Alkaline cupric chloride etchant for printed circuit board

Abstract

An alkaline cupric chloride etchant for a printed circuit board, comprising copper chloride and a sub-etchant. The sub-etchant comprises the following in percentage by weight: 10 to 30 percent of ammonium chloride, 0.0002 to 25 percent of carboxylic acid and/or ammonium carboxylate, 0.01 to 45 percent of ammonium carbonate and/or ammonium bicarbonate, 0.0001 to 20 percent of one or more selected from hydroxylamine hydrochloride, hydroxylamine sulphate and hydrazine hydrate, the balance being water. The initial feed amount B of copper chloride is calculated according to the following formula: B=(134.5/63.5)x the set value of the copper ion concentration A; the control parameter of the production process of the resulting etchant is set to be: the copper ion concentration of 30-170 g/L.

Claims

1. An alkaline cupric chloride etchant for printed circuit board, comprising cupric chloride and a sub-etchant, wherein an automatic detection and feeding control machine is used for controlling the specific gravity of the etchant, in order to keep the concentration of copper ions in the etchant to be no less than a set value; the sub-etchant comprises the following components in percentage by weight: 10%-30% NH.sub.4Cl; 0.0002%-25% of a first composition, wherein the first composition is carboxylic acid, ammonium carboxylate or a combination thereof; 0.01%-45% of a second composition, wherein the second composition is ammonium carbonate, ammonium bicarbonate or a combination thereof; 0.0001%-20% of a third composition, wherein the third composition is one or more compounds selected from hydroxylamine hydrochloride, hydroxylamine sulphate, and hydrazine hydrate; and the balance of water; the initial feed amount B of the cupric chloride is obtained by calculation according to the following formula:
B=(134.5/63.5)×set value A of the concentration of copper ions; control parameters of a production process of the etchant are set as follows: the concentration of copper ions is 30-170 g/L.

2. The high efficiency and environmental friendly alkaline cupric chloride etchant according to claim 1, wherein the sub-etchant comprises the following components in percentage by weight: 15%-30% NH.sub.4Cl; 0.5%-13% of the first composition; 2%-30% of the second composition; 0.01%-15% of the third composition; and the balance of water.

3. The alkaline cupric chloride etchant according to claim 2, wherein the sub-etchant comprises the following components in percentage by weight: 15%-25% NH.sub.4Cl; 1%-10% of the first composition; 5%-25% of the second composition; 0.1%-10% the third composition; and the balance of water.

4. The alkaline cupric chloride etchant according to claim 1, wherein the carboxylic acid is one or more compounds selected from the group comprising formic acid, citric acid and malic acid; the ammonium carboxylate is one or more compounds selected from the group comprising ammonium formate, ammonium citrate and ammonium malate.

5. The alkaline cupric chloride etchant according to claim 1, wherein the etchant further comprises ammonium hydroxide.

6. The alkaline cupric chloride etchant according to claim 5, wherein, based on percentage by weight of the etchant, the etchant further comprises ≤25% by weight of ammonium hydroxide.

7. The alkaline cupric chloride etchant according to claim 6, wherein the control parameters of the production process of the etchant are set as follows: the concentration of copper ions is 30-170 g/L, the pH value is 7.0-8.8.

8. The alkaline cupric chloride etchant according to claim 7, wherein the control parameters of the production process of the etchant are set as follows: the concentration of copper ions is 40-160 g/L, the pH value is 7.0-8.4.

Description

DESCRIPTION OF THE EMBODIMENTS

(1) The invention is further described by the following exemplary embodiments. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. Nonessential modification and adjustments made by other people according to the invention still belong to the protection scope of the invention.

