Ny fizotra farany amin’ny PCB ny fanamboarana dia niova fiovana lehibe tato anatin’ny taona vitsivitsy. These changes are the result of the constant need to overcome the limitations of HASL(Hot air cohesion) and the growing number of HASL alternatives.

Ny paty farany dia ampiasaina hiarovana ny velaran’ny varahina varahina. Copper (Cu) dia faritra tsara ho an’ny singa welding, fa mora entina amin’ny oxygène; Ny oksidana varahina dia manakana ny mandon’ny solder. Na dia ny volamena (Au) aza izao no ampiasaina hanaronana varahina, satria ny volamena tsy manala oksidra; Ny volamena sy ny varahina dia hiparitaka haingana ary hiparitaka. Izay varahina miharihary dia hamorona oksida varahina tsy azo alaina haingana. Ny fomba fiasa iray dia ny fampiasana “layer” sakana “nickel (Ni) izay manakana ny volamena sy ny varahina tsy hamindra ary manome faritra maharitra sy mitondra ho an’ny fivondronan’ny singa.

Fepetra takiana PCB amin’ny fonosana nikela tsy electrolytic

Ny fonosana nikela tsy electrolytic dia tokony hanao asa maro:

Ny ambonin’ny tahiry volamena

Ny tanjona faratampon’ny boriborintany dia ny mamorona fifandraisana misy tanjaka ara-batana avo sy toetra mampiavaka ny herinaratra tsara eo amin’ny PCB sy ny singa. Raha misy oksida na fandotoana eo amin’ny PCB, dia tsy hitranga io fiombonam-bary io amin’ny fivalanana malemy ankehitriny.

Ny fametrahana volamena dia voajanahary eo ambonin’ny nikela ary tsy mihodina mandritra ny fitehirizana maharitra. Na izany aza, ny volamena dia tsy mijanona amin’ny nikela voahosotra, noho izany ny nikela dia tsy maintsy mijanona ho madio eo anelanelan’ny fandroana nikela sy ny fandravana ny volamena. Thus, the first requirement of nickel is to remain oxygen-free long enough to allow gold to precipitate. Components developed chemical leaching baths to allow 6~10% phosphorus content in nickel precipitation. Ity atiny fosforôla ity ao anaty fonosana nikela tsy electrolytic dia raisina ho fandanjalanjana mitandrina ny fifehezana fandroana, oksida ary toetra ara-batana sy ara-batana.

hamafin’ny

Ny elanelana vita amin’ny nickel tsy electrolytic dia ampiasaina amin’ny fampiharana maro izay mitaky tanjaka ara-batana, toy ny fitaterana fiara fitaterana fiara. Ny fepetra PCB dia ambany kokoa noho ireo ho an’ireo rindranasa ireo, saingy ny hamafin’ny sasany dia zava-dehibe amin’ny fifamatorana tariby, ny fifandraisana amin’ny touchpad, ny mpampitohy an-tsisitra, ary ny fikirakirana maharitra.

Ny famatarana firaka dia mitaky hamafin’ny nikela. Ny fihoaran’ny fikorontanana dia mety hitranga raha manimba ny fipoahana ny firaka, izay manampy ny firaka “hitsonika” ao anaty vongan-tany. Ny sary SEM dia tsy mampiseho fidirana an-tampon’ny nikela fisaka / volamena na nikela / palladium (Pd) / volamena.

Toetra mampiavaka ny herinaratra

Ny varahina no metaly voafidy amin’ny fananganana faritra satria mora ny manamboatra azy. Ny varahina dia mitarika herinaratra tsara kokoa noho ny ankamaroan’ny vy (latabatra 1) 1,2. Gold also has good electrical conductivity, making it a perfect choice for the outermost metal because electrons tend to flow on the surface of a conductive route (the “surface” benefit).

