokuvamile kubonisa ukuthi sekusondele ukuphela kwempilo.

Ukuhlola Ukusebenza Okusebenzayo

Ukuhlolwa kokusebenza ngaphansi kwezimo zomthwalo kuveza ukwehluleka ngezikhathi ezithile ukuhlolwa kwebhentshi okungakunaki. Izimbangela ezivamile zokwehluleka kwe-capacitor kuma-electronics ziveza njengokukhuphuka komsindo wesitimela samandla, ukuncipha kokuphumelela kwesihlungi, noma ukuhluka kwesikhathi kumanethiwekhi e-RC. Ukucabanga okushisayo ngesikhathi sokusebenza kuthola amaphethini okushisa angavamile aphakamisa i-ESR ephakeme noma i-ripple current eyeqile.

Isiphetho

Amaphethini Okwehluleka Okubikezelwayo

Ezinkulungwaneni zezinhlangano ze-PCB e-Highleap Electronics, ukwehluleka kwe-capacitor kulandela amaphethini abikezelwayo lapho izimbangela zembangela zingaxazululwa. Izinhlobo ezahlukene ze-capacitor zidinga amasu okuvikela ahlukile; yiziphi izindlela zokuvikela ama-capacitor e-ceramic angase angasebenzi kuzo izinhlobo ze-electrolytic noma ze-tantalum.

Umthelela Wokuphatha Okushisayo

Ukuphathwa kwe-thermal kuthinta kakhulu impilo ende ye-capacitor. Ukulungiswa okulula kwesakhiwo okwehlise izinga lokushisa lengxenye ngo-15°C kwanweba impilo yasensimini kusukela eminyakeni emibili kuya kweyisikhombisa. Imithetho eqinile yokwehlisa amandla kagesi iphinde yaqeda ukwehluleka kwe-tantalum ngaphambi kwesikhathi emikhiqizweni yezimoto.

Indlela Yokuvimbela Ehlelekile

Indlela ephumelela kakhulu ihlanganisa amamajini edizayini kagesi alandelanayo nezilawuli zokukhiqiza ukuvimbela umonakalo odalwe ukuhlanganisa. Izinyathelo zihlanganisa ukuhlola okuzenzakalelayo kokubona ama-microcracks e-ceramic capacitor kanye nephrofayili eshisayo ukuze kuqinisekiswe ukugeleza kabusha okunembayo. Lezi zinqubo zehlise ukwehluleka kwenkambu okuhlobene ne-capacitor ngama-87% eminyakeni emithathu.