Electroless copper plating (Electroless Plating Copper) is also commonly known as PTH. Printed circuit board hole metallization technology is one of the key circuit board manufacturing technology. Quality of Hole is strictly controlled in prerequisite to ensure high quality final product, and quality control plating copper layer is the key. Test method of controlling daily use are as follows:
(1) Electroless copper Rate Determination: Using electroless copper plating solution for copper deposition rate has certain technical requirements. If the process is too slow, it is possible to cause the hole wall voids or pinholes. In case plating copper rate is too fast, it will have a rough coating. To this end, the scientific determination of copper deposition rate is one of the method to control the quality of the copper sink. Chemical etching provide thin copper plating.
For example, copper deposition rate profile measuring method:
• Material: Epoxy substrate after etching copper with dimensions of 100 × 100 (mm).
(2) Measurement step:
1. The sample was at 120-140 ℃. Baked it for 1 hour and then weighed using an analytical balance W1 (g);
2. at 350-370 g/l of chromic anhydride and 208-228 ml/l sulfuric acid corrosion mixture (temperature 65 ℃) for 10 minutes, rinse with water;
3. In addition to chromium waste processing (temperature 30-40 ℃) 3-5 minutes, washed;
4. according to the provisions of prepreg process conditions, activation, and dope also processed;
5. Electrical circuit board Plated copper solution (temperature 25 ℃) PTH and a half hours to clean;
6. specimens at 120-140 ℃ bake 1 hour to a constant weight, weight W2
3. The copper deposition rate is calculated as: Rate = (W2-W1) 104 / 8.93 × 10 × 10 × 0.5 × 2 (μm)
4. Compared with the judgment: the measurement result data and process data provided by the comparison and judgment.
5. Etching solution etching rate determination
Through hole plating of copper micro-etching process is done by microscopic roughening, and plating copper layer to increase the binding force. To ensure the stability of the etching solution and the etching uniformity of the copper foil, the etching rate was measured to ensure that it remains within the range prescribed in the process.
1. Hydrogen peroxide in the sample (80-100 g/l) and sulfuric acid (160-210 g/l), 2 minutes at 30 ℃ etching, cleaning, cleaned with deionized water;
2. At 120-140 ℃ bake for 1 hour at constant weight load W2 (g), the sample before etching conditions also Click to constant weight weighing W1 (g).
3. calculate the etching rate rate = (W1-W2) 104/2 × 8.933T (μm / min) Where: s- sample area (cm2) T- etch time (min)
4. determine: 1-2μm / min corrosion rate is appropriate. (1.5-5 minute corrosion of copper 270-540mg).
5. Glass cloth Test Method
Electroless copper plating and activation is a key step in Hole metallization process. Despite the qualitative and quantitative analysis of palladium ions and also liquid may reflect activation restore performance, but not as glass cloth reliability test. Glass cloth copper deposition conditions in the most demanding and can display performance of activation, restore, and plating copper solution. It is outlined as follows:
(1) material: glass cloth desizing treatment in 10% sodium hydroxide solution then cut into 50 × 50 (mm). At the end of four weeks, remove some glass and make glass scattered.
(2) Experimental steps:
1. The specimens were copper process for processing;
2. plating copper into solution, and after 10 seconds, the glass cloth tip should have copper plating, black or dark brown. 30-40 seconds later, all the copper sink. 2 minutes after copper plated deepen. Three minutes later, it should be heavy plating.
3. Analyzing: If more than PTH effect, indicating activation, reduction and good performance copper sink, otherwise poor.