One article to understand the copper immersion process
Copper deposition is an autocatalytic redox reaction that can be deposited on non-conductive substrates. The role of immersed copper is to realize hole metallization, so that double-sided and multi-layer boards can realize interconnection between layers. Copper immersion is suitable for electroless copper immersion on the metal of printed circuit board holes. It is also suitable for electroless copper immersion on the surface of iron, steel, stainless steel, zinc alloy and copper alloy. It is also suitable for ceramic copper plating, glass copper plating, resin copper plating and plastic copper plating. , diamond copper plating, leaf copper plating, etc.
Copper deposition process equipment: desmear, copper deposition (PTH) and panel power (PP) three-in-one automatic production line.
Safety precautions for the copper immersion process:
1. When adding potions, you must wear rubber gloves that are resistant to strong acids and alkali, gas masks, protective goggles, protective masks, work shoes that are resistant to strong acids and alkali, work aprons and other corresponding safety labor protection supplies.
2. Chemical liquid discharge should be treated accordingly, and what should be recycled and reused should be recycled to make full use of renewable resources and meet national discharge standards.
3. The air of sunken copper drawing contains NO, NO2, HCHO and other irritating and toxic gases. Workshop workers must wear corresponding labor protection supplies, and workshop exhaust should be turned on throughout the day.
4. Always check whether the liquid level of the medicine is normal (in line with the liquid level indication in the tank).
5. Always pay attention to whether the temperature indication on the control panel and the filter circulation pump are normal.
6. Before starting the sinking copper wire each time, the first cylinder should be started by making boards. If the boards are made for a long time, a dummy board dragging cylinder must be made first when production is resumed.
7. The immersed copper cylinder must be inflated frequently, and all liquid medicine cylinders must be kept clean to avoid dust and other contamination.
8. Pay special attention to backlight testing during production, and analyze and adjust immediately if the backlight is found to be abnormal.
9. Frequently check whether the swing, automatic dosing, regeneration device, fire bull, etc. are operating well.
Steps of copper immersion process: including the following steps
1. Treatment before copper sinking;
2. Activation treatment;
3. Chemical copper deposition.
Treatment before copper immersion in the copper immersion process:
1. Deburring: The substrate goes through a drilling process before copper deposition. Although this process is easy to produce burrs, it is the most important hidden danger that causes inferior hole metallization. Deburring process must be used to solve it. Mechanical methods are usually used to ensure that there are no barbs or blockages on the hole edges and inner hole walls.
2. Remove oil stains:
(1) Source of oil contamination: oil contamination caused by hand contact with the drill bit, fingerprints when removing the substrate, and others.
(2) Types of oil pollution: animal and vegetable oils, minerals, etc. The former belongs to saponified oil; the latter belongs to non-saponified oil.
(3) Characteristics of oils and fats: Animal and vegetable oils are saponified oils whose main component is fatty acids, which react with alkali to form fatty acid salts and glycerin that are soluble in water; the chemical structure of mineral oils is mainly paraffin hydrocarbons. A mixture of olefins and naphthenic hydrocarbons and chlorides. It is insoluble in water and does not react with alkali.
(4) The basis for selecting the oil removal treatment method: according to the nature of the oil and the degree of oil contamination.
(5) Method: Use organic solvents and chemical and electrochemical alkaline oil removal.
(6) Function and principle: □Saponizable oils react chemically with alkali to form fatty acid salts and glycerin that are easily soluble in water. The reaction formula is as follows:
(C17H35COO)3NAOH3C17H35COONa+C2H5(OH)2
□Non-saponified oils: mainly rely on surfactants such as OP emulsifier, sodium dodecyl sulfate, sodium silicate, etc. There are two groups in the structure of these substances, one is hydrophobic and the other is hydrophilic. First, the emulsifier is adsorbed on the interface between oil and water, using hydrophobic groups to create an affinity with the oil stains on the surface of the matrix, while the hydrophilic groups point to the oil-removal liquid. Water is a very strong polar molecule, causing oil stains to The gravitational force with the substrate surface is reduced, and through the convection and stirring of the oil removal liquid, the oil stains leave the substrate surface, achieving the ultimate goal of oil removal.
3. Coarse treatment:
(1) The purpose of roughening: mainly to ensure good bonding strength between the metal coating and the substrate.
(2) Principle of roughening: Make micro-concave pits on the surface of the substrate to increase its surface contact area, form a mechanical button combination with the immersed copper layer, and obtain higher bonding strength.
(3) Coarse methods and choices: There are basically the following methods, which mainly play the role of acid etching and strong oxidation.
Ammonium persulfate-sodium persulfate-copper chloride solution hydrogen peroxide/sulfuric acid.
Activation treatment of copper immersion process:
1. The purpose of activation: mainly to form an "initiation center" to make copper deposition uniform.
2. The basic principle of activation: deposit a uniform layer of activation center core particles on the non-metal surface to be plated
3. Activation methods and options:
Step-by-step activation method: It has been proved from production practice that colloidal palladium (one-step activation method) has excellent activation performance, making the obtained deposited layer have good bonding strength and long use time, but the preparation conditions are strict. The activation solution is light brown in color.
A. There are three types of colloidal palladium: acidic colloidal palladium, base palladium, and alkaline colloidal palladium.
B. Preparation of colloidal palladium: Dissolve 1 gram of palladium dichloride in 100 ml of hydrochloric acid and 200 ml of aqueous solution. After all is dissolved, place the beaker in a constant temperature water bath to maintain 30°C ± 1°C and stir under conditions Next, add 2.54 grams of tin dichloride (SnCl2·2H2O) and react for 12 minutes, then mix the two solutions (A, B) (the ingredients of solution B are 75 grams/liter of tin dichloride and 7 grams/liter of sodium silverate NaSnO447H2O , hydrochloric acid 200 ml/L) and continue to incubate for 3 hours (covered) in a constant temperature water bath at 40~50°C. The principle of using this process is that the catalytic performance of palladium particles is related to the aging temperature. It is known from practice that the best conditions are 60℃±5℃. Keeping the temperature for 4-6 hours can not only improve the catalytic activity of palladium particles, but also extend their service life.
C. Activation mechanism: The micelle structure of "colloidal palladium" is an electric double layer, and [Pd0]m is the colloidal core. During activation, Sn2+ is first adsorbed in the pores, and then the divalent tin ions are adsorbed and then C1-1 is adsorbed, forming a [nSn2+·2(n-x)Cl-] adsorption layer and forming a colloidal group. Such micelles are negatively charged and will not agglomerate when collided with aqueous solutions. The 2xCl-1 outside the adsorption layer is a diffusion layer.
D. Maintenance of activation solution: Because the preparation of activation solution is complicated and costly, please pay attention to the following points when using it.
In order to avoid bringing water into the activation solution, treat it with the following solution for 2 to 3 minutes before activation: SnCl2·2H2O40g/L HCl100ml/L. This process is called pre-soaking, and then activation treatment is carried out. The purpose is to filter the water. Dry.
The ingested substrate should contain as little solution as possible and be repeatedly washed in the recovery tank. Use this water to replenish the consumption of the activation solution or to prepare new solutions.
After the activation solution has been used for a period of time, when stratification is found, 10 to 20 grams of stannous chloride per liter can be added according to the actual volume of the activation solution, and the stratification will disappear.
When the temperature is lower than 15°C, the activation effect is poor and heating should be used. A water bath jacket is required for heating.
E. Degumming treatment: Remove excess residual activation solution to prevent it from being brought into the copper sink tank and causing the solution to decompose. NaOH 50 g/L treatment time is 1.5 minutes.
