Hauv thaj tsam ntawm siab - zaus thiab siab - circuits ceev, cov yam ntxwv impedance ntawm PCB ncaj qha txiav txim siab ncaj ncees thiab ruaj khov ntawm cov teeb liab kis tau tus mob. Impedance mismatch tuaj yeem ua rau muaj teeb meem xws li teeb liab kev xav, attenuation, crosstalk, thiab nyob rau hauv cov xwm txheej hnyav, txawm tias ua rau tsis ua hauj lwm ntawm tag nrho cov kab hluav taws xob. Yog li ntawd, PCB impedance tswj tshuab tau dhau los ua qhov txuas tseem ceeb los xyuas kom meej tias qhov kev ua tau zoo ntawm high - zaus thiab siab - circuits ceev.
1, Kev nkag siab yooj yim ntawm pcb impedance tswj
Lub hom phiaj tseem ceeb ntawm kev tswj hwm impedance yog ua kom tus yam ntxwv impedance ntawm pcb kis tau tus mob raws li impedance ntawm cov cuab yeej txuas nrog ntawm ob qho kawg, txhawm rau txo qis zog poob thiab cuam tshuam ntawm cov teeb liab thaum sib kis. Cov yam ntxwv impedance tsis yog ib qho kev tiv thaiv tus nqi, tab sis ib qho nyuaj impedance txiav txim siab los ntawm kev faib tawm tsis kam, faib cov peev txheej, thiab faib inductance ntawm cov kab sib kis. Nws qhov loj me yog ze ze rau cov qauv ntawm lub cev, cov yam ntxwv ntawm cov khoom siv, thiab cov txheej txheem thev naus laus zis ntawm pcb.
Nyob rau hauv siab - zaus thiab siab - cov xwm txheej ceev (xws li 5G kev sib txuas lus, servers, aerospace electronics, thiab lwm yam), lub wavelength ntawm lub teeb liab yog luv luv, thiab qhov cuam tshuam ntawm kev faib khoom ntawm cov kab sib kis ntawm cov teeb liab tau nrawm dua. Lub impedance tswj qhov tseeb cov cai yog siab heev, thiab nyob rau hauv ib co hnyav scenarios, cov neeg yuav tsum tau nruj me ntsis, uas tso siab heev xav tau ntawm cov txheej txheem tom ntej.
2, Core influencing yam: cov khoom siv thiab cov yam ntxwv tsis
(1) Xaiv cov substrate thiab tooj liab -clad txheej
Lub substrate thiab tooj liab ntawv ci yog cov khoom siv tseem ceeb uas txiav txim siab qhov impedance yam ntxwv ntawm pcb, thiab lawv cov kev ua tau zoo tsis cuam tshuam ncaj qha rau impedance tswj qhov tseeb.
Dielectric qhov tsis tu ncua ntawm substrate: Dielectric qhov tsis tu ncua yog ib qho tseem ceeb ntawm cov substrate, thiab cov yam ntxwv impedance yog inversely proportional rau lub square root ntawm dielectric tas li. Kev hloov pauv me me hauv dielectric tas li tuaj yeem ua rau qhov hloov pauv impedance. Lub dielectric qhov tsis tu ncua ntawm ntau hom substrates sib txawv heev, thiab tsis tshua muaj dielectric tas li substrates feem ntau yog siv nyob rau hauv siab - zaus thiab siab - ceev xwm txheej, uas yog tsim nyog rau tsawg poob teeb liab kis tau tus mob. Hauv kev siv cov tswv yim, nws yog ib qho tsim nyog los xaiv lub substrate nrog ruaj khov dielectric tas li thiab tsis tshua muaj kub coefficient raws li kev khiav hauj lwm zaus ntawm Circuit Court, kom tsis txhob muaj kev hloov pauv hauv dielectric tas li los ntawm ib puag ncig kub hloov, uas yuav cuam tshuam rau impedance stability.