Table 1. Resistivity of PCB metal

1.7 varahina (anisany Ω cm

Gold (including 2.4 Ω cm

Nickel (including 7.4 Ω cm

Famonoana nikela tsy electrolytic 55 ~ 90 µ ω cm

Although the electrical characteristics of most production plates are not affected by the nickel layer, nickel can affect the electrical characteristics of high frequency signals. Ny fiparitahan’ny mari-pamantarana mikraoba PCB dia mety mihoatra ny famaritan’ny mpamorona. This phenomenon is proportional to the thickness of the nickel – the circuit needs to pass through the nickel to reach the solder spot. Amin’ny fampiharana maro, ny signal elektrika dia azo averina amin’ny famaritana endrika amin’ny alàlan’ny famaritana ny fametrahana nikela latsaky ny 2.5µm.

Fifandraisana fanoherana

Ny fanoherana amin’ny fifandraisana dia tsy mitovy amin’ny azo antoka satria ny nikela / volamena dia mijanona tsy voafehy mandritra ny androm-piainan’ny vokatra farany. Ny nikela / volamena dia tsy maintsy mijanona ho mifandray amin’ny fifandraisana ivelany aorian’ny fipoahan’ny tontolo iainana maharitra. Antler’s 1970 book expressed nickel/gold surface contact requirements in quantitative terms. Various end-use environments have been studied: 3 “65°C, a normal maximum temperature for electronic systems operating at room temperature, such as computers; 125 ° C, ny mari-pana tsy maintsy iasan’ny mpampitohy manerantany, izay voatondro matetika amin’ny fampiharana miaramila; 200 ° C, io mari-pana io dia lasa manandanja kokoa amin’ny fitaovana manidina. “

Ho an’ny mari-pana ambany dia tsy ilaina ny sakana nikela. Rehefa mitombo ny mari-pana, ny habetsaky ny nikela ilaina hisorohana ny fitomboan’ny famindrana nikela / volamena (Tabilao II).

Tabilao 2. Fifandraisana fanoherana ny nikela / volamena (1000 ora)

Ny fifandraisana amin’ny sisin’ny nikela dia fifandraisana mahaliana amin’ny 65 ° C, fifandraisana mahafapo amin’ny 125 ° C

0.0 µm 100% 40% 0%

0.5 µm 100% 90% 5%

2.0 µm 100% 100% 10%

4.0 µm 100% 100% 60%

Ny nikela nampiasaina tamin’ny fianaran’i Antler dia notifirina herinaratra. Ny fanatsarana dia andrasana amin’ny nikela tsy electrolytic, araka ny fanamafisan’i Baudrand 4. Na izany aza, ireo vokatra ireo dia ho an’ny volamena 0.5 µm, izay matetika mipoitra 0.2 µm ny fiaramanidina. Ny fiaramanidina dia azo heverina ho ampy ho an’ny singa mifandraika miasa amin’ny 125 ° C, fa ny singa maripana ambony kokoa dia mitaky fanandramana manokana.

“Ny nikela matevina, ny tsara kokoa ny sakana, amin’ny tranga rehetra,” hoy i Antler, “fa ny zava-misy amin’ny famokarana PCB dia mandrisika ny injeniera hametraka nikela betsaka araka izay ilaina. Ny nikela / volamena fisaka izao dia ampiasaina amin’ny telefaona finday sy pager izay mampiasa teboka fifandraisan’ny touch-pad. The specification for this type of element is at least 2 µm nickel.

Ilay mpampitohy

Ny fanitrihana nickel / volamena tsy misy electrolytic dia ampiasaina amin’ny fanamboarana tabilao misy lohataona, press-fit, sliding press-low ary ireo mpampifandray hafa tsy lasoka.

Ny mpampifandray plug-in dia mila maharitra maharitra ara-batana. Amin’ireto tranga ireto, ny palitao nikela tsy electrolytic dia matanjaka tsara amin’ny fampiharana PCB, fa ny fitrohana volamena kosa tsy. Very thin pure gold (60 to 90 Knoop) will rub away from the nickel during repeated friction. Rehefa esorina ny volamena, dia manala oksizenina haingana ny nikela voarindra, ary miteraka fiakaran’ny fanoherana ny fifandraisana.

Ny fandrakofana nickel tsy electrolytic / fanitrihana volamena dia mety tsy ny safidy tsara indrindra ho an’ny mpampifandray plug-in izay mahazaka fampidirana maro mandritra ny androm-piainan’ny vokatra. Ny velaran-tany nikela / padiumadium / volamena dia atolotra ho an’ireo mpampifandray marobe.

