Mokhoa oa ho qetela oa ho roala bakeng sa PCB tlhahiso e bile le liphetoho tse kholo lilemong tsa morao tjena. Liphetoho tsena ke litholoana tsa tlhoko ea kamehla ea ho hlola likhaello tsa HASL (Momahano o chesang oa moea) le palo e ntseng e hola ea mekhoa e meng ea HASL.

Ho roala ha ho qetela ho sebelisoa ho sireletsa bokaholimo ba foil ea koporo ea potoloho. Koporo (Cu) ke sebaka se setle sa lisebelisoa tsa ho tjheseletsa, empa e haelloa habonolo; Oxide ea koporo e sitisa metsi ho qhekella. Le ha joale khauta (Au) e se e sebelisetsoa ho koahela koporo, hobane khauta ha e oxidize; Khauta le koporo li tla phatlalatsoa kapele ‘me li kenelle. Koporo efe kapa efe e pepesitsoeng e tla theha oxide ea koporo e sa checheng kapele. Mokhoa o mong ke oa ho sebelisa nickel (Ni) “barrier layer” e thibelang khauta le koporo ho fetisa le ho fana ka sebaka se tšoarellang, se tsamaisang kopano ea karolo.

Litlhoko tsa PCB bakeng sa ho roala nickel e seng motlakase

Ho roala ha nickel e seng motlakase ho lokela ho etsa mesebetsi e ‘maloa:

Bokaholimo ba peeletso ea khauta

Morero oa mantlha oa potoloho ke ho theha khokahano le matla a phahameng a mmele le litšobotsi tse ntle tsa motlakase lipakeng tsa PCB le likarolo. Haeba ho na le oxide leha e le efe kapa tšilafalo holim ‘a PCB, kopanetsoeng ena welded ne a ke ke etsahala le ts’ebetsong kajeno fokolang.

Khauta e beha ka tlholeho holim’a nickel mme ha e oxidize nakong ea polokelo e telele. Leha ho le joalo, khauta ha e lule holim’a nikele e nang le oxidized, ka hona, nickel e tlameha ho lula e hloekile lipakeng tsa bate ea nickel le ho fela ha khauta. Thus, the first requirement of nickel is to remain oxygen-free long enough to allow gold to precipitate. Lisebelisoa li hlahisitse libaka tsa ho sesa tsa lik’hemik’hale ho lumella phosphorus e 6 ~ 10% ka har’a pula ea nikele. Sesebelisoa sena sa phosphorus se apereng nikele e sa sebeliseng motlakase se nkuoa e le tekatekano e hlokolosi ea taolo ea bate, oxide le thepa ea motlakase le ea mmele.

thatafala

Libaka tse se nang motlakase oa nickel tse koahetsoeng li sebelisoa lits’ebetsong tse ngata tse hlokang matla a ‘mele, joalo ka libering tsa phetisetso ea likoloi. Litlhokahalo tsa PCB li thata haholo ho feta tsena bakeng sa lits’ebetso tsena, empa thatafalo e itseng e bohlokoa bakeng sa ho kopanya terata, likhokahano tsa touchpad, likhokelo tsa edge-connetor le ts’ebetso ea ts’ebetso.

Tlamo ea lead e hloka thatafalo ea nickel. Ho lahleheloa ke khohlano ho ka etsahala haeba loto e ka senyeha, e thusang moetapele hore o “qhibilihe” kahare ho substrate. Litšoantšo tsa SEM ha li bontše ho kenella kahare ho nickel / khauta e bataletseng kapa nickel / palladium (Pd) / khauta.

Litšobotsi tsa motlakase

Koporo ke tšepe ea khetho bakeng sa sebopeho sa potoloho hobane ho bonolo ho e etsa. Koporo e tsamaisa motlakase hantle ho feta hoo e batlang e le tšepe e ngoe le e ngoe (tafole ea 1) 1,2. Khauta e boetse e na le motlakase o motle, o etsang hore e be khetho e nepahetseng bakeng sa tšepe e kantle haholo hobane lielektrone li tloaetse ho phalla ka holim’a tsela e tsamaeang hantle (“bokaholimo” ba melemo).

Tafole ea 1. Resistivity ea tšepe ea PCB

Koporo 1.7 (ho kenyeletsoa Ω cm

Gold (including 2.4 Ω cm

Nikele (ho kenyelletsa 7.4 Ω cm

Non-electrolytic nikele barbotage 55 ~ 90 µ ω cm ,.

Leha litšobotsi tsa motlakase tsa lipoleiti tse ngata tsa tlhahiso li sa angoe ke lera la nikele, nikele e ka ama litšobotsi tsa motlakase tsa matšoao a maqhubu a phahameng. Tahlehelo ea lets’oao la microwave PCB e ka feta litlhaloso tsa moqapi. This phenomenon is proportional to the thickness of the nickel – the circuit needs to pass through the nickel to reach the solder spot. Liketsong tse ngata, matšoao a motlakase a ka khutlisoa ho sebopeho sa moralo ka ho hlakisa li-depositi tsa nickel tse ka tlase ho 2.5µm.

Ikopanye le ho hanyetsa

Khokahano ea khokahano e fapane le ho ts’ehetsa hobane sefahleho sa nickel / khauta se lula se sa koaheloa ho pholletsa le bophelo ba sehlahisoa sa ho qetela. Nickel / khauta e tlameha ho lula e khannela batho ba kantle kamora ho pepeseha ha tikoloho nako e telele. Antler’s 1970 book expressed nickel/gold surface contact requirements in quantitative terms. Ho ithutiloe libaka tse fapaneng tsa ts’ebeliso: 3 “65 ° C, mocheso o tloaelehileng o phahameng bakeng sa litsamaiso tsa elektroniki tse sebetsang mocheso oa kamore, joalo ka likhomphutha; 125 ° C, mocheso oo lihokelo tsa bokahohle li tlamehang ho sebetsa, hangata o boletsoeng bakeng sa ts’ebeliso ea sesole; 200 ° C, mocheso oo o ba bohlokoa le ho feta bakeng sa thepa e fofang. ”

Bakeng sa lithemparetjha tse tlase, litšitiso tsa nickel ha li hlokahale. Ha mocheso o eketseha, palo ea nickel e hlokahalang ho thibela phetiso ea nickel / khauta e eketseha (Lethathamo la II).

Tafole ea 2. Khokahano ea nikele / khauta (lihora tse 1000)

Nikele mokoallo lera e khotsofatsang ikopanye le ka 65 ° C ho ikopanya le khotsofatsang ka 125 ° C ho ikopanya le khotsofatsang ka 200 ° 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%

Nikele e sebelisitsoeng thutong ea Antler e ile ea khethoa ka motlakase. Lintlafatso li lebelletsoe ho tsoa ho nickel e sa sebeliseng motlakase, joalo ka ha ho netefalitsoe ke Baudrand 4. Leha ho le joalo, liphetho tsena ke tsa khauta ea 0.5 µm, moo sefofane se atisang ho tetebela 0.2 µm. Sefofane se ka nahanoa hore se lekane bakeng sa likarolo tsa puisano tse sebetsang ho 125 ° C, empa likarolo tse phahameng tsa mocheso li tla hloka liteko tse khethehileng.

“Ha nickel e ntse e tenya, ho tla ba le mokoallo maemong ‘ohle,” ho bolela Antler, “empa linnete tsa tlhahiso ea PCB li khothaletsa baenjiniere ho beha nickel e ngata kamoo ho hlokahalang. Nikele / khauta e bataletseng e se e sebelisoa liselefounong tsa cellular le pager tse sebelisang libaka tsa puisano tse ka amang batho. The specification for this type of element is at least 2 µm nickel.

Sehokedi

Ho qoelisoa ka nono / khauta e sa sebeliseng motlakase ho sebelisoa ha ho etsoa mapolanka a potoloho a nang le selemo se loketseng, o tobetsa, o thellisoa hanyane ka hanyane le likhokelo tse ling tse se nang tšepe.

Lihokelo tsa plug-in li hloka ho tšoarella nako e telele. Maemong ana, ho roala nickel e seng motlakase ho matla ho lekana bakeng sa lits’ebetso tsa PCB, empa ho qoelisoa ka khauta ha ho joalo. Khauta e hloekileng e tšesaane haholo (60 ho isa ho 90 Knoop) e tla itlotsa ho tloha nakong ea likhohlano khafetsa. Ha khauta e tlosoa, nickel e pepesitsoeng e kenella kapele, e leng se etsang hore ho be le keketseho ea ho hanyetsoa ha mabitso.

Ho qoelisoa ka nikele e sa sebeliseng motlakase oa motlakase / ho qoelisoa ka khauta e kanna ea se khetho e ntle ka ho fetesisa bakeng sa lihokelo tsa plug-in tse mamellang ho kenella hangata bophelong bohle ba sehlahisoa. Nickel / palladium / libaka tsa khauta li khothaletsoa bakeng sa likhokelo tse ngata.

Lera la mokoallo

Nikele e sa sebeliseng motlakase e na le tšebetso ea likarolo tse tharo tsa mokoallo poleiting: 1) ho thibela ho hasana ha koporo ho khauta; 2) Ho thibela ho hasana ha khauta ho nickel; 3) Mohloli oa nikele o entsoeng ke metsoako ea Ni3Sn4 intermetallic.

Ho fapana ha koporo ho nickel

Ho fetisoa ha koporo ka nickel ho tla baka ho senyeha ha koporo holima khauta. 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. Ka hona, tlhokahalo ea mocheso oa mokoallo oa mokoallo e ka tlase ho motsotso o le mong ka tlase ho 250 ° C.

Turn le Owen6 ba ithutile ka litlamorao tsa mekhahlelo e fapaneng ea koporo le khauta. Ba fumane hore “… Papiso ea litekanyetso tsa ho kenella ka koporo ho 400 ° C le 550 ° C e bonts’a hore chromium le nikele e hexavalent e nang le phosphorus ea 8-10% ke likarolo tsa mokoallo tse sebetsang ka ho fetisisa tse ithutoang “. (tafole 3).

Tafole ea 3. Ho phunyeletsa ha koporo ka nickel ho ea khauta

Botenya ba nikele 400 ° C lihora tse 24 400 ° C lihora tse 53 550 ° C lihora tse 12

0.25 µm 1 µm 12 µm 18 µm

0.50 µm 1 µm 6 µm 15 µm

1.00 1m 1 8m XNUMX µ M XNUMX µm

2.00 µm E seng phetiso e sa hasaneng e sa hasaneng

According to the Arrhenius equation, diffusion at lower temperatures is exponentially slower. Ho khahlisang ke hore tekong ena, nickel e se nang motlakase e ne e sebetsa hantle makhetlo a 2 ho isa ho a 10 ho feta nickel e khethiloeng ka motlakase. Turn le Owen ba supa hore “… Tšitiso ea (8%) 2µm (80µinch) ea motsoako ona e fokotsa phallo ea koporo ka mokhoa o sa tsotelleng. ”

Ho tsoa tekong ena e feteletseng ea mocheso, botenya ba nickel ea bonyane 2µm ke lintlha tse bolokehileng.

Phapang ea nickel ho khauta

Tlhokahalo ea bobeli ea nickel e sa sebeliseng motlakase ke hore nickel ha e tsamaee ka “lithollo” kapa “masoba a matle” a imetsoeng ka khauta. Haeba nickel e kopana le moea, e tla oxidize. Nickel oxide ha e rekisoe ebile ho thata ho e tlosa ka phallo.

Ho na le lingoloa tse ‘maloa ka nickel le khauta tse sebelisoang e le bajari ba ceramic chip. Lisebelisoa tsena li mamella mocheso o feteletseng oa kopano nako e telele. Teko e tloaelehileng bakeng sa libaka tsena ke 500 ° C metsotso e 15.

Bakeng sa ho lekola bokhoni ba libaka tse bataletseng tse sa sebeliseng motlakase oa motlakase / libaka tse kentsoeng khauta ho thibela nikele oxidation, ho ile ha ithutoa ka bokhabane ba libaka tse nang le mocheso. Different heat/humidity and time conditions were tested. Liphuputso tsena li bonts’itse hore nickel e sirelelitsoe ka ho lekana ke leaching khauta, e lumellang ho khonahala hantle kamora ho tsofala nako e telele.

Ho hasanngoa ha nickel ho khauta e kanna ea ba moeli oa kopano maemong a mang, joalo ka tlamo ea khauta ea thermalsonic. Ketsahalong ena, sefahleho sa nickel / khauta ha se tsoetse pele ho feta bokaholimo ba nickel / palladium / khauta. 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. Phuputso ena e boetse e bonts’itse hore ho ne ho se na phallo ea koporo ka 2.5µm ea nickel / palladium e khethiloeng ke pono ea Auger nakong ea metsotso e 15 ho 500 ° C.

Nickel tin intergeneric komponeng

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).

Tafole ea 4. Bothata ba lisebelisoa tsa PCB ka ho tjheseletsa

Mocheso oa tšepe ° C ho fapana (µinches / SEC.)

Khauta 450 486 117.9 167.5

Koporo 450 525 4.1 7.0

Palladium 450 525 1.4 6.2

Nikele 700 1.7

Ka lits’ebetso tsa nickel / khauta le tin / lead, khauta hang e qhalana ka thini e hlephileng. Solder e theha khokahano e matla ho nickel ea mantlha ka ho theha metsoako ea Ni3Sn4 intermetallic. Enough nickel should be deposited to ensure that the solder will not reach underneath the copper.Litekanyo tsa Bader li bontšitse hore ha ho hlokehe ho feta 0.5µm ea nickel ho boloka mokoallo, leha o feta methating e fetang e tšeletseng ea mocheso. In fact, the maximum intermetallic layer thickness observed is less than 0.5µm(20µinch).

masoba

Nikele / khauta e sa sebeliseng motlakase e sa tsoa fetoha seaparo se tloaelehileng sa ho qetela sa PCB, ka hona lits’ebetso tsa indasteri li kanna tsa se tšoanelehe sebakeng sena. Ts’ebetso ea mouoane oa nitric acid e ea fumaneha bakeng sa ho leka porosity ea nickel / khauta ea elektrolytiki e sebelisoang e le sehokedi sa plug-in (IPC-TM-650 2.3.24.2) 9. Nikele / impregnation e sa sebeliseng motlakase e ke ke ea fetisa tlhahlobo ena. Tekanyetso ea porosity ea Europe e se e ntlafalitsoe ho sebelisoa potassium ferricyanide ho tseba hore na bokaholimo bo bokae ba libaka tse bataletseng, tse fanoang ho latela pores ka millimeter ea sekwere (bugs / mm2). Sebaka se setle se bataletseng se lokela ho ba le masoba a ka tlase ho a 10 ho limilimithara tse sekwere ho holisa 100 x.

bofello

Indasteri ea tlhahiso ea PCB e thahasella ho fokotsa palo ea nickel e kentsoeng ka sekepeng ka mabaka a litšenyehelo, nako ea potoloho le ts’ebetsong ea thepa. Bonyane ba nikele ga tlhaloso e lokela ho thusa ho thibela ho hasana ha koporo holima khauta, ho boloka matla a weld, le ho boloka ho ikopanya le ho hanyetsa ho le tlase. Palo e phahameng ea nickel e lokela ho lumella maemo hore a fetohe ha ho etsoa lipoleiti, kaha ha ho mekhoa e mebe ea ho hloleha e amanang le li-depositi tse teteaneng tsa nickel.

Bakeng sa boholo ba meralo ea kajeno ea boto ea potoloho, seaparo se seng sa motlakase se nang le motlakase sa 2.0µm (80µinches) ke botenya bo tlase ba nickel bo hlokahalang. Ha e le hantle, botenya ba nickel bo tla sebelisoa ho PCB e ngata ea tlhahiso (Setšoantšo sa 2). Phetoho ea botenya ba nickel e tla hlaha ka lebaka la phetoho ea thepa ea lik’hemik’hale tsa ho hlapa le phetoho ea nako ea mochini o phahamisang o iketsang. Ho netefatsa bonyane ba 2.0µm, litlhaloso ho tsoa ho basebelisi ba ho qetela li hloka 3.5µm, bonyane ba 2.0µm, le boholo ba 8.0µm.

Mofuta ona o boletsoeng oa botenya ba nikele o ipakile o loketse tlhahiso ea limilione tsa liboto tsa potoloho. Lebelo le kopana le ho khonahala, bophelo ba sethala le litlhoko tsa ho ikopanya tsa li-elektronike tsa kajeno. Hobane litlhoko tsa kopano li fapane le sehlahisoa se seng ho ea ho se seng, ho koahela bokaholimo ho ka hloka ho ntlafatsoa bakeng sa ts’ebeliso e ngoe le e ngoe.