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How To Control Copper Plating Quality for PCB Board
Nov 01, 2017

PCB hole metallization is one of the key technologies of printed circuit board manufacturing.Controlling hole metallization quality strictly is the prerequisite for the final product quality, while the key point is to control the quality of the plating copper layer.The common test and control methods are as follows:

1.Determination of chemical deposition rate for PCB circuit board:

Chemical copper plating is used to have certain technical requirements for copper deposition rate.The rate is too slow may cause holes or pinholes in the hole wall; too fast will make a rough coating. For this reason, scientific determination of copper precipitation rate is one way to control the quality of copper.Herein, below is the method of determination of copper deposition rate.

(1) material: the epoxy base material etched copper,size 100 x 100(mm)

(2) measurement procedure:

A. Bake sample in 120-140 ℃ for 1 hour, and weight it by analytical balance after cooling,record W1(g); 

B. Put the sample in 350-370 g/l chromium anhydride and 208-228g/l sulfuric acid mixture(65 ℃) and corrode 10 minutes, rinse clean by water;

C.Put the sample in waste liquid removed chrome and treat(30-40℃) for 3-5 minutes, then wash clean; 

D.Based on the process conditions do presoaking, activating and treat in redox liquid; 

E. in copper plating liquid (25℃) etch copper half an hour,then wash clean; 

F. Baking the sample for 1 hour in 120-140℃ to be constant weight, record W2(g). 

(3) calculation for immersion copper rate:

Rate=(W2-W1)104/8.93 * 10 *10x10x0.5x2(um)

(4) comparison and judgment:

Compare and judge the measurement results with the data provided by the process data. 


2.Etching rate determination method  for PCB circuit board

Before the hole plating, the copper foil is treated with microetching to increase the binding force with the copper layer.To ensure the stability of etching solution and the uniformity of copper foil etching, the determination of etching rate is required to ensure that it is within the scope of process regulation. 

(1) materials: 0.3mm copper foil clad plate, after removed oil and brushed, then cut into 100x100(mm); 

(2) determination procedure:

A.Sample is corroded in hydrogen peroxide(80-100g/l) and sulfuric acid(160-210 g/l) for 2 minutes in 30 ℃,then clean, washed by deionized water; 

B.Bake the sample in 120-140 ℃ for 1 hour, then weight after be weight constantly,record W2(g), the sample also be weighed before corrosion with the same conditions,record W1(g). 

(3) calculation of etching rate

Rate=(w1-w2)104/2x8.933T(um/min)

In the equation: s-sample area(cm2) T-etching time(min)

(4) judgment: corrosion rate@1-2um/min is appropriate.(1.5-5minutes etch copper 270-540mg). 


3.Glass cloth test method for PCB circuit board

In the process of hole metallization, the activation and immersion copper is the key process of electroplating. Although qualitative and quantitative analysis ion palladium and liquid can reflect activation reduction performance, reliability is not equal to glass cloth test.But glass cloth heavy copper condition is most strict, it can display most performance of activated, reduced and submerged copper liquid.The introduction is as follows:

(1) material: the glass cloth is removed in 10% sodium hydroxide solution and cut it to 50x50(mm), and remove some glass fiber at the end of the four sides, so that the glass will disperse. 

(2) test procedures:

A.The sample is processed according to the copper plating process;    B.Put the sample in the copper immersed liquid, the glass cloth end should be immersed copper completely in 10 seconds, show in black or dark brown. After 2 minutes, all will be immersed completely, and copper color will be deepen after 3 minutes.For heavy copper, after 10 seconds the glass cloth end must be immersed copper completely, 30-40 seconds later, all are immersed copper. 

C.Judgment: if the above copper effect is achieved, the performance of activation, reduction and precipitation is good;if not, the perormance is bad.