(2) In the following exemplary embodiments and comparative examples, the ammonium chloride used is preferably ammonium chloride produced by Guangzhou Chemical Reagent Factory; the formic acid used is preferably formic acid produced by Guangzhou Chemical Reagent Factory; the ammonium formate used is preferably ammonium formate produced by Guangzhou Chemical Reagent Factory; the ammonium hydroxide used is preferably ammonium hydroxide produced by Guangzhou Chemical Reagent Factory; the cupric chloride used is preferably CuCl.sub.2.2H.sub.2O (≥99.0%) produced by Guangzhou Chemical Reagent Factory; the citric acid used is preferably citric acid produced by Guangzhou Chemical Reagent Factory; the malic acid used is preferably DL-malic acid produced by Guangzhou Chemical Reagent Factory; the ammonium citrate used is preferably ammonium citrate produced by Guangzhou Chemical Reagent Factory; the ammonium malate used is preferably ammonium malate produced by Xi'an Dafengshou Biotech Co., Ltd.; the ammonium carbonate used is preferably ammonium carbonate produced by Shanghai Hengyuan Biotech Co., Ltd.; the ammonium bicarbonate used is preferably ammonium bicarbonate produced by Shanghai Lanke Medical Science and Technology Development Co., Ltd.; the hydroxylamine hydrochloride used is preferably hydroxylamine hydrochloride produced by Jiangsu Aikewei Science and Technology Co., Ltd.; the hydroxylamine sulphate used is preferably hydroxylamine sulphate produced by Jiangsu Aikewei Science and Technology Co., Ltd.; the hydrazine hydrate used is preferably hydrazine hydrate produced by Shandong Kaisitong Chemical Co., Ltd. The automatic detection and feeding control machines used are preferably Yegao PCB alkaline etching automatic feeding control machine type-2 which is produced by Guangzhou Yegao Chemical Co., Ltd. In addition to the above-listed products, those of skill in the art can also select products and equipments with similar properties to those listed herein according to conventional choices to achieve the object of the current invention.

Embodiment 1

(3) Step 1: at ambient temperature and pressure, according to the designated components as illustrated in Table 1 below, selected raw materials are dissolved in water to prepare the sub-etchant.

(4) Step 2: cupric chloride was added into per liter of the sub-etchant obtained in step 1; the added amount of cupric chloride was obtained by calculation according to the set value of the concentration of copper ions in the solution listed in Table 1:

(5) $\begin{array}{cc}\frac{\mathrm{molar}\mathrm{mass}\mathrm{of}{\mathrm{CuCl}}_2}{\begin{array}{c}\mathrm{molar}\mathrm{mass}\mathrm{of}\mathrm{copper}\\ \mathrm{ion}\end{array}}=\frac{\begin{array}{c}\mathrm{mass}\mathrm{of}{\mathrm{CuCl}}_2\mathrm{to}\mathrm{be}\mathrm{added}\\ \mathrm{per}\mathrm{liter}\mathrm{of}\text{sub-etchant}\end{array}}{\begin{array}{c}\mathrm{mass}\mathrm{of}\mathrm{copper}\mathrm{ion}\mathrm{to}\mathrm{be}\\ \mathrm{added}\mathrm{per}\mathrm{liter}\mathrm{of}\\ \text{sub-etchant}\end{array}}& \left(\mathrm{Formula}1\right)\end{array}$

(6) Wherein the molar mass of cupric chloride is 134.5 g/mol; and the molar mass of copper ion is 63.5 g/mol. According to the value specified in embodiment 1 of Table 1, the mass of cupric chloride to be added into per liter of sub-etchant is 190.6 g.

(7) Step 3: the solution obtained in step 2 was poured into an etchant tank, and sensor probes of the automatic detection and feeding control machine were immersed into the etchant.

(8) Step 4: the sub-etchant obtained in step 1 was poured into a sub-etchant supplement tank, which was connected to a charging pump controlled by a specific gravity numerical control meter of the automatic detection and feeding control machine; the temperature of the etchant tank was set to 50° C., the pressure of spray nozzles of the etching machine was set to 2 kg/cm.sup.2.

(9) Step 5: the etching operation was started. Sub-etchant was automatically charged and all the components in the etchant were balanced by the automatic detection and feeding control machine, keeping the specific gravity at the numerical values specified; the concentration of copper ions and pH value of the etchant detected by the automatic detection and feeding control machine during etching process were recorded in Table 1.

(10) Test on Etch Quality

(11) The test was carried out using PCBs with size of 620×540 mm, copper foil thickness of 1 oz, line width and line spacing of 50.8 μm and pure copper etching rate test boards with size of 500×300×1.5 mm via spray corrosion testing in an etching machine. The etching rate and etch factor K were calculated using methods known in the art, e.g., those described in Printed Circuit Technique by Li Xueming, Occupational Skill Testing Authority of Electronic Industry of Ministry of Industry and Information Technology, fifth edition, p 387-389; “Theory and Application of Metal Corrosion”, Wei Baoming, Chemical Industry Press, p 5-7; Discussion in Methods of Etch Factor Calculation, Tian Ling, et al., printed circuit information, 2007 No. 12, p 55-56. The calculated results of etching rate and etch factor K are presented in Table 2.