The barrier layer

Ny nikela tsy electrolytic dia manana asan’ny sosona sakana telo eo amin’ny lovia: 1) hisorohana ny fanaparitahana varahina amin’ny volamena; 2) To prevent the diffusion of gold to nickel; 3) Loharanon’ny nikela noforonin’ny Ni3Sn4 intermetallic compound.

Fanaparitahana varahina amin’ny nikela

Ny famindrana varahina amin’ny alàlan’ny nikela dia hamoahana ny varahina amin’ny volamena ambonin’ny tany. The copper will oxidize quickly, resulting in poor weldability during assembly, which occurs in the case of nickel leakage. Nickel is needed to prevent migration and diffusion of empty plates during storage and during assembly when other areas of the plate have been welded. Noho izany, ny takiana amin’ny mari-pana amin’ny sosona sakana dia latsaky ny iray minitra ambanin’ny 250 ° C.

Turn sy Owen6 dia nandinika ny vokatry ny sakana samihafa amin’ny varahina sy volamena. Hitan’izy ireo fa “… Ny fampitahana ny sanda permeabilité varahina amin’ny 400 ° C sy 550 ° C dia mampiseho fa ny chromium hexavalent sy ny nikela miaraka amin’ny atiny fosforôly 8-10% no sosona sakana mahomby indrindra nianarana “. (latabatra 3).

Tabilao 3. Fidirana varahina amin’ny alàlan’ny nickel to gold

Nickel thickness 400°C 24 hours 400°C 53 hours 550°C 12 hours

0.25 µm 1 µm 12 µm 18 µm

0.50 µm 1 µm 6 µm 15 µm

1.00 µm 1 µm 1 µ M 8 µm

2.00 µm Non-diffusion non-diffusion tsy fanaparitahana

According to the Arrhenius equation, diffusion at lower temperatures is exponentially slower. Mahaliana fa amin’ity andrana ity, ny nikela tsy mandeha amin’ny alàlan’ny electrolytic dia 2 hatramin’ny 10 heny mahomby kokoa noho ny nikela elektroplated. Navoitran’i Owen ary nomarihin’i Owen fa “… A (8%) 2µm(80µinch) barrier of this alloy reduces copper diffusion to a negligible level.”

Avy amin’ity fitsapana hafanana tafahoatra ity, ny hatevin’ny nikela 2µm farafahakeliny dia famaritana azo antoka.

Fanaparitahana nikela amin’ny volamena

Ny fepetra takiana faharoa amin’ny nikela tsy electrolytic dia ny nikela tsy hifindra monina amin’ny “grains” na “lavaka tsara” nofenoina volamena. If nickel comes into contact with air, it will oxidize. Nickel oxide is not soldable and difficult to remove with flux.

Misy lahatsoratra maromaro momba ny nikela sy ny volamena ampiasaina ho mpitatitra kozatra seramika. These materials withstand the extreme temperatures of assembly for a long time. Fitsapana mahazatra an’ireo sehatra ireo dia 500 ° C mandritra ny 15 minitra.

Mba hahafahana manombatombana ny fahaizan’ny fisaka nikela tsy misy electrolytic / volamena-impregnated fisorohana mba hisorohana ny okidratika nikela, dia nodinihina ny fahaizan’ny fipetrahan’ny mari-pana. Different heat/humidity and time conditions were tested. Ireo fandinihana ireo dia naneho fa ny nikela dia voaaro amin’ny alàlan’ny fametahana volamena, mamela ny faharetana tsara aorian’ny fahanterana lava.

Ny fanaparitahana nikela amin’ny volamena dia mety ho antony voafetra ho an’ny fivoriana amin’ny tranga sasany, toy ny fatorana tariby thermalsonic volamena. Amin’ity rindranasa ity dia tsy dia mandroso noho ny velaran-tany nikela / palladium / volamena ny velarana nikela / volamena. Iacovangelo investigated the diffusion properties of palladium as a barrier layer between nickel and gold and found that 0.5µm palladium prevents migration even at extreme temperatures. This study also demonstrated that there was no diffusion of copper through 2.5µm of nickel/palladium determined by Auger spectroscopy during 15 minutes at 500°C.