Lub thickness thiab roughness ntawm tooj liab ntawv ci: Lub thickness ntawm tooj liab ntawv ncaj qha cuam tshuam rau kev faib tsis kam ntawm cov kab sib kis. Qhov me me thickness, qhov loj dua qhov kev faib tawm, thiab qhov tseem ceeb tshaj qhov cuam tshuam ntawm impedance. High zaus thiab siab - ceev luam ntawv Circuit Court boards feem ntau siv nyias tooj liab ntawv ci los txo cov teeb liab poob los ntawm cov tawv nqaij. Lub caij no, qhov roughness ntawm tooj liab ntawv tseem tuaj yeem cuam tshuam cov teeb liab kis tau tus mob. Qhov loj dua qhov kev ntxhib los mos, qhov hnyav dua qhov tawg ntawm lub teeb liab thaum lub sij hawm kis tau tus mob, tshwj xeeb tshaj yog nyob rau hauv siab - zaus scenarios. Qhov cuam tshuam ntawm qhov roughness ntawm impedance tsis tuaj yeem tsis quav ntsej. Yog li ntawd, nws yog ib qho tsim nyog yuav tau xaiv electrolytic tooj liab ntawv ci los yog dov tooj liab ntawv ci nrog tsawg nto roughness los xyuas kom meej impedance stability.
(2) Kev tswj xyuas qhov tseeb ntawm cov kab sib txuas cov qauv tsis zoo
Lub cev tsis sib xws ntawm cov kab kis tau tus mob yog lub hauv paus txiav txim siab cov yam ntxwv impedance, feem ntau suav nrog kab dav, kab sib nrug, thiab dielectric thickness (qhov kev ncua deb ntawm kab sib kis thiab lub dav hlau siv). Cov qauv sib txawv ntawm cov kab sib txuas (xws li cov kab microstrip, kab strips, thiab cov kab sib txawv) yuav tsum muaj kev tswj xyuas meej rau qhov sib txawv.
Microstrip kab: Microstrip kab yog ib qho kev sib kis kab qauv nyob rau saum npoo ntawm pcb, muaj cov teeb liab kab, substrate (dielectric txheej), thiab ib tug siv dav hlau (hauv av los yog lub hwj chim txheej) hauv qab no. Nws cov yam ntxwv impedance feem ntau muaj feem xyuam rau txoj kab dav, dielectric thickness, thiab substrate dielectric tas li. Hauv cov txheej txheem tsim khoom, kev tswj xyuas qhov tseeb ntawm kab dav thiab dielectric thickness yog siab heev, txwv tsis pub nws yooj yim ua rau impedance hloov thiab tshaj qhov raug.
Ribbon kab: Cov kab ribbon nyob hauv pcb thiab yog qhwv los ntawm ob lub dav hlau siv. Cov kab teeb liab yog ib puag ncig los ntawm cov txheej dielectric, thiab nws cov yam ntxwv impedance tsis yog tsuas yog cuam tshuam rau txoj kab dav thiab substrate dielectric tas li, tab sis kuj mus rau qhov kev ncua deb ntawm lub sab sauv thiab qis siv dav hlau thiab qhov kev ncua deb ntawm cov teeb liab kab thiab sab sauv siv dav hlau. Vim tias tag nrho cov ntaub qhwv cov kab sawb los ntawm dielectric txheej, lub teeb liab tsis tshua muaj cuam tshuam los ntawm kev cuam tshuam sab nraud, tab sis qhov nyuaj ntawm kev tswj cov thickness ntawm dielectric txheej thaum lub sij hawm tsim khoom yog ntau dua. Nws yog tsim nyog los xyuas kom meej lub uniformity ntawm lub thickness ntawm lub dielectric txheej tom qab lamination kom tsis txhob impedance offset tshwm sim los ntawm uneven thickness.
Cov kab sib txawv: Ib txoj kab sib txawv muaj ob lub teeb liab kab sib txuas, uas txo cov hom kev cuam tshuam los ntawm kev sib txawv ntawm cov teeb liab sib txawv. Nws impedance tswj muaj xws li cov yam ntxwv impedance (ib zaug kawg impedance) thiab txawv impedance (impedance ntawm ob lub teeb liab kab). Differential impedance feem ntau muaj qhov sib npaug sib npaug nrog ib qho kawg impedance, feem ntau cuam tshuam nrog kab dav, kab sib nrug, thiab dielectric thickness. Kev tswj qhov tseeb ntawm kab sib nrug yog nruj me ntsis yuav tsum tau. Yog tias qhov sib txawv ntawm cov kab sib txawv loj dhau lawm, nws yuav ua rau qhov sib txawv impedance mus rau qhov sib txawv ntawm cov nqi teeb tsa, cuam tshuam rau kev ncaj ncees ntawm cov teeb liab sib txawv.