(12) Testing the Impact on Photoresists:

(13) When the various process parameters arrived at set numerical values, printed circuit test boards with the size of 500×300×1.5 mm, and are coated with either liquid or dry film photoresists, were employed for spray corrosion testing in the etching machine for 1 min. The automatic detection and feeding control machine automatically recharged and balanced each component in the etchant, keeping the pH value and the specific gravity at prescribed numerical values specified in Table 1. The liquid or dry film photoresists were carefully scrutinized and gently scratched using equipment in order to observe whether there is discoloration, softening or stripping of the photoresists. The results of the test are recorded in Table 3.

Embodiments 2-3

(14) The procedures of embodiment 1 were repeated respectively, using the designated content of each component and parameters of the automatic detection and feeding control machine as specified in embodiments 2-3 of Table 1 below.

(15) Etch quality test was carried out as mentioned in embodiment 1.

Embodiments 4-5

(16) The procedures of embodiment 1 were repeated respectively, using the designated content of each component and parameters of the automatic detection and feeding control machine as specified in embodiments 4-5 of Table 1 below. Wherein in step 2, 63.5 g of cupric chloride was added into per liter of the sub-etchant obtained in step 1 to allow the concentration of copper ions in the obtained solution to reach the value specified in embodiments 4-5 of Table 1.

(17) Etch quality test was carried out as mentioned in embodiment 1.

Embodiments 6-7

(18) The procedures of embodiment 1 were repeated respectively, using the designated content of each component and parameters of the automatic detection and feeding control machine as specified in embodiments 6-7 of Table 1 below. Wherein in step 2, 84.7 g of cupric chloride was added into per liter of the sub-etchant obtained in step 1 to allow the concentration of copper ions in the obtained solution to reach the value specified in embodiments 6-7 of Table 1.

(19) Etch quality test was carried out as mentioned in embodiment 1.

Embodiments 8

(20) The procedures of embodiment 1 were repeated respectively, using the designated content of each component and parameters of the automatic detection and feeding control machine as specified in embodiments 8 of Table 1 below. Wherein in step 2, 127 g of cupric chloride was added into per liter of the sub-etchant obtained in step 1 to allow the concentration of copper ions in the obtained solution to reach the value specified in embodiments 8 of Table 1.

(21) Etch quality test and impact testing on photoresists were carried out as mentioned in embodiment 1.

Embodiments 9

(22) The procedures of embodiment 1 were repeated respectively, using the designated content of each component and parameters of the automatic detection and feeding control machine as specified in embodiments 9 of Table 1 below. Wherein in step 2, 127 g of cupric chloride was added into per liter of the sub-etchant obtained in step 1 to allow the concentration of copper ions in the obtained solution to reach the value specified in embodiments 9 of Table 1.

(23) Etch quality test was carried out as mentioned in embodiment 1.

Embodiments 10

(24) The procedures of embodiment 1 were repeated respectively, using the designated content of each component and parameters of the automatic detection and feeding control machine as specified in embodiments 10 of Table 1 below. Wherein in step 2, 317.7 g of cupric chloride was added into per liter of the sub-etchant obtained in step 1 to allow the concentration of copper ions in the obtained solution to reach the value specified in embodiments 10 of Table 1.

(25) Etch quality test was carried out as mentioned in embodiment 1.

Embodiment 11

(26) The procedures of embodiment 1 were repeated respectively, using the designated content of each component and parameters of the automatic detection and feeding control machine as specified in embodiments 11 of Table 1 below. Wherein in step 2, 360 g of cupric chloride was added into per liter of the sub-etchant obtained in step 1 to allow the concentration of copper ions in the obtained solution to reach the value specified in embodiments 11 of Table 1.

(27) Etch quality test was carried out as mentioned in embodiment 1.

Embodiment 12

(28) The procedures of embodiment 1 were repeated respectively, using the designated content of each component and parameters of the automatic detection and feeding control machine as specified in embodiments 12 of Table 1 below. Wherein in step 2, 63.5 g of cupric chloride was added into per liter of the sub-etchant obtained in step 1 to allow the concentration of copper ions in the obtained solution to reach the value specified in embodiments 12 of Table 1.

(29) Etch quality test was carried out as mentioned in embodiment 1.

