Lead-free tin green printed circuit board process example

SL-2 Multi-Copper Surface Anti-Oxidation and Anti-Corrosion Agent

SL-2 multifunctional copper surface oxidation and corrosion inhibitor is a new high-tech environmental protection product. It can form a dense organic film on the surface of metallic copper when it is in contact with it. As a result, it plays an anti-oxidation and anti-corrosion effect on the surface of metallic copper.

The product can be widely used in the whole process of printed circuit board production. For example, during the process of oxidation prevention, the tin-lead-dissolved tin mixed with nitric acid can achieve the best protection for metallic copper while dissolving the lead-tin coating, and can also be used as the antioxidant layer of the final product instead of through the hot air leveling treatment. Solder oxide layer.

Another very important application of this product is to replace the current use of lead-platinum plating process to achieve circuit board production without lead, tin waste discharge.

application:

*Instead of lead-platinum plating Processes for use are: ... electroplating copper - washing - dipping SL-2 (greater than 2 minutes) - hot water - drying - faded film - alkaline etching...
* End product anti-oxidation treatment (instead of hot air leveling)
The use process is: ... Washing - dipping SL-2 (10 seconds) - hot water - drying ...

* Copper surface anti-oxidation and anti-corrosion additives

According to the specific use conditions, it can be added to acidic copper plating solution, acid-plated lead-tin solution, and acidic cleaning solution, which can effectively relieve the oxidation and corrosion caused by acidic liquids on copper. After the treated copper surface is washed with water, it can keep the copper surface from being oxidized for a long time (it is recommended to add 10%, the user can adjust according to the use conditions).

Product technical indicators:

Appearance: Blue-green transparent or translucent liquid Specific gravity: 1.00
PH value: 4.45-4.50

Mechanism Introduction:

SL-2 Multi-Copper Anti-oxidant Anti-corrosion agent contains an organic compound. The compound has 1 active group. This group can form a covalent bond with copper. As a result, the molecules are tightly linked to copper and do not bond to other organic materials or lead-tin metals. In this way, when the SL-2 multifunctional copper surface oxidation and corrosion inhibitor is in contact with copper, it will only form a dense organic film on the copper surface. This compound has solubility in acidic aqueous solutions, is insoluble in neutral and alkaline aqueous solutions, and assumes a molten state when the ambient temperature exceeds 100°C. The SL-2 multifunctional copper surface oxidation and corrosion resisting agent utilizes these chemical properties to achieve effective protection of copper under alkaline conditions, faded organic films, and etching; copper surface protection in the air Oxidation; In high temperature soldering, the solder can penetrate the anti-oxidation film; Under acidic conditions, the anti-oxidation anti-corrosion film is removed.

Use examples:

Instead of electroplating lead-tin process

After electroplating of copper on the circuit, the plate was immersed in a pre-impregnated solution (the pre-infusion was 5% SL-2 in a 5% aqueous solution of hydrochloric acid; the operating conditions were: room temperature, time to ensure that the surface of the plate and the pore walls were fully wetted If the surface oxidation is serious, the infiltration time can be properly extended; flush the surface with clean water to ensure that the liquid attached to the surface is not acidic; immerse the plate in the oxidation- and anti-corrosion agent on the surface of the SL-2 multi-functional copper, in 20 -2°C infiltration time at -25°C (When the solution temperature is low, the infiltration time can be properly extended. The maximum soaking temperature should not exceed 40°C); Soak the plate in hot water at 70-80°C, soaking time In order to ensure that the surface of the board and the wall of the hole are in full contact with the hot water, it is usually 10-20 seconds; the board is fixed on the rack and placed in an oven (the oven must be in a ventilated state), 140°C, 10 minutes. When the panel temperature is close to room temperature, the developing film is faded out in a 5% aqueous alkali solution, and you can clearly see that the copper surface of the positive image part is significantly different from the copper of other parts; Etching in an alkaline copper chloride etching solution etches copper in the negative pattern portion. This step is to ensure that there are no solid particles in the etchant, and the transfer wheel of the etching machine is preferably round. If soaked swing etching is used, the effect is best; after etching, the plate can be rinsed with clean water to perform subsequent processes.

Example one, anti-oxidation treatment between processes

After the copper is electroplated in the holes, the plate is placed into the prepreg described in Example I. The operating conditions are: room temperature, time to ensure that the surface of the plate and the walls of the holes are fully wetted (usually 10 seconds); flush the plate with water Face to ensure that the liquid attached to the board is not acidic; placing the board on a rack naturally air dry (or other drying method), can guarantee the brightening of the copper surface for several days as early as possible; after dilute pickling and washing, subsequent steps can be carried out Process.

Example II Anti-oxidation treatment of the final product

After printing (coating) of solder resist and printed characters, the board is degreased, and then the board is placed in the pre-preg liquid described in Example 1, operating conditions: room temperature, time to ensure that the board surface and hole wall can be fully Infiltration, removal of the oxide layer time; flush the surface with water to ensure that the liquid attached to the board is not acidic; and then washed with pure water again, the board immersed in the SL-2 multi-purpose copper surface anti-oxidation anti-corrosion agent, Soaking time at room temperature is 10 seconds; the plate is soaked in hot water at 70-80°C, soaking time to ensure that the surface of the plate and the hole wall are in full contact with the hot water, usually 10-20 seconds; After rinsing with clean water, the plates are dried, and the drying conditions are: 120° C., 10 minutes; afterwards, the products are finished through the shape and inspection of the cut-milling.

Example 3: Corrosion Inhibitors as Fade-Lead Tin Solution

Adding the SL-2 multi-functional copper surface antioxidant to the nitric acid aqueous solution can effectively protect the copper during the process of removing the lead-tin coating. It is recommended to add 10%, users can adjust within the range of 1-20% according to the actual situation. If lead and tin fade slowly, you can reduce it.

Example four, instead of electroplating lead-tin process

After electroplating of copper on the circuit, the plate was immersed in a pre-impregnated solution (the pre-infusion was 5% SL-2 in a 5% aqueous solution of hydrochloric acid; the operating conditions were: room temperature, time to ensure that the surface of the plate and the pore walls were fully wetted If the surface oxidation is serious, the infiltration time can be properly extended; flush the surface with clean water to ensure that the liquid attached to the surface is not acidic; immerse the plate in the oxidation- and anti-corrosion agent on the surface of the SL-2 multi-functional copper, in 20 -2°C infiltration time at -25°C (When the solution temperature is low, the infiltration time can be properly extended. The maximum soaking temperature should not exceed 40°C); Soak the plate in hot water at 70-80°C, soaking time In order to ensure that the surface of the board and the wall of the hole are in full contact with the hot water, it is usually 10-20 seconds; the board is fixed on the rack and placed in an oven (the oven must be in a ventilated state), 140°C, 10 minutes. When the panel temperature is close to room temperature, the developing film is faded out in a 5% aqueous alkali solution, and you can clearly see that the copper surface of the positive image part is significantly different from the copper of other parts; Etching in an alkaline copper chloride etching solution etches copper in the negative pattern portion. This step is to ensure that there are no solid particles in the etchant, and the transfer wheel of the etching machine is preferably round. If soaked swing etching is used, the effect is best; after etching, the plate can be rinsed with clean water to perform subsequent processes.