3, Ntsiab Cai Tswj Tshuab: Txheej Txheem Ua Haujlwm Zoo
Cov txheej txheem tsim khoom pcb yog cov kauj ruam tseem ceeb hauv kev hloov cov khoom tsis zoo rau hauv cov khoom tiag, los ntawm cov txheej txheem txiav, lamination, duab hloov mus rau etching, solder mask txheej. Txhua kauj ruam ntawm cov txheej txheem tuaj yeem cuam tshuam qhov tseeb ntawm impedance thiab yuav tsum muaj kev tswj xyuas meej kom ntseeg tau tias impedance stability.
(1) Precise tswj txheej txheem lamination
Cov txheej txheem lamination yog txheej txheem ntawm laminating ntau txheej txheej ntawm substrate thiab tooj liab ntawv ci rau hauv ib qho, ncaj qha txiav txim siab qhov sib xws thiab ruaj khov ntawm dielectric thickness, thiab yog ib qho ntawm cov txheej txheem tseem ceeb rau kev tswj impedance.
Kev sib koom ua ke ntawm kev tswj lub siab thiab qhov kub thiab txias: tsim nyog lub siab thiab qhov kub ntawm qhov nkhaus (qhov kub ntawm qhov ntsuas kub, qhov ntsuas kub ntawm lub rwb thaiv tsev, lub sij hawm rwb thaiv tsev) yuav tsum tau teeb tsa raws li cov yam ntxwv ntawm lub substrate thaum lub sij hawm lamination. Yog tias lub siab tsis txaus, tej zaum yuav muaj qhov sib txawv ntawm cov substrate thiab cov ntawv ci tooj liab, uas ua rau qhov tsis sib xws ntawm qhov nruab nrab; Yog tias qhov kub thiab txias dhau los yog lub sijhawm rwb thaiv tsev ntev dhau lawm, lub substrate yuav raug kho ntau dhau, ua rau muaj kev hloov pauv hauv dielectric tas li thiab cuam tshuam rau impedance. Kev saib xyuas lub sijhawm tiag tiag yuav tsum tau ua kom ntseeg tau tias qhov ntsuas kub thiab siab sib txawv yog tswj tau nyob rau hauv qhov tsim nyog.
Alignment tswj ntawm lamination: Thaum laminating ntau- txheej luam tawm Circuit Court boards, kev sib dhos ntawm txhua txheej cov kab sib txuas nrog lub dav hlau siv ncaj qha cuam tshuam rau qhov sib xws ntawm qhov nruab nrab tuab. Yog tias qhov sib txawv ntawm qhov sib txawv loj dhau lawm, nws yuav ua rau lub dielectric thickness nyob rau hauv qee qhov chaw ua thinner los yog thicker, ua rau lub zos impedance offset. Yog li ntawd, siab -cov cuab yeej muab qhov tseeb yuav tsum tau siv los xyuas kom meej tias qhov kev sib txawv ntawm cov lamination yog tswj nyob rau hauv qhov tsim nyog. Nyob rau tib lub sijhawm, tom qab lamination, kev sib haum xeeb ntawm cov txheej yuav tsum tau kuaj xyuas los ntawm cov cuab yeej kuaj kev tshaj lij kom tshem tawm cov khoom tsis tsim nyog.
(2) Txhim kho cov duab hloov pauv thiab cov txheej txheem etching
Cov duab hloov pauv yog cov txheej txheem ntawm kev hloov cov kab sib kis kab duab mus rau cov ntawv ci tooj liab, thaum etching tshem tawm cov ntawv xov tooj ntau dhau los ua cov kab sib kis kawg. Ob txheej txheem no ncaj qha txiav txim siab qhov tseeb ntawm kab dav, uas nyob rau hauv lem cuam tshuam rau impedance.