Embodiment 13

(30) The procedures of embodiment 1 were repeated respectively, using the designated content of each component and parameters of the automatic detection and feeding control machine as specified in embodiments 13 of Table 1 below. Wherein in step 2, 84.7 g of cupric chloride was added into per liter of the sub-etchant obtained in step 1 to allow the concentration of copper ions in the obtained solution to reach the value specified in embodiments 13 of Table 1.

(31) Etch quality test was carried out as mentioned in embodiment 1.

Embodiment 14

(32) The procedures of embodiment 1 were repeated respectively, using the designated content of each component and parameters of the automatic detection and feeding control machine as specified in embodiments 14 of Table 1 below. Wherein in step 2, 127 g of cupric chloride was added into per liter of the sub-etchant obtained in step 1 to allow the concentration of copper ions in the obtained solution to reach the value specified in embodiments 14 of Table 1.

(33) Etch quality test was carried out as mentioned in embodiment 1.

Embodiment 15

(34) The procedures of embodiment 1 were repeated respectively, using the designated content of each component and parameters of the automatic detection and feeding control machine as specified in embodiments 15 of Table 1 below. Wherein in step 2, 317.7 g of cupric chloride was added into per liter of the sub-etchant obtained in step 1 to allow the concentration of copper ions in the obtained solution to reach the value specified in embodiments 15 of Table 1.

(35) Etch quality test was carried out as mentioned in embodiment 1.

Embodiment 16

(36) The procedures of embodiment 1 were repeated respectively, using the designated content of each component and parameters of the automatic detection and feeding control machine as specified in embodiments 16 of Table 1 below. Wherein in step 2, 360 g of cupric chloride was added into per liter of the sub-etchant obtained in step 1 to allow the concentration of copper ions in the obtained solution to reach the value specified in embodiments 16 of Table 1.

(37) Etch quality test was carried out as mentioned in embodiment 1.

Embodiment 17

(38) The procedures of embodiment 1 were repeated respectively, using the designated content of each component and parameters of the automatic detection and feeding control machine as specified in embodiments 17 of Table 1 below. Wherein in step 2, 63.5 g of cupric chloride was added into per liter of the sub-etchant obtained in step 1 to allow the concentration of copper ions in the obtained solution to reach the value specified in embodiments 17 of Table 1.

(39) Etch quality test was carried out as mentioned in embodiment 1.

Embodiment 18

(40) The procedures of embodiment 1 were repeated respectively, using the designated content of each component and parameters of the automatic detection and feeding control machine as specified in embodiments 18 of Table 1 below. Wherein in step 2, 84.7 g of cupric chloride was added into per liter of the sub-etchant obtained in step 1 to allow the concentration of copper ions in the obtained solution to reach the value specified in embodiments 18 of Table 1.

(41) Etch quality test was carried out as mentioned in embodiment 1.

Embodiments 19

(42) The procedures of embodiment 1 were repeated respectively, using the designated content of each component and parameters of the automatic detection and feeding control machine as specified in embodiments 19 of Table 1 below. Wherein in step 2, 127 g of cupric chloride was added into per liter of the sub-etchant obtained in step 1 to allow the concentration of copper ions in the obtained solution to reach the value specified in embodiments 19 of Table 1.

(43) Etch quality test and impact testing on photoresists were carried out as mentioned in embodiment 1.

Embodiment 20

(44) The procedures of embodiment 1 were repeated respectively, using the designated content of each component and parameters of the automatic detection and feeding control machine as specified in embodiments 20 of Table 1 below. Wherein in step 2, 317.7 g of cupric chloride was added into per liter of the sub-etchant obtained in step 1 to allow the concentration of copper ions in the obtained solution to reach the value specified in embodiments 20 of Table 1.

(45) Etch quality test and impact testing on photoresists were carried out as mentioned in embodiment 1.

Embodiment 21

(46) Step 1: at ambient temperature and pressure, according to the designated components as illustrated in Table 1 below, selected raw materials are dissolved in water to prepare the sub-etchant. In addition, 25% ammonium hydroxide was prepared;

(47) Step 2: cupric chloride was added into per liter of the sub-etchant obtained in step 1; the added amount of cupric chloride was obtained by calculation according to the set value of the concentration of copper ions in the solution listed in Table 1:

