Conventional plastic the plating copper process: accelerated → → degreasing → rough → colloidal palladium activation electroless copper plating → copper plating. As having a carcinogenic formaldehyde as a reducing agent used in the process of electroless copper plating, a serious threat to the safety of the operator. 1963 DARadovsky invention direct plating, the technology to achieve industrialization in the 1980s, direct the hole metal Chemical plating technology is generally used in the printed circuit board Arts in. In In 1996, Atotech invented Futuron technology, mainly used in ABS alloy material, the process of the process: degreasing → rough → → Futuron activation → copper replacement tin plating copper. Although the technology has its advantages, but there are the inevitable shortcomings, such as easy to drain plating from plated slow, expensive.

MacdermidCo. Phoenix technology was invented in 1991. It is characterized by using sodium hypophosphite as the reductant instead of formaldehyde, occurs first electroless copper plating, so that the plastic surface covering a conductive copper layer, and then directly in the electroless copper plating solution, electroless copper plating. The process is characterized by: (1) using hypophosphite reducing agent instead of formaldehyde; (2) the ground floor, to avoid leakage plated electroless plating; (3) easily electroless plating and electroplating. But the process is only applied to the printed circuit board, as for OPC multilayer circuit board, but not used in ABS plastic and its alloys.

Inferior race hypophosphite reducing agent for electroless copper plating, coating thickness is generally less than 1 μm copper layer deposition reaction can not afford to catalysis. Ni2 + ions in LiJun in the system for re-activating agent to get a certain thickness of the coating, and add 22 ’bipyridine coating performance.

of Phoenix craft on direct plating of ABS plastic, and 22 ’bipyridine additive copper plating. Now most of the domestic factories using the the chemical nickel plated ABS plastic plating as bottom layer, and then electroplating. If the process ( pre-treatment step chemical nickel plating chemical) can be plating and electroplating changed the same plating tank, shortening step, cost savings. The reaction mainly in two steps, the electroless copper plating and copper plating (electroplating solution with the same chemical bath composition), hypophosphite electroless plating process mainly from the reduction. The main contents of this paper hypophosphite copper plating process and different temperatures determine the phosphorus content of the coating.

Experiment

Electroless copper plating solution by the following composition: c (CuSO4) = 004mol / L, and C (sodium hypophosphite) = 028mol / L, and c ( citric acid sodium) = 0051mol / L, and c (boric acid) = 0485mol / L, as well as ρ (22 ’bipyridine) = 5mg / l. Solution with deionized water preparation, the solution was adjusted with NaOH pH = 92 to 96. The electroless copper plating is maintained at a temperature of (70 ± 05) ° C. The same as the composition of the electroless copper plating solution, electroless copper plating solution, the plating temperature of 15 to 70 ° C. In the same plating tank plating, for the control of the temperature, can also be in the plating bath of the same composition at different temperatures of the two bath plating.

ABS plastic: The alkaline degreasing → chromate coarsening → sodium sulfite solution reduction → HCl solution prepreg → colloidal palladium activation → NaOH solution peptize → electroless copper plating. Cyclic voltammetry after electroless copper plating 5min specimen as the working electrode plating solution.

Using atomic force microscopy (referred to as the AFM, the the U.S. Molecular Imaging Company PicoScan / PicoSPM) to observe the surface morphology of the copper plating layer; XRF X-ray fluorescence spectrometer (referred to as Germany Bruker company S4Explorer) to analyze the content of elements in the coating; electrochemical workstation (CHI660, Shanghai Chen Hua Company) to measure the characteristics of the bath cyclic voltammetry (CV). CV measurements using a three-electrode system Pt electrode, calomel electrode as the reference electrode, Pt films, electroless copper plating piece as the working electrode.

