Electroless Plating Copper is commonly known as immersion copper. Circuit board hole metallization technology is one of the keys to printed circuit board manufacturing technology. Strictly controlling the quality of hole metallization is the premise to ensure the quality of the final product, while controlling the quality of the copper immersion layer is the key. The routine test control methods are as follows:
1. Determination of chemical copper deposition rate:
The use of electroless copper plating solution has certain technical requirements for the copper deposition rate. If the rate is too slow, it may cause voids or pinholes in the hole wall; and if the rate of copper sinking is too fast, the coating will be rough. For this reason, the scientific determination of the copper deposition rate is one of the means to control the quality of the copper deposition. Taking the electroless copper plating provided by Schering as an example, the method for measuring copper sinking rate is introduced:
1. Material: The epoxy base material after copper etching is used, and the size is 100 × 100 (mm).
2. Measurement steps:
2.1. Bake the sample at 120-140℃ for 1 hour, and then use an analytical balance to weigh W1(g);
2.2. Corrosion for 10 minutes in a mixture of 350-370 g/L chromic anhydride and 208-228 mL/L sulfuric acid (temperature 65°C), and rinse with clean water;
2.3. Treat it in the waste liquid of chromium removal (temperature 30-40℃) for 3-5 minutes and wash it clean;
2.4. Pre-dip, activate, and process in reducing solution according to process conditions;
2.5. Immerse copper in copper precipitation solution (temperature 25℃) for half an hour and clean it;
2.6. Bake the test piece at 120-140℃ for 1 hour to constant weight, and weigh W2(g).
2.7. Calculation of copper sinking rate: rate=(W2-W1)104/8.93×10×10×0.5×2(μm)
2.8. Comparison and judgment: compare and judge the measurement results with the data provided by the process data.
2. Determination method of etching rate of etching solution
Before the through-hole plating, the copper foil is micro-etched to make the micro-roughening, so as to increase the bonding force with the copper sink layer. In order to ensure the stability of the etching solution and the uniformity of the copper foil etching, the etching rate needs to be measured to ensure that it is within the range specified by the process.
1. Material: 0.3mm copper clad laminate, degreasing, brushing, and cut into 100×100(mm);
2. Determination procedure: A. The sample is corroded in hydrogen peroxide (80-100 g/L) and sulfuric acid (160-210 g/L) at a temperature of 30°C for 2 minutes, washed with deionized water; B. At 120- Bake at 140°C for 1 hour, weigh W2 (g) after constant weight, and weigh W1 (g) with constant weight before corrosion.
3. Etching rate calculation rate=(W1-W2)104/2×8.933T(μm/min) In the formula: s-sample area (cm2) T-etching time (min)
4. Judgment: 1-2μm/min corrosion rate is appropriate. (1.5-5 minutes copper etching 270-540mg).
3. Glass cloth test method
In the process of hole metallization, activation and copper sinking are the key processes of electroless plating. Although the qualitative and quantitative analysis of ionic palladium and reducing solution can reflect the activation reduction performance, the reliability is not comparable to that of the glass cloth test. The copper sinking conditions of glass cloth are the most severe, and it can best show the performance of activation, reduction and copper sinking solution. The introduction is as follows:
1. Material: Desizing the glass cloth in 10% sodium hydroxide solution. And cut into 50 × 50 (mm), remove some glass filaments around the ends to spread the glass filaments.
2. Test steps:
2.1. Treat the sample according to the copper immersion process;
2.2. Put it in the copper sinking solution. After 10 seconds, the end of the glass cloth should be completely copper-sinking and turn black or dark brown. After 2 minutes, it will sink all the way up, and after 3 minutes, the copper color will deepen; for heavy copper sinking, 10 seconds The end of the rear glass cloth must be completely copper-sunk, and after 30-40 seconds, all the copper should be immersed;
2.3. Judgment: If the above copper sinking effect is achieved, it means that the activation, reduction and copper sinking performance is good, but the opposite is poor.
The above is the control method for improving the quality of copper sinking of PCB circuit boards that we have sorted out. I hope it will be helpful to you. If there is anything unclear, please contact the QQ, WeChat or phone on the right, and we will have professional personnel to help you. you answer.
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