(48) $\begin{array}{cc}\frac{\mathrm{molar}\mathrm{mass}\mathrm{of}{\mathrm{CuCl}}_2}{\begin{array}{c}\mathrm{molar}\mathrm{mass}\mathrm{of}\mathrm{copper}\\ \mathrm{ion}\end{array}}=\frac{\begin{array}{c}\mathrm{mass}\mathrm{of}{\mathrm{CuCl}}_2\mathrm{to}\mathrm{be}\mathrm{added}\\ \mathrm{per}\mathrm{liter}\mathrm{of}\text{sub-etchant}\end{array}}{\begin{array}{c}\mathrm{mass}\mathrm{of}\mathrm{copper}\mathrm{ion}\mathrm{to}\mathrm{be}\\ \mathrm{added}\mathrm{per}\mathrm{liter}\mathrm{of}\\ \text{sub-etchant}\end{array}}& \left(\mathrm{Formula}1\right)\end{array}$

(49) Wherein the molar mass of cupric chloride is 134.5 g/mol; and the molar mass of copper ion is 63.5 g/mol. The mass of cupric chloride to be added into per liter of sub-etchant is 360 g according to the value specified in embodiment 21 of Table 1.

(50) Step 3: the solution obtained in step 2 was poured into an etchant tank, and sensor probes of the automatic detection and feeding control machine were immersed into the etchant.

(51) Step 4: the 25% of ammonium hydroxide obtained in step 1 was poured into an ammonium hydroxide supplement tank, which was connected to a charging pump controlled by a pH numerical control meter of the automatic detection and feeding control machine; the sub-etchant obtained in step 1 was poured into a sub-etchant supplement tank, which was connected to a charging pump controlled by a specific gravity numerical control meter of the automatic detection and feeding control machine.

(52) Step 5: the temperature of the etchant tank was set to 50° C., the pressure of spray nozzles of the etching machine was set to 2 kg/cm.sup.2, and the pH value was set as the value specified in Table 1. The automatic detection and feeding control machine was started and the etchant was prepared; when the pH of the etchant arrived at the set numerical value, the numerical value of the specific gravity numerical control meter was set according to the reading of a hydrometer on the automatic detection and feeding control machine.

(53) Step 6: the etching operation was started. All the components in the etchant were automatically charged and balanced by the automatic detection and feeding control machine, keeping the pH value and the specific gravity at the numerical values specified in Table 1.

(54) Etch quality test and impact testing on photoresists were carried out as mentioned in embodiment 1.

Comparative Example 1

(55) Step 1: at ambient temperature and pressure, according to the designated components as listed in Table 1 below, selected raw materials are dissolved in water to prepare the sub-etchant.

(56) Step 2: cupric chloride was added into per liter of the sub-etchant obtained in step 1; the added amount of cupric chloride was obtained by calculation according to the set value of the concentration of copper ions in the solution listed in Table 1:

(57) $\begin{array}{cc}\frac{\mathrm{molar}\mathrm{mass}\mathrm{of}{\mathrm{CuCl}}_2}{\begin{array}{c}\mathrm{molar}\mathrm{mass}\mathrm{of}\mathrm{copper}\\ \mathrm{ion}\end{array}}=\frac{\begin{array}{c}\mathrm{mass}\mathrm{of}{\mathrm{CuCl}}_2\mathrm{to}\mathrm{be}\mathrm{added}\\ \mathrm{per}\mathrm{liter}\mathrm{of}\text{sub-etchant}\end{array}}{\begin{array}{c}\mathrm{mass}\mathrm{of}\mathrm{copper}\mathrm{ion}\mathrm{to}\mathrm{be}\\ \mathrm{added}\mathrm{per}\mathrm{liter}\mathrm{of}\\ \text{sub-etchant}\end{array}}& \left(\mathrm{Formula}1\right)\end{array}$

(58) Wherein the molar mass of cupric chloride is 134.5 g/mol; and the molar mass of copper ion is 63.5 g/mol. The mass of cupric chloride to be added into per liter of sub-etchant is 127 g according to the value specified in Table 1.

(59) Step 3: the solution obtained in step 2 was poured into an etchant tank, and sensor probes of the automatic detection and feeding control machine were immersed into the etchant.

(60) Step 4: the sub-etchant obtained in step 1 was poured into a sub-etchant tank, which was connected to the charging pump controlled by a specific gravity numerical control meter of the automatic detection and feeding control machine; an 20% ammonium hydroxide solution was poured into an ammonium hydroxide supplement tank, which was connected to a charging pump controlled by a pH numerical control meter of the automatic detection and feeding control machine; the temperature of the etchant tank was set to 50° C., the pressure of spray nozzles of the etching machine was set as 2 kg/cm.sup.2.