Kev tswj hwm ntawm cov duab hloov pauv: Cov duab hloov pauv feem ntau siv cov txheej txheem photolithography, suav nrog peb kauj ruam ntawm txheej txheej, raug, thiab kev loj hlob. Thaum thov photoresist, nws yog ib qho tsim nyog los xyuas kom meej tias lub thickness ntawm cov photoresist yog uniform kom tsis txhob plam lub npoo ntawm tus qauv tom qab raug vim tsis sib xws photoresist thickness; Thaum raug, nws yog ib qho tsim nyog los tswj qhov raug lub zog thiab raug raug. Lub siab - lub tshuab ua kom pom tseeb yuav tsum tau siv los xyuas kom meej tias qhov sib txawv ntawm cov duab kab dav thiab cov nqi teeb tsa raug tswj nyob rau hauv qhov tsim nyog; Thaum lub sij hawm txoj kev loj hlob, nws yog ib qho tsim nyog los tswj lub sij hawm tsim kho thiab qhov kub thiab txias kom tsis txhob muaj kev loj hlob tsis txaus lossis ntau dhau.
Kev ua kom zoo ntawm cov txheej txheem etching tsis: Cov txheej txheem etching yuav tsum tau teeb tsa cov etching tov concentration, etching kub, thiab etching tus nqi raws li lub thickness ntawm cov ntawv ci tooj liab. Kev nrawm nrawm nrawm tuaj yeem ua rau txo qis hauv kab dav dav, thaum qeeb etching ceev yuav ua rau tsis tiav etching thiab residual tooj liab ntawv nyiaj cuam tshuam impedance. Nyob rau tib lub sijhawm, cov khoom siv tshuaj tsuag etching yuav tsum tau siv los xyuas kom meej tias cov tshuaj etching yog sib npaug ntawm cov ntawv ci tooj liab, tsis txhob etching tsis sib xws thiab kab dav sib txawv hauv qee qhov chaw. Tom qab etching, txoj kab dav qhov tseeb yuav tsum tau kuaj xyuas los ntawm cov khoom siv kho qhov muag, thiab cov khoom uas tshaj qhov sib txawv yuav tsum tau rov ua dua lossis muab pov tseg raws sijhawm.
(3) Tswj kev cuam tshuam ntawm lub ntsej muag npog ntsej muag thiab kho qhov chaw
Txawm hais tias txheej txheej ntawm daim npog ntsej muag (cov roj ntsuab) thiab kev kho deg (xws li kub kub, tin plating) tsis ncaj qha txiav txim siab impedance, kev kho tsis raug tseem yuav cuam tshuam rau impedance stability.
Thickness tswj ntawm lub npog ntsej muag: Lub npog ntsej muag npog npog qhov chaw ntawm cov kab sib kis, thiab nws cov dielectric tsis tu ncua thiab tuab yuav muaj kev cuam tshuam me ntsis ntawm cov impedance ntawm cov kab microstrip (cov kab sawb tsis tshua muaj kev cuam tshuam los ntawm daim npog ntsej muag vim yog qhwv los ntawm dielectric txheej). Yog tias lub thickness ntawm lub npog ntsej muag tsis sib xws, nws yuav ua rau qhov tsis sib xws ntawm qhov chaw nyob ib puag ncig ntawm microstrip kab, yog li ua rau muaj kev hloov pauv hauv zos impedance. Yog li ntawd, thaum lub sij hawm solder daim npog qhov ncauj, nws yog ib qhov tsim nyog los tswj lub txheej thickness, kom lub deviation nyob rau hauv ib tug tsim nyog ntau yam, thiab zam lub solder daim npog qhov ncauj txheej npog qhov tseem ceeb ntawm cov kis kab mob.
Kev sib raug zoo ntawm kev kho deg: Lub hom phiaj ntawm kev kho saum npoo yog los tiv thaiv tooj liab foil oxidation thiab xyuas kom vuam kev ntseeg tau, tab sis lub thickness thiab uniformity ntawm cov txheej txheem kho kuj tuaj yeem cuam tshuam qhov kev tiv thaiv ntawm cov kab sib kis. Yog tias lub thickness ntawm txheej txheej tsis sib npaug, nws yuav ua rau muaj kev hloov pauv hauv qhov chaw tiv thaiv kab mob, yog li cuam tshuam rau impedance. Therefore, it is necessary to control the process parameters of surface treatment to ensure that the thickness deviation of the treatment layer is controlled within a reasonable range, while ensuring consistency through visual inspection and thickness testing.