II Results and Discussion

1, hypophosphite the 15 ℃ role

15 ℃, hypophosphite not occur in solution electroless plating reaction, electro-reduction reaction does not occur on a copper electrode and a platinum electrode. In order to study the role of sodium hypophosphite experiment without copper ion plating bath. Figure 1, curve 1, Pt as the working electrode, a plating solution (pH = 95) None of Cu2 +, when-850mV

Figure 1, curve 2 and 3 are electroless copper plating film as a working electrode. Curve 3 does not contain the Cu2 + and sodium hypophosphite, when E <-1100mV, Cu cathode Hydrogen Reaction occurs; When E = -270 ~-260mV, there is a small peak, because the solution does not exist in the copper salt and sodium hypophosphite, so that the peak is not reduction peak, but certain ions in the plating solution in the Cu surface adsorption peak. Curve 2 contains sodium hypophosphite and no Cu2 + ions, its cathode Hydrogen Reaction potential value curve 3 due to the presence of sodium hypophosphite, the peak ratio of the hydrogen evolution curve of the curve 2, 3 must be high, and in the -270 also has an adsorption peak in the vicinity of ~-260mV.

From the above analysis, and 15 ° C, sodium hypophosphite in the bath very stable, not chemical plating reaction and electro-reduction reaction on the Pt electrode and the Cu electrode .

2,50 ℃ without copper ion plating solution times hypophosphite role

Seq sodium hypophosphite as the reducing agent of the electroless copper plating reaction once started, at 50 ℃ can still be subjected to chemical plating reaction. Figure 2 is an electroless copper plating film as a working electrode, 50 ° C without copper ion plating solution (pH = 95) the cyclic voltammogram of FIG.

negative sweep when E =-270mV Ads peak adsorption peak, similar to Figure 1. 2 peak (E-Re) E =-580mV at reduction peak, the solution does not contain copper ions, so the reduction peak is not caused by the copper, but sodium hypophosphite on copper electrode electrochemical reduction of peak, the electrode reaction as follows: v

positive scan process, E =-1030mV for the chemical reaction of sodium hypophosphite with the negative sweep process E =-1080mV peak. E =-180mV for the oxidation peak of the Cu-P alloy, the Cu is oxidized to Cu +, Cu + complex (monovalent copper complex, the same below) generated under alkaline conditions, and adsorbed on the surface of the copper electrode. E = 0mV at the oxidation peak of Cu + complex, in the presence of a complexing agent, the reaction of Cu2 + complex (complexes of divalent copper, the same below). Figure 3 is a chemical copper sheet (5min) as a working electrode, and 50 ° C containing copper ions excluding secondary sodium hypophosphite plating solution (pH = 95) the cyclic voltammogram of FIG. Process of negative Esau, E = -400 to-270mV when the peak is similar adsorption peak (ADS), and Figure 1,2. Two peaks at E = -830 ~-780mV at divalent copper complex reduction peak (Re); positive scan two oxidation peaks, one at E = -190 ~~-160mV at oxidation of Cu as Cu + complex, E = 0mV near the oxidation of Cu + complex of the oxidation peak of Cu2 + complex, similar to the results in Figure 2.

3,70 ℃ plating solution

4, the morphology of the coating at different temperatures and its phosphorus content

chemical copper specimens were 5min after plating, at different temperatures obtained. As can be seen, the coating obtained under the low temperature is relatively dense, surface roughness is smaller. As the temperature increases, the roughness of the surface of the coating is increased, the surface of the deposited layer of particles gradually becomes larger.

Conclusion

ABS plastic surface roughening, after the activation treatment, the first in the electroless copper plating solution for electroless plating, and then in the same solution for electroless copper plating method is feasible. 15 ℃, hypophosphite none of them take place in the Pt electrode and the Cu electrode surface electro-reduction and chemical reaction, Pt piece chemical copper XRF test results show that the coating does not contain P element; 50 ° C, sodium hypophosphite electrochemical reduction occurs in the plating bath and disproportionation reduction, containing Cu and P in the coating; 70 ° C, due to the presence of copper ions and sodium hypophosphite solution, and the interactions between them so that all the peaks are offset . After the chemical plating, the electroless copper plating layer can be selected by controlling the temperature of the P element content. The low temperatures plating can be obtained a relatively dense coating.