(61) Step 5: the etching operation was started. The sub-etchant and the ammonium hydroxide solution were automatically charged and all the components in the etchant were balanced by the automatic detection and feeding control machine, keeping the specific gravity at 1.20 g/ml and the pH value at 7.2.

(62) Test on Etch Quality

(63) The test was carried out using PCBs with size of 620×540 mm, copper foil thickness of 1 oz, line width and line spacing of 50.8 μm and pure copper etching rate test boards with size of 500×300×1.5 mm via spray corrosion testing in an etching machine. The etching rate and etch factor K were calculated using methods known in the art, e.g., those described in Printed Circuit Technique by Li Xueming, Occupational Skill Testing Authority of Electronic Industry of Ministry of Industry and Information Technology, fifth edition, p 387-389; “Theory and Application of Metal Corrosion”, Wei Baoming, Chemical Industry Press, p 5-7; Discussion in Methods of Etch Factor Calculation, Tian Ling, et al., printed circuit information, 2007 No. 12, p 55-56. The calculated results of etching rate and etch factor K are presented in Table 2.

Comparative Examples 2

(64) Step 1: at ambient temperature and pressure, according to the designated components as listed in Table 1 below, selected raw materials are dissolved in water to prepare the sub-etchant.

(65) Step 2: cupric chloride was added into per liter of the sub-etchant obtained in step 1; the added amount of cupric chloride was obtained by calculation according to the set value of the concentration of copper ions in the solution listed in Table 1:

(66) $\begin{array}{cc}\frac{\mathrm{molar}\mathrm{mass}\mathrm{of}{\mathrm{CuCl}}_2}{\begin{array}{c}\mathrm{molar}\mathrm{mass}\mathrm{of}\mathrm{copper}\\ \mathrm{ion}\end{array}}=\frac{\begin{array}{c}\mathrm{mass}\mathrm{of}{\mathrm{CuCl}}_2\mathrm{to}\mathrm{be}\mathrm{added}\\ \mathrm{per}\mathrm{liter}\mathrm{of}\text{sub-etchant}\end{array}}{\begin{array}{c}\mathrm{mass}\mathrm{of}\mathrm{copper}\mathrm{ion}\mathrm{to}\mathrm{be}\\ \mathrm{added}\mathrm{per}\mathrm{liter}\mathrm{of}\\ \text{sub-etchant}\end{array}}& \left(\mathrm{Formula}1\right)\end{array}$

(67) Wherein the molar mass of cupric chloride is 134.5 g/mol; and the molar mass of copper ion is 63.5 g/mol. The mass of cupric chloride to be added into per liter of sub-etchant is 63.5 g according to the value specified in Table 1.

(68) Step 3: the solution obtained in step 2 was poured into an etchant tank, and sensor probes of the automatic detection and feeding control machine were immersed into the etchant.

(69) Step 4: the sub-etchant obtained in step 1 was poured into a sub-etchant tank, which was connected to the charging pump controlled by a specific gravity numerical control meter of the automatic detection and feeding control machine; the temperature of the etchant tank was set to 50° C., the pressure of spray nozzles of the etching machine was set as 2 kg/cm.sup.2.

(70) Step 5: the etching operation was started. The sub-etchant was automatically charged and all the components in the etchant were balanced by the automatic detection and feeding control machine, keeping the specific gravity at the numerical values specified in Table 1.

(71) Test on Etch Quality

(72) The test was carried out using PCBs with size of 620×540 mm, copper foil thickness of 1 oz, line width and line spacing of 50.8 μm and pure copper etching rate test boards with size of 500×300×1.5 mm via spray corrosion testing in an etching machine. The etching rate and etch factor K were calculated using methods known in the art, e.g., those described in Printed Circuit Technique by Li Xueming, Occupational Skill Testing Authority of Electronic Industry of Ministry of Industry and Information Technology, fifth edition, p 387-389; “Theory and Application of Metal Corrosion”, Wei Baoming, Chemical Industry Press, p 5-7; Discussion in Methods of Etch Factor Calculation, Tian Ling, et al., printed circuit information, 2007 No. 12, p 55-56. The calculated results of etching rate and etch factor K are presented in Table 2.