4, Kev Tshawb Fawb thiab Kev Tshawb Fawb: Xyuas kom muaj kev tswj xyuas qhov tseeb
Kev kuaj pom impedance thiab kev txheeb xyuas yog kab kawg ntawm kev tiv thaiv rau pcb impedance tswj. Los ntawm kev siv cov cuab yeej tshaj lij thiab cov txheej txheem los kuaj xyuas qhov impedance qhov tseem ceeb ntawm cov khoom tiag, peb xyuas kom meej tias lawv ua tau raws li qhov yuav tsum tau ua thiab muab cov ntaub ntawv txhawb nqa rau cov txheej txheem optimization.
(1) Cov cuab yeej nrhiav kom pom impedance thiab txoj hauv kev
Tam sim no, lub ntsiab pcb impedance nrhiav kom tau cov cuab yeej yog impedance tester, thiab cov kev kuaj xyuas feem ntau suav nrog lub sij hawm sau reflectometry (TDR) thiab zaus sau txoj kev.
Lub sij hawm sau reflectometry: TDR xam cov yam ntxwv impedance raws li qhov kev xav ntawm lub plawv dhia ceev ceev xa mus rau cov kab sib kis. Txoj kev no tuaj yeem pom qhov kev hloov pauv ntawm impedance ntawm ntau lub ntsiab lus ntawm cov kab sib kis (xws li qhov chaw thiab qhov loj ntawm impedance hloov), thiab tsim nyog rau kev kuaj xyuas qhov txawv txav hauv cheeb tsam hauv impedance (xws li kab dav sib txawv thiab tsis sib xws dielectric thickness). Thaum lub sij hawm sim, nws yog ib qho tsim nyog los txuas qhov kev sojntsuam mus rau qhov ntsuas cov ntsiab lus ntawm pcb kom ntseeg tau tias muaj kev sib cuag zoo, thiab qhov ntsuas zaus yuav tsum npog qhov kev ua haujlwm siab ntawm - zaus thiab siab - circuits ceev.
Txoj kev sau ntau zaus: Txoj kev sau ntau zaus suav cov yam ntxwv impedance los ntawm kev ntsuas qhov sib txawv ntawm cov kab sib txuas ntawm ntau zaus. Txoj kev no tuaj yeem txheeb xyuas qhov kev hloov pauv ntawm impedance nrog zaus thiab tsim nyog rau kev ntsuas qhov impedance ruaj khov ntawm cov ntawv luam tawm Circuit Board thoob plaws tag nrho cov haujlwm ntau zaus.
(2) Kev txheeb xyuas cov ntaub ntawv tshawb pom thiab kev ua kom zoo
Kev kuaj pom impedance tsis yog qhov kawg, tab sis qhov kev tshawb pom ntawm cov teeb meem hauv cov txheej txheem los ntawm kev txheeb xyuas cov ntaub ntawv, thiab kev ua kom zoo ntawm cov txheej txheem tsis. Piv txwv li, yog tias microstrip kab impedance ntawm ib pawg ntawm cov ntawv luam tawm Circuit Board feem ntau pom tias tsis tshua muaj, nws yuav tsum tau xyuas seb puas muaj teeb meem xws li kab dav dav, me me dhau ntawm dielectric thickness, lossis siab dhau ntawm dielectric qhov tsis tu ncua ntawm cov substrate. Tom qab nrhiav cov hauv paus ntsiab lus ntawm qhov teeb meem, kho cov txheej txheem sib xws. Nyob rau tib lub sijhawm, nws yog ib qho tsim nyog yuav tsum tsim kom muaj cov ntaub ntawv tshawb pom impedance los sau cov ntaub ntawv tshawb pom ntawm txhua pawg ntawm cov ntawv luam tawm hauv Circuit Court, sau cov kev sib raug zoo ntawm cov txheej txheem tsis thiab impedance los ntawm kev txheeb xyuas kev txheeb cais, thiab tsim cov txheej txheem tswj xyuas cov txheej txheem txuas ntxiv txhim kho qhov tseeb ntawm impedance tswj.