Vondron-kambana mitambatra nickel

During surface mount or wave soldering operation, atoms from the PCB surface will be mixed with solder atoms, depending on the diffusion properties of the metal and the ability to form “intermetallic compounds” (Table 4).

Tabilao 4. Fahasamihafana amin’ny fitaovana PCB amin’ny welding

Ny mari-pana metaly ° C diffusivity (µinches / SEC.)

Volamena 450 486 117.9 167.5

Copper 450 525 4.1 7.0

Palladium 450 525 1.4 6.2

Nickel 700 1.7

Amin’ny rafitra nikela / volamena sy tin / firaka, ny volamena avy hatrany dia levona ao anaty vifotsy malalaka. The solder forms a strong attachment to the underlying nickel by forming Ni3Sn4 intermetallic compounds. Enough nickel should be deposited to ensure that the solder will not reach underneath the copper.Ny fandrefesana an’i Bader dia nampiseho fa tsy mihoatra ny 0.5µm ny nikela ilaina amin’ny fitazonana ny sakana, na dia amina tsingerin’ny hafanana mihoatra ny enina aza. In fact, the maximum intermetallic layer thickness observed is less than 0.5µm(20µinch).

porous

Ny nikela / volamena tsy electrolytic dia vao tsy ela izay nanjary firakotra farany ambony PCB farany ambony, ka mety tsy mety amin’io fomba io ny fomba indostrialy. Misy dingan’ny etona asidra azôty hizaha toetra ny poriazika amin’ny alàlan’ny nikela / volamena electrolytic ampiasaina ho mpampifandray plug-in (IPC-TM-650 2.3.24.2) 9. Ny nickel / impregnation tsy electrolytic dia tsy handalo ity fitsapana ity. Ny fenitra porosity eropeana dia novolavolaina tamin’ny fampiasana potasioma ferricyanide hamaritana ny poria azo itoviana amin’ny fisaka, izay omena amin’ny lafiny pore isaky ny milimetatra toradroa (bug / mm2). Ny velarana fisaka tsara dia tokony hanana lavaka latsaky ny 10 isaky ny milimetatra toradroa amin’ny fanamafisana 100 x.

famaranana

Ny indostrian’ny famokarana PCB dia liana amin’ny fampihenana ny habetsaky ny nikela apetraka eo amin’ny solaitrabe noho ny antony vidiny, ny vanim-potoanan’ny tsingerina ary ny fifanarahan’ny fitaovana. Ny famaritana nikela farafahakeliny dia tokony hanampy amin’ny fisorohana ny fanaparitahana varahina amin’ny tampon’ny volamena, mitazona ny tanjaky ny vy tsara, ary mitazona ny fanoherana ambany ho ambany. Ny famaritana nickel farany ambony dia tokony hamela ny fahafaha-manao amin’ny famokarana takelaka, satria tsy misy fomba tsy fahombiazana lehibe mifandraika amin’ny fametrahana nikela matevina.

Ho an’ny ankamaroan’ny endriny ankehitriny, ny fonosana nikela tsy electrolytic 2.0µm (80µinches) no hatevin’ny nikela farany ambany takiana. Amin’ny fampiharana, karazana hatevin’ny nikela no ampiasaina amin’ny famokarana betsaka ny PCB (sary 2). Ny fiovana amin’ny hatevin’ny nikela dia vokatry ny fiovan’ny toetran’ny akora simika fandroana sy ny fiovan’ny fotoanan’ny milina fananganana mandeha ho azy. Mba hahazoana antoka farafahakeliny 2.0µm, ny famaritana avy amin’ny mpampiasa farany dia mila 3.5µm, farafahakeliny 2.0µm, ary 8.0µm farafaharatsiny.

Ity karazana hatevin’ny nikela voafaritra ity dia voaporofo fa mety amin’ny famokarana tabilao an-tapitrisany. Ny elanelam-potoana dia mahafeno ny faharetana, ny fiainana talantalana ary ny fepetra takiana amin’ny elektronika ankehitriny. Satria ny fepetra takiana amin’ny fivoriambe dia tsy mitovy amin’ny vokatra iray mankany amin’ny iray hafa, ny fonosana ambonin’ny dia mety mila havaozina ho an’ny fampiharana manokana.