Comparative Examples 3

(73) The procedures of comparative example 2 were repeated respectively, using the designated content of each component and parameters of the automatic detection and feeding control machine as specified in comparative example 3 of Table 1 below. Wherein in step 2, 127 g of cupric chloride was added into per liter of the sub-etchant obtained in step 1 to allow the concentration of copper ions in the obtained solution to reach the value specified in comparative example 3 of Table 1.

(74) Etch quality test was carried out as mentioned in comparative example 2.

Comparative Examples 4

(75) The procedures of comparative example 2 were repeated respectively, using the designated content of each component and parameters of the automatic detection and feeding control machine as specified in comparative example 4 of Table 1 below. Wherein in step 2, 317.7 g of cupric chloride was added into per liter of the sub-etchant obtained in step 1 to allow the concentration of copper ions in the obtained solution to reach the value specified in comparative example 4 of Table 1.

(76) Etch quality test was carried out as mentioned in comparative example 2.

(77) Testing the Impact on Photoresists:

(78) When the various process parameters of the automatic detection and feeding control machine in step 3 arrived at set numerical values, printed circuit test boards with the size of 500×300×1.5 mm, were coated with either liquid or dry film photoresists, and were employed for spray corrosion testing in the etching machine for 1 min. The automatic detection and feeding control machine automatically recharged and balanced each component in the etchant, keeping the pH value and the specific gravity at prescribed numerical values specified in Table 1. The liquid or dry film photoresists were carefully scrutinized and gently scratched using equipment in order to observe whether there is discoloration, softening or stripping of the photoresists. The results of the test are recorded in Table 3.

(79) Data Analysis of Tables 1-3:

(80) Comparative example 1 belongs to the etching system mentioned in the application of Chinese invention CN201510176486.9. Comparing comparative example 1 with embodiment 19, both etchant have the same pH value and concentration of copper ions with each other, whereas a higher etching rate and larger etch factor were obtained in embodiment 19. Therefore the etching system of the invention has a better etching speed and better etching quality.

(81) Comparative example 2-4 are commonly-seen traditional alkaline etching systems at present. According to the results, the etching speeds were extremely low when the pH value was less than 8, and that shows traditional alkaline etching systems with a pH value below 8 are unsuitable for industrialized production. Wherein, comparative example 4 has an identical pH value and concentration of copper ions with embodiment 10, embodiment 15 and embodiment 20, but the etching rates and the etch factors of the three embodiment are all better than those of comparative example 4. It can be seen that the etching system of the invention has a better etching speed and better etching quality.

(82) TABLE-US-00001 TABLE 1 Concentration of Sub-etchant copper Specific Ammonium Ammonium Ammonium Formic Ammonium ions gravity water chloride bicarbonate carbonate acid Formate Etching system g/L pH g/ml wt % wt % wt % wt % wt % wt % Comparative 60.01 8.0 1.17 72 22 0 0 5 0 example 1 Comparative 30 7.0 1.10 55 20 0 0 0 0 example 2 Comparative 60.01 8.0 1.13 55 20 0 0 0 0 example 3 Comparative 160 8.8 1.22 55 20 0 0 0 0 example 4 Embodiment 1 90 7.2 1.17 49.7 22 0 18 3 0 Embodiment 2 90 7.2 1.17 54.5 22 0 18 0 3 Embodiment 3 90 7.6 1.17 49.4 22 0.3 18 2.5 0.1 Embodiment 4 30 7.0 1.18 26 10 0 19 20 5 Embodiment 5 30 7.0 1.27 15 10 37 8 25 0 Embodiment 6 40 7.8 1.19 26 10 0 9 10 11 Embodiment 7 40 8.0 1.28 13 10 25 20 25 0 Embodiment 8 60.01 7.8 1.21 26 10 0 9 10 11 Embodiment 9 60.01 8.0 1.30 13 10 25 20 25 0 Embodiment 10 160 8.8 1.23 54.99 30 0.01 0 0.0002 0 Embodiment 11 170 8.4 1.25 54.99 30 0 0.01 0.0002 0 Embodiment 12 30 7.0 1.23 27 15 18 12 0 13 Embodiment 13 40 8.0 1.24 17 15 15 15 3 2 Embodiment 14 60.01 8.0 1.26 17 15 15 15 3 2 Embodiment 15 160 8.8 1.23 47.49 30 2 0 0 0 Embodiment 16 170 8.4 1.25 47.49 30 1 1 0 0 Embodiment 17 30 7.0 1.21 40 15 8 17 5 1 Embodiment 18 40 8.0 1.23 30 15 10 15 0 5 Embodiment 19 60.01 8.0 1.25 30 15 10 15 0 5 Embodiment 20 160 8.8 1.23 43.9 25 0 5 0 0 Embodiment 21 170 8.4 1.25 68.9 25 4 1 0 0 Sub-etchant Hydroxyl- Hydroxyl- Malic Ammonium Citric Ammonium amine amine Hydrazine- Ammonium acid malate acid citrate hydrochloride sulphate hydrate hydroxide Etching system wt % wt % wt % wt % wt % wt % wt % wt % Comparative 0 0 0 0 0 0 0 1 example 1 Comparative 0 0 0 0 0 0 0 25 example 2 Comparative 0 0 0 0 0 0 0 25 example 3 Comparative 0 0 0 0 0 0 0 25 example 4 Embodiment 1 0 0 0 0 1.3 0 0 6 Embodiment 2 0 0 0 0 0 0 2.5 0 Embodiment 3 0.1 0.1 0.1 0.1 0 1.3 0 6 Embodiment 4 0 0 0 0 0 0 20 0 Embodiment 5 0 0 0 0 0 0 5 0 Embodiment 6 1 1 1 1 1 1 18 10 Embodiment 7 0 0 0 0 0 0 5 2 Embodiment 8 1 1 1 1 1 1 18 10 Embodiment 9 0 0 0 0 0 0 5 2 Embodiment 10 0 0 0 0 0 0.0001 0 15 Embodiment 11 0 0 0 0 0 0.0001 0 15 Embodiment 12 0 0 0 0 1 0 14 0 Embodiment 13 2 2 2 2 1 1 13 10 Embodiment 14 2 2 2 2 1 1 13 10 Embodiment 15 0.5 0 0 0 0 0.01 0 20 Embodiment 16 0.5 0 0 0 0.01 0 0 20 Embodiment 17 1 1 1 1 0 0 10 0 Embodiment 18 0 0 0 5 1 1 8 10 Embodiment 19 0 0 0 5 1 1 8 10 Embodiment 20 1 0 0 0 0 0.1 0 25 Embodiment 21 0 0.5 0.5 0 0 0.1 0 0

(83) TABLE-US-00002 TABLE 2 Etching Etching rate Etch factor Environmental system (μm/min) K impact Comparative 55 6.8 Slight ammonia odor example 1 Comparative 12 1.5 Slight ammonia odor example 2 Comparative 55 6.0 Obvious ammonia odor example 3 Comparative 60 5.0 Obvious ammonia odor example 4 Embodiment 1 35 13.2 No ammonia odor Embodiment 2 40 12.9 No ammonia odor Embodiment 3 45 15.1 No ammonia odor Embodiment 4 23 15.3 Almost no ammonia odor Embodiment 5 22 15.1 Almost no ammonia odor Embodiment 6 36 8.9 Almost no ammonia odor Embodiment 7 40 9.1 Almost no ammonia odor Embodiment 8 55 9.4 Almost no ammonia odor Embodiment 9 59 9.8 Almost no ammonia odor Embodiment 10 62 5.5 Obvious ammonia odor Embodiment 11 60 7.7 Obvious ammonia odor Embodiment 12 24 16.4 Almost no ammonia odor Embodiment 13 39 9.0 Slight ammonia odor Embodiment 14 58 8.9 Slight ammonia odor Embodiment 15 63 6.3 Obvious ammonia odor Embodiment 16 55 6.0 Obvious ammonia odor Embodiment 17 22 20.1 Almost no ammonia odor Embodiment 18 42 13 Slight ammonia odor Embodiment 19 56 15.8 Slight ammonia odor Embodiment 20 61 6.3 Obvious ammonia odor Embodiment 21 65 6.8 Obvious ammonia odor

(84) TABLE-US-00003 TABLE 3 Etching pH Type of system value photoresist Observation of etch resist Comparative 8.8 dry-film No discoloration; partly striped example 4 after gentle scratching liquid No discoloration; partly striped after gentle scratching Embodiment 1 7.2 dry-film Not discolored, softened or striped liquid Not discolored, softened or striped Embodiment 8 7.8 dry-film Not discolored, softened or striped liquid Not discolored, softened or striped Embodiment 19 8.0 dry-film No discoloration; partly striped after gentle scratching liquid No discoloration; partly striped after gentle scratching

(85) It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed embodiments without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the disclosure covers modifications and variations provided that they fall within the scope of the following claims and their equivalents.