After an "image transfert and development" step, now you will have to:

-Create a copper layer on the developped areas  of the dry film, to create tracks of the outerlayer of PCB.

-Thereafter create a selective tinning on tracks to protect Copper from the aggressiveness of etching.

• Copper plating

This operation is devided into 3 steps:

*Surface preparation: degreasing (ELECTROPOSIT PC CLEANER) and micro-etching to increase the surafce roughness and improve adhesion.

*Activation: is done in the solvent of the copper plating bath (sulfuric acid).

*Electrolytic Copper:

To perform this plating, two kind of current are possible:

Pulse current (PPR) or Direct Current (DC).

Pulse current can be used in horizontal (COPPER GLEAM PPR-H) or in vertical mode (CuPulse). However, it is less used and requires insoluble anodes.

Direct current is more usual on French PCB manufacturing lines. CTS proposes:

-COPPER GLEAM PC

-COPPER GLEAM 125

-COPPER GLEAM CLX

-COPPER GLEAM HT 55

Via filling process allows to Copper plate small size holes and blind holes, but requires as well insoluble anodes and the use of copper oxide.

N.B.: The additive promotes high current densities. the higher the current density, the higher the additive consumption.

Approximately one hour is necessary to plate 30 µm.

• Selective tinning

Selective tinning can be realised with tin (Sn) or with an alloy of tin and Lead (Sn/Pb).

Tin:

A thin layer (4-6µm) of Tin is filed because it will be stripped afterward.

-in MSA (MetaneSulfonic Acid) middle: SOLDERON PCT

-in sulfuric middle: RONASTAN EC

-in sulfuric acid middle - Bright Tin: TIN GLEAM CD

Tin / Lead (60/40):

A layer of about 10µm of this aloy is filed.

-IN MSA middle: SOLDERON PC

Close from the eutectic point of the Tin / Lead alloy.