Study on the influence of acid etching rate

- Sep 15, 2018-

In recent years, with the development of microwave technology, more and more microstrip circuit boards are used in the multi-function light antenna system. The commonly used microstrip circuit boards are generally made of polytetrafluoroethylene copper-clad, and various microwave band lines are carried on one side or both sides. As a result, frequency changes are directly affected.Therefore, in the process of the microstrip circuit board, the control of the dimension accuracy of the microstrip line is strict, which raises new problems for the process. 

1 the introduction

In recent years, with the development of microwave technology, more and more microstrip circuit boards are used in the multi-function light antenna system. The commonly used microstrip circuit boards are generally made of polytetrafluoroethylene copper-clad, and various microwave band lines are carried on one side or both sides. As a result, frequency changes are directly affected.Therefore, in the process of the microstrip circuit board, the control of the dimension accuracy of the microstrip line is strict, which raises new problems for the process. 

Etching is the process of stripping the copper off the developing area of the circuit board to form the required circuit diagram.Acid CuCl2 etching solution is a common etching solution used for anti-etching dry film, anti-etching printing materials, liquid photosensitive printing materials, gold coating. 

Experiment 2

2.1 experimental materials

Single copper-clad, shenzhen dejing yuyang electronics co., LTD.Hydrochloric acid, pure analysis, shenzhen dingqing chemical co. LTD.Anhydrous cupric chloride, pure analysis, Shanghai sinopharm group;Sodium chlorate, analytical purity, Shanghai Abby chemical reagent co. LTD.Benzotriazole, analytically pure, Shanghai Abby chemical reagent co., LTD.Sulfamic acid, analytical purity, Shanghai eipi chemical reagent co., LTD.Ammonium chloride, pure analysis, Qingdao yak chemical reagent sales co. LTD. 

2.2 experimental instrument

TE214S electronic balance, saibole (Shanghai) instrument co., LTD.Dhg-9025a thermostatic drying oven, Shanghai hecheng instrument manufacturing co. LTD. 

2.3 experimental methods

2.3.1 acid etching process method

Single coated copper sheet - cleaning - inspection - acid etching - washing - pickling - washing - drying - weighing

2.3.2 preparation of additives

According to get 0.1 g of benzene and three azole nitrogen, amino sulfonic acid, 1.0 g 10. GNH4Cl, add 100 ml beaker, with the capacity to 100 ml, the deionized water under 25 ℃, stir well. 

2.4 appearance inspection and analysis

The appearance of the etching sample was examined to observe the evenness of the etching surface, the existence of edge and the completeness of etching. 

3 results and discussion

3.1 influence of process parameters on etching rate

3.1.1 influence of copper chloride concentration on etching rate

Selection of hydrochloric acid concentration 2.0 mol/L, potassium chloride concentration of 14 g/L, sodium chlorate 20 g/L, additive concentration in 14 g/L, operating temperature is 50 ℃, change the copper chloride concentration.The effects of different copper chloride concentrations on the etching rate were investigated, and the results were shown in FIG. 1. 

Figure 1 influence of copper chloride concentration on etching rate

Figure 1 influence of copper chloride concentration on etching rate

It can be seen from figure 1 that when the mass concentration of copper chloride is less than 200g/L, the etching rate increases sharply with the increase of concentration.When the mass concentration of copper chloride is 200g/L, the maximum etching rate is 14.42With the further increase of the mass concentration of copper chloride, etching rate was first reduced.Therefore, the optimal copper chloride mass concentration is about 200g/L. 

3.1.2 influence of Cu+ concentration on etching rate

Selection of copper chloride concentration of 200 g/L, 2.0 mol/L hydrochloric acid concentration, concentration of potassium chloride 14 g/L, sodium chlorate 20 g/L, additive concentration in 14 g/L, operating temperature 50 ℃.The effect of different Cu+ concentrations on the etching rate was investigated, and the results were shown in FIG. 2. 

Figure 2 influence of Cu+ concentration on etching rate

Figure 2 influence of Cu+ concentration on etching rate

Depending on the etching reaction, the copper etching will form a univalent copper ion, which will significantly reduce the etching rate.Therefore, it is necessary to keep the content of Cu+ in a low range during the etching operation and re-oxidize it to Cu2+ as soon as possible. 

3.1.3 influence of HCl concentration on etching rate

Selection of copper chloride concentration of 200 g/L, potassium chloride concentration of 14 g/L, sodium chlorate 20 g/L, additive concentration in 14 g/L, operating temperature is 50 ℃, change the concentration of hydrochloric acid.The effect of different HCl concentrations on the etching rate was investigated, and the results were shown in FIG. 3. 

Figure 3 influence of HCl concentration on etching rate

Figure 3 influence of HCl concentration on etching rate

Both Cu2+ and Cu+ are actually complex ions in the copper chloride etching solution.The copper ion is a good complex formation because it has an incomplete d orbital electron shell.In general, four coordination bonds can be formed.When the solution contains more Cl-, Cu2+ exists as [CuCl4]2- complex ions and Cu+ exists as [CuCl3]2- complex ions.When the concentration of hydrochloric acid increases, the etching time decreases and the amount of copper dissolved can be increased.However, the concentration of hydrochloric acid should not be too high, otherwise, the increased acid fog will not only affect the environment but also increase the corrosion damage to equipment, and the solubility of copper chloride decreases rapidly with the increase of acid concentration. 

3.1.4 effect of additive concentration on etching rate

Selection of copper chloride concentration of 200 g/L, 2.0 mol/L hydrochloric acid concentration, concentration of potassium chloride 14 g/L, sodium chlorate, 20 g/L operation temperature is 50 ℃, change the concentration of additive.The effects of different additive concentrations on the etching rate were investigated, and the results were shown in FIG. 4. 

Figure 4 influence of additive concentration on etching rate

Figure 4 influence of additive concentration on etching rate

It can be seen from figure 4 that with the increase of additive concentration, there is a linear relationship between etching rate and additive concentration.When the additive concentration is 10g/L, the etching rate is about 13.75 displacement m/min. When the additive concentration is 14g/L, the etching rate is 14.41 displacement m/min.However, the additive concentration was too high. On the one hand, the additive crystallized on the surface of the sample and residues increased, which affected the appearance of the sample.On the other hand, the cost of etching solution will go up.Therefore, the concentration of additives cannot be increased blindly.Under comprehensive consideration, the additive concentration can be controlled at 10-18g/L. 

3.1.5 influence of temperature on etching rate

The copper chloride concentration was 200g/L, the hydrochloric acid concentration was 2.0mol/L, the potassium chloride concentration was 14g/L, the sodium chlorate was 20g/L, the additive concentration was 14g/L, and the temperature was changed.The effects of different temperatures on the etching rate were investigated, and the results were shown in FIG. 5. 

FIG. 5 influence of temperature on etching rate

FIG. 5 influence of temperature on etching rate

With the increase of temperature, etching rate faster, but the temperature is unfavorable and exorbitant, general control around 50 ℃.Too high temperature will lead to too much HCl volatilization, resulting in the imbalance of the proportion of solution components.In addition, if the etching solution temperature is too high, the corrosion resistant layer is easy to damage. 

3.2 appearance inspection analysis

Through the appearance inspection of the etching sample, the test results show that the etching surface is uniform, there is no edge and the etching is complete. 

4 conclusion

(1) the best formula of acidic etching solution is: 200g/L of copper chloride mass concentration, 1.5-2.5 mol/L of hydrochloric acid concentration, 20g/L of sodium chlorate, 10-18g/L of potassium chloride concentration, and 14g/L of additive concentration. 

(2) the operating temperature 50 ℃ or so.