PCB_MF

6.7 PlatingMost printed circuits, acid pResist Removal :This is exceedingly rapid wosolvents or strong Alkalis 60are used.

plating solutions are used.orth variety of organic0oC – 75oC are effective)













6.8



6.9



UNIPLAT

IT 7TING





7.1 Electroless Copper Platincopper being the conduct it should be protected froimprove the solderability.There are two methods•applying lacquer•non-tarnishing metals coatalloy coating silver, nickel an

ng Processtive material on the PCBom the tarnishing andting like tin. Tin and leadnd gold plating.

PLATING TECHNIQPlating of a metal cana copper by three meta) Immersion Platingb) Electroless Platingc) Electro plating

QUES. be accomplished on thods. They are

7.2 Immersion PIt is the deposition of metsubstrate by chemical replaa salt of the coating metal.The substrate metal reducionic state in the solution.Eg. Tin immersion platingCu + Sn2 = Sn +Cu2 would

Plating : tallic coating on theacement, from a solution of ces the atoms from their take place

7.3 Electroless plaThis mechanism is similarsource of electrons is a chemIn electroplating electronspower source to reduce mestate in electroless plating ndeposition.

ating: r to electroplating but the mical reduction agent. s are obtained from a DCetal ions to the metallic no current is used in the

Mechanism:copper is reduced from itsmeans of chemical reducing The reducing agent reducsolution to metal atoms forThe process produces a cometal coating on a suitableimmersion in an appropriat A chemical reducing agenelectrons from the reaction

s ionic state in solution byg agent ces the metal ions in ther deposition. ontinuous build up of substrate by simplete aqueous solution.nt in the solution suppliesn.

Mn⁺+ne----Mo.the reaction takes place oThe drilled PCB is activatefilm of palladium as a activa

only on a catalytic surface.ed by coating with a thinator

7.4 Activator :Strong acid or strong alkaMixed catalyst solution :Stannous solution dehydraPalladium chloride ---0.25-1Hcl ----- 200-30

alisate --- 50-60gm/ltr1.0gm/ltr00ml/ltr

7.5 Elecroless Bath1. Electroless Bath: CuS042. A chelating or complexin sodium potassium tar tartrate triethanol am3. A reducing agent : For4. Strong alkali – NaOH o5. Stabilizer : potassiumcompounds of either sulphu

h ng agent : Rochelle salt, rtrate or EDTA, othermino and diethyl amino rmaldehyde or KOH cyanide or organic ur or sodium.

Eg: Two mercapto – bonzotAcetic acid.Cupric ions reduces metalli

thizole or benzyl – selenoic cu + acetic acid.

PTH ProcessElectroless copper plating pr1) Alkali cleaning2) Rinse3) Mild Etching4) Rinse5) 10% H2So46) Rinse7) HCL8) Activator9) Rinse10) Post Activator11) Rinse12)Electro less copper platin

rocess steps:ng













7.6 ElectroplatThe process of depositingcoating upon a negatively cthe medium is water in wdissolved as a current sourc

tingg an adherent metalliccharged electrodewhich metal salts have been ce of metallic ions

7.7 Copper platiCopper has excellent elecreadily plated is low cost anresult.Copper is readily activatedbond is obtained between cmetals.

ing:ctrical conductivity, isnd give highly reliabled and hence a good metalcopper and other plated

In PTH plating the thickne25µm, can carry 10A, throuAcid copper plating is wid

ess should not be less thanugh 1mm hole.dely used in PCB’s plating.

Cathode Rod MovemFiltration : Continuousmaintain the quality of p

ments filtration in regard